JPH0771983A - Reference-position detecting device - Google Patents

Abstract

PURPOSE:To accurately detect a reference position by obtaining a signal of a steep reference position. CONSTITUTION:The reference-position detecting device comprises a rotor 22 formed from glass or the like and rotated by a drive, a light-emitting diode 16 emitting light toward the rotor 22, and a phototransistor 18, etc., for receiving the light that is emitted from the light emission means 16 and transmitted through the rotor 22. The rotor 22 has a reference-position detecting portion 22b projected from the surface facing the light emission means 16. The reference-position detecting portion 22b gathers and transmits the light from the light emission means 16 and directs it to the light reception means 18, so that the light reception means 18 receives the light of great illumination.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reference position detecting device for use in an encoder that outputs a number of pulse signals proportional to a rotation angle of an input shaft, for detecting a reference (origin) position of the input shaft. Is.

[0002]

2. Description of the Related Art FIG. 4 is a perspective view showing a schematic structure of an example of a conventional rotary encoder. The input shaft 11 of the encoder 10 is rotatably supported. The slit disk 12 is formed of a member such as glass or acrylic and is attached to the input shaft 11. A predetermined number of slits 12 a are formed on the outer peripheral portion of the slit disk 12 at equal intervals along the circumferential direction. Further, a home slit 12b is formed on the inner peripheral side of the slit disk 12. The home slit 12b is formed by forming a plurality of slits with different intervals.

On the upper side of the slit disk 12 in the figure, fixed slit plates 13 and 14 are arranged in parallel with the slit disk 12. The fixed slit plate 13 is formed with slits 13a having the same spacing as the slits 12a.
Similarly, the fixed slit plate 14 includes the home slit 12
The same slit 14a as b is formed.

Further, on the lower side of the slit disk 12 in the figure, a light emitting diode 15 as a light emitting means is provided at a position corresponding to the slit 12a and the home slit 12b, respectively.
16 are arranged. In addition, the fixed slits 13 and 14
On the upper side of the figure, the phototransistor 1 as a light receiving means is provided so as to face the light emitting diodes 15 and 16, respectively.
7 (17a and 17b) and 18 are arranged. The home slit 12b of the slit disk 12, the fixed slit plate 14, the light emitting diode 16, and the phototransistor 18 constitute a reference position detecting device for detecting the reference position of the input shaft 11.

Next, the operation of the encoder 10 will be described. The input shaft 11 is rotated by a drive unit (not shown), which causes the slit disk 12 to rotate. The light emitting diodes 15 and 16 are driven by a power circuit (not shown) and irradiate the slit disk 12 with light.

When the light emitted from the light emitting diodes 15 and 16 passes through the rotating slit disc 12 and the fixed slit plates 13 and 14, the transmitted light causes moire fringes. This moire fringe is caused by the phototransistor 17,
The light is received by 18 and converted into an electric signal. This electric signal is amplified and output by an amplifier (not shown).

FIG. 5 shows a phototransistor 17 (17
It is a figure which shows an example of the output signal obtained by a, 17b) and 18. Phototransistors 17a and 17b
Is adjusted so that the phases of the output signals A and B of the two are shifted from each other by 90 ° (electrical angle), and the phase is also reversed by reversing the rotation direction. Therefore, by combining with a reversible counter having a direction discrimination circuit The number of rotations can be added or subtracted.

The output signal C is the home slit 12
b is the slit 14a of the fixed slit plate 14 and the input shaft 11
Output when the directions match. That is, it is detected once for each rotation of the slit disk 12. Therefore, the desired position can be set to the reference position by the output signal C.

[0009]

However, the above-mentioned conventional encoder has the following problems. In order to accurately detect the reference position, the output signal C must be a steep signal. For this reason, the home slit 12b and the slit 14a of the fixed slit plate 14 are composed of a plurality of slits having different slit intervals, and both of them are provided on the input shaft 1.
Light having a high illuminance is received by the phototransistor 18 only when they match in one direction. However, such a shape has a problem in that it is difficult to manufacture and the cost is high.

Further, today, a high-resolution encoder is required in order to cope with highly accurate measurement and control. However, there is a manufacturing limit on the number of slits 12a that can be formed in the slit disk 12. Therefore,
Conventionally, the gap between the slit disk 12 and the fixed slit plate 13 is set to about 80 μm and only the 0th order light is received by the phototransistor 17, but the gap between them is set to about 3 mm and the ± first order is set. By receiving the interference light, 0
An encoder having a resolution twice as high as that of only the next light has been proposed. Further, by securing a large gap between the two in this way, the slit disk 12 and the fixed slit plate 1 may be different due to manufacturing errors or mounting errors of each component.
It is possible to eliminate the possibility of contact with 3, 14.

However, when the gap between the slit disk 12 and the fixed slit plate 13 is increased, the fixed slit plates 13 and 14 are generally formed integrally, so that the slit disk 12 and the fixed slit plate 14 are integrated. The gap also becomes larger,
There is a problem that the output signal C cannot be a steep output signal and the detection accuracy of the reference position decreases. If the fixed slit plates 13 and 14 are formed separately, there is a problem that the manufacturing cost increases.

