JPS6287814A - Rotary encoder - Google Patents

Abstract

PURPOSE:To enhance measuring accuracy, by providing a deflection width detection means for detecting the deflection width of a cord wheel and a control means controlling the output value of a light receiving element so as to make the same constant. CONSTITUTION:A deflection width sensor 4 using a linear image sensor is arranged to the circumference of a cord wheel 21 at the position corresponding to a light emitting element 11 as a deflection width detection means for detecting the deflection width of the cord wheel 21. This sensor 4 detects the position of the circumferential surface of the wheel 21. The signal corresponding to said circumferential surface is obtained and the deflection width of the wheel is detected. The output of this sensor 4 is inputted to a converter circuit 5 being a control means and the brightness of the element 11 is regulated correspondingly to said output. That is, the brightness of the element 11 is made large as the circumferential surface of the wheel is separated from a phase plate 32 to control the output amplitude of the light receiving element 31 so as to make the same large. By this method, the output level of the element 31 comes to an almost constant value to produce highly accurate signal output.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a rotary encoder, and more particularly, to a rotary encoder used for measuring the rotation angle and rotation speed of objects in robots, machine tools, and measuring instruments. It is.

[Background Art] Generally, this type of rotary encoder, as shown in FIG.
and a light receiving block including a light receiving element 31. The light emitting block 10 is equipped with a light emitting element 11 , the rotating block 20 is provided with a code wheel 21 that rotates together with the rotating shaft 22 , and the light receiving block 30 is equipped with a light emitting element 1 .
1 and a plurality of light receiving elements 31 facing the code wheel 2
1 and a phase plate 32 interposed between the light receiving element 31 and the light receiving element 31. As shown in FIG. 5, the code wheel 21 has a large number of slits 23 periodically formed in the circumferential direction, and when the code wheel 21 rotates together with the rotating shaft 22, the light receiving element 31 By detecting the number of passages through the slit 23, the rotation angle and the like can be detected.

Here, if the code wheel 21 and the phase plate 32 are not parallel, the distance l between the code wheel 21 and the phase plate 32 will change as the code wheel 21 rotates. When the distance l between the code wheel 21 and the phase plate 32 changes, as shown in FIG. 8(a), the larger the distance @12, the smaller the amplitude of the output of the light receiving element 31. When is rotating, w
As shown in FIG. S8 (b), the output level of the light receiving element 31 changes with the passage of time. If the output amplitude of the light-receiving element 31 is not constant in this way, the output change of the light-receiving element 31 will not be at a constant period when the code wheel 21 is rotating at a constant speed, making it impossible to perform accurate measurements. A problem arises.

[Object of the Invention] The present invention has been made in view of the above points, and its main purpose is to improve the output of the light receiving element even when the code wheel is tilted in the axial direction of the rotation axis. The aim is to improve measurement accuracy by keeping the amplitude constant.

[Disclosure 1 of the Invention As shown in FIGS. 5 to 7, a rotary encoder basically includes a light projection block 10 and a rotation block 20.
and a light receiving block 30.

The light projection block 10 is composed of a base 12 fixed at a fixed position in the casing 1, a light emitting element 11 such as an infrared light emitting diode fixed to the base 12, and a bearing 13 mounted in the center of the base 12. Ru. A bearing 14 is also mounted on the casing 1 coaxially with the bearing 13.

As shown in FIG. 5, the rotating block 20 has a code wheel 21 mounted on a rotating shaft 22, and the code wheel 21 is attached to a holding bush 24 press-fitted into the rotating shaft 22.
and an end pusher 25 disposed opposite to the holding bush 24 and fixed to the rotating shaft 22.

