JPS6356158A - Motor unit - Google Patents

Abstract

PURPOSE:To enable turning a rotator with a small sliding resistance by generat ing a dynamic pressure between both end faces of the rotator through its rota tion so as to make said rotator levitate. CONSTITUTION:A ceramic rigid shaft 51 is fastened to a supporter stand 21. Said supporter stand 21, epoxy resin 27, stator coil 25 and an end face member 70 composed of hard ceramic are bonded and fastened together into an integral body. A rotator 61 is manufactured by lamination of a permanent magnet as a rotor magnet 79 between upper and lower ceramic plates 62 and 63. Grooves for generating dynamic pressure are formed on both faces of the rotator 61 and the dynamic pressure is generated through rotation of said rotator 61 to make it levitate.

Description

[Detailed Description of the Invention] [Industrial Application Definition] The present invention relates to a motor unit used in laser printers, barcode leagues, etc., and more specifically, a motor unit equipped with a polygon mirror that scans a laser beam. Regarding.

[Prior Art] FIG. 12 is a schematic diagram of a laser scanning optical system used in a laser printer.

In the scanning of the laser beam, a laser beam from a laser unit 11 consisting of a semiconductor laser, a gas laser, etc. is reflected by a polygon mirror 12 and irradiated onto the surface of the photoreceptor drum 13. Here, the polygon mirror 12 is driven. Rotated by motor '15, polygon mirror 12
The laser beam reflected by the photosensitive drum 13 is irradiated over the entire width of the photosensitive drum 13 so as to scan the photosensitive drum 13. Note that a correction lens 17 is provided between the laser unit 11 and the polygon mirror 12 and between the polygon mirror 12 and the photosensitive drum 13.

Further, the signal of the image formed on the photoreceptor drum 13 is transmitted from an image signal processing circuit (not shown) to a laser input/exit window (11).
The on/off and strength of the laser beam is adjusted to irradiate the photoreceptor drum 13 with the desired laser beam to form an image.

FIG. 13 is a longitudinal cross-sectional view of a motor unit 20 in which the polygon mirror 12 and drive motor 15 of FIG. 12 are incorporated.

In FIG. 13, reference numeral 21 denotes a support base screwed to a fixing member (not shown), and a substantially cylindrical outer cylinder 22 is fixed to the support base 21 via an O-ring 35. A cap 41 is similarly screwed to the upper part of the outer cylinder 22 via an O-ring 36. Further, a cylindrical fixed shaft 51 is fixed to the center of the support base 21, and the upper end of this fixed shaft 51 extends to the vicinity of the cap 41. Further, a large number of grooves for generating dynamic pressure are formed on the outer circumferential surface of the fixed shaft 51, so that rotation of the rotating sleeve 71 generates dynamic pressure for supporting thrust loads and radial loads.

Functionally, this dynamic pressure generation groove generates dynamic pressure by a lower groove 52 having a herringbone shape, and a middle groove 53 and an upper groove 54 forming a herringbone shape to support a radial load, and Air is fed into the upper surface of the fixed shaft 51 through the middle groove portion 53, thereby increasing the air pressure between the fixed shaft 51 and the thrust bearing 75 to support the thrust load.

A polygon 81 is screwed to the L portion of the rotating sleeve 71, a rotor magnet 79 is fixed to the lower part with adhesive, and a balance ring 72 is further fixed.

A plate-shaped thrust bearing 75 with an air hole 76 formed in the center is fixed to the end of the rotating sleeve 71, and the upper end surface of the fixed shaft 51 facing the thrust bearing 75 is finished into a smooth plane. ing. Further, a laser entrance/exit window 23 transmits the laser light irradiated from the outside onto the mirror part 85 of the polygon 81 and the laser light reflected to the desired exposure surface.
is attached to a part of the upper circumferential surface of the outer cylinder 22, and a stator coil 2 for driving the rotor magnet 79 is attached to a part of the upper peripheral surface of the outer cylinder 22.
5 is fixed so as to surround the rotor magnet 79.

Note that 31 is a Hall element for detecting the rotation speed of the rotating sleeve 71, that is, the polygon 81, and a signal from the Hall element is guided to the outside by a signal pin 33. Also, 3
2 is a power bin for feeding power to the stator coil 25.

In this motor unit 20, when the start switch of the control circuit (not shown) is turned on, the Hall element 31
The output signal is read into the control circuit, and power is supplied from the power bottle 32 to the stator coil 25 in order to bring the polygon 81 to a predetermined rotational speed. In this way, the polygon 81 that rotates at high speed not only needs to maintain high rotational accuracy, but also has to minimize the surface runout of the reflective surface, so the gap between the fixed shaft 51 and the rotating sleeve 71 must be extremely small. It is considered narrow.

