JP2570515Y2 - 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 transmission type rotational position detecting device. More specifically, the present invention relates to a position adjusting structure for a light receiving element and a rotating disk having a spiral slit.

[0002]

2. Description of the Related Art Various types of optical rotational position detecting devices are conventionally known. For example, JP-A-60-2250
No. 24 discloses a structure using a rotating disk having a spiral slit. As shown in FIG. 7, a disk 102 is attached to the optical rotary position detecting device having this structure so as to be rotatable about a rotary 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. A light source 104 is fixedly arranged to irradiate the disk 102 with incident light. Also, disk 102
The light receiving element 105 is fixedly arranged at a position directly opposite to the light source 104 via the. The light receiving element 105 has a long light receiving surface 106 arranged along the radial direction of the disk 102, and receives the transmitted light from the slit that moves in the radial direction along with the rotational displacement of the disk 102, and Outputs a detection signal.

[0003]

FIG. 8 is a graph showing 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 rotation angle and the light receiving position in the radial direction are in a proportional relationship. The light receiving element outputs a detection signal according to the light receiving position. Therefore, in principle, the rotation angle and the detection signal have a linear relationship.

In the graph of FIG. 8, the horizontal axis represents the disk rotation angle as the mechanical angle φ, and the vertical axis represents the detection signal as the electrical angle θ. The mechanical angle can range from φA to φB in the positive and negative directions around the reference point φO. This range corresponds to the draft angle of the substantially spiral slit and is an effective rotation detection area. Generally, the absolute values of φA and φB are set equal. On the other hand, the fixed light receiving element is positioned so that the electrical angle correctly matches the mechanical angle. That is, when the adjustment is correctly performed, the electrical angle becomes the central point θO when the mechanical angle is at the reference point φO. When the mechanical angle is φA, the electrical angle is θ
A, and when the mechanical angle is φB, the electrical angle is θB. In this case, the absolute values of θA and θB are set to be equal.

However, there is a problem in that it is actually difficult to perform relative positioning between the rotating disk and the light receiving element so that the mechanical angle and the electrical angle coincide. 2. Description of the Related Art Conventionally, in positioning adjustment of a light receiving element, first, a disk is rotated once, an output range of a detection signal is measured, and a reference point of a spiral slit is temporarily set based on the result. The radial position of the light receiving element is adjusted so that the detection signal is at a predetermined reference level with respect to the provisionally set reference point. In this state, the disk is rotated again, and the output range of the detection signal is measured to check whether the electrical angle matches the mechanical angle. Normally, it is difficult to exactly match the electrical angle and the mechanical angle in one adjustment operation, and the same procedure is repeated while changing the position of the light receiving element in a direction to reduce the error between them. That is, since the adjustment is performed by repeating trial-and-error operations, there is a problem that a great deal of labor and skill are required for alignment and high accuracy cannot be obtained.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned problems in the prior art, an object of the present invention is to provide an adjustment structure that can easily match the mechanical angle of a rotating disk with the electrical angle of a detection signal. I do. The following measures were taken to achieve this purpose. That is, the optical rotary position detecting device according to the present invention is basically composed of a moving member and fixed light sources and fixed light receiving elements arranged on both sides thereof.
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,
The transmitted light from the slit width portion that moves in the radial direction with the rotational displacement is received, and a rotational position detection signal is output. In this configuration, the disk is provided with a slit for adjusting the position detection signal at a position symmetrical to a reference point of the spiral slit with respect to the center of rotation. Preferably, the size and shape of the adjusting slit are set so as to have the same output as the rotational position detection signal corresponding to the reference point.

