JPS59204441A - Bearing - Google Patents

Abstract

PURPOSE:To increase the stability in the thrust direction of a bearing by relatively displacing previously a stator and a rotor of a motor in a rotor axial direction, and generating a magnetic force in a direction for eliminating the displacement when the rotor is rotated. CONSTITUTION:An armature 4 is displaced in a direction for separating from a thrust retainer 8 at a distance (d) from the longitudinal center of the armature 4 to the longitudinal center of a permanent magnet 5. The magnet 5 is circumferentially magnetized, and a magnetic force is operated in a direction for setting the distance (d) to zero on a sleeve 3 having the magnet 5 and a polygonal mirror 7. Accordingly, a force for axially restricting a rotary member which floats during the operation is operated on the member.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention (-4) relates to a dynamic pressure bearing suitable for use in a high-speed motor, and particularly to a thrust stabilizer thereof.

It has long been well known that ball bearings, for example, are used in the bearings of motors, which are rotary drive devices, in various types of equipment that require high-speed rotation. Bearings also feature high-speed stability, long life, and high overturning characteristics.
In order to improve accuracy and reduce unevenness in low rotation, dynamic pressure bearings using air, oil, etc. are increasingly being used.

Of course, various configurations of hydrodynamic bearings have been proposed, and the ones suitable for small motors are outlined below: Figures 1 and 2 (d) Although the configuration of the motor used to rotate the polygon mirror of the scanner mechanism used is schematically shown, it is of course not intended to be limited to this type of motor.

In FIG. 1, a stator 4 is fixed to one casing, and a permanent rotor 5 fixed to the rotating shaft 2 is disposed inside the stator 4, and the rotating shaft 2 is fixed to the casing. A polygon mirror 7 is attached to this part of the polygon mirror 7, which is covered by a cover 6.

The rotating shaft 2 has a bearing part 1a formed in the casing and a bearing member 1bvC, and is supported by the bearing part 1a.
Herringbone grooves 2a and 2b are formed on the outer peripheral surface facing the bearing member 1b, and these portions constitute a dynamic pressure bearing in the radial direction when the shaft 2 rotates.

As shown in the figure, a bearing member 1C is disposed on the upper step of the bearing portions 1b and 2b in the upper part of the figure, and a large number of grooves are formed in the radial direction of the lower surface of the bearing member 1C on the side facing the upper step. During rotation, this part acts as a hydrodynamic bearing1.
~, the shaft 2 is slightly displaced upward in the figure to support the thrust) k.

FIG. 2 schematically shows another configuration of the polygon mirror drive motor, in which parts corresponding to those shown in FIG. , Nanano 1, etc. will be omitted. In this device, a rotor 5 is attached to a sleeve 6, the sleeve 6 is loosely attached to a shaft 2 fixed to a casing 1, and a polygon mirror 7 is fixed to the sleeve 6. Furthermore, a member 8 is attached to the upper end of the sleeve (indicated as a thrust receiver).
The sleeve, rotor 5, polygon mirror 7, etc. are supported by the weight roller in contact with the upper end of the sleeve.

During rotation, the sleeve 6 contacts the shaft 2 due to the presence of the herringbone groove 2C, and the thrust bearing also rotates in the axial direction due to the axial fluid pressure generated by the part 8. The rotating part floats up.

Note that in FIGS. 1 and 2, reference numeral 9 is a Hall element for obtaining changes in the magnetic field, and reference numeral 10 is a sensor that detects the rotation speed from the black and white notches formed on the surface O of the lower balancer 5a of the rotor 5. Then, the stator coil current is switched according to the signal change of the Hall element 9, and the sensor 10 KJ:
The tack signal is fed back to maintain a constant rotation.

The smooth motor described above does not require position adjustment of the shaft and bearings, and the entire motor has ball bearings. The type of V used can also be made smaller and has the advantage of making the rotating parts lighter, making it suitable for use in image forming apparatuses as described above. As is clear from the figure, the rotating part is free in at least one direction, so when used horizontally, for example, the rotating part is free in the thrust direction (
dEasy to become unstable, and even when used vertically,
It is necessary to increase the thrust load capacity against vibrations in the thrust direction, and the selection range of groove shape and rotation speed is difficult to overcome.

The present invention has been made in view of the above-mentioned situation, and is a dynamic pressure bearing for a rotating or driving device used in high-speed rotating equipment. The purpose is to provide a bearing with high axial stability by increasing the load rigidity in the thrust direction by generating force in the direction opposite to the direction in which the rotating member is displaced and floated relative to the fixed member of the bearing during operation. That is.

Hereinafter, the present invention will be described as a vertically arranged dynamic pressure bearing for rotating a polygon mirror at high speed, which is used in laser printer scanners, copying machines, etc. The rotating polygon mirror device attached to the rotor side of the motor to be used will be explained with reference to FIG.