Therefore, the rotating parts such as the rotating sleeve 71 and the polygon 81 are sealed by the outer cylinder 22 and the cap 41 in order to prevent foreign matter from entering the sliding parts with such minute intervals.

The motor unit 20 shown in Fig. 13 is for driving the polygon mirror 12, which is suitable for high-definition image processing, but if high definition is not required, such as in a barcode reader, it is necessary to have a sealed structure. There isn't.

[Problems to be Solved by the Invention] Since the above-mentioned laser printer reproduces a clear image on a photoreceptor drum at a high speed, the polygon mirror can be used at a high speed and the reflective surface is less likely to fall. Must be rotated in the state.

Furthermore, since the laser entrance/exit window is easily contaminated by lubricating oil, there is a restriction that lubricating oil cannot be used for the bearing. For these reasons, the sliding part between the fixed shaft and the rotating sleeve is machined with extreme precision to effectively generate dynamic pressure from air, and the sliding part of the rotating sleeve, polygon, part of the mirror, and rotor magnet is The rotating parts are precisely machined, and at the same time, the mass balance is suitably adjusted.

However, the inclination of the reflective surface of the polygon mirror is ±1.
In order to achieve a weight of 5 gm or less, a fixed shaft with a length of 50 m or more must be precisely machined and the distance between it and the rotating sleeve must be 3 pm or less, making mass production of the product difficult.

In addition, when performing even higher speed image processing, the rotation speed of the polygon mirror should be increased to 30. Although it is desired to increase the rotation speed to OOO rpm or more, such high-speed rotation increases the radial load on the fixed shaft, making it extremely difficult to support it with an air film.

The present invention solves these drawbacks, accurately reflects laser light, etc. using a polygon mirror with a simple structure, and furthermore,
This was done to enable high-speed rotation.

[Means for Solving the Problems] The present invention provides a rotating body having a flat plate shape with a through hole formed in the center, the rotating body having a plurality of mirror surfaces whose outer periphery is a regular polygon. , a fixed shaft passing through a through hole of the rotating body, and a stator coil fixed in parallel with the flat rotating body, and a permanent magnet or a secondary conductor provided on the rotating body. A motor unit for rotating a rotating body with the stator coil, wherein a surface of the rotating body facing the stator coil and an end face of the stator coil side fixing portion facing the rotating body are each made of a hard ceramic material, and This motor unit is characterized in that a groove for generating dynamic pressure is formed on one of the two surfaces. A pressing plate capable of pressing the rotating body toward the stator coil is provided in the direction opposite to the stator coil of the rotating body, and the surface of the rotating body facing the pressing plate and the flat surface of the pressing plate facing the rotating body are also hard. A groove for generating dynamic pressure may be formed either on the plane of the pressing plate facing the rotating body or on the plane of the rotating body facing the pressing plate.

[Function] The motor unit of the present invention rotates a rotating body, which is a polygon mirror to which a permanent magnet or a secondary conductor is fixed as a rotor magnet, by a magnetic field formed by a stator coil arranged parallel to the rotating body. The sliding parts between the rotating body around which the polygon mirror is formed and the stator coil, which is the fixed side member, are each made of a hard ceramic material, and there are grooves on either side for generating dynamic pressure. , the rotor is suspended and rotated by the dynamic pressure of the fluid generated by the groove for generating dynamic pressure. Further, since the fluid film formed at this time has a damping effect, the rotating body is stably held over the entire large sliding surface, and the deflection of the mirror surface can be significantly reduced.

When a pressing plate is provided, the rotating body is held between the stator coil-side fixing portion end face member and the pressing plate, and the deflection of the mirror surface during rotation can be further reduced and stabilized.

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

FIG. 1 is a longitudinal sectional view of a motor unit 20 of the present invention.

In FIG. 1, reference numeral 21 denotes a support base which is screwed to a fixing member (not shown), and a substantially cylindrical outer cylinder 24 is fixed to the support base 21 via an O-ring 37. Further, a cap 41 is also fixed to the upper part of the outer cylinder 24 via an O-ring 37 by a hook (not shown).

The center of the support base 21 is made of hard ceramic (for example, SiC).
, Si3N4) is fixed, and a solenoid 42 is also screwed into the center of the cap 41 and fixed. The circumferential surface of the fixed shaft 51 fixed to the support base 21 is processed to have a satin finish in a portion corresponding to the stator coil 25, thereby enhancing adhesiveness with the stator coil 25. Further, the stator coil 25, which is formed by laminating sheet-like coils, has an element for detecting the magnetic pole of a permanent magnet as a rotor magnet 79 fixed to the rotating body 61, which is laminated integrally with the coil on its upper surface. These details are not shown.

