JP2972480B2 - Optical rotation position detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical rotary type position detecting device. More specifically, the present invention relates to a structure for reinforcing a rotating disk having a spiral slit. For more information,
The present invention relates to an optical correction structure associated with a reinforcing structure.

[0002]

2. Description of the Related Art Various types of optical rotational position detecting devices are conventionally known. For example, Japanese Patent Application Laid-Open No. 60-1401
No. 17, JP-A-60-225024, and the like disclose a structure using a rotary disk having a spiral slit. As shown in FIG. 9, in the optical rotation position detecting device having this structure, a disk 102 is attached so as to be rotatable about a rotation shaft 101. The disk 102 is made of a light-shielding material such as metal, and has a spiral slit 103 formed on the surface thereof along the circumferential direction from the center of rotation. Light source 1 for irradiating incident light facing disk 102
04 is fixedly arranged. Further, a light receiving element 105 is fixedly arranged at a position facing the light source 104 via the disk 102. The light receiving element 105 has a long light receiving surface 106 arranged along the radial direction of the disk 102, and receives transmitted light from a slit that moves in the radial direction along with the rotation direction of the disk 102, and rotates the light. Outputs a position detection signal.

FIG. 10 shows the relationship between the rotation angle of the disk 102 and the detection signal. With the rotation of the disk, the light transmitted through the spiral slit moves along the light receiving surface having a long shape. The light receiving element outputs a detection signal according to the light receiving position of the transmitted light. For example, when a PSD or the like is used as a light receiving element, a detection signal corresponding to the position of the center of gravity of transmitted light on the light receiving surface is output. If no error factor is included, the rotation angle and the detection signal have a linear relationship.

[0004]

Referring back to FIG. 9, the problem to be solved by the invention will be briefly described. As the length of the spiral slit increases, the detection angle range increases. That is, the detection angle range is proportional to the helix angle. However, as the draft angle is increased, the area for connecting the portions of the disk separated on both sides in the width direction of the slit is reduced, and the mechanical strength is reduced. For this reason, there is a problem that a thin disk made of metal or the like bends and deforms during rotational displacement, and a detection error occurs. As a countermeasure, a structure in which a disk made of a thin metal plate is backed with a transparent resin plate or a glass plate and reinforced is considered. However, this laminate structure has the drawbacks that it increases the manufacturing cost and increases the weight and thickness of the rotationally displaced portion. Alternatively, a method of forming a spiral slit pattern by vacuum-depositing a light-shielding material such as metal on the surface of a disk made of a transparent glass plate via a mask may be considered. However, even with this method, there is a disadvantage that the manufacturing cost is several times higher than the etching processing of the thin metal plate.

[0005] In view of the above-mentioned problems of the prior art, it is a basic object of the present invention to provide a reinforcing structure to a rotating disk itself made of, for example, a thin metal plate. By the way, when the reinforcing structure is provided on the disk, this causes the incident light from the light source to be partially blocked, thereby reducing the amount of received light, and
It is also possible that the position of the center of gravity of the transmitted light spot on the light receiving surface fluctuates and an error appears in the detection signal. Therefore,
An object of the present invention is to provide, in addition to the above-described basic objects, a correction structure that suppresses a reduction in the amount of received light caused by a reinforcing structure and a change in the center of gravity of a transmitted light spot.

[0006]

To achieve the above-mentioned object, the following means have been taken. That is, the optical rotary position detecting device according to the present invention includes a moving member and fixed light sources and fixed light receiving elements disposed on both sides of the moving member as basic components. The moving member is formed of a disk that is rotationally displaced, and has a spiral slit formed along the surface circumferential direction.
The fixed light source irradiates the moving member with incident light. The light receiving element has a long light receiving surface arranged along the radial direction of the disk, receives the transmitted light from the slit that moves in the radial direction along with the rotational displacement, and outputs a rotation position detection signal.
In such a configuration, the disk is reinforced by taking measures to provide a beam portion across the width direction of the slit. Further, a means of providing a pair of different size correction holes having a total area equal to the area of the beam portion is provided on both sides in the radial direction of the slit width corresponding to the beam portion to prevent a decrease in the amount of received light. I have. Assuming that the areas of the pair of correction holes are S1 and S2 and the distances between the center of gravity of each correction hole and the center of gravity of the beam portion are d1 and d2, respectively, d1 ·
The relationship of S1 = d2 · S2 is satisfied to prevent a change in the center of gravity of the transmitted light spot on the light receiving surface.

