JPH02271107A - Rotary encoder - Google Patents

Abstract

PURPOSE:To prevent the leak and splash of grease to the side of a code plate with the pumping action of high speed rotation by forming a minute gap between the end opposite to the code plate of a rotating shaft and its fixed face before installing a disc, and communicating the inner peripheral part of the minute gap with the inside of ball bearings. CONSTITUTION:A rotating shaft 1 forming a support flange 3 of a code plate 4 is supported against its supporting member 8 with ball bearings 7a, 7b, and a disc 11 is installed on the end of the shaft 1 opposite to the code plate 4. Furthermore, a minute gap d is formed between the disc 11 and the side faces of the ball bearing 7b end the supporting member 8. Seal members 12 are installed on mutually opposite sides of the ball bearings 7a, 7b, but no seal member is installed on the sides facing each other. Therefore, the pumping action of the disc 11 due to high speed rotation creates air current in the direction of A to prevent the leak and splash of grease from inside the ball bearings 7a, 7b toward the code plate.

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 Figure 2.
A support flange 22 is provided protruding from one end of the hollow rotating shaft 21 through which the measurement shaft can be inserted, and the inner circumference of a code plate 23 having regular slits formed on the outer circumference is placed on the support flange 22. The hollow rotary shaft 21 is rotatably supported by a support member 25 via a pair of ball bearings 24, and a light projecting portion is provided with the outer peripheral portion of the code plate 23 sandwiched between the support member 25. and a detector 26 having a light receiving section.

Note that the reason why a hollow rotating shaft is used as the rotating shaft 21 as described above is because the rotating shaft 21 is a solid IF-! When using I, it is necessary to connect the encoder to the end of the measurement axis using a coupling, which requires a large space, and in order to support high-speed rotation, the axis must be aligned with extremely high precision, which may cause vibration. This is because there is a risk that this may occur, and 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 Incidentally, for example, in the precision machining field, high-speed and high-precision machining has been increasingly required in recent years, and as a result, there has been an increasing demand for row reencogs that can handle high-speed rotation. Along with this, there has been a demand for something that is easy to maintain.

However, since the ball bearing 24 rotates at high speed, the grease is sealed with a non-contact sealing member, and in order to improve the rotation accuracy of the code plate 23, the ball bearing 24 is placed close to the code plate 23. Therefore, when the rotary shaft 21 is rotated at high speed, an airflow is generated radially outward from the ball bearing as the cord plate 23 and the support flange 22 rotate at high speed, and the grease in the ball bearing 24 is The grease leaks from the sealing part and scatters, and the scattered grease hits the cord plate 2.
There is a problem in that there is a problem that dirt may adhere to the surface of the sensor 3 and cause detection errors if maintenance is not performed frequently.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, it is an object of the present invention to provide a low-return encoder that does not scatter grease even when rotated at high speed and is free from the risk of staining the code plate.

Means for Solving the Problems In order to achieve the above object, the present invention rotatably supports a rotating shaft on which a support flange for fixing a code plate is formed by a support member via a ball bearing. The disc is arranged with a minute gap provided between the end opposite to the code plate and the fixing surface, and the inner peripheral part of the minute gap is communicated with the inside of the ball bearing.

Function According to the present invention, as the rotary shaft rotates at high speed, the disc also rotates at high speed, and its pumping action forces the air in the minute gap between it and the fixed surface to the outer periphery, and as a result, air is pumped inside the ball bearing. An airflow is generated toward the disc side, which can reliably prevent the grease inside the ball bearing from leaking to the code plate side, and the leaked grease can stain the code plate and cause detection errors. do not have.

Example An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, reference numeral 1 denotes a rotary shaft consisting of a hollow shaft in which a cylindrical hole 2 is formed 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 thereof. There is. The outer periphery of one side of the support flange 3 on one end of the rotating shaft is a receiving surface 3a, on which the inner periphery of the code plate 4 is placed and supported, and the inner periphery of the code plate 4 is supported by an adhesive 5. It is fixed to the flange 3. Further, a boss portion 3b is formed on the inner peripheral portion of the support flange 3 on the above-mentioned − surface side, and the elastic pressure plate 6 elastically engaged with the outer periphery of the boss portion 3b and the receiver are formed between the surface 3a. The code plate 4 is compressed. The code plate 4 is made of an annular glass plate, and slits are regularly formed on the outer periphery of the code plate 4.

