JPH0734331Y2 - Rotary encoder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a rotary encoder used for detecting the amount of rotation of a rotary shaft or the like in a machine tool, for example.

[Prior Art] Conventionally, various rotary encoders have been used to detect a rotation amount of a rotary shaft in a measurement target such as a machine tool.

The rotary encoder has a rotating part mounted on the rotating shaft of the measurement target and a fixing part fixed to the target body,
The relative rotation amount between the rotating portion and the fixed portion is optically or magnetically detected by the detecting portion to measure the rotation angle of the rotating shaft and the like.

Generally, the higher the accuracy of the rotary encoder, the more precise the mounting is required. If there is a mounting error between the rotary shaft to be measured and the rotary encoder, the bearing that supports the rotary portion of the rotary encoder may be damaged. Therefore, when mounting the rotary encoder, the rotary shaft to be measured and the rotary part of the rotary encoder are connected using a flexible coupling to prevent the bearing from being damaged. However, this method cannot avoid errors inherent to the flexible coupling due to backlash, transmission errors due to deviation of the center position, and the like, and therefore there is a problem in that high accuracy of measurement can be prevented.

As one method for solving this problem, Japanese Patent Laid-Open No. 58-17
As disclosed in Japanese Patent No. 1617, a method of fixing a rotating portion and a fixed portion of a rotary encoder with a joint having torsional steel has been considered.

[Problems to be Solved by the Invention] According to the conventional rotary encoder in which the rotating portion and the fixed portion are fixed by a rigid joint, an error or back error caused by relative twist between the rotating portion and the fixed portion is generated. It is possible to prevent rush. However, in the above-described conventional technique, no consideration is given to an error due to distortion or eccentricity between the rotating portion and the fixed portion, and the conventional rotary encoder causes a measurement error due to an eccentricity error or the like. Could not be prevented.

[Object of the Invention] It is an object of the present invention to provide a rotary encoder that does not cause a measurement error due to an eccentricity error or the like even if strain or eccentricity is applied between a fixed part and a rotating part.

[Means for Solving the Problems] A rotary encoder according to the present invention comprises a rotary part mounted on a rotary shaft of a measurement target, a fixed part fixed to a main body of the measurement target, and a relative position between the rotary part and the fixed part. A plurality of sets of detection units that output signals according to the target rotation amount, and the rotation unit has a degree of freedom of movement in the radial direction with respect to the rotation unit.

[Operation] When an error occurs in the radial direction between the rotary unit and the fixed unit, the outputs of the plurality of sets of detection units are averaged, and the reading error is reduced as much as possible.

[Embodiment] The first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

The rotary encoder 1 has a structure in which a rotary unit 5 including a hollow shaft 3 and an angle scale plate 4 is rotatably provided inside a cylindrical housing 2 that is a fixed unit. First, the hollow shaft 3 is externally inserted and fixed to a rotary shaft (not shown) to be measured, and a flange 3a is provided on the central outer peripheral surface thereof. An annular angle graduation plate 4 made of a glass plate having marking lines at regular intervals is fixed to the flange 3a. Next, cover plates 6 and 7 each having a hole through which the hollow shaft 3 is inserted are fixed to both front and rear end surfaces of the housing 2 that houses the rotating portion 5. Further, the housing 2 is provided with a flange 2a so that it can be fixed to the main body to be measured. On the inner peripheral surface of the center of the housing 2, a base portion 9 having a projecting step portion 8 is circumferentially formed, and two sets of detection portions 10 and 10 for detecting the rotation of the rotating portion 5 are formed on the base portion 9. It is provided. That is, the base 9 is provided with a light source 11, a collimating lens 12, and a scanning plate 13 made of a glass plate having engraved lines at the same intervals as the angle scale plate 4, and the angle scale plate 4 is further sandwiched. At a position facing the scanning plate 13, a photoelectric conversion element 15 is attached to each of the detection units on a substrate 14 fixed to the housing 2 side. Also, as shown in FIG.
The detectors 10 and 10 at the locations are arranged at positions such that the central angle α extending about the rotation center of the hollow shaft 3 is 180 °. Next, an annular fixing plate 16 is bolted to the protruding portion 8 of the base portion 9.
It is attached with 17. A thrust bearing 18 is provided between the fixed plate 16 and the flange 3a of the hollow shaft 3, and the fixed plate 16 is mounted on the hollow shaft 3 side by a double nut 19 screwed into the hollow shaft 3. There is. That is,
The hollow shaft 3 is held with respect to the housing 2 in the thrust direction, but since there is a slight gap between the projecting portion 8 and the flange 3a, the hollow shaft 3 can be freely moved within a certain range in the radial direction. Has been done.

Next, the operation of the above configuration will be described. First, the flange 2a of the housing 2 is fixed to the main body to be measured, and the hollow shaft 3 is fixed to the rotating shaft to be measured. When the rotary shaft 3 rotates, the angle scale plate 4 on the rotary unit 5 side relatively rotates with respect to the scanning plate 13 on the fixed unit side, so that the moire fringes generated by the score lines move in the radial direction. The light from the light source 11 is collimated by the collimating lens 12 and reaches the photoelectric conversion element 15 as pulsed light through the moire fringes. Therefore, from the two-phase signal output from each element 15, the rotation angle of the rotating unit 5 is increased. , The direction of rotation can be detected.

