JP2002039167A - Dynamic pressure bearing, motor, light deflection device, and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dynamic pressure bearing, a motor, and a light deflection device having the dynamic pressure bearing and the motor improved starting characteristic when a rotor side rotates for a fixed bearing side while floating, and an image forming device having the light deflection device. SOLUTION: This dynamic pressure bearing comprises a base member 11, a radial bearing 19, and thrust bearings 21a and 21b fixed to the base member, and a rotor 15 provided rotatably for the radial bearing and the thrust bearings. A maximum diameter d of a contacting surface 27 between the radial bearing and the thrust bearings is an outer diameter D of the radial bearing or less. An elastic member is disposed between the base member and the thrust bearings. The motor and the optical deflection device are structured so that a coil and a fixed yoke are disposed over a magnet of the rotor and an attraction force of the magnet applies in the opposite direction against gravity. The motor and the optical deflection device are also structured so that an intermittent driving signal or an inverse rotation driving signal are inputted in starting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure bearing having improved starting characteristics when a rotating body rotates while floating with respect to a fixed bearing side, a motor having improved starting characteristics, and a dynamic pressure bearing or a motor having the same. The present invention relates to a light deflecting device and an image forming apparatus including the light deflecting device.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus such as a laser beam printer or a digital copying machine, a light deflecting device which performs light beam scanning to write an image on a photosensitive drum is used. Such an optical deflector is provided with a hydrodynamic bearing in which a polygon mirror to which a magnet is fixed is rotatably configured via a bearing, and a motor is provided by providing a coil on a substrate in opposition to the magnet of the hydrodynamic bearing. It has. FIG. 9 shows an example of a motor provided with such a known dynamic pressure bearing.

[0003] The conventional motor shown in FIG.
And a polygon mirror 170 on which a mirror surface 171 is formed.
, A rotating body 150 having a pressing plate 160 of the polygon mirror 170 and a flange 180 for fixing the polygon mirror 170, a bearing 200 provided on an inner peripheral surface 181 of the flange 180, and a magnet 220 fixed to a concave portion of the flange 180. And a dynamic pressure bearing having: In this dynamic pressure bearing, a lower thrust bearing 211 is fixed below the central shaft 110 of the base plate 110, a bearing 190 is fixed through the central shaft 111, and an upper thrust bearing 210 is fixed above the central shaft 111. Are fixed with screws by a fixing plate 250, and the bearing 190 and the upper and lower thrust bearings 210 and 21 are fixed.
1 forms a recess 260 fixed to the central axis 111 of the base plate 110. The motor includes a coil 130 fixed on the printed circuit board 120 of the base plate 110 so as to face the magnet 220. The motor is a coil 13
0 when the bearing 20
0 rotates at high speed while forming an air gap between the rotating body 150 and the recess 260.

However, as described above, the bearing 200 floats together with the rotating body 150 in the recess 260 and rotates in a non-contact manner.
Since it is in contact with the lower thrust bearing 211 and the like on the fixed bearing side within 0, the torque required for starting tends to be large. Then, when the lower thrust bearing 211 is pressed against the base plate 110 via the upper thrust bearing 210 and the bearing 190 and fixed by screwing, the lower thrust bearing 211 is deformed concavely upward in the drawing, and the outer periphery thereof becomes the bearing 200 on the rotation side. As a result, the torque required for starting is further increased, and the starting characteristics are degraded. In addition, if foreign matter such as dust enters between the fixed bearing-side bearings 190 and the upper and lower thrust bearings 210 and 211 and the rotating body-side bearings 200, the torque required for startup increases.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present invention provides a dynamic pressure bearing, a motor, and a motor having improved starting characteristics when the rotating body rotates while floating above the fixed bearing. An object of the present invention is to provide an optical deflecting device including the dynamic pressure bearing or the motor and an image forming apparatus including the optical deflecting device.

[0006]

In order to achieve the above object, a dynamic pressure bearing according to the present invention comprises a base member, a radial bearing and a thrust bearing fixed to the base member, and a radial bearing and a thrust bearing. A rotating body rotatably provided with respect to a bearing, wherein a maximum diameter of a contact surface between the base member and the thrust bearing is equal to or less than an outer diameter of the radial bearing. And

According to this dynamic pressure bearing, when the thrust bearing is fixed to the base member, the contact surface between the base member and the thrust bearing is made smaller than the outer diameter of the radial bearing, so that the deformation of the thrust bearing is reduced. Since the thrust bearing does not press the rotating body side, the starting torque can be reduced and the starting characteristics can be improved.

