JP3448146B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a laser beam printer or a digital copying machine for driving a motor using a dynamic pressure bearing to rotate a polygon mirror and performing scanning according to image information.

[0002]

2. Description of the Related Art Conventionally, in a digital copying machine which is an image forming apparatus, for example, a polygonal mirror having an accurate polygonal shape is rotationally driven at a constant speed in a constant direction by a polygon motor, and a polygonal mirror in the semiconductor laser unit is installed therein. A laser beam emitted from a semiconductor laser is converted into a parallel light beam by a collimator lens and is shaped into a constant light beam by passing through an aperture provided in the semiconductor laser unit, and the light beam is sub-scanning direction by a cylindrical lens. A laser beam scanning device is provided so that the compressed one is made incident.

The rotation speed of the polygon mirror of the laser beam scanning device is determined by the rotation speed of the photosensitive drum, the writing density of the laser beam scanning device, and the number of faces of the polygon mirror. Further, in such a laser beam scanning device, the demand for high-speed rotation of the polygon mirror has been increasing due to the recent increase in processing speed, high density, and high image quality of the image forming apparatus.

Conventionally, a polygon motor in such a laser beam scanning device has used a ball bearing as a bearing for supporting its rotating shaft, but this ball bearing has a limit to the need for high speed operation. For,
In order to cope with such speeding up, a dynamic pressure bearing has come to be used as a bearing of a polygon motor (see, for example, JP-A-60-26432).

This dynamic pressure bearing is a bearing for supporting the shaft or the shaft by the rotation of the rotor portion (both cases may be used).
A groove called “groove” is provided to generate a dynamic pressure in the gap between the shaft and the bearing, and the generated pressure supports the rotating portion in a non-contact state. Therefore, generally, the bearing rigidity increases as the rotation speed of the rotor portion increases.

Further, as a medium for generating a dynamic pressure, a dynamic pressure bearing utilizing air or a dynamic pressure bearing utilizing a liquid such as a magnetic fluid has been developed and is actually used. Therefore, an example of a polygon motor that uses an air dynamic pressure bearing,
It shows in FIG. In the figure, 61 is a motor housing,
62 is a fixed shaft in which a groove called a groove is formed,
Reference numeral 63 denotes a printed circuit board provided with a coil, which is a portion that serves as a motor stator.

Further, 64 is a bearing fitted to the fixed shaft 62 with a clearance of several microns, 65 is a polygon mirror fixed to the bearing 64 by a retainer 66 and screws 67, 68
Is a rotor magnet, which is a portion that serves as a rotor.
Further, this polygon motor is provided with a cover 69 for the purpose of dustproofing and soundproofing, and a transparent glass 70 is provided at the beam passage portion of the cover 69. The thrust directions of the fixed shaft 62 and the bearing 64 are not in contact with each other due to the repulsive force of the magnets 71 and 72.

[0008]

Generally, in the case of an image forming apparatus such as a digital copying machine equipped with the above laser beam scanning device, a motor control circuit for controlling the driving of the polygon motor when the main switch is turned off. The voltage application to the polygon motor is stopped, which causes the polygon motor to stop. At that time, the rotor of the polygon motor continues to rotate as it is due to inertia, but when a dynamic pressure bearing is used as the bearing, dynamic pressure is generated in the gap between the shaft and the bearing, and the rotor part is not in contact. Since it is rotating, its rotation speed gradually decreases, but it continues to rotate for a long time.

That is, in the case of a polygon motor using such a dynamic pressure bearing, due to its characteristics, the state in which the rotor is fluffy for a long time at low rotation and low bearing rigidity continues for a long time. . In such a state, if a large vibration or shock is applied to the motor from the outside, the shaft and the bearing of the motor should be in contact with each other due to the vibration or shock, even if they are originally rotating without contact. Become.
As a result, the shaft or bearing is damaged or worn, resulting in a significant decrease in performance or a shortened life. Further, in the worst case, the shaft and the bearing may be engaged with each other, and in such a case, the bearing may be locked, and there is a fear that the device cannot be used thereafter.

