JPH0119050Y2 - - Google Patents

Description

[Detailed description of the invention] (Technical field of the invention) The invention relates to an encoder device.
The present invention relates to an encoder device in which play in the axial direction of a rotating disk is eliminated by improving the bearing portion thereof.

(Prior Art) As shown in FIG. 1, a conventional encoder device has a main body 1 rotatably supporting a rotary shaft 2 via ball bearings 3, 3', and a boss 3 on a part of the rotary shaft 2.
The rotary disk 6 is fixed through the main body 1, and a light projector 8, a light receiver 9, and a fixed pattern 7 are arranged on the main body 1, so that the rotation of the rotary shaft 2 can be extracted as a pulse signal.

In this type of encoder device, if the gap δ shown in Fig. 1 is wide, the detection accuracy will be poor and the rise of the signal will not be sharp, so the gap δ is usually set to 0.2.
It is required to be less than mm. Furthermore, if the rotating disk 6 and the fixed pattern 7 come into contact with each other, the fixed pattern 7 will be damaged, so they must be prevented from coming into contact with each other. However, since the play in the axial direction of the ball bearing is usually larger than the above-mentioned gap δ between the rotating disk 6 and the fixed pattern 7, simply supporting the rotating shaft 2 with the ball bearing 3 will result in poor detection accuracy. This has the fatal problem of not being able to provide a good encoder device.

That is, since it is necessary to arrange a large number of spherical bodies between the guide groove of the outer ring and the guide groove of the inner ring, the ball bearing essentially has a gap in the radial direction, that is, a radial gap. For this reason, the inner ring moves left and right (in the axial direction) relative to the outer ring. This movement in the axial direction is called an axial clearance, and even if there is some radial clearance, a considerably large amount of axial clearance will be generated.

If the radial clearance, which is the backlash that occurs between the outer ring and the inner ring, is not removed, the movement in the axial direction,
That is, it is difficult to remove the axial clearance, and as a result, it is difficult to maintain the accurate clearance δ.

Therefore, minimizing the axial play of the ball bearing 3, which has a large effect on the fluctuation of the gap δ, is an extremely important issue for realizing a highly accurate encoder device. It is no exaggeration to say that various means have been considered for this purpose.

For example, there is a method in which a thrust load is always applied to the rotating shaft 2 in one direction. However, this is not preferable because it requires a separate device for applying a thrust load and also increases the rotational torque of the encoder.

Another method is to offset the play in the axial direction of the ball bearings 3, 3' by keeping the distance between the inner races of the ball bearings 3, 3' constant and decreasing or widening the distance between the outer races. However, as a general mechanical design common sense, one bearing 3' is normally movable in the axial direction, so the distance between the outer rings can be expanded and
or is substantially difficult to reduce.

In other words, in order to enable the bearing 3' to move in the axial direction, the distance between the bearings must be long enough to stabilize the shaft, so if this is to be satisfied, the shaft length will inevitably become longer. Therefore, since the shaft expands and contracts in the axial direction due to thermal expansion or the like, the distance between the outer rings of the bearing cannot be forcibly regulated.

Still another method is to remove the play in the axial direction of the ball bearing by applying an appropriate shimmy to the inner ring when fitting the ball bearing onto the shaft, thereby expanding the inner ring. However, in this case, it is not possible to always machine the dimensions of the shaft and the inner diameter of the inner ring, which determine the interference, so in order to obtain the appropriate interference, it is necessary to match the actual parts one by one. This is an extremely difficult task.

(Purpose of the invention) Therefore, the present invention aims to reduce the gap between the rotating disk and the fixed pattern by making it possible to easily remove the play in the axial direction of the ball bearing without increasing the rotational torque of the rotating shaft. The purpose of the present invention is to provide a suitable encoder device.

(Structure of the invention) To achieve this object, the encoder device according to the invention includes a device frame, a fixed pattern fixed to the device frame, and a rotatably supported by the device frame via a ball bearing. An encoder device comprising a rotating shaft, a boss fitted and supported at the tip of the rotating shaft, and a rotating disk integrated with the boss and positioned in front of the fixed pattern with a gap. A tapered portion is formed at a portion of the shaft that faces the inner ring of the ball bearing, a thin walled portion having a tapered hole is formed at the tip of the boss, and the tip of the boss is connected to the tapered portion of the rotating shaft. The present invention is characterized in that a tightening element is fitted between the inner ring of the ball bearing and is provided at the tip of the rotating shaft to tighten and fix the boss to the ball bearing side.

(Example) Next, an example of the present invention will be described with reference to FIG.

Note that parts that are the same as those in the conventional device shown in FIG. 1 will be described using the same reference numerals as in FIG. 1.

Further, in the embodiments described below, an example in which an encoder device is provided at one end of the rotating shaft of another mechanical device will be described.

