JP2003169487A - Apparatus with oscillation-wave drive unit and control method of oscillation-wave drive unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent squeak noise generated when an oscillation-wave motor is driven at prescribed conditions (mainly, at a low load and at a low speed). <P>SOLUTION: A break for applying a load onto an output shaft of the oscillation-wave motor is provided. When the oscillation motor generates squeak noise, the oscillation-wave motor is driven while a load is applied to the output shaft by the break. <P>COPYRIGHT: (C)2003,JPO

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, and an electrophotographic apparatus, such as a printer, for rotating a transfer member such as a photosensitive drum, a transfer belt or a transfer drum by a vibration wave motor which is a driving means with good rotation accuracy. The present invention can be applied to equipment such as an apparatus, a copying machine, and a facsimile machine.

[0002]

2. Description of the Related Art A vibration wave driving device such as a vibration wave motor generally applies an alternating signal to excite a vibration wave in a vibrating body, as proposed in Japanese Patent Application Laid-Open No. 58-148682. This is a motor in which a rotor (rotating body) that is brought into pressure contact with a vibrating body is rotated by this vibration wave to obtain a driving force, and the driving force thereof is disclosed in JP-A-63-1379 and JP-A-60-176470. Japanese Patent Laid-Open No. 59-2
As described in detail in JP-A-04477, etc., stable rotatability is realized at a constant speed.

[0003]

When a vibration wave motor with good rotation accuracy is used as the driving means for the photosensitive drum or transfer belt of an electrophotographic apparatus, an abnormal noise (hereinafter referred to as squeal) is generated from the vibration wave motor depending on the rotation conditions. ) Occurs and the rotation characteristics are deteriorated. This squeal is different from the abnormal sound generated near the resonance frequency of the vibration wave motor, as shown in FIG.
Occurs in a region satisfying a predetermined load torque and rotation speed indicated by the diagonal line. As can be seen from FIG. 7, the number of revolutions (driving frequency) and the load torque generated differ depending on the state of the motor, but they often occur at low load and low rotation.

It has been confirmed that this squeal does not occur at the maximum rotational speed or maximum torque of each vibration wave motor. However, when the number of rotations of the motor is low and the load applied to the motor becomes light, squeal may occur. Therefore, in order not to cause malfunction, the motor is not driven in the shaded area in FIG. It is desirable to do so.

[0005]

In order to solve the above problems, the invention as set forth in claim 1 of the present application is a vibration wave for exciting a vibration wave in a vibrating body to rotationally move a rotating body in contact with the vibrator. In a device having a drive device as a drive source, the device has a load applying means for applying a load to the rotational movement of the rotating body, and when the load applied to the rotating body during driving of the vibration wave drive device is within a predetermined range, It is characterized in that the load applying means applies a load such that the load applied to the rotating body exceeds the predetermined range.

Similarly, to solve the above-mentioned problems, the invention according to claim 10 of the present application controls a vibration wave driving device for exciting a vibration wave in a vibration body and rotatingly moving a rotation body in contact with the vibrator. In the method, when the load applied to the rotating body is within a predetermined range when the vibration wave driving device is driven, the load is applied to the rotating body so that the load applied to the rotating body exceeds the predetermined range. It is what

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) FIGS.
Shows a first embodiment of the present invention.

FIG. 2 shows the overall schematic structure of the color image forming apparatus. First, the configuration of the color reader unit will be described.

Reference numeral 213 is a CCD, 211 is a substrate on which the CCD 213 is mounted, 212 is a printer processing section, 201 is a platen glass (platen), and 202 is a document feeder (note
There is also a configuration in which a mirror surface pressure plate or a white pressure plate (not shown) is mounted in place of the document feeding device 202), 203 and 2
Reference numeral 04 is a light source of a halogen lamp or a fluorescent lamp that illuminates the original, 205 and 206 are reflectors that collect the light of the light sources 203 and 204 onto the original, 207, 208 and 209 are mirrors, and 210 is reflected light from the original or projection. Light the CCD 21
A lens for condensing on 3 and 214 for the halogen lamp 20
A carriage 315 for accommodating the mirrors 3,204, the reflecting umbrellas 205,206 and the mirror 207 is a carriage 215 for accommodating the mirrors 208,209. In addition, the speed of the carriage 214 is V
Then, the carriage 215 mechanically moves at a speed of V / 2 in a direction perpendicular to the electrical scanning (main scanning) direction of the CCD 213 to scan (sub-scan) the entire surface of the document.