Therefore, in the case of a polygon motor using such a dynamic pressure bearing, a large vibration or shock is applied to the device especially after the main switch of the device is turned off until the polygon motor is stopped. It was necessary to prevent it from moving or moving the device. For this reason, in the past, it has been called attention by describing this point in a manual or the like as a precaution for use. However, the time from turning off the main switch to stopping the polygon motor is very long due to the characteristics of the dynamic pressure bearing, so during that time something may give a large vibration or impact to the device, There was a risk of damaging the motor.

The present invention has been made in view of the above problems, and the shaft and bearing of the motor for rotating the polygon mirror after the main switch of the device is turned off are prevented from being damaged, and the motor The purpose is to prevent performance deterioration and shortening of life.

[0012]

In order to achieve the above object, the present invention provides an image forming apparatus having a laser beam scanning device as described above, which is provided on the display unit for a predetermined time after the main power is turned off. It is provided with a means for displaying a caution so as not to apply vibration or shock to the main body.

Further, it is preferable that the predetermined time is equal to or longer than a predicted time from when the main power source is turned off to when the motor for rotating the polygon mirror is stopped. Further, in any one of the above image forming apparatuses, the motor can rotate at a plurality of rotation speeds, and the predetermined time is changed according to the rotation speed of the motor set when the main power supply is turned off. Means may be provided.

Further, the motor rotation detecting means for detecting the rotation of the motor and the motor rotation detecting means after the main power supply is turned off until the rotation of the motor is no longer detected.
The image forming apparatus may be configured by providing a display unit with means for displaying a caution so as not to apply vibration or impact to the apparatus body.

Further, in the image forming apparatus, the motor rotation detecting means may be a means for detecting the rotation of the motor by the back electromotive force of the motor, or the motor may be operated by the output of a hall element provided in the motor. It is advisable to provide a means for detecting the rotation of the.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a control system of an image forming apparatus and its related configuration for explaining an embodiment of the present invention, and FIG. 2 is a schematic configuration showing an overall configuration of a digital copying machine which is also the image forming apparatus. It is a figure.
The digital copying machine, which is the image forming apparatus shown in FIG. 2, includes an automatic document feeder 11, an image reading apparatus 12 provided in the apparatus body 10, and a printer unit 13 having a laser beam scanning apparatus 27.

The automatic document feeder 11 sets the number of originals set on a predetermined original table (not shown).
The sheets are fed one by one and set on the contact glass 14, and when the scanning of the original is completed, the original is set on the contact glass 14.
Discharge from above. As shown in FIG. 3, the image reading device 12 includes a first carriage A including an illumination lamp 15 serving as a light source, a reflecting mirror 16, and a first mirror 17, and a second mirror 1.
8 and a second carriage B having a third mirror 19.

When the image of the original is read, the first carriage A moves forward at a constant speed, and the second carriage B moves forward following the first carriage A at half the speed of the first carriage A. By doing so, the document on the contact glass 14 is optically scanned. Then, the reflected light image of the document on the contact glass 14 illuminated by the illumination lamp 15 and the reflecting mirror 16 is reflected by the first mirror 17, the second mirror 18,
An image is formed on the CCD sensor 22 by the lens 21 via the third mirror 19 and the color filter 20 shown in FIG.

The CCD sensor 22 photoelectrically converts the reflected light image of the formed original to output an analog image signal,
The image of the original is read. Then, after the reading of the image is completed, the first carriage A and the second carriage B return to their home positions (return). Note that CC
3 lines of C equipped with red (R), green (G), and blue (B) filters as D sensors
If a CD is used, a color original can be read.

