JP2003240603A - Displacement detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a displacement detection device capable of performing stably accurate position detection without causing a signal defect even when an external force works on a flexible printed wiring board after position adjustment. <P>SOLUTION: In an MR encoder capable of adjusting the rotational position of a magnetic head 1 by rotating the magnetic head 1 in the supported state, and having a pressure spring 4 for supporting the magnetic head 1, while pressurizing it to a magnetic tape, an FPC 2 connected to the magnetic head 1 is interfitted into a rotation shaft 7 coaxially with a rotation center hole 4a for rotational position adjustment provided on the pressure spring, thereby to regulate the position of the FPC 2. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement detection device such as a magnetic encoder that magnetically detects displacement of a movable member.

[0002]

2. Description of the Related Art In recent years, in many mechanical devices, the displacement and speed of a movable member are accurately detected 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 and moving a focusing lens forward and backward is provided inside. In a lens barrel having such an autofocus mechanism or a zoom mechanism, for example, Japanese Patent Laid-Open No. 2000-
As described in Japanese Patent No. 205808, there is one equipped with a displacement detection device composed of a magnetic encoder in order to detect the moving position of the moving optical system when the lens is driven. The detection capability of these displacement detection devices is improving day by day, and adjustment of the mounting error of the displacement detection device requires extremely high precision adjustment. Therefore, conventionally, when assembling the displacement detection device, the inclination of the detection element (magnetic head) with respect to the movable member (magnetic scale) is adjusted as the adjustment of the displacement detection device.

[0003]

However, in the above-mentioned conventional device, when some force acts on the flexible printed wiring board (hereinafter, referred to as FPC) fixed to the magnetic head after the position adjustment, the magnetic head is moved. There is a case where the spring member that pressurizes the magnetic scale is bent and a slight deviation occurs in the adjustment position of the magnetic head. In such a case, there is a problem that the detection signal from the magnetic head becomes extremely weak, a detection error becomes large, and a signal defect such as a missed detection occurs. Further, since the detection signal is weak and unstable, there are many inconveniences in subsequent signal processing.

An object of the present invention is to provide a displacement detecting device capable of performing stable and accurate position detection without causing a signal defect even when an external force acts on the flexible printed wiring board after position adjustment. It is to be.

[0005]

The present invention solves the above-mentioned problems by the following means for solving the problems. It should be noted that, for ease of understanding, reference numerals corresponding to the embodiments of the present invention will be given and described, but the present invention is not limited thereto. That is, the invention of claim 1 is a displacement detecting device for detecting a displacement of a movable member (6) provided so as to be relatively displaceable with respect to a fixed member (8), and is integrated with the movable member. A scale (3) displaceably provided, a displacement detector (1) that directly or indirectly contacts the scale and detects displacement of the scale, and a member that supports the displacement detector. The rotation position of the displacement detection unit can be adjusted by rotating the displacement detection unit with respect to the fixed member, and the displacement detection unit is supported while being pressed against the scale. A pressure support member (4),
A wiring member (2) which is connected to the displacement detection unit and whose position is regulated in the vicinity of the rotation center of the rotation position adjustment;
It is a displacement detection device provided with.

According to a second aspect of the present invention, in the displacement detecting device according to the first aspect, the pressure supporting member (4) is fitted to the central shaft (7) provided on the fixing member (8). The wiring member (2) has a fitting hole (4a), and the rotational position of the wiring member (2) can be adjusted together with the displacement detection unit around the fitting hole.
Is a displacement detecting device having a position regulating hole (2a), the position of which is regulated by fitting the position regulating hole to the central shaft.

The invention of claim 3 relates to claim 1 or claim 2.
In the displacement detection device described in [1], the scale (3)
Is a magnetic scale in which magnetisms of different polarities are alternately arranged along the movement direction, and the displacement detection unit (1) includes a magnetoresistive element for detecting the magnetism of the magnetic scale. It is a displacement detection device.

The invention of claim 4 is from claim 1 to claim 3.
The displacement detecting device according to any one of items 1 to 7, wherein the position where the wiring member (2) is taken out of the displacement detecting section (1) is provided on a side close to the rotation center. It is a displacement detection device.

The invention of claim 5 is from claim 1 to claim 4.
In the displacement detection device according to any one of items 1 to 4, the position where the displacement detection unit (1) is supported by the pressure support member (4) is provided on the side close to the rotation center. Is a displacement detecting device.

According to a sixth aspect of the present invention, in the displacement detecting device according to any one of the first to fifth aspects, the wiring member (2) is a flexible printed wiring board. It is a displacement detection device.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in more detail below with reference to the drawings. Figure 1
FIG. 6 is a cross-sectional view of a lens barrel using an embodiment of the displacement detection device according to the present invention. The lens barrel in the present embodiment is an autofocus lens barrel for a single-lens reflex camera that is used by being attached to a camera body (not shown). The moving lens group 5 is a part of the taking lens, and is a lens group that moves in a direction along the optical axis L (hereinafter, referred to as an optical axis direction) when performing a focusing operation. The cam ring 6 is a moving lens group 5
Is a cylindrical movable member that rotates around a fixed cylinder (fixed member) 8 when the is moved, and has a cam groove 6a formed therein. The cam ring 6 is rotated by the rotational force of the actuator transmitted from the connecting member, with the engaging portion 6b engaging with the connecting member (not shown). Therefore, when the cam ring 6 rotates, the movable lens group 5 moves in the optical axis direction.