Next, the structure of the printer section in FIG. 2 will be described. 217M is a magenta (M) image forming unit 217
C is a cyan (C) image forming unit, 217C is a yellow (Y) image forming unit, and 217K is a black (K) image forming unit. Since the respective configurations are almost the same, the M image forming unit 2
17M will be described in detail, and description of other image forming units will be omitted.

In the M image forming unit 217M, 221M
Is a photosensitive drum on which a latent image is formed by the light from the LED recording head 219M. 220M is a primary charger that charges the surface of the photosensitive drum 221M to a predetermined potential to prepare for latent image formation. A developing device 222M develops the latent image on the photosensitive drum 221M to form a toner image. The developing device 222M includes a sleeve 218M for applying a developing bias to develop.

A transfer charger 223M discharges from the back surface of the transfer material conveying belt 233 to transfer the toner image on the photosensitive drum 221M to a recording paper or the like on the transfer material conveying belt 233. In this embodiment, since the transfer efficiency is high, the cleaner portion is not arranged, but it goes without saying that there is no problem even if the cleaner portion is attached (similarly, cyan (C)).
217C to 223C, Yellow (Y) 217Y to 2C
23Y, black (K) is 217K to 223K).

Next, a procedure for transferring a toner image onto a transfer material such as recording paper will be described. Transfer materials such as recording paper stored in the cassettes 240 and 241 are picked up by the pickup roller 23.
9 and 238, the sheet is supplied to the transfer material conveying belt 233 by the sheet feeding rollers 236 and 237. The supplied recording paper is charged by the adsorption charging device 246. 248a ~
248d is a transfer material conveying belt roller, which drives the transfer material conveying belt 233, and 248a is an adsorption charger 246.
The recording material and the like are charged in a pair with the transfer material conveying belt 2
The recording paper or the like is adsorbed on 33. In this embodiment, the transfer material transport belt roller 248c is connected to the transfer material transport belt 23.
Although it is a drive roller for driving 3, the other transport belt rollers 248a, 248 may be used depending on the configuration of the apparatus.
Either b or 248d may be used as the drive roller.

A paper edge sensor 247 detects the edge of the recording paper or the like on the transfer material conveying belt 233. The detection signal of the paper edge sensor 247 is sent from the printer unit to the color reader unit and used as a sub-scanning synchronization signal when sending a video signal from the color reader unit to the printer unit (without using this signal. It is a well-known fact that it is possible to generate a synchronization signal, and the above configuration is not limited to the present invention, for example, the paper feed rollers 236 and 237.
It is also possible to use as a synchronization signal at the drive timing of).

Thereafter, the recording paper or the like is transferred onto the transfer material conveying belt 23.
The toner image is formed on the surface of the image forming units 217M to 217K in the order of MCYK. The transfer material such as recording paper that has passed through the K image forming unit 217K is separated from the transfer material conveying belt 233 after being discharged by the discharging charger 249 in order to facilitate separation from the transfer material conveying belt 233. Reference numeral 250 denotes a peeling charger, which prevents image disturbance due to peeling discharge when the recording paper or the like is separated from the transfer material conveying belt 233. The separated recording paper or the like is charged by pre-fixing chargers 251 and 252 in order to supplement the toner suction force and prevent image disturbance,
The toner image is heat-fixed by the fixing device 234 and is discharged to the discharge tray 235.

In this embodiment, a vibration wave motor is used as a drive motor for rotating the photosensitive drums 221M to 221K, and the transfer material conveying belt 233 is used.
The vibration wave motor 101 is also used as a drive motor for rotating the drive roller 248C for driving the.