The rotating shaft l is connected to the support member 8 via a pair of ball bearings 7a and 7b.
It is rotatably supported. These ball bearings 7a, 7
b is fitted into the bearing hole 8a of the support member 8 from both sides, and its outer race is engaged with an annular protrusion 8b protruding from the middle of the bearing hole 8a, and the rotating shaft 1
A stepped portion 1 formed near the support flange 3 on the outer peripheral surface of the
The inner race of one ball bearing 7a is engaged with a, and the inner race of the other ball bearing 7b is fixed to the rotating shaft 1 by being pressed by a nut 9 fitted to the outer peripheral surface of the other end of the rotating shaft 1. ing.

Further, a detector 10 for detecting the rotational position of the code plate 4 is disposed on the support member 8. This detector lO is
The code plate 4 is irradiated with laser light from a laser light source, and light and dark fringes of a Fraunhofer diffraction image generated by slits regularly formed on the outer periphery of the code plate 4 are irradiated onto the photodetecting element through the slits. has been done.

A disk 11 is integrally provided on the outer periphery of the nut 9 so that a minute gap d is formed between the outer end surface of the ball bearing 7b on the other end side of the rotation axis l and the side surface of the support member 8. There is. Moreover, no seal members are provided on the mutually opposing side surfaces of the pair of ball bearings 7a and 7b, and sealing material portions 12 are provided only on the mutually opposite side surfaces. Note that the seal member 12 is attached to the outer race and is in a non-contact state with the inner race.

Next, the operation will be explained. When the rotating shaft 1 rotates at high speed with the rotation of the measuring shaft inserted and fixed to the rotating shaft 1, the support flange 3
The cord #Ii, 4 rotates at high speed through the cord #Ii, 4, and its rotational position is detected by the detector 9. This detector 9 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, errors are guaranteed. It is possible to detect the position without Therefore, even if the code plate 4 is displaced in the thickness direction as it rotates, there is no fear that the encoder will be damaged due to contact between the code plate 4 and the detector 9.

In addition, as the rotating shaft 1 rotates at high speed, an air flow in the direction of the arrow is formed by the pumping action of the disc 11, and the inner periphery of the gap d between the inner periphery of the disc 11 and the ball bearing 7b is becomes a negative pressure, and air is sucked into the ball bearings 7a, 7b from the support flange 3 and cord plate 4 side on one end of the rotating shaft l. Sea -- By providing the small member 12, the ball bearing 7
Grease is held between a and 7b, and the suction air flow is easily formed. In this way, the air flow reliably prevents the grease in the ball bearing 7a or 7b from leaking to the code plate 4 side, and the leaked grease scatters and causes dirt on the code plate 4. There isn't. Therefore, even if maintenance is not performed frequently, the code plate 4 will not be contaminated with scattered grease and cause detection errors.

In the above embodiment, sealing members were not provided on the inner side surfaces of the ball bearings 7a and 7b to facilitate the formation of air flow. An air flow may be formed from the outer side of each ball bearing 7a, 7b toward this space 13 by introducing the grease into the space 13 between the ball bearings 7a, 7b. Furthermore, by arranging the seal members 11 on both sides of each ball bearing 7a, 7b, the grease can be reliably held within each ball bearing 7a, 7b. In order to introduce negative pressure into the space 13, a disc 1 is attached to the side surface of the nut 9 and the outer peripheral surface of the rotating shaft 1.
What is necessary is to form an air passage groove that communicates with the space 13 from the inner circumference of the space 13.

Effects of the Invention According to the rotary encoder of the present invention, as is clear from the above description, a disc is arranged at the end of the rotary shaft opposite to the code plate with a minute gap provided between it and the fixed surface. Since the inner peripheral part of the minute gap is communicated with the inside of the ball bearing, as the rotating shaft rotates at high speed, the ζ disk also rotates at high speed, and its pumping action creates an air flow inside the ball bearing toward the disk side. This can reliably prevent grease from leaking from inside the ball bearing to the code plate, prevent grease from scattering and attaching to the code plate, and prevent detection errors caused by dirt on the code plate. It has a great effect.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional front view of an embodiment of the present invention, and FIG. 2 is a longitudinal sectional front view of a conventional example. 1...Rotating shaft, 3...Support flange,
4... Code plate, 7a, 7b... Ball bearing, 8... Support member, 11... Disc plate,
d...Minute gap.

Claims (1)

[Claims] A rotating shaft on which a support flange for fixing the code plate is formed is rotatably supported by a support member via a ball bearing, and a minute gap is created between the end of the rotating shaft on the opposite side from the code plate and the fixed surface. A rotary encoder characterized in that a disc is provided and an inner peripheral portion of the minute gap is communicated with the inside of a ball bearing.