JPH0216412A - Rotary encoder - Google Patents

Abstract

PURPOSE:To reduce a cumulative pitch error by unitizing a code plate, a detector, a hollow rotary shaft, a bearing, and a support member and providing a means which fixes the core of the hollow rotary shaft to a shaft to be measured in an adjustable state. CONSTITUTION:The hollow rotary shaft 1 is fitted externally onto the shaft 2 to be measured. The code plate 4 which has regular slits is fixed to a flange 3 provided to the outer periphery of the hollow rotary shaft 1. The hollow rotary shaft 1 is supported rotatably on an annular support member 7 through a couple of ball bearings 6 and the support member 7 is provided with a detector 8 which detects the rotational position of the code plate 4 to detect a Fraunhofer diffraction image generated by the slits of the code plate 4 with laser light. Further, the fixing means 11 consisting of chevron shaped sleeves 14 and 15, wedgelike sleeves 12a and 12b, and a clamping bolt 13 is provided between the hollow rotary shaft 1 and the shaft 2 to be measured. While the shaft 2 to be measured is turned, the eccentricity of the hollow rotary shaft 1 is found from measurement surfaces 10a and 10b and adjusted with the bolt 13. Consequently, the cumulative pitch error is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rotary encoder, and more particularly to a rotary encoder that can be easily attached to a shaft to be measured.

Conventional technology Conventionally, in high-resolution rotary encoders, the fourth
As shown in the figure, the hollow shaft 42 to which the code plate 41 is fixed is fitted onto the shaft to be measured 43 with a gap, and the hollow shaft 42 is fitted onto the contact surface 43a formed on the shaft to be measured 43 in the axial direction. One end is engaged and positioned, and the other end of the hollow shaft 42 is pushed through a pressing plate 46 by a port 45 screwed onto a plurality of positions in the circumferential direction of a fixing ring 44 which is screwed and fixed to the end of the shaft 43 to be measured. It is fixed by pressing the hollow shaft 42 in the radial direction.
The tips of screws 47, which are screwed through multiple locations in the circumferential direction in the radial direction, are brought into contact with the outer peripheral surface of the shaft to be measured 43, and the screws are screwed so that the axes of the code plate 41 and the shaft to be measured 43 are aligned. It is configured so that it can be adjusted with 47. Further, a detector 4 for detecting the rotational position of the code plate 41 is attached to the fixed side via a bracket 49 so that its position can be adjusted.

On the other hand, in a rotary encoder with relatively low resolution, as shown in FIG. 54 is equipped with a detector 55 for detecting the rotational position of the code plate 51, and when installed, the hollow rotating shaft 52 is attached to the shaft to be measured 56.
The fixing nut 5 is fitted and screwed onto the end of the shaft 56 to be measured.
At 7, it is fastened and fixed to the contact surface 56a.

In addition, in order to prevent the support member 54 from rotating, the outer circumference of the annular leaf spring 58 perpendicular to the rotation axis is fixed to the stationary side with a pin 59a, and the inner circumference is attached to the support member 54. (pol) 59b.

Problem to be Solved by the Invention By the way, in the mounting configuration shown in FIG. 4, the code plate 41 is directly attached to the shaft 43 to be measured, so that the code plate 41 can be placed in a state with less eccentricity with respect to the shaft 43 to be measured. However, the assembly of the rotary encoder itself and its installation must be done at the same time at the rotary encoder installation site, which reduces the cumulative pitch error and makes it compatible with high-resolution rotary encoders. There is a problem that assembly and adjustment of the low-return encoder, such as output waveform adjustment, is required during installation work, which is very time-consuming.

On the other hand, in the mounting configuration shown in FIG. 5, since the rotary encoder is unitized, the mounting work is easy. Eccentricity between the measurement axes 56 is unavoidable, resulting in a large cumulative pitch error, which poses a problem in that it cannot be applied to a high-resolution rotary encoder.

In addition, since the support member 54 is fixed to the inner circumference of an annular temporary spring 58 whose outer circumference is fixed to the fixed side, the rigidity of this plate spring 58 exerts a large restraint force, and the support member 54 and the measured object are There is also the problem that the eccentricity of the shaft 56 causes large load fluctuations to occur in the bearing 53 during rotation, causing uneven rotation.