As described above, the vibration wave motor uses the traveling wave excited in the vibrating body by applying the alternating signal, and is stable at the constant speed detected by the speed sensor for detecting the driving speed of the motor. The frequency of the drive signal, the voltage value of the drive signal, or the pulse width of the drive signal is controlled according to the speed detection signal for rotation.

FIG. 3 shows a block diagram of the vibration wave motor control system, and the speed control of the vibration wave motor will be briefly described below.

Reference numeral 301 in FIG. 3 denotes a target speed setting unit in which the speed of the vibration wave motor is set by a control unit (not shown). The speed control circuit 302 performs speed control by determining the difference between the target speed set in the target speed setting unit 301 and the speed signal obtained from the encoder 305 for measuring the rotation speed of the vibration wave motor. Is.

The speed control circuit 302 has a frequency (hereinafter referred to as a drive frequency) or a pulse width (hereinafter referred to as a drive pulse width) of a drive signal applied to the vibrating body according to the difference between the target speed and the actual speed. To change. The vibration wave motor can increase the rotation speed by lowering the drive frequency or widening the drive pulse width (higher drive voltage), and conversely by increasing the drive frequency or narrowing the drive pulse width. The rotation speed can be reduced. Therefore, even if either the drive frequency or the drive pulse width is fixed, the speed can be controlled by controlling the other.

In the present embodiment, the case where the drive pulse width is constant and only the drive frequency is changed will be described as an example. Speed acceleration / deceleration is judged by the speed control circuit 302,
Determine if the current drive frequency needs to be increased or decreased. This determination result is transmitted to the frequency setting circuit 303, and the frequency setting circuit 303 inputs necessary driving frequency information to the pulse width setting circuit 304.
In this pulse width setting circuit 304, at the input frequency,
In addition, a drive signal having a predetermined pulse width is generated. From this drive signal, a driver (not shown) drives each other 90 times.
Generates two sine waves that are out of phase with each other and drives the vibration wave motor.

When the speed control circuit 302 detects that the rotation speed of the motor is within the predetermined range, it sends a speed lock signal to perform constant speed driving.

Here, FIG. 1 is a diagram best showing the features of the present invention. A brake 102 is provided on the output shaft 103 of the vibration wave motor 101 that drives the photosensitive drum 221. When only the photosensitive drum is driven, the load is light and the squeal may occur in the vibration wave motor. The drive characteristics of the vibration wave motor at this time are shown in FIG.

FIG. 4 shows the characteristics of the rotation speed when the torque is increased from the no-load state while the drive pulse width and the drive frequency are fixed in the relationship between the motor load torque and the rotation speed. There is. The operating area of the vibration wave motor when squealing is generated corresponds to the shaded area in FIG. 4 (hereinafter referred to as squealing area).

As can be seen from FIG. 4, when the operating region of the motor is within the squealing region, it can be shifted outside the squealing region by changing the rotation speed of the vibration wave motor or by increasing the rotation torque. it can. However, since the photosensitive drum 221 of the electrophotographic apparatus has an appropriate rotation speed depending on the type of paper and the like, the rotation speed of the motor cannot be changed.

Therefore, the output shaft 1 of the vibration wave motor 101
03 by the brake 102, the output shaft 10
The load Ta is applied to the rotor of the vibration wave motor connected to the motor 3, and the minimum load torque applied to the motor during driving is raised above the maximum torque Ta in the squeaking region to drive the motor rotor. As a result, the operation area of the motor is shifted out of the squeal area. The load applied by the brake 102 is not necessarily Ta, as long as the minimum load torque applied to the motor exceeds Ta.

The rotation speed of the rotor of the vibration wave motor 101 when the photosensitive drum is rotated at a predetermined speed is defined as the used rotation speed R. When the vibration wave motor is driven at the use rotation speed R, and the maximum use torque applied to the vibration wave motor by the photosensitive drum is Tmax in FIG. 4, the operation area of the vibration wave motor falls within the squeal area in FIG. I will end up. However, by adding the load Ta by the brake 102, the operating region shifts to the right, the minimum torque to be used exceeds the maximum torque Ta in the squeaking region, and the operating region shifts outside the squeaking region. Of course, in this state, no noise is generated in the vibration wave motor.

