JPH0327747A - Rotational driving gear for polygon mirror - Google Patents

Abstract

PURPOSE:To contrive the miniaturization so as to suppress swivel motion by securing a magnet to the cylindrical internal peripheral surface of a rotary unit and arranging a driving coil opposedly to this magnet while constituting a dynamic pressure bearing in an opposed surface part between the peripheral of the before described rotary unit and a fixed bearing. CONSTITUTION:A rotor 7 is secured to a stepped part in an end plate 8 to form a closed part, and after a mirror mounting part is constituted in this closed part, a magnet 9 is fixed to the internal peripheral surface of the rotor 7. Next a magnet 10 is mounted to the periphery of the end plate 8, and a thrust adjusting screw 13 is screwed to the center part of the end plate 8. While a magnet 14 is mounted to the lower surface center part of the end plate 8, and a polygon mirror is fixed to an upper surface of the end plate 8. The base end part of a fixed bearing 11 is secured to a stepped part in a base 17. A stator core 21 and a driving coil 22 correspond to a fixed part in a rotational driving gear for the before described polygon mirror.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a polygon mirror rotation drive device using a hydrodynamic air bearing, and more particularly, to a polygon mirror that can be applied as a cantering source for a polygon mirror. This relates to a rotary drive device. (Conventional technology) Conventional technology 1. Conventionally, there is a polygon mirror rotation device for rotating a polygon mirror for optical scanning that uses a dynamic pressure air bearing, and its configuration is shown in FIG. 4, for example. In the figure, reference numeral 1 indicates a rotating body, on the lower end side of which an annular magnet 2 is arranged inside the stator 5 and coil 6, and on the upper end side there is a groove (air W
) A disk-shaped thrust bearing 3 in the shape of G and a polygon mirror M for optical scanning are respectively attached. The figure shows a case where the rotating body 1 is in a rotating state, and due to the rotation of the rotating body, the thrust bearing 3 is moved to the fixed bearing 4 surrounding the rotating body l.
It floats up by the gap t and is balanced with the thrust load. In addition to the one shown in the drawings, this type of rotary motion device forms a groove on the outer circumferential surface of a fixed bearing to form a bearing, and a rotating body is fitted onto the outer circumferential surface with a gap, and a groove is formed on the outer circumferential surface of the fixed bearing. The rotary body 1 is rotated along the inner periphery of the fixed bearing 4 by either rotating the rotary body or attaching a magnet to the center or end of the rotary body l having a groove as shown in the figure. All of these structures perform the bearing function by generating dynamic pressure in the air layer on the bearing surface, but the dynamic pressure is related to the circumferential speed of the rotating body surface with grooves, so in order to obtain a large dynamic pressure, it is necessary to Requires a large shaft diameter. Therefore, in order to obtain the required hydrodynamic air bearing function, a fixed bearing diameter or rotating shaft diameter of a certain size is required. Therefore, there is a large space loss in this area, and in order to obtain the same bearing characteristics as a normal rotary active device, the external dimensions of the rotary drive device must be increased. Conventional technology 2. Furthermore, Japanese Patent Application Laid-Open No. 55-139051 discloses a motor structure in which a spiral groove is provided on the outer periphery of the rotor and acts as a dynamic pressure gas bearing, and a motor moving part is disposed inside the spiral groove. (Problems to be Solved by the Present Invention) In the above-mentioned prior art 1, the shaft diameter of the rotating body and the diameter part of the fixed bearing are so-called dead spaces and are not utilized at all, and therefore a large dynamic pressure is applied. The more you try to achieve this, the more the efficiency of space utilization will decline. Further, in the prior art 2, only the motor structure is disclosed, and there is no description regarding attachment with a mirror, but assuming that the combination with a mirror is assumed,
Simply fixing the mirror to the motor shaft does not provide perpendicularity to the axis of rotation, so it is necessary to first fix a mounting seat for attaching the mirror to the motor shaft, and then fix the polygon mirror to this mounting seat.