[0008] In this case, the base member may be provided with a convex portion that comes into contact with the thrust bearing. Further, the thrust bearing may be provided with a convex portion which comes into contact with the base member, and a spacer may be provided between the thrust bearing and the base member. With these configurations, the contact surface between the base member and the thrust bearing can be made smaller than the outer diameter of the radial bearing.

Further, another dynamic pressure bearing according to the present invention is provided with a base member, a radial bearing and a thrust bearing fixed to the base member, and a rotatable bearing with respect to the radial bearing and the thrust bearing. And a rotating body, wherein an elastic member is provided between the base member and the thrust bearing.

According to this dynamic pressure bearing, even if unevenness is present on the surface of the base member or foreign matter such as dust is mixed in, the deformation of the thrust bearing due to the elastic member can be prevented because of the elastic member. Does not press the rotating body side, the starting torque is reduced, and the starting characteristics can be improved.
The elastic member only has to have an elastic modulus smaller than at least the elastic modulus of the material of the base member or the thrust bearing.

In this case, when the maximum diameter of the elastic member is smaller than the outer diameter of the radial bearing, the deformation of the thrust bearing can be further prevented as described above, the starting torque can be reduced, and the starting characteristics can be improved.

Further, the motor according to the present invention includes the above-described dynamic pressure bearing, a magnet disposed on the rotating body, and the magnet opposed to the magnet such that the rotating body rotates relative to the base member. A coil is provided on the base member, and a fixed yoke is provided on the base member adjacent to the coil. According to this motor, the starting torque of the motor is reduced, and the starting characteristics can be improved.

Further, an optical deflecting device according to the present invention includes the above-described dynamic pressure bearing and a polygon mirror which rotates together with the rotating body. According to this light deflecting device, the starting torque of the polygon mirror is reduced, and the starting characteristics can be improved.

Another motor according to the present invention includes a base member fixed to a coil, a fixed yoke provided adjacent to the coil, a radial bearing and a thrust bearing fixed to the base member. A motor comprising: a dynamic pressure bearing having a rotating body that rotates relatively to the base member; and a magnet disposed on the rotating body so as to face the coil, wherein the magnet has an attractive force. Are disposed so as to act in the opposite direction to gravity, and the coil and the fixed yoke are disposed above the magnet.

According to this motor, since the base member and the rotating body are turned upside down and the coil and the fixed yoke are positioned above the rotating body and the magnet, the attractive force of the magnet acts in the direction opposite to the gravity. The load applied to the thrust bearing due to the weight of the rotating body is reduced, the starting torque can be reduced, and the starting characteristics can be improved. Further, by disposing the coil above the motor, the heat radiation of the coil can be improved.

Further, another optical deflecting device according to the present invention comprises a substrate on which a coil, a fixed yoke provided adjacent to the coil are fixed, a base member fixed on the substrate,
A radial bearing and a thrust bearing fixed to the base member, a rotating body having a magnet arranged to face the coil and rotating relative to the base member, and a polygon mirror rotating with the rotating body. Wherein the magnet is arranged so that its attractive force acts in a direction opposite to gravity, and the substrate is arranged such that the coil and the fixed yoke are located above the magnet. It is characterized by having done.

According to this optical deflector, the base member and the rotating body are turned upside down, and the coil and the fixed yoke are positioned above the rotating body and the magnet, so that the attraction force of the magnet acts in the direction opposite to the gravity. Therefore, the load applied to the thrust bearing due to the weight of the rotating body is reduced, the starting torque can be reduced, and the starting characteristics can be improved. In addition, the heat radiation of the coil can be improved by installing the coil above.

Another motor according to the present invention includes a base member fixed to a coil, a fixed yoke provided adjacent to the coil, a radial bearing and a thrust bearing fixed to the base member. A motor comprising: a dynamic pressure bearing having a rotating body that rotates relatively to the base member; and a magnet disposed on the rotating body so as to face the coil. After the intermittent drive signal is input, a steady drive signal is input.