In the apparatus shown in FIG. 1, the output shaft 103 is provided on both sides of the motor, and the photosensitive drum 221 is provided on one side of the motor.
Although the brake 102 is provided on the other side, it is not limited to this shape, and of course, the brake 102 may be provided between the vibration wave motor 101 and the photosensitive drum 221.

In principle, it is not always necessary to apply a load to the output shaft, and any other method may be used as long as the rotor of the vibration wave motor is loaded. A method of providing a load applying means such as a brake on the output shaft is the most easily realized method.

In the above, the brake 1 provided on the output shaft is also used.
Although 02 has a configuration for applying a predetermined load Ta, the load to be applied need not be a predetermined value and may be variable.

Further, the brake 102 does not always need to be operated, and may be electrically ON / OFF switchable. As a structure that can be electrically switched ON / OFF, it is conceivable to use a powder brake whose amount of brake can be changed by applying an electric current, or to use an electromagnetic clutch between the brake and the motor. With such a configuration, the brake can be applied according to the occurrence of squeal.

(Second Embodiment) Although the first embodiment has been described with respect to the prevention of squeaking when the vibration wave motor is driven at a constant speed, the present invention is not limited to this. In the second embodiment, by using the brake described in the first embodiment, the vibration wave motor can be driven without squealing other than the constant speed driving.

Generally, there are few cases where the motor is used only at a specific rotation speed R used. In fact, in electrophotographic devices,
It is necessary to switch the speed according to the type of transfer material. It is a well-known fact that the fixing property of an image by a fixing device is improved by making it fast for thin paper and slow for thick paper.

When the appropriate rotation speed of the vibration wave motor when the transfer material is thin paper is R1 and when it is thick paper is R2, the result is as shown in FIG. When thin paper is used, that is, when it is used at the rotational speed R1, there is no squeaking region in the torque applied to the vibration wave motor (within the range up to the maximum usable torque Tmax).

In this state, if the load Ta is added to the vibration wave motor by the brake 102 as in the case of the first embodiment, the operating region shifts to the right by Ta in FIG. In this case, the upper limit of the torque-rotation characteristic is shown in FIG.
If it corresponds to the uppermost line of the above, the margin of the operating region of the vibration wave motor is reduced, which is not desirable for stable operation.

Therefore, the operating speed of the vibration wave motor is R
In the case of 1, it is necessary to control the brake 102 so as not to add the load Ta. When the rotational speed used is R2, as described in the first embodiment, the powder brake or the clutch is controlled so that the torque of Ta is generated in the motor by the brake 102, and the squeaking is prevented.

The above is R1 in which the rotational speed used is higher than R2.
However, if the rotation speed is outside the squeaking range (for example, a low speed range below the squeaking range in FIG. 5), it is needless to say that the load Ta need not be added by the brake. Yes.

(Third Embodiment) In the second embodiment, the rotation speed of the vibration wave motor is in a different region, whereas in the third embodiment, the rotation speed of the vibration wave motor is This is an example of a case where the load applied to the motor is constant and the load is different.

FIG. 6 shows the operating range of the vibration wave motor when the loads are different. Although the rotation speed used is constant R, the case where the motor is driven in different operation regions under low load and high load is shown.

In the first embodiment, the example in which the photosensitive drum is rotated is used. However, for example, when the photosensitive drum is operated by connecting another load with drive connecting means (clutch etc.) Load operating area occurs.

Since the operating region is included in the squealing region when the load is low, the brake 102 is the same as in the first embodiment.
The load Ta is applied to shift the operating region to outside the squeaking region. When the load is high, the operating region is not included in the squealing region, and if the load Ta is added, if the upper limit of the torque-rotation characteristic corresponds to the top line in FIG.
Since the margin of the operation area of the vibration wave motor is reduced, it is not desirable for stable operation.

Therefore, when the load applied to the vibration wave motor is large to some extent, it is necessary to control the brake 102 not to add the load.

In the above-described first to third embodiments, an explanation has been given by taking as an example the case where the operating region of the motor is included in the squealing region when the vibration wave motor is driven mainly at low load and low rotation. However, squeal does not always occur at the time of driving with low load and low rotation. Since the driving characteristics differ depending on the individual vibration wave motors, the conditions of the squeaking region also differ depending on the individual vibration wave motors.