The present invention has been made in order to solve the above-mentioned problems. Even when the gap is set large, the reference position can be set by obtaining a signal of a steep reference position. The purpose is to detect accurately.

[0013]

In order to achieve the above-mentioned object, a first solution means of a reference position detecting device according to the present invention comprises a rotating body (22) rotated by a drive unit and the rotating body. A light emitting means (16) for irradiating light, and a light receiving means (1) for receiving the light from the light emitting means transmitted through the rotating body.
8) The reference position detecting device according to claim 8, wherein the rotating body is formed in a substantially convex shape on the surface on the light emitting means side and collects the light from the light emitting means and transmits the light to the light receiving means side. It is characterized by including a reference position detection unit (22b).

The second means for solving the problems comprises a rotating body (32) rotated by a drive unit, a light emitting means (16) for irradiating the rotating body with light, and the light emitting means reflected by the rotating body. A light receiving means (18) for receiving light, wherein the rotating body is formed in a substantially concave shape on its surface to collect the light from the light emitting means to the light receiving means side. It is characterized by comprising a reference position detection unit (32b) for reflecting.

A third solving means is the above-mentioned second solving means, wherein the optical path direction of the reflected light of the reference position detecting section (42b) is different from the optical path direction of the reflected light on the other surface of the rotating body. The light receiving unit is arranged on the optical path of the reflected light of the reference position detection unit.

A fourth solving means is the above-mentioned first to third solving means, wherein light is allowed to pass through an opening (24a) formed in a part between the rotating body and the light receiving means. A slit plate (24) for allowing the light receiving means to receive the light that has passed therethrough is provided.

[0017]

In the first or second solving means, when the light is emitted from the light emitting means, the reference position detecting portion collects the light and reflects or transmits the light to the light receiving means side. Therefore, the light receiving means can receive light with high illuminance.

In the third solving means, the optical path of the reflected light of the reference position detecting section is different from the optical path of the reflected light of the other surface, and the light receiving means is arranged on the optical path of the reflected light of the reference position detecting section. To be done. In the fourth solving means, the light is received by the light receiving means through the opening of the slit plate arranged between the rotating body and the light receiving means. Therefore, it is possible to further increase the difference in illuminance of the light received by the light receiving means when the reference position detection unit is irradiated with light and when it is not irradiated.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the reference position detecting device according to the present invention will be described below with reference to the drawings. The same parts as those shown in the conventional example are designated by the same reference numerals, and the duplicated description will be appropriately omitted.

FIG. 1 shows a first reference position detecting apparatus according to the present invention.
It is a schematic block diagram which shows the Example of. In the reference position detecting device of FIG. 1, the slit disc 22 is formed of a member such as glass or acrylic. Further, the reference position detector 22b is provided on the surface of the slit disk 22 on the side of the light emitting diode 16 and is formed so as to protrude in a substantially convex shape ((a) in the figure). The reference position detection unit 22b may be provided by adhering a light-transmitting convex body to the slit disc 22 or may be integrally formed with the slit disc 22. The fixed slit plate 24 is arranged between the phototransistor 18 and the slit disc 22 and has one slit 24a (opening). Therefore, the light passing through the slit 24a is received by the phototransistor 18.

As shown in FIG. 1A, when the light from the light emitting diode 16 is applied to the reference position detecting portion 22b, the light transmitted to the phototransistor 18 side is fixed slit by the reference position detecting portion 22b. Slit 24 of plate 24
It is focused near a. Therefore, the light with strong illuminance is received by the phototransistor 18. Further, as shown in FIG. 1B, when the area other than the reference position detecting portion 22b of the slit disk 22 is irradiated with the light, the light is diverged to the phototransistor 18 side, and the light with low illuminance is changed. The light is received by the phototransistor 18.

Based on this difference in illuminance, the reference position detector 22
The output signal of b becomes a steep signal, and the reference position detection unit 2
The position of 2b can be accurately detected. In addition, by adjusting the shape of the convex portion of the reference position detection unit 22b,
Since the light can be condensed at a desired position, even if the gap between the slit disk 22 and the fixed slit plate 24 is set to be large, the phototransistor 18 can receive the light with high illuminance.

FIG. 2 is a schematic block diagram showing the second embodiment of the present invention. In the reference position detecting device of FIG. 2, a reflective layer (not shown) having a high reflectance such as gold or aluminum is formed on the upper surface of the slit disk 32 in the figure. Therefore, the light emitting diode 16 is arranged on the phototransistor 18 side. Reference position detector 3
2b is provided on the surface of the slit disk 32 on the side of the light emitting diode 16 and the phototransistor 18, and is formed in a substantially concave shape. The reference position detector 32b is formed so that its optical axis 39 is substantially perpendicular to the slit disk 32. The reference position detector 32b
A concave body having a reflective surface may be attached to the slit disk 32.