[0007]

According to the present invention, an adjusting slit is provided at a point symmetrical point with the reference point of the spiral slit. In other words, the adjustment slit is equivalent to the reference point width of the spiral slit, and the positioning and fixing of the light receiving element is performed using the adjustment slit. That is, the position of the light receiving element in the radial direction is set so that the detection signal becomes a predetermined reference level in a state where the adjustment slit and the light receiving element are aligned. This setting can be performed in one operation and is extremely simple. Next, when the disk is rotated by 180 °, the reference point of the spiral slit is correctly aligned with the fixed light receiving element. As described above, since the reference point width portion of the spiral slit and the adjustment slit are equivalent, the detection signal automatically becomes a predetermined reference level. In this manner, the mechanical angle of the rotating disk and the electrical angle of the rotational position detection signal can be accurately matched by one adjustment operation.

[0008]

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 plan view showing a rotating disk which is a main component of the optical rotational position detecting device according to the present invention. The disk 1 is attached to a rotating shaft 2 and can be rotationally displaced. A spiral slit 11 is provided along the surface circumferential direction of the disk 1. The spiral indicated by the dashed line is drawn geometrically with reference to the center O of the disk 1. The spiral slit 11 has a reference point φ = 0 °
And the mechanical angle is set between φ = + 60 ° and φ = −60 ° in both the positive and negative directions. In order to eliminate an error at both ends of the slit 11, the draft angle may be set to be larger than the effective mechanical angle in advance. A light source (not shown) is fixedly arranged on the upper surface side of the disk 1, and a light receiving element 3 is fixedly arranged on the lower surface side of the disk 1 so as to face the light source. The light receiving element 3 has a long light receiving surface 31 aligned along the radial direction of the disk 1. The light transmitted through the slit 11 is received by the light receiving surface 31 and a rotation position detection signal is obtained. The light receiving position moves linearly in the radial direction as the disk 1 rotates. In the illustrated state, the reference point of the spiral slit 11 is exactly aligned with the light receiving surface 31.

As a characteristic of the present invention, the center O of the disk 1 is
The adjustment slit 12 is provided at a position symmetrical to the reference point of the spiral slit 11. The dimensions and position of the adjustment slit 12 are set so as to be the same output as the rotational position detection signal corresponding to the reference point. Specifically, the adjustment slit 12 is located at a position rotated by 180 ° from the reference point of the spiral slit 11, and the radial distance from the rotation center O is set to be equal to each other. In addition, the draft angle of the adjustment slit 12 is set to, for example, 10 °. Preferably, the adjustment slit 12 has a shape in which a portion of the spiral slit 11 located at the reference point is cut out and transferred to a symmetrical position.

Next, an adjusting operation using the above-mentioned adjusting slit will be described with reference to FIG. (A) shows the adjusted state, and (B) shows the unadjusted state. In this example, the light receiving element is driven by a single power supply, and 2.5 V when the mechanical angle φ = 0 °.
At the reference output level. ± 60 around φ = 0 °
° can be detected, and the output changes by ± 2 V. That is, when the minimum mechanical angle φ = −60 °, an output of 0.5 V is obtained, and when the maximum mechanical angle φ = + 60 °, an output of 4.5 V is obtained. This output is set symmetrically with respect to the reference level 2.5V. Preferably, in order to stabilize the output, automatic light amount control is performed on the fixed light source so that the amount of received light is constant. In this case, the light receiving amount is extremely reduced in a portion where there is no spiral slit, so that the automatic light amount control works so as to increase the light amount of the light source as much as possible, and the light source may be broken. Therefore, in the part without slit, the light amount is limited,
A reference level detection output of 2.5 V is obtained.