According to this motor, by intermittently applying a drive signal at a frequency of, for example, about 30 to 200 Hz at the time of starting the motor, the motor vibrates, and even when foreign matter enters between the thrust bearing and the rotating body side, No foreign matter is caught, starting torque is reduced, and starting characteristics can be improved.

[0020] Still another motor according to the present invention comprises a base member fixed to a coil, a fixed yoke provided adjacent to the coil, a radial bearing and a thrust bearing fixed to the base member. A motor comprising: a dynamic pressure bearing having a rotating body that rotates relatively to the base member; and a magnet disposed on the rotating body so as to face the coil. When the coil is not activated by input of a drive signal, a high-frequency intermittent drive signal is input to the coil, and then a steady drive signal is input.

According to this motor, when the motor is not started when the motor is started, for example, when the motor is not started due to catching by foreign matter mixed between the thrust bearing and the rotating body, for example, 30 to 2 times.
By intermittently applying the drive signal at a frequency of about 00 Hz, the motor vibrates, no foreign matter is caught, the starting torque is reduced, and the starting characteristics can be improved.

Still another motor according to the present invention comprises a base member fixed to a coil, a fixed yoke provided adjacent to the coil, a radial bearing and a thrust bearing fixed to the base member. A motor comprising: a dynamic pressure bearing having a rotating body that rotates relatively to the base member; and a magnet disposed on the rotating body so as to face the coil. After the rotation drive signal is inputted, a normal rotation drive signal is inputted.

According to this motor, the motor is reversely rotated at the time of starting, so that even if foreign matter is mixed between the thrust bearing and the rotating body side, the foreign matter or the like is not caught, and the starting torque at the time of normal rotation after that. Is reduced, and the starting characteristics can be improved.

Still another motor according to the present invention comprises a base member fixed to a coil, a fixed yoke provided adjacent to the coil, a radial bearing and a thrust bearing fixed to the base member. A motor comprising: a dynamic pressure bearing having a rotating body that rotates relatively to the base member; and a magnet disposed on the rotating body so as to face the coil. When the drive is not started by the input of the drive signal, the drive signal of the normal rotation is input after the drive signal of the reverse rotation is input to the coil.

According to this motor, when the motor is not started due to, for example, a foreign matter mixed between the thrust bearing and the rotating body when the motor is started, the motor is rotated in reverse, so that the foreign matter is not caught. Thereafter, the starting torque for normal rotation is reduced, and the starting characteristics can be improved.

Further, the apparatus may be provided with a detecting means for detecting the rotation of the rotating body, and detecting whether or not the motor is started at the time of starting. Thus, when it is detected that the motor does not start, it is possible to input an intermittent drive signal to the coil or a reverse drive signal as described above.

Further, another light deflecting device according to the present invention includes the above-described motor and a polygon mirror which rotates together with the rotating body. According to this light deflecting device, the starting torque of the polygon mirror is reduced, and the starting characteristics can be improved.

Further, the image forming apparatus according to the present invention is provided with a light deflecting device, and writes image information on a photosensitive member by light reflected by the polygon mirror. According to this image forming apparatus, the starting torque of the polygon mirror can be reduced and the starting characteristics can be improved, so that the start of writing to the photosensitive member can be started in a short time, and the image forming apparatus can be started in a short time. .

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, first to fifth embodiments according to the present invention will be described with reference to the drawings.

<First Embodiment>

FIG. 1 is a side sectional view of an optical deflector showing a first embodiment of the present invention. First light deflecting device 1 of FIG.
0 is a base member 11 made of a metal such as aluminum.
A printed circuit board 12 attached and fixed to the base member 11, a coil 13 formed and fixed on the printed circuit board 12, and a coil 13
Fixed yoke 14 provided on the opposite side to the base member 1
And a rotating body 15 that rotates with respect to the rotating member 1.

The rotating body 15 includes a polygon mirror 17 having a mirror surface 17a, a holding plate 16 for the polygon mirror 17, and a flange 18 for fixing the polygon mirror 17.
And a bearing 20 fixed to the inner peripheral surface 18b of the flange 18 with an adhesive or the like, and the flange 1 so as to face the coil 13.
8 and a magnet 22 fitted and fixed in the concave portion 18a of each of the first and second portions, and the respective portions rotate integrally.

