JPH06294666A - Absolute type encoder - Google Patents

Abstract

PURPOSE:To conduct monitoring of the quantitative fluctuation of light emitted from a light emitting element without increasing the outer size and without sacrifice of output of a rotational position detection signal. CONSTITUTION:Slits 201-203 for monitoring the quantity of light are made in a fixed slit plate 31 along the peripheral direction corresponding to tracks 17-19 for detecting the rotational position made in a rotary slit plate 21. In this regard, the tracks 17-19 also serve as tracks for monitoring the quantity of light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical absolute encoder capable of obtaining an absolute position output according to a rotational angle position regardless of whether or not it is rotated.

[0002]

2. Description of the Related Art FIG. 6 is a schematic configuration diagram of such an optical absolute encoder.

[0003] The absolute type encoder, a plurality light emitted from the light emitting element 1 ₁ to 1 ₃ (shown three),
The rotary slit plate 2 having an optical slit having a binary code pattern corresponding to the rotational position and the fixed slit plate 3 transmit or block the light by relative rotation, and the light receiving element 4 detects the presence or absence of the light. It is output as a binary absolute position detection signal.

[0004] In such an absolute type encoder, if the amount of light from the light emitting element 1 ₁ to 1 ₃ is changed to deteriorate the accuracy of the position detection signal, will produce an error in position detection.

[0005] Therefore, the absolute type encoder, the light projecting current or gain of the light receiving element 4 of the light-emitting element 1 ₁ to 1 ₃ in accordance with the change by monitoring the change in the amount of light from the light emitting element 1 ₁ to 1 ₃ or varied, or constitute performs processing such as changing the threshold value of the waveform shaping circuit (not shown) so as to compensate for the change in light quantity of the light emitting element 1 ₁ to 1 _3.

[0006] Figure 7 is a rotary slit plate 2 ₀ in the conventional example for monitoring the change in light quantity of such light-emitting elements 1 ₁ to 1 ₃
And is a front view showing a configuration of a stationary slit plate 3 _0.

[0007] rotary slit plate 2 ₀ having an optical slit that corresponds to the rotational position, to monitor the three light amount of the light-emitting element 1 ₁ to 1 _3, transmits light three light amount monitor track 51 _to 5 ₃ are formed concentrically around the entire circumference, whereas, in the stationary slit plate 3 _0, the light-emitting elements 1 ₁
In each irradiation region ₆₁ through ₃ shown in ~ 1 ₃ circular,
And has a position detecting slit 7-15 corresponding to concentric position detecting tracks composed of optical slits, light quantity monitor slits _{161-164 3} corresponding to the light amount monitor track 5 ₁ to 5 ₃ are formed cage, the light from the light emitting element 1 ₁ to 1 ₃ through the light quantity monitor truck 5 ₁ to 5 ₃ and the light quantity monitor slits _{161-164 3,} so as to respectively received by the light receiving element for monitor (not shown) ing.

[0008]

[SUMMARY OF THE INVENTION However, the rotational slit plate 2 _0, apart from the rotational position detecting tracks composed of optical slits, in the conventional example in which over the light amount monitor track 5 ₁ to 5 ₃ to the entire circumference , inhibits miniaturization of the encoder becomes the outer shape of the rotary slit plate 2 ₀ is large, or, if not increase the external shape of the rotary slit plate 2 _0, obtained correspondingly, forced to reduce the opening area of the optical slit Therefore, the output of the position detection signal is reduced and the position detection accuracy is reduced.

The present invention has been made in view of the above-mentioned points, and it is an object of the present invention to provide a light emitting element without increasing the outer shape of the rotary slit plate and without sacrificing the output of the rotary position detection signal. It is an object of the present invention to provide an absolute encoder capable of monitoring a change in light quantity.

[0010]

In order to achieve the above-mentioned object, the present invention is constructed as follows.

