JPH11146675A - Motor control device and image forming device - Google Patents

Abstract

(57) [Problem] For example, in an electrophotographic image forming apparatus, in an ultrasonic motor speed feedback loop control,
When the wear of the motor progresses to exceed the maximum adjustment amount of the drive frequency, the drive voltage, and the like, a means for solving the problem of lowering the constant speed rotation performance and damaging the motor and the like is provided. For this reason, various measured values capable of estimating a motor driving state such as a driving speed of a target speed and a driving position shift are regularly set even during a constant speed rotation that does not require a processing procedure such as updating of a target speed. A motor control device is provided for detecting the occurrence of a drive abnormality by constantly monitoring the magnitude of the difference from the set standard value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a motor control device and an image forming apparatus using the same.

[0002]

2. Description of the Related Art Generally, in a control device using a motor as a drive source, it is required that a drive member driven by the motor be repeatedly operated while maintaining a certain level of precision. Is done.

In particular, for example, in an electrophotographic image forming apparatus, in order to form a highly accurate image, a photosensitive member driving motor or a transfer member driving motor is used.
It is required to use a motor with higher rotation accuracy, and in order to achieve the purpose, an ultrasonic motor has been used as a motor for driving a photosensitive member or as a part of a motor for driving a transfer member. ing.

An ultrasonic motor is disclosed in, for example, Japanese Patent Application Laid-Open No. 58-1
This is a motor using ultrasonic vibration proposed in Japanese Patent Application Publication No. 4682/1994.
-1379, JP-A-60-176470, JP-A-5
As described in detail in respective publications such as Japanese Patent Application Laid-Open No. 9-204477, a drive frequency and a control amount, which are control amounts according to a difference between a speed signal from a speed detecting means such as an encoder signal and a preset target speed, are described. The so-called “speed feedback loop control” that constantly adjusts the drive voltage and the pulse width of the drive voltage realizes stable rotation performance at a constant speed.

When accelerating or decelerating this type of ultrasonic motor in the above-described control system, a speed corresponding to a target constant speed is set as a target speed. The vehicle gradually accelerates or decelerates, finally reaches the set speed, and shifts to a constant speed rotation state.

However, in this case, the speed change of the ultrasonic motor at the time of acceleration / deceleration differs depending on the inherent characteristics of the motor. It is necessary to periodically update the intermediate target speed up to that point.

On the other hand, the speed adjustment during the constant speed rotation is always performed by adjusting the control amount such as the drive frequency / drive voltage and the pulse width of the drive voltage in the feedback loop control system. Need not be performed on a regular basis.

[0008]

However, the friction between the stator and the rollers of the ultrasonic motor generated when operating the ultrasonic motor and the motor driving member of the control device, and the friction between a plurality of motor driving members driven by the motor. The abrasion of the motor and the motor driving member due to the generation of friction is inevitable in principle. Normally, in the present control system, the drive frequency and the drive voltage, which are the control amounts, and the pulse width of the drive voltage are adjusted by the speed feedback loop control.
Because the amount of control can compensate for it, the rotation performance does not easily decrease, but the above wear progresses,
If the control amount exceeds the maximum adjustment amount of the drive frequency / drive voltage or the pulse width of the drive voltage, it becomes impossible to perform normal feedback loop control, and the constant speed rotation performance is reduced and the motor and the motor There was a fear that the driving member might be damaged.

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and has as its object to provide a motor control device capable of solving these problems and an image forming apparatus using the same.

[0010]

Therefore, in the present invention, any one of the following motor control devices (1) to (15) and the following (16) to ( The object is achieved by providing any one of the image forming apparatuses described in the item 21).

(1) Target speed setting means for setting a target rotation speed, and a speed feedback loop control using a rotation speed detection signal corresponding to the target speed set by the target speed setting means. Motor speed adjustment means for adjusting the rotation speed of the motor, drive status detection means for detecting the drive status of the motor controlled by the motor speed adjustment device, and detection by the drive status detection means Based on the driving status information of the motor, based on the motor drive error determining means for determining an error in the drive of the motor, performing a drive error determination by the motor drive error determination means during rotation drive, A motor control device for periodically monitoring an error.