27 is an epoxy resin plate for increasing the insulation between the stator coil 25 and the support base 21;
1. Epoxy resin board 27. The stator coil 25 and an end face member 28 made of hard ceramic (for example, α-3iC ceramic) covering the upper surface of the stator coil 25 are bonded and fixed together. Here, the fixed shaft 51 and the fixed portion end face member 28 are accurately positioned so as to be perpendicular to each other.

The rotating body 61 has a magnet as a rotor magnet 79 between an upper ceramic plate 62 and a lower ceramic plate 63.
The polygon mirror 12 is made of an L layer, and the upper ceramic plate 62 has a mirror surface around the upper ceramic plate 62 to form a mirror portion 85.

Further, a spring 43 is disposed around the solenoid 42 fixed inside the cap 41, and the spring 43
The pressing plate 45 is pressed against the rotary body 61 by the pressing plate 45, in which the ceramic plate 48 on the lower surface is pressed against the rubber plate 47.
With the pressing force of the spring 43 via the iron plate 46, substantially the entire upper surface of the rotating body 61 is evenly pressed.

In addition, when the rotating body 61 is started, the iron plate 46 on the upper surface of the pressing plate 45 is connected to the solenoid 42 by energizing the solenoid 42.
By suctioning, the pressing plate 45 is lifted and the thrust load on the rotating body 61 is eliminated.

Both surfaces of the rotating body B1, the surface of the ceramic end member 28 fixed to the surface of the stator coil 25, and the surface of the ceramic plate 48 on the lower surface of the pressing plate 45 are each finished to be smooth and have little waviness. Further, grooves 81 for generating dynamic pressure are formed on both sides of the rotating body 61.

FIG. 2 is a plan view of the rotating body 61, in which the surface of the upper ceramic plate 62 is smooth as described above and has zero waviness over the entire surface.
Maximum surface roughness (Rwax) is 0 at 3 gm or less
．． Smooth plane of 5 gm or less, groove depth 3 to 10
A spiral groove portion 91 for generating dynamic pressure of g and m is formed. In addition, a through hole 6 formed in the center of the rotating body 61
5 is surrounded by an annular land 93 having the same height as the spiral land 92 adjacent to the spiral groove 91.

Furthermore, the through hole 65 of the rotating body 61 is provided with a rotor magnet 79.
The permanent magnet, the upper ceramic plate 62, and the lower ceramic plate 63 have a cylindrical shape that is almost a perfect circle,
It is perpendicular to the surfaces of the upper ceramic plate 62 and the lower ceramic plate 63.

Similarly to FIG. 2, grooves for generating dynamic pressure are formed on the surface of the lower ceramic plate 63, the surface condition is the same, and the spiral direction is opposite.

FIG. 3 is a partial cross-sectional view of the rotating body 61, in which an upper ceramic plate 82, a rotor magnet 79, and a lower ceramic plate 63, each of which has a regular hexagonal shape, are glued together and made into one body. The end face 64 of the mirror is polished to a very smooth mirror surface and constitutes a mirror portion 85.

Further, FIG. 4 is a plan view of the rotor magnet 79,
In this embodiment, a 6Th permanent magnet is used.

In FIG. 1, a herringbone-shaped groove 55 is formed on the peripheral surface of the fixed shaft 51 corresponding to the rotating body 61.
Dynamic pressure is generated by the rotation of the rotating body B1, and the radial load is supported.

In the above-mentioned embodiment, upon startup, first the solenoid 42 is energized, the upper pressing plate 45 is lifted, and then the power is applied to the stator coil 25 so that the zero-rotating body 61 that rotates the rotary body 61 reaches a predetermined rotation speed. After reaching the stator coil 25 or after a certain period of time has elapsed after the power is turned on to the stator coil 25, the current of the solenoid 42 is cut off or gradually lowered, and the pressing plate 45 is lowered to press against the rotating body 61.

In this state, the rotating body 61 is held between the pressing plate 45 and the end member 28, and the sliding portion between the pressing plate 45 and the rotating body 61 and the sliding portion between the end member 28 and the rotating body 61 are A fluid film of air is formed, which rotates with very small amplitude in the vertical direction.

In addition, in FIG. 1, the protrusion 49 formed on the cap 41
is a rotation stopper of the press plate 45.

