JP2000205808A - Displacement detecting device and lens barrel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a magnetic detecting element from slanting to a magnetic pattern. SOLUTION: A pressure spring 41 has a pivot 61 molded atop while bent almost in a V shape and this pivot 61 engages with a V-shaped groove 63 formed on a holder 45. The lower end of the pivot 61 is formed arcuately and the pivot 61 and V-shaped groove 63 are formed at right angles to an optical axis L, so the holder 45 swings in an assembled state around a swing center axis P nearly parallel to the rotating direction of a rotary cylinder 5. Consequently, a magnetoresistive(MR) element 47 comes into contact with a magnetic body layer 25 irrelevantly to whether the tip of the pressure spring 41 slants, and the gap between the entire surface of the MR element 47 and the magnetic body layer 25 is held at a prescribed value by a spacer film 49.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement detecting device for detecting a displacement of a movable member by magnetism and a lens barrel provided with the device.

[0002]

2. Description of the Related Art In recent years, in many mechanical devices, it is generally practiced to accurately detect the displacement and speed (time differential value of displacement) of a movable member as information for performing feedback control and the like. For example, in a lens barrel for an autofocus camera, a focus cam mechanism for converting a rotational driving force of an electric motor or the like into a linear driving force to move a focusing lens forward and backward is provided therein. -12
As described in JP-A-8566 and JP-A-7-324946, many have a displacement detecting device for detecting a rotational displacement of a rotary cylinder constituting a focus cam mechanism.

In this type of displacement detecting device, as shown in FIG. 6, for example, a magnetic member 21 such as a plastic magnet on which a magnetic pattern 30 is formed is adhered to the outer peripheral surface of the rotary cylinder 5. The rotational displacement of the magnetic pattern 30 (that is, the rotating cylinder 5) is detected by a magneto-resistive element (MR element) 47 disposed close to. At this time, in order to perform accurate detection, the surface of the magnetic member 21 and the MR element 4
The distance between the magnetic member 21 and the MR element 47 must be interposed between the magnetic member 21 and the MR element 47. The MR element 4 is formed by the pressure spring 41 as an elastic member.
A technique of pressing the magnetic member 7 against the magnetic member 21 has been put to practical use. In FIG. 6, a member denoted by reference numeral 3 is a fixed cylinder used for rotatably holding the rotary cylinder 5 and screwing the pressing spring 41. The member denoted by reference numeral 45 is the MR element 4
7 is a holder for fixing 7 to the pressure spring 41.

[0004]

Generally, in a displacement detecting device for a lens barrel, as described above, a leaf spring which is low in manufacturing cost and excellent in mass productivity is used as the pressure spring 41. There has been a problem that the parallelism between the magnetic member 21 and the MR element 47 is hindered. FIG. 7 is an enlarged side view of the pressure spring 41, the MR element 47, and the magnetic member 21. As shown in FIG. 7, the pressure spring 41 has a rectangular unloaded shape (indicated by a two-dot chain line). (Shown) is attached in a greatly bent state, thereby generating a pressing force for pressing the MR element 47 against the magnetic member 21. However, in this case, a slight inclination angle α is generated between the MR element 47 and the magnetic member 21 due to a minute shape error or mounting error of the pressure spring 41, an outer diameter error of the rotary cylinder 5, or the like. Element 47
(A tip in FIG. 7) is a predetermined amount δ from the magnetic member 21.
It may only be raised.

When such a phenomenon occurs, the magnetic member 2
The detection signal from the MR element 47, most of which departs from 1, becomes extremely weak, and an extremely undesirable situation arises in consideration of the subsequent signal processing. Although some attempts have been made to increase the distance (effective length) from the fixed end of the pressure spring 41 to the MR element 47 in order to suppress such inconveniences, a space for that purpose is required in the lens barrel. In addition to the difficulty in securing the angle, even when this method is employed, the inclination of the MR element 47 with respect to the magnetic member 21 cannot be completely eliminated. In FIG. 7, the inclination between the MR element 47 and the magnetic member 21 is exaggerated for easy understanding. In FIG. 7, a member denoted by reference numeral 49 is a spacer film that regulates a gap between the MR element 47 and the magnetic member 21. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a displacement detection device that prevents a tilt of a magnetic detection element with respect to a magnetic pattern, and a lens barrel including the device.