However, even with this configuration, the motor bearing and the part of the polygon mirror including the mounting seat rotate while being separated in the axial direction, so the motor rotor and the mounting seat are interfering with each other. The center of gravity of the rotating body, including a portion of the polygon mirror, moves from the center of the bearing toward the mirror side that includes the mounting seat, causing the rotating body to perform a sliding motion. This sliding motion of the rotating body causes rotational deflection in the bearing, and there is a risk that both ends of the dynamic pressure bearing surface may come into contact with the stationary bearing surface, resulting in a seizure phenomenon. be. SUMMARY OF THE INVENTION An object of the present invention is to provide a polygon mirror rotational movement device that can effectively utilize space and further reduce the size of the device, while at the same time suppressing slicing motion. (Means for Solving the Problems) In order to achieve the above object, the present invention provides a fixed bearing having an open end and a cylindrical inner circumferential surface formed inside the fixed bearing, and a fixed bearing having a cylindrical inner circumferential surface. a cylindrical rotating body disposed in the space formed, one end side being open and a cylindrical inner circumferential surface being formed inside, and a closed part on the opposite side from the open one end side serving as a mirror mounting part; , a polygon mirror fixed to the closed portion of the cylindrical rotating body so as to protrude beyond the space formed by the cylindrical inner circumferential surface of the fixed bearing; A hydrodynamic bearing is formed by providing a groove on either the surface or the cylindrical inner circumferential surface of the fixed bearing that rotatably fits and supports the cylindrical outer circumferential surface of the cylindrical rotating body, while the cylindrical rotating body A magnet is fixed to the cylindrical inner peripheral surface of the body, and a driving coil is arranged opposite to the magnet to constitute a motor section inside the cylindrical rotating body, and the motor section drives the cylindrical rotating body. By rotating it, the polygon mirror fixed to the closed part of the cylindrical rotating body is rotated. That is, in order to locate the power source of the rotary motion device in the inner part of the rotary body, which has conventionally not been used as a dead space, a magnet is fixed to the cylindrical inner peripheral surface of the rotary body, and the magnet The present invention is characterized in that a driving coil is disposed facing the rotating body, and a dynamic pressure bearing is constructed on the opposing surface between the outer periphery of the rotating body and the inner periphery of the fixed bearing. (Structure) A detailed description will be given below based on an embodiment of the present invention. The configuration of the polygon mirror rotation drive device according to the present invention is shown in Fig. 1. In the figure, reference numeral 7 indicates a rotor which is a cylindrical rotating body, and is made of a soft magnetic material such as mild steel, and has an outer peripheral surface with a surface roughness of 0.2.
After finishing with S or less, cylindricity of 0.5μm or less, and roundness of 0.5μm or less, grooves G (see Figure 2) are formed on the outer circumferential surface using methods such as etching to further improve wear resistance. The surface has been treated for this purpose. This rotor 7 has its upper end fitted into a stepped portion of a flange-like end plate 8 and fixed thereto to form a closed portion, and a mirror mounting portion is formed in this closed portion. After having such a configuration, additional machining is performed to ensure the accuracy of the perpendicularity between the end plate 8 and the rotor 7, etc. Thereafter, a cylindrical magnet 9 is fitted and fixed onto the inner peripheral surface of the rotor 7. Note that if the rotor 7 is made of a non-magnetic material, a yoke is constructed around the outer periphery of the magnet 9. In this example, since the rotor 7 is made of a magnetic material, it functions as a yoke, and there is no need to use a special yoke material as described above. Next, a multi-pole magnetized annular magnet 10 is attached to the outer periphery of the end plate 8. This magnet IO is provided at the upper end of a fixed bearing 11, which will be described later, and is arranged to face a detection coil 12, and functions to generate a rotation speed detection signal for controlling the rotation speed of a rotating body such as the rotor 7. Figure 2 shows the rotor assembly assembled in this way. In the figure, a large number of grooves G for dynamic pressure bearings are formed on the outer peripheral surface of the rotor 7. Note that even if the groove G is formed not on the outer circumferential surface of the rotor 7 but on the inner circumferential surface of the fixed bearing 11, the required dynamic pressure bearing function can also be obtained. A thrust adjustment screw 13 having a curved tip is screwed into the center of the end plate 8. Further, an annular magnet l4 is attached to the center of the lower surface of the end plate 8 with its center aligned. Further, on the upper surface of the end plate 8, a polygon mirror M is mounted with screws 15. It is tightened and fixed with 16 etc. Here, the polygon mirror M is fixed at a position projecting upward from the space formed by the cylindrical inner peripheral surface of the fixed bearing 11. In the rotor assembly section constructed in this way, the rotor 7 is fitted into the hollow portion of the fixed bearing 1l, thereby constructing a polygon mirror rotating device. The fixed bearing 11 has a cylindrical shape, has a cylindrical inner circumferential surface formed inside with one end open, and its base end is fitted into and fixed to the stepped portion of the base 17. The rotor 7 is mounted on the fixed bearing l1
A cylindrical inner circumferential surface is formed in the interior with one end side open, and
The closed part on the opposite side to the open end mentioned above is the mirror mounting part. The inner circumferential surface of the fixed bearing 11, that is, the circumferential surface portion facing the outer circumferential surface of the rotor 7, is finished with the same precision as the outer circumferential surface of the rotor 7, and is subjected to a surface treatment for wear resistance. Incidentally, when the rotor 7 is fitted, the bearing clearance with the fixed bearing l1 is set to about 2 to 7 μm on one side. The band-shaped groove 17a provided on the inner periphery faces the band-shaped groove 7a formed on the outer periphery of the rotor 7, and these grooves are connected to the hole 1 that communicates the inside and outside of the rotor 7.
Together with 7b, it is used for air circulation in the hydrodynamic bearing. base l
The lower end of a column 18 is inserted through the center of the column 7 and is attached by tightening with a nut N, and a disk-shaped thrust plate 19 is fixed to the tip of this column 18. Furthermore, an annular magnet 20 is disposed on the outer circumferential portion of the thrust plate 19 so that the same magnetic pole as the magnet l4 faces.
is fitted and fixed. A stator core 21 formed by laminating multiple layers of plates made of magnetic material is attached to the support column 18, and a pulsation coil 22 is provided around the outer periphery of the stator core 21 by winding. This driving coil 22 faces the magnet 9. The stator core 21, the moving coil 22, etc. correspond to the fixed part of the rotational movement device for the polygon mirror, and together with the rotor and magnet 9 as rotating parts, constitute the rotational drive source of the rotational movement device for the polygon mirror. ．． Here, the fixed bearing 11 is stationary and covers the rotating body, so it also functions as an outer frame of the rotary moving device. In such a configuration, the rotor assembly includes like-polarity opposing magnets 14. A levitation force is exerted by the magnetic repulsion between the two parts, and the frictional force at the contact area is reduced. Note that by utilizing the attraction force between the stator core 21 and the magnet 9, the magnet 14. It can also be replaced with 20. The position in the thrust direction is adjusted by rotating the thrust adjustment screw 13 to change the distance between the magnets 14 and 20. Next, a circuit board 23 on which a magnetic sensor and some circuit components are mounted is placed on the upper surface of the base 17, and the lead wires are connected to the grooves 24. 25 etc. to the outside. Screw hole 26 formed in the base. 27 and the like are provided for attaching a rotating active device for the polygon mirror.

