JPH07104205A - Rotating body - Google Patents

Abstract

PURPOSE:To provide the rotating body which is formed by coupling >=2 parts varying in coefft. of linear expansion, does not generate an unbalance change even if the temp. of the rotating body is changed by the heat generation of the rotating body itself or environmental temp. and does not generate vibrations in spite of rotation at a high speed. CONSTITUTION:This rotating body is constituted by disposing two cylindrical parts to face each other apart a spacing to fix a blind cylindrical rotor 2 and rotor 19 varying in materials. Since the inner and outer peripheries of the cylindrical parts are not in contact with each other, the force acting on the cylindrical parts is generated only in both bottoms joined by a screw 18 even if the temp. of the rotating body changes and a difference in the expansion and shrinkage of the rotor 2 and the yoke 19 is generated by a difference in the coefft. of linear expansion. A deviated deformation is not generated and vibrations are not generated if the rotating body rotates at a high speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention suppresses relative movement between constituent members due to temperature change in a rotating member composed of members having different linear expansion coefficients, particularly in a high speed rotating member such as a polygon mirror motor. The present invention relates to the structure of a rotating body that suppresses the occurrence of vibration due to.

[0002]

2. Description of the Related Art A polygon mirror motor shown in FIG. 4 can be cited as an example of a rotating body composed of members having different linear expansion coefficients. Conventionally, the polygon mirror motor has been used as a laser scanner for digital copying, laser printers, etc., and its rotation speed is extremely high at about 10,000 to 30,000 RPM. Therefore, as the bearing, a dynamic pressure air bearing or the like that can be rotationally supported without contact is used. The polygon mirror 1 is fitted to the convex portion 13 at the end of the rotor 2 and is pressed and fixed to the rotor 2 by a corrugated spring 17 sandwiched between the polygon mirror 1 and the balance plate 16, and a spiral groove formed on the outer peripheral surface 14 of the rotor 2. The bearing 15 is supported by the dynamic pressure bearing 4 between the bearing 15 and the inner circumference of the bearing 5, and rotates at high speed. The material of the rotor 2 is easy to cut, and the same aluminum alloy as the material of the general polygon mirror 1 is used. Inside the rotor 2, an annular magnet 10 that forms a magnetic circuit for driving and a yoke 19 made of iron are arranged. The yoke 19 has a cylindrical shape with a bottom, and a screw 18 is screwed into a screw hole 20 provided at the bottom to be fixed to the rotor 2 together with the balance plate 16. The yoke 19 may be fixed to the rotor 2 by adhesion. Reference numeral 22 is a recess for preventing the head of the screw 18 from protruding.
An escape portion 21 for preventing contact with the yoke 19 is formed in the cylindrical portion of the inner peripheral portion of the rotor 2 near the fastening portion with the yoke 19.

A rotor 2 having a polygon mirror 1 and the like assembled therein is inserted into a bearing 5 with a dynamic pressure generating gap of several μm to several tens of μm, and a base 8 fixed to the bearing 5 is provided.
The rotor driving coil 9 is fitted and fixed to the central columnar portion of the. The coil 10 and the annular magnet 9 form a motor unit. Further, a pair of annular magnets 11 and 12 are arranged so as to face each other on the upper outer periphery of the central columnar portion of the base 8 and the inner periphery of the balance plate 16 to form a magnetic thrust bearing. The temperature of the rotor 2 changes due to a change in ambient temperature, heat generated by the driving coil 9, heat generated by air friction loss of the dynamic pressure bearing, heat generated by friction of the polygon mirror 1 with air, and the like. Due to this temperature change, the two members (the rotor 2 and the yoke 1) forming the rotor 2 and having different linear expansion coefficients are formed.
9) moves relatively and an imbalance occurs. The unbalanced motor causes vibrations due to rotation, which become more noticeable as the rotation speed increases.

[0004]

When fixing members having different linear expansion coefficients, such as the rotor 2 made of aluminum and the yoke 19 made of iron, as shown in FIG. 4, a gap (escape portion 2) is formed near the fixing portion.
1) is provided, and the yoke 19 is provided below it.
The outer peripheral portion is in contact with the inner peripheral portion of the rotor 2 at some point. In the case of such a structure, the rotor 2 and the yoke 19 are
A change in temperature causes a difference in expansion and causes relative movement. For example, if a temperature rise occurs due to heat generation of the motor itself during operation, an imbalance change will occur accordingly, and a change will occur in the vibration at the initial stage of start-up and the vibration after warm-up. The vibration vibrates the surrounding mechanical system and optical system, and in the case of a laser beam printer, the printing is disturbed and noise is generated. In view of the above drawbacks, an object of the present invention is to provide an unbalanced change in a rotating body in which two or more parts having different linear expansion coefficients are combined, even if the temperature of the rotating body changes due to heat generation of the rotating body itself or environmental temperature. The object is to provide a rotating body that does not generate vibration even when rotated at high speed without rotating.