A circular convex portion 11b having an outer diameter d is formed below the central axis 11a of the base member 11.
After the lower thrust bearing 21b is fitted so as to rest on the convex portion 11b, the lower thrust bearing 21b penetrates the center shaft 11a and has an outer diameter D.
A radial bearing 19 (where D ≧ d) is fitted. Further, an upper thrust bearing 21a is fitted above the central shaft 11a, and a fixing plate 25 is screwed thereon with screws 25a. Thus, the upper thrust bearing 21a, the radial bearing 19, and the lower thrust bearing 21b are fixed to the base member 11, and the concave portion 26 is formed by the upper thrust bearing 21a, the lower thrust bearing 21b, and the bearing 19. ing. The upper and lower thrust bearings 21a and 21b and the radial bearing 19 are made of ceramics.

The base member 11 and the upper thrust bearing 21a
, The radial bearing 19, the lower thrust bearing 21 b, and the rotating body 15 constitute a dynamic pressure bearing. The dynamic pressure bearing, the coil 13, and the fixed yoke 14 constitute a motor. A bearing 20 fixed to the flange 18 is located in the concave portion 26 with a gap therebetween.
2, and rotates at a high speed while forming an air gap with the concave portion 26.

According to the light deflecting device 10 as described above, when the lower thrust bearing 21b is fixed on the protrusion 11b of the base member 11, the protrusion 11b and the lower thrust bearing 21b are fixed.
The maximum diameter d of the contact surface 27 is the outer diameter D of the radial bearing 19.
By making it smaller, it is possible to prevent the lower thrust bearing 21b from being concave on the inner periphery and being deformed upward in the figure on the outer periphery 21c. For this reason, since the lower thrust bearing 21 does not particularly press the lower side surface 20a of the bearing 20 with its outer periphery 21c, the starting torque of the motor is reduced, and the starting characteristics can be improved. Thus, a motor and a light deflecting device having a short startup time can be realized.

The lower thrust bearing 21b may be provided with a convex portion which comes into contact with the base member 11, or a spacer may be provided between the lower thrust bearing 21b and the base member 11.

<Second Embodiment>

FIG. 2 is a side sectional view of an optical deflecting device showing a second embodiment of the present invention. Second light deflector 3 of FIG.
0 has almost the same configuration as the optical deflector 10 of FIG. 1 except that an elastic member is provided. Therefore, the same portions are denoted by the same reference numerals and description thereof is omitted.

As shown in FIG. 2, the second light deflecting device 30
In this case, the outer diameter d ′ (however, the outer diameter D of the radial bearing 19) penetrates the center shaft 11 a between the base member 11 (having no projection 11 b as shown in FIG. 1) and the lower thrust bearing 21 b. The circular elastic member 28 of ≧ d ′) is fitted. The elastic member 28 is made of a rubber sheet, but may be another elastic material having an elastic coefficient smaller than that of the base member 11 or the lower thrust bearing 21b, for example, a resin material.

According to the above-described light deflecting device 30, the surface 1 facing the lower thrust bearing 21b of the base member 11 is formed.
Even if unevenness due to machining or the like is present in 1c or foreign matter such as dust is mixed in, the lower thrust bearing 21b can be prevented from being deformed due to the presence of the elastic member 28 between the lower thrust bearing 21b and the lower thrust bearing 21b. Since the lower thrust bearing 21b does not press the lower side surface 20a of the bearing 20, the starting torque can be reduced and the starting characteristics can be improved. This allows
A motor and a light deflecting device with a short startup time can be realized. Further, since the outer diameter d 'of the elastic member 28 is equal to or smaller than the outer diameter D of the radial bearing 19, the deformation of the lower thrust bearing 21 can be further prevented as in the first embodiment, the starting torque is reduced, and the starting is reduced. Characteristics can be improved.

<Third Embodiment>

FIG. 3 is a side sectional view of an optical deflecting device showing a third embodiment of the present invention. Third light deflector 4 of FIG.
0 is different from the optical deflecting device 20 of FIG. 2 except that the coil and the fixed yoke are located above the magnet of the rotating body so that the attracting force of the magnet acts in the direction opposite to the gravity. Since they have almost the same configuration, the same parts are denoted by the same reference numerals and description thereof will be omitted.

