JPH05289015A - Mounting structure for polygon mirror - Google Patents

Abstract

PURPOSE:To reduce the number of components and to surely suppress the vibration of a polygon mirror when it is rotated at high speed. CONSTITUTION:The mounting structure of the polygon mirror 36 includes a hub 14 rotated by the driving force of a motor, the polygon mirror 36 mounted on the hub 14 by fitting, and a spring member 46 which holds the polygon mirror 36. Plural pressing parts 52 protruding in the axial direction along the circumferential direction are formed at the outer peripheral part of the spring member 46 consisting of an annular plate member. The spring member 46 is comprised so as to press the polygon, mirror 36 in the axial direction of the hub 14 by each of the pressing parts by mounting the mirror 36 on the hub 14 by fitting, and each of the pressing parts 52 is provided with blade shape so as to increase a pressing force on the polygon mirror 36 by the air flow according to the rotation of the hub 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polygon mirror mounting structure applied to an image forming machine such as a laser beam printer.

[0002]

2. Description of the Related Art A polygon mirror conventionally used for a laser beam printer is attached to a shaft of a hall motor and rotates at a high speed. Also, its rotation speed is
The speed is accurately controlled by the controller. The polygon mirror is made by cutting from an aluminum material, and the polygonal portion formed on the outer periphery thereof constitutes a mirror surface.
In a laser printer, when a rotating polygon mirror is irradiated with a semiconductor laser beam whose light intensity is modulated, the laser beam is reflected in different directions depending on the position of the mirror surface at that moment. As a result, the surface of the photosensitive drum is scanned by the reflected light, and a latent image of print information is formed. The latent image is then developed with toner,
The transfer and fixing action takes place and appears on the medium.

The attachment of the polygon mirror to the shaft of the motor has been performed, for example, by screwing the polygon mirror to the shaft. According to this mounting structure,
It is necessary to form a through hole in the polygon mirror itself and further form a screw on the inner peripheral portion of the polygon mirror, which requires a large number of processing steps, and thus is not suitable for mass production and also increases the cost. Since it is necessary to use an adhesive or the like to prevent loosening of the screw connection, the workability of assembling is not good. Further, there is a risk of damaging the polygon mirror during the tightening work on the shaft. Further, as another mounting structure, a holding preload spring for holding the polygon mirror and a C ring for fixing the holding preload spring, or a combination of a holding preload spring and a cup and a screw for fixing the holding preload spring has been used. According to these mounting structures, similarly, the number of parts is large and the workability is poor. On the other hand, since the rotor is rotated at a high speed of 10,000 rpm or more, a slight imbalance that does not cause a problem at low speed rotation and insufficient pressing force for pressing the polygon mirror on the hub cause vibration of the polygon mirror, which causes the scanning. It will adversely affect the accuracy of. Therefore, it is desirable that the number of parts on the rotor side is as small as possible. However, according to the conventional polygon mirror mounting structure, since the number of parts is relatively large, the risk of vibration is extremely high, and a predetermined number of parts are required. There is a problem that the reliability is not sufficiently ensured at the number of revolutions or more.

[0004]

SUMMARY OF THE INVENTION The main object of the present invention is to provide an improved polygon mirror mounting structure that has a small number of parts and can reliably suppress vibration of the polygon mirror during high-speed rotation. is there.

[0005]

In order to achieve the above main object, according to the present invention, a hub rotated by a driving force of a motor and an outer peripheral portion of the hub at one axial end thereof are fitted and mounted. The hub includes a polygon mirror and a spring member that holds the polygon mirror at a mounting position. An axially protruding boss portion is formed on the one end side of the hub, and at least a part of the periphery of the boss portion is formed. Fitting groove means is formed, the spring member is formed of an annular plate member, a projecting means that fits into the fitting groove means is formed on an inner peripheral portion of the spring member, and the outer peripheral portion of the protruding member is arranged in the circumferential direction. In addition, a plurality of pressing portions that are gradually inclined downward in the rotation axis direction toward the rotation direction of the hub are formed, and the tip end of each of the pressing portions is formed of a bent portion that projects in the axial direction. , Fit the protruding means to the fitting groove means Each of the bent portions provided on the pressing portion presses the polygon mirror in the axial direction of the hub, and when the hub rotates, each pressing portion increases the pressing force on the polygon mirror by the air flow. A polygon mirror mounting structure is provided.

