JPH0946953A - Motor and laser beam printer using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the efficiency of a motor and stabilize its rotation in a high-speed rotary region while reducing the diameter of its rotary shaft without increasing its shaft deflection, by making the maximum interval between its oil dynamic-pressure fluid bearings not smaller than the thickness of its rotary magnet and not larger than the double of the thickness, and by making the position of the center of the maximum interval fall within the scope of the thickness of its rotary magnet. SOLUTION: A housing 6 made of an oil-impregnated material is fastened, while being passed through the center of a stator coil 5 of a motor, to a printed board 1 whereon a driving IC 2, socket 3, yoke 4 and the stator coil 5 are mounted, and a sleeve 7 is formed in this housing 6 for a shaft 8 to be attached to it in a rotatable way. On the surface of the shaft 8, grooves 9a, 9b constituting oil dynamic-pressure fluid bearings are so engraved that the maximum interval (X) between them is made not smaller than the thickness (H) of a rotary magnet 12 and not larger than 2H. The shaft 8 is so attached to the sleeve 7 that the position of a center (P) of the maximum interval X falls within the scope of the thickness H of the rotary magnet 12. Thereby, the motor can be rotated without increasing its shaft deflection even when the diameter of the shaft 8 is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor and a laser beam printer using the same.

[0002]

2. Description of the Related Art In recent years, as laser beam printers have become smaller in size, their internal parts, for example, polygon mirror drive motors (scanner motors) for scanner units have been improved.
Also, it is desired that the size be small and the shaft runout be small.

Generally, a scanner motor drives a polygon mirror with high precision to scan a reflected light beam of a laser accurately and at high speed. As a bearing structure, a ball bearing structure, a fluid bearing structure or the like is used.

For example, in the case of a ball bearing structure, a rotating shaft having a diameter of about 4 to 6 mm is generally produced because it is advantageous in terms of cost, and a fluid bearing structure also follows this and rotates. The diameter of the shaft is about 4 to 6 mm.

Comparing the fluid bearing structure and the ball bearing structure, the fluid bearing structure is quieter and less expensive than the ball bearing structure because the rolling noise of the balls is low. It is often used for motors with rotational speed.

As one of the motors of this fluid bearing structure, for example, there is a scanner motor of hydraulic fluid pressure bearing structure, and this scanner motor is a sleeve of a housing 61 fixed to a printed circuit board 60 as shown in FIG. 62
A rotary shaft 63 is rotatably provided on a portion of the rotary shaft 63, and a flange 65 on which a drive magnet 64 is mounted is mounted on the rotary shaft 63.
A polygon mirror 66 and the like are supported, and a stator 67 is arranged on the yoke 67 on the housing 61 so as to face the driving magnet 65.

In this case, the rotating shaft 63 having a diameter of about 4 to 6 mm
A groove 69 for generating dynamic pressure is engraved on the outer peripheral surface of the rotary shaft 63.
A radial gap between the sleeve 62 and the sleeve 62 is set to, for example, about 5 μm, and oil is applied to the gap to rotate the rotary shaft 63 and the sleeve 6
The contact friction with 2 is reduced.

In the case of a motor of this type of bearing structure, the bearing span L on the sleeve 62 side and the rotary shaft 63 are considered in terms of support strength.
Has a relationship of D / L with the diameter D of the rotating shaft 63. For example, if the diameter D of the rotating shaft 63 is reduced, the bearing span L needs to be lengthened accordingly. Manufacturing (processing) of bearing holes becomes difficult.

By the way, in recent years, there has been a trend toward higher color printing, higher image quality, and higher speed printing in printers, and the above-mentioned rotation speed of about 10 Krpm is insufficient for a scanner motor, and rotation of about 20 to 30 Krpm is required. Number is required.

However, when the scanner motor having the above-mentioned hydraulic fluid pressure bearing structure is used in such a high speed rotation range, the oil applied between the rotary shaft 63 and the sleeve 62 is generated by centrifugal force and friction generated by high rotation. The resulting rise in temperature causes scattering and evaporation, which shortens the life of the motor.