As shown in FIG. 3, the third light deflecting device 40
2, the base member 11 and the rotating body 15 are arranged vertically opposite to each other as compared with FIG. 2, and support members 41 and 42 for supporting the base member 11 are arranged at both left and right ends of the base member 11. , 42 are attached and fixed to a member 43 on the device side to which the light deflection device 40 is attached. In FIG. 3, the elastic member of FIG. 2 is omitted, but may be provided, or a convex portion as shown in FIG. 1 may be provided on the base member.

The rotating body 1 has the coil 13 and the fixed yoke 14.
5, the weight of the rotating body and the attractive force of the magnet are applied to the lower thrust bearing 21b, so that the frictional force between the lower surface 20a of the bearing 20 and the lower thrust bearing 21b is increased, and the starting characteristics are reduced. Had a negative impact,
According to the third light deflecting device 40, the base member 11 and the rotating body 15 are turned upside down, and the coil 13 and the fixed yoke 14
Is positioned above the rotating body 15 and the magnet 22, the attractive force of the magnet acts in the direction opposite to the direction of gravity G, so that the load applied to the thrust bearing 21 a due to the weight of the rotating body 15 is reduced, and the frictional force is reduced. As a result, the starting torque can be reduced, and the starting characteristics can be improved. Thus, a motor and a light deflecting device having a short startup time can be realized. In addition, by disposing the coil 13 above the motor, the heat radiation of the coil 13 can be improved.

Next, a modification of the optical deflector 40 of FIG. 3 will be described with reference to FIG. The light deflecting device 50 of FIG. 4 is different from the light deflecting device of FIG.
And the coil 13 on the lower surface 12a.
The fixed yoke 14 is provided on the upper surface 12b so as to face the fifth magnet 22. A spacer member 29 is provided between the lower surface 12a of the substrate 12 and the central axis 11a of the base member 11.
Are arranged so that the distance between the coil 13 and the magnet 22 can be adjusted.

According to the light deflecting device 50 shown in FIG.
By locating the third yoke 14 and the fixed yoke 14 above the rotating body 15 and the magnet 22, the attractive force of the magnet acts in the direction opposite to the direction of gravity G, so that the load on the thrust bearing 21b due to the weight of the rotating body 15 is reduced. However, the frictional force between the lower thrust bearing 21b and the lower surface 20a of the bearing 20 is reduced, so that the starting torque can be reduced and the starting characteristics can be improved. Thus, a motor and a light deflecting device having a short startup time can be realized. In addition, by disposing the coil 13 above the motor, the heat radiation of the coil 13 can be improved. In FIG. 4, the elastic member of FIG. 2 is omitted, but may be provided.
Further, a convex portion as shown in FIG. 1 may be provided on the base member.

<Fourth Embodiment>

FIG. 5 is a side sectional view of a fourth optical deflector showing a fourth embodiment of the present invention, and FIG. 6 shows a coil and a Hall element arranged on a substrate of the optical deflector of FIG. FIG. 7A is a plan view and FIG. 7B is a diagram showing a basic driving circuit for driving the motor. FIGS. 7A and 7B are diagrams showing driving signals applied when the motor is started.

The fourth light deflecting device 50 shown in FIG.
Since the elastic member is omitted from the optical deflector described in the above, the same components as those in FIG. 2 are denoted by the same reference numerals and the description thereof is omitted.

As shown in FIG. 6A, six sets of coils 5
1 to 56 are arranged on the same circle on the substrate 12, and the coils 51 and 52 are diametrically opposed to each other, and the coils 53 and 54 and the coils 55 and 56 are also diametrically opposed to each other. are doing. A permanent magnet 61 is provided opposite to the coils 51 to 56 as shown in FIGS. Also, as shown in FIG.
Hall elements 57 for detecting the permanent magnets 61 passing directly above are provided in the elements 3 and 55, respectively. Information on the rotation speed and position of the rotating body 15 can be obtained based on the detection signals from the three Hall elements 57, and the Hall element 57 has functions as a speed sensor and a position sensor. In FIG. 6B, a motor 66 is constituted by the coils 51 to 56, the Hall element 57, and the permanent magnet 61.