(2) In particular, even when it is not necessary to update the target speed by the target speed setting means for control (hereinafter, referred to as a target speed setting unnecessary state), the drive error judgment by the motor drive error judgment means is periodically performed. (1) The motor control device according to the above (1), wherein the motor control device performs the error monitoring.

(3) When the target speed setting unnecessary state is set,
Particularly, the motor control device according to the above (2), wherein the motor is driven to rotate at a constant speed.

(4) In the motor speed adjusting means,
(1) wherein the motor whose rotation speed is controlled by feedback loop control using the rotation speed detection signal is an ultrasonic motor controlled by ultrasonic vibration control.
The motor control device according to the item.

(5) The motor control device according to (4), wherein the rotation speed detection signal used for controlling the rotation speed of the ultrasonic motor is an encoder output signal.

(6) The motor control device according to (4), wherein the feedback loop control amount during speed adjustment by the motor speed adjustment means is an ultrasonic pulse width or an ultrasonic frequency or both. .

(7) The motor drive status information is obtained by calculating the difference between the motor drive speed and the target speed (hereinafter, referred to as drive speed deviation) and the difference between the total motor rotation amount and the integral value of the target speed (hereinafter, referred to as the drive speed deviation). When the driving speed deviation or the driving position deviation, or both of them, exceed a predetermined specified value, the motor driving error determination means determines a driving error. The motor control device according to (1).

(8) Target speed setting means for setting a target rotation speed, and a speed feedback loop control using a rotation speed detection signal corresponding to the target speed set by the target speed setting means. Motor speed adjustment means for adjusting the rotation speed of the motor, drive status detection means for detecting the drive status of the motor controlled by the motor speed adjustment device, and detection by the drive status detection means Motor drive error determination means for determining an error in motor drive based on the obtained drive status information of the motor, wherein the drive error determination by the motor drive error determination means is performed in accordance with the drive status of the motor. A motor control device for performing error monitoring while changing a reference.

(9) In the motor speed adjusting means,
(8) wherein the motor whose rotation speed is controlled by the feedback loop control using the rotation speed detection signal is an ultrasonic motor controlled by ultrasonic guidance control.
The motor control device according to the item.

(10) The motor control device according to (9), wherein the rotation speed detection signal used for controlling the rotation speed of the ultrasonic motor is an encoder output signal.

(11) The motor control device according to (9), wherein the feedback loop control amount during speed adjustment by the motor speed adjusting means is an ultrasonic pulse width or an ultrasonic frequency or both. .

(12) The motor driving status information is a driving speed deviation and a driving position deviation. If the driving speed deviation and / or the driving position deviation exceeds a predetermined value, the motor driving error is detected. The motor control device according to the above (8), wherein the determination means determines a drive error.

(13) The drive error determination means changes a drive error determination reference during the entire period or a part of the period during which the motor is being driven during acceleration, constant speed rotation, or deceleration. 8) The motor control device according to the above.

(14) The drive error determination means does not make a drive error determination during the whole period or a part of the period during which the motor is being driven during acceleration, constant speed rotation, or deceleration. (8) The motor control device according to the above (8).

(15) The motor control device according to (14), wherein the partial period when the driving condition of the motor is accelerating is an initial stage of acceleration start.

(16) The motor control device according to the above (14), wherein the partial period when the driving state of the motor is decelerating is an initial stage of deceleration start.

(17) A motor control device according to any one of the above items (1) to (16), and a photosensitive member and / or a transfer member driven by the motor. Image forming device.

(18) The image forming apparatus according to (17), wherein the photosensitive member driven by the photosensitive member drive motor is a photosensitive drum.

(19) The image forming apparatus according to (17), wherein the transfer member driven by the transfer member drive motor is a transfer drum.

(20) The image forming apparatus according to (17), wherein the transfer member driven by the transfer member drive motor is a transfer belt.