[0006]

When the hub rotates at a high speed while the polygon mirror is fitted and attached to the outer peripheral portion of the hub by the spring member, air passes through the upper surfaces of the pressing portions of the spring member at a high speed. Due to this high-speed air flow, a force that axially presses the polygon mirror is applied to each of the pressing portions. This force increases as the rotor rotates at higher speed, and more firmly presses the polygon mirror against the hub, so that vibration at high speed is reliably prevented. In addition, the spring member is pushed in from the axial direction of the hub, or simply pushed and then rotated, and the projecting means is fitted and held in the fitting groove means of the hub, and each of the pressing portions holds the polygon mirror. Since it is configured to press in the axial direction of the hub, it is easy to attach the polygon mirror.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a polygon mirror mounting structure according to the present invention will be described below with reference to the drawings.

1 to 4 showing an embodiment in which the present invention is applied to an axial flux type brushless DC motor, a polygon mirror mounting structure includes a hub 14, a polygon mirror 36 and a spring member 46 which will be described in detail later. I'm out. Reference numeral 2 is a fixed base of the motor, and a shaft 4 indicated by a chain double-dashed line is fixed upright in the center of the fixed base. An armature coil 6 is annularly arranged on the upper surface of the fixed base 2 on the fixed shaft 4 side. A rotor 8 is rotatably supported on the fixed shaft 4 via a bearing (not shown). The rotor 8 includes a rotor base 10, a rotor magnet (permanent magnet) 12 mounted on the lower surface side of the rotor base 10,
The hub 14 mounted on the upper surface side of the rotor base 10 is included. The rotor magnet 12 is positioned so as to be opposed to the armature coil 6 in a plane at a predetermined interval. A magnet 16 for a frequency oscillator for detecting the rotation speed of the rotor 8 is mounted on the outer peripheral portion of the rotor base 10, while a pickup coil 18 is mounted on the upper surface of the fixed base 2. Pickup coil 1
The magnets 8 are positioned so as to face the magnet 16 in a plane at a predetermined interval.

The hub 14 is made of aluminum and has a cup shape. A through hole 22 is formed in an axial center portion of a wall 20 that defines one end side of the hub 14, and is rotatably fitted and supported by a fixed shaft 4 of a motor via a bearing (not shown). As a result, the rotor 8 is rotatably supported by the fixed shaft 4 of the motor. The hub 14 is formed with an outer peripheral portion 24 into which a polygon mirror 36 described later is fitted and mounted. The outer peripheral portion 24 has a circular cross section and extends in the axial direction from one end side of the hub 14, and the other end thereof is defined by a shoulder (step portion) 26. The shoulder 26 is a right-angled surface extending radially outward from the outer peripheral portion 24. A boss portion 28 protruding in the axial direction is formed on one end side of the hub 14. Fitting groove means is formed on at least a part of the periphery of the boss portion 28. That is, as shown in FIGS. 1 and 4, a predetermined cross-sectional shape (spline shape in this example) is provided around the boss portion 28.
Are formed. Reference numeral 30 indicates a concave portion, and reference numeral 32 indicates a convex portion. An arcuate fitting groove 34 centered on the axis of the hub 14 is formed in each of the protrusions 32. The fitting groove means is constituted by a fitting groove 34 in this embodiment. The outer diameter of the boss portion 28 is smaller than that of the outer peripheral portion 24, and there is a predetermined gap in the axial direction between the fitting groove 34 and the shoulder 26.

A polygon mirror 36 is fitted and mounted on the outer peripheral portion 24 of the hub 14. The polygon mirror 36 includes a polygonal outer peripheral portion 38 and a hub 1 as shown clearly in FIG.
40 having an inner peripheral shape that can be fitted to the outer peripheral portion 24 of
And axially opposite side surfaces 42 and 44 defined by the planes orthogonal to the axis. The polygon mirror 36 is made of aluminum, and each surface of the polygon forms a mirror surface. Although the cross section of the outer peripheral portion 24 of the hub 14 is circular in the illustrated example, it may be replaced by a cross sectional shape that cannot rotate relative to the mating partner. In that case, the hole 40 of the polygon mirror 36 has an inner peripheral shape that can be fitted therein.