As shown in FIG. 6B, FIG.
The coils 51 and 52, the coils 53 and 54, and the coils 55 and 56 shown in (a) are connected in series, respectively, and the three connected wires are connected to one point, and the other terminal is connected to the A,
B and C are connected respectively. The three Hall elements 57 detect a change in the magnetic field from the N pole and the S pole of the opposed permanent magnet 61 and output an H or L signal. One of the H or L output signals from the three Hall elements 57 is input to a PAM (pulse amplitude modulation) circuit 63 as a speed signal to fluctuate the voltage from a power supply 64 (24 V), and the other is a position signal. A signal is input to the gate driver 65 as a signal, and the control unit of the gate driver 65 switches the switching transistor T
The ON / OFF operation of each of r1, Tr2, Tr3, Tr4, Tr5, and Tr6 is performed.

For example, when Tr3 is turned on and Tr5 is turned on, connection between terminals (AB) is made. That is, power is supplied to the coils 51 and 52 and the coils 53 and 54. Switching of energization 24 times during one rotation of the rotating body 15 (FIG. 5), that is, switching of energization six times during 1/4 rotation. For example, during one rotation (AB), (A-
C), (BC), (BA), (CB),
A series of connections of (CA) such as (C-A)
This is repeated four times by switching the energization to 56. This energization switching is performed by the switching transistor Tr.
It can be performed by a combination of ON / OFF of 1, Tr2, Tr3 and ON / OFF of switching transistors Tr4, Tr5, Tr6 and switching thereof. In this way, the motor 66 rotates at a high speed while the rotation is controlled based on the detection of the magnetic field fluctuation by the Hall element 57.

A start control circuit 67 to which a position signal from the Hall element 57 is input is connected to the PAM circuit 63. As shown in FIG. 7A, when the motor 66 does not rotate and does not start even if a driving current flows through the coil as a driving signal from the power supply 64 and the PAM circuit 63 at the time of startup, the Hall element 57 detects that the motor 66 does not rotate. , Based on the position signal, the activation control circuit 67
, And a drive signal for the coil is output intermittently.

For example, when the motor does not start 10 seconds after the start as shown in FIG.
An intermittent drive signal is input to the coil at the frequency of z. When the motor is started, the motor does not start due to the presence of foreign matter such as dust mixed between the lower thrust bearing 21b and the lower surface 20a of the bearing 20, or the abutment of the lower thrust bearing 21b on the lower surface 20a. At times, by inputting the intermittent drive signal to the coil, the motor vibrates, and there is no catch due to foreign matter or contact, the starting torque is reduced, stable starting can be realized, and the starting characteristics can be improved.
Thus, a highly reliable motor and optical deflection device that are unlikely to cause a start-up failure even when a foreign matter moves can be realized.

The intermittent drive signal is, for example, 30 to 20.
A frequency of about 0 Hz is preferred. After starting in this manner, a normal steady-state current is input to the coil.

The start control circuit 67 shown in FIG.
The fact that the motor 66 does not rotate at startup is
Is detected, the PAM is rotated so that the rotating body 15 rotates in the reverse direction.
The circuit 63 may output a reverse rotation drive signal only for a short period of time, and then input a normal forward normal current to the coil. Accordingly, by slightly rotating the motor in the reverse direction at the time of starting, the catch due to foreign matter or contact is eliminated, the starting torque at the time of normal rotation thereafter is reduced, stable starting can be realized, and the starting characteristics can be improved.

In the above-described example, the intermittent drive signal or the reverse rotation drive signal is input to the coil when it is detected that the motor does not rotate at the time of startup. A drive signal may be input.

The structure of the optical deflector to which the basic driving circuit of this embodiment can be applied is not limited to that shown in FIG. 5, but may be other structures. Of course, it may be a deflection device.

<Fifth Embodiment>

Next, as a fifth embodiment, an example in which the light deflecting device shown in FIGS. 1 to 5 is incorporated in a light scanning optical unit of an image forming apparatus will be described with reference to FIG. FIG. 8 is a perspective view showing a schematic configuration of the optical scanning optical unit.

