JPS59202429A - Information recording device - Google Patents

Abstract

PURPOSE:To rotate stably a polygon mirror with the center of gravity down, and to reduce the deflection of the mirror as much as possible to obtain a record with good quality by providing the polygon mirror at the position apart from the support position of a rotating shaft in the gravitative direction. CONSTITUTION:A hollow cylinder 3 contains a motor box formed by fixing a bottom plate 3a which has a shaft 1 implanted in the center and an armature coil 8 as a stator is arranged on the internal circumference of the cylinder 3. A sleeve 2 fitted with a thrust receiving member 5 atop is supported on the shaft 1 by the member 5 at a fine interval of several microns, and numbers of spiral herringbone type streak grooves are formed in the external circumference of the shaft, so that the shaft 1 and sleeve 2 form a dynamic pressure bearing. A permanent magnet 7 is fitted to the outer circumference of a sleeve 2 at the position facing to the armature 8 and the polygon mirror 6 is fixed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applicable to a laser beam printer, copying machine or video. The present invention relates to an information recording device having a rotating polygon mirror suitable for use in discs and the like.

Recently, high-speed rotation motors used in the drive parts of scanners, videos, and disks for information recording devices such as laser beam printers have become more and more important. Motors using dynamic pressure bearings have come to be used in search of ease of use.

FIG. 1 shows an outline of the main parts when such a motor is used in a beam scanning mechanism of a laser beam printer. The light beam is deflected by the boundary surface of a polygon mirror PM attached to the rotating shaft of a motor M, and this light beam scans the surface of a rotating photosensitive drum D having a photoconductive layer formed on the edge of the lens system Li to form a latent image. However, this latent image is transferred and fixed onto a notebook-like material by an image forming means similar to, for example, well-known electrophotographic copying means to obtain a copy.

In such devices, motors that can rotate polycon mirrors at high speed and with high precision and have a long life and are easy to maintain are required, and to meet this demand, motors that use hydrodynamic bearings are being used. It's coming.

FIG. 2 is a sectional view showing a motor equipped with a hydrodynamic bearing and a polygon mirror suitable for use in the above case, and the bottom of the casing 3 has herringbone grooves on the outer circumferential surface. A sleeve 2 is loosely fitted onto this shaft with a gap of approximately several microns, and a magnet 7 serving as a rotor is mounted on the outer surface of the sleeve 2. It is arranged.

An armature coil 8, which is a stator, is attached to the inner surface of the casing 3 so as to surround the magnet 7, and an armature coil 8, which is a stator, is attached to the bottom of the casing 3 in order to detect the rotation speed of the magnet 7. A Hall element 9 and a Hall element 1o for controlling the rotation speed are fixed, respectively, to maintain constant rotation of the rotor.

The fixed shaft 1. The sleeve 2 protrudes upward in the drawing,
A polygon mirror 6 is attached near the top of the sleeve, and a thrust receiver member 5 is arranged inside the top of the sleeve.When the sleeve is stationary, this member 5 comes into contact with the end of the shaft 1, and the sleeve 2゜Magnet 7. It is designed to support a rotating part including the mirror 6.

As can be seen from the illustrated configuration, the rotary drive device (motor) equipped with a rotating polygon mirror configured as described above attaches the stator, Hall element, etc. to the casing 3, and then rotates the polygon @
6. Magnet 7. Since the rotating part consisting of the sleeve 2 and the like is mounted on the shaft and assembled, there is a risk that the magnet will come into contact with the Hall elements 9 and 10, which must be placed near the magnets, and damage these elements. Furthermore, the characteristics of Hall elements vary, and even after they have been installed, they sometimes have to be replaced. In such a case, it will be necessary to completely disassemble the assembled device, but it is easy to understand that such work is troublesome and undesirable.

In order to eliminate such drawbacks, for example, as shown by the dotted line in FIG.
It is conceivable to arrange it. In this way, the Hall element can be easily replaced, but in this case, it is necessary to arrange the Hall element and a support member to support it between the polygon mirror 6 and the magnet 7. For this purpose, the sleeve forming the bearing 2. @11 will have to be made that long. At this time, if the rotating part including the sleeve 2 is pulled out from the shaft to attach and detach the pole element, there is no need to make the bearing part particularly long. However, once the device is on the market, it is virtually impossible.

As mentioned above, making the bearing part even a little longer means that the polygon mirror, which is a large inertial body in the rotating part, will be separated from the bearing part by that much.In hydrodynamic bearings where the bearing rigidity cannot be increased very much, This is unavoidable, and a decrease in rotational stability and impact resistance cannot be avoided.

The present invention has been made in view of the above-mentioned defects in information recording devices such as image forming devices, particularly in the motors used therein, and includes a polygon mirror disposed near the lower end of the sleeve. , the pole element is attached to the lid that closes the casing, and the pole element is positioned near the permanent magnet when the lid is placed on the casing, thereby controlling the center of gravity of the entire rotating part. This lowers the rotary part to support and operate the rotating part more stably, and also to prevent the Hall element from being damaged by magnets, etc.
It is not bulky and can be replaced very easily as it is not often interfered with by the arrangement of other parts.This makes it possible to shorten the hydrodynamic bearing part, making it easy to manufacture and assemble. It is also an object of the present invention to provide an information recording device that is easy to maintain, allows the polygon mirror to operate more stably, and greatly contributes to accurate optical information processing.

Embodiments of the present invention will be described below with reference to FIG. 3 of the accompanying drawings. In this figure, members corresponding to those shown in the first figure described above are designated by the same reference numerals. A bottom plate 3a having a shaft 1 implanted in the center thereof is fixed to the hollow cylindrical body 3 to form a motor case 7, and an armature coil 8 serving as a stator is disposed on the inner periphery of the cylindrical body 3.

On the shaft, a sleeve 2 has a thrust bearing member 5 attached to the top thereof, and the thrust bearing is supported by the member 5 with a minute gap of several microns between the shaft 1 and the shaft 1.
Spiral shape on the outer circumferential surface.

The shaft 1 and the sleeve 2 form a hydrodynamic bearing by forming a large number of herringbone grooves.

A permanent magnet 7 is arranged on the outer periphery of the sleeve 2 at a position facing the armature 8, and a polygon mirror 6 is fixed near the lower end of the sleeve.

A cover 4a having Hall elements 9 and 10 attached thereto used for detecting and controlling the rotational speed is disposed on the top of the cylinder 3 to maintain the entire body in an airtight state. As can be seen from FIG. 3, the Hall elements 9 and 10 are of course positioned so that they are brought near the permanent magnet when the cover 4a is attached to the cylindrical body 3.

With this structure, if the Hall element needs to be replaced, it can be easily done by simply removing the cover 4a without having to disassemble the device significantly. Unlike known systems in which rotating parts including sleeves, permanent magnets, etc. are assembled in a state in which the Hall element is installed last, there is no risk of damaging the element. Further, since no extra space is required to facilitate the attachment and detachment of the Hall element, the bearing portion can be shortened accordingly, making manufacturing easier and stabilizing the operation of the rotating portion.

FIG. 4 shows still another embodiment of the present invention, and since the basic structure of the device including bearings, motors, polygon mirrors, etc. is the same as that shown in FIG. Explanation will be omitted.

In this embodiment, the end face of the permanent magnet is also magnetized, and a Hall element 9,1° is disposed so as to face the end face. When the pole element is arranged as shown in Figure 3, the position of the Hall element must be shifted in the direction of the rotational axis of the rotating part so that the coil end of the armature does not come into contact with it. The permanent magnet itself must be made a little longer in order to face the two, but by using the configuration shown in Figure 4, there is no need to make the permanent magnet longer due to the presence of the Hall element. It is convenient because it can be shortened.

It should be noted that the pole element serving as the motor control means is not limited to this, and any known control means may of course be used.

As explained above, in the above embodiment, the polygon mirror is arranged below the permanent magnet which is the rotor of the motor, and the permanent magnet, which is a large inertial body in the rotating part, the polygon mirror, etc.
Since the thrust bearings, which are all supporting members, are located below the members, the center of gravity of the rotating part is lowered in the 1f force direction, and the hydrodynamic bearings generate pressure in the radial direction on the polygon mirror, increasing bearing rigidity. Since the rotation can be stabilized, the reliability of beam scanning can be increased and good images can be obtained.

The Hall element used for detecting and controlling the rotational speed of the rotor is placed in a position that is easy to manufacture, maintain, inspect, and replace, and does not require any special space for assembly or replacement. This greatly contributes to improving the functionality of the device and reducing costs.

The rotation drive device according to the present invention, which includes a motor equipped with a polygon mirror, has the polygon mirror below the rotation axis as described above, so that the center of gravity of the entire rotating part of the device is located below, and stable rotation can be achieved. This makes it possible to minimize mirror deflection and obtain high-quality records. Furthermore, when the rotary drive device according to the present invention is incorporated into an image forming apparatus or the like, the detection element portion such as the Hall element, which has relatively low strength, can be attached and detached in minutes before other components, so it is not necessary for repair or maintenance. It is easy to do this, and it greatly contributes to reducing not only manufacturing costs but also running costs.

[Brief explanation of the drawing]

FIG. 1 is a perspective view schematically showing a part of a scanner of a known image forming apparatus, FIG. 2 is a sectional view of a known polygon mirror and a rotational drive device that drives it, and FIG. 3 is a rotational drive device according to the present invention. FIG. 4 is a sectional view of a device showing another embodiment of the present invention. 1... IQll, 2... Sleeve, 3. Casing (cylindrical body), 4.4a... Cover, 5... Thrust receiver is a member, 6. Polygon mirror, 7... Magnet, 8... Coil ,9. ] O-Hall device patent applicant Canon Co., Ltd. agent Patent attorney Mi Irie ゛1 Figure 2 Figure 4 Figure 3

Claims (1)

[Claims] An information recording device in which a polygon mirror is arranged at a part of a rotating shaft which is biased in the direction of gravity, and is spaced 411 degrees apart in the direction of gravity from the support position of the shaft.