The analog image signal from the CCD sensor 22 is converted into a digital image signal by an analog / digital converter, and various image processings (binarization, multi-value conversion, gradation processing, conversion, etc.) are performed by the image processing plate 23. Double processing, editing processing, etc.) is performed. The printer unit 13 is provided with a photoconductor drum 25 which is an image carrier, and the photoconductor drum 25 is rotationally driven in the direction of arrow A by the drive unit during the copying operation, and the surface thereof is uniformly charged by the charging device 26. After being charged, the laser beam scanning device 27 performs image exposure with the digital image signal subjected to the above-described image processing, and an electrostatic latent image is formed. And the electrostatic latent image
It is developed by the developing device 28.

On the other hand, the transfer paper is fed from the paper feed stage selected from the paper feed devices 33 to 35 toward the registration roller 36, and the transfer paper is timinged by the registration roller 36 with the image on the photosensitive drum 25. The image (visual image) on the photoconductor drum 25 is transferred thereto by the transfer device 30. The transfer sheet is separated from the photosensitive drum 25 by the separating device 31, is conveyed to the fixing device 38 by the conveying device 37, the image is fixed there, and is then discharged onto the tray 39. Then, the photosensitive drum 2
The surface of 5 is cleaned by the cleaning device 32 after the transfer paper is separated to remove the residual toner.

In the laser beam scanning device 27, as shown in FIG. 4, the laser beam emitted from the semiconductor laser in the semiconductor laser unit 40 is used as the semiconductor laser unit 40.
It is converted into a parallel light beam by a collimating lens inside and is shaped into a constant light beam by passing through an aperture provided in the semiconductor laser unit 40. This light beam is compressed in the sub-scanning direction by the cylindrical lens 41 and enters the polygon mirror 42.

The polygon mirror 42 has an accurate polygonal shape as shown in the drawing, and is driven to rotate in a certain direction at a constant speed by the polygon motor 4 (not shown in FIG. 4, so see FIG. 2). . And this polygon mirror 42
The rotational speed of the photosensitive drum 25, the writing density of the laser beam scanning device 27, and the polygon mirror 42
It is determined by the number of faces. The laser beam that has entered the polygon mirror 42 from the cylindrical lens 41 is deflected by the reflecting surface of the polygon mirror 42 and enters the fθ lens 44 that constitutes an optical system.

The fθ lens 44 is the polygon mirror 4
The scanning light having a constant angular velocity from 2 is converted so as to be scanned at a constant velocity by the photosensitive drum 25, and the laser beam from the fθ lens 44 is also transmitted through the reflecting mirror 45 and the dustproof glass 46 which also constitute an optical system. An image is formed on the photosensitive drum 25. The fθ lens 44 also has a surface tilt correction function. The laser beam that has passed through the fθ lens 44 is
It is reflected by the synchronization detection mirror 47 outside the image area and guided to the synchronization detection sensor 48. Then, the detection output of the synchronization detection sensor 48 provides a synchronization signal that serves as a reference for cueing in the main scanning direction.

As shown in FIG. 1, this digital copying machine includes a power supply control device 1 having a timer circuit 7 and a power supply control circuit 8, a laser scanning device control circuit 2, and a polygon motor control circuit 3 having a brake circuit 6. , And a display unit control circuit 9 for controlling the display of the display unit 24. The laser scanning device control circuit 2 is supplied with power from the power supply control device 1, and the polygon motor control circuit 3 is supplied to the polygon motor 4
Clock signal (CL
K) and an ON / OFF signal for controlling the start / stop of the motor.

The polygon motor control circuit 3 receives power supply from the power supply control device 1, and receives the laser scanning device control circuit 2.
The above-mentioned clock signal and ON / OFF signal are input to control the rotation of the polygon motor 4. The brake circuit 6 of the polygon motor control circuit 3 functions to brake the polygon motor 4 while the power (voltage) is being supplied after the main switch 5 is turned off. Also,
When the main power supply is turned off by the main switch 5, the power supply control device 1 displays on the display unit control circuit 9 a display for calling attention to the display unit 24 so as not to apply vibration or shock to the device body 10 (for example, A signal for displaying a message or lighting a warning light) is output for a predetermined time after the main power supply is turned off.

