JP3374572B2 - Light deflection device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical deflector, and more particularly, it can attenuate the transmission of vibration generated by the rotation of a rotating body and prevent the transmission of heat generated from a drive unit. The present invention relates to a light deflector.

[0002]

2. Description of the Related Art In a conventional optical deflector, a DC motor directly drives a rotary polygon mirror, and when the rotary polygon mirror is rotated at a high speed, a radial gap structure using an iron core coil is adopted. When rotating at a low speed, it is general to use an axial gap using an air-core coil. A technique for realizing the above optical deflector at low cost is disclosed in Japanese Utility Model Laid-Open No. 3-129918. As shown in FIG. 6, in this optical deflector, a hub 22 is fixed to a rotary shaft 1, and a rotary polygon mirror 13 is attached to the hub 22. The rotating shaft 1 is provided with rolling grooves r1 and r2. The rolling grooves r1, r2, bearing outer rings 3, 4
And the steel ball 2 inserted between them, two sets of ball bearings are provided, as well as the core 7, coil 8 and magnet 15.
The drive motors are respectively configured by the above. The rotary shaft 1 is rotatably supported by the two sets of ball bearings and the preload spring 5, and is driven by the drive motor.

[0003]

In recent years, the image quality of laser printers, copying machines, facsimile machines and the like has been rapidly improved. For this reason, there is an increasing need for a low-cost optical deflector having both high speed and high reliability, but it is difficult for the technology disclosed in the above-mentioned publication to sufficiently meet this requirement. . When the motor housing is made of a metal, for example, an aluminum alloy for the purpose of radiating heat from the iron core coil and improving the mechanical accuracy of the motor housing, the heat from the iron core coil is transferred to the motor housing and then the bearing. Will be transmitted to. For this reason, the lubricating oil of the bearing is deteriorated by heat, or the viscosity of the lubricating oil is reduced to scatter and the lubricating oil is exhausted. Due to such a situation, there is a problem that the bearing and the rotary shaft are in contact with each other and rub against each other, and the life thereof is significantly reduced.

Further, when the motor is rotated at a high speed, vibrations of the rotary shaft and the bearing are transmitted to the motor housing and subsequently to the optical box. Therefore, there is a problem that the mirror, the lens, and the like vibrate, and uneven scanning occurs. An object of the present invention is to eliminate the above-mentioned problems of the prior art, prevent heat generated from a drive unit from being transmitted to a rotating shaft and a bearing, and attenuate the transmission of vibration generated by rotation of a rotating body. It is an object of the present invention to provide an optical deflecting device that is not affected by vibrations in an optical unit mounted in an optical box.

[0005]

In order to achieve the above-mentioned object, the invention of claim 1 is characterized in that a rotary shaft circumferential gap is provided.
A stator consisting of a winding and an iron core facing the rotor
A metal motor housing supported in the circumferential direction of the rotation axis and having a function of a mounting flange for the optical box; a bearing rotatably supporting the rotating body; and a metal motor housing provided between the metal motor housing and the bearing, It is characterized in that it is provided with a resin cylindrical sleeve having a low thermal conductivity and a low vibration transmission rate as compared with the metal motor housing. The invention of claim 2 is characterized in that it comprises a sliding radial bearing and a thrust bearing integrally formed on the bottom portion of the cylindrical sleeve to support the rotating body in the thrust axial direction.

[0006]

According to the first aspect of the present invention, the resin cylindrical sleeve has a low thermal conductivity and cannot keep the heat generated in the winding in the bearing. Therefore, the lubricating oil of the bearing is deteriorated,
It becomes possible to prevent exhaustion. Further, the cylindrical sleeve makes the vibration generated when the rotary body rotates transparently attenuate, and the vibration is not transmitted to the metal motor housing. Therefore, it is possible to prevent the optical unit mounted in the optical box from being vibrated without being transmitted to the optical box. According to the invention of claim 2, the cylindrical sleeve can block heat and vibration. Therefore, it is possible to prevent the heat generated in the winding from being transmitted to the sliding radial bearing and the vibration from the sliding radial bearing being transmitted to the optical box. Further, the thrust bearing integrally formed with the cylindrical sleeve makes it possible to damp transmission of vibrations in the thrust axis direction of the rotating body, that is, in the rotation axis direction.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical deflector of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a partial cross-sectional view showing the configuration of an embodiment of a laser printer to which an optical deflector is applied. In the figure, 1 is a semiconductor laser that emits a laser beam 12, 2 is a rotary polygon mirror that reflects the laser beam 12 emitted from the semiconductor laser 1 to an fθ lens group 3 described later, and 3 is composed of lenses 3a and 3b. Fθ lens group, 4 is a drive motor for rotating the rotary polygon mirror 2, 5 is an optical box to which the present optical deflector is attached, 7
Is an optical box cover for covering the light deflecting device and the inner cover 6, and 8 is a laser beam 12 from the rotary polygon mirror 2.
Is a cylindrical mirror that reflects light to the mirror 13, 9 is a frame on which the optical unit is mounted, 10 is a cover that covers the optical unit, and 11 is a photoconductor on which the laser beam 12 reflected by the mirror 13 is irradiated.

FIG. 2 is a sectional view of the optical deflecting device of the first embodiment. FIG. 3 is a sectional view of a portion where the optical deflector shown in FIG. 2 is attached to the optical box 5. In the figure, 18 is a motor drive circuit board, 19 is a holding spring, 20 is a pedestal 22.
It is a rotary shaft to which the rotary polygon mirror 2 is fixed via.
Reference numeral 21 denotes a motor housing having a function of a mounting flange for the optical box 5 and fixed to the optical box 5 by a mounting screw 33. This motor housing 21 is
Usually made of aluminum alloy. Reference numeral 24 denotes a winding wound around an iron core 25, and this winding 24 is supported by the motor housing 21 together with the iron core 25. 26 is a ball bearing that supports the rotary shaft 20;
Reference numeral 7 is a preload spring for preloading the ball bearing 26 and a cylindrical sleeve 30 described later, and 29 is a rotor to which a magnet 28 is attached. Reference numeral 30 denotes a resin cylindrical sleeve into which the ball bearing 26 is fitted, and is made of, for example, a resin having a low thermal conductivity, a vibration transmittance and an elastic coefficient such as nylon 66 or polycarbonate. The rotary polygon mirror 2, the rotary shaft 2
0, the pedestal 22, the rotor 29, and the like constitute a rotating body. The winding 24, the iron core 25 and the magnet 2
A drive unit of the motor is configured by 8.

In the above-described embodiment, first, when an electric current is applied to the winding 24 according to an instruction from a controller (not shown) and the rotating body is rotated by the action of the driving unit,
The winding 24 generates heat, and the heat is transmitted to the iron core 25. This heat is then transferred from the iron core 25 to the motor housing 21. The cylindrical sleeve 30 blocks heat transmitted to the motor housing 21 and prevents the heat from being transmitted to the ball bearing 26. Further, when the rotating body rotates at a high speed, a slight imbalance of the rotating body causes vibrations or vibrations in the ball bearings 26. The vibrations are transmitted and attenuated by the cylindrical sleeve 30, and The vibration transmitted to the housing 21 is suppressed low.

In the optical deflector as described above, the heat blocking effect and the vibration transmission damping effect when the motor housing 21 is made of aluminum alloy and the cylindrical sleeve 30 is made of nylon 66 will be specifically described. . The thermal conductivity of the aluminum alloy is 0.29 ca.
1 / cm / s / K. On the other hand, the nylon 6
6 is 5.8 × 10 ⁻⁴ cal / cm / s / K. From the difference in thermal conductivity as described above, it can be seen that the nylon 66 has a heat insulating effect of 500 times that of the aluminum alloy.

Further, the vibration transmitted to the ball bearing 26 is
The transmission attenuation when passing through the cylindrical sleeve 30 and the motor housing 21 is the transmittance τ ² = 4Z 1 between the two media, that is, the vibration strength of nylon 66 and aluminum alloy.
It can be represented by the formula of Z2 / (Z1 + Z2) ² . Where Z1 is the intrinsic impedance of nylon 66 (k
g / s / cm ² ), Z2 is the inherent impedance of the aluminum alloy.

Z1 is the density of nylon 66 ρ1 =
0.00138 kg / cm ³ , longitudinal elastic modulus E 1 = 2 × 1
Since it is 0 ⁸ kg / cm / s ² , Z1 = ρ1 (E1 /
ρ 1) ^1/2 = 166 kg / s / cm ² . Z2 is the density of the aluminum alloy ρ2 = 0.027k
g / cm ³ , longitudinal elastic modulus E 2 = 7 × 10 ⁸ kg / cm /
Since s ² and Poisson's ratio σ = 0.34, Z 2 = ρ 2
(E2 / ρ2 / (1- σ 2)) 1/2 = 1460kg / s
/ Cm ² .

From the above values, the transmittance of the vibration intensity is τ ² = 4Z1Z2 / (Z1 + Z2) ² = 4 × 166 × 1460 / (166 + 1460) ² = 0.37. Comparing the transmission τ ² = 0.37 of vibration strength of the nylon 66 and the aluminum alloy with the transmission τ ² = 1 of the conventional single member, the former has a vibration of about 2.7 with respect to the latter. It can be seen that there is an effect of doubling.

Next, the cylindrical sleeve 30 is made of nylon 6
A case of using polycarbonate instead of 6 will be described. The thermal conductivity of the aluminum alloy is 0.29.
It is cal / cm / s / K. On the other hand, the polycarbonate has a density of 4.6 × 10 ⁻⁴ cal / cm / s / K. From the difference in thermal conductivity as described above, it can be seen that the polycarbonate has a heat insulating effect 630 times that of the aluminum alloy.

When the vibration transmitted to the ball bearing 26 passes through the cylindrical sleeve 30 and the motor housing 21, the transmission attenuation is between the two media, that is, the transmittance τ ² = 4Z 1 of the vibration strength of the polycarbonate and the aluminum alloy.
It can be represented by the formula of Z2 / (Z1 + Z2) ² . In this case, Z1 is the polycarbonate, and Z2 is the inherent impedance of the aluminum alloy. Z1
Is the density of polycarbonate ρ1 = 0.0012 kg /
cm ³ , longitudinal elastic modulus E 1 = 2.2 × 10 ⁸ kg / cm /
Since s ² , Z1 = ρ1 (E1 / ρ1) ^1/2 = 18
It becomes 8 kg / s / cm ² . As described above, the intrinsic impedance Z2 of aluminum alloy is Z2 = 1460
It is kg / s / cm ² .

From the above values, the transmittance is τ ² = 4Z 1 .Z 2 / (Z 1 + Z 2) ² = 4 × 188 × 1460 / (188 + 1460) ² = 0.4. Comparing the transmittance τ ² = 0.4 of the vibration strength of the above-mentioned polycarbonate and aluminum alloy with the transmittance τ ² = 1 of the conventional single member, the former is about 2.5 times the vibration as compared with the latter. It can be seen that there is a damping effect.

As is clear from the above description, in this embodiment, the cylindrical sleeve 30 having a low heat conductivity and a low vibration transmission rate is provided between the motor housing 21 and the ball bearing 26. The heat generated from the winding 24 stops at the motor housing 21 and is not transmitted to the ball bearing 26. Therefore, it is possible to prevent the lubricating oil of the ball bearing 26 from deteriorating due to heat, and to prevent the viscosity of the lubricating oil from decreasing and scattering to deplete the lubricating oil. Also,
It is possible to prevent the rotating shaft 20 and the ball bearing 26 from coming into contact with each other and rubbing against each other, and shortening the life thereof. In addition, the cylindrical sleeve 30
Vibrates and attenuates vibrations of the rotary shaft 20 and the ball bearing 26 that occur when the rotating body is rotated by the drive motor 4. Therefore, the vibration of the rotating shaft and the bearing causes the motor housing 21
The optical units such as the mirrors 8 and 13 and the fθ lens group 3 mounted on the frame 9 of the optical box 5 do not vibrate through the optical box 5 and the scanning unevenness is generated. Can be prevented. In this embodiment,
Although the case where the cylindrical sleeve 30 is made of nylon 66 and polycarbonate has been described, the present invention is not limited to this.
In the present invention, any other material may be used as long as it has a lower thermal conductivity than the material of the motor housing 21 and that transmits and attenuates vibrations.

Next, a second embodiment will be described with reference to FIG. FIG. 4 is a sectional view of the optical deflector of this embodiment. In the figure, 31 is a sliding radial bearing that supports the rotating shaft 20, and 32 is a thrust bearing that is fitted in the sliding cylindrical sleeve 30 and supports the lower end of the rotating shaft 20. At least one of the contact surfaces of the thrust bearing 32 and the lower end of the rotary shaft 20 has a convex arc, and the rotary shaft 20 is supported by the thrust bearing 32 at one point. Note that other reference numerals in the figure indicate the same or equivalent parts as the corresponding reference numerals in FIG. According to this embodiment, as in the first embodiment, the heat generated from the winding wire 24 is blocked by the cylindrical sleeve 30 and is not transferred to the sliding radial bearing 31. Therefore, the deterioration or depletion of the lubricating oil impregnated in the sliding radial bearing 31 can be reduced, and the life of the sliding radial bearing 31 can be extended. Further, since the sliding radial bearing 31 generates only a small vibration as compared with the ball bearing, the influence of the vibration exerted on the optical box 5 becomes smaller.

Next, a third embodiment will be described with reference to FIG. FIG. 5 is a sectional view of the optical deflector of this embodiment. In the figure, 30 'is a cylindrical sleeve having a bottom. Reference numeral 32 'is a bottom portion integrally formed with the cylindrical sleeve 30', and is a thrust bearing that supports the lower end of the rotary shaft 20. The contact surface at the lower end of the rotary shaft 20 is a convex arc, and the rotary shaft 20 is supported by the thrust bearing 32 'at one point. It should be noted that other reference numerals in FIG.
The same as or equivalent to the corresponding reference numerals in FIG. According to the present embodiment, similarly to the first and second embodiments, the heat transfer to the sliding radial bearing 31 and the transfer of the vibration from the sliding radial bearing 31 to the optical box 5 are performed by the cylindrical sleeve 30 '. , Can be prevented. Further, the cylindrical sleeve 30 'can dampen the vibration of the rotating body in the thrust axis direction, that is, the rotation axis direction by the thrust bearing 32'.

[0020]

As is apparent from the above description, according to the invention of claim 1, the resin cylindrical sleeve has a low thermal conductivity, is extremely hard to transfer heat, and can substantially insulate heat. Therefore, the heat generated from the winding is blocked by the cylindrical sleeve provided between the metal motor housing and the bearing and is not transferred to the bearing. For this reason, it is possible to prevent the lubricating oil of the bearing from being deteriorated by heat, and to prevent the viscosity of the lubricating oil from decreasing and scattering to deplete the lubricating oil. In addition, it is possible to prevent the rotating shaft and the bearing from coming into contact with each other and rubbing against each other, and significantly shortening the life thereof. In addition, the cylindrical sleeve,
It is possible to permeate and dampen vibrations of the rotating shaft and bearings that occur when the rotating body is rotated by the drive motor. Therefore, the vibrations of the rotary shaft and the bearing are not transmitted to the metal motor housing and the optical box, and the optical unit mounted on the frame of the optical box is not vibrated, which causes uneven scanning. Can be prevented.

According to the invention of claim 2, similarly to the invention of claim 1, the cylindrical sleeve transfers the heat generated in the winding to the sliding radial bearing and the vibration from the sliding radial bearing. Transmission to the optical box can be prevented. Further, the cylindrical sleeve can dampen the transmission of vibration in the thrust axis direction of the rotating body, that is, the rotation axis direction, by means of the thrust bearing.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a configuration of an embodiment of a laser printer to which an optical deflecting device is applied.

FIG. 2 is a cross-sectional view showing a cross section of the configuration of the optical deflecting device of the first embodiment.

FIG. 3 is a cross-sectional view of a portion where the optical deflector shown in FIG. 2 is attached to an optical box.

FIG. 4 is a sectional view showing a section of an optical deflecting device of a second embodiment.

FIG. 5 is a sectional view showing a section of an optical deflecting device of a third embodiment.

FIG. 6 is a cross-sectional view showing a cross section of a conventional optical deflector.

[Explanation of symbols]

1 ... Semiconductor laser, 2 ... Rotating polygonal mirror, 3 ... f.theta. Lens group, 4 ... Drive motor, 5 ... Optical box, 7 ... Optical box cover, 9 ... Frame, 11 ... Photoconductor, 12 ... Laser beam, 18 ... Motor drive circuit board, 19 ... Holding spring, 2
0 ... Rotary shaft, 21 ... Motor housing, 22 ... Pedestal, 2
4 ... Winding, 25 ... Iron core, 26 ... Ball bearing, 27 ... Preload spring, 28 ... Magnet, 29 ... Rotor, 30 ... Cylindrical sleeve, 31 ... Sliding radial bearing, 32 ... Thrust bearing.

Claims (2)

(57) [Claims] 1. A rotary polygon mirror, a rotating body comprising a rotating shaft and pedestal like, a driving motor for rotating the rotary member, the optical deflecting device having an optical box having an optical unit, the rotation shaft A metal motor housing that supports a stator composed of a winding and an iron core in the circumferential direction of the rotating shaft, which faces the rotor via a circumferential gap , and has a function of a mounting flange for the optical box. A bearing that rotatably supports the rotating body, and a resin that is provided between the metal motor housing and the bearing and has a lower thermal conductivity and a lower vibration transmittance than the metal motor housing. An optical deflecting device comprising: a cylindrical sleeve made of. 2. The optical deflector according to claim 1, wherein the bearing is a sliding radial bearing, and the thrust bearing is integrally formed on the bottom of the cylindrical sleeve and supports the rotating body in the thrust axial direction. An optical deflection device characterized by the above.