The correction hole is, for example, circular. In this case, if the radii of the pair of circular correction holes are r1 and r2, and the distance from the center of rotation of the disk to the center of gravity of the beam is R0, r1
/ (R0 + d1) = r2 / (R0-d2). In other words, the common tangent to the ends of the pair of circular correction holes is set so as to coincide with the radial direction from the center of rotation of the disk. The correction hole may be substantially trapezoidal. In this case, if the dimensions from the center of gravity of the pair of trapezoidal correction holes to the ends in the rotation direction are m1 and m2, respectively, m1 / (R0 + d
1) = m2 / (R0−d2) is satisfied. Therefore,
Similarly to the circular correction hole, a common tangent to the rotation direction ends of the pair of trapezoidal correction holes coincides with the radial direction from the center of rotation of the disk. Further, a common tangent line of the pair of correction holes,
The side end lines of the beams are made to coincide with each other so that the pair of correction holes and the beams enter the light receiving surface at the same time. In this case, the light receiving element is subjected to predetermined masking, and has a light receiving surface whose edge in the disk rotation direction is substantially parallel to the radial direction from the center of rotation of the disk.

[0008]

According to the present invention, the respective regions of the disk defined by the spiral slits are not separated but are connected to each other by the beam. Therefore, it is possible to suppress the bending deformation of the disk, and it is possible to increase the draft angle of the spiral as compared with the related art, so that the rotation detection angle range can be expanded. By the way, when a beam portion is provided in the slit, incident light from the light source is partially and intermittently blocked by the passage, and the light receiving state fluctuates. Specifically, the interposition of the beam portion causes a decrease in the amount of received light and a change in the position of the center of gravity. Therefore, a pair of correction holes is provided corresponding to the beam portion, and light equivalent to blocked light is introduced to the light receiving surface to correct fluctuations in the light receiving state. A pair of correction holes,
It is arranged on both sides in the radial direction of the slit width corresponding to the beam, and the total area thereof is equal to the area of the beam. If the areas of the pair of correction holes are S1 and S2, and the distance between the center of gravity of each correction hole and the center of gravity of the beam portion is d1 and d2, respectively, d1 · S1 = d2 ·
The relationship of S2 is satisfied. With this configuration, the light receiving surface can be irradiated with the same amount of light as the light blocked by the beam, and the center of gravity of the pair of correction holes matches the center of gravity of the beam. Therefore, the light passing through the pair of correction holes is equivalent to the light blocked by the beam, and the influence of the beam can be offset. In addition, the common tangent line in contact with the ends of the pair of correction holes and the side end line of the beam portion are aligned along the radial direction of the disk, and the edge of the light receiving surface in the disk rotation direction is substantially parallel to the radial direction of the disk. It is to be. Thereby, the pair of correction holes and the beam portion enter and exit the light receiving surface at the same time, so that the light receiving state does not fluctuate even during the transition during rotation.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic perspective view showing a basic configuration of an optical rotary position detecting device according to the present invention.
A disk 1 made of a light-shielding material such as metal is fixed to a rotating shaft 2 and can be rotated. The rotating shaft 2 is connected to a detection target (not shown). A spiral slit 3 that gradually expands from the center in the circumferential direction on the surface of the disk 1
Are formed. At a substantially middle point of the spiral slit 3, a beam portion 4 is provided in the width direction thereof, and the disk 1 is mechanically reinforced. In this example, two beams 4 are provided, but the invention is not limited to this. Further, the beam portion 4 is provided at a substantially middle point of the spiral slit 3, but the present invention is not limited to this. As a feature of the present invention, a pair of correction holes 5 are formed corresponding to the individual beam portions 4. The slit 3, the beam 4, and the correction hole 5 can be formed simultaneously by, for example, etching.

Above the disk 1, a light source 6, such as an LED, is fixedly arranged. The light source 6 emits substantially parallel light to the surface of the disk 1 via a light projecting lens fixed to the surface. On the other hand, a light receiving element 7 is fixedly arranged below the disk 1 in alignment with the light source 6. The light receiving surface 8 provided on the surface has a longitudinal shape along the radial direction of the disk 1. The transmitted light 9 from the spiral slit 3 moves in the radial direction along with the rotational displacement of the disk 1 and is received by the light receiving surface 8. The light receiving element 7 includes a light receiving position detecting element such as a PSD, for example, and outputs differential signals A and B to a pair of output terminals.
That is, the output signals A and B change differentially according to the light receiving position 11 of the transmitted light 9. More precisely, it changes according to the position of the center of gravity of the transmitted light 9. The output signals A and B are output from the difference circuit 1
0, a detection signal Vout representing the rotational position of the disk 1 is obtained.