By the way, in the conventional digital copying machine, when the main switch is turned off in a normal case, the power supply to all circuits is cut off. Therefore, in the case of a polygon motor using a dynamic pressure bearing in the bearing portion, after the main switch is turned off, it continues to rotate due to inertia for a long time.

When a large vibration or shock is applied to the device from the outside while the polygon motor is rotating due to inertia, the rotating polygon motor is in non-contact with the shaft supporting the shaft. Because of the strong contact of each other from the state, they may be scratched or worn, resulting in a significant loss of performance or a shortened life. Further, in the worst case, the shaft and the bearing may engage with each other (gnawing) to cause the bearing to lock, and in such a case, the device cannot be used thereafter. .

However, in this digital copying machine,
When the main switch 5 is turned off, the timer circuit 7 provided in the power supply control device 1 operates and continues to supply power to the display control circuit 9 for a predetermined time. As a result, a warning display indicating that the polygon motor 4 is rotating even after the main switch 5 is turned off is displayed on the display unit 24, and vibration or impact is not applied to the apparatus main body while the display is displayed. To be warned. Therefore, the operator looks at the warning display and takes care not to apply vibration or shock to the apparatus body 10 while the warning is displayed. Thereby, even in the polygon motor 4 using the dynamic pressure bearing as described above, it is possible to prevent the shaft and the bearing supporting the shaft from strongly contacting each other from the non-contact state. It is possible to prevent them from being damaged or worn out and significantly impairing the performance.

Next, the operation of each part after the main switch 5 is turned off will be described with reference to the flowchart of FIG. The power supply control device 1 shown in FIG. 1 includes a central processing unit (CPU) having various determination and processing functions, a ROM that stores each processing program and fixed data, and a RAM that is a data memory that stores the processing data. A microcomputer including an input / output circuit (I / O) is provided.

When the flow chart of FIG. 5 starts, the microcomputer first determines in step 1 whether the main switch (main SW) 5 is off, and if it is off, proceeds to step 2 to laser The scanning device control circuit 2 causes the polygon motor control circuit 3 to output a motor stop signal (OFF signal) for stopping the polygon motor 4.

In the next step 3, the timer setting time (predetermined time) t0 is set in the timer circuit 7 in the power supply control device 1 and the timer is started. Then, in step 4, it is judged whether or not the set time t0 that has been set has passed, and if it has not yet passed (NO determination), step 5
The display proceeds to (5) to supply power (voltage) to the display control circuit 6, and the polygon motor 4 is rotating due to inertia. Hereinafter, a warning display will be displayed on the display unit 24.

Then, again in step 4, it is judged whether or not the set time t0 has elapsed, and if it has elapsed, step 6
Then, by stopping the supply of power to the display control circuit 6 (stopping the voltage application), the warning display displayed on the display 24 is erased, and the processing of this routine ends. In addition,
In the case where the polygon motor 4 is rotating in the normal use state, if a display indicating that the motor is rotating is displayed on the display unit 24,
Even after the main switch 5 is turned off, the display is continued for the set time t0. When the display of the motor rotation is not displayed in the normal use state, the main switch 5 is turned off and the above warning display is displayed on the display unit 24.

FIG. 6 shows the main switch (main SW) 5
FIG. 6 is a timing chart showing a period from when the switch is turned off to when the polygon motor 4 is stopped. When the main switch 5 is turned off, the timer circuit 7 operates, and power is continuously supplied to the display control circuit 9 (application of the voltage Vv) until the aforementioned set time t0 elapses.