As shown in FIG. 8, the optical scanning optical unit comprises an optical deflection device 72 fixed on a base 100 and having a polygon mirror 73, a semiconductor laser 76, a collimator lens (beam shaping optical system) 75, 1 cylindrical lens 71, fθ lens 70, 2nd cylindrical lens 80, reflection mirror 90, mirror 8 for timing detection
2 and a synchronization detector 81, respectively. The beam emitted from the semiconductor laser 76 is converted into parallel light by the collimator lens 75, and enters the polygon mirror 73 rotating in the direction of the arrow in the drawing via the first cylindrical lens 71 of the first imaging optical system. The reflected light from the reflection surface 73a of the polygon mirror 73 passes through a second imaging optical system including the fθ lens 70 and the second cylindrical lens 80, and passes through the reflection mirror 90 to the photosensitive drum 91 of the image forming apparatus.
Are scanned in the main scanning direction at a predetermined spot diameter on the peripheral surface of the. The synchronization detection for each line in the main scanning direction is performed by causing the light beam before scanning to be incident on the synchronization detector 81 via the mirror 82, and in synchronization with this, the photosensitive drum 101
Rotates in the sub-scanning direction.

As described above, the image information can be written on the photosensitive drum 101 by the laser beam from the semiconductor laser 76. In this case, the light deflecting device 72
As described above, the start-up characteristics are improved, and the start-up is performed stably in a short time. Therefore, the time until the image information can be written to the photosensitive drum 101 is reduced, and the image forming apparatus can be operated in a short time. You can start with

As described above, the present invention has been described by the embodiments. However, the present invention is not limited to these embodiments.
Various modifications are possible within the scope of the technical idea of the present invention. For example, the dynamic pressure bearing and the motor according to the present invention may be applied to other devices other than the optical deflecting device, and the optical deflecting device may be applied to other devices such as a bar code other than the image forming device. .

[0064]

According to the present invention, a dynamic pressure bearing and a motor having improved starting characteristics when the rotating body side rotates while floating with respect to the fixed bearing side, an optical deflector provided with the dynamic pressure bearing or the motor, and An image forming apparatus including the light deflecting device can be provided.

Further, by reducing the required starting torque, a high-performance motor and a light deflecting device with a short starting time can be realized.
Further, it is possible to realize a highly reliable motor and optical deflecting device in which starting failure is unlikely to occur even when foreign matter or the like is mixed.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a light deflecting device according to a first embodiment of the present invention.

FIG. 2 is a side sectional view of an optical deflecting device according to a second embodiment of the present invention.

FIG. 3 is a side sectional view of an optical deflecting device according to a third embodiment of the present invention.

FIG. 4 is a side sectional view showing a modified example of the light deflecting device according to the third embodiment.

FIG. 5 is a side sectional view of an optical deflecting device according to a fourth embodiment of the present invention.

6A is a plan view showing a coil and a Hall element arranged on a substrate of the optical deflector of FIG. 5, and FIG. 6B is a view showing a basic drive circuit for driving a motor.

FIGS. 7A and 7B are diagrams showing drive signals applied at the time of starting the motor shown in FIGS. 5 and 6. FIGS.

FIG. 8 is a perspective view of an optical scanning optical unit of an image forming apparatus according to a fifth embodiment of the present invention.

FIG. 9 is a side sectional view of a conventional light deflecting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Base member 11a Center axis 11b Convex part 12 Printed circuit board (board) 13 Coil 14 Fixed yoke 15 Rotating body 17 Polygon mirror 17 17a Mirror surface 19 Radial bearing 20 Bearing on rotating body 21a Upper thrust bearing 21b Lower thrust bearing 22 Magnet 27 Contact Surface 28 Elastic member 41, 42 Support member 51-56 Coil 57 Hall element (detection means) 61 Permanent magnet 67 Start control circuit 72 Optical deflector 91 Photoconductor drum d Outside diameter of convex portion 11b D Outside diameter of radial bearing 19 d '' Outer diameter of elastic member 28

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02K 21/24 B41J 3/00 D 5H607 H04N 1/113 H04N 1/04 104A 5H621 (72) Inventor Kurosawa Takashi Akira 2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica Corporation (72) Inventor Naohiro 2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica Corporation F-term (reference) 2C362 BA08 BA10 2H045 AA13 AA24 AA56 3J011 AA01 AA03 BA06 CA02 JA02 KA02 KA03 PA02 RA03 5C072 AA03 BA13 HA02 HA13 HB15 XA01 XA05 5H605 AA03 AA04 BB05 BB10 BB14 BB20 CC01 CC02 CC04 DD09 EA02 EB02 EB05 EB06 EB12 EB18 FF10 GG04 BB01 BB06 BB06 A01 BB06 A01 BB06 GG12 GG15 JJ05 JJ06 5H621 BB07 GA02 GB03 HH01 JK19