The hydrodynamic bearing shown in Fig. 6 has a rotating sleeve arranged on a fixed shaft with grooves formed in its entirety, and the overlapping portion of the shaft and sleeve is approximately the entire (5-type) in which the bearing function is exerted over the entire area. For those who are using the 7L in a vertical arrangement, this type has a fixed sleeve 1111k, a rotatable shaft with a rotating member on the shaft side, and fixed support parts near both ends of the shaft. Of course, the present invention can also be applied to configurations in which the opposing surfaces of the rotating shaft and the supporting member are formed as dynamic pressure bearings.

Figures i+n are side sectional views of the aforementioned rotating polygon mirror device.

At the center of the bottom of the bottomed casing 1, a shaft 2 with grooves carved on its outer circumferential surface is fixedly installed, and on the inner circumferential surface of the casing (an armature coil 4 serving as a stator is disposed). Id,
The sleeve 6 is arranged around the n1 while maintaining a minute gap n1.
A thrust bearing member 8 is fixed to the top of the sleeve, and a portion of the thrust bearing rests on the end face of the shaft 1 to support the sleeve 6. A permanent magnet 5 serving as a rotor is attached to the sleeve 6 at a position facing the armature coil 4.
, and a multifaceted border 7 is fixed on the top of it. The casing 1 is covered with a cover 6, which seals the above-mentioned bearing portion and all other parts.

= 6- In the motor having such a configuration, in the illustrated one, the longitudinal center of the armature 4 is a distance d from the longitudinal center of the permanent magnet 5, and the thrust receiver is spaced n from the member 8.
It is biased in the direction of Since the magnet 5 is magnetized in a circumferential direction, by arranging it in a biased manner, the sleeve 6 containing the permanent magnet 5 and the polygon mirror 7 have a distance (1, in the direction where f is zero, that is, in the downward direction in the figure). Magnetic force will come into play.

In the configuration shown in the figure, the size of the
When the surface magnetic flux of the magnet of φ is 1200 G and d is 5 mrn, it becomes about 20 Q g, and considering that one pupil of the rotating part including the sleeve 6, permanent magnet 5, and polygon mirror 7 is about 300 g, the weight is quite large. It will be in the same state as when it was added.

With this configuration, it goes without saying that the amount of floating of the thrust receiver from the shaft end surface of the part 8 during driving of the motor is reduced, but the larger the amount of floating, the better. As long as the floating state is ensured, it is preferable to have less fl, and the action of the magnetic force increases the load rigidity in the axial direction, thereby increasing the stability in that direction.

In this case, in addition to the military song of the other rotating parts, the thrust receiver is placed on the shaft 1 by the magnetic force (as described above).
This will be applied as a pressure contact force on the end face of the Or by this rotating polygon device? It is very important to maintain durability by keeping the motor running at full speed even when the device itself is not operating.

The embodiment in which the bearing is arranged vertically has been described above.
It is easy to understand that even when the bearing is arranged horizontally or in a direction close to this direction, it can contribute to the axial stability of the rotating part.

Furthermore, by completely changing the value of the aforementioned deflection amount d, it is possible to adjust the force acting in the thrust direction regardless of the performance of the motor.

Furthermore, the present invention can be applied to an outer rotor motor in which the rotor is arranged outside the stator, and also to a brush motor in which the identification side is made up of a circumferentially magnetized magnet and the rotating side is made up of an armature coil. It is obvious that the present invention can also be applied to an AC hysteresis motor, since the stator acts in the same way as a magnet when energized.

The part indicated by reference numeral 9 in Fig. 6 is a comprehensive representation of the Hall element, sensor, etc. for detecting and controlling the rotation of the motor, and these parts I are located near the bottom of the casing. However, in the case shown in the figure, the stator 4 is located below and the rotor side is not raised unnecessarily, so it is easy to install it in the space above the stator. By configuring this, it is possible to prevent the Hall element and the like from being damaged by the rotor side member during assembly or repair of the motor.

As explained above, the present invention uses dynamic pressure bearings (~,
In this motor having a rotor on the rotating member side of the bearing and a stator on the fixed member side, 9- a direction opposite to the direction in which the rotating member of the bearing is displaced and separated from the fixed part when the morph is activated; Since the relative position of the stator in the longitudinal direction with respect to the rotor is biased so that magnetic force acts on the bearing, a force acts on the rotating member floating during operation to restrain it in the axial direction. This increases the load rigidity in the thrust direction of the bearing, which has the effect of increasing the stability of the bearing in the thrust direction.In particular, it reduces the vibration fL of printers, scanners, videos, discs, etc., which greatly contributes to obtaining high-quality images. .

[Brief explanation of drawings]

1 and 2 are sectional views of a rotating polygon mirror device using a motor using a known dynamic pressure bearing, and FIG. 6 is a sectional view of a rotating polygon mirror device according to an embodiment of the present invention. 1...Casing, 2...Shaft, 6...Sleeve, 4゛Passator (armature coil), 5...
・Rotor (permanent magnet), 6...Cover, 7.
・Polygon Mi7-18...Thrust receiver is a member, 9
...control means-10 = @1i! 1 □・1113t"1 1N - 2

Claims (1)

[Claims] A bearing in which a stator and a rotor of a motor are preliminarily displaced relative to each other in the rotor axis direction, and when the rotor rotates, a magnetic force is applied in a direction to completely eliminate the displacement.