An MR encoder is provided for detecting the amount of rotation (displacement) of the cam ring 6 and transmitting it to a controller (not shown). The MR encoder in this embodiment includes a magnetic tape 3, a magnetic head 1, a pressure spring 4, a flexible printed wiring board (hereinafter, FPC) 2, and a rotary shaft 7.

The magnetic tape 3 is a magnetic scale attached to the cam ring 6 along the rotational direction of the cam ring 6, rotates together with the rotation of the cam ring 6, and has magnetic properties of different polarities. Are alternately arranged along the rotation direction.

FIG. 2 is a perspective view for explaining the MR encoder in this embodiment. 2A shows a state before the position of the FPC 2 is restricted, FIG. 2B shows a state in which the rotary shaft 7 is removed, and FIG. 2C shows a state in which the rotary shaft 7 is attached. It shows the state. In addition, FIG.
FIG. 2B is a diagram shown for explanation, and the state of FIG. 2C shows the embodiment of the present invention.

The magnetic head 1 is a displacement detector fixed to the pressure spring 4, has a magnetoresistive element for detecting the magnetism of the magnetic tape 3, and the magnetic tape 3 is pressed by the pressure spring 4. It is pressed. Therefore, when the cam ring 6 rotates, the magnetic tape 3 rotates while sliding on the magnetic head 1, and the rotation amount of the cam ring 6 can be detected.
A position where the magnetic head 1 is supported by a pressure spring 4 described later,
Further, the positions where the FPC 2 described later is taken out from the magnetic head 1 are both on the side close to the rotation shaft 7 described later (camera body side).

The pressure spring 4 is a pressure support member in which the magnetic head 1 is fixed to the magnetic head mounting portion 44 and fixed to the fixed cylinder 8 by a screw (not shown) through the fixing hole 4c. The pressure spring 4 includes a first arm portion 41, a connection portion 42, and a second portion between the fixing hole 4c and the magnetic head mounting portion 44.
Has an arm portion 43.

The first arm portion 41 extends from the fixing hole 4c to the optical axis L.
It is provided at two locations in parallel so as to project in a direction substantially along with, and is bent with the fixed hole 4c side as a fulcrum. The connecting portion 42 includes a tip portion of the first arm portion 41 and a second arm portion.
This is a part for connecting the arm part 43 of the. Second arm 43
Are provided in parallel between the connecting portion 42 and the magnetic head mounting portion 44 in the direction substantially along the optical axis L, and when viewed from the fixed cylinder 8 as a reference, the connecting portion 42 side bends. It is like this. The magnetic head attachment portion 44 is a portion for fixing the magnetic head 1 at the end of the magnetic head 1 on the camera body side.

By forming the bending arm as the spring of the pressure spring 4 in such a manner as to be folded back, the spring constant can be reduced even with a small pressure spring, and the magnetic head 1 can be uniformly applied. It can be pressurized with pressure. Further, when the cam ring 6 rotates with respect to the fixed barrel 8, the position of the magnetic tape 3 moves so as to undulate due to the influence of component accuracy and the like. However, the pressure spring 4 is formed as described above. As a result, the movement of the magnetic tape can be followed without the magnetic head 1 tilting, and the magnetic head 3 can always be in close contact with the magnetic tape 3.

The pressure spring 4 has a rotation center hole 4a,
An adjustment long hole 4b is provided. The rotation center hole 4a is
It is a fitting hole that fits into the rotary shaft 7 together with an FPC 2 described later. The adjustment long hole 4b is a hole through which an adjustment eccentric pin (not shown) can pass. When adjusting the position of the magnetic head 1 with respect to the magnetic tape 3, the adjusting eccentric pin is inserted into a hole (not shown) provided in the fixed barrel 8 through the adjusting elongated hole 4b to adjust the eccentric pin. By rotating the pressure spring 4, the pressure spring 4 rotates around the rotation center hole 4a, and delicate adjustment can be easily performed.

The FPC 2 is a wiring member fixed to the magnetic head 1 for transmitting a signal obtained from the magnetic head 1 to a processing circuit. The FPC 2 is provided with a position regulating hole 2a, which is sized to overlap the rotation center hole 4a provided in the pressure spring 4 for adjusting the angle of the magnetic head 1, and penetrates the rotation shaft 7. The position of FPC2 is regulated.

The rotary shaft 7 is a central shaft screwed into the fixed cylinder 8, and the position regulating hole 2a of the FPC 2 and the rotational center hole 4a of the pressure spring 4 are fitted to this shaft.