[0011] As shown in FIG.
If the motor is rotated by 60 ° one rotation, an imbalanced detection signal is output because the mechanical angle and the electrical angle do not match. That is, the reference point φ =
The output level of the detection signal at 0 ° is the reference level 2.5.
V, and the output levels V + and V− at both ends of the spiral slit are unbalanced due to the offset. Note that the output level is maintained at 2.5 V by the above-described control in the portion having no slit. Further, when the reference point φ is rotated 180 ° from 0 °, a small peak appears because the light source light is received through the above-described adjustment slit. This peak level is equivalent to the above-described offset because the reference points of the adjustment slit and the spiral slit are equivalent. In other words, 180
If a peak appears while rotating, it indicates that adjustment is not completed. In other words, if the radial position of the light receiving element is adjusted so that the output of the adjusting slit becomes 2.5 V, the positional relationship with the spiral slit becomes optimal, and the output of the spiral slit becomes uniform around 2.5 V. It comes to touch. Thus, according to the present invention,
Strict position adjustment of the light receiving element can be performed only by monitoring only the output of the adjustment slit, so that the adjustment time can be shortened and the assembly cost can be reduced.

In the conventional adjusting method, a reference point is temporarily determined in advance, and the output at that position is monitored to temporarily determine the position of the light receiving element in the radial direction. In this case, as the reference point, the midpoint (0 °) of the spiral slit or the end point (+
(60 ° or -60 °) is conceivable, but at the end point, the signal is degraded at the end points, which is not appropriate. The midpoint of the slit is defined as a portion having an intermediate value between the maximum value and the minimum value of the output over the entire output range by rotating the disk once, but does not completely match due to signal deterioration at the slit end point. If they do not match, an imbalance occurs in the electrical angle between the positive side and the negative side. To eliminate this imbalance, 0
It is necessary to adjust the output levels at three points, °, + 60 °, and -60 °. The procedure is to rotate the disk.
Set to the position of 5V output. This is set to 0 ° and the rotation is ± 60 °, and the outputs V + and V− at that time are measured. (V +)-
Unless 2.5V = 2.5V- (V-), ((V +)
− (V −)) / 2, the position of the light receiving element is shifted to the smaller one of V + and V−, the disk is rotated again to adjust to the 2.5V point, and then the output of ± 60 ° is measured. This procedure is repeated until the above equation is satisfied. As described above, in the conventional method, an extremely low-accuracy method of using the measurement result of the entire signal output to determine the midpoint position of the slit has been adopted.

FIG. 3 is a schematic sectional view showing an example of the overall configuration of the optical rotational position detecting device according to the present invention. Bearings 5a and 5b and a light source 6 are attached to the main body 4. The rotating shaft 2 is inserted into the bearings 5a and 5b. One end of the rotating shaft 2 is press-fitted with a rotor bush 21 and abuts the bearing 5b. The bearing 5a side is fixed by a G ring 22. Further, a coil spring 23 is interposed between the bearings 5a and 5b, and the thrust play of the rotating shaft 2 is reduced by applying pressure from the inside and pressing the bearing to the outside. The disk 1 is inserted into the rotor bush 21 and fixed by an SE ring 24. The disk 1 has a helical slit 11, an adjusting slit 12, and a rotary shaft insertion hole 13. The light source 6 is fixed to the main body 4 so as to irradiate the spiral slit 11. On the other hand, the light receiving element 3 is mounted on a circuit board 7 on which a signal detection circuit is mounted, and is arranged so as to face the light source 6 via the disk 1. The circuit board 7 is fixed to the main body 4 via a board holder 8.

The light emitted from the light source 6 is transmitted to a lens member 61.
The light is turned into substantially parallel light, and the rotating disk 1 is irradiated. The light transmitted through the spiral slit 11 reaches the light receiving surface 31 of the light receiving element 3. When the disk 1 is rotated, the light receiving position moves in the radial direction. This movement amount is linear with respect to the rotation angle.

FIG. 4 is a schematic diagram showing the planar shape of the light receiving element 3. As shown in the figure, a long light receiving surface 31 is formed on the surface of the light receiving element 3, and a pair of photocurrents which decrease in proportion to the distance from the inner end a and the outer end b in the radial direction to the light receiving position. Ia and Ib are output.

