JPS5920044B2 - Bearing preload device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a constant pressure preloading device for a ball bearing, and more particularly to a preloading method for a rotating device that is required to suppress rotational signal ρ vibration to an extremely low level.

To prevent vibration of the rotating shaft supported by ball bearings,
Preload is applied to the ball bearing in the thrust direction using a spring, and FIG. 1 is a cross-sectional view of an O-transmission polygonal mirror optical deflector.

The following will be explained according to the drawings: 1 is a rotating shaft, 2 is a rotor magnet, and 3 is a field winding. 4 and 5 are ball bearings press-fitted into the rotating shaft 1.

6 is a housing for the ball bearing 4; T is a spring for applying preload to the ball bearings 4 and 5; 8 is a pressure adjustment ring for adjusting the pressure of the spring; 9 is flexible to support the ball bearing 4. Board material, 10, 11
is a case, and 12 is a rotating polygon mirror.

The outer ring of the ball bearing 4 is press-fitted or bonded to the housing 6 in order to suppress vibration as much as possible. The same applies to the ball bearing 5. In the configuration shown in FIG. 1, the preload of the spring adjusted by the pressure adjustment ring 8 is applied to the ball bearings 4 and 5 through the housing 6.

As a result of the preload being applied, the inner and outer rings of the ball bearings 4 and 5 move in opposite directions in the thrust direction by the thrust clearance of the ball bearings, and the inner ring, ball, and outer ring come into contact with each other and are supported by the outer ring and the ball. This allows the inner ring to rotate without rattling. In general rotating equipment such as small motors, vibrations of the rotating shaft can be suppressed to within a practically sufficient accuracy by such a method.

However, for devices such as rotating polygonal mirror optical deflectors that rotate at high speed and require extremely low vibration of the rotating shaft, this method alone is insufficient to keep the vibration of the rotating shaft within the required precision. It cannot be suppressed. This point will be explained in the second section below.
This will be explained with reference to FIGS. 3, 3, 4, 5, and 1. FIG. 3 is a side view of a spring for preloading a ball bearing.

In general, the parallelism of the load-receiving surfaces Ta and Tb of a flat spring for ball bearing preloading is not sufficiently suppressed.
For example, the outer diameter is 35□. In the case of a flat spring with a plate thickness of about 0.4 mm, the actual parallelism is about several minutes to more than ten minutes. If there is a discrepancy in parallelism between the surfaces 7a and 7b that receive the load in this way,
For example, the counter spring pressing surface 8a of the pressure adjustment ring 8 in FIG.
is maintained perpendicular to the central axis of the rotating shaft 1, and even if the ball bearing 4 is installed perpendicularly to the raceway surface of the inner ring or to the center of the rotating shaft 1, the vertical section AOA2 cross section of the ball bearing in FIG. As shown in the figure, the outer ring 40 of the ball bearing 4 is inclined with respect to the inner ring 41 by an angle θ due to the deviation of the parallelism of the spring.

In this way, when the outer ring 40 of the ball bearing 4 is inclined with respect to the inner ring 41 and pressurized P is applied as shown in the figure, the outer ring 40
The balls 4b constituting the ball bearing 4 on the AOA2 section of the vertical cross-sectional view closest to the XX direction of the tilt direction of 0 contact the outer ring 40 and the inner ring 41, but are closest to the YY' direction perpendicular to the XX2 direction. The balls 4b5 constituting the ball bearing on the longitudinal section BOB2 are B
As the outer ring 40 is tilted θ in the XX″ direction as shown in the OB2 cross-sectional view, the amount of movement of the outer ring 40 in the thrust direction relative to the inner ring 41 due to the preload P becomes smaller than when θ=0.
The outer ring 40 and the inner ring 41 cannot contact each other, and a slight gap remains within the ball bearing. This is done by placing the outer ring 40 of the ball bearing in a plane that includes the XX2 axis and the center axis of the ball bearing 4 without applying any preload.
When b is rotated until both the outer ring 40 and the inner ring 41 come into contact, a gap approximately the same amount as the initial gap of the ball bearing 4 remains between the ball 4b' on the cross section of the BOB 5 and the outer ring 40 and the inner ring 41. It can be easily understood if you think about it.

Now, if a slight gap remains in the cross-sectional direction of the ball bearing, when the rotating shaft rotates at high speed, the rotating shaft will generate vibrations in this direction.

When vibration occurs in the radial direction in the two ball bearings 4, the geometric center of the rotating shaft 0A0'
A moves to 0B05B, and in the case of the rotating polygonal mirror optical deflector, the inclination angle of the mirror surface 12p (the angle of inclination of the mirror surface with respect to a plane perpendicular to the rotation center axis) increases by Δψ as shown. Rotating polygonal mirror type optical deflection, the inclination Δψ of the mirror surface of the deflector is the fifth
As shown in the figure, the polarized beam 13 causes a positional deviation d of the scanning line drawn on the scanning plane 14 in a direction perpendicular to the scanning line. When the scanning plane moves at a constant speed in a direction perpendicular to the scanning line, this appears as pitch unevenness of the scanning line, making the image drawn on the scanning plane unsightly. The inclination of the ball bearing outer ring due to the parallelism error of the counter spring not only induces vibration in the radial direction of the rotating shaft as described above, but also induces vibration in the thrust direction of the outer ring. Vibration in the thrust direction of the ball bearing also induces vibration in other optical systems in equipment equipped with a rotating polygonal mirror optical deflector, and as with the tilt of the rotation axis, pitch unevenness in scanning and scanning lines can be caused. This causes fluctuations (jitter) in the scanning direction. One way to solve this kind of problem is to use two fitting washers with a spherical sliding surface between the ball bearing and the preload spring, as shown in Japanese Utility Model Publication No. 40-5056, for example. A method has been proposed to absorb the spring parallelism error.