Therefore, until the set time t0 elapses, a warning display is displayed on the display section 24 to call attention so as not to apply vibration or shock to the apparatus body 10. Further, during the set time t0, power is supplied to the polygon motor control circuit 3 and a motor stop signal (OFF signal) is output from the laser scanning device control circuit 2 to the polygon motor control circuit 3. , The brake circuit 6 is applied to the polygon motor 4 only during the set time t0.
Works.

Therefore, when the time (predicted time) from the constant speed rotation state of the polygon motor 4 to the stop of being applied with the braking by the action of the brake circuit 6 is ts, t0 ≥
By setting t0 to be ts, the above warning display can be displayed on the display unit 24 until the polygon motor 4 is surely stopped. Also, the set time t
By setting 0 to a value close to the time ts, it is possible to prevent power from being supplied to the display control circuit 9 for an unnecessarily long time after the main switch 5 is turned off.

FIG. 7 is a block diagram similar to FIG. 1 for explaining another embodiment of the image forming apparatus according to the present invention.
FIG. 8 is a flow chart showing a part of a routine relating to a warning display process performed by the microcomputer of the power supply control device 1'of the image forming apparatus. Parts corresponding to those in FIG. is there. In the image forming apparatus according to this embodiment, the polygon motor control circuit 3'is
The polygon motor 4 can be rotated at a plurality of rotation speeds, and the power supply control device 1'will set the above-mentioned set time t0 according to the rotation speed of the polygon motor 4 set when the main switch 5 is turned off. (See FIG. 6).

That is, the polygon motor 4 may be rotated at a plurality of rotation speeds depending on the process linear velocity of the apparatus, the writing density, and the like. Therefore, the time (predicted time) until the polygon motor 4 is stopped by applying the brake by the brake circuit 6 from the rotation state at each rotation speed is ts.
1, ts2, ts3, and set times t1, t2, t3 (main switch 5 is turned off) for supplying power (voltage) to the display control circuit 9 and the polygon motor control circuit 3'corresponding to these times. It is advisable to set the relationship with the time after being set to t1 ≥ts1, t2 ≥ts2 and t3 ≥ts3.

Then, depending on the number of revolutions of the polygon motor 4 at the time when the main switch 5 is turned off, any one of the set times t1, t2 and t3 is set, which is necessary. Power is supplied to the display control circuit 9 and the polygon motor control circuit 3 for a minimum period of time.

FIG. 8 shows a routine for changing the set time according to the rotation speed of the polygon motor 4. This routine is performed in step 3 of the flowchart shown in FIG. In FIG. 8, CLK is a clock for determining and controlling the rotation speed of the polygon motor 4, and in this example, the polygon motor 4 is drive-controlled by three kinds of rotation speeds. That is, when the main switch 5 is turned off while the polygon motor 4 is rotating at the first rotation speed (CLK1), the time t1 is set to the set time t0 of the timer of the timer circuit 7 in the power supply control device 1 '. Is set by t1 ≧ ts1.

When the rotation speed of the polygon motor 4 is not the first rotation speed (CLK1), it is judged whether or not it is the second rotation speed (CLK2). Time t2 is set to the set time t0 of the timer, t2
Set with ≧ ts2. Further, if the number of revolutions of the polygon motor 4 is neither the first number of revolutions nor the second number of revolutions, it is the third number of revolutions (CLK3), so the time t3 is set to the timer set time t0 of the timer circuit 7. , T3 ≧ ts3. In this embodiment, as shown in FIG.
A clock (C that determines and controls the rotation speed of the polygon motor 4)
LK) information is sent from the laser scanning device control circuit 2 to the timer circuit 7, and the clock information is used to set the timer set time t0.

Also in this embodiment, the laser scanning device control circuit 2 is supplied with power from the power supply control circuit 8, and the laser scanning device control circuit 2 supplies the polygon motor 4 to the polygon motor control circuit 3 '. It outputs a clock (CLK) signal for controlling by the number of revolutions of and a ON / OFF signal for controlling start / stop. And
The polygon motor control circuit 3'is supplied with power from the power supply control circuit 8 and is supplied with the above-mentioned clock (CLK) signal and ON.
/ OFF signal is input from the laser scanning device control circuit 2,
The rotation of the polygon motor 4 is controlled.

