JPH04190315A - Polygon mirror - Google Patents

Abstract

PURPOSE:To prevent shifting and removal of a weight caused by the centrifugal effect and enable maintenance of balance with high accuracy by providing on an upper surface of the reference center hole of a polygon mirror an annular groove of L-shaped section of which bottom line is extended radially, and which is concentric with the reference center hole. CONSTITUTION:There is provided to the external circumference of the reference center hole H of a polygon mirror 2 an annular groove B of L-shaped section which is concentric with the reference center hole H. The annular groove B of L-shaped section is open to the top, and a weight W1 is embedded into the annular groove B. This constitution not only facilitates to maintain the balance of an optical deflecting system, but also prevents shifting and removal of the weight by the centrifugal effect while the optical deflecting system rotates. In particular, the balance adjustment of the polygon mirror can be achieved easily, enabling good maintenance of the balance when the optical deflecting system rotates at high speed and when a thick polygon mirror is employed.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a polygon mirror used in an optical deflector.

(Prior Art) An optical deflector employing a polygon mirror will be described with reference to FIGS. 2 and 3 of the accompanying drawings.

An armature coil group 9 is arranged on the upper surface of an iron-based printed circuit board 10. A fixed shaft bushing 12 is fixed to the center of the printed circuit board 10.

A fixed shaft 3 is fixed to the fixed shaft bush 12. A pair of pole bearings 11, which are rotatable bearing means, are mounted on the outer periphery of the fixed shaft 3 together with the hub 4. A long yoke 7 is fixed to the lower surface of the hub 4, and this back yoke 7
A motor driving magnet 8 is adhesively fixed to the inside of the holder.

Further, a U-shaped annular groove 1 is provided on the upper outer surface of the hub 4.
4 is provided by cutting or the like, while the suppression cap 15 has a U-shaped annular #111 provided on the upper outer surface of the hub 4.
A plurality of half-folding protruding portions 13 are provided which are a plurality of engaging members that can be engaged with 4 and play the role of preventing removal. After mounting the polygon mirror l on the stepped portion of the hub 4, press the elastic O-ring 6 located on the upper surface of the polygon mirror 1, then push down the pressing cap 15, and then push the half-folded protruding portion 13 of the pressing cab 15 onto the hub 4. The polygon mirror 1 is clamped and fixed between the hub 4 and the O-ring 6 by engaging the U-shaped annular groove 14. Reference numeral 3b indicates a preload means ↑ for the bearing means provided at the upper end of the fixed shaft 3.

When the polygon mirror 1 is supported by the hub 4 and rotates around the outer periphery of the fixed shaft 3, various efforts have been made to maintain the horizontal balance during rotation of the polygon mirror 1 and improve its accuracy.

One of them is the configuration shown in FIG. In FIG. 2, mirror surfaces AI, A2. A3. A4゜A5. A6. A
7. On the upper surface of an octahedral polygon mirror 1 having A8, a concentric circular U-shaped cross section WD is carved with the reference center hole H of this mirror as the center. The polygon mirror L is assembled into an optical deflector and mounted on a motor, and in order to adjust the balance during rotation of the motor, a weight W is embedded at a predetermined location within this circular groove with a U-shaped cross section. It was designed to ensure smooth rotation of Polygon Mira 1.

(Problem to be Solved by the Invention) However, even if the weight W is embedded in a circular groove with a U-shaped cross section formed in the upper surface F of the polygon mirror 1 as described above, the centrifugal force due to the rotation of the optical deflector As a result, the weight W moves within the circular groove or falls off from the opening of the circular groove, so that the purpose of maintaining smooth rotation of the polygon mirror may not be achieved. Especially when rotating at high speeds,
When a thick polygon mirror is used for the hub that supports this, there are problems such as difficulty in maintaining balance during rotation.

The invention of this application aims to solve the above problems.

(Means for solving the problem) Polygon mirror 2 forming a plurality of mirror surfaces A1 to A8 on the outer periphery
In the optical deflector incorporating the polygon mirror 2, the upper surface F of the polygon mirror 2 and the reference center hole H
A concentric circular groove B with an angled cross-section or a circular MIC with a U-shaped cross section is bored in the inner side of the groove with the reference center hole H as the center, respectively.
The circular groove B with a slanted cross section formed in the upper surface F opens upward, and the circular groove C with a U-shaped cross section formed in the inner surface I opens toward the reference center hole H, and into these circular grooves B and C. Each weight W
Polygon Mira 2 characterized by embedding l, W2
I will provide a.