That is, the present invention is a rotary slit plate having a track for detecting a rotary position which is composed of an optical slit,
A light-emitting element that emits light, a fixed slit plate having a slit for rotational position detection corresponding to the track for rotational position detection and a slit for monitoring the amount of light of the light-emitting element, and a fixed slit plate arranged corresponding to the slit for rotational position detection. In the optical absolute type encoder including a light receiving element for detecting a rotational position and a light receiving element for light amount monitoring arranged corresponding to the light amount monitoring slit, the light amount monitoring slit of the fixed slit plate is The slit plate is formed along the circumferential direction so as to correspond to the rotational position detection track, and the rotational position detection track is also used as the light amount monitor track.

[0012]

According to the above construction, it is not necessary to form a light quantity monitor track separately from the rotational position detection track.
As a result, the outer shape of the rotary slit plate is not increased, and the output of the light detection signal corresponding to the rotational position is not sacrificed.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a front view showing the construction of a rotary slit plate 2 ₁ and a fixed slit plate 3 ₁ according to an embodiment of the present invention. The same reference numerals are given to the portions corresponding to the conventional example of FIG. Attach.

The entire structure of this absolute encoder is the same as that shown in FIG. 6, and the description thereof is omitted.

[0016] In this embodiment, without increasing the outer shape of the rotary slit plate 2 _1, moreover, without sacrificing the output of the position detection signal corresponding to the rotational position, the light-emitting element 1
To be able to monitor changes in light amount of ₁ to 1 _3, it is constructed as follows.

That is, the rotary slit plate 2 ₁ has a structure shown in FIG.
Conventional light amount monitoring truck 5 ₁ to 5 ₃ are not formed, such as, three light-emitting elements 1 ₁ to 1 each irradiation region 6 of the _third
1 to 6 _3, the rotational position detecting track 17 composed of an optical slit that corresponds to the relatively small lower bit pitch
19 are arranged respectively.

Meanwhile, the fixed slit plate 3 _1, as in the conventional example of FIG. 7, the rotational position detecting slit 7-15 corresponding to the rotational position detecting track of the rotary slit plate 2 ₁ is formed Further, in this embodiment, the circumferences of the irradiation regions 6 _{1 to} 6 ₃ of the _three light emitting elements 1 ₁ to ₁₃ are circled corresponding to the rotational position detecting tracks 17 to 19 of the rotary slit plate 2 _1. Along the direction, slits for light quantity monitoring 20 _{1 to} 20 ₃
Are formed respectively.

[0019] In this embodiment, the circumferential width of each of the light amount monitoring slits 20 ₁ to 20 _3, the corresponding pitch of the optical slits in each rotational position detecting track 17 to 19 1.
5 times and it is, thus, in the irradiation region 6 _3, in order to form a light intensity monitoring slit 20 ₃ forms a position of the rotational position detecting slit 13 is shifted in the circumferential direction.

A light quantity monitor light receiving element (not shown) is arranged corresponding to each of the light quantity monitor slits 20 _{1 to} 20 ₃ .

With this structure, the rotational position detecting tracks 17 to 19 are also used as the light quantity monitoring tracks.

Therefore, it is not necessary to provide the light quantity monitor tracks 5 ₁ , 5 ₂ , 5 ₃ on the rotary slit plate 2 ₀ over the entire circumference as in the conventional example, whereby the outer shape of the rotary slit plate 2 ₁ can be improved. The size of the encoder can be reduced without increasing the size.

In this embodiment, the circumferential widths of the light quantity monitor slits 20 _{1 to} 20 ₃ shown in FIG. 2B are the same as the rotational position detecting tracks 17 to 19 shown in FIG. 2A.
Of which is 1.5 times the pitch P of the optical slit, therefore, the rotation of the rotary slit plate 2 _1, monitor signal obtained by the light quantity monitoring light receiving element, pulsates as shown in FIG. (C) It will be. Therefore, in this embodiment, the output of the light receiving element for light quantity monitor is smoothed by the smoothing capacitor.

In the above-described embodiment, the circumferential widths of the light quantity monitor slits 20 _{1 to} 20 ₃ are set to 1.5 times the pitch P of the optical slits of the rotational position detecting tracks 17 to 19, but As another embodiment of the invention, the circumferential widths of the light quantity monitor slits 20 _{1 to} 20 ₃ may be an integral multiple of the pitch P of the optical slits of the rotational position detection tracks 17 to 19.