FIG. 9 is a block diagram similar to FIG. 1 for explaining still another embodiment of the image forming apparatus according to the present invention, and FIG. 10 is a microcomputer included in the power supply controller 1 ″ of the image forming apparatus. 5 is a flowchart showing a routine relating to a warning display process performed by the power supply control device 1 ″ of the image forming apparatus according to the present embodiment, which has motor rotation detection means for detecting rotation of the polygon motor 4 and has a main switch. When 5 is turned off, the polygon motor control circuit 3 outputs an off signal for stopping the polygon motor 4 to the laser scanning device control circuit 2, and the motor rotation detecting means stops detecting the rotation of the polygon motor 4. For continuing to supply power to the display control circuit 9 to warn the device body 10 not to apply vibration or impact To be displayed on the display unit 24 display tell.

By supplying power (voltage) to the polygon motor control circuit 3 until the polygon motor 4 stops rotating, the brake circuit 6 is activated to brake the polygon motor 4. That is,
When the polygon motor 4 is rotating, a motor rotation detection signal is output from the polygon motor 4 to the power supply control device 1 ″, and when the main switch 5 is turned off, the motor rotation detection signal is output. Power is supplied from the power supply control device 1 ″ to the polygon motor control circuit 3, the laser scanning device control circuit 2 and the display unit control circuit 9 only until the detection of “1” is stopped. Therefore, until the stop of the polygon motor 4 is detected, power is continuously supplied from the power supply control circuit 8 of the power supply control device 1 ″ to the display control circuit 9, and during that time, a warning is displayed on the display 24. Be done.

Next, regarding the warning display processing performed by the microcomputer provided in the power supply control device 1 ″,
This will be described with reference to the flowchart of FIG. It is determined whether or not the main switch (main SW) 5 is off. If it is off, the laser scanning device control circuit 2 causes the polygon motor control circuit 3 to move to the polygon motor 4
A motor stop signal (OFF signal) for stopping the motor is output. Therefore, the polygon motor 4 is stopped by applying the brake by the brake circuit 6.

In the next step, it is judged from the motor rotation detection signal whether the polygon motor 4 is still rotating,
If it continues to rotate (determination of YES), power is continuously supplied from the power supply control device 1 ″ to the display control circuit 9, and vibration or impact is applied to the device body 10 while the polygon motor 4 is still rotating. A warning display is displayed on the display unit 24 so as to call attention so as not to output the warning (output of the warning display).

When the polygon motor 4 is rotating in a normal use state and a display for indicating the rotation is displayed on the display section 24,
The display is continued. Then, when the stop of the polygon motor 4 is detected by not detecting the motor rotation detection signal, the power supply to the display unit control circuit 9 by the power supply control device 1 ″ is stopped, and the processing of this routine ends.

As the motor rotation detection signal,
For example, the output of the Hall element that controls the rotation of the polygon motor 4 or the counter electromotive force generated by the rotation of the polygon motor 4 can be used. According to this embodiment, power can be supplied to the display control circuit 9 after the main switch 5 is turned off for a minimum required time while the polygon motor 4 is rotating, so that the most efficient operation is possible. A warning can be displayed.

[0049]

As described above, according to the present invention, the polygon mirror can be rotated at a high speed by increasing the image forming processing speed, increasing the image density, and improving the image quality. Even if a high-speed dynamic bearing that supports the rotating part in a non-contact state is used for the motor that rotates the motor, when the main power is turned off, the display unit will not display A warning message is displayed to warn the user not to give a shock, so the operator, etc., must be careful not to give a large vibration or shock to the machine while it is displayed. It is possible to prevent the performance of the motor from being deteriorated and the service life of the motor from being shortened when the shaft and the bearing of the shaft are in heavy contact with each other.