The code wheel 21 is formed into a thin disk shape, and a large number of slits 23 are bored at equal intervals along the circumferential direction on its outer periphery, and a reference position is set closer to the center than the slits 23. A reference slit 26 is bored. The slit 23 and the reference slit 26 are the light emitting element 1
1, and the light emitted from the light emitting element 11 is transmitted through the slit 23 and the reference slit 26. Rotation @22 is light projection block 1
Bearings 13.14 provided in 0 and casing 1
Supported by

The light receiving block 30 is disposed on the opposite side of the light emitting block 10 via the code wheel 21, and the WS
As shown in Figure 6, the slit 23 of the code wheel 21
Three light receiving elements 31 A#*rl#I+L that receive the light transmitted through the reference slit 26 and the reference slit 26 and convert it into an electrical signal.
Ml−$J[ff, l−! 14'=51 A phase plate 32 in which correction slits 34 are formed at positions corresponding to the respective children 31, and a phase plate 32 and a substrate 3.
3 and a light guide 35 that guides the light transmitted through the phase plate 32 to each light receiving element 31. A pair of correction slits 34 are provided on the left and right at positions corresponding to the slits 23 of the code wheel 21, and one correction slit 34 is provided at a position corresponding to the reference slit 26.

Each correction slit 34 is formed by a group of small slits. Each correction slit 34 is provided in the light guide 35.
Three guide holes 36 are formed correspondingly. This guide hole 36 allows the light transmitted through each correction slit 34 to reach the light receiving element 31 without interfering with each other. 7-ray X plate 32, board 33 and light guide 3
5 are integrally coupled with each other to form a light receiving block 30.

In the rotary encoder constructed as described above, if the code wheel 21 is not attached at right angles to the rotating shaft 22, the output amplitude of the light receiving element 31 changes as described above, and the light receiving element 31 changes as described above. When the output of the code wheel 21 is shaped into a rectangular wave by the waveform shaping circuit 3, a highly accurate signal output cannot be obtained. It is necessary to correct the output level of the light receiving element 31 in accordance with the width. A configuration for performing such correction will be explained in the following embodiments.

(Example 1) As shown in FIG. 1, as an amplitude detection means for detecting the amplitude of the amplitude of the code wheel 21, an amplitude sensor 4 using a linear image sensor such as a COD is connected to the light emitting element 11. They are arranged around the code wheel 21 at corresponding positions. This swing width sensor 4 has a code wheel 21
The position of the circumferential surface of the rotary shaft 22 is detected, and in the case of a COD, it is arranged along the axial direction of the rotating shaft 22. As a result, a signal corresponding to the position of the circumferential surface of the code wheel 21 is obtained, and the amplitude of the swing of the code wheel 21 is detected. The output of the swing width sensor 4 is input to a conversion circuit 5 which is a control means, and the brightness of the light emitting cord 11 is adjusted in accordance with the output of the swing width sensor 4. In other words, the further the circumferential surface of the code wheel 21 is away from the phase plate 32, the more the luminance of the light emitting element 11 is reduced, and the output amplitude of the light receiving element 31 is controlled to become more extreme. Thereby, the output level of the light receiving element 31 becomes a substantially constant value, and a highly accurate signal output can be obtained.

(Example 2) In this example, as shown in FIG.
An example is shown in which the vibration amplitude detection means of No. 1 is constituted by a Z-phase optical part 6 and a synchronization circuit 7, and the control means is constituted by a memory circuit 8.
That is, when the code wheel 21 is attached to the rotating shaft 22, the swing width of the code wheel 21 is a constant value, so after assembling the rotary encoder,
Once you measure the relationship between the rotation angle of the code wheel 21 and the amount of light received by the light receiving element 31, you can determine how much the amount of light received by the light receiving element 31 changes depending on the rotation angle from the reference position. I understand. Therefore, the relationship between the rotation angle of the code wheel 21 and the brightness of the light emitting element 11 corresponding to the rotation angle is stored in advance in the memory circuit 8, and the rotation i angle of the code wheel 21 is passed to the memory circuit 8, and If the light emitting element 11 is caused to emit light by the output obtained in accordance with the rotation angle,
The output amplitude of the light receiving element 31 becomes a constant value.

The reference position of the code wheel 21 is set at the light receiving element 31 (that is, the Z phase light section 6) corresponding to the reference slit 26 described above.
), and at this position, the synchronous circuit 7 is reset, and the output signal of the output of the light receiving element 31 corresponding to the slit 23 is waveform-shaped by the waveform shaping circuit 3. By inputting , the rotation angle of the code wheel 21 from the reference position is detected. In this way, by giving the rotation angle of the code wheel 21 to the memory circuit 8, the memory circuit 8
Then, the light emitting element 11 is caused to emit light with a brightness corresponding to the rotation angle.