(Function) By drilling a plurality of circular grooves with an angular or U-shaped cross section concentrically on the outer periphery of the reference center hole and embedding a weight in each groove, the balance of the optical deflector can be maintained. This not only facilitates the rotation of the optical deflector, but also prevents the weight from moving or falling off due to centrifugal force during rotation of the optical deflector. Particularly when the optical deflector is rotating at high speed or when a thick polygon mirror is used, the balance of the polygon mirror can be easily adjusted and a good balance can be maintained.

(Embodiment) An embodiment of the invention of this application will be described below with reference to the accompanying drawings.

The polygon mirror 2 of the present invention employed as an optical deflector has a plurality of outer peripheral mirror surfaces AI, A2. A3. A4. A5゜A6. A7.
It is a hexagonal polygon mirror that forms A8. On the upper surface F of the polygon mirror 2, there is a circular groove B formed on the outer periphery of the reference center hole H, concentrically with the reference center hole H, and having a cross-sectional shape extending toward the outer periphery.
to be drilled. Also, a circular groove C having a U-shaped cross section is bored in the inner surface I of the reference center hole H, concentrically with the reference center hole H. The circular groove B opens above the polygon mirror 2, and the circular groove C opens toward the inner side of the reference center hole H, respectively. In order to maintain balance with high precision when the polygon mirror 2 is supported by the hub 4 and rotates around the fixed shaft 3, weights Wl and W2 are embedded in appropriate positions of the circular grooves B and C. . In other words, in the circular groove B with an L-shaped cross section, the weight is deeply inserted into the L-shaped part of the bottom surface, and in the U-shaped circular groove C, the weight is embedded in the part that opens toward the inner surface of the reference center hole. It is. As described above, the polygon mirror 2 has a plurality of circular grooves B and C which are used as balance weights at a plurality of locations to maintain the balance. Also weight Wl.

W2 can be prevented from falling off or moving during rotation.

The configuration, in which multiple concentric circular grooves are provided and weights are embedded in these grooves according to the shape of the grooves, maintains high-precision balance, especially when the thickness of the polygon mirror is large or when the polygon mirror rotates at high speed. It's useful.

In this example, a polygon mirror forming an octahedron has been described, but the same principle can of course be applied to polygon mirrors with other numbers of faces, and the number of circular grooves is not necessarily limited to two. Single or multiple values may be set.

(Effect) In the present invention, a single or plural concentric circular grooves are formed with the reference center hole of the polygon mirror as the center, and balance weights are arranged in each of these circular grooves.
A polygon mirror built into the optical deflector helps maintain high-precision balance during rotation. Particularly when the polygon mirror rotates at high speed or when a polygon mirror with a large thickness is used, it is possible to maintain balance with high precision. Therefore, vibrations during rotation of the optical deflector can be suppressed to a minimum. Therefore, when the optical deflector is used in a laser beam printer or the like by improving the optical beam scanning stability of the optical deflector, printing quality can be improved.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of a polygon mirror according to the present invention. FIG. 2 is a partially cutaway perspective view of a conventional polygon mirror. Figure 3 is a cross-sectional view of an optical deflector that uses a polygon mirror. 1.2...polygon mirror, 3...fixed axis, 4...
Hub A1-A8...mirror surface, B, C, D...circular groove,
F...Top surface, H...Reference center hole, ■...Inner surface,
w, wt, w2... weight. Figure 1 Figure 2 Figure 3 I 3 Fixed shaft 4 Hub'

Claims (1)

[Scope of Claims] 1. An optical deflector incorporating a polygon mirror forming a plurality of mirror surfaces on the outer periphery, which has an L-shaped cross section with the bottom surface extending toward the outer periphery from the upper surface of the reference center hole of the polygon mirror, and A polygon mirror characterized by having a circular groove concentric with the reference center hole. 2. The polygon mirror according to claim 1, wherein a circular groove having a U-shaped cross section is formed concentrically with the reference center hole on the inner surface of the reference center hole. 3. The circular groove formed in the upper surface opens upward, and the circular groove formed in the inner surface opens toward the reference center hole, and weights are embedded in these circular grooves. The polygon mirror described in 1.