Further, in the rotating shaft 63 having a diameter of 4 to 6 mm,
Since the friction surface with the sleeve 62 is wide, mechanical loss increases, and the rotation efficiency of the motor decreases.

Therefore, in order to reduce the friction between the rotary shaft 63 and the sleeve 62, if the radial clearance is increased, the diameter is 4 to 4.
Even with the 6 mm rotary shaft 63, the shaft runout becomes large, and it cannot be used as a scanner motor that accurately scans a laser at high speed.

[0013]

In the above-mentioned motor having the conventional hydraulic fluid pressure bearing structure, when the motor is used in a high rotation range up to about 20 to 30 Krpm, it is applied between the rotation shaft and the sleeve. The oil was scattered and evaporated,
There is a problem that the life of the motor is shortened.

Further, in the rotating shaft having a diameter of about 4 to 6 mm, there is a problem that the frictional surface with the sleeve is wide, resulting in a large loss both mechanically and electrically, and the rotation efficiency of the motor is lowered.

The present invention has been made to solve the above problems, and an object thereof is to provide a motor that can be used in a high rotation range and a laser beam printer using the same.

[0016]

In order to achieve the above-mentioned object, the invention according to claim 1 is such that a rotary shaft rotatably supported by a sleeve provided in a housing and a flange on the rotary shaft. A supported rotating magnet, a stator coil arranged around the rotating magnet to face the rotating magnet, and drives the rotating magnet, and at least one lower part on the inner wall surface of the sleeve or the outer peripheral surface of the rotating shaft. The maximum bearing spacing from the uppermost one to the lowermost one is greater than or equal to the thickness of the rotary magnet and less than or equal to twice the thickness of the rotary magnet, and less than the thickness of the rotary magnet. And a groove for dynamic pressure arranged such that the center point of the maximum bearing spacing is located within the range.

In this case, by forming the groove for dynamic pressure in the above-mentioned forming range, even if the shaft diameter of the rotating shaft is reduced to about 2 mm, the shaft runout of the rotating shaft is reduced and the motor is stably rotated. be able to.

The reason is as follows.

Since the maximum bearing spacing is specified to be equal to the thickness of the magnet capable of supporting the generated rotational force or twice the thickness of the magnet capable of performing accurate sleeve processing, the rotational accuracy is improved and at the same time. The required and sufficient bearing performance can be obtained.

Further, since the center point of the bearing gap is located within the thickness range of the rotary magnet, the force acting on the rotary magnet can be efficiently received and the short maximum bearing gap can be effectively used.

Further, according to the above-mentioned motor structure, since the inner rotor type is adopted, the total weight of the rotary magnet and the flange can be reduced, and the maximum diameter of these rotary parts can be kept small. Even if is used, the rotational runout can be suppressed.

Further, since the rotating portion has a simple structure in which a rotating magnet is attached to the rotating shaft via a flange,
It is easy to reduce the weight and suppresses rotational runout.

According to a second aspect of the present invention, a sleeve rotatably supported by a shaft fixed to the housing, a rotary magnet supported by the sleeve via a flange, and a rotary magnet facing the circumference of the rotary magnet. And a stator coil for driving the rotating magnet, and at least one on the inner wall surface of the sleeve or one on the outer peripheral surface of the shaft are formed downward, one from the uppermost one to the lowermost one. Is arranged such that the maximum bearing spacing is equal to or greater than the thickness of the rotary magnet and is equal to or less than twice the thickness of the rotary magnet, and the center point of the maximum bearing spacing is located within the range of the thickness of the rotary magnet. And a groove for dynamic pressure control.

In this case, the shaft is fixed and the sleeve rotates, but in this case as well, the center point of the bearing interval is located within the thickness range of the rotary magnet, so that the force acting on the rotary magnet is efficiently It receives well and suppresses rotational shake.