FIG. 2 shows a plan view of the rotating disk 1. In this example, the draft angle of the spiral slit 3 is set to 350 °. If the beam 4 is not inserted, the slit 3
As a result, the region connecting the portions partitioned inward and outward in the width direction becomes extremely small, and the desired mechanical strength cannot be maintained. If the draft angle of the spiral is set to 350 °, the rotation position detection range extends from 0 ° to 350 °. In this example, the beam portion 4 is located substantially at the center (175
°). In this way, the pair of metal pieces separated by the slit 3 are connected at two positions symmetrical to each other with respect to the rotating shaft 2, so that a balanced reinforcing structure can be obtained. Further, the beam portion 4 is arranged at a central light receiving position where a pair of differential signals output from the light receiving element become substantially equal to each other. For this reason, the output of the light receiving element is designed so that adverse effects due to fluctuations in the light receiving state accompanying the passage of the beam during rotation can be eliminated as much as possible.

As a feature of the present invention, as shown in FIG. 3 (partially enlarged view), a beam portion 4 is provided in the width direction of the slit 3 to reinforce the disk, and a slit corresponding to the beam portion 4 is provided. A pair of correction holes are provided on both radial sides of the width. In this figure, for the sake of convenience, the radially outer correction hole is denoted by reference numeral 51, and the radially inner correction hole is denoted by reference numeral 5.
It is represented by 2. Both are circular, and the outer correction hole 5
1 has a relatively large opening area S1, and the inner correction hole 52 has a relatively small opening area S2. The total opening area S1 + S2 of the pair of correction holes 51 and 52
Is set to be equal to the shielding area S0 of the beam portion 4. Center of gravity (center of circular opening) W of one correction hole 51
1, the center of gravity of the other correction hole 52 (the center of the circular opening) W2,
The centers of gravity W0 of the beam portions 4 are arranged in a straight line along the same radius R of the rotating disk. The center of gravity W1 of one correction hole 51 is located at a relatively short distance d1 from the center of gravity W0 of the beam portion 4, and the center of gravity W2 of the other correction hole 52 is located at a relatively long distance d2 from the center of gravity W0 of the beam portion 4. A pair of correction holes 51 and 5
The relationship d1 · S1 = d2 · S2 holds between the two. The combined center of gravity of the pair of correction holes 51 and 52 and the center of gravity W0 of the beam portion 4 match, and both are optically equivalent. Therefore, the beam portion 4 interposed in the slit 3 has a pair of correction holes 51,
52, and the fluctuation of the light receiving state can be completely corrected.

Next, the operation of the optical rotational position detecting device according to the present invention will be described in detail with reference to FIG. In the state (A), the beam 4 provided in the slit 3 is located outside the light receiving surface 8. Accordingly, the light receiving element outputs a predetermined detection signal according to the position W of the center of gravity of the transmitted light area (indicated by hatching) from the slit 3 on the light receiving surface 8. next,
In the state (B), the disk rotates clockwise with respect to the light receiving surface 8, and the beam 4 enters the light receiving surface 8. Light receiving surface 8
The upper part of the transmitted light region is partially blocked and bisected by the beam part 4 as shown by hatching. The center of gravity W of the divided transmitted light area is offset from the normal center of gravity position.
Therefore, as shown in (B), if the correction hole is not provided, an error appears in the detection signal.
In addition, the amount of received light is reduced by the amount that is blocked by the beam 4,
This may cause a detection error. In view of this point, in the present invention, (C)
As shown in FIG. 7, a pair of correction holes 51 and 52 are provided corresponding to the beam portion 4. Since the total area of the pair of correction holes 51 and 52 is equal to the area of the beam portion 4, there is substantially no change in the amount of received light. Further, since the combined center of gravity of the pair of correction holes 51 and 52 coincides with the center of gravity of the beam portion 4, the center of gravity W
No offset occurs.