(21) The image forming apparatus according to the above (20), further comprising the transfer belt, a plurality of the photosensitive members and a plurality of motors for driving the photosensitive members.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below.
The preferred embodiments will be described in detail with reference to the drawings.

[0033]

1 to 4 are explanatory views showing the structure of an image forming apparatus according to an embodiment of the present invention. Based on them, the basic configuration will be described.

(Configuration of Color Reader) First, the configuration of the color reader will be described.

FIG. 1 is a diagram showing an outline of the overall configuration of the image forming apparatus. Here, 101 is a CCD, 311 is a CC
A board 300 on which D101 is mounted, a control unit 300 for controlling the entire image forming apparatus, a reference numeral 312, a portion of the digital image processing unit shown in FIG.
A printer processing unit 301 including portions 202 to 205;
Denotes a platen glass (platen), and 302 denotes a document feeder (DF) (a mirror pressure plate (not shown) may be mounted in place of the document feeder 302).

Reference numerals 303 and 304 denote light sources (halogen lamps or fluorescent lamps) for illuminating the original, and 305 and 3 respectively.
Reference numeral 06 denotes a reflector for condensing the light from the light sources 303 and 304 on the original, reference numerals 307 to 309 denote mirrors, reference numeral 310 denotes a lens for condensing reflected light or projection light from the original on the CCD 101, and reference numeral 314 denotes a halogen. A carriage that houses the lamps 303 and 304, the reflectors 305 and 306, and the mirror 307;
Reference numeral 315 denotes a carriage that houses the mirrors 308 and 309, and 313 denotes an external interface (I / F) with another device.

The carriage 314 is moved at a speed V and the carriage 315 is moved at a speed V / 2 mechanically in the direction perpendicular to the electrical scanning (main scanning) direction of the CCD 101, so that the entire surface of the document is covered. Scan (sub-scan).

As shown in the block diagram of FIG. 2, the control unit 300 has a CPU 401 having an I / F for exchanging information for controlling the digital image processing unit 312 and the printer control I / F 357, respectively. And an operation unit 402. The operation unit 402 is configured with a touch panel-equipped liquid crystal for inputting processing execution contents by an operator and notifying the operator of information regarding processing.

Next, the digital image processing unit 312 shown in FIG.
Will be described in detail. FIG. 4 shows the digital image processing unit 3.
FIG. 12 is a block diagram illustrating a detailed configuration of a twelfth embodiment.

The original on the original platen glass 301 is
The light reflected from the CCD 304 is reflected by the CCD 1
01 and converted into an electric signal (CCD 101
Means that if the color sensor is an RGB color filter,
The CCD may be inline on the line CCD in the order of RGB, or may be a 3-line CCD in which an R filter, a G filter, and a B filter are arranged for each CCD.
It may be different from the CD.)

Then, the electric signal (analog image signal) is input to the image processing unit 312, and the clamp & Am
p. & S / H & A / D unit 102 sample and hold (S
/ H), the dark level of the analog image signal is clamped to the reference potential, amplified to a predetermined amount (the processing order is not limited to the notation order), A / D converted, and, for example, RGB.
It is converted into an 8-bit digital signal.

The RGB signals are output to the shading unit 1.
03, after shading correction and black correction are performed,
In the connection & MTF correction & document detection unit 104, the CCD
If the 101 is a three-line CCD, the splicing process adjusts the delay amount for each line according to the reading speed and corrects the signal timing so that the three lines have the same reading position because the reading positions between the lines are different. In the MTF correction, the reading MTF changes depending on the reading speed and the magnification, so the change is corrected, and the document detection scans the document on the platen glass 301 to recognize the document size.

The digital signal whose read position timing has been corrected is input to the CCD 1 by the input masking unit 105.
01 and the spectral characteristics of the light sources 303 and 304 and the reflectors 305 and 306.

The output of the input masking unit 105 is
/ F signal is input to the selector 106 which can be switched. The signal output from the selector 106 is input to the color space compression & background removal & LOG conversion unit 107 and the background removal unit 115.