FIG. 5 is a graph showing the relationship between the light receiving position and the photocurrent. As is clear from the graph, the pair of photocurrents I
a and Ib change differentially and cross each other at the midpoint c when properly adjusted. When the pair of photocurrents is subjected to difference processing to generate a rotational position detection signal, common-mode noise can be removed and the sensitivity can be doubled. However, it is easily affected by a change in the amount of received light due to a change in the light amount of the light source or a variation in the width of the spiral slit. For this reason, it is preferable to constantly monitor the amount of received light and feed back the information to automatically control the amount of light from the light source so that the amount of received light becomes constant.

Finally, FIG. 6 is a circuit block diagram showing a configuration example of the drive circuit mounted on the circuit board 7 shown in FIG. As illustrated, in this example, a PSD is used as the light receiving element 3, and a pair of photodiodes PDa, PDa,
It is represented by PDb. One photodiode PDa
Is output to the corresponding voltage signal Va via the buffer 91a. Similarly, the photocurrent Ib output from the other photodiode PDb is converted into a corresponding voltage signal Vb via the buffer 91b. The pair of voltage signals Va and Vb are subjected to differential processing by the comparator 92 to obtain a rotational position detection signal Vout.

On the other hand, the PSD average signal obtained from the output terminals of the pair of buffers 91a and 91b is input to the automatic light amount control circuit 93, and automatically controls the light emission amount of the light source 6 composed of LEDs. That is, the above-described PSD average signal is applied to the negative input terminal of the differential amplifier 94, and a predetermined reference voltage Vref2 is applied to the positive input terminal. The drive transistor 95 is controlled so as to cancel the difference between the two, and the light emission amount of the LED becomes constant. The light amount of the light source is adjusted by the automatic light amount control circuit 93 so that the amount of received light is always constant, and the influence of the change of the spiral slit width and the unevenness of the light source light distribution is eliminated.

[0019]

As described above, according to the present invention, the adjusting slit is provided at a position symmetrical to the reference point of the spiral slit with respect to the center of rotation of the disk. The shape and dimensions of the adjusting slit are set so that the same output as the rotational position detection signal corresponding to the reference point is obtained. By adjusting the radial position of the light receiving element while monitoring only the signal output of the adjustment slit, the electrical angle and the mechanical angle can be easily matched, simplifying the adjustment work and achieving high-precision alignment. There is an effect that.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing a disk which is a main component of the optical rotational position detecting device according to the present invention.

FIG. 2 is a diagram for explaining a method for adjusting a light receiving element based on the present invention.

FIG. 3 is a schematic cross-sectional view showing an example of the entire configuration of the optical rotational position detecting device according to the present invention.

FIG. 4 is a schematic diagram illustrating a planar shape of a light receiving element.

FIG. 5 is a graph showing an output signal of a light receiving element.

FIG. 6 is a circuit diagram showing an example of a drive circuit incorporated in the optical rotation position detecting device according to the present invention.

FIG. 7 is a perspective view showing a conventional optical rotational position detecting device.

FIG. 8 is a graph showing a relationship between a rotation angle and a detection signal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Disc 2 Rotation axis 3 Light receiving element 4 Main body 6 Light source 7 Circuit board 11 Spiral slit 12 Adjustment slit 31 Light receiving surface 93 Automatic light amount control circuit

Claims (2)

(57) [Scope of request for utility model registration] 1. A moving member comprising a disk which is rotationally displaced and having a spiral slit formed along a surface circumferential direction thereof,
A fixed light source for irradiating the moving member with incident light, and a transmitted light from a slit having a long light receiving surface disposed along the radial direction of the disk and having a radially movable shape with rotational displacement. An optical rotary position detecting device comprising: a fixed light receiving element that outputs a rotational position detection signal; wherein the disk has a slit for adjusting the rotational position detection signal at a position symmetrical to a reference point of the spiral slit with respect to a rotation center. An optical rotational position detecting device comprising: 2. The optical rotational position detecting device according to claim 1, wherein the adjusting slit is set to have the same output as a rotational position detection signal corresponding to the reference point.