Claims (17)

[Claims] 1. A dynamic pressure bearing comprising a base member, a radial bearing and a thrust bearing fixed to the base member, and a rotating body rotatably provided with respect to the radial bearing and the thrust bearing. A dynamic pressure bearing, wherein a maximum diameter of a contact surface between the base member and the thrust bearing is equal to or less than an outer diameter of the radial bearing. 2. The dynamic pressure bearing according to claim 1, wherein the base member is provided with a convex portion that comes into contact with the thrust bearing. 3. The thrust bearing according to claim 1, wherein a convex portion is provided in contact with the base member.
The dynamic pressure bearing according to the above. 4. The dynamic pressure bearing according to claim 1, wherein a spacer is provided between the thrust bearing and the base member. 5. A dynamic pressure bearing comprising a base member, a radial bearing and a thrust bearing fixed to the base member, and a rotating body rotatably provided with respect to the radial bearing and the thrust bearing. A dynamic pressure bearing, wherein an elastic member is provided between the base member and the thrust bearing. 6. The dynamic pressure bearing according to claim 5, wherein a maximum diameter of the elastic member is equal to or less than an outer diameter of the radial bearing. 7. The dynamic pressure bearing according to claim 1, a magnet disposed on the rotating body, and the magnet such that the rotating body rotates relative to the base member. And a fixed yoke disposed on the base member adjacent to the coil and opposed to the coil. 8. An optical deflecting device comprising: the dynamic pressure bearing according to claim 1; and a polygon mirror that rotates together with the rotating body. 9. A base member for fixing a coil, a fixed yoke provided adjacent to the coil, a radial bearing and a thrust bearing fixed to the base member, and rotating relative to the base member. And a magnet disposed on the rotating body so as to face the coil, wherein the magnet has an attractive force acting in a direction opposite to gravity. Wherein the coil and the fixed yoke are disposed above the magnet. 10. A substrate to which a coil, a fixed yoke provided adjacent to the coil is fixed, a base member fixed to the substrate, a radial bearing and a thrust bearing fixed to the base member. A light deflecting device comprising: a rotator having a magnet arranged to face the coil and rotating relative to the base member; and a polygon mirror rotating with the rotator, wherein the magnet is An optical deflecting device, wherein the substrate is arranged so that an attractive force acts in a direction opposite to gravity, and the coil and the fixed yoke are positioned above the magnet. 11. A base member for fixing a coil, a fixed yoke provided adjacent to the coil, a radial bearing and a thrust bearing fixed to the base member, and rotating relative to the base member. And a magnet disposed on the rotating body so as to face the coil, wherein a high-frequency intermittent drive signal is input to the coil at startup. And a motor for receiving a steady drive signal. 12. A base member for fixing a coil, a fixed yoke provided adjacent to the coil, a radial bearing and a thrust bearing fixed to the base member, and rotating relative to the base member. And a magnet disposed on the rotating body so as to face the coil, wherein the motor is not started by input of a steady drive signal to the coil at startup. In this case, after a high-frequency intermittent drive signal is input to the coil, a steady drive signal is input. 13. A base member for fixing a coil, a fixed yoke provided adjacent to the coil, a radial bearing and a thrust bearing fixed to the base member, and rotating relative to the base member. And a magnet disposed on the rotating body so as to face the coil, wherein a driving signal for reverse rotation is input to the coil at startup. And a motor for inputting a drive signal for normal rotation. 14. A base member fixing a coil, a fixed yoke provided adjacent to the coil, a radial bearing and a thrust bearing fixed to the base member, and rotating relative to the base member. And a magnet disposed on the rotating body so as to face the coil, wherein the motor is activated by inputting a normal rotation drive signal to the coil at startup. If the motor is not driven, a reverse rotation drive signal is input to the coil, and then a normal rotation drive signal is input. 15. The motor according to claim 12, further comprising detection means for detecting rotation of the rotating body, and detecting whether or not the motor is started at the time of starting. 16. The method according to claim 7, 9, 11, 12, 13, 1.
16. An optical deflecting device comprising: the motor according to 4 or 15; and a polygon mirror that rotates together with the rotating body. 17. An image forming apparatus comprising the light deflecting device according to claim 8, 10 or 16, wherein image information is written on a photosensitive member by light reflected by the polygon mirror.