JPH06102056A - Optical rotation displacement detector - Google Patents

Abstract

PURPOSE:To prevent flexural deformation while stabilizing detection output by reinforcing a rotary disc provided with a spiral slit. CONSTITUTION:The optical rotational displacement detector comprises a disc 1 rotary displaces around a rotary shaft 2, and a light source 5 and a light receiving element 7 disposed oppositely on the opposite sides thereof. A spiral slit 3 is made in the surface of the disc 1 along the peripheral direction thereof. The light source 5 projects light onto the disc 1. The light receiving element 7 has an elongated light receiving face 8 arranged in the radial direction of the disc 1. The light receiving face 8 receives light 9 transmitted through the slit 3 which moves in radial direction as the disc 1 rotates and produces a rotational displacement detection signal. Seams 4 are provided obliquely along the spiral direction of the slit 3 in order to reinforce the disc 1. Furthermore, effective opening of the slit 3 in radial direction is set constant along the spiral direction except the oblique seam parts 4 in order to stabilize detection output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission type rotational displacement detecting device. More specifically, the present invention relates to a reinforcing structure of a rotating disk having slits formed in a spiral shape.

[0002]

2. Description of the Related Art Conventionally, various types of optical rotational displacement detecting devices are known. For example, JP-A-60-2250
Japanese Unexamined Patent Publication No. 24 discloses a structure using a rotating disk having spiral slits. As shown in FIG. 5, in the optical rotational displacement detection device having this structure, a disc 102 is attached so as to be rotatable around a rotation shaft 101.
The disk 102 is made of a light-shielding material such as a metal plate, and has a spiral slit 103 on its surface along the circumferential direction from the center of rotation.
Are formed by etching. A light source 104 is fixedly arranged to face the disk 102 and to illuminate incident light above the disk 102. The light sources 104 are arranged so as to cover the radial region of the disc 102. Also, the disc 102
The light receiving element 105 is provided below the light source 104 at a position facing the light source 104.
Is fixedly placed. The light receiving element 105 is provided with a light receiving surface 106 having a longitudinal shape arranged along the radial direction of the disk 102, and receives the transmitted light from the slit width portion that moves in the radial direction with the rotational displacement of the rotary disk 102. Then, the rotational displacement detection signal is output.

FIG. 6 shows the relationship between the rotation angle of the disc 102 and the detection signal. With the rotation of the disk, the light transmitted through the spiral slit width portion moves along the longitudinal light receiving surface.
The light receiving element outputs a detection signal according to the light receiving position of the transmitted light. Therefore, the rotation angle and the detection signal have a linear relationship.

[0004]

The problem to be solved by the invention will be briefly described with reference to FIG. 5 again. The detection angle range is expanded as the length of the spiral slit is extended. That is, the detection angle range is proportional to the draft angle of the spiral. However, the larger the draft angle, the smaller the area connecting the respective parts of the disc separated on both sides of the slit, and the lower the mechanical strength. For this reason, there is a problem that a disk made of a metal plate or the like is flexibly deformed during the rotational displacement and a detection error occurs.

As a countermeasure against this, a structure in which a disk made of a metal plate is lined with a transparent resin plate and reinforced is considered. However, this laminated structure or laminated structure has a drawback that the manufacturing cost is increased and the weight and thickness of the rotary displacement member are increased. Alternatively, a structure is conceivable in which a metal light-shielding material such as aluminum is vacuum-deposited on the surface of a disk made of a transparent glass material or the like through a mask to form a spiral slit. However, the use of vacuum vapor deposition also raises the manufacturing cost as compared with the etching process of a metal plate, and has the drawbacks of low long-term reliability.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, it is an object of the present invention to provide a reinforcing structure to the rotating disk itself which is composed of a single thin metal plate. The following measures have been taken in order to achieve this object. That is, the optical rotational displacement detection device according to the present invention includes a moving member and a fixed light source and a fixed light receiving element arranged on both sides of the moving member as a basic constituent element. The moving member is composed of a disk which is rotationally displaced, and spiral slits are formed by etching along the circumferential direction of the surface. The fixed light source irradiates the moving member with incident light so as to cover its radial region. The light receiving element has a long-shaped light receiving surface arranged along the radial direction of the disk, receives the transmitted light from the slit width part that moves in the radial direction along with the rotational displacement, and detects the rotational displacement detection signal. Output. In such a structure, a means for mechanically reinforcing the moving member is provided by inserting a seam obliquely along the spiral direction of the slit. Further, a measure is taken so that the radial effective opening size of the slit width portion excluding the joint portion is always the same along the spiral direction, and the received amount of slit transmitted light is constant. Preferably,
The seam is symmetrically patterned with respect to the spiral center line of the slit width portion.