When light is emitted from the light emitting diode 16 to the reference position detector 32b, the reflected light is condensed by the reference position detector 32b in the vicinity of the slit 24a of the fixed slit plate 24. Therefore, the light with strong illuminance is received by the phototransistor 18. Further, as shown in FIG. 2B, when light is applied to a region other than the reference position detection portion 32b of the slit disk 32, the reflected light is diverged to the phototransistor 18 side and light with low illuminance is emitted. Is received by the phototransistor 18.

FIG. 3 is a schematic block diagram showing a third embodiment of the present invention, showing a modification of the second embodiment. In the reference position detecting device of FIG. 3, the slit disk 4
The second reference position detector 42b is formed such that its optical axis 49 is inclined with respect to the slit disk 42 by a predetermined amount. Further, the light emitting diode 16 and the phototransistor 18 are arranged so as to be symmetrical with respect to the optical axis 49.

When light is emitted from the light emitting diode 16 to the reference position detector 42b, the reflected light is condensed by the reference position detector 42b in the vicinity of the slit 24a of the fixed slit plate 24 and is received by the phototransistor 18. It
Further, as shown in FIG. 3B, when light is applied to a region other than the reference position detecting portion 42b of the slit disc 42, the reflected light diverges in a direction symmetrical to the incident direction of light. The reflected light hardly passes through the slit 24a of the fixed slit plate 24. Therefore, the reflected light is hardly received by the phototransistor 18. This makes it possible to further increase the difference in illuminance of the light received by the phototransistor 18 when the light is applied to the reference position detector 42b and when it is not applied.

An embodiment of the reference position detecting device according to the present invention has been described above. However, the present invention is not limited to the above-mentioned embodiment, and various modifications can be made without departing from the scope of the invention. is there. For example, in the embodiment, the reference position detecting portions 32b and 42 are provided on the surfaces of the slit disks 32 and 42.
Although b is formed, the reference position detectors 32b and 42b may be directly formed on the input shaft 11 of FIG. 4, for example.

In the embodiment, the fixed slit plate 24 is provided in the vicinity of the front surface of the phototransistor 18, but this is for the purpose of shielding unnecessary light from the outside and improving the sensitivity of the phototransistor 18. When the influence of outside light is small, the fixed slit plate 24 may not be provided.

The present invention can be applied to various rotary, angle and displacement measuring instruments, positioning controllers and the like in addition to rotary encoders and linear encoders.

[0030]

According to the reference position detecting device of the first or second aspect of the invention, since the reference position detecting portion collects the light and transmits or reflects it to the light receiving means side, the light receiving means is
It is possible to receive light with high illuminance. As a result, the output signal of the reference position detector becomes a steep signal, and the position of the reference position detector can be accurately detected. Also,
By changing the shape of the reference position detector, it is possible to collect light at a desired position, so even if the gap between the rotating body and the light receiving means is set large, the light receiving means receives light with strong illuminance. Can be made.

According to the reference position detecting device of the third or fourth aspect, the difference in illuminance of the light received by the light receiving means when the reference position detecting portion is irradiated with light and when it is not irradiated is further increased. As a result, the reference position can be detected more accurately, and the detection accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing a third embodiment of the present invention.

FIG. 4 is a perspective view showing a schematic configuration of an example of a conventional rotary encoder.

5 is a diagram showing an example of output signals obtained by phototransistors 17 and 18. FIG.

[Explanation of symbols]

 16 Light emitting diode 18 Phototransistor 22, 32, 42 Slit disk 22b, 32b, 42b Reference position detection part 24 Fixed slit plate 24a Slit (opening) 39, 49 Optical axis of reference position detection part 32b, 42b

Claims (4)

[Claims] 1. A reference position including a rotating body rotated by a drive unit, a light emitting means for irradiating the rotating body with light, and a light receiving means for receiving light from the light emitting means that has passed through the rotating body. In the detection device, the rotating body includes a reference position detection unit that is formed in a substantially convex shape on the surface of the light emitting unit side and that collects light from the light emitting unit and transmits the light to the light receiving unit side. Characteristic reference position detection device. 2. A reference provided with a rotating body rotated by a driving unit, a light emitting means for irradiating the rotating body with light, and a light receiving means for receiving light from the light emitting means reflected by the rotating body. In the position detecting device, the rotating body includes a reference position detecting unit that is formed in a substantially concave shape on a surface thereof and that collects light from the light emitting unit and reflects the light toward the light receiving unit. Position detection device. 3. The reference position detection device according to claim 2, wherein the reference position detection unit is formed such that the optical path direction of the reflected light is different from the optical path direction of the reflected light on the other surface of the rotating body. The reference position detecting device is characterized in that the light receiving means is arranged on the optical path of the reflected light of the reference position detecting section. 4. The reference position detection device according to claim 1, wherein light is passed through an opening formed in a part between the rotating body and the light receiving means, and the light is passed therethrough. A reference position detecting device, characterized in that a slit plate is provided for allowing the light receiving means to receive light.