FIG. 3 shows the light quantity monitor slits 20 ₁ to 20 2.
0 ₃ a circumferential width, the rotational position detecting track 17
2 when the pitch P of the 19 optical slits is doubled
It is a figure corresponding to. As shown in this figure (C),
The monitor signal obtained by the monitor light receiving element does not pulsate, and stable light amount compensation is possible.

FIG. 4 is a view corresponding to FIG. 1 of another embodiment of the present invention.

[0027] In this embodiment, the rotary slit plate 2 _1, three corresponding to one of the irradiation regions ₆₁ of the light emitting element 1 ₁ to 1 ₃ of the irradiation region ₆₁ through _3, the pitch A rotational position detecting track 18 composed of an optical slit corresponding to a lower bit having a relatively small number is arranged. The fixed slit plate 3 ₂ is provided with its irradiation area 6 ₁ in correspondence with the rotational position detecting track 18. A slit 21 for light quantity monitor is formed along the circumferential direction, and a light receiving element for light quantity monitor is arranged corresponding to the slit 21 for light quantity monitor. Further, the fixed slit plate 3 ₂ is attached to the rotary slit plate 2 ₁
The rotational position detecting slits 7 to 15 are formed corresponding to the rotational position detecting tracks.

[0028] In this embodiment, instead of monitoring all the light amount of each light-emitting element 1 ₁ to 1 _3, one light emitting element 1 ₁
The light intensity of each of the light emitting elements 1 ₁ to
It is to change the threshold value of 1 ₃ position detection signal.

That is, FIG. 5 is a diagram showing such a threshold value setting circuit. In FIG. 5, reference numeral 22 is a light quantity monitor light receiving element arranged corresponding to the light quantity monitor slit 21, and REF1, REF2 is the light emitting elements 1 ₂ and 1 ₃
Is the threshold voltage of the position detection signal corresponding to
3 is a threshold voltage of the position detection signal corresponding to the light emitting element 1 _1. The level of REF1 and REF2 can be adjusted by the variable resistor VR.
In addition, R is a resistor and C is a capacitor.

[0030] since the compensation thus one light emitting device 1 ₁ of all of the light emitting element by monitoring the amount of light 1 ₁ to 1 ₃ of the light intensity, can be configured is simplified reduced cost.

[0031]

As described above, according to the present invention, the rotation position detecting track is also used as the light amount monitor track of the light emitting element.
Since it is not necessary to separately provide a light quantity monitor track, it is possible to reduce the size of the rotary slit plate and thus the encoder.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a rotary slit plate and a fixed slit plate according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a monitor signal in the embodiment of FIG.

FIG. 3 is an explanatory diagram corresponding to FIG. 2 of another embodiment of the present invention.

FIG. 4 is a configuration diagram corresponding to FIG. 1 of still another embodiment of the present invention.

5 is a diagram showing a threshold value setting circuit of the embodiment of FIG.

FIG. 6 is a schematic configuration diagram of an absolute encoder.

FIG. 7 is a configuration diagram of a rotary slit plate and a fixed slit plate of a conventional example.

[Explanation of symbols]

1 ₁ to 1 ₃ the light emitting element 2, 2 _0, 2 ₁ rotary slit plate 3,3 _0, 3 _1, 3 ₂ fixed slit plate 17-19 rotational position detecting track 20 ₁ to 20 _3, 21 light amount monitor track

Claims (2)

[Claims] 1. A rotary slit plate having a rotational position detection track made of an optical slit, a light emitting element for irradiating light, a rotational position detection slit corresponding to the rotational position detection track, and a light amount monitor of the light emitting element. A fixed slit plate having a slit for use in rotation, a light receiving element for rotational position detection arranged corresponding to the slit for rotational position detection, and a light amount monitoring light receiving element arranged corresponding to the light amount monitoring slit. In the optical absolute type encoder, a slit for light amount monitoring of the fixed slit plate is formed along the circumferential direction corresponding to a track for detecting the rotational position of the rotary slit plate, and the track for detecting the rotational position is a light amount. An absolute encoder that is also used as a monitor truck. 2. The circumferential width of the light quantity monitor slit is set to an integral multiple of the pitch of the optical slit of the rotation position detection track which is also used as the light quantity monitor track. Absolute encoder.