[0006]

According to a first aspect of the present invention, there is provided a displacement detecting device for detecting a displacement of a movable member held so as to be relatively displaceable with respect to a fixed member. A magnetic pattern formed on the movable member,
A magnetic detecting element elastically held by the fixed member and slidably contacting the magnetic pattern is provided, and the magnetic detecting element swings with a swing center substantially parallel to a displacement direction of the movable member. According to a second aspect of the present invention, there is provided the displacement detecting device according to the first aspect, wherein the movable member has a cylindrical shape, and the displacement of the movable member with respect to the fixed member is rotation. According to these inventions, for example, even if the support of the magnetic detection element with respect to the fixed member is performed by a leaf spring or the like, the magnetic detection element swings with the swing center substantially parallel to the displacement direction of the movable member, The magnetic detection element and the magnetic pattern come into close contact with each other with a space regulating member or the like interposed therebetween.

According to a third aspect of the present invention, there is provided a lens barrel having a displacement detecting device for detecting a displacement of a movable barrel held so as to be relatively displaceable with respect to a fixed member, wherein the lens barrel is formed on the movable barrel. A magnetic pattern, and a magnetic detection element elastically held by the fixed member and slidably in contact with the magnetic pattern, wherein the magnetic detection element swings with a swing center substantially parallel to a displacement direction of the movable cylinder. According to a fourth aspect of the present invention, there is provided the lens barrel according to the third aspect, wherein a displacement of the movable barrel with respect to the fixed member is a rotation. According to these inventions, for example, even if the support of the magnetic detection element with respect to the fixed member is performed by a leaf spring or the like, since the magnetic detection element swings with the swing center substantially parallel to the displacement direction of the rotary cylinder, The magnetic detecting element and the magnetic pattern are in close contact with each other with the space regulating member interposed therebetween, and the amount of rotation of the rotating cylinder (ie, the amount of movement of the focusing lens group) can be detected with high accuracy.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a main part of a lens barrel according to an embodiment of the present invention. As shown in FIG.
The lens barrel 1 includes a fixed barrel 3 that is bayonet-coupled to a camera body (not shown), a rotating barrel 5 that is rotatably fitted to the fixed barrel 3 to form a focus cam mechanism, and a sector gear of the rotating barrel 5. The rotating cylinder drive mechanism 13 including the reduction gear train 9 and the electric motor 11 meshing with the gear 7 is a main component. Reference numeral L in FIG. 1 denotes an optical axis which is a center of travel of light from a subject, and a rotating component such as the rotating cylinder 5 rotates around the optical axis L. Further, a member indicated by reference numeral 15 is a press ring that restricts the rotation of the rotary cylinder 5 in the axial direction. In FIG. 1, the reduction gear train 9 and the electric motor 11 are shown in an unfolded state for easy understanding, but the rotating cylinder driving mechanism 13 is arranged close to the outer periphery of the rotating cylinder 5 in an actual machine.

A belt-shaped magnetic member 21 is adhered to the outer peripheral surface of the rotary cylinder 5. As shown in FIG. 2, the magnetic member 21 is formed by coating a surface of a base film 23 made of a synthetic resin such as vinyl chloride with a magnetic layer 25 of barium ferrite or the like. The magnetic member 21
A round hole 27 into which the projection 26 of the rotary cylinder 5 is fitted is formed on one end side, and the side end is locked in the linear groove 28 of the rotary cylinder 5 so that the rotary cylinder 5 can be moved in the axial direction and the rotational direction. It is positioned with high precision. The magnetic layer 2
As shown in FIG. 3 (a view in the direction of arrow A in FIG. 2), S poles and N poles are alternately magnetized in the rotation direction of the rotary cylinder 5, thereby forming the magnetic pattern 30. Is formed. In the drawing, the member indicated by reference numeral 31 is an adhesive applied to the back surface of the base film 23, but a double-sided adhesive tape or the like may be employed instead.