In this way, the rotating body 61 is sandwiched between the pressing plate 45 and the fixed part end member 28 via the fluid film, and there is a gap of about 3 g, m (one side) between the central through hole 65 and the fixed shaft 51. Therefore, dynamic pressure is generated by the belling-pond-shaped groove 55 formed on the circumferential surface of the fixed shaft 51, and the radial load is also supported via the fluid film.

As a method for forming the grooves 91 for generating dynamic pressure on the surfaces of the lower ceramic plate 63 and the upper ceramic plate 62 of the fixed shaft 51 of the ceramic acid and the rotating body 61, first, the surface of the ceramic member is made into a smooth cylindrical surface or a flat surface. After that, resin is attached to the parts other than the grooves by screen printing, hardened, and then shot blasted using alumina or silicon carbide particles to form grooves of a predetermined depth in the exposed parts, Then, it is convenient to remove the resin layer.

5 to 7 are diagrams showing another embodiment of the rotating body 61 shown in FIG. 1, in which the groove for generating dynamic pressure for supporting the thrust load is formed on the end surface of the stator coil side fixed part. They are formed on the surfaces of the member 28 and the pressing plate 45, respectively.

FIG. 5 is a longitudinal cross-sectional view of the rotating body 61, showing the lower ceramic plate 6 constituting the lower end face facing the stator coil 25.
3 is formed integrally with a rotating sleeve 67 having a through hole 65, and an annular rotor magnet 73 is fixed between the upper ceramic plate 62 and the lower ceramic plate 63, and the outer periphery thereof is a metal mirror part 85. ing.

FIG. 6 is a plan cross-sectional view with the upper ceramic plate 62 removed, and the rotor magnet 79 is magnetized to six poles, and the polygon mirror 12 is formed by a regular hexagonal mirror portion 85.

In this embodiment, the -L ceramic plate 62 and the lower ceramic plate 63 extend further to the outer periphery than the polygon mirror 12 and have a structure in which a mirror portion 85 is protected, and are formed above and below the polygon mirror 12. upper ceramic plate 62
and the diameter of the lower ceramic plate 63 by the polygon mirror 12
This upper ceramic plate 62 can be set regardless of the diameter of the upper ceramic plate 62.
Since the lower ceramic plate 63 can support the thrust load while limiting the deflection of the rotating body 61, it is easier to keep the tilt of the mirror surface within a desired range.

Further, since the groove portion 91 for generating dynamic pressure is processed into the end face member 28, which is a ceramic member of the fixing portion, and the ceramic plate 48 of the pressing plate 45, adjustment of the mass balance of the rotating body 61 becomes easier.

FIG. 8 shows another embodiment of the groove shape for generating dynamic pressure, which is a herringbone shape.

In this way, a herringbone-shaped dynamic pressure generating groove 95 with an outer diameter of r2 and an inner diameter of rl is formed in a part of the ceramic plate 62 of the rotating body 61, and the groove 95 is moved clockwise as shown by the arrow in the figure. When rotated, the radii r1 and r2 as shown in Figure 9.
A high dynamic pressure can be generated between the rotating body B1
It can receive thrust loads around the area.

Moreover, FIG. 11 shows the movement in the sliding part when the rotating body 61 is rotated when a spiral dynamic pressure generating groove 91 with an outer diameter of R2 and an inner diameter of R1 as shown in FIG. 1θ is formed. This qualitatively shows the magnitude of pressure generated. In FIGS. 9 and 11, it is assumed that the through hole 65 is open to atmospheric pressure, and the units of the vertical axis are shown as arbitrary.

Although the embodiment of the present invention describes a case in which a six-pole magnetized permanent magnet is used as the rotor magnet 72 provided on the rotating body 61, the number of magnetic poles is not limited to six, and further permanent magnets may be used. The present invention is not limited to the case where the rotor magnet 72 is used, but the induction coil may be formed of a conductive secondary conductor and replaced with the rotor magnet 72.

In addition, the hard ceramic material used in the present invention is preferably a hard ceramic material with a dense structure such as silicon carbide or silicon nitride. In particular, the ceramic material used for the end face of the fixed part on the stator coil side is suitable for reducing eddy current loss. α which added Si3N4 and BeO with high electrical resistance considering the
-8iG is desirable.

[Effects of the Invention] The present invention provides a motor unit in which a permanent magnet and a secondary conductor are fixed to a rotating polygon mirror, and a stator coil is arranged parallel to a rotating body such as a polygon mirror. The sliding parts of the rotating body are made of hard ceramic material, and a yt part for generating dynamic pressure is formed on one of the sliding surfaces, so that the thrust load of the rotating body is supported by the flat surface. Therefore, the rotation of the rotating body generates dynamic pressure between both end faces of the rotating body, causing the rotating body to float, and the rotating body can be rotated with extremely small sliding resistance. The deflection (inclination) of the surface of the rotating polygon mirror is limited by the damping effect of the fluid film formed over the entire planar sliding surface, so it becomes very small.