After the signal input to the background removal unit 115 is removed from the background, the signal is input to a black character determination unit 116 that determines whether or not the document is a black character of the document, and a black character signal is generated from the document.

The color space compression / background removal / LOG converter 107 to which the output of the other selector 106 is input.
Then, color space compression determines whether the read image signal is within the range that can be reproduced by the printer, and if so, corrects it so that it is within the range that the image signal can be reproduced by the printer. I do. Then, a background removal process is performed, and the RGB signals are converted into CMY signals by LOG conversion.

The timing of the signal generated by the black character determination unit 116 and the output signal of the color space compression / background removal / LOG conversion unit 107 are adjusted by a delay 108 to correct the timing.

The two types of signals are supplied to the moiré removing section 109
The moiré is removed at step 110, and at step 110, scaling processing is performed in the main scanning direction. Reference numeral 111 denotes a UCR & masking & black character reflection unit. A CMY signal is generated by a UCR process for a signal processed by the scaling unit 110, and a CMYK signal is corrected by the masking processing unit into a signal output from the printer.
The determination signal generated by the black character determination unit 116 is fed back to the CMYK signal.

UCR & Masking & Black Character Reflection Unit 111
Is subjected to density adjustment by the γ correction unit 112 and then subjected to smoothing or edge processing by the filter unit 113. The signal processed as described above is converted from an 8-bit multi-level signal into a binary signal by a binary conversion unit 201 (FIG. 3) (conversion method is any of dither method, error diffusion method, and error diffusion method). No problem.)

(Configuration of Printer Unit) Next, the configuration of the printer unit will be described. In FIG. 1, reference numeral 355 denotes a printer control I / F.
It serves as a port for receiving control signals from the PU 401. The printer unit performs an operation described below based on a control signal from the printer control I / F 355.

Next, the image forming section will be described in detail. In FIG. 1, 317 is an M image forming unit, and 318 is C
An image forming unit, 319 is an M image forming unit, and 320 is a K image forming unit. Since the configuration of each of the image forming units 317 to 320 is the same, the M image forming unit 317 will be described in detail below, and the description of the other image forming units will be omitted.

In the M image forming section 317, reference numeral 342 denotes a photosensitive (body) drum, on which a latent image is formed by light from the LED array 210. Reference numeral 321 denotes a primary charger, which charges the surface of the photosensitive drum 342 to a predetermined potential.
Prepare for latent image formation. A developing device 322 develops the latent image on the photosensitive drum 342 to form a toner image.

The developing device 322 includes a sleeve 345 for applying a developing bias to develop. A transfer charger 323 discharges from the back of the transfer belt 333 to transfer the toner image on the photosensitive drum 342 to recording paper on the transfer belt 333.

In this embodiment, since the transfer efficiency is good, no cleaner is provided (it goes without saying that there is no problem even if the cleaner is mounted). Also, the photosensitive drum 342
Is provided with a temperature detection sensor 353 for detecting the temperature of the photosensitive drum 342, and is used for controlling the rotation operation of the drum. The control method will be described later in detail. The other photosensitive drums 343, 34
4,345 for each temperature detection sensor
356 has a similar function.

Next, a procedure for forming an image on a recording paper or the like will be described. The recording paper and the like stored in the cassettes 340 and 341 are transferred by the pickup rollers 339 and 338 to the transfer belt 33 by the sheet feed rollers 336 and 337 one by one.
3 is supplied. The fed recording paper is supplied to the adsorption charger 3
Charged at 46. Reference numeral 348 denotes a transfer belt roller which drives the transfer belt 333 and
6, the recording paper or the like is charged, and the transfer belt 333 is charged.
To adsorb recording paper.

Reference numeral 347 denotes a paper edge sensor, which is a transfer belt 33.
3 to detect the leading edge of the recording paper or the like. The detection signal of the paper leading edge sensor is sent from the printer unit to the color reader unit, and is used as a sub-scanning synchronization signal when a video signal is sent from the color reader unit to the printer unit.