The entire device is covered with a cover 28 to protect it from dust.
It is sealed. In this configuration, since the rotating part of the polygon mirror rotating device is located inside the rotor 7, the space loss around the central axis is significantly improved compared to the conventional technology. ．． Furthermore, for example, the space occupied by the support column 18 is not structured such that the support column itself receives a radial load, so a shaft with a small diameter is sufficient, or it is possible to eliminate the support column itself. Moreover, when compared with the prior art shown in FIG.
Since the length in the axial direction can be increased, the effective surface area is greatly improved compared to conventional rotary drive devices of the same size, and when compared with the same rotary drive device output, it is significantly smaller. It is possible to In this example, when compared with the conventional example at the same torque and rotational speed, the diameter of the hydrodynamic bearing part is larger, so the load on the bearing is significantly improved, and the hydrodynamic effect is maintained even at a relatively low rotational speed. Obtainable.

Furthermore, since the rotor 7 serves as both a bearing and a magnetic yoke, it is advantageous in terms of cost reduction. Others, stator core 21. Since the magnet 9, rotor 7, bearing section, etc. can be configured by simply fitting cylindrical parts, the overall structure is extremely simple, and assembly is easy, reducing costs. Since it is placed on the outer periphery of the rotary motion device, the rigidity of the entire rotary motion device is increased and it has the advantage of being less susceptible to vibrations. In the above embodiment, the rotor 7 and the end plate 8 are constructed by combining separately manufactured parts, and it may be difficult to maintain the accuracy of the perpendicularity between them during assembly. This accuracy affects the accuracy of the polygon mirror mounted on the end plate 8. Therefore, if it is difficult to achieve the precision of the above-mentioned perpendicularity, it is effective to manufacture these parts as one piece. An example is shown in Figure 3. In the figure, the reference numeral 70 indicates a rotor which is a cylindrical rotating body manufactured by machining the rotor 7 and end plate 8 in the above example from a single piece of material. In such a rotor 70, a polygon mirror M is provided at the bottom of the cylindrical rotating body, that is, at the closed part, and it is possible to improve the accuracy of the perpendicularity between the rotor side surface a and the surface b that receives the loaded object. Ideal for mounting polygon mirrors M that require precision.

