JPH04233A - Bearing unit for high speed motor - Google Patents

Abstract

PURPOSE:To prevent considerable fluctuation of the speed fluctuation rate of a motor by setting the gaps between a retainer and a rotary shaft and between the retainer and an outer ring such that the grease can be fed, by a small quantity at a time, into the gaps. CONSTITUTION:A retainer 26 is arranged between a rotary shaft 18 and an outer ring 25 and a plurality of insertion holes 26a are made through the retainer 26. A ball 27 is inserted into each insertion hole 26a such that it is rollable between a groove 18a in the rotary shaft 18 and a groove 25a in the outer ring 25 when it is positioned by means of the retainer 26. Lubricant grease 28 is applied on the upper end face of the retainer 26. The grease 28 has the consistency of 235 and the gaps 29, 30 between the retainer 26 and the rotary shaft 18 and between the retainer 26 and the outer ring 25 are set such that a small quantity of grease 28 is fed into the gaps 29, 30 at a time. Consequently, the grease is not fed more than required quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a bearing device for a high-speed rotation motor used in a laser beam printer or the like.

(Prior Art) Motors used in laser beam printers, for example, are generally used at high speeds (for example, 8,000 to 15,000 rpm), and the structure of the bearing portion of such a motor is shown in FIGS. 4 and 5. Shown below. In this case, the bearing 2 is attached to the rotating shaft 1 in advance before the rotating shaft 1 is assembled into the stator (not shown).
can be assembled. An annular groove 18 is formed at a predetermined portion on the outer circumference of the rotating shaft 1, and an annular outer ring 3 is disposed on the outer circumferential portion of the rotating shaft 1 with a predetermined gap therebetween. An annular groove 3a facing the groove 1a of the rotating shaft 1 is formed in the inner peripheral portion of the outer ring 3. Reference numeral 4 denotes an annular retainer made of plastic, for example, and is disposed between the rotating shaft 1 and the outer ring 3, and has a plurality of insertion holes 4a that are open at the lower end in FIG. There is. A plurality of balls 5 are inserted into each insertion hole 4a, and are provided so as to be able to roll between the groove 1a of the rotary shaft 1 and the groove 3a of the outer ring 3 while being positioned by the retainer 4. The upper end surface of the retainer 4 in FIG. 4 is coated with lubricating grease 6.

Although not shown, a rotor yoke and a rotor magnet are assembled to the rotating shaft 1 to which the bearing 2 is assembled to form a rotor, and this rotor is assembled into a stator to form a motor.

In a motor with such a configuration, as the rotary shaft 1 rotates, the balls 5 rotate together with the retainer 4 around the rotary shaft 1 at a rotation speed that is approximately 1/2 of the rotation speed of the rotary shaft 1, and the balls 5 further rotate. Also, the grease 6 is applied to the gap 7 between the retainer 4 and the rotating shaft 1 and the retainer 4 and the outer ring 3.
The ball 5 is supplied to the ball 5 portion through the gap 8 between the ball 5 and the ball 5.

(Problems to be Solved by the Invention) However, in the conventional configuration, there was a problem in that the rate of speed fluctuation (referred to as jitter) may change greatly instantaneously when the motor rotates. If the speed fluctuation rate of the motor changes greatly in this way, it would appear as fluctuations in the image of the laser beam printer.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a bearing device for a high-speed rotating motor that can prevent the speed fluctuation rate of the motor from changing significantly.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a rotating shaft in which an annular groove is formed on the outer periphery, and a predetermined groove formed on the outer periphery of the rotating shaft over the entire circumference between the rotating shaft and the rotating shaft. an annular outer ring arranged with a gap therein and having a groove opposite to the groove formed on the inner circumference; an annular retainer arranged between the rotating shaft and the outer ring; A high-speed rotation motor is provided with a plurality of balls that are rotatably provided between the groove of the rotating shaft and the groove of the outer ring when the motor is in a state of rotation, and the end face of the retainer is coated with lubricating grease. In the bearing device, a gap between the retainer and the rotating shaft and a gap between the retainer and the outer ring,
It is characterized in that the grease is set so that it can enter only a small amount into both the gaps depending on the consistency of the grease.

(Function) By the way, the inventor of the present invention investigated the cause of the instantaneous large change in the speed fluctuation rate of the motor in the conventional configuration and found the following. The grease is supplied between the ball and the groove of the rotation shaft and between the ball and the groove of the outer ring through the gap between the retainer and the rotation shaft and the gap between the retainer and the outer ring. If the grease gets into the ball part more than necessary, it will form a lump, and the ball may be able to overcome the lump of grease. At this time, the rotation of the other balls changes instantaneously via the retainer, and as a result, the speed fluctuation rate of the motor changes instantaneously and greatly.

Therefore, in the above-mentioned means, by ensuring that only a small amount of grease enters the gap between the retainer and the rotating shaft and the gap between the retainer and the outer ring, the gap between the ball and the groove of the rotating shaft is Also, it prevents more grease than necessary from entering between the ball and the groove of the outer ring, and prevents the grease from clumping around the ball, thereby preventing the ball from climbing over lumpy grease. can do.

(Example) Hereinafter, an example in which the present invention is applied to a bearing device for a motor for a laser beam printer will be described with reference to FIGS. 1 to 3.