[0005]

In order to achieve the above-mentioned object, the present invention is a method of connecting two or more large and small bottomed cylindrical bodies forming a rotating body by connecting the bottoms of the bottomed cylindrical bodies to form a cylinder. Stacked so that the parts do not touch. Further, in coupling of two or more large and small cylindrical bodies constituting the rotating body, only a part of the cylindrical portion of the cylindrical body in the circumferential direction is brought into contact with each other.

[0006]

[Operation] In this way, only the bottom of the bottomed cylinder is joined,
If the inner and outer peripheral surfaces of the cylinder do not contact, the temperature of the rotating body changes, and even if there is a difference in expansion and contraction between the inner cylinder and the outer cylinder due to the difference in linear expansion coefficient, the force acting on the cylinder is It occurs only at the bottom part that is joined by, so that the center of gravity does not change even if deformation occurs. Therefore, no change in unbalance occurs and no vibration is generated even when rotating at high speed. In addition, when the inner and outer peripheral surfaces of the cylindrical part of the cylindrical body are in contact with each other in the circumferential direction, centering of the inner and outer cylindrical body is ensured. Even if a difference in expansion and contraction occurs between the inner cylinder and the outer cylinder due to the difference in expansion coefficient, the force acting on the cylinder is concentrated at the contact point. However, the contact point is fixed and cannot move, and the shape of the member between the contact points changes to absorb the force. Therefore, the center of gravity of the deformed member does not change, the unbalance does not change, and vibration does not occur even at high speed rotation.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to one embodiment shown in the drawings.
FIG. 1 shows a first embodiment to which the present invention is applied. This motor includes a polygon mirror 1, a rotating portion including a rotor 2 and a bearing,
It is composed of a fixed part including a base, and the same reference numerals as those in FIG. 4 indicate the same parts. The rotating part of the motor comprises a balance plate 16, a wavy spring 17, a polygon mirror 1, a rotor magnet 12, a rotor 2, a yoke 19, a drive magnet 10 and a screw 18.

A herringbone type groove 15 for generating dynamic pressure is formed on the outer periphery of the cylindrical portion of the bottomed cylindrical rotor 2.
The surface is subjected to surface treatment such as plating to prevent corrosion and wear. The polygon mirror 1 is fitted to the rotor end portion 13 and is fixed to the rotor 2 via a corrugated spring 17 so that the mirror surface accuracy does not deteriorate due to assembly. The balance plate 16 is fixed to the bottom portion of the rotor 2, and has a role of pressing the spring 17 for fixing the mirror, a role of providing a portion for correcting unbalance after assembly, and a role of a carrying handle. Inside the rotor 2, an iron yoke 19 that constitutes a magnetic circuit for generating rotational torque and a drive magnet 12 that constitutes a thrust magnetic bearing.
Are placed one on top of the other. The cylindrical portion of the bottomed cylindrical yoke 19 is provided with a gap 21 for preventing contact with the rotor 2 over the entire circumference, and is fixed to the rotor 2 by a screw 18 at the bottom portion. The screws 18 are evenly arranged at two places.

The fixed portion of the motor is the base magnet 1
1, a base 8 having a columnar portion, a coil 9, a core 23, and a bearing 5. The base magnet 11 is installed in the columnar portion at a position facing the rotor magnet 12,
It constitutes a thrust magnetic bearing. The coil 9 has a core 23 disposed inside and is fixed to the columnar portion facing the drive magnet 10. The base 8 is fixed to the bearing 5 with screws. Similar to the outer surface of the rotor 2, the inner surface of the bearing 5 is surface-treated with alumite or the like to prevent corrosion and wear. The balance plate 16, the polygon mirror 1, the rotor 2, the bearing 5, and the base 8 are all made of aluminum alloy so that mechanical distortion due to temperature change and misalignment between parts are unlikely to occur. Due to its small advantages, the startup time is shortened.

The rotating portion mainly composed of the rotor 2 is inserted into the fixed portion mainly composed of the bearing 5 with a gap of several μm to several tens of μm in the circumferential direction to form a dynamic pressure air bearing and rotate. As a result, pressure is generated to hold the rotating portion in the circumferential direction. The thrust direction is levitationally supported by a magnetic thrust bearing that utilizes the attractive force of the pair of magnets 11 and 12. Due to the mechanical interlocking configuration of the components, the rotating part is associated with a significantly greater imbalance than is normally available during assembly. Therefore, many rotors 2 need to be corrected for imbalance. Holes 24 and 24 'are opened in the balance plate 16 and the end portion of the rotor 2 by cutting with a drill as needed to correct the imbalance.

As described above, since only the bottom of the bottomed cylindrical body is joined and the inner and outer peripheral surfaces of the cylindrical portion are not in contact with each other, the temperature of the rotor changes and the difference in linear expansion coefficient causes the rotor 2 and the yoke 19 to be different. Even if a difference in expansion and contraction occurs, the force acting on the cylindrical portion is generated only at both bottom portions joined by the screw 18, and even if deformation occurs, the center of gravity does not change. Therefore, no change in unbalance occurs and no vibration is generated even when rotating at high speed.

Next, a second embodiment to which the present invention is applied will be described with reference to FIGS. This motor is a polygon mirror 1,
It is composed of a rotating portion including the rotor 2, a bearing, and a fixed portion including a base, and the same reference numerals as those in FIG. 1 indicate the same parts. This embodiment is the same as the rotor 2 in the first embodiment.
Three convex portions 2 are formed at equal intervals on the inner periphery of the opening end of the convex portion 2 a, and the convex portions 2 a abut the outer periphery of the yoke 19.
Therefore, the rotor 2 and the yoke 19 can be centered and the positional accuracy is improved.

As described above, since only the bottom of the bottomed cylindrical body is connected and the inner and outer peripheral surfaces of the cylindrical portion are not in contact with each other, the temperature of the rotating body changes, and the rotor 2 and the yoke 19 differ in linear expansion coefficient. Even if a difference in expansion and contraction occurs, the force acting on the cylindrical portion is generated only at both bottom portions joined by the screw 18, and even if deformation occurs, the center of gravity does not change. Therefore, there is no change in unbalance, vibration does not occur even when rotating at high speed, and since the convex portion 2a abuts the outer circumference of the yoke 19, the rotor 2 and the yoke 19 can be centered and the positional accuracy is improved. To do.

[0014]

[Modification] The above-described embodiment is an example of using the present invention, and various modifications can be made without departing from the gist of the present invention. For example, fixing with screws can be replaced with fixing with adhesive or welding. The number of cylindrical bodies, the fixed positions and the number of convex portions can be appropriately set, and the fixed positions and the contact positions on the convex portions are preferably equidistant, but the effects of the present invention can be obtained even if they are not equidistant. Further, the material is not limited to aluminum alloys and iron-based materials, but copper alloys and resin materials can be used.

In the case of the second embodiment, since the workability of forming the convex portion 2a on the rotor 2 is not so good,
A convex portion 2a is formed on an annular body of an aluminum alloy having an outer diameter smaller than the outer diameter of the rotor, and the convex portion 2a is bonded to the yoke 19 to form an annular step portion on the inner peripheral side of the rotor 2. Then, an annular body may be fitted here. Of course, the annular body may be fixed to the rotor 2. In this way, the hole 2
Since the ring 4 may be opened in the annular body, the thickness of the cylindrical portion of the rotor 2 can be reduced.

Further, in the second embodiment, the yoke 19
May be formed into a cylindrical shape, the convex portion 2a may be extended in the axial direction, and the yoke may be bonded and fixed by the convex portion. In this case, the shape of the yoke is simplified and a yoke obtained by cutting a pipe can be used. When the convex portion 2a is fixed to the yoke 19, the force acting on the cylinder is concentrated at the contact point even if the temperature changes and a difference in expansion and contraction between the annular body and the yoke 19 occurs due to the difference in linear expansion coefficient. However, the contact point is fixed and cannot move, and the shape of the member between the contact points changes to absorb the force. Therefore, the center of gravity of the deformed member does not change, the unbalance does not change, and vibration does not occur even at high speed rotation.

[0017]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, in a high-speed rotating body, when connecting members having different linear expansion coefficients, in connecting two or more large and small cylindrical bodies forming the rotating body, whether the cylindrical bodies contact each other or not. Since only a part of the cylindrical body is in contact with the rotating body, there is no change in the unbalance even if there is a change in the temperature of the rotating body due to the simple structure. Is obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a motor that is a first embodiment of the present invention.

FIG. 2 shows a sectional view of a motor that is a second embodiment of the present invention.

FIG. 3 is a sectional view taken along line AA of FIG.

FIG. 4 shows a cross-sectional view of a motor that is a conventional coupling example.

[Explanation of symbols]

 1 Polygon mirror 2 Aluminum rotor 5 Bearing 19 Iron yoke

Claims (2)

[Claims] 1. A rotary body comprising two or more large and small bottomed cylindrical bodies made of members having different linear expansion coefficients, the two bottomed cylindrical bodies being fixed at the bottom of the bottomed cylindrical body, Rotating body facing each other with a space so as not to contact. 2. A rotary body comprising two or more large and small cylinders made of members having different linear expansion coefficients, and two or more cylinders being overlapped with each other at a space, and a part of the circumference of the facing portion. A rotating body that has a convex portion and makes them contact with each other at a part in the circumferential direction.