Further, according to the invention of claim 3, a rotating shaft rotatably supported by a sleeve provided in the housing,
A rotary magnet supported on this rotary shaft via a flange,
A stator coil that is disposed around the rotary magnet to face the rotary magnet, and a stator coil that drives the rotary magnet, and at least one upper coil and one lower coil are formed on the inner wall surface of the sleeve. So that the maximum bearing spacing is equal to or greater than the thickness of the rotary magnet and is equal to or less than twice the thickness of the rotary magnet, and the center point of the maximum bearing spacing is located within the range of the thickness of the rotary magnet. And a slide bearing portion arranged.

In this case, since the sliding bearing portion is formed on the inner wall surface of the sleeve at the same position as the groove for dynamic pressure,
Rotational shake is suppressed in the same manner as above.

According to a fourth aspect of the present invention, in the motor according to any one of the first to third aspects, the housing and the sleeve are formed of an oil-impregnated metal material.

In this case, since the housing is an oil-impregnated metal material, it is relatively soft as compared with brass or aluminum,
A bearing hole smaller than before can be machined with high precision. Further, since the sleeve is an oil-impregnated metal material, even if the oil is consumed due to friction when the motor is used at a high rotation speed for a long time, the oil can be supplemented, so that the life of the motor can be extended.

Further, the invention according to claim 5 is the motor according to any one of claims 1 to 3, characterized in that the shaft diameter of the rotary shaft is, for example, 2 mm.

In this case, since the shaft diameter of the rotary shaft is 2.5 mm,
The contact surface between the sleeve and the rotating shaft becomes narrow. Therefore, when the motors are rotated at high speed, friction between them is reduced, and the rotation efficiency of the motors is improved.
It can be used in the high rotation range up to about 20 to 30 Krpm.

As a result, the life of the motor can be extended, and the motor can be downsized by the reduction of the shaft diameter of the rotary shaft.

According to a sixth aspect of the present invention, in the motor according to the first aspect, a polygon mirror fixed to the upper portion of the flange is further provided.

In this case, a small motor having a fixed polygon mirror and a small shaft diameter can be used as a deflection scanning unit of a laser beam printer.

Further, the invention according to claim 7 is characterized in that the motor according to claim 6 is used for a deflection scanning section of a laser beam printer.

In this case, the laser can be accurately scanned at a high speed without rotating the shaft even with a rotating shaft having a diameter of about 2 mm.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a plan view showing the structure of a scanner motor which is one embodiment of the motor according to the present invention, and FIG. 2 is a sectional view taken along the line AA 'of the scanner motor shown in FIG.

In the figure, reference numeral 1 is a printed circuit board of the scanner motor. A metal such as iron is used as a main material of the printed board 1, and each electronic component is mounted by insulating the surface of the board. As the electronic parts, for example, a motor driving IC 2, a socket 3, a polygonal yoke 4, a plurality of stator coils (motor driving coils) 5 radially arranged on the yoke 4, a hall element (not shown), etc. are mounted. ing. At the center position of the stator coil 5 of the printed circuit board 1, a housing 6 formed by processing (molding) an oil-impregnated metal material or the like penetrates the circuit board 1 and is fixed. Since the oil-impregnated metal material used for the housing 6 is a relatively soft material as compared with brass and aluminum, fine processing such as axial hole processing can be accurately performed.

A bearing tube, that is, a sleeve 7 is formed at the center of the housing 6 so as to penetrate therethrough in the vertical direction. The sleeve 7 has a shaft diameter of, for example, φ2 ± 0.00
A shaft (rotating shaft) 8 processed with an accuracy of 1 mm or the like is rotatably attached. On the surface of the shaft 8, a plurality of spiral grooves in the axial direction, that is, a plurality of continuous V-shaped grooves 9a and 9b extending in the rotation direction are engraved. Shaft 8
The rotation of itself is stabilized (dynamic pressure fluid bearing structure). The spiral grooves 9a and 9b may be formed on the inner wall surface of the sleeve 7.

A flange (a part of the rotor) 10 is fixed to the shaft 8. A polygon mirror 11 as a rotary polygon mirror is fixed to the upper portion of the flange 10. A donut-shaped magnet (rotating magnet) 12 is attached to the end of the flange 10 so as to face the stator coil 5 fixed to the substrate 1. Next, the operation of the scanner motor will be described.

In this scanner motor, the motor drive I
When a drive signal is applied to the stator coil 5 from C2,
A magnetic field is generated, a driving force acts on the magnet 12 in a certain direction, and the rotor portion including the flange 10 rotates in a certain direction together with the shaft 8.

At this time, the grooves 9a, 9 formed in the shaft 8
By b, a dynamic pressure is generated between the shaft 8 and the sleeve 7, and even an extremely thin shaft 8 having a shaft diameter of 2 mm can be stably rotated without swinging.

When the positions of the grooves 9a and 9b formed on the shaft 8 were changed variously, the maximum bearing spacing X was equal to or more than twice the thickness (height) H of the magnet 12, that is, the thickness of the magnet. H ≦ maximum bearing spacing X ≦ magnet thickness H × 2, and the midpoint P of the spacing X is
It has been found that when the thickness (height) H of the magnet 12 is within the range, the rotation of the shaft 8 is stable and the axial runout is minimized.

Here, the maximum bearing spacing X means the uppermost groove 9a formed on the shaft 8 to the lowermost groove 9a.
It is the interval to the lower limit of b.

By engraving the grooves 9a and 9b within the maximum bearing spacing X, the rotation of the shaft 8 is most stable.

As another arrangement example of the grooves 9a and 9b,
As shown in FIG. 3A, the middle point P is shifted to the lower side of the width H of the magnet 12 to form the upper and lower grooves 9a and 9b, and as shown in FIG. The magnet 12
There may be a case where the upper and lower grooves 9a and 9b are formed by being shifted to the upper side of the width H of. In this case, the positional relationship between the shaft 8 and the magnet 12 can be variously changed when the height of the motor is limited.

Here, the structure of this scanner motor and the relationship of centrifugal force, bearing loss, rotation speed, etc. will be described.

First, the relationship between the radius of the motor shaft and the centrifugal force acting on the oil will be described. The shaft radius is r,
Assuming that the oil density is ρ, the rotation speed is ω, and the centrifugal force acting on the oil is F, the relationship between them is as shown in the following equation.

F infinity ρ × r × ω × 2 According to this equation, it is understood that the centrifugal force becomes smaller and the oil is scattered less as much as the diameter of the shaft is smaller than in the conventional case.

The bearing loss is given by the following equation.

Loss infinity r × 3 × ω × 4 According to this formula, when the rotation speed increases to 10 to 20 Krpm, the loss increases 16 times, but if the shaft radius is halved, it will be about twice. .

Further, since the housing 6 is formed by processing the oil-impregnated metal material, the oil lost due to evaporation or other reasons is replenished from the metal material itself, so that the life of the motor is extended. Since the inner diameter of the sleeve 7 is small, the deformation of the hole during metal sintering is small, and the inner diameter of the sleeve 7 can be processed accurately.

Thus, according to this scanner motor,
Since the oil-impregnated metal material, which is a relatively soft material, is used for the housing 6, even if the hole diameter of the sleeve 7 portion is about 2 mm, it can be accurately processed and the radial gap between the sleeve 7 and the shaft 8 can be reduced. Therefore, the shaft diameter of the shaft is 2 mm, which is less than half of the conventional shaft, and the motor can be used in a high rotation range of about 10 to 20 Krpm, and the motor and the entire printer can be downsized. .

When the shaft 8 has a shaft diameter of 2 mm, the weight of the flange 10, the rotary polygon mirror 11 and the magnet 12 reduces the supporting force. However, by reducing the radial gap, the shaft inside the sleeve 7 is reduced. While the rattling of 8 is reduced, the oil content (lubrication component) oozes out in the radial gap portion by using the oil-impregnated metal material for the housing 6, and the lubrication state is maintained for a long period of time. The smoothness can be maintained for a long time, and the life of the motor can be extended.

Further, since the oil-impregnated metal material used for the housing 6 is relatively soft as compared with brass or the like, the vibration generated in the bearing sliding portion is absorbed by the housing 6 and the noise of the motor is reduced. Can also contribute.

Next, a laser beam printer using the scanner motor will be described. FIG. 4 is a diagram showing a laser beam printer using a scanner motor as a deflection scanning unit.

In the figure, reference numeral 41 is a paper feed unit such as a tray. An image forming unit 42 transfers the image information onto the sheet supplied from the tray 41. An image fixing unit 43 fixes the image information transferred on the paper to the paper. Reference numeral 44 denotes a deflection scanning unit, which is the scanner motor itself. The deflection scanning unit 44 is fixed by screws or the like in a narrow space above the housing of this printer. The deflection scanning unit 44 emits a laser beam from a laser light source unit (not shown) mounted on the substrate 1, reflects the laser beam on the polygon mirror 11 and the reflection plate 45, and outputs the laser beam to the image forming unit 42. Four
Reference numeral 6 is each conveying means such as a roller.

In the case of this laser beam printer, the polygon mirror 11 fixed to the upper portion of the flange 10 of the scanner motor, which is the deflection scanning unit 44, is driven at high speed without any axis shake,
Since the laser light emitted from the laser light source unit on the substrate of the scanner motor is reflected toward the image forming unit 42 side, it is possible to perform deflective scanning accurately at high speed.

According to this laser beam printer, since the scanner motor is used for the deflection scanning section 44, the laser beam can be deflected and scanned at high speed and accurately.

The present invention is not limited to the above embodiment.

In the above-mentioned embodiment, the bearing structure is constructed by engraving the grooves 8a and 9b for dynamic pressure at predetermined positions of the shaft 8. However, instead of the grooves 9a and 9b, a simple ring-shaped slide is provided on the sleeve 7 side. The same effect can be obtained by providing the bearing portion.

In the above embodiment, an example in which the shaft 8 having a shaft diameter of 2 mm is rotatably supported by the housing 6 of the scanner motor and the shaft 8 rotates is described.
As shown in FIG. 5, the grooves 50a, 5 are provided at predetermined positions on the outer peripheral surface.
0b-formed shaft 51 having a shaft diameter of 2 mm and integrally fixed to the housing 52, the yoke 4, and the stator coil 5
And the like are attached to the printed circuit board 53, while the magnet 54 and the polygon mirror 55 corresponding to the stator coil 5 are integrally fixed to the flange 56 to form the flange 56.
The sleeve portion 56a provided on the shaft 51 may be rotatably supported by the shaft 51 to rotate the flange 56. An oil-containing metal material is also used for the housing 52 in this case.

In this case, the flange 56 is formed by hollowing out the portion other than the sleeve portion 56a, and the weight supported by the extremely thin shaft 51 having a shaft diameter of 2 mm is reduced, so that the bearing loss can be reduced. .

That is, in the present invention, as long as the groove for dynamic pressure is formed in either the sleeve portion or the shaft and the sleeve portion and the shaft slide and rotate with respect to each other, another bearing structure is provided. It is also applicable to, for example, a ball bearing structure.

[0065]

As described above, according to the present invention, one dynamic pressure groove is formed below the inner wall surface of the sleeve or the outer peripheral surface of the rotary shaft, and the maximum bearing of these grooves is formed. The spacing is more than twice the thickness of the rotating magnet and less than twice, and the center point of the maximum bearing spacing is positioned within the range of the thickness of the rotating magnet. The rotation can be stabilized at times.

Further, since the housing and the sleeve are made of the oil-impregnated metal material, the bearing hole smaller than the conventional one can be machined with high accuracy. Also, since the sleeve is an oil-impregnated metal material,
Even when the motor is used at high rotation speed for a long time, the oil content can be supplemented from the oil-containing metal material itself even if the oil content is consumed due to friction, so that the life of the motor can be extended.

Further, since the shaft diameter of the rotary shaft is 2 mm, the contact surface between the sleeve and the rotary shaft is narrowed, friction between them is reduced, and the rotational efficiency of the motor is improved.

Therefore, the motor can be used in a high rotation range up to about 20 to 30 Krpm.

Since the polygon mirror is fixed to the rotary shaft, this scanner motor can be used as the deflection scanning unit of the laser beam printer.

When this scanner motor is used as a deflection scanning unit of a laser beam printer, it has a diameter of 2
The laser can be accurately scanned at high speed without any axis shake even on the mm rotation axis.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a scanner motor of the present invention.

FIG. 2 is a diagram showing a cross section taken along the line AA ′ of the scanner motor of FIG.

FIG. 3A is a diagram showing another arrangement example in which the midpoint P of the grooves 9a and 9b is shifted to the lower side of the width H. FIG. 9B is a diagram showing another arrangement example in which the midpoint P of the grooves 9a and 9b is shifted to the upper side of the width H.

FIG. 4 is a diagram showing a laser beam printer using this scanner motor for a deflection scanning unit.

FIG. 5 is a sectional view showing another embodiment of the scanner motor of the present invention.

FIG. 6 is a diagram showing a conventional scanner motor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Printed circuit board, 2 ... Motor drive IC, 3 ... Socket, 4 ... Yoke, 5 ... Stator coil, 6 ... Housing, 7 ... Sleeve, 8 ... Shaft, 9a, 9b ... Groove, 1
0 ... Flange, 11 ... Polygon mirror, 12 ... Magnet.

Claims (7)

[Claims] 1. A rotary shaft rotatably supported by a sleeve provided in a housing; a rotary magnet supported by the rotary shaft via a flange; A stator coil that drives a rotating magnet;
At least one upper one and one lower one are formed on the inner wall surface of the sleeve or the outer peripheral surface of the rotary shaft, and the maximum bearing spacing from the uppermost one to the lowermost one is equal to or larger than the thickness of the rotary magnet, Less than twice the thickness of the rotating magnet,
And a groove for dynamic pressure which is arranged such that the center point of the maximum bearing spacing is located within the range of the thickness of the rotary magnet. 2. A sleeve rotatably supported by a shaft fixed to the housing; a rotary magnet supported by the sleeve via a flange; and a rotary magnet disposed to face the circumference of the rotary magnet. A stator coil for driving the
At least one upper one and one lower one are formed on the inner wall surface of the sleeve or the outer peripheral surface of the shaft, and the maximum bearing spacing from the uppermost one to the lowermost one is equal to or more than the thickness of the rotating magnet, A groove for dynamic pressure, which is not more than twice the thickness of the magnet and is arranged such that the center point of the maximum bearing spacing is located within the range of the thickness of the rotary magnet. The motor to drive. 3. A rotary shaft rotatably supported by a sleeve provided in the housing; a rotary magnet supported by the rotary shaft via a flange; A stator coil that drives a rotating magnet;
At least one upward and one downward on the inner wall surface of the sleeve
And the maximum bearing spacing from the uppermost one to the lowermost one is not less than the thickness of the rotating magnet and not more than twice the thickness of the rotating magnet, and within the range of the thickness of the rotating magnet. And a slide bearing portion arranged so that the center point of the maximum bearing spacing is located in the motor. 4. The motor according to claim 1, wherein the housing and the sleeve are made of an oil-impregnated metal material. 5. The motor according to claim 1, wherein the rotary shaft has a shaft diameter of 2.5 mm or less. 6. The motor according to claim 1, further comprising a polygon mirror fixed to an upper portion of the flange. 7. A laser beam printer using the motor according to claim 6 for a deflection scanning unit.