Reference numeral 46 is a spring member for holding the polygon mirror 36 at the mounting position. The spring member 46 is formed of an annular plate member (for example, phosphor bronze, spring steel plate or synthetic resin). As shown in FIG. 2, a protrusion means that can be fitted into the fitting groove means is formed on the inner peripheral portion of the spring member 46. That is, the inner peripheral portion of the spring member 46 is formed with an uneven portion that can be fitted into the uneven portion of the boss portion 28. Reference numeral 48 indicates a concave portion and reference numeral 50 indicates a convex portion. The protrusion means is constituted by the uneven portions (48, 50) in this embodiment. Further, a plurality of pressing portions 52 are formed on the outer peripheral portion thereof.
Each of the pressing portions 52 is formed by punching out a predetermined length along the circumferential direction, and the bending portion 5 protruding in the axial direction.
It consists of 2 '. In the spring member 46, the protrusion means (50) is fitted and held in the fitting groove means (34) so that each of the pressing portions 52 causes the polygon mirror 36 to move to the hub 1.
4 is configured to be pressed in the axial direction. That is,
The inner peripheral surface of each of the concavo-convex portions of the spring member 46 and the outer peripheral surface of each of the concavo-convex portions of the boss portion 28 are formed in an arc centered on their axial center. The uneven portion of the spring member 46 is replaced with the boss portion 2.
8, the spring member 46
Of the spring member 4 to the convex portion 32 of the boss 28.
In the state where the convex portions 50 of No. 6 are aligned with the concave portions 30 of the boss portion 28, respectively, by pushing in from one end side of the boss portion 28 in the axial direction to rotate, each of the convex portions 50 of the spring member 46 is changed. Fitting groove 3 formed in each of the convex portions 32 of the
4 is fitted and held. At the same time, each of the pressing portions 52 is configured to press the polygon mirror 36 in the axial direction of the hub 14. In this mounted state, each of the pressing portions 52 has a bent portion 52 ′ at its tip end, which is formed by the polygon mirror 36.
Of the hub 1 while contacting the side surface 42 of the hub 14 and facing the rotation direction of the hub 14 (the direction of the arrow in FIGS. 1 and 2).
The blade shape is such that the pressing force on the polygon mirror 36 is increased by the air flow accompanying the rotation of 4.

The polygon mirror 36 is fitted in the outer peripheral portion 24 from one end side of the hub 14 and is mounted with its side surface 44 pressed against the shoulder 26. Next, with the uneven portion of the spring member 46 aligned with the uneven portion of the boss portion 28,
When pushed in from one end side in the axial direction and rotated by a predetermined angle, each of the convex portions 50 of the spring member 46 is fitted and held in each of the fitting grooves 34 of the boss portion 28 (so-called bayonet coupling). .. As a result, the spring member 46 is prevented from coming off the hub 14 in the axial direction thereof. At the same time, the pressing portion 52 that comes into contact with the one side surface 42 of the polygon mirror 36 bends around the convex portion 50 fitted in each of the fitting grooves 34 as a fulcrum. As a result, each of the pressing portions 52 of the spring member 46 presses the polygon mirror 36 in the axial direction of the hub 14, specifically, the side surface 44 of the polygon mirror 36 is pressed against the shoulder 26. It is firmly attached to the hub 14 only by pushing the member 46 in the axial direction and rotating the member. When the armature 6 is energized, the rotor 8 rotates around the fixed shaft 4 at a predetermined rotation speed. The polygon mirror 36 is rotated together with the hub 14 together with it. Since the rotor 8 rotates at a high speed, the air flows through the spring member 46.
It passes through each upper surface of the pressing portion 52 at high speed. Due to this high-speed airflow, a force that presses the polygon mirror 36 in the axial direction (shoulder 26 direction) is applied to each of the pressing portions 52. This force increases as the rotation speed of the rotor 8 increases, and more firmly presses the polygon mirror 36 against the hub 14, so that vibration during high speed rotation is reliably prevented. The rotation number of the rotor 8 is detected by the magnet 16 for the frequency oscillator and the pickup coil 18. A control device (not shown) accurately controls the rotation speed of the rotor 8 based on this detection information. Incidentally, FIG. 5 shows the hub 14
FIG. 6 is a cross-sectional view showing a state in which the polygon mirror 36 is incorporated in and the polygon mirror 36 is fixed to the hub 14 by a spring member 46.