In FIG. 5, if the inner diameter of the hollow rotating shaft 52 is increased, a bearing 53 with a larger diameter is required, and the rotation accuracy of the code plate 51 is reduced accordingly.
It has not been considered to interpose an axial center adjusting means between the shaft 56 to be measured and the hollow rotary shaft 52, since there is a possibility that a detection error may occur due to a large variation in the clearance between the shaft 56 and the shaft 52.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, it is an object of the present invention to provide a low-resolution encoder that is easy to install, has a small cumulative pitch error, and is capable of high-resolution position detection.

Means for Solving the Problems In order to achieve the above object, the present invention includes a code plate, a hollow rotating shaft to which the code plate is fixed, and a hollow rotating shaft which is rotatably supported via a bearing, and the code plate is rotated. A fixing means that is interposed between a support member to which a detector for detecting a position is attached, an inner circumferential surface of the hollow rotating shaft and the shaft to be measured, and fixes the hollow rotating shaft to the shaft to be measured so as to be able to adjust the axial center. and a measuring surface formed on the outer circumferential surface of the hollow rotating shaft.A particularly preferable method is characterized in that the code plate is irradiated with a laser beam from a laser light source, and the code plate is irradiated with a laser beam by slits regularly formed in the code plate. A laser type detector is used in which light and dark fringes of the resulting Fraunhofer diffraction image are irradiated onto a photodetecting element through a slit. Preferably, the measurement surfaces are formed on the protrusions at both ends of the hollow rotating shaft, and the clamping means comprises a pair of wedge-shaped sleeves and chevron-shaped sleeves that are drawn together by a spring mechanism.

Further, a coupling means is used which fixes the support member only in the rotational direction around the axis of the hollow rotating shaft and couples it to the fixed side so that it can float in other directions. This coupling means may include an engagement pin protruding radially from the support member and a fixed locking member that engages the engagement pin in the circumferential direction;
A flexible wire member arranged tangentially to the circumference centered on the axis of a hollow rotating shaft and having an intermediate portion fixed to a support member, and a fixing bracket fixing both ends of the flexible wire member to a fixed side. Preferably.

Function: According to the rotary encoder of the present invention, the code plate, the detector, the hollow rotating shaft, the bearing, and the support member are combined into a unit, so it can be easily installed by simply attaching it to the shaft to be measured. Moreover, since the hollow rotary shaft is equipped with a fixing means that fixes the shaft to the shaft to be measured so that the shaft center can be adjusted, the eccentricity can be reduced by adjusting the shaft center while measuring the shaft center position on the measurement surface, and the cumulative pitch can be reduced. Errors can be reduced and high resolution can be achieved.

In addition, if the detector is a laser type that detects narrow beam-like bright and dark fringes caused by Fraunhofer diffraction, there is no risk of detection errors even if the gap between the code plate and the detector is set large. By providing the fixing means, the diameters of the hollow rotary shaft and the bearing become larger, the bearing accuracy decreases, and even if the surface runout of the code plate increases, no detection error occurs.

Furthermore, if the measurement surfaces are provided at both ends of the hollow rotating shaft, the accuracy of detecting the axis will be increased.

Furthermore, by fixing the support member only in the rotational direction and allowing it to float in other directions, load fluctuations do not occur on the bearings due to rotation, and the rotation system is not adversely affected.

EXAMPLE Hereinafter, an example of the present invention will be described based on FIGS. 1 and 2.

In FIG. 1, ``■'' is a hollow rotary shaft that is fitted onto the shaft 2 to be measured, and a support flange 3 for the code plate 4 is provided on the outer periphery of the shaft. The inner periphery of the code plate 4 is brought into contact with and fixed to the support on one surface of the support flange 3. The hollow rotating shaft l is rotatably supported by a support member 7 made of an annular plate via a pair of ball bearings 6. A detector 8 for detecting the rotational position of the code plate 4 is disposed on the support member 7 . This detector 8 irradiates the code plate 4 with laser light from a laser light source, and irradiates light and dark fringes of a Fraunhofer diffraction image generated by slits regularly formed in the code plate 4 onto a photodetecting element through the slits. It is configured as follows.

Reference numeral 9 denotes a cover that covers the code plate 4 and the detector 8, and its outer circumference is fixed to the outer circumference of the support member 7. 6a is a fixing nut for the bearing 6, which is screwed onto the outer periphery of the hollow rotating shaft l. The outer circumferential surfaces of both ends of the hollow rotary shaft 1 on the outer side in the axial direction from the cover 9 and the fixed nut 6a are measurement surfaces 10a formed exactly on the same axis as the code plate 4;
10b.