FIG. 5 is a plan view showing a main part of a second embodiment of the optical rotational position detecting device according to the present invention. To facilitate understanding, parts corresponding to those of the first embodiment shown in FIGS. 1 to 3 are denoted by corresponding reference numerals. In the present embodiment, regarding the pair of circular correction holes 51 and 52, in addition to the above-described relationship of S1 + S2 = S0 and d1 · S1 = d2 / S2, r1 / (R0 + d1) = r2 / (R0−d2).
The relationship is satisfied. Note that r1 represents the radius of one circular correction hole 51, r2 represents the radius of the other circular correction hole 52, and R0 represents the distance from the center of rotation O of the disk to the center of gravity W0 of the beam 4. As is clear from the figure, r1 / (R0 + d1) is a pair of correction holes 51 and 52.
Correction hole 5 for the radius R passing through the centers of gravity W1, W2 of
1 represents the tangent of a tangent line T that is in contact with the opening end of the opening 1. Similarly, r2 / (R0-d2) is the inside correction hole 52.
Represents the tangent of a tangent line T that is in contact with the opening end of the tangent line. Since both tangents are equal, a pair of correction holes 5
The open ends of the first and second 52 are located on the same tangent line T along the radial direction. In this embodiment, both ends 4 of the beam portion 4 are used.
1 and 42 are formed so as to coincide with the two common tangents T, respectively. Further, the light receiving surface 8 of the light receiving element 7 is masked with a predetermined pattern as shown by hatching, and both end edges 81 and 82 separated in the disk rotation direction are substantially parallel to the radial direction from the rotation center O of the disk. Has become.

The operation of the second embodiment shown in FIG. 5 will be described with reference to FIG. When the disk rotates counterclockwise with respect to the light receiving surface 8 from the state shown in FIG. 5, the beam 4 and the corresponding pair of correction holes 51 and 52 become one edge 81 of the light receiving surface 8.
To enter. At this time, the opening ends of the pair of correction holes 51 and 52 and one side end 41 of the beam portion 4 are aligned along the radial direction of the disk, and the edge 81 of the light receiving surface 8 is also parallel to the radial direction. Has become. Therefore, the correction holes 51 and 52 and the beam portion 4 enter the light receiving surface 8 at the same time, and the fluctuation of the light receiving state can be suppressed as much as possible even during such a transition. When the disk is further rotated in the counterclockwise direction, the pair of correction holes 51 and 52 and the beam 4 retreat from the other edge 82 of the light receiving surface 8. Also in this case, the opening ends of the correction holes 51 and 52 and the other side end 42 of the beam portion 4 are aligned along the radial direction, and are simultaneously separated from the edge 82 of the light receiving surface 8.

FIG. 7 shows a reference example for comparison. Parts corresponding to those of the second embodiment shown in FIG. 6 are given the same reference numerals to facilitate understanding. In this reference example, the pair of correction holes 51 and 52 have the same opening area and are aligned with the corresponding beam portion 4 on the same radius R.
The total opening area of the correction holes 51 and 52 and the shielding area of the beam 4 are set to be equal. However, both correction holes 51,
Since 52 have the same dimensions, the common tangents connecting the ends do not coincide in the radial direction. Therefore, the pair of correction holes 51, 52
When the light enters the edge of the light receiving surface 8, there is a time difference between the time when the opening end of the inner correction hole 52 enters and the time when the opening end of the outer correction hole 51 enters, and the light receiving state fluctuates transiently. Occurs. Therefore, the center of gravity of the transmitted light area on the light receiving surface 8 is shifted from the normal position, and a detection error occurs.

FIG. 8 is a plan view of a main part of a third embodiment of the optical rotary position detecting device according to the present invention. Basically, it has the same structure as that of the second embodiment shown in FIG. 5, and corresponding parts are denoted by corresponding reference numerals to facilitate understanding. The difference is that a pair of correction holes 51 and 5 are provided.
2 is a trapezoid. However, the upper and lower ends of the correction hole may be formed in an arc shape as shown by a dotted line. Also in this embodiment, the total opening area S of the pair of trapezoidal correction holes 51 and 52 is set.
1 + S2 is set to be equal to the shielding area S0 of the beam 4, and the relationship of d1 · S1 = d2 · S2 is also satisfied. In addition, m1 / (R0 + d1) = m2 / (R0−d
The relationship of 2) is satisfied. Here, m1 represents the dimension from the center of gravity W1 of the outer trapezoidal correction hole 51 to the end in the rotation direction, and m2 represents the dimension from the center of gravity W2 of the inner trapezoidal correction hole 52 to the end in the rotation direction. With such a configuration, the common tangent line T that contacts the opening ends of the correction holes 51 and 52 coincides with the radial direction. Accordingly, similarly to the second embodiment shown in FIG. 5, the pair of trapezoidal correction holes 51 and 52 can enter and exit the light receiving surface 8 at the same time.