Next, the present invention will be described with reference to another embodiment applied to an outer rotor type brushless DC motor in which a fixed armature coil and a rotor side magnet are circumferentially opposed to each other. 6 to 10 showing another embodiment of the present invention, the mounting structure of the polygon mirror includes a hub 60, a polygon mirror 74, and a spring member 84 which will be described in detail later. The hub 60 is formed of a synthetic resin in a cup shape, and a motor magnet (permanent magnet) 61 is embedded in the cup-shaped inner portion. Hub 6
A through hole 64 is provided in the axial center portion of the ceiling portion 62 that defines the upper surface of 0.
Is formed, and a fixed shaft (not shown) penetrates. Through hole 64
A bearing (not shown) is interposed between the side wall of the shaft and the fixed shaft, whereby the hub 60 rotates as a rotor of the motor. The hub 60 is formed with an outer peripheral portion 66 into which a polygon mirror 74 described later is fitted and mounted. Perimeter 66
Has a circular cross section and extends axially from one end of the hub 60,
The other end is defined by a shoulder (step) 68. The shoulder 68 is a right-angled surface extending radially outward from the outer peripheral portion 66. A boss portion 70 projecting in the axial direction is formed on the one end side of the hub 60. A fitting groove means is formed around the boss portion 70. That is, a ring-shaped fitting groove 72 is formed around the boss 70 around its axis. The outer diameter of the boss portion 70 is smaller than that of the outer peripheral portion 66, and there is a predetermined gap in the axial direction between the fitting groove 72 and the shoulder 68.

A polygon mirror 74 is fitted and mounted on the outer peripheral portion 66 of the hub 60. The polygon mirror 74 includes a polygonal outer peripheral portion 76 and a hub 6 as clearly shown in FIG.
Hole 78 having an inner peripheral shape that can be fitted to the outer peripheral portion 66
And axially opposite side surfaces 80 and 82 defined by a surface orthogonal to the axis. The configuration of the polygon mirror 74 is the same as the polygon mirror 3 described in the previous embodiment.
Since it is substantially the same as 6, the description will be omitted here.

Reference numeral 84 denotes a spring member for holding the polygon mirror 74 at the mounting position. The spring member 84 is formed of an annular plate member (for example, phosphor bronze, spring steel plate or synthetic resin). On the inner peripheral portion of the spring member 84, a protrusion means that can be fitted into the fitting groove 72 that is a fitting groove means is formed. That is, the protruding means is, in this embodiment,
A plurality of engaging claws 86 formed on the inner peripheral portion of the spring member 84.
It consists of Further, a plurality of pressing portions 88 are formed on the outer peripheral portion thereof. Each of the engaging claws 86 is formed by axially bending a tip portion protruding in the axial direction. Each of the pressing portions 88 is formed by a bent portion that is formed by punching out a predetermined length along the circumferential direction and that projects in the axial direction. The pressing direction of the pressing portion 88 is opposite to that of the engaging claw 86. The spring member 84 has the protrusion means (86) and the fitting groove means (72).
Each of the pressing portions 88 is configured to press the polygon mirror 74 in the axial direction of the hub 60 by fittingly holding the polygon mirror 74. That is, by pushing the spring member 84 in the axial direction from the one end side of the hub 60, each of the engaging claws 86 is fitted and held in the fitting groove 72 of the hub 60. At the same time, each of the pressing portions 88 is configured to press the polygon mirror 74 in the axial direction of the hub 60. The structure of each of the holding portions 88 is substantially the same as that of the holding portion 52 described in the previous embodiment, and thus the description will be omitted.

The polygon mirror 74 is fitted in the outer peripheral portion 66 from one end side of the hub 60, and the side surface 82 thereof is pressed against the shoulder 68 and mounted. Next, the spring member 84 is attached to the hub 6.
When pushed in from the one end side of 0 in the axial direction, each of the engaging claws 86 of the spring member 84 is fitted and held in the fitting groove 72 of the hub 60 by the spring action. Thereby, the spring member 84 is
The hub 60 is prevented from coming off in the axial direction. At the same time, the pressing portion 88 that contacts the one side surface 80 of the polygon mirror 74 bends. As a result, the pressing portion 88 of the spring member 84 is set with each of the engaging claws 86 fitted in the fitting groove 72 as a fulcrum.
Each press the polygon mirror 74 in the axial direction of the hub 62. Specifically, the side surface 82 of the polygon mirror 74 is shoulder 6
6 is pressed, the polygon mirror 74 moves to the spring member 8
It is firmly attached to the hub 60 only by the pushing operation of 4 in the axial direction. When an armature (not shown) of the motor is energized, the hub 60 rotates around a fixed shaft at a predetermined rotation speed. The polygon mirror 74 is rotated together with the hub 60. Since the hub 60 rotates at high speed,
Air passes through the upper surface of each of the pressing portions 88 of the spring member 84 at high speed. This high-speed air flow causes the polygon mirror 74 to move axially (shoulder 68 direction) with respect to each of the pressing portions 88.
A force is applied to press. This force increases as the rotation speed of the hub 60 increases, and the polygon mirror 74 moves to the hub 6
Since it is more firmly pressed against 0, vibration during high speed rotation is reliably prevented. 10 is a partial cross-sectional view showing a state in which the polygon mirror 74 is incorporated in the hub 60 and the polygon mirror 74 is fixed to the hub 60 by the spring member 84.