Now, in this embodiment, since the rotating portion 5 has the freedom of movement in the radial direction with respect to the housing 2 in order to prevent the occurrence of an error due to the distortion between the rotating portion 5 and the housing 2, both portions 5 When a radial force is applied between the two, the center of the rotating portion 5 deviates from the center of the housing 2 (eccentricity e). As shown in FIG. 2, when the distance from the center to the detection unit 10 where the photoelectric conversion element 15 is located is R, the eccentricity error δ is generally represented by δ = e / Rsinα. Further, in the present embodiment, since α = 180 °, δ = 0, and by averaging the signals from the two sets of photoelectric conversion elements 15 and 15, it is possible to obtain the correct rotation amount with the eccentricity error removed.

Next, a second embodiment of the present invention will be described with reference to FIGS.

The rotary encoder 21 has a structure in which a rotary portion 25 including a hollow shaft 23 and an angle scale plate 24 is rotatably provided inside a cylindrical housing 22 that is a fixed portion. First, the hollow shaft 23 is externally inserted and fixed to a rotary shaft of a measurement object (not shown), and an angle scale plate 24 similar to that of the first embodiment is fixed to the flange 23a. Next, on both front and rear end surfaces of the housing 22 that houses the rotating portion 25,
Lid plates 26 and 27 each having a hole through which the hollow shaft 23 is inserted are fixed. Further, two mounting portions 28, 28 are formed on the inner peripheral surface of the housing 22 at intervals of a central angle of about 100 °. On the front end surface and the rear end surface of this mounting portion 28,
The elongated rectangular leaf springs 29 are fixed by bolts 30, respectively. The leaf spring 29 is substantially perpendicular to the central axis of the rotating portion 25, and its tip is fixed to the rear end surface of the annular scanning body 33 by a leaf spring holder 31 and a bolt 32. The scanning body 33 is a member for externally inserting the hollow shaft 23 inside the housing 22, that is, the scanning body 33 is movable in the axial direction (thrust direction) within the housing 22 by two to four leaf springs 29. Supported by.
A thrust bearing 35 is provided between the annular receiving plate 34 provided on the scanning body 33 and the flange 23a of the hollow shaft 23, and the hollow shaft 23 is held in the thrust direction with respect to the housing 22 side. However, it is configured so that it can move freely within a certain range in the radial direction. Then, the hollow shaft 23 inside the housing 22 is externally inserted, and the flange 22a
A coil spring is provided between the cover plate 27 on the side and the rear end surface of the scanning body 33.
36 is interposed and biases the scanning body 33 forward. Next, the scanning body 33 is provided with a detecting section 37 including two sets of photodetectors, as in the first embodiment. That is, the detection unit 37 is a light source 38 and a collimating lens.
39, a scanning plate 40, a substrate 41, and a photoelectric conversion element 42, and the angle scale plate 24 is positioned between the scanning plate 40 and the photoelectric conversion element 42. In addition, the detection unit 37 is
Similar to the embodiment, two sets are provided so as to form a central angle of 180 ° with respect to the scanning body 33.

According to this embodiment, it is possible to obtain a measurement result in which the eccentricity error in the radial direction is removed by exhibiting substantially the same operation and effect as the first embodiment. Besides, the mounting error in the thrust direction is absorbed by the scanning body 33 being supported by the leaf spring 29 having the freedom of movement only in the thrust direction.

In each of the above embodiments, as a method of detecting the relative amount of rotation between the fixed portion and the rotating portion, an optical means utilizing moire fringes has been described as an example. Of course, the rotation amount detection method may be an optical method that does not utilize moire fringes other than this, or may be a magnetic method or the like.

Further, in each of the above-described embodiments, the number of detecting units 10 and 37 is two, but the number may be more than this. Also, two detectors
Since 10,37 are arranged so as to form a central angle of 180 °, an error due to eccentricity can be removed, and the structure is simple and excellent. However, this angle is not necessarily 180 °. Post-processing becomes a little complicated, but 180 °
Even if each detection unit is arranged at a central angle other than, the eccentricity error δ can be made zero by appropriately correcting and processing the data obtained from each detection unit.

[Advantages of the Invention] According to the present invention, since the rotating portion is movable in the radial direction with respect to the fixed portion and the rotation amount is detected by a plurality of sets of detecting portions, the strain applied to the rotary encoder is It is possible to suppress errors caused by eccentricity and eccentricity, and it is possible to realize highly accurate measurement.

[Brief description of drawings]

FIG. 1 is a view showing a first embodiment of the present invention, which is a sectional view taken along the line AB of FIG. 2, FIG. 2 is a front view of the same embodiment, and FIG. 4 is a front view showing a second embodiment,
FIG. 5 is a sectional view taken along the line B-A in FIG. 3, and FIG. 5 is a sectional view taken along the line C-D in FIG. 1,21 …… Rotary encoder, 2,22 …… Housing as fixed part, 5,25 …… Rotating part, 10,37 …… Detecting part.

Claims (1)

[Scope of utility model registration request] 1. A rotary unit mounted on a rotary shaft to be measured,
It comprises a fixed part fixed to the main body to be measured, and a plurality of sets of detection parts for outputting a signal according to the relative rotation amount of the rotation part and the fixed part, wherein the rotation part is the rotation part. A rotary encoder characterized by having freedom of movement in the radial direction with respect to.