Therefore, each vibration wave motor may be driven under desired conditions, and when squeal occurs, a load may be applied to the rotor of the vibration wave motor. In other words, it suffices to activate the brake only when the operating area of the vibration wave motor is within the range of the squealing area, and when the operating area of the vibration wave motor comes out of the range of the squeaking area without operating the brake. May control to stop the brake.

As described above, it may be easy to construct a powder brake or the like in which the amount of braking can be varied by applying a current, as described above.

Further, in the above-described embodiment, an example in which the pulse width of the drive signal is fixed and the frequency is changed to rotate the motor at a desired speed has been described. However, the frequency is fixed and the pulse width is changed. When changing to a desired rotation speed,
Alternatively, it is needless to say that the rotor of the vibration wave motor can be loaded to prevent squeal even if the frequency and the pulse width are both changed to achieve a desired speed.

Further, what rotates using the vibration wave motor as a drive source is not limited to the photosensitive drum, but may be a transfer belt or a transfer drum. The present invention can be applied not only to the electrophotographic apparatus but also to devices such as a printer, a transfer device, and a facsimile. Further, the present invention is not limited to these image forming apparatuses, but the present invention effectively acts on a vibration wave motor that produces a squeal according to the speed or load condition.

[0048]

As described above, when the squeal is generated by driving the vibration wave motor, the load is forcibly applied to the motor to shift the operating region of the motor to the outside of the squealing region. Can be prevented.

The conditions of this squealing region are low speed and low load in the case of driving the photosensitive drum of the electrophotographic apparatus, but this applies a load torque amount and torque according to the characteristics of each vibration wave motor. It is necessary to determine the conditions.

Depending on the operation area, it may or may not be used in the squealing area. In this case, when the rotation speeds are different, the load is added only in the rotation speed mode in which the squealing occurs.

When the load is different, the load is added only in the squealing area mode (mainly low load) to control the vibration wave motor outside the squealing area. This is effective in preventing the vibration and sufficiently bringing out the performance of the vibration wave motor.

[Brief description of drawings]

FIG. 1 is a diagram showing a vibration wave motor in which a brake is provided on an output shaft according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a color image forming apparatus.

FIG. 3 is a block diagram showing a speed control system of a vibration wave motor.

FIG. 4 is a diagram showing a relationship between a torque-rotational speed characteristic and a squeal region when the driving speed of the vibration wave motor is constant.

FIG. 5 is a diagram showing a relationship between a torque-rotational speed characteristic and a squeal region when the driving speed of the vibration wave motor is variable.

FIG. 6 is a diagram showing a relationship between a torque-rotational speed characteristic and a squeal region when the load applied to the vibration wave motor is variable.

FIG. 7 is a diagram showing a relationship between torque-rotational speed characteristics of a vibration wave motor and a squeaking region.

[Explanation of symbols]

101 vibration wave motor 102 brake 103 output shaft 221 Photosensitive drum 301 Target speed setting unit 302 Speed control circuit 303 Frequency setting circuit 304 pulse width setting circuit 305 encoder

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Claims (15)