[0007]

In the present invention, the areas of the disk defined by the spiral slit are not separated but are connected to each other by the seam. Therefore, the flexural deformation of the disk can be suppressed, and the draft angle of the spiral can be made larger than in the conventional case, so that the rotation detection angle range can be expanded. The seam is oblique along the spiral direction of the slit, and the radial effective opening dimension of the slit width portion excluding the seam portion is patterned so as to be always the same along the displacement direction.
Therefore, the amount of light received through the slit width portion is always constant regardless of the position of the moving member that is rotationally displaced. Therefore, the amount of received light does not change during the continuous rotational displacement, and a stable detection output can be obtained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic perspective view showing a configuration of an optical rotational displacement detection device according to the present invention. A disk 1 made of a light-shielding material such as a metal plate is fixed to a rotary shaft 2 and can be rotationally displaced. The rotary shaft 2 is connected to a detection target (not shown). The surface of the disk 1 is formed with a spiral slit 3 that gradually expands from the center along the circumferential direction. A seam 4 obliquely extending along the spiral direction of the slit 3 is formed to mechanically reinforce the disc 1. In order to make the width 3 effective opening of the slit 3 large, the joint 4
It is preferable to make the width of the as narrow as possible. The seam 4 and the slit 3 can be simultaneously formed by etching, for example.

A light source 5 made of, for example, an LED is fixedly arranged above the disk 1. The light source 5 irradiates the surface of the disk 1 with substantially parallel light through a light projecting lens 6 fixed to the surface thereof. On the other hand, below the disk 1, a light receiving element 7 is fixedly arranged in alignment with the light source 5. The light-receiving surface 8 provided on the surface has a longitudinal shape along the radial direction of the disk 1. Along with the rotational displacement of the disk 1, the transmitted light 9 from the width of the spiral slit 3 moves in the radial direction and is received by the light receiving surface 8. The light receiving element 7 is formed of a light receiving position detecting element such as PSD, and outputs the differential signals A and B to a pair of output terminals. That is, the output signals A and B are differentially changed according to the light receiving position of the transmitted light 9. The differential signal is subjected to a predetermined arithmetic processing (AB) / (A + B) by the arithmetic circuit 10 and outputs a detection signal representing the rotational displacement of the disk 1.

FIG. 2 shows an enlarged partial shape of the slit 3.
The seams 4 are arranged at predetermined intervals along the spiral direction of the slit 3. Each seam 4 has a substantially V-shape, and is oblique along the spiral direction. Also, slit 3
The V-shaped seam 4 is symmetrically patterned with respect to the spiral center line 11. As a feature of the present invention,
The effective opening size in the radial direction of the width portion of the slit 3 excluding the seam 4 is designed to be always the same along the spiral direction. For example, focusing on the existing radial direction R1,
The effective opening size of the slit width portion is given by a + b + c excluding the seam 4. Focusing on the other radial direction R2, the effective opening size of the slit width portion is given by d + e excluding the seam 4. According to this invention, (a
+ B + c) and (d + e) are equal.

As an example, the radial directions R1 and R2 have been described, but the effective opening size of the slit width portion is always designed to be the same in all radial directions. Therefore,
The light receiving surface of the light receiving element fixed along the radial direction is a disk 1
During the rotational displacement of, a constant amount of transmitted light is continuously received from the slit width portion. Therefore, the barycentric position of the light-receiving spot projected on the slit width portion changes continuously and linearly along the light-receiving surface, and excellent linearity can be obtained. In addition, the line width of the seam 4 is set to the minimum size required for mechanical reinforcement, and the loss of the amount of transmitted light blocked by this is extremely small. Therefore, it is possible to maintain the detection output accuracy that is substantially the same as the conventional one.