According to the present embodiment, the position of the FPC 2 is regulated by the position regulating hole 2a, so that even if an external force acts on the FPC 2 after the position of the magnetic head 1 is adjusted, the pressure spring 4 is not applied. There is no warp, a signal defect does not occur, and stable and accurate position detection can be performed. Therefore, since the position of the magnetic head 1 is displaced after the adjustment, the readjustment is not required, and the handling is facilitated, the workability during assembly can be improved.

Further, not only at the time of assembling, but after being incorporated in the product, the hardness of the FPC changes due to temperature changes,
Even if warpage (deformation) occurs, accurate position detection can be performed.

Further, in implementing the present invention, since no newly required parts are generated, even a low-cost displacement detecting device can stably and accurately detect the position.
Furthermore, since the position regulation hole 2a is provided at the same position as the rotation center hole 4a of the pressure spring 4, even the small displacement detection device can regulate the position of the FPC 2.

(Modifications) The present invention is not limited to the above-described embodiments, but various modifications and changes can be made, which are also within the scope of the present invention. For example, in the present embodiment, an example in which the position regulating hole 2a has the same size as the rotation center hole 4a of the pressure spring 4 is shown, but the present invention is not limited to this, and the size may be different, for example. It does not need to be fitted to the same rotating shaft.

Further, in this embodiment, the rotary shaft 7 is
Although the example in which the fixed barrel 8 is formed as a separate component is shown, the invention is not limited to this, and the fixed barrel 8 may be integrally formed as a part of the fixed barrel 8.

Further, in the present embodiment, an example of the MR encoder has been described, but the present invention is not limited to this, and an optical sensor or the like which requires other precise position accuracy may be used.

[0028]

As described in detail above, according to the present invention, the following effects can be obtained. (1) Since the wiring member that is connected to the displacement detection unit and whose position is regulated in the vicinity of the rotation center of the rotational position adjustment is provided, even if an external force is applied to the wiring member, the external force is not transmitted to the displacement detection unit. Stable and accurate position detection can be performed.

(2) Since the position of the wiring member is regulated by fitting the position regulating hole to the central axis, the position of the wiring member can be regulated even if the position detecting device is small, and the wiring member is stable. Therefore, accurate position detection can be performed.

(3) The scale is a magnetic scale in which magnetisms of different polarities are alternately arranged along the moving direction,
Since the displacement detection unit includes a magnetoresistive element that detects the magnetism of the magnetic scale, even a magnetic encoder that requires high-accuracy mounting accuracy can perform stable and accurate position detection.

(4) Since the position at which the wiring member is taken out and the position supported by the pressure supporting member in the displacement detecting section are provided on the side close to the center of rotation, even if the position detecting device is small, it is stable. Therefore, accurate position detection can be performed.

(5) Since the wiring member is a flexible printed wiring board, even a position detecting device having a simple structure and a low cost can stably and accurately detect the position.

[Brief description of drawings]

FIG. 1 is a sectional view of a lens barrel using an embodiment of a displacement detection device according to the present invention.

FIG. 2 is a perspective view illustrating an MR encoder according to this embodiment.

[Explanation of symbols]

1 magnetic head 2 Flexible printed wiring board (FPC) 3 magnetic tape 4 pressure spring 5 Moving lens group 6 cam ring 7 rotation axis 8 fixed cylinder

Claims (6)

[Claims] 1. A displacement detecting device for detecting a displacement of a movable member provided so as to be relatively displaceable with respect to a fixed member, the scale being provided so as to be displaceable integrally with the movable member, A displacement detection unit that directly or indirectly contacts the scale and detects displacement of the scale, and a member that supports the displacement detection unit, in a state in which the displacement detection unit is supported with respect to the fixed member. By rotating, it is possible to adjust the rotational position of the displacement detector,
A pressure support member that supports the displacement detection unit while applying pressure to the scale; and a wiring member that is connected to the displacement detection unit and that is positionally regulated in the vicinity of the rotation center of the rotational position adjustment. Displacement detection device. 2. The displacement detection device according to claim 1, wherein the pressure support member has a fitting hole that fits into a central shaft provided in the fixing member, and the fitting hole is centered around the fitting hole. Rotational position can be adjusted together with the displacement detection unit, the wiring member has a position regulating hole, the position regulating hole is regulated by fitting the central axis,
Displacement detection device characterized by. 3. The displacement detection device according to claim 1, wherein the scale is a magnetic scale in which magnetisms of different polarities are alternately arranged along a movement direction, and the displacement detection unit includes: A displacement detecting device comprising a magnetoresistive element for detecting the magnetism of the magnetic scale. 4. Any one of claims 1 to 3
The displacement detection device according to the item 1, wherein the position at which the wiring member is taken out of the displacement detection unit is provided on a side closer to the rotation center. 5. Any one of claims 1 to 4
The displacement detection device according to item 4, wherein the position where the displacement detection unit is supported by the pressure support member is provided on a side close to the center of rotation. 6. The displacement detecting device according to claim 1, wherein the wiring member is a flexible printed wiring board.