A fixing means 11 is interposed between the outer circumferential surface of the shaft to be measured 2 and the inner circumferential surface of the hollow rotary shaft 1, and fixes the hollow rotary shaft to the shaft to be measured so that the axis center can be adjusted. The clamp means is composed of a pair of wedge-shaped sleeves 12a, 12+) that are attracted to each other, an angled sleeve 14 that engages with the inner periphery of these wedge-shaped sleeves 12a, 12b, and an angled sleeve 15 that engages with the outer periphery of the wedge-shaped sleeves 12a, 12b. There is. The outer periphery of the chevron-shaped sleeve 15 is divided into two parts at the central position in the axial direction, and an adjustment distance piece 16 is interposed therebetween.

Further, as shown in FIGS. 2(a) and 2G, the support member 7 is fixed to the outer periphery of the support member 7 only in the rotational direction, and is connected to the fixing part 18 in a state where it can float in other directions. Coupling means 17 are provided. The coupling means 17 includes an engagement pin 19 protruding from the support member 7 in the radial direction, and a locking bracket 2 that engages the engagement pin 19 from the circumferential side.
The locking bracket 20 is attached to the fixed part 18, and the press locking pin 21 is attached to the locking bracket 20 so as to be retractable and retractable, and is secured by a spring 22. It is biased to protrude.

Next, a procedure for attaching the low-resolution encoder having the above configuration to the shaft 2 to be measured will be explained. The hollow rotating shaft 1 is externally fitted onto the shaft to be measured 2, and the fixing means 11 with the fastening bolts 13 loosened is interposed between the inner peripheral surface of the hollow rotating shaft 1 and the outer peripheral surface of the shaft to be measured 2, Further, the engagement pin 19 protruding from the support member 7 is press-fitted between the locking bracket 20 and the pressing locking pin 2I.

Next, after tightening the fastening bolt 13 to fix the shaft 2 to be measured and the hollow rotating shaft 1, the eccentricity of the hollow rotating shaft 1 is measured by applying a dial gauge to the measurement surfaces 10a and 10b while rotating the shaft 2 to be measured. do. Once the amount of eccentricity and the direction of eccentricity are known,
Adjust the axial center of the hollow rotating shaft 1 by slightly loosening the fastening bolt 13, and repeat the adjustment process of tightening and fixing the fastening bolt 13 again to align the axial center of the shaft 2 to be measured and the hollow rotating shaft 1. The installation work is completed when the value is 0 or more.

The axis center of the hollow rotating shaft 1 can be adjusted by forcibly displacing the hollow rotating shaft 1 by tapping or the like.
This is done by changing the relative positions of b and the chevron sleeves 14,15.

Next, the operation as a rotary encoder will be explained. When the shaft 2 to be measured rotates, the code plate 4 rotates together with the hollow rotating shaft 1, and the rotation state is detected by the detector 8. By processing the detection signal, the rotational position and rotation of the shaft 2 to be measured are determined. Speed is detected.

At this time, since the shaft to be measured 2 and the hollow rotary shaft 1 are fixed with their axes aligned by the fixing means II, the code plate 4 eccentrically rotates as the shaft to be measured 2 rotates due to the eccentricity of the code plate 4. (whirling) will not cause an accumulated pitch error in the detection results.

In addition, the detector 8 is of a laser type and detects narrow beam-shaped bright and dark stripes caused by Fraunhofer diffraction of the laser beam, so even if a relatively large gap is provided on both sides of the code plate 4, it can be reliably detected. Error-free position detection is possible. Therefore, even if the diameters of the hollow rotary shaft 1 and the ball bearing 6 are increased due to the interposition of the fixing means 11 and the bearing accuracy is reduced, and rotational surface runout occurs in the code plate 4, there is no risk of a detection error occurring.

Furthermore, since the support member 7 is fixed only in the rotational direction by the coupling means 17 and can float in other directions, even if there is slight eccentricity that does not affect rotation detection, it will not be affected during rotation. Since the support member 7 can be displaced according to the eccentricity, the bearing 6
There is no possibility that a large load will act on the motor and cause uneven rotation.