Furthermore, the sliding surface is made of a hard ceramic material such as SiC, S.
Since it is made of i3"N4, etc., it will not wear out. In particular, since the amount of TiE in the rotating body is small, there will be no wear at all even when it comes into contact with solid objects.

Furthermore, since the deflection of the polygon mirror formed around the rotating body is limited by a plane, the accuracy is high. In contrast, in the present invention, the width of the groove for generating dynamic pressure provided on the fixed shaft is narrowed, and the groove for generating dynamic pressure provided on the end face of the rotating body and the flat surface of the end cap of the fixed part on the stator coil side reduces the load. Since the groove portion for generating dynamic pressure is machined with high accuracy on the flat portion, manufacturing becomes easy.

Therefore, according to the present invention, since the weight of the rotating body is small, it has excellent durability, and since the sliding part is made of ceramic material, the dynamic pressure generation effect is maintained well even under high thrust loads. This is practically useful because it takes a relatively short time to reach a predetermined rotational speed and allows a motor unit with a small surface deflection (inclination) of the polygon mirror to be constructed with a simple mechanism.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 2 is a plan view of the rotating body of FIG. 1, FIG. 3 is a partial vertical sectional view of FIG. 2, and FIG.
The figure is a cross-sectional view of the rotor magnet, Figures 5 to 7 are diagrams showing other embodiments of the rotating body, and Figure 8 is a diagram showing another embodiment of the dynamic pressure generating groove. FIG. 9 is a diagram showing the dynamic pressure generated by the dynamic pressure generating groove, the first O.
11 and 11 are diagrams showing the shape of a spiral dynamic pressure generating groove and the dynamic pressure generated by the groove, and FIG. 12 is a schematic diagram of a laser beam scanning optical system using a polygon mirror, and FIG. FIG. 13 is a longitudinal sectional view of a motor unit incorporating a polygon mirror. 11=laser unit, 12=polygon mirror, 1
3-photosensitive drum, 15=drive motor, 20=motor unit, 22=outer tube, 23=laser entrance/exit window,
24=Outer cylinder, 25=Stator coil, 28: End member, 41=Cap, 42=Solenoid, 45=Press plate, 51=Fixed shaft, 52.53.54.55=Groove for dynamic pressure generation, 61=Rotation body, 62=upper ceramic plate, 63=lower ceramic plate, 65=1τ through hole,
71 = Rotating sleeve, 75 = Thrust bearing, 79 = Rotor magnet, 81 = Polygon, 85 = Part of Mira, 91.95 = Groove for generating dynamic pressure. E 3 Illustration 8 Illustration 9 Illustration

Claims (2)

[Claims] (1) A rotating body that is flat and has a through hole formed in the center, and has a plurality of mirror surfaces whose outer periphery is a regular polygon, and a rotating body that passes through the through hole of the rotating body. The rotating body is provided with a fixed shaft provided as a rotor, and a stator coil fixed in parallel with the flat plate-shaped rotating body, and the rotating body is controlled by a permanent magnet or a secondary conductor provided on the rotating body and the stator coil. A motor unit to be rotated, wherein a surface of the rotating body facing the stator coil and an end surface of the stator coil side fixed part facing the rotating body are each made of a hard ceramic material, and one of the two surfaces A motor unit characterized in that a groove for generating dynamic pressure is formed in the motor unit. (2) A rotating body that is flat and has a through hole formed in the center, the rotating body having a plurality of mirror surfaces whose outer periphery is a regular polygon, and a rotating body that passes through the through hole of the rotating body. a fixed shaft provided as a rotor, and a stator coil fixed in parallel with the flat rotating body, and the rotary body is rotated by a permanent magnet or a secondary conductor provided on the rotary body and the stator coil. The motor unit has a pressing plate that can press the rotating body toward the stator coil in a direction opposite to the stator coil of the rotating body, and further includes an upper surface and a lower surface of the rotating body, and a flat surface of the pressing plate facing the rotating body. The stator coil side fixed part end faces are each made of a hard ceramic material, and a groove for generating dynamic pressure is formed on either the stator coil side fixed part end face facing the rotating body or the rotary body plane facing the stator coil. A motor unit characterized in that a groove for generating dynamic pressure is formed on either one of the plane of the pressing plate facing the rotating body or the plane of the rotating body facing the pressing plate.