On the other hand, a pressure spring 141 made of a spring steel plate is fixed to the fixed cylinder 3 with a screw 43, and an MR element 47 is attached to the tip of the pressure spring 141 via a synthetic resin holder 45. Is held. Pressure spring 141
Represents the degree of bending θ in the no-load shape as shown in FIG.
In the mounting state shown in FIG. 2, the MR element 47 is largely bent and deformed and presses the MR element 47 against the magnetic member 21 with a predetermined pressing force F. In the figure, reference numeral 4
The member indicated by No. 9 is a spacer film made of PTFE or the like having a low coefficient of friction and excellent wear resistance.
It is fixed to the lower surface of the R element 47. The member denoted by reference numeral 51 is a flexible printed circuit board interposed between the holder 45 and the MR element 47, which is connected to an electric terminal (not shown) to supply a current from the camera body side or to supply the MR element 47. To output a detection signal to the signal processing circuit. The member denoted by reference numeral 53 is
This is a washer provided to prevent the holder 45 from dropping out of the holder 1.

In the case of the present embodiment, as shown in the exploded perspective view of FIG. 5, the pressure spring 141 has a pivot 61 which is bent and formed in a substantially V-shape at the tip thereof. It engages with a V-shaped groove 63 formed in the holder 45.
Since the lower end portion of the pivot 61 is formed in an arc shape, and the pivot portion 61 and the V-shaped groove 63 are formed so as to be orthogonal to the optical axis L in plan view (FIG. 3), FIGS.
In the assembled state shown in (1), the holder 45 has the swing center axis P substantially parallel to the rotation direction of the rotary cylinder 5 and the pressure spring 4
Swing with respect to 1.

A substantially rectangular through hole 65 is formed in the pressure spring 141 so as to be orthogonal to the pivot 61, and a substantially rectangular shank 67 projecting from the upper surface of the holder 45 is formed in the through hole 65. Insert. Therefore, the through hole 6
5, the outer surface of the shank 67 is locked to the inner surface of the shank 6 with respect to the pressing spring 141 of the holder 45.
Turning around the axis 7 is prevented. In FIG. 5, reference numeral 69 denotes a locking pin protruding from the upper surface of the shank 67.
After the holder 45 and the washer 53 are assembled to the pressurizing spring 141, the locking pin 69 is deformed by a method such as heat melting to fix the washer 53 to the holder 45.

The operation of this embodiment will be described below. When assembling the lens barrel 1, the assembler attaches the rotating cylinder 5 to the fixed cylinder 3, and then mounts the pressing spring 141 to which the holder 45 and the MR element 47 are assembled to the fixed cylinder 3 with screws 43. . Then, the MR element 47 abuts on the magnetic layer 25 of the magnetic member 21 via the spacer film 49, and the pressing spring 141 is largely bent to push the MR element 47 on the magnetic layer 25 via the holder 45. And press. At this time, the tip of the pressure spring 141 is greatly inclined,
The inclination angle is determined by a minute shape error and a mounting error of the pressure spring 141, an outer diameter error of the rotary cylinder 5, and the like, and when mass production is performed, the uniformity cannot be obtained.

However, in the present embodiment, the pressure spring 14
Since the holder 45 swings about the swing center axis P with respect to 1, the MR element 47 comes into close contact with the magnetic layer 25 regardless of the inclination of the tip of the pressure spring 141. As a result, the gap between the entire surface of the MR element 47 and the magnetic layer 25 is maintained at a specified value by the spacer film 49, so that a strong detection signal from the MR element 47 can be obtained. Signal processing in the processing circuit is performed smoothly.