FIG. 3 is a schematic partial enlarged view showing another embodiment of the joint shape according to the present invention. It has a shape basically similar to that of the embodiment shown in FIG. 2, and corresponding parts are given corresponding reference numerals to facilitate understanding.
The difference from the embodiment shown in FIG. 2 is that each seam 4 is V
It means that the pattern is not in a letter shape but in an X shape. Compared to V joints, X joints can provide a more mechanically balanced reinforcement structure. Also in this example, the effective opening sizes of the width portions of the slit 3 are set to be equal in all radial directions. For example, the effective aperture dimension in the radial direction R1 is given by a + b, and
The effective aperture dimension of 2 is given by c + d + e, and the radial direction R
The effective aperture size of 3 is given by f, but they are all equal. That is, from the radial width of the slit 3 to the joint 2
The line width for this line is subtracted.

FIG. 4 shows a comparative example of seam patterns for reference. For easy understanding, parts corresponding to those of the embodiment of the present invention shown in FIG. 2 are designated by corresponding reference numerals. In this comparative example, the seams 4 are regularly provided at a predetermined pitch P along the spiral direction of the slit 3. The array pitch P is set so as to match the lateral dimension W of the light receiving surface 8. As is clear from the figure, the seam 4
By setting the arrangement pitch P of the same as the lateral dimension W of the light receiving surface 8, the effective projection areas of the width portions of the slits 3 with respect to the light receiving surface 8 become equal regardless of the position of the rotating disk 1, and the light receiving amount can be made constant. . However, unlike the present invention,
The effective opening size in the radial direction of the width portion of the slit 3 changes periodically. Therefore, on average, the amount of received light is always constant, but fluctuations actually occur, and subtle fluctuations appear in the detection output. Therefore, the detection accuracy is lower than that of the present invention.

[0014]

As described above, according to the present invention, the disc is mechanically reinforced and deflected by forming a joint in the spiral slit formed by etching in the rotary disc made of a thin metal plate or the like. The effect is that it can be suppressed. or,
In addition to skewing the seam along the spiral direction of the slit, the radial effective opening size of the slit width part excluding the seam is always the same along the spiral direction to remove subtle fluctuations and detect the light receiving element. This has the effect of stabilizing the output.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing the structure of an optical rotational displacement detection device according to the present invention.

FIG. 2 is an enlarged partial plan view showing a shape of a joint which is a characteristic element of the present invention.

FIG. 3 is an enlarged partial plan view showing another example of the shape of the seam.

FIG. 4 is an enlarged partial plan view showing a reference example of a joint shape.

FIG. 5 is a perspective view showing a conventional optical rotational displacement detection device.

FIG. 6 is a graph showing a relationship between a rotation angle and a detection signal of a conventional optical rotary displacement detection device.

[Explanation of symbols]

 1 disk 2 rotating shaft 3 slit 4 seam 5 light source 7 light receiving element 8 light receiving surface 9 transmitted light 10 arithmetic circuit

Claims (2)

[Claims] 1. A moving member, which is composed of a disc that is rotationally displaced, and has a spiral slit formed along the circumferential direction of the surface thereof,
A fixed light source for irradiating the moving member with incident light and a longitudinal light receiving surface arranged along the radial direction of the disk are provided to receive transmitted light from a slit width portion that moves in the radial direction with rotational displacement. In an optical rotational displacement detection device consisting of a fixed light receiving element that outputs a rotational displacement detection signal, a movable member is reinforced by adding a seam obliquely along the spiral direction of the slit, and the slit width part excluding the seam part. An optical rotary displacement detection device characterized in that the effective aperture size in the radial direction is always made equal along the spiral direction so that the amount of received slit transmitted light is constant. 2. The optical rotational displacement detection device according to claim 1, wherein the seam is symmetrically patterned with respect to a center line of the slit width portion in the spiral direction.