However, providing a spherical sliding surface on the washer means that the radii of the spherical surfaces must be precisely aligned.
Since the finishing accuracy of the spherical surface must be improved, the processing cost is high, so it cannot be said to be an inexpensive method. The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and is designed to ensure that even if there is a parallelism error on the surface receiving the load of the preload spring, the outer ring of the ball bearing will always be parallel to the inner ring without tilting. The purpose is to provide a preload mechanism at low cost.

The present invention will be explained below with reference to the drawings.

FIG. 6 is a sectional view of one embodiment of the present invention.

Figure 7 is a perspective view of the preload ring section for transmitting preload.
The figure is a partially enlarged view of the preload portion. 15 in Figures 6, 7, and 9
is formed on a ring concentric with the center of the rotating shaft 1, and its structure includes two hemispherical protrusions 16 located opposite to the center of the rotating shaft on a straight line passing through the center of the lower surface, as shown in FIG.
and a preload transmission ring formed with two hemispherical protrusions 17 at opposite positions to the center of the rotating shaft on a straight line passing through the center of the upper surface and substantially perpendicular to the straight line, 18 is a preload of a spring. This is a seat for transmitting the information to the protrusion 17. The numbers of other components are exactly the same as in FIG. With the above configuration, as shown in FIG. 9, even if the parallelism of the spring 7 is out of alignment, the preload applied by the spring 7 will always be applied to the rotation axis 1, regardless of the inclination of the lowest surface 7c of the spring 7. , that is, the center of the ball bearing 4.

Because now the straight line passing through the two hemispherical protrusions 17)
Considering the moment, the entire preload ring...The forces Pl9P2, P3, and P4 applied to the preload receiving surface 6a of the housing 6 and the lower surface 18b of the seat 18 are balanced with each other, so the preload on the housing 6 from the protrusion 16 is The resultant force of the preloads P3 and P4 transmitted to the receiving surface 6a acts on the intersection of the straight line passing through the two hemispherical protrusions 17 and the straight line passing through the two hemispherical protrusions 16, that is, the center of the ball bearing 4. It is from. The preload of the spring 7 is the ball bearing ±
If it acts on the center of the ball bearing, the outer ring 40 of the ball bearing will be correctly parallel to the inner ring 41, and all the balls 4b will come into contact with the inner and outer rings, eliminating the gap in the ball bearing all around the circumference. In this way, if preload can be applied with the gap in the ball bearing completely eliminated, the effect of the preload on the ball bearing can be maximized, and the vibration of the rotating shaft can be suppressed to an extremely low level.
Furthermore, with such a configuration, it is possible not only to eliminate the influence of the eccentricity of the parallelism of the counter spring, but also to prevent the counter spring pressing surface 8a of the pressure adjustment ring 8 and the preload receiving surface 6 of the housing 6 from being affected.
a and the influence of the perpendicularity error of the end face abutting surface 6b of the ball bearing outer ring 40 of the housing 6 with respect to the central axis of the rotating shaft 1 can also be eliminated.

It should be noted that the preload ring part does not necessarily have to have the protrusions 16 and 17 formed in a hemispherical shape as shown in FIG. 7, but can be formed in a semicylindrical shape whose axis passes through the center of the ring as shown in FIG. You may do so.

Further, the spring for preloading does not have to be a flat spring; a compression coil spring, a plate spring, or another spring type having the same function may be used. As described above, with the configuration of the present invention, a great effect can be achieved by simply interposing a pressure transmitting member as a bearing preloading means for a rotating shaft that is subject to extreme vibration and whirling, and is extremely useful in practical use. be.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a conventional bearing preload device applied to a rotating polygonal mirror optical deflector, Figure 2 is a three-sided view showing the state of the ball bearing of the device in Figure 1, and Figure 3 is A side view of a spring for preloading, FIG. 4 is an explanatory diagram of the operation of the device in FIG. 1, FIG. 5 is an explanatory diagram of the function of the device in FIG. 1 as an optical deflector, and FIG. 6 is a diagram showing the bearing preload of the present invention. A vertical cross-sectional view of the device applied to a rotating polygonal mirror type optical deflector, FIG. 7 is a perspective view of the preload ring portion in FIG. 6, and FIG.
FIG. 9 is a perspective view showing another example of the configuration of the preload ring portion in the figure, and FIG. 9 is a partially enlarged longitudinal cross-sectional view of the preload portion in FIG. 6. 1...Rotating shaft, 4...Ball bearing, 6...Using, 7...Set spring, 8...Pressure adjustment ring , 12...
・Rotating polygon mirror, 15...Preload ring, 16,1
7... protrusion, 18... seat.

Claims (1)

[Claims] 1. A bearing preloading device in which a rotating shaft is supported by at least two ball bearings, and a preloading means applies a preload in the thrust direction of the ball bearing, which is provided between the ball bearing and the preloading means, and is provided between the ball bearing and the preloading means, Protrusions formed at two opposing positions on a straight line passing through the center of the rotating shaft receive pressure from the preloading means, and formed at two positions other than the two opposing positions on a straight line passing through the center of the rotating shaft. A bearing preloading device comprising a preload transmitting member that applies pressure from the preloading means to the ball bearing with a protrusion.