The description of the specific embodiment has been completed.
Aspects of the present invention are not limited to this embodiment.
For example, in the above-described embodiment, the rotation amount of the rotary barrel in the lens barrel is detected. However, the embodiment may be applied to a device that detects a linear movement amount, or the displacement of the movable member in another device may be detected. You may apply to the displacement detection apparatus which detects. In the above embodiment, the magnetic sensing element is caused to swing with the swing center formed by the pivot formed in the pressure spring and the V-shaped groove formed in the holder. Various forms, such as one that swings with the swing center inserted, can be used. Further, in the above-described embodiment, a pressure spring made of a spring steel plate is used as the elastic member for pressing the magnetic detection element against the magnetic pattern.
A coil spring, synthetic rubber, or the like may be used. Furthermore, the specific configuration and the like of the lens barrel are not limited to the examples in the above embodiment, but can be appropriately changed according to design convenience and the like.

[0016]

According to the present invention, there is provided a displacement detecting device for detecting a displacement of a movable member held so as to be relatively displaceable with respect to a fixed member, wherein the magnetic pattern formed on the movable member is fixed to the fixed member. A magnetic detection element elastically held by a member and slidingly contacting the magnetic pattern, and the magnetic detection element swings with a swing center substantially parallel to a displacement direction of the movable member. Even if the magnetic detection element is supported on the member by a leaf spring or the like, the magnetic detection element swings with the swing center substantially parallel to the direction of displacement of the movable member, so that the cost and cost of the lens barrel and the like can be reduced. The magnetic detection element and the magnetic pattern come into close contact with each other with a space regulating member or the like interposed therebetween while increasing the space, so that a strong detection signal can be obtained from the magnetic detection element.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a lens barrel according to an embodiment of the present invention.

FIG. 2 is an enlarged side view showing a main part of the embodiment.

FIG. 3 is a view taken in the direction of arrow A in FIG. 2;

FIG. 4 is a side view showing a state before mounting a pressure spring and the like in the embodiment.

FIG. 5 is an exploded perspective view of a pressure spring and a holder according to the embodiment.

FIG. 6 is a perspective view showing a conventional lens barrel.

FIG. 7 is an enlarged side view showing a main part of the lens barrel.

[Explanation of symbols]

 Reference Signs List 1 lens barrel 3 fixed cylinder 5 rotating cylinder 13 rotating cylinder driving mechanism 21 magnetic member 25 magnetic layer 41, 141 pressure spring 45 holder 47 MR Element 49 Spacer film 51 Flexible printed board 61 Pivot 63 V-shaped groove 65 Through hole 67 Shank L Optical axis

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 7/08 G02B 7/04 A

Claims (4)

[Claims] 1. A displacement detecting device for detecting a displacement of a movable member held so as to be relatively displaceable with respect to a fixed member, comprising: a magnetic pattern formed on the movable member; A displacement detection device comprising: a magnetic detection element that slides on the magnetic pattern; and wherein the magnetic detection element swings around a swing center substantially parallel to a displacement direction of the movable member. 2. The displacement detecting device according to claim 1, wherein the movable member has a cylindrical shape, and a displacement of the movable member with respect to the fixed member is a rotation. 3. A lens barrel having a displacement detecting device for detecting a displacement of a movable barrel held so as to be relatively displaceable with respect to a fixed member, wherein: a magnetic pattern formed on the movable barrel; And a magnetic detecting element which is elastically held on the magnetic pattern and slidably contacts the magnetic pattern, and wherein the magnetic detecting element swings around a swing center substantially parallel to a displacement direction of the movable barrel. . 4. The lens barrel according to claim 3, wherein the displacement of the movable barrel with respect to the fixed member is a rotation.