JPH0259614A - Rotary encoder - Google Patents

Abstract

PURPOSE:To obtain the rotary encoder for rotating at high speed, and also, to make it compact and inexpensive by fitting a rotary shaft to which a code plate is fixed to an intermediate rotary shaft so as to be freely rotatable through a first ball bearing, and supporting this intermediate rotary shaft so as to be freely rotatable by a supporting member through a second ball bearing. CONSTITUTION:On the receiving surface 3a of a supporting flange 3 of a rotary shaft 1, the inside peripheral part of a code plate 4 is placed and supported, and fixed with an adhesive agent 5. Also, plural tongues 6b of an elastic inserted pressure piece for inserting and holding the code plate 4 between its piece and the receiving surface 3a are pressed and fitted into the outside periphery of a boss part 3b of the supporting flange 3. Moreover, the rotary shaft 1 fitted to a cylindrical intermediate rotary shaft 8 through a pair of ball bearings 7 and supported so as to be free rotatable, and this intermediate rotary shaft 8 is supported so as to be freely rotatable by a supporting member 10 through a pair of ball bearings 9. Accordingly, the rotary shaft 1 can be supporting by using the ball bearing having an allowable rotating speed of about half of the maximum rotating speed of the rotary shaft 1, and it is possible to cope with high speed rotation.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rotary encoder, and more particularly to a high-speed rotary encoder.

Conventional technology Conventionally, high-speed rotary encoders include, for example, 1
Those that can handle rotational speeds of 10,000 r, p, m or more have been put into practical use. An example of its configuration is shown in FIG.
A code plate 22 in which slits are regularly formed is fixed to the end of a hollow rotating shaft 21 through which the measuring shaft can be inserted, and this hollow rotating shaft 21 is rotatably supported by a support member 24 via a pair of ball bearings 23. and a cord Fi2 is attached to this support member 24.
A detector 25 having a light emitting part and a light receiving part is installed with the light emitting part 2 in between.

When a hollow rotating shaft is used as the rotating shaft 21 as described above,
The larger the diameter of the ball bearing 23, the more difficult it becomes to handle high-speed rotation, and the cost increases. Nevertheless, the reason for using a hollow rotating shaft is that if a solid shaft is used as the rotating shaft 21, it is necessary to connect the encoder to the shaft end of the measuring shaft using a coupling, which requires a large space. To support high-speed rotation, there is a risk of vibration unless the axes are aligned with extremely high precision.
Furthermore, problems arise, such as the need for the coupling to have rigidity to withstand acceleration during acceleration and deceleration due to servo drive.

Problems to be Solved by the Invention In recent years, for example, in the field of precision machining, high-speed and high-precision machining has been increasingly required, and therefore there has been a demand for rotary encoders that can handle even higher rotation speeds.

However, because of the above reasons, it is necessary to use ball bearings with a large diameter, and it is difficult and extremely expensive to obtain ball bearings that can handle high-speed rotation. There is a problem with becoming. Another option is to use an air bearing, which is known as a bearing for high-speed rotation, but since such ultra-high-speed rotary encoders are not mass-produced, this also poses the problem of being extremely expensive. .

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, it is an object of the present invention to provide a rotary encoder that can handle high-speed rotation, is compact, and is inexpensive.

Means for Solving the Problems In order to achieve the above object, the present invention includes a rotary shaft to which a code plate is fixed, which is rotatably fitted to an intermediate rotary shaft via a first ball bearing, and the intermediate rotary shaft is connected to the intermediate rotary shaft. It is characterized in that it is rotatably supported by a support member via a second ball bearing.

Further, a motor for forcibly rotating the intermediate rotating shaft may be interposed between the intermediate rotating shaft and the support member.

Preferably, the detection unit irradiates the code plate 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 onto a photodetector through the slits. A laser system configured as follows is used.

According to the present invention, the intermediate rotating shaft is arranged between the rotating shaft and the support member, and the first and second ball bearings are arranged between them, so that the intermediate rotating shaft is connected to the first and second ball bearings. The bearings rotate at a rotational speed at which the rotational resistances of the bearings are equal, that is, approximately half the rotational speed of the rotational shaft, and the maximum rotational speed of the first and second ball bearings is approximately half the rotational speed of the rotational shaft. Therefore, relatively inexpensive mass-produced ball bearings can be used, and even if a hollow rotary shaft with a large diameter is used to achieve a compact configuration, the inexpensive ball bearings can support high-speed rotation.

Furthermore, by forcibly rotating the intermediate rotating shaft using a motor at a rotation speed that is approximately half of the rotation speed of the rotating shaft, the rotation speed between the first and second ball bearings can be reliably distributed approximately in half. This prevents the rotation speed from unexpectedly exceeding the allowable rotation speed.

Furthermore, by using a laser type detection unit to detect narrow beam-like bright and dark stripes caused by Fraunhofer diffraction, a relatively large gap can be provided on both sides of the code plate, which allows the ball bearing to be arranged in two stages. Due to this arrangement, even if the code plate is displaced in the plate thickness direction as it rotates, there is no fear that the encoder will be damaged due to contact.

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

In FIG. 1, ■ is a rotary shaft consisting of a hollow shaft formed with a cylindrical hole 2 through which a measuring shaft (not shown) is inserted, and a support flange 3 for a code plate 4 is provided on the outer periphery of one end. There is. One surface of the outer periphery of this support flange 3 is a receiving surface 3.
a, the inner peripheral part of the code plate 4 is placed and supported,
And the inner peripheral edge of the code plate 4 is attached to the support flange 3 with adhesive 5.
is fixed to. Further, a boss portion 3b is formed on the inner peripheral portion of the support flange 3 so as to protrude from the negative side.

Reference numeral 6 denotes an elastic clamping piece that clamps the code plate 4 between the support surface 3a, and as shown in FIG. is protruded, and by being press-fitted to the outer circumference of the boss portion 3b of the support flange 3, the tongue piece 6b is elastically deformed and locked to the outer circumferential surface of the boss portion 3b, and its elastic restoring force causes The code plate 4 is compressed.

The rotating shaft 1 is fitted and rotatably supported by a cylindrical intermediate rotating shaft 8 via a pair of first ball bearings 7, and this intermediate rotating shaft 8 is supported via a pair of second ball bearings 9. supporting member 10
It is rotatably supported.

A detector 11 for detecting the rotational position of the code plate 4 is disposed on the support member 10. This detector 11 irradiates the code plate 4 with laser light from a laser light source, and
The light and dark fringes of the Fraunhofer diffraction image generated by the regularly formed slits are irradiated onto the photodetecting element through the slits.

Next, the operation will be explained. When the rotating shaft 1 rotates with the rotation of the measuring shaft inserted and fixed to the zero-rotating shaft 1, the first ball bearing 7 and the second ball bearing 7 are inserted between the rotating shaft 1 and the support member 10. Since the intermediate rotating shaft 8 is interposed via the bearing 9, the intermediate rotating wheel 8 rotates at approximately half the rotational speed of the rotating shaft 1. That is, when the relative rotational speed between the rotating shaft 1 and the intermediate rotating shaft 8 increases from a certain rotational state, the temperature of the first ball bearing 7 rises and the rotational resistance increases, and as a result, the rotation of the ball bearing 9 of the tube 2 decreases. The resistance becomes relatively small, the rotation speed of the intermediate rotation shaft 8 increases, and the relative rotation speed of the rotation shaft 1 and the intermediate rotation shaft 8 decreases. In this way, the first and second ball bearings 7 and 9 rotate at approximately the same rotational speed, and the rotational speed of the other ball bearing increases before at least one of the ball bearings exceeds its maximum allowable rotational speed. do.

Therefore, the rotating shaft 1 can be supported using a ball bearing having an allowable rotational speed that is approximately half the maximum rotational speed of the rotating shaft 1.

The rotational position and rotational speed of the measurement shaft are detected by the detector 11 as the code plate 4 rotates together with the rotation shaft 1. This detector 11 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 will not cause errors. It is possible to detect the position without any Therefore, the first and second ball bearings 7.9
Since the encoders are arranged in two stages, there is no fear that the encoder will be damaged due to contact between the code plate 4 and the detector 11 even if the code plate 4 is displaced in the plate thickness direction as it rotates.