In the above embodiment, an example was shown in which the engagement pin 19 was used as the coupling means 17 between the support member 7 and the fixed part.
As shown in Figures (a) and Φ), the central part of the piano wire 24 is fixed with a fixture 23 attached to the outer periphery of the support member 7, and both ends of this piano wire 24 are fixed with fixing brackets 25. You can. In this case as well, the same effect can be obtained by the piano wire 24 acting as a rigid body in the rotational direction along its axial center direction and acting as a weak elastic body in other directions.

Effects of the Invention According to the rotary encoder of the present invention, as is clear from the above description, the code plate, the detector, the hollow rotating shaft, the bearing, and the support member are combined into a unit, so that the rotary encoder can be directly used to be measured. It can be easily installed by simply attaching it to the shaft, and it is equipped with a fixing means that fixes the hollow rotating shaft to the shaft to be measured so that the shaft center can be adjusted. By adjusting it, the eccentricity can be reduced and the accumulated pitch error can be reduced, and it can also be used with high resolution.

In addition, if the detector is a laser type that detects narrow beam-like bright and dark fringes caused by Fraunhofer diffraction, there is no risk of detection errors even if the gap between the code plate and the detector is set large. By providing the fixing means, the diameter of the hollow rotary shaft and the bearing becomes large, and even if the bearing accuracy is reduced and the surface runout of the code plate becomes large, no detection error occurs.

Furthermore, if the measurement surfaces are provided at both ends of the hollow rotating shaft, the accuracy of detecting the axis will be increased.

Furthermore, by fixing the support member only in the direction of rotation and allowing it to float in other directions, there is no load fluctuation on the bearings as it rotates, and there is no negative impact on the rotating system, resulting in great effects. Demonstrate.

[Brief explanation of the drawing]

1 and 2 show one embodiment of the present invention, FIG. 1 is a longitudinal sectional front view, FIG. 2 is a connecting means, FIG. A bottom view and FIG. 3 show other examples of the coupling means, FIG. 3(a) is a side view, FIG. 3(b) is a bottom view, and FIGS. be. ■...Hollow rotating shaft, 2...Axle to be measured,
4... Code plate, 6... Ball bearing, 7...
...Supporting member, 8...Detector, 10a,
10b...Measurement surface, 11...Fixing means, 12a, 12b...Wedge-shaped sleeve, 13
...... Fastening bolt, 14.15... Chevron sleeve, 17... Connection means, 18...
・Fixing part, 19...Engaging pins 1, 20...
... Locking bracket, 21... Press locking pin,
24...Piano wire, 25...Fixing bracket. Agent: Patent Attorney Industry: Shigetaka Haka1 personFigure 1Figure Figure 1

Claims (7)

[Claims] (1) A code plate, a hollow rotating shaft to which the code plate is fixed,
A supporting member that rotatably supports the hollow rotating shaft via a bearing and is attached with a detector for detecting the rotational position of the code plate, and is interposed between the inner circumferential surface of the hollow rotating shaft and the shaft to be measured. A rotary encoder comprising: a fixing means for fixing the hollow rotating shaft to the shaft to be measured so that the axis can be adjusted; and a measuring surface formed on the outer peripheral surface of the hollow rotating shaft. (2) The detector irradiates the code plate with laser light from a laser light source, and the light and dark fringes of the Fraunhofer diffraction image generated by slits regularly formed in the code plate are irradiated onto the photodetection element through the slits. 2. The rotary encoder according to claim 1, wherein the rotary encoder is configured as follows. (3) The rotary encoder according to claim 1 or 2, wherein the measurement surfaces are formed on protrusions at both ends of the hollow rotating shaft. (4) The rotary encoder according to claim 1, 2 or 3, wherein the fixing means comprises a clamping means comprising a pair of wedge-shaped sleeve and chevron-shaped sleeve that are drawn together by a screw mechanism. (5) The support member according to claim 1, 2, 3 or 4, further comprising a coupling means for fixing the support member only in the rotational direction around the axis of the hollow rotating shaft and coupling it to the fixed side so that it can float in other directions. rotary encoder. (6) The rotary encoder according to claim 5, wherein the coupling means includes an engagement pin protruding in the radial direction from the support member, and a fixed-side locking member that engages with the engagement pin in the circumferential direction. . (7) The coupling means includes a flexible wire arranged tangentially to the circumference of the hollow rotating shaft with its middle portion fixed to the support member, and its both ends fixed to the fixed side. 6. The rotary encoder according to claim 5, further comprising a fixing bracket.