[Brief description of drawings]

FIG. 1 is a block diagram showing a control system of an image forming apparatus and its related configuration for explaining an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing an overall configuration of a digital copying machine which is also the image forming apparatus.

FIG. 3 is a schematic diagram showing the configuration of an image reading device 12 provided in the digital copying machine.

FIG. 4 is a perspective view showing a laser beam scanning device 27 also provided in the digital copying machine.

5 is a flowchart showing a routine relating to a warning display process performed by a microcomputer included in the power supply control device 1 of FIG.

FIG. 6 is a timing chart showing a period from when the main switch 5 is turned off to when the polygon motor 4 is stopped in the image forming apparatus of FIG.

FIG. 7 is a block diagram similar to FIG. 1 for explaining another embodiment of the image forming apparatus according to the present invention.

FIG. 8 is a flowchart showing a part of a routine relating to warning display processing performed by the microcomputer of the power supply control device 1 ′ of the image forming apparatus.

FIG. 9 is a block diagram similar to FIG. 1 for explaining still another embodiment of the image forming apparatus according to the present invention.

FIG. 10 is a power supply control device 1 ″ of the image forming apparatus.
FIG. 10 is a flowchart showing a routine relating to a warning display process performed by the microcomputer of FIG.

FIG. 11 is a configuration diagram showing an example of a polygon motor employing a conventional air dynamic pressure bearing.

[Explanation of symbols] 1,1 ', 1 ": Power supply control device 2: Laser scanning device control circuit 3, 3 ': Polygon motor control circuit 4: Polygon motor 5: Main switch 7: Timer circuit 8: Power supply control circuit 9: Display control circuit 10: Device body 24: Display unit 27: Laser beam scanning device 42: Polygon mirror 44: fθ lens 45: Reflecting mirror

Claims (6)

(57) [Claims] 1. A beam generating means modulated based on an image signal, a polygon mirror for deflecting a beam generated by the beam generating means, and a motor using a dynamic pressure bearing for rotating the polygon mirror. In an image forming apparatus having a laser beam scanning device having an optical system for forming a beam deflected and scanned by rotation of the polygon mirror at a predetermined position, and having a display unit at a position visible from the outside of the device body, An image forming apparatus, comprising means for displaying a message on the display unit for a caution not to apply vibration or shock to the apparatus body for a predetermined time after the main power is turned off. 2. The image forming apparatus according to claim 1, wherein the predetermined time is equal to or longer than a predicted time from when the main power supply is turned off to when the motor is stopped. 3. The image forming apparatus according to claim 1, wherein the motor can rotate at a plurality of rotation speeds, and the rotation speed of the motor is set when the main power supply is turned off. The image forming apparatus further comprises means for changing the predetermined time. 4. A beam generating means modulated based on an image signal, a polygon mirror for deflecting the beam generated by the beam generating means, and a motor using a dynamic pressure bearing for rotating the polygon mirror. In an image forming apparatus having a laser beam scanning device having an optical system for forming a beam deflected and scanned by rotation of the polygon mirror at a predetermined position, and having a display unit at a position visible from the outside of the device body, A motor rotation detecting means for detecting the rotation of the motor and vibration or impact is applied to the main body of the apparatus until the motor rotation detecting means stops detecting the rotation of the motor after the main power is turned off. An image forming apparatus, characterized in that a means for displaying a message to call attention so as not to be present is provided. 5. The image forming apparatus according to claim 4,
The image forming apparatus, wherein the motor rotation detecting means is means for detecting the rotation of the motor by the counter electromotive force of the motor. 6. The image forming apparatus according to claim 4,
The image forming apparatus is characterized in that the motor rotation detecting means is means for detecting the rotation of the motor based on the output of a Hall element provided in the motor.