The present invention has been described above with reference to an embodiment.
Various modifications are possible within the scope of the invention, and these modifications are not excluded from the scope of the invention.

[0018]

According to the present invention described above, the number of parts is small, and the vibration of the polygon mirror during high-speed rotation can be reliably suppressed. As a result, the accuracy of scanning by the polygon mirror can be reliably maintained, and the reliability can be sufficiently ensured. Since the holding force of the polygon mirror increases as the rotation speed increases, there is no possibility of setting the initial setting value of the spring force of the spring member to an excessively large value.
Also, the polygon mirror can be firmly held on the hub by pushing the spring member from one end side of the hub in the axial direction, or by pushing and rotating it. To do. Further, since there is no possibility of damaging the polygon mirror, quality and reliability are improved. Furthermore, since the number of parts is small, mass production is possible at low cost.

[Brief description of drawings]

FIG. 1 is an exploded view showing a main part of an embodiment of a mounting structure for a polygon mirror improved according to the present invention, with a part broken away.

FIG. 2 is a plan view of the spring member shown in FIG.

FIG. 3 is a plan view of the polygon mirror shown in FIG.

FIG. 4 is a plan view of the hub shown in FIG.

FIG. 5 is a partial cross-sectional view showing a state in which a polygon mirror is attached to a hub and fixed with a spring member.

FIG. 6 is an exploded view showing the main parts of another embodiment of the polygon mirror mounting structure improved according to the present invention;
Figure showing a part of it broken

FIG. 7 is a plan view of the spring member shown in FIG.

8 is a plan view of the polygon mirror shown in FIG.

9 is a plan view of the hub shown in FIG.

FIG. 10 is a partial cross-sectional view showing a state in which a polygon mirror is attached to a hub and fixed with a spring member.

[Explanation of symbols]

 14 and 60 ... Hubs 24 and 66 ... Outer peripheral portion 26 and 68 ... Shoulder 30 ... Recess 32 .... Convex 34 ... Grooves 36 and 74 ... Polygon mirrors 46 and 84 ... Spring members 48 ... Recesses 50 ... Convex portions 52 and 88 ... Retaining portions 72 ... ... Mating groove 86 ... Engaging claw

Claims (3)

[Claims] 1. A hub including a hub rotated by a driving force of a motor, a polygon mirror fitted and mounted on an outer peripheral portion of the hub on one axial end side, and a spring member for holding the polygon mirror at a mounting position. , The one end side of the hub,
A boss portion projecting in the axial direction is formed, a fitting groove means is formed in at least a part of the periphery of the boss portion, the spring member is formed of an annular plate member, and the fitting portion is formed on an inner peripheral portion thereof. Projecting means that fits into the groove means is formed, and a plurality of holding portions are formed on the outer peripheral portion thereof along the circumferential direction and gradually inclined downward in the rotation axis direction toward the rotation direction of the hub. Each of the tip ends of the spring member is formed of a bent portion that projects in the axial direction. Pressing the polygon mirror in the axial direction of the hub,
The polygon mirror mounting structure, wherein the pressing force on each of the pressing portions is increased by the air flow when the hub is rotated. 2. A plurality of concavo-convex portions having a predetermined cross-sectional shape are formed around the boss portion, and the fitting groove means comprises:
The protrusion means of the spring member is formed of an arcuate fitting groove centered on the shaft center of the hub formed in each of the protrusions, and the protrusion means is formed on the inner peripheral portion of the protrusion-depression portion. The spring member is composed of a concavo-convex portion that can be fitted, and is pushed and rotated in the axial direction from the one end side of the hub in a state where the concavo-convex portion of the spring member is aligned with the concavo-convex portion of the boss portion. The polygon mirror mounting structure according to claim 1, wherein each of the convex portions is configured to be fitted and held in each of the fitting grooves of the boss portion. 3. The fitting groove means comprises an annular fitting groove formed around the boss portion and centered on the axial center of the hub, and the protrusion means of the spring member is Each of the engaging claws is fitted into the fitting groove of the hub by being configured by a plurality of engaging claws formed on the peripheral portion and pushing the spring member axially from one end side of the hub. The mounting structure for a polygon mirror according to claim 1, wherein the mounting structure is configured to be held.