[0018]

As described above, according to the present invention, the disk is mechanically reinforced and bent by providing a beam portion for the spiral slit formed in the rotating disk made of a thin metal plate or the like. This has the effect of suppressing Further, by providing a correction hole corresponding to the beam portion, there is an effect that the detection output of the light receiving element can be stabilized.

[Brief description of the drawings]

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

FIG. 2 is a plan view showing the shape of a disk incorporated in the optical rotation position detecting device according to the present invention.

FIG. 3 is a partial plan view showing a first embodiment of a correction hole which is a feature of the present invention.

FIG. 4 is a schematic diagram for explaining the operation of the first embodiment.

FIG. 5 is a partial plan view showing a second embodiment of a correction hole which is a feature of the present invention.

FIG. 6 is an operation explanatory diagram of the embodiment shown in FIG. 5;

FIG. 7 is a partial plan view showing a reference example of a correction hole.

FIG. 8 is a partial plan view showing a third embodiment of a correction hole which is a feature of the present invention.

FIG. 9 is a perspective view showing a conventional optical rotational position detecting device.

FIG. 10 is a graph showing a relationship between a rotation angle of the optical rotation position detection device and a detection signal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Disk 2 Rotation axis 3 Slit 4 Beam part 5 Correction hole 6 Light source 7 Light receiving element 8 Light receiving surface 9 Transmitted light 10 Difference circuit 11 Light receiving position

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-47-41861 (JP, A) JP-A-60-259909 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01D 5/26-5/38 G01B 11/00-11/30 G01P 1/00-3/80

Claims (8)

(57) [Claims] 1. A moving member comprising a disk which is rotationally displaced and having a helical slit formed on the surface thereof along a circumferential direction, a fixed light source for irradiating the moving member with incident light, and a radial direction of the disk. Optical position detecting device comprising a fixed light receiving element for receiving transmitted light from a slit that moves in the radial direction along with the rotational displacement and that outputs a rotational position detection signal, the light receiving surface having a longitudinal light receiving surface arranged in a vertical direction. In the above, a beam portion is provided along the width direction of the slit to reinforce the disc, and a pair of sizes having a total area equal to the beam area on both sides in the radial direction of the slit width corresponding to the beam portion. An optical rotational position detecting device having a correction hole. 2. The area of a pair of correction holes is defined as S1 and S2,
The distance between the center of gravity of each correction hole and the center of gravity of the beam part is d1, d2, respectively.
The optical rotational position detecting device according to claim 1, wherein the following relationship is satisfied: d1 · S1 = d2 · S2. 3. The optical rotational position detecting device according to claim 2, wherein the correction hole is circular. 4. The radii of the pair of circular correction holes are r1 and r, respectively.
And the distance from the center of rotation of the disk to the center of gravity of the beam is R
4. The optical rotational position detecting device according to claim 3, wherein when 0 is satisfied, a relationship of r1 / (R0 + d1) = r2 / (R0-d2) is satisfied. 5. The optical rotational position detecting device according to claim 2, wherein the correction hole has a substantially trapezoidal shape. 6. The distance from the center of gravity of each of the pair of trapezoidal correction holes to its end in the direction of rotation is m1, m2, and the distance from the center of rotation of the disk to the center of gravity of the beam is R0: m1 / (R0 + d1) 6. The optical rotational position detecting device according to claim 5, wherein the following relationship is satisfied: m2 / (R0-d2). 7. A moving member comprising a disk which is rotationally displaced and having a helical slit formed on the surface thereof along a circumferential direction, a fixed light source for irradiating the moving member with incident light, and a radial direction of the disk. Optical position detecting device comprising a fixed light receiving element for receiving transmitted light from a slit that moves in the radial direction along with the rotational displacement and that outputs a rotational position detection signal, the light receiving surface having a longitudinal light receiving surface arranged in a vertical direction. In the above, a beam portion is provided along the width direction of the slit to reinforce the disk, and a pair of correction holes having a total area equal to the area of the beam portion are provided on both sides in the radial direction of the slit width corresponding to the beam portion. An optical system characterized in that a common tangent to the ends of the pair of correction holes and a side end line of the beam coincide with each other so that the pair of correction holes and the beam enter the light receiving surface simultaneously. Type rotational position detector. 8. The optical rotation position detecting device according to claim 7, wherein the light receiving element has a light receiving surface whose edge in the disk rotation direction is substantially parallel to the radial direction from the rotation center of the disk. .