(Example 3) In the above example, the brightness of the light emitting cord 11 was adjusted in accordance with the swing width of the code wheel 21, but in this example,
As shown in FIG. 3, the amplitude of the input signal to the waveform shaping circuit 3 is kept constant by adjusting the amplification factor of the amplifier circuit 9 that amplifies the output of the light receiving element 31 in accordance with the amplitude of the swing of the code wheel 21. It is designed to be a value. That is, as in the first embodiment, the vibration amplitude of the code wheel 21 is detected by the vibration amplitude sensor 4, and the conversion circuit 5 sets the amplification circuit 9 so that the amplification factor corresponds to the vibration amplitude. As the amplifier circuit 9, for example, a voltage-controlled amplifier circuit whose amplification factor can be varied depending on the magnitude of the control voltage is used. In this way, since the amplitude of the input signal to the waveform shaping circuit 3 is kept at a constant level, a highly accurate output signal can be obtained in the same way as when changing the brightness of the light emitting element 11. Here, the amplification factor of the amplifier circuit 9 is set to increase as the code wheel 21 is farther away from the seven-point plate 32.

(Embodiment 4) Similar to Embodiment 3, this embodiment changes the amplification factor of the amplifier circuit 9 that amplifies the output of the light receiving element 31 in accordance with the amplitude of the amplitude of the code wheel 21, and detects the amplitude of the amplitude. means,
The control means is constructed in the same manner as in the second embodiment. That is, the amplification factor of the amplifier circuit 9 is set in advance in accordance with the rotation angle of the code wheel 21 from the reference position of the code wheel 21, and this relationship is stored in the storage circuit 8.
The synchronization circuit 7 detects the rotation angle based on the output of the soai optical unit 6 and the output of the waveform shaping circuit 3, passes the rotation angle to the storage circuit 8, and sets the amplification factor of the amplifier circuit 9 in accordance with the rotation angle. It is set. In this way, as in the third embodiment, the input signal level to the waveform shaping circuit 3 becomes a constant value, and a highly accurate signal output is obtained.

[Effects of the Invention] As described above, the present invention includes a vibration amplitude detection means for detecting the vibration amount of the code wheel in the axial direction of the rotating shaft, and an output value of the light receiving element is set to a constant value based on the output of the vibration amplitude detection means. Since a control means is provided to control the light emitting element or the light receiving element so that the output amplitude of the light receiving element remains constant even when the code wheel is tilted in the axial direction of the rotation axis, There is an advantage that the element or light-receiving element is controlled, resulting in improved measurement accuracy.

[BRIEF DESCRIPTION OF THE DRAWINGS] tA1 is a schematic configuration diagram showing the first embodiment of the present invention, FIG. 2 is a schematic configuration diagram showing the second embodiment same as the above, and FIG. 3 is a schematic configuration diagram showing the third embodiment same as the above. 4 is a schematic configuration diagram showing Example 4 of the same as above, FIG. 5 is an exploded perspective view showing a recirculating block used in the above, FIG. 6 is an exploded perspective view showing a light receiving block used in the same, FIG. 7 is a schematic cross-sectional view of the main parts of the same as above, and FIG. 8 is an explanatory diagram of the operation showing the conventional problem. 3 is a waveform shaping circuit, 4 is an amplitude sensor, 5 is a conversion circuit,
6 is a Z-phase light receiving section, 7 is a synchronous circuit, 8 is a memory circuit, 9 is an amplifier circuit, 11 is a light emitting element, 21 is a code wheel, 22
3 is a rotating shaft, 31 is a light receiving element, and 32 is a 7-Aze plate.・Princess 2, Figure 3, Figure 7 (b)

Claims (1)

[Claims] (1) A code wheel that is formed in a disc shape and co-rotates with a rotating shaft in a direction substantially perpendicular to the surface of the code wheel, and has many slits periodically formed in the circumferential direction; A light emitting element that emits light toward the slit, a plurality of light receiving elements that receive light transmitted through the slit of the code wheel and converting it into an electrical signal, and each light receiving element that is interposed between the code wheel and the light receiving element. In a rotary encoder equipped with a phase plate in which correction slits are respectively formed corresponding to 1. A rotary encoder comprising a control means for controlling a light emitting element or a light receiving element so that an output value of the light receiving element becomes a constant value.