[Claims] 1. A device having as a drive source a vibration wave driving device for exciting a vibration wave in a vibrating body to rotationally move a rotating body in contact with the vibrator, wherein a load is applied to the rotational movement of the rotating body. The load applying means applies a load such that the load applied to the rotating body exceeds the predetermined range when the load applied to the rotating body is within a predetermined range when the vibration wave driving device is driven. An apparatus having an oscillatory wave drive device characterized by the above. 2. A device having as a drive source a vibration wave driving device for exciting a vibration wave in a vibrating body to rotationally move a rotating body in contact with the vibrator, wherein a load is applied to the rotational movement of the rotating body. And a load applied to the rotating body during driving of the vibration wave driving device is within a predetermined range, and a rotation speed of the rotating body is within a predetermined range, the load applying means rotates the rotating body. A device having a vibration wave driving device, wherein a load is applied so that the load on the body exceeds the predetermined range. 3. A device having, as a drive source, a vibration wave drive device for exciting a vibration wave in a vibrating body to rotationally move a rotating body in contact with the vibrator, wherein a load is applied to apply a load to the rotational movement of the rotating body. When the load applied to the rotating body is within a predetermined range when the vibration wave driving device is driven, the load applying unit applies a load so that the load applied to the rotating body exceeds the predetermined range. And an oscillatory wave drive device for rotating the rotating body. 4. A device having as a drive source a vibration wave driving device for exciting a vibration wave in a vibrating body to rotationally move a rotating body in contact with the vibrator, wherein a load is applied to the rotational movement of the rotating body. And a load applied to the rotating body during driving of the vibration wave driving device is within a predetermined range, and a rotation speed of the rotating body is within a predetermined range, the load applying means rotates the rotating body. A device having a vibration wave drive device, characterized in that a load applied to a body exceeds the predetermined range to rotate the rotating body. 5. A device having as a drive source a vibration wave driving device for exciting a vibration wave in a vibrating body to rotationally move a rotating body in contact with the vibrator, wherein a load is applied to apply a load to the rotational movement of the rotating body. When an abnormal sound is generated when the vibration wave driving device is driven, the load applying unit applies a load enough to eliminate the abnormal sound to rotate the rotating body. And a device having a vibration wave driving device. 6. A vibrating body is provided with a rotating body that excites a vibration wave and makes a rotational movement by contacting the vibrator, a load applied to the rotating body is within a predetermined range, and a rotation speed of the rotation is A device having as a drive source a vibration wave driving device that generates an abnormal sound when within a predetermined range, comprising a load applying means for applying a load to the rotational movement of the rotating body, the load applying means comprising: A device having a vibration wave driving device, characterized in that the rotating body is rotated by applying a load such that the load on the body is larger than the maximum value of the predetermined range. 7. The vibration wave driving device according to claim 1, wherein the load applying means does not apply a load when the vibration wave driving device does not generate an abnormal sound. A device that has. 8. A device having a vibration wave driving device according to claim 1, wherein the load applying means is a brake. 9. The apparatus having a vibration wave driving device according to claim 8, wherein the brake operates only when the rotation speed and the load torque of the vibration wave driving device are within predetermined ranges. 10. A method for controlling a vibration wave driving device, wherein a vibration wave is excited in a vibrating body, and a rotating body in contact with the vibrator is rotationally moved, wherein a load applied to the rotating body when the vibration wave driving device is driven. Is within a predetermined range, a load is applied to the rotating body so that the load applied to the rotating body exceeds the predetermined range. 11. A method of controlling a vibration wave driving device, wherein a vibration wave is excited in a vibrating body, and a rotating body in contact with said vibrator is rotationally moved, wherein a load applied to said rotating body when driving said vibration wave driving device. Is within a predetermined range and the rotation speed of the rotating body is within a predetermined range, a load is applied to the rotating body so that the load applied to the rotating body exceeds the predetermined range. A method for controlling an oscillatory wave drive device. 12. A method of controlling a vibration wave driving device, wherein a vibration wave is excited in a vibrating body and a rotating body in contact with the vibrator is rotationally moved, when an abnormal sound is generated when the vibration wave driving device is driven. Is a control method of the vibration wave drive device, wherein the rotating body is rotated by applying a load enough to eliminate the abnormal sound to the rotating body. 13. A vibrating body is provided with a rotating body that excites a vibration wave and makes a rotational movement by contacting the vibrator, wherein a load applied to the rotating body is within a predetermined range, and a rotation speed of the rotation is When in a predetermined range, in a control method of a vibration wave driving device that generates an abnormal sound, the load applied to the rotating body is added to the rotating body only a load larger than the maximum value of the predetermined range, A method of controlling a vibration wave driving device, comprising rotating the rotating body. 14. A load is not applied when the vibration wave driving device does not generate an abnormal sound.
The method of controlling the vibration wave driving device according to any one of 0 to 13. 15. The vibration wave driving device according to claim 10, wherein the load is applied only when the rotation speed and the load torque of the vibration wave driving device are within predetermined ranges. Control method.