In this example, the magnet 400 for generating a rotational speed detection signal and the detection coil 120 are respectively arranged inside the rotor 70. In this example, a further device is used to enable adjustment of the height position of the polygon mirror M. The idea is that the tip of the adjustment screw 130 is received by the head 30a of the second tA adjustment screw 30 screwed into the upper end of the support column 180. If you do this, magnet 14.
14. Optimal magnet that balances the repulsive force between the rotor 70 and the gravity of the rotor 70 and its loaded objects. Adjustment can be made by simply rotating the second adjustment screw 30 and changing its height position without changing the interval between the two.

The configuration other than the above in this example is similar to the configuration shown in FIG. 1, and to avoid complication, parts with the same functions as in FIG. (Function) In the present invention, a magnet is attached to the inner surface of the cylindrical rotor, and the drive source configuration of the rotation active device of the polygon mirror is implemented inside the rotor, so that the space around the center axis of the rotation drive device of the polygon mirror is reduced. Loss is greatly improved. (Effects of the Invention) In this way, in the present invention, in order to effectively utilize the unused internal space of the rotor, the drive source of the polygon mirror rotation trapping device is arranged, so that the polygon mirror rotation trapping device can be adjusted accordingly. It is possible to reduce the size of the Furthermore, in the present invention, the polygon mirror is provided in the closed part of the cylindrical rotating body whose outer peripheral surface is used as a dynamic pressure bearing part and the motor part is arranged in the inner peripheral part, so that the dynamic pressure bearing part This allows the mirror to be brought as close as possible to the maximum, thereby suppressing the sliding motion of the rotating body that causes seizure of the bearing. Furthermore, in the present invention, since the mirror is attached to the closed part of the cylindrical rotating body whose outer peripheral surface is used as a dynamic pressure bearing part and whose inner peripheral part is arranged with a motor part, a separate mirror mounting seat is required. There is no need to provide one. Furthermore, since the cylindrical rotating body of the present invention has a motor section incorporated therein and its outer peripheral surface is used as a bearing surface, the diameter of the cylindrical rotating body can be made relatively large, and as a result, The closed part of the cylindrical rotating body, that is, the mirror mounting surface, can be made larger. Therefore,
The perpendicularity of the mirror mounting surface to the rotational axis of the motor can also be configured with high precision, which is advantageous because deflection of the mirror can also be suppressed.

[Brief explanation of drawings]

FIGS. 1 and 3 are cross-sectional views of a polygon mirror rotary motion device illustrating embodiments of the present invention, FIG. 2 is a front view of a rotor, and FIG. 4 is a conventional polygon mirror rotary motion device. This is a sectional view of the main parts. 7,70... rotor, 9.
... Magnet, 11... Fixed bearing, 22... Drive coil, G... Groove, M... Polygon mirror

Claims (1)

[Scope of Claims] A fixed bearing having a cylindrical inner circumferential surface formed inside with an open end, and a fixed bearing disposed in a space formed by the cylindrical inner circumferential surface of the fixed bearing, with an open end and an inner a cylindrical rotating body in which a cylindrical inner circumferential surface is formed, and a closed part opposite to the open end side serves as a mirror mounting part; and the fixed bearing is attached to the closed part of the cylindrical rotary body a polygon mirror fixed to protrude beyond the space formed by the cylindrical inner circumferential surface of the cylindrical rotating body; A groove is provided on either one of the cylindrical inner circumferential surfaces of the fixed bearing that is freely fitted and supported to form a hydrodynamic bearing, while a magnet is fixed to the cylindrical inner circumferential surface of the cylindrical rotating body, A motor section is configured inside the cylindrical rotating body by arranging a driving coil facing the magnet, and the motor section rotates the cylindrical rotating body to be fixed to the closed part of the cylindrical rotating body. A polygon mirror rotation drive device configured to rotate the polygon mirror.