In the first embodiment, the intermediate rotating shaft 8 rotates at a rotational speed that equalizes the rotational resistance of the first and second ball bearings 7 and 9, and as a result, it rotates at approximately half the rotational speed of the rotating shaft 1. Although an example is shown in which the intermediate rotating shaft 8 is forcibly driven to rotate.

A second embodiment in which forced rotation is shown in FIGS. 3 and 4 is shown. In FIG. 3, the code plate 4 of the intermediate rotating shaft 8
A rotor 13 is fixed to the outer periphery of the end opposite to the side where the rotor 13 is arranged, and a stator 14 is attached to the support member 10 side facing the rotor 13 with a gap therebetween. is configured.

Next, the driving means for this motor 15 will be explained with reference to FIG. The detection signal from the detector 11 is input to the rotational speed calculation circuit 16 to output a speed signal, and the speed signal is inputted to the motor rotational speed setting circuit 17, which is approximately half of the detected rotational speed of the rotating shaft 1. The speed is set as the rotation command speed of the motor 15. The driver 18 operates based on this rotation speed command, and the motor 15 is driven so as to reach the rotation command speed. Since accuracy is not required for the rotational speed of this motor 15, there is no need to perform speed detection.

The operation of this second embodiment is similar to that of the first embodiment, and the explanation thereof will be omitted.

Effects of the Invention According to the rotary encoder of the present invention, as is clear from the above description, the intermediate rotating shaft is arranged between the rotating shaft and the support member, and the first and second ball bearings are arranged between them. Therefore, the intermediate rotating shaft rotates at approximately half the rotational speed of the rotating shaft,
The maximum rotational speed of the first and second ball bearings is approximately half the rotational speed of the rotating shaft, and relatively inexpensive ball bearings that are mass-produced can be used. Therefore, even if a hollow rotary shaft with a large diameter is used to achieve a compact configuration, high-speed rotation can be achieved using inexpensive ball bearings, and an inexpensive and compact rotary encoder for high-speed rotation can be obtained.

Furthermore, by forcibly rotating the intermediate rotating shaft using a motor at a rotation speed that is approximately half of the rotation speed of the rotating shaft, the rotation speed between the first and second ball bearings can be reliably distributed approximately in half. This prevents the rotation speed from unexpectedly exceeding the allowable rotation speed.

Furthermore, by using a laser type detection unit to detect narrow beam-like bright and dark stripes caused by Fraunhofer diffraction, a relatively large gap can be provided on both sides of the code plate, which allows the ball bearing to be arranged in two stages. Due to this arrangement, even if the code plate is displaced in the thickness direction as the code plate rotates, there is no fear that the encoder will be damaged due to contact, and other great effects are achieved.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional front view of the first embodiment of the present invention, Fig. 2 is a perspective view of an elastic clamping piece, Fig. 3 is a longitudinal sectional front view of the second embodiment of the invention, and Fig. 4 is an intermediate rotation FIG. 5 is a control block diagram of the motor that drives the shaft, and is a longitudinal sectional front view of the conventional example. 1... Rotating shaft, 4... Code plate, 7.
...First ball bearing, 8...Intermediate rotating shaft,
9...Second ball bearing 10...Support member, 11...Detector, 15...Motor. On behalf of Homura Patent Attorney Shigetaka Awano 1 person 1 - Rotation axis No. 31 @ 2 Figure 4 Ward 15-Mo 9 h

Claims (3)

[Claims] (1) The rotating shaft to which the code plate is fixed is rotatably fitted to the intermediate rotating shaft via the first ball bearing, and the intermediate rotating shaft is rotatably fitted to the supporting member via the second ball bearing. A rotary encoder characterized by support. (2) The rotary encoder according to claim 1, characterized in that a motor for forcibly rotating the intermediate rotating shaft is interposed between the intermediate rotating shaft and the support member. (3) A detection unit that irradiates the code plate with laser light from a laser light source, and irradiates the light and dark fringes of the Fraunhofer diffraction image generated by slits regularly formed on the code plate onto the photodetector through the slits. The rotary encoder according to claim 1 or 2, comprising: