JP2002106567A - Hydrodynamic air bearing type optical deflector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrodynamic air bearing type optical deflector which keeps stable rotary condition without lowering of bearing performance even when thermal deviation occurs on the whole bearing, or by suppressing thermal deviation over all the bearing. SOLUTION: In the hydrodynamic air bearing type optical deflector, a gap between a fixed shaft and a rotary shaft of a pump mechanism located near a fixed shaft which is exposed to the outside of a case, is designed wider than a gap between a fixed shaft and a rotary shaft of a radial hydrodynamic air bearing. Besides an axial flow generation mechanism for generating axial flow is provided on or near the radial hydrodynamic air bearing in order to cool the air supplied to the axial flow generation mechanism through an exhaust hole which is used to exhaust the air in the case to the outside with a pump mechanism.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure air bearing type optical deflector mounted on information equipment, imaging equipment, measuring equipment, etc., and more particularly, it has a pump mechanism capable of substantially evacuating the inside of a case, The present invention relates to a high-performance dynamic pressure air bearing type optical deflector capable of reducing power consumption and noise.

[0002]

2. Description of the Related Art The applicant of the present invention can discharge air inside a case sealed by a case and a cover member to the outside of the case by rotating a rotor portion, and can decompress or evacuate the inside of the case. Japanese Patent Application Laid-Open No. 09-061742 discloses a dynamic pressure air bearing type optical deflector provided with a pump mechanism.
No., JP-A-10-206780, Japanese Patent No. 264576
No. 8, Patent No. 2645773, Japanese Patent Application No. 11-1595
No. 39 and others. A dynamic pressure air bearing type optical deflector provided with this pump mechanism will be described with reference to FIGS.

FIG. 15 is a longitudinal sectional view showing an example of a dynamic pressure air bearing type optical deflector provided with a pump mechanism, and FIG.
FIG. 5 is a half sectional view showing a peripheral portion of a pump mechanism of a dynamic pressure air bearing type optical deflector 5.

[0004] Reference numeral 11h denotes a base on which a fixed shaft 21h is erected substantially at the center, and a housing 13h to which a stator coil 63 is fixed.
h. A rotating shaft 23h rotatably supported by a radial dynamic pressure air bearing 31h is engaged with the outer periphery of the fixed shaft 21h, and the rotating polygon mirror 61, the rotor yoke 65, and the like are attached to the rotating shaft 23h, so that the rotor is rotated. Unit is configured. This rotor part is combined with a case 15h composed of a base 11h and a housing 13h, and a cover member 17h provided with a laser beam transmitting window (not shown).
By being accommodated in a case sealed by the above, the rotating polygon mirror 6
1 will rotate at high speed.

Here, in a dynamic pressure air bearing type optical deflector provided with a pump mechanism, as shown in FIG. 16, when the rotor rotates, a dynamic pressure is generated in the radial dynamic pressure air bearing 31h. And the radial dynamic pressure air bearing 3
As shown by arrows in the figure, air in the case (mirror chamber 19h) is substantially at the center of the fixed shaft 21h by upper and lower pump mechanisms 41h and 43h formed by herringbone grooves engraved at both ends of 1h. The air is sucked from the air communication passages 49j and 49k formed toward the portion, discharged to the outside of the case through a filter 53h and an air communication passage 49i formed substantially in the center of the fixed shaft 21h, and is discharged with time. The pressure inside the case can be reduced to a substantially vacuum state.

[0006] By reducing or evacuating the pressure in the case (mirror chamber 19h) as described above, the air resistance when the rotor rotates can be greatly reduced, and the loss of the motor can be suppressed. In addition to the above, wind noise generated when the rotary polygon mirror 61 rotates at high speed can be largely suppressed.

FIGS. 17 to 23 show another example of the structure of a dynamic pressure air bearing type optical deflector provided with a pump mechanism. The dynamic pressure air bearing type optical deflector shown in FIGS. By forming separate herringbone grooves for suction at both ends of the dynamic pressure air bearing 31i, the bearing rigidity of the radial dynamic pressure air bearing 31i can be increased. The bearing type optical deflector can suppress the axial dimension by providing the thrust bearings 33j and 33i with a pump function. FIG. 21 shows that the pump mechanism 43g is provided only at one end of the radial dynamic pressure air bearing 31g to similarly reduce the axial dimension. FIG. 23 shows that the hollow sleeve is fixed to the fixed shaft. Although this is 21e, basically the same effect as the dynamic pressure air bearing type optical deflector shown in FIGS. 13 and 14 can be obtained. In addition,
FIGS. 22A to 22C show other examples of the configuration of the radial dynamic pressure air bearing, but not limited to the herringbone groove, and various types of dynamic pressure air bearings can be applied. .

As described above, in the dynamic pressure air bearing type optical deflector provided with the pump mechanism, the pressure in the case sealed by the case and the cover member is reduced to a considerably lower pressure than the atmospheric pressure at the operating rotational speed. Alternatively, since the air can be evacuated, windage loss and wind noise caused by a rotary polygon mirror or the like can be significantly reduced, and power consumption can be suppressed.

[0009]

However, when air is present in the case, heat generated by fluid friction in the radial dynamic pressure air bearing or the like is transferred to the case or the cover member via a fixed shaft or the like. Besides being transmitted (convection) to the case and the cover member using the air in the case as a medium,
The temperature around the bearing part is almost uniform, but when the inside of the case is decompressed or evacuated, convection in the case hardly occurs, and especially in a dynamic pressure air bearing type optical deflector equipped with a pump mechanism. Therefore, in order to discharge the air in the case to the outside, at least a part of the fixed shaft is provided with a discharge hole, and the vicinity thereof is exposed to the outside of the case or comes into contact with the outside air, Heat is easily dissipated compared to other parts. As a result, the temperature around the bearing portion including the pump mechanism varies, and this temperature difference appears as a difference in the amount of thermal expansion. There is a problem that the gap between the shaft and the fixed shaft is not uniform throughout the bearing portion, and the clearance cannot be secured, so that the bearing performance is reduced, and in the worst case, the rotating shaft is seized.

According to the present invention, even when a temperature difference occurs throughout the bearing portion, a stable rotation state can be obtained by preventing the performance of the bearing from deteriorating, or by making the temperature difference less likely to occur throughout the bearing portion. It is intended to obtain a dynamic pressure air bearing type optical deflector.

The objects and novel features of the invention will become more fully apparent when the following description is read in conjunction with the accompanying drawings. However, the drawings are for explanation only, and do not limit the technical scope of the present invention.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a radial fixed shaft having a hollow fixed shaft erected in a case and a herringbone groove or other dynamic pressure generating portion formed on the inner periphery of the fixed shaft. A rotating shaft rotatably supported by a dynamic pressure air bearing, and a rotating polygon mirror and other rotor portions that rotate integrally with the rotating shaft are housed in a case sealed with a case and a cover member, and the rotor A dynamic pressure air bearing type optical deflector equipped with a pump mechanism for discharging air in the case to the outside of the case by rotating the portion and reducing or evacuating the inside of the case; The gap between the fixed shaft and the rotating shaft of the pump mechanism provided in the vicinity of the radial dynamic pressure air bearing is set to be wider than the gap between the fixed shaft and the rotating shaft of the radial dynamic pressure air bearing. Constitute a receiving mold optical deflector.

Further, a fixed shaft erected on the case and a rotary shaft rotatably supported on the outer periphery or inner periphery of the fixed shaft by a radial dynamic pressure air bearing comprising a herringbone groove and other dynamic pressure generating portions. A rotating polygon mirror that rotates integrally with the rotating shaft is housed in a case sealed by a case and a cover member, and the air in the case is moved to the outside of the case by rotating the rotor portion. In the dynamic pressure air bearing type optical deflector provided with a pump mechanism for reducing or evacuating the inside of the case, an axial flow generating mechanism for generating an axial flow in the radial dynamic pressure air bearing or in the vicinity thereof is provided. The dynamic pressure air bearing type light is cooled by cooling air supplied to the axial flow generating mechanism through a discharge hole for discharging air in the case to the outside of the case by a pump mechanism. Constitute a direction device.

A fixed shaft erected on the case; and a rotating shaft rotatably supported on the inner periphery of the fixed shaft by a radial dynamic pressure air bearing comprising a herringbone groove and other dynamic pressure generating parts. The rotating polygon mirror and other rotor unit that rotates integrally with the rotating shaft are housed in a case sealed by a case and a cover member, and the air in the case is discharged to the outside of the case by rotating the rotor unit. A dynamic pressure air bearing type optical deflector having a pump mechanism for decompressing or evacuating the inside of the case, wherein an axial flow generating mechanism for generating an axial flow is provided at or near the radial dynamic pressure air bearing; Alternatively, an air communication passage formed substantially in the center of the rotating shaft and communicating with the outside of the case, or discharging the air in the case to the outside of the case by the pump mechanism. And supplying air outside the case to an end on the suction side of the axial flow generating mechanism through the air passage, and an air communication passage formed at a discharge hole of the pump mechanism or at a substantially central portion of the fixed shaft or the rotating shaft. By discharging air from the end of the axial flow generating mechanism on the discharge side to the outside of the case through the above, a dynamic pressure air bearing type optical deflector is formed.

Further, a rotating shaft rotatably supported by a radial fixed pressure air bearing comprising a hollow fixed shaft erected in a case and an outer or inner periphery of the fixed shaft and a herringbone groove or other dynamic pressure generating portion. And a rotating polygon mirror that rotates integrally with the rotating shaft and another rotor unit are housed in a case sealed by a case and a cover member, and the air in the case is rotated by rotating the rotor unit. In a dynamic pressure air bearing type optical deflector provided with a pump mechanism for discharging to the outside and decompressing or evacuating the inside of the case, the exposed portion of the fixed shaft to the outside of the case is insulated to the extent that the function of the pump mechanism is not hindered. A dynamic pressure air bearing type optical deflector is constituted by covering with a member.

In addition, a rotation is rotatably supported on a hollow fixed shaft erected in the case and a radial dynamic pressure air bearing formed of a herringbone groove or other dynamic pressure generating portion on the outer or inner periphery of the fixed shaft. Shaft, and a rotating polygon mirror that rotates integrally with the rotating shaft is housed in a case sealed with a case and a cover member, and the air in the case is rotated by rotating the rotor. In a dynamic pressure air bearing type optical deflector having a pump mechanism for discharging to the outside of the case and decompressing or evacuating the inside of the case, a fixed shaft of a pump mechanism provided near the fixed shaft exposed to the outside of the case. A dynamic pressure air bearing type optical deflector by optimizing the linear expansion coefficient of the fixed shaft or the rotating shaft so that the gap with the rotating shaft is substantially constant before and after driving the motor.

A hollow fixed shaft erected on the case;
A rotary shaft rotatably supported on the outer circumference or inner circumference of the fixed shaft by a radial dynamic pressure air bearing comprising a herringbone groove or another dynamic pressure generating portion, and a rotating polygon mirror rotating integrally with the rotary shaft. A pump that accommodates the other rotor portion in a case hermetically sealed by a case and a cover member, and discharges air in the case to the outside of the case by rotating the rotor portion, thereby reducing or evacuating the inside of the case. In a dynamic pressure air bearing type optical deflector provided with a mechanism, a gap between a fixed shaft and a rotating shaft of a pump mechanism provided near the fixed shaft exposed to the outside of the case is substantially constant before and after driving of the motor. By optimizing the shape near the exposed portion of the fixed shaft, a dynamic pressure air bearing type optical deflector is configured.

[0018]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a longitudinal sectional view of a dynamic pressure air bearing type optical deflector according to a first embodiment of the present invention, and FIG. 2 shows a main part of the dynamic pressure air bearing type optical deflector of FIG. FIG. 3 is an enlarged half sectional view.

Reference numeral 15a denotes a case in which a hollow fixed shaft 21a is erected substantially at the center, and the stator coil 6
3 is fixed. On the inner periphery of the hollow fixed shaft 21a,
A shaft of a rotary shaft 23a rotatably supported by a radial dynamic pressure air bearing 31a is engaged with the fixed shaft 2 by a hub formed integrally with the shaft.
A rotor portion is formed by covering the opening end above 1a and attaching a rotating polygon mirror 61, a rotor yoke 65, and the like to the outer periphery of the hub. This rotor portion is accommodated in a case sealed by a case 15a and a cover member 17a formed with a laser light transmission window (not shown) in a state where the rotor portion is supported in the thrust direction by a thrust bearing 33a, and substantially. Thus, the inside of the mirror chamber 19a closed at a high speed is rotated at a high speed.

Here, the pump mechanism for depressurizing or substantially evacuating the inside of the case (mirror chamber 19a) will be described in detail with reference to FIG. 1. The outer periphery of the shaft of the rotating shaft 23a and the inner periphery of the fixed shaft 21a are defined by predetermined values. The rotor portion is rotatably supported by a radial dynamic pressure air bearing 31a provided substantially at the center of the rotor portion. At both ends of the radial dynamic pressure air bearing 31a, pump mechanisms 41a and 43a provided with a herringbone groove or the like are provided. As the rotor rotates, the air in the mirror chamber 19a is sucked through a gap and a communication passage 51a formed in the flange of the fixed shaft 21a and communicating the lower end of the fixed shaft 21a with the inside of the case. . The sucked air in the mirror chamber 19a is supplied to the air communication passages 49a, 49b, 49c formed inside the shaft of the rotating shaft 23a, the lower pump mechanism 43a and the radial dynamic pressure air bearing, as shown by arrows in the drawing. The filter chamber 53 is discharged to the outside of the case via a discharge port 45a formed in a flange portion of the fixed shaft 21a and a filter 53a, which communicates the vicinity of the boundary with the outside of the mirror chamber 31a.
The inside of 9a can be decompressed or substantially evacuated. On the other hand, both ends of the radial dynamic pressure air bearing 31a communicate with the outside of the case via atmosphere communication passages 49a, 49b, 49c, a discharge port 45a, and the like. Regardless of the pressure inside 19a, stable bearing rigidity can always be obtained.

However, the problem here is that since the inside of the mirror chamber 19a is substantially evacuated, heat generated by the radial dynamic pressure air bearing can hardly be expected to be dissipated by convection. The heat is radiated to the outside of the case by heat conduction of the rotation shaft 21a and the rotation shaft 23a.

This will be described in detail with reference to FIG.
Since the flange portion of the fixed shaft 21e is exposed to the outside, heat radiation is good, and a temperature difference occurs between the vicinity of the exposed portion and other portions, resulting in a difference in the amount of thermal expansion. That is, the thermal expansion caused by the fluid friction of the radial dynamic pressure air bearing 31a causes the rotation shaft 23a and the fixed shaft 2
1e will be deformed as shown by broken lines, respectively.
The initial gap CL1 where the rotating shaft 23a and the fixed shaft 21e face each other changes like CL2 and CL3. When the temperature of the rotating shaft 23a and the temperature of the fixed shaft 21e are almost the same, the gap becomes almost the same as in CL1 and CL2. However, when the temperature difference occurs between them, the gap is made as in CL3. Is narrower than CL1 and a predetermined clearance cannot be secured, so that the bearing performance is degraded or, in the worst case, seizure of the rotating shaft is caused.

On the other hand, in the dynamic pressure air bearing type optical deflector according to the first embodiment of the present invention, as shown in FIG. 2, near the flange portion of the fixed shaft 21a exposed to the outside. The fixed shaft 21a and the rotating shaft 23 of the provided pump mechanism 43a
a is set to be larger than the gap between the fixed shaft 21a and the rotating shaft 23a of the radial dynamic pressure air bearing 31a by G, so that even when a temperature difference occurs throughout the bearing portion, It is possible to obtain a stable rotation state without lowering the bearing performance or causing seizure of the rotating shaft.

Incidentally, the temperature around the radial dynamic pressure air bearing rises by about 55 ° C. (about 80 ° C. when the room temperature is 25 ° C.), and the temperature difference between the rotating shaft and the fixed shaft reaches about 20 ° C. It has been confirmed by experiments that when a temperature difference of 20 ° C. occurs when both the rotating shaft and the fixed shaft are made of aluminum, the linear expansion coefficient of aluminum becomes 23 to 29E-6 / ° C.
(Here, “E-6” means 10 to the sixth power, that is, 0.000023 to 0.000029 / ° C .; the same applies hereinafter.)
In this case, G is set to 3 μm
Is set to However, since these data are considered to vary depending on the specifications and operating environment of the motor, it is desirable to set the value of G according to the specifications. Further, the maximum value of G may be set to such an extent that the pump function can be obtained when the gap between the fixed shaft and the rotary shaft of the pump mechanism becomes minimum due to the temperature difference.

Next, another embodiment of the present invention will be described with reference to FIGS. In addition, the first of the present invention
The same components as those of the dynamic air bearing type optical deflector according to the embodiment are denoted by the same reference numerals, and description thereof is omitted.

FIG. 3 is an enlarged half sectional view of a main part of a dynamic pressure air bearing type optical deflector according to a second embodiment of the present invention.

The main difference between the dynamic air bearing type optical deflector of the second embodiment of the present invention and the dynamic air bearing optical deflector of the first embodiment of the present invention is that the lower pump is used. The gap between the fixed shaft and the rotating shaft of the mechanism is not uniformly set to be wider than the gap between the fixed shaft and the rotating shaft of the radial dynamic air bearing by G, but as shown in FIG. Is set broadly with a gradient in the range of 0 to G in accordance with the variation of.

As described above, by setting a gradient in the range of 0 to G, an optimum clearance can be obtained after the gap between the rotating shaft and the fixed shaft changes due to thermal expansion. Since it can be configured, more stable bearing performance and pump function can be obtained.

FIGS. 4 and 5 are longitudinal sectional views of a dynamic pressure air bearing type optical deflector according to the third and fourth embodiments of the present invention.

The dynamic air bearing type optical deflection of the third and fourth embodiments of the present invention is mainly different from the dynamic air bearing optical deflection of the first and second embodiments of the present invention. Does not set the gap between the fixed shaft and the rotating shaft of the lower pump mechanism wider than the gap between the fixed shaft and the rotating shaft of the radial dynamic pressure air bearing, but generates an axial flow in the radial dynamic pressure air bearing. The axial flow generating mechanism is provided in the vicinity of the radial dynamic pressure air bearing or integrally with the radial dynamic pressure air bearing, and the air supplied to the axial flow generating mechanism is cooled through a discharge port for discharging the air to the outside of the case. It is in.

FIG. 4 shows the axial flow generating mechanism 67a provided near the lower end of the radial dynamic pressure air bearing 31b.
Has an axial flow generating mechanism 67b provided integrally with the radial dynamic pressure air bearing 31c.
The air supplied to the fixed shafts 7a and 67b is cooled through a discharge port 45a formed in a flange portion of the fixed shaft 21e, and the cooled air is supplied to the radial dynamic pressure air bearings 31b and 31.
c, the radial dynamic pressure air bearings 31b, 31c
Since the temperature distribution can be made uniform throughout, the same effects as those of the dynamic pressure air bearing type optical deflector of the first and second embodiments of the present invention can be obtained, and the radial dynamic pressure air can be obtained. Since the heat generation of the bearings 31b and 31c can be suppressed, the maximum rotation speed can be increased by about 10%.

FIGS. 6 and 7 are longitudinal sectional views of a dynamic pressure air bearing type optical deflector according to the fifth and sixth embodiments of the present invention.

The dynamic air bearing type optical deflection of the fifth and sixth embodiments of the present invention is mainly different from the dynamic air bearing optical deflection of the third and fourth embodiments of the present invention. Has an inlet for supplying air outside the case to the axial flow generating mechanism, and an outlet for discharging the outside of the case through the radial dynamic pressure air bearing,
They are provided separately.

FIG. 6 shows a radial dynamic pressure in which a cylindrical end having an air communication passage 49a penetrating the inside is provided on the rotating shaft 23d and an axial flow generating mechanism is integrally provided instead of providing a lower pump mechanism. Due to the suction action of the air bearing 31c, as shown by the arrow in the drawing, the outside of the case is passed through a filter 53b of a suction port 47a provided at a substantially central portion of a bottom plate 57b provided at a lower end surface of the fixed shaft 21c. From the air, the atmosphere communication passage 49a, the radial dynamic pressure air bearing 3
1c, is discharged to the outside of the case via the discharge port 45a and the filter 53a.

FIG. 7 shows a boundary between the suction port 47b and the discharge port 45b on the flange portion of the fixed shaft 21d, the upper pump mechanism 41a and the upper end face of the radial dynamic pressure air bearing 31c, while keeping the lower pump mechanism 43c and the like. Has an opening in the vicinity,
A second communication passage 51c communicating with the discharge port 45b is provided, and the radial dynamic pressure air bearing 31c integrally provided with the axial flow generating mechanism is provided with a filter as shown by an arrow in FIG. Air is sucked in from the outside of the case via the suction port 53c and the suction port 47b, and is discharged to the outside of the case via the radial dynamic pressure air bearing 31c, the second communication path 51c, the discharge port 45b, and the filter 53c.

As described above, the air supplied to the radial dynamic pressure air bearing is sucked from the outside of the case through the suction port, and the heated air after cooling the radial dynamic pressure air bearing is:
Since the cooling efficiency of the radial dynamic pressure air bearing and the like can be improved by discharging the fluid to the outside of the case through the discharge port, the dynamic pressure air bearing type optical deflection device according to the third and fourth embodiments of the present invention can be improved. The same effect as the vessel can be obtained,
Further improvement in rotation speed can be expected.

FIGS. 8 and 9 are a longitudinal sectional view and a main part enlarged view of a dynamic pressure air bearing type optical deflector according to the seventh and eighth embodiments of the present invention.

The dynamic air bearing type optical deflection of the seventh and eighth embodiments of the present invention is mainly different from the dynamic air bearing type optical deflection of the first to sixth embodiments of the present invention. Is that the exposed portion of the fixed shaft to the outside of the case is covered with a heat insulating member within a range that does not hinder the function of the pump mechanism.

FIG. 8 is a view in which the flange portion of the fixed shaft 21e, which is exposed to the outside of the case, is covered with a heat insulating member such as styrene foam, and the pump mechanism 41a, 43d removes air inside the mirror chamber 19a. Discharge port 45a for discharging
The opening of the pump mechanism 41 is not completely closed.
The functions a and 43d are not impaired.

FIG. 9 shows a case in which the lower part of the case 15a is covered with a heat insulating member together with the flange portion of the fixed shaft 21e. Similarly to FIG. 8, the opening of the discharge port 45a is provided so as not to hinder the functions of the pump mechanisms 41a and 43d. The department is not completely closed.

As described above, by covering the exposed portion of the fixed shaft to the outside of the case with the heat insulating member as long as the function of the pump mechanism is not obstructed, the temperature of the entire bearing portion such as the pump mechanism and the radial dynamic pressure air bearing can be increased. Since it can be configured so as not to cause a difference, a predetermined clearance can be obtained from the time of startup to the time of steady rotation, and the same as the dynamic air bearing type optical deflector of the first embodiment of the present invention. The effect of can be obtained.

FIGS. 10 and 11 show the ninth and first embodiments of the present invention.
It is a longitudinal section of a dynamic pressure air bearing type optical deflector of a 0th embodiment.

The dynamic pressure air bearing type optical deflection of the ninth and tenth embodiments of the present invention is mainly different from the dynamic pressure air bearing type optical deflection of the first to eighth embodiments of the present invention. Optimizes the linear expansion coefficient of the fixed shaft or rotating shaft so that the gap between the fixed shaft and the rotating shaft of the pump mechanism provided near the fixed shaft exposed outside the case is almost constant before and after the motor is driven. It has become.

The coefficient of linear expansion of aluminum is 23 to 29E-6 /
When the temperature difference between the fixed shaft and the rotating shaft at this time is 20 ° C., the linear expansion coefficient of the rotating shaft having a different thermal expansion amount due to the temperature difference is set in the range of 15-18E-6 / ° C. Then
The amounts of thermal expansion of the fixed shaft and the rotating shaft become substantially equal. Therefore, using an alloy material such as an Al—Cu—Zn alloy (aluminum bronze), a Cu—Ni alloy (Constantan), and an Fe—Cr—Ni alloy (stainless steel) having such a linear expansion coefficient, FIG. As shown in FIG. 11 to FIG. 11, by forming the alloy portions 73a and 73b integrally with the rotating shaft, the gap between the fixed shaft and the rotating shaft of the pump mechanism can be made substantially constant before and after driving the motor. Therefore, stable bearing performance can be obtained from the start to the steady rotation.

On the contrary, the linear expansion coefficient of the fixed shaft having a different thermal expansion amount due to the temperature difference is set to 36 to 44E-6 / ° C.
The same effect can be obtained by setting in the range.

FIG. 12 is a longitudinal sectional view of a dynamic pressure air bearing type optical deflector according to an eleventh embodiment of the present invention.

The main difference between the dynamic air bearing type light deflection of the eleventh embodiment of the present invention and the dynamic air bearing light deflection of the first to tenth embodiments of the present invention is that The shape of the fixed shaft near the exposed part has been optimized so that the gap between the fixed shaft and the rotary shaft of the pump mechanism provided near the fixed shaft exposed to the outside is almost constant before and after driving the motor. is there.

A notch 69a is formed in the vicinity of the exposed portion of the fixed shaft 21f, where the lower pump mechanism 43d is formed, so as to leave only the pump mechanism 43d. Due to the formation of the notch portion 69a, the outer periphery of the flange portion, which is the exposed portion of the fixed shaft 21f, and the inner periphery of the flange portion where the pump mechanism 43d and the like are provided are connected via a slight connection portion 71 to conduct heat. Is performed,
Depending on the cross-sectional area of the connection portion, the heat conduction characteristics deteriorate, and the heat conduction of the temperature deteriorates between the inner periphery of the flange portion and the outer periphery of the flange portion. For this reason, the temperature around the lower pump mechanism 43d is almost the same as the temperature of the radial dynamic pressure air bearing 31a, and no temperature difference is generated throughout the pump mechanism and the entire bearing portion of the radial dynamic pressure air bearing. Stable bearing performance can be obtained over the time of rotation.

In the meantime, as shown in FIG.
The description has been given of the shaft rotating type dynamic pressure air bearing type optical deflector. However, as shown in FIG. 14, the sleeve rotating type dynamic pressure air bearing type optical deflector also rotates with the fixed shaft due to the temperature difference. A change occurs in the gap with the axis. In the case of the rotary shaft type, the gap is narrowed as shown by CL3 in FIG. 13, and in the worst case, there is a risk that the rotating shaft may be seized. When the gap is widened as indicated by CL6, there is a danger that the bearing performance will decrease.

However, the axial flow generating mechanism generates an axial flow in the radial dynamic pressure air bearing to suppress the temperature rise of the radial dynamic pressure air bearing, and cover the exposed portion of the fixed shaft to the outside of the case with a heat insulating member. The shape near the exposed part of the fixed shaft, so that the temperature difference does not occur throughout the bearing part such as the pump mechanism and the radial dynamic pressure air bearing, and the linear expansion coefficient of the fixed shaft or rotating shaft is optimized The gap between the fixed shaft and the rotating shaft of the pump mechanism is
It is clear that the configuration that becomes substantially constant before and after the motor is driven is also applicable to a sleeve rotating type dynamic pressure air bearing type optical deflector. Detailed description of the optical deflector has been omitted.

Further, the gap between the fixed shaft and the rotary shaft of the pump mechanism provided near the flange portion of the fixed shaft exposed to the outside is G more than the gap between the fixed shaft and the rotary shaft of the radial dynamic pressure air bearing. An axial flow generation mechanism that is set to be wider or that generates an axial flow in the radial dynamic pressure air bearing is provided near or integrally with the radial dynamic pressure air bearing. Supply air,
It has been described individually, such as cooling through a discharge port that discharges to the outside of the case and covering the exposed portion of the fixed shaft to the outside of the case with a heat insulating member as long as it does not interfere with the function of the pump mechanism. It is needless to say that may be adopted in combination as appropriate.

[0053]

As described in detail above, the present invention has the following effects.

(1) A hollow fixed shaft erected on the case,
A rotating shaft rotatably supported on the inner periphery of the fixed shaft by a radial dynamic pressure air bearing comprising a herringbone groove or other dynamic pressure generating portion, and a rotating polygon mirror or the like which rotates integrally with the rotating shaft. A pump mechanism for accommodating the rotor portion in a case sealed by a case and a cover member, and discharging the air in the case to the outside of the case by rotating the rotor portion to reduce the pressure or evacuate the inside of the case. In the dynamic pressure air bearing type optical deflector provided, the gap between the fixed shaft and the rotating shaft of the pump mechanism provided near the fixed shaft exposed to the outside of the case is fixed to the fixed shaft and the rotating shaft of the radial dynamic pressure air bearing. The dynamic pressure air bearing type optical deflector is configured by setting the gap wider than the gap, so that even if a temperature difference occurs throughout the bearing part, the bearing performance is low. Without causing or rotary shaft seizure etc., it is possible to obtain a stable rotation state. Also,
The gap between the fixed shaft and the rotating shaft of the lower pump mechanism is not uniformly set wider than the gap between the fixed shaft and the rotating shaft of the radial dynamic air bearing, but corresponds to the change in the gap due to thermal expansion By setting the slope with a gradient, the optimal clearance can be obtained after the gap between the fixed shaft and the rotating shaft changes due to thermal expansion, so that more stable bearing performance and pump function Can be obtained.

(2) A fixed shaft erected on the case, and a rotating shaft rotatably supported on the outer or inner periphery of the fixed shaft by a radial dynamic pressure air bearing comprising a herringbone groove and other dynamic pressure generating portions. A rotating polygon mirror that rotates integrally with the rotating shaft and other rotor parts are housed in a case sealed by a case and a cover member, and by rotating the rotor part, air in the case is removed from the case. In a dynamic pressure air bearing type optical deflector equipped with a pump mechanism for reducing or evacuating the inside of the case, an axial flow generating mechanism for generating an axial flow in the radial dynamic pressure air bearing or in the vicinity thereof is provided. The pump mechanism cools the air supplied to the axial flow generating mechanism through a discharge hole for discharging the air in the case to the outside of the case, thereby providing a dynamic pressure air bearing type light. Since it constitutes a countercurrent apparatus, since it as the temperature difference throughout the bearing portion does not occur,
Since the same effect as (1) can be obtained and the heat generation of the radial dynamic pressure air bearing can be suppressed,
The maximum rotation speed can be increased by about 10%.

(3) A fixed shaft erected on the case and a rotating shaft rotatably supported on the inner periphery of the fixed shaft by a radial dynamic pressure air bearing comprising a herringbone groove and other dynamic pressure generating portions. The rotating polygon mirror that rotates integrally with the rotating shaft is housed in a case sealed by a case and a cover member and other rotor parts, and by rotating the rotor part, air in the case is moved to the outside of the case. In a dynamic pressure air bearing type optical deflector provided with a pump mechanism for discharging and decompressing or evacuating the inside of the case, an axial flow generating mechanism for generating an axial flow in or near the radial dynamic pressure air bearing is provided, and An air communication passage formed at a shaft or a substantially central portion of the rotating shaft and communicating with the outside of the case, or discharging the air in the case to the outside of the case by the pump mechanism. And supplying air outside the case to an end on the suction side of the axial flow generating mechanism through the air passage, and an air communication passage formed at a discharge hole of the pump mechanism or at a substantially central portion of the fixed shaft or the rotating shaft. The hydrodynamic air bearing type optical deflector is constructed by discharging air from the end of the axial flow generating mechanism on the discharge side to the outside of the case via the shaft, so that the cooling efficiency throughout the entire bearing portion is improved. Therefore, the same effect as (2) can be obtained, and further improvement in rotation speed can be expected.

(4) A hollow fixed shaft erected on the case,
A rotary shaft rotatably supported on the outer circumference or inner circumference of the fixed shaft by a radial dynamic pressure air bearing comprising a herringbone groove or another dynamic pressure generating portion, and a rotating polygon mirror rotating integrally with the rotary shaft. A pump that accommodates the other rotor portion in a case hermetically sealed by a case and a cover member, and discharges air in the case to the outside of the case by rotating the rotor portion, thereby reducing or evacuating the inside of the case. In a dynamic pressure air bearing type optical deflector provided with a mechanism, a dynamic pressure air bearing type optical deflector is configured by covering an exposed portion of the fixed shaft to the outside of the case with a heat insulating member as long as the function of the pump mechanism is not hindered. As a result, it is possible to prevent a temperature difference from occurring throughout the bearing portion, so that a predetermined clearance can be obtained from the start to the steady rotation. , Without causing seizure or the like and a decrease in the rotational axis of the bearing performance, it is possible to obtain a stable rotation state.

(5) A hollow fixed shaft erected on the case,
A rotary shaft rotatably supported on the outer circumference or inner circumference of the fixed shaft by a radial dynamic pressure air bearing comprising a herringbone groove or another dynamic pressure generating portion, and a rotating polygon mirror rotating integrally with the rotary shaft. A pump that accommodates the other rotor portion in a case hermetically sealed by a case and a cover member, and discharges air in the case to the outside of the case by rotating the rotor portion, thereby reducing or evacuating the inside of the case. In a dynamic pressure air bearing type optical deflector provided with a mechanism, a gap between a fixed shaft and a rotating shaft of a pump mechanism provided near the fixed shaft exposed to the outside of the case is substantially constant before and after driving of the motor. Since the dynamic pressure air bearing type optical deflector is configured by optimizing the linear expansion coefficient of the fixed shaft or the rotating shaft, the same effect as (4) can be obtained. .

(6) A hollow fixed shaft erected on the case,
A rotary shaft rotatably supported on the outer circumference or inner circumference of the fixed shaft by a radial dynamic pressure air bearing comprising a herringbone groove or another dynamic pressure generating portion, and a rotating polygon mirror rotating integrally with the rotary shaft. A pump that accommodates the other rotor portion in a case hermetically sealed by a case and a cover member, and discharges air in the case to the outside of the case by rotating the rotor portion, thereby reducing or evacuating the inside of the case. In a dynamic pressure air bearing type optical deflector provided with a mechanism, a gap between a fixed shaft and a rotating shaft of a pump mechanism provided near the fixed shaft exposed to the outside of the case is substantially constant before and after driving of the motor. Since the dynamic pressure air bearing type optical deflector is configured by optimizing the shape near the exposed portion of the fixed shaft, the same effect as (4) can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a dynamic pressure air bearing type optical deflector according to a first embodiment of the present invention.

FIG. 2 is an enlarged half sectional view of an essential part of the dynamic pressure air bearing type optical deflector of FIG. 1;

FIG. 3 is an enlarged half sectional view of a main part of a dynamic pressure air bearing type optical deflector according to a second embodiment of the present invention.

FIG. 4 is a longitudinal sectional view of a dynamic pressure air bearing type optical deflector according to a third embodiment of the present invention.

FIG. 5 is a longitudinal sectional view of a dynamic pressure air bearing type optical deflector according to a fourth embodiment of the present invention.

FIG. 6 is a longitudinal sectional view of a dynamic pressure air bearing type optical deflector according to a fifth embodiment of the present invention.

FIG. 7 is a longitudinal sectional view of a dynamic pressure air bearing type optical deflector according to a sixth embodiment of the present invention.

FIG. 8 is a longitudinal sectional view of a dynamic pressure air bearing type optical deflector according to a seventh embodiment of the present invention.

FIG. 9 is an enlarged sectional view of a main part of a dynamic pressure air bearing type optical deflector according to an eighth embodiment of the present invention.

FIG. 10 is a longitudinal sectional view of a dynamic pressure air bearing type optical deflector according to a ninth embodiment of the present invention.

FIG. 11 is a longitudinal sectional view of a dynamic pressure air bearing type optical deflector according to a tenth embodiment of the present invention.

FIG. 12 is a vertical sectional view of a dynamic pressure air bearing type optical deflector according to an eleventh embodiment of the present invention.

FIG. 13 is a half-sectional view of an essential part of an enlarged part A of FIG. 23;

FIG. 14 is an enlarged partial cross-sectional view of a main part of part B of FIG. 21;

FIG. 15 is a longitudinal sectional view showing an example of a conventional dynamic pressure air bearing type optical deflector.

FIG. 16 is a half sectional view showing a periphery of a pump mechanism of the dynamic pressure air bearing type optical deflector of FIG. 15;

FIG. 17 is a longitudinal sectional view showing another configuration example of a conventional dynamic pressure air bearing type optical deflector.

FIG. 18 is a half sectional view showing the periphery of a pump mechanism of the dynamic pressure air bearing type optical deflector of FIG. 17;

FIG. 19 is a longitudinal sectional view showing another configuration example of a conventional dynamic pressure air bearing type optical deflector.

FIG. 20 is a plan view showing the periphery of a pump mechanism of the dynamic pressure air bearing type optical deflector of FIG. 19;

FIG. 21 is a longitudinal sectional view showing another configuration example of a conventional dynamic pressure air bearing type optical deflector.

FIG. 22 is a cross-sectional view showing another configuration example of the radial dynamic pressure air bearing.

FIG. 23 is a longitudinal sectional view showing another configuration example of a conventional dynamic pressure air bearing type optical deflector.

[Explanation of symbols]

15a, 15g, 15h, 15i: Case, 17a, 17h, 17i: Cover member, 19a, 19b, 19h, 19i: Mirror room, 21a to 21j, 21m, 21n, 21p: Fixed shaft, 23a to 23e, 23g to 23i , 23m, 23n, 2
3p to 23r: rotating shaft, 31a, 31b, 31c, 31g, 31h, 31i: radial dynamic pressure air bearing, 33a, 33h, 33i, 33j: thrust bearing, 41a, 41h, 41i, 43a to 43d, 43g to 4
3j: pump mechanism, 45a, 45b, 45i, 45j: outlet, 47a, 47b: inlet, 49a to 49c, 49f to 49k, 49m, 49n, 4
9p: atmosphere communication path, 51a, 51b, 51c: communication path, 53a, 53b, 53c, 53g, 53h: filter, 55a, 55b: sealing member, 57a, 57b: bottom plate, 59a, 59b: heat insulating member, 61 : Rotating polygon mirror, 63: stator coil, 65: rotor yoke, 67a, 67b: axial flow generating mechanism, 69a: notch, 71: connecting part, 73a, 73b: alloy part.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takeshi Miura 110-1 Shinkushita Nitta, Iruma-shi, Saitama F-term (reference) in Nidec Copal Electronics Co., Ltd. 2H045 AA14 AA23 AA24 3J011 AA04 BA04 CA03 KA02 KA03 MA23

Claims (6)

[Claims] 1. A hollow fixed shaft erected in a case, and a rotary shaft rotatably supported on the inner periphery of the fixed shaft by a radial dynamic pressure air bearing comprising a herringbone groove and other dynamic pressure generating portions. A rotating polygon mirror that rotates integrally with the rotating shaft is housed in a case sealed by a case and a cover member, and the air in the case is moved to the outside of the case by rotating the rotor portion. And a dynamic pressure air bearing type optical deflector provided with a pump mechanism for reducing or evacuating the inside of the case, wherein a fixed shaft and a rotating shaft of the pump mechanism provided near the fixed shaft exposed outside the case. Wherein the gap is set wider than the gap between the fixed shaft and the rotating shaft of the radial dynamic pressure air bearing. 2. A fixed shaft erected in a case and a rotary shaft rotatably supported on the outer periphery or inner periphery of the fixed shaft by a radial dynamic pressure air bearing comprising a herringbone groove and other dynamic pressure generating portions. A rotating polygon mirror that rotates integrally with the rotating shaft is housed in a case sealed by a case and a cover member, and the air in the case is moved to the outside of the case by rotating the rotor portion. And a dynamic pressure air bearing type optical deflector provided with a pump mechanism for reducing or evacuating the inside of the case, wherein the radial dynamic pressure air bearing or an axial flow generating mechanism for generating an axial flow in the vicinity thereof is provided, A dynamic pressure air bearing type light, wherein air supplied to the axial flow generating mechanism is cooled through a discharge hole for discharging air in the case to the outside of the case by a pump mechanism. Deflector. 3. A fixed shaft erected in a case, and a rotating shaft rotatably supported on an inner periphery of the fixed shaft by a radial dynamic pressure air bearing comprising a herringbone groove and other dynamic pressure generating portions, The rotating polygon mirror and other rotor unit that rotates integrally with the rotating shaft are housed in a case sealed by a case and a cover member, and the air in the case is discharged to the outside of the case by rotating the rotor unit. And
In a dynamic pressure air bearing type optical deflector provided with a pump mechanism for reducing or evacuating the inside of the case, an axial flow generating mechanism for generating an axial flow in the radial dynamic pressure air bearing or in the vicinity thereof is provided, and the fixed shaft or the fixed shaft is provided. A suction-side end of the axial flow generating mechanism through an air communication passage formed at a substantially central portion of the rotating shaft and communicating with the outside of the case or a discharge hole for discharging air in the case to the outside of the case by the pump mechanism; To the outside of the case, and at the discharge side end of the axial flow generating mechanism through a discharge hole of the pump mechanism or the air communication passage formed at a substantially central portion of the fixed shaft or the rotating shaft. A dynamic pressure air bearing type optical deflector characterized by discharging air out of the case to the outside of the case. 4. A rotary shaft rotatably supported by a radial fixed-pressure air bearing comprising a hollow fixed shaft erected in a case, and an outer or inner periphery of the fixed shaft having a herringbone groove or another dynamic pressure generating portion. And a rotating polygon mirror that rotates integrally with the rotating shaft and another rotor unit are housed in a case sealed by a case and a cover member, and the air in the case is rotated by rotating the rotor unit. In a dynamic pressure air bearing type optical deflector having a pump mechanism for discharging to the outside and reducing or evacuating the inside of the case, the exposed portion of the fixed shaft to the outside of the case is insulated to the extent that the function of the pump mechanism is not hindered. A dynamic pressure air bearing type optical deflector characterized by being covered by a member. 5. A rotary shaft rotatably supported by a radial fixed-pressure air bearing comprising a hollow fixed shaft erected in a case, and an outer or inner periphery of the fixed shaft having a herringbone groove or other dynamic pressure generating portion. And a rotating polygon mirror that rotates integrally with the rotating shaft and another rotor unit are housed in a case sealed by a case and a cover member, and the air in the case is rotated by rotating the rotor unit. In a dynamic pressure air bearing type optical deflector having a pump mechanism for discharging to the outside and decompressing or evacuating the inside of the case, a fixed shaft of a pump mechanism provided near the fixed shaft exposed to the outside of the case rotates. A dynamic pressure air bearing type optical deflector characterized by optimizing a linear expansion coefficient of a fixed shaft or a rotating shaft so that a gap between the shaft and the motor is substantially constant before and after driving. 6. A rotary shaft rotatably supported by a radial fixed-pressure air bearing comprising a hollow fixed shaft erected in a case and an outer or inner periphery of the fixed shaft having a herringbone groove or another dynamic pressure generating portion. And a rotating polygon mirror that rotates integrally with the rotating shaft and another rotor unit are housed in a case sealed by a case and a cover member, and the air in the case is rotated by rotating the rotor unit. In a dynamic pressure air bearing type optical deflector having a pump mechanism for discharging to the outside and decompressing or evacuating the inside of the case, a fixed shaft of a pump mechanism provided near the fixed shaft exposed to the outside of the case rotates. A dynamic pressure air bearing type optical deflector characterized in that the shape near the exposed portion of the fixed shaft is optimized so that the gap with the shaft is substantially constant before and after driving of the motor.