In FIG. 3 showing the entire motor, 11 is a stator, which is constructed by attaching a printed circuit board 14 provided with a drive coil 13 to a housing 12. On the other hand, the rotor 15 has a metal mirror attachment part 19 fitted to one end of a rotating shaft 18 on which bearings 16 and 17 are assembled vertically in advance, and a rotor magnet 20 is attached to this mirror attachment part 19. The rotor yoke 21 is attached with screws 22, and the rotating shaft 18 is attached to the bearing 16.1.
It is rotatably supported by the housing 12 via 7. A compression coil spring 23 is disposed between the upper and lower bearings 16 and 17. A mirror 24 for reflecting laser light is attached to the upper surface of the mirror attachment portion 19.

Since the upper and lower bearings 16 and 17 have the same structure, the upper bearing 16 will be described in detail with reference to FIGS. 1 and 2.

An annular groove 18a is formed at a predetermined portion on the outer periphery of the rotating shaft 18.
An annular outer ring 25 is disposed with a predetermined gap between the outer ring 25 and the rotating shaft 18.
An annular groove 25a facing the groove 18a is formed. Reference numeral 26 denotes an annular retainer made of plastic, for example, and is disposed between the rotating shaft 18 and the outer ring 25, and has a plurality of insertion holes 26a formed therein.

27 is a plurality of balls inserted into each insertion hole 26a,
It is provided so as to be able to roll between the groove 18a of the rotating shaft 18 and the groove 25a of the outer ring 25 while being positioned by the retainer 6. The upper end surface of the retainer 26 in FIG. 1 is coated with lubricating grease 28.

By the way, in this type of motor, as mentioned above, more grease 28 than necessary may get into the ball 27 portion, causing the ball 27 to overcome the lumpy grease 28, which causes the speed fluctuation rate to change instantaneously. The problem was that there was a big change.

Therefore, in this embodiment, the grease 28 has a consistency of 235 (JIS K2220.5).
．． 3), and grease 28 fills the gap 29 between the retainer 26 and the rotating shaft 18 and the gap 30 between the retainer 26 and the outer ring 25.
5. Only a small amount can enter 0. 0.05m so that
It was set to m.

In the above configuration, as the rotating shaft 18 rotates, the balls 27 rotate together with the retainer 26 around the rotating shaft 18 at a rotation speed that is approximately 1/2 of the rotation speed of the rotating shaft 18, and the balls 27 further rotate. It also rotates, and grease 2
8 is supplied to the ball 27 portion through a gap 29 between the retainer 26 and the rotating shaft 18 and a gap 30 between the retainer 26 and the outer ring 25.

At this time, a gap 29 between the retainer 26 and the rotating shaft 18
Since only a small amount of grease 28 is allowed to enter the gap 30 between the retainer 26 and the outer ring 25, the grease 28 is allowed to enter between the ball 27 and the groove 18a of the rotating shaft 18 and between the ball 27 and the outer ring 25. It is possible to prevent more grease 28 than necessary from entering between the groove 25a and the groove 25a. As a result, ball 2
Since the grease 28 does not become lumpy near 7, it is possible to prevent the ball 27 from climbing over the lumpy grease 28, thereby preventing the speed fluctuation rate of the motor from changing significantly. This makes it possible to prevent fluctuations in images produced by laser beam printers.

Further, in this embodiment, the retainer 26 and the rotating shaft 18
The gap 29 between the retainer 26 and the outer ring 25 and the gap 30 between the retainer 26 and the outer ring 25 are set smaller than before, and the retainer 26
Since the thickness dimension of the retainer 26 is made larger than that of the conventional one, the rigidity of the retainer 26 is increased and the retainer 26 becomes difficult to deform, so that the speed fluctuation rate of the motor can be further suppressed.

[Effects of the Invention] As explained above, according to the present invention, the gap between the retainer and the rotating shaft and the gap between the retainer and the outer ring are made such that only a small amount of grease can enter into both gaps. By setting it to It has the following effects.

[Brief explanation of the drawing]

Figures 1 to 3 show an embodiment of the present invention, with Figure 1 being a longitudinal sectional view of the main parts, Figure 2 being a cross sectional view of the main parts, and Figure 3 being a longitudinal sectional view of the entire motor. be. 4 and 5 show conventional configurations, with FIG. 4 being a diagram corresponding to FIG. 1, and FIG. 5 being a diagram corresponding to FIG. 2. In the drawing, 16 and 17 are bearings, 18 is a rotating shaft, and 18a
25 is a groove, 25 is an outer ring, 25a is a groove, 26 is a retainer, 7 is a ball, 28 is a grease, and 29°0 is a gap.

Claims (1)

[Claims] 1. A rotating shaft having an annular groove formed on its outer periphery, and a rotating shaft arranged with a predetermined gap around the entire circumference between the rotating shaft and the rotating shaft, and facing the groove on its inner periphery. an annular outer ring having a groove formed therein; an annular retainer disposed between the rotating shaft and the outer ring; A plurality of movably provided balls are provided, and lubricating grease is applied to the end face of the retainer, and a gap between the retainer and the rotating shaft and a gap between the retainer and the outer ring are provided. A bearing device for a high-speed rotation motor, characterized in that the gap is set so that the grease can enter only a small amount into both the gaps, depending on the consistency of the grease.