In FIG. 2, ball bearings 3 and 3' are fitted into the frame 11 and other fixed portions 11a. The outer ring of the ball bearing 3 is regulated in the axial direction, and the ball bearing 3' is fitted to another fixed portion 11a so as to be movable in the axial direction. The distance between these ball bearings 3, 3' is long in order to stabilize the shaft and to provide a transmission device to the shaft. Ball bearing 3 arranged in this way,
3' supports the rotating shaft 2a,
The rear end of the rotating shaft 2a is fitted into the ball bearing 3',
Alternatively, they are fitted with a tight fit.

On the other hand, a tapered portion 12 is provided at the tip of the rotating shaft 2a.
A boss 4a having a taper hole 13 having the same angle as the tapered portion 12 is fitted into the tapered portion 12. A thin wall portion 14 is formed on the boss 4a, and the outer periphery of the thin wall portion 14 fits into the inner ring of the ball bearing 3.

Therefore, the tip of the rotating shaft 2a is connected to the boss 4a.
It is supported by the ball bearing 3 via the thin wall portion 14 of the ball bearing 3. Further, the boss 4a is tightened by a nut 5 screwed onto the tip of the rotating shaft 2a.
It is designed to be integrated with the A rotating disk 6 is fixed to the boss 4a, which is fixed to the rotating shaft 2a in this manner. Further, a light emitter 8 is attached to the frame 11 via a light receiver 9 and a bracket 10 so as to sandwich the outer peripheral portion of the rotating disk 6, and a projector 8 is attached to the frame 11 so as to face the rotating disk 6. A fixed pattern 7 is fixed to. Now, when supporting the rotating shaft 2a on the ball bearing 3, the inner diameter of the inner ring of the ball bearing 3 and the boss 4 are determined in advance.
The fit between a and the outer diameter of the thin wall portion 14 is made so that there is a clearance fit relationship. And rotation axis 2
The thin part 14 of the boss 4a is fitted between the tapered part 12 of the ball bearing 3 and the inner ring of the ball bearing 3, and the nut 5 is used to tighten the boss 4a. As a result, the thin portion 14 is compressed radially outward by the action of the tapered portion 12 and the tapered hole 13. Therefore, the inner ring of the ball bearing 3 is pressed through the thin wall portion 14 and expanded, so if the tightening force by the nut 5 is adjusted, the ball bearing 3
The radial play between the inner ring and the outer ring of the ball bearing 3 can be removed, and the axial play between the outer ring and the inner ring of the ball bearing 3 can be removed without increasing the rotational resistance of the rotating shaft 2a.

Therefore, once the gap δ between the rotating disk 6 and the fixed pattern 7 is determined, it hardly changes during use, and as a result, a highly accurate pulse signal can be generated.

Note that an appropriate number of slits may be provided in the thin wall portion 14 of the boss 4a to facilitate pressing the inner ring of the ball bearing 3 outward in the radial direction. Furthermore, since the thin wall portion 14 and the inner ring of the ball bearing 3 will eventually form a fairly tight fit, the inner ring of the ball bearing 3 and the boss 4a are normally
Although it is not necessary to fix the thin wall part of the
Depending on the situation, these may be fixed.

In the above-described embodiment, a case has been described in which play in the axial direction of the ball bearing 3 is removed, but the present invention is not limited to this, and the ball bearing 3' and the rear end of the rotating shaft 2a are formed into a tapered surface. The inner ring of the ball bearing 3' may also be biased radially outward by being fitted together.

(Effects of the invention) As described above, in the present invention, the tip of the boss has a tapered portion formed in the portion facing the inner ring of the ball bearing of the rotating shaft, and a thin portion having a tapered hole at the tip. The tightening element fitted between the tapered part of the rotating shaft and the inner ring of the ball bearing and provided at the tip of the rotating shaft tightens and fixes the boss to the ball bearing side. By tightening to the ball bearing side, the thin wall part of the boss is expanded in the radial direction by the action of the tapered surface, and the inner ring of the ball bearing is expanded toward the outer ring, which reduces the rotational torque of the rotating shaft. It is possible to remove backlash in ball bearings without increasing the amount of play.

Therefore, according to the present invention, it is possible to minimize the gap δ between the rotating disk fixed to the end of the rotating shaft via the boss and the fixed pattern and to maintain it at a constant value. As a result, the accuracy of the signal generated by the encoder can be improved by several steps compared to the conventional device shown in FIG.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional device, and the second
The figure is a sectional view showing the device of the present invention. Explanation of symbols in the drawings, 2a...Rotating axis, 3,
3'...Ball bearing, 6...Rotating disk, 7...Fixed pattern, 12...Tapered portion, 13...Tapered surface.

Claims (1)

[Claims for Utility Model Registration] (a) a device frame; (b) a fixed pattern fixed to the device frame; (c) a rotating shaft rotatably supported by the device frame via a ball bearing. (d) a boss fitted and supported at the tip of the rotating shaft; and (e) a rotating disk integrated with the boss and positioned in front of the fixed pattern with a gap therebetween. (f) a tapered portion is formed at a portion of the rotating shaft that faces the inner ring of the ball bearing; (g) a thin walled portion having a tapered hole is formed at the tip of the boss; (h) the boss (i) a tightening element is provided at the tip of the rotating shaft to tighten and fix the boss to the ball bearing side; An encoder device characterized by: