JPS62184429A - Rotary polygonal mirror driving device - Google Patents

Abstract

PURPOSE:To eliminate accumulation of the error of constituting parts by forming a rotor with materials having a specific gravity larger than that of a rotary polygonal mirror and rotating the rotor to cut the upper face of its annular projection on a basis of a stator body. CONSTITUTION:A rotor 8 is formed with materials having a specific gravity larger than that of a rotary polygonal mirror 13 for the purpose of approximating the center of gravity of the rotating part of the rotor 8 to the axis near an annular projection 83 which is provided on the rotor 8 as the attaching face of the polygonal mirror 13. A half or larger part of the lower part of a stator body 4 has an outside diameter >=3 times as large as that of a ball bearing 11 to improve the rigidity. The upper face of the rotor 8 is provided with a fitting projection 82 to which the polygonal mirror 13 is fitted and the annular projection 83 as the reference position of the lower face of the polygonal mirror 13. In the rotatory balance state, a shaking part of the upper face 83a is cut while rotating the upper face 83a of the projection 83. Thereafter, the polygonal mirror 13 is stuck to the rotor 8. Thus, the polygonal mirror 13 is kept high-precision to obtain images of high quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotating polygon mirror drive device, and more particularly to the configuration of an electric motor for manufacturing the electric motor that provides the driving force with high precision.

[Conventional technology]

The electric motor used in this type of drive device is one in which a polygon mirror is directly fixed to the rotating part, or the rotating part is formed directly into a rotating polygon mirror, as described in Japanese Patent Publication No. 59-197010. A rotating polygon mirror driving device is formed by doing the following.

Compared to the latter, the former is easier to select the material for the polygon mirror and to process the polygon itself, and this method is advantageous in terms of manufacturing. In either case, the rotating polygon mirror requires a high degree of precision, and the part that fixes the polygon mirror must have sufficient rotation precision, that is, the coaxiality of the rotating part and the flatness of the surface on which the polygon mirror is attached.

Since run-out and other factors have a large effect, improving the accuracy of these factors was an essential requirement. However, the electric motor part is a combination of parts such as a stator, two rotors, and a bearing, and there is a limit to the accuracy that can be obtained by combining these parts as a unit.

[Problem that the invention seeks to solve]

In the above-mentioned conventional technology, even if the precision of individual parts is manufactured to obtain the best results,
After assembly, the accuracy errors of each part are aggregated and become a large error, making it impossible to avoid problems such as tilting of the mirror surface that occurs when a polygon mirror is attached.

An object of the present invention is to improve the accuracy of the assembled state of an electric motor, and to improve the dynamic rotational unbalance of rotating parts in the assembled state of the electric motor so that good accuracy can be obtained when a polygon mirror is attached to the motor. The purpose of installing the polygon mirror in the assembled state of the electric motor is to minimize the accumulation of errors in the component parts by cutting the parts.

[Means for solving problems]

For the above purpose, by appropriately selecting the material of the rotating part of the electric motor, the center of gravity of the rotating part can be brought closer to the polygon mirror mounting part, making it easier to remove the unbalance of the dynamic rotation of the rotating part. In addition, as a material that is easy to cut, in order to improve the accuracy of the motor after assembly, it is rotated by a cutting tool, such as a cutting tool, that is fixed in a fixed position relative to the stator, which is the most important reference after assembly. The purpose of cutting the rotor is to remove the relative run-out between the stator and rotor, but the important thing is to install a cutting tool at a fixed position relative to the stator. The fixed position varies greatly depending on the rigidity of the electric motor itself and whether or not the rotating body vibrates during cutting. For this purpose, as mentioned above, by selecting the specific gravity of the material of the rotating part, when the center of gravity of the rotating body is close to the part to be cut, vibrations during rotation will be minimized and stable cutting will be possible. The bearing support part on the stator side must be supported with rigidity, the spacing between the bearings must be made as wide as possible to prevent shaft vibration, and the ball bearings used in the bearings must be fixed by the axial force applied during cutting. It is necessary to use a bearing structure that prevents the rotor side from displacing with respect to the child. Furthermore, as mentioned above, vibrations caused by unbalanced rotation of the rotor are a factor that makes it difficult to maintain accuracy, so this should be eliminated. By doing so, it is possible to improve accuracy during rotation.

[Effect]

First, in order to increase the rigidity of the bearing support part on the stator side,
When attaching the rotating mirror to 1/2 of the total length of the stator, the outer diameter of the section on the opposite side and the opposite side should be at least three times the outer diameter of the bearing to provide sufficient rigidity against the bending moment applied to the rotating polygon mirror side of the rotating shaft. It is intended to have the following.

Next, the electric motor is rotated, and the first rotor is cut using a cutting tool with the stator side as the reference position, so that the deflection of the surface on which the polygon mirror is attached can be removed.

At this time, a bending moment and a load are applied to the shaft in the axial direction through the cutting surface, pushing the ball bearings that make up the bearing in the axial direction, but the contact between the outer ring, inner ring, and balls of the ball bearing A preload is applied to prevent the position from changing, which allows the rotor surface to be cut stably. Further, a groove on the circumference, for example, is provided close to the outer periphery of the rotor surface, and a correction weight for correcting the unbalanced rotation is inserted therein, or a correction weight is inserted into the rotor itself to remove the unbalanced weight. We take measures such as drilling holes to compensate for the weight and prevent vibrations caused by unbalance of the rotor, which is a rotating body. This prevents the accuracy from decreasing due to unevenness due to undulation of the surface. Here, one feature of the present invention is that the rotor's polygon mirror mounting portion is made of a material such as brass that has a specific gravity at least higher than that of the material of the polygon mirror, so that the center of gravity of the rotating portion can be By installing it near the part and correcting the unbalance near this area,
In addition to providing the effect of preventing the expansion of vibrations due to residual child balance during rotation of the rotor, the material of the cut portion of the rotor satisfies the specific gravity mentioned above and is made of a material with good machinability to smooth the cut surface. This provides an effect of further improving accuracy.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

In the figure, 1 is a rotating polygon mirror drive device, and stator coil 2
A stator substrate 3 is provided, which is fixed to the stator body 4, and the coil 2 is formed into a three-phase coil as shown in FIG. According to No. 1, a driving force is applied to a magnet 6 which is an annular body provided apart from a stator substrate 3 and a narrow gap 5 and magnetized to a plurality of poles, and this driving force is transmitted through a yoke iron plate 7 of the magnet 6. and is fixed to the rotor 8. Reference numeral 9 denotes an annular iron yoke plate for forming a magnetic path on the stator side, and is fixed to the stator main body 4. The stator body 4 has a stator coil 2 and a stator board 3 in a portion less than 1/2 of the total length of the stator body 4, and has bearing support parts 41 and 42 in the center, and the upper bearing support part 41 has an umbrella. It is provided at the center of the shaped rotor 8 at a position surrounded by the magnet 6 and at the upper end of the stator body 4. The rotor 8 is made of a material with a higher specific gravity than the rotating polygon fi 13, and has excellent machinability, since the center of gravity of the rotating part is placed as close to the annular protrusion 83 provided on the rotor 8 as the mounting surface of the rotating polygon fi 13 as much as possible. The key is to select materials with good quality. In the embodiment of the present invention, the rotor 8 is made of brass with a specific gravity of about 8.2, and the rotating polygon mirror 13 is made of aluminum with a specific gravity of about 2.7. on the other hand,
The lower bearing support part 42 is provided at the lowest part of the stator body 4, and the lower part of the stator body 4, which is the lower part in the figure, has an outer diameter of at least 3 times the outer diameter of the bearing. In order to improve the rigidity, the spacing between the bearings is increased, and the inclination of the shaft 12 due to errors in the upper ball bearing 10 and lower ball bearing 11 mounted thereon is minimized. These ball bearings 1
The outer rings 0 and 11 are the bearing parts 41 and 42 of the stator main body 4.
The step portions 43 and 44 regulate the distance between the bearings. On the other hand, the shaft 12 is fitted and fixed to a 681 provided at the center of the rotor 8, and the rotating polygon mirror 13 is fixed on the rotor 8, and the rotating polygon mirror 13 is fixed on the top surface (a six-sided mirror in the embodiment). 13, and an annular projection 83 which serves as a reference position on the lower surface of the rotating polygon mirror 13 and is an important part for achieving accuracy in the rotating polygon mirror drive device of the present invention. An annular groove 84 is provided in close proximity for fixing the additional weight 14 for correcting the unbalance of the rotating parts. In order to correct the dynamic child balance during rotation of the rotating part, in addition to the method illustrated in the embodiment of the present invention, a hole may be made with a drill or the like near the outer periphery of the rotor 8 to remove the unbalanced weight. There are several methods, and the same effect can be obtained using either method. The shaft 12 has a length that passes through the inner rings of the upper and lower ball bearings 10 and 11 and projects further downward from the lower ball bearing 11. Here, the inner circumferential side of the shaft 12 comes into contact with the inner ring of the lower ball bearing 11. The outer periphery is provided with a dish-shaped preload spring 15 which is received by a preload adjuster 16 fixed to the end of the shaft 12. This dish-shaped preload spring 15 is on the upper side.

By eliminating the radial clearance between the lower ball bearings 10 and 11, the rotating polygon mirror rJj is created using the radial clearance.
A: This is to prevent a decrease in rotation accuracy during rotation due to dimensional play in the radial direction due to rotation of the electric motor section 17 consisting of the stator body 4 and rotor 8 of the device 1, as shown in Fig. 3. , upper and lower ball bearings 10 and 1, respectively.
] is applied in the direction of the arrow P', and the relationships among the outer ring, inner ring, and balls of each ball bearing are in the state shown in the figure.

In such a state, the rotor 8 as shown in FIG.
Even if a force in the P direction is applied to the stator body 4 and the rotor 8, no relative movement occurs between the stator body 4 and the rotor 8. In such a state, when the motor part 17, that is, the rotor 8, rotates due to the electromagnetic force between the stator body 4 and the rotor 8 and reaches a predetermined rotation speed, the centrifugal force due to the rotor balance of the rotor 8 naturally causes the motor to rotate. Portion 17 will experience vibrations.

The electric motor section 17 is provided with an FG that detects the rotational speed of the rotor 8, and this signal feeds a speed command back to the drive circuit to keep the rotational speed of the rotor 8 constant. Vibrations caused by the child balance are generated in the optical system of a laser printer 21 as shown in FIG. The light is focused by an fO lens 22 that keeps the scanning speed constant above the photoreceptor drum 23.
This deteriorates the scanning accuracy of the laser beam 24 on the upper side and deteriorates the image produced by the laser printer 21. Therefore, in the motor section 17, an annular groove 84 is used to add additional weight 14 thereto to eliminate rotational imbalance. This creates the first factor in obtaining high image quality.

Next, in a state where the rotational unbalance has been sufficiently eliminated, the stator main body 4 of the motor section 17 is fixed to the fixed reference stand 18, and the rotor 8 is The swinging portion of the upper surface 83a is cut while rotating the upper surface 83a of the annular protrusion 83 provided thereon by the self-generated rotational force of the electric motor section 17.

As a result, the upper surface 83a of the annular protrusion 83 can suppress the deflection to 0.5 μm, whereas the combination of the components of the motor portion 17 alone could suppress the deflection to 20 μm. Also, the upper surface 8 of the annular projection 83
The cutting of 3a performs the same operation as cutting on a lathe using the power generated by the electric motor part 17 without borrowing any other mechanical power, so that it is possible to prevent the accuracy from decreasing due to the influence of vibrations caused by other cutting machines. I can do it. Furthermore, as explained in FIG. 3, the radial clearance between the upper and lower pole bearings 10 and 11 is eliminated by the preload spring 15, so that even if force is applied in the direction of the arrow P in FIG. 4 during cutting, the rotor 8 is one that does not move in the direction of the arrow and allows for stable cutting to remove runout. In this case, the upper ball bearing 10 transfers the axial force P to the inner ring,
ball.

When cutting the upper surface 83a of the annular protrusion 83 by receiving it at the upper part of the stator body 4 in the order of the outer ring step 43, the axial load P is separated from the center by d, so a bending moment is applied to the shaft 12. The moment is maximum at the position of the lower ball bearing 11.

For this reason, a bending moment is also applied to the bearing support portion 42 of the lower ball bearing 11, and it is necessary to provide this portion of the stator body 4 with large rigidity. As shown in the figure, this part is made thicker to increase rigidity.

〔Effect of the invention〕

As described above, according to the present invention, first, i'l! Motive part 17
In order to correct the rotor imbalance caused by the rotation of the rotor 8 to be as small as possible, the rotor 8 is made of a material with a higher specific gravity than the rotating polygon fi 13, and the center of gravity of the rotating polygon mirror 13 of the rotor 8 is mounted close to the position in terms of axial coordinates. By correcting the rotor balance near this point, the unbalance can be minimized, so even if the first rotor surface fi13 is rotated at a high speed of about 10,000 rpm+, the vibration will not increase and the image quality will be improved. It can have a great effect on improvement.

Next, the stator main body 4, which is a rotating part, excites the electric motor part 17 to self-rotate as an electric motor, and after removing the aforementioned unbalance, the upper surface 83a of the annular protrusion 83, which serves as a reference for attaching the rotating polygon mirror 13, is removed. Since the upper surface 83a is cut using the stator main body 4 as a reference, it can be machined until the runout of the upper surface 83a is almost eliminated.Since this surface is used as a reference when attaching the rotating polygon mirror 13, the attached rotating polygon mirror 1
No. 3 can maintain high accuracy and obtain a high-quality image without causing unnecessary displacement of the laser beam b. In this case, the shape of the stator main body 4 is stable even against the axial load and bending moment received when cutting the upper surface 83a, which has the effect of further increasing accuracy.

[Brief explanation of drawings]

Fig. 1 is a front cross-sectional view of an embodiment of the rotating polygon mirror drive device of the present invention, Fig. 2 is a plan view, Fig. 3 is an explanatory diagram of the state of the ball bearing, and Fig. 4 is the rotation of the main part. FIG. 5 is an electrical system diagram for driving the motor portion, and FIG. 6 is an explanatory diagram of an example of a laser printer using the rotary polygon mirror drive device of the present invention. 1... Rotating polygon mirror drive device, 2... Stator coil,
3... Stator board, 4... Stator body, 5... Slit, 6... Magnet, 7, 9... Yoke iron plate, 8...
... Rotor, 10... Upper ball bearing, 11.
...Lower ball bearing, 12...shaft, 13...
Rotating polygon mirror, 14...additional weight, 15...preload spring, 16...preload adjustment tool. 17... Electric motor part, 18... Reference stand, 19...
Bit, 21... Laser printer, 22... fθ lens, 23... Photosensitive drum, 24... Laser light beam, 41° 42... Bearing support part, 43.44...
Stepped portion, 81...hole, 82...fitting protrusion, 83...
Annular projection, 83a...Top surface, certain 10 oak? Figure 93 α-m- and a certain B mouth t+ figure

Claims (1)

[Scope of Claims] 1. In a stator body (4) in which ball bearings (10) and (11) are fitted at both upper and lower ends with their outer ring intervals regulated, one side is electrically biased. A space for installing a stator coil (2) that gives rotational force to the magnet (6) is provided in an axial direction of 1/2 or less, and the other end has a wall thickness that is three times or more thicker than that of the ball bearing (11). A rotor (8) to which a magnet (6) is fixed is provided on the side facing the stator coil (2), and this rotor (8) is connected to a rotating polygon mirror (
A bearing support part (13) formed into an umbrella shape and having one ball bearing (10)
41), the outer surface of the shape for fixing the rotating polygon mirror (13) has a fitting protrusion (82) that fits with the rotating polygon mirror (13), and a surface that supports this. A shaft (12) formed with an annular projection (83) and a means for correcting rotational imbalance is fitted and fixed in the center of the rotor (8).
) passed through two ball bearings (10) and (11), and the inner ring of one ball bearing (11) was pressed by a preload spring (15) to correct the unbalance of the rotor (8). The motor portion (17) formed between the rotor (8) and the stator body (4) is energized to rotate the rotor (8), and the rotor is rotated with respect to the stator body (4). (8) Annular projection (83
) After cutting the upper surface (83a) of the rotating polygon mirror (13
) is fixed to a rotor (8).