Thereafter, the recording paper or the like is conveyed by the transfer belt 333, and a toner image is formed on the surface of each of the image forming units 317 to 320 in the order of MCYK. K
The recording paper that has passed through the image forming unit 320 is transferred to the transfer belt 3
In order to facilitate separation from the transfer belt 33, the toner is removed from the transfer belt 333 after the charge is removed by the charge removal charger 349.

Reference numeral 350 denotes a peeling charger, which prevents image disturbance due to peeling discharge when recording paper or the like is separated from the transfer belt 333. The separated recording paper or the like is charged by the pre-fixing chargers 351 and 352 in order to compensate for the toner adsorption force and prevent image disturbance, and then the toner image is thermally fixed by the fixing device 334. The paper is discharged to the paper discharge tray 335.

FIG. 3 is a block diagram showing a detailed configuration of the printer processing unit. The LED image recording will be described with reference to FIG.

The binary CM generated by the image processing unit in FIG.
The YK image signal is a signal generated by the binary conversion unit based on the paper leading edge signal from the paper leading edge sensor 347 (FIG. 1). By adjusting the difference in distance from the image forming unit, four colors can be printed at predetermined positions. Each LED drive 206 to 209 is
A signal for driving 10 to 213 is generated.

In this embodiment, an ultrasonic motor is used as a drive motor for rotating each of the photosensitive drums 342 to 345 and the transfer belt 333 in FIG. The ultrasonic motor is a motor using ultrasonic vibration, and controls a driving frequency, a driving voltage, and a pulse width of the driving voltage according to a speed detection signal for rotating stably at a constant speed.

(Method of Controlling Ultrasonic Motor) An embodiment showing a method of controlling the ultrasonic motor will be described below. FIG. 5 is a block diagram for explaining an embodiment of the control method of the ultrasonic motor.

In FIG. 5, reference numeral 501 denotes an ultrasonic motor to which an encoder 506 is connected, and the number of revolutions is input to a speed control circuit 504. The speed control circuit 504
The speed feedback loop control using the frequency setting circuit 503 and the pulse width setting circuit 502 is performed based on the rotation speed of the encoder 506 so as to rotate at the target speed set by the target speed setting unit 505.

The speed deviation detecting unit 507 and the position deviation detecting unit 508 respectively determine the rotational speed deviation and the position of the ultrasonic motor 501 based on the output of the encoder 506 and the target speed set in the target speed setting unit 505. The deviation is constantly measured and calculated. The CPU 509 performs setting of a target speed at the time of acceleration, constant speed, and deceleration in this control system, error monitoring, and the like.

A ROM 510 is connected to the CPU 509 as storage means for storing data for performing these processes.
As necessary information, a target speed table 511, a speed deviation allowable value table 512, and a position deviation allowable value table 513 are stored.

Here, there is a relationship as shown in FIG. 6 between the drive frequency and the rotation speed of the ultrasonic motor. This curve has the characteristic of shifting in the direction indicated by the arrow in FIG. 6A as the temperature rises. In addition, the same curve is obtained by increasing the drive pulse width (equivalent to increasing the voltage), as shown in FIG.
In order to shift to the direction indicated by the arrow in (b), the drive pulse width may be increased in order to maintain a constant rotation speed with respect to the previous temperature rise, but there is a limit to speed correction using only the pulse width. For this reason, if the deviation of the characteristics becomes large, it is impossible to perform the correction by itself.

Therefore, in order to follow the speed, it is necessary to change the driving frequency. However, changing the driving frequency causes a change in the natural vibration characteristics of the motor. This can lead to image degradation. Therefore, while the latent image is formed on the surface of each photosensitive drum, it is necessary to take care that correction by changing the drive frequency is not performed.

Subsequently, the CPU 509 at the time of acceleration, constant speed, and deceleration of the ultrasonic motor in the control system described above.
The processing performed in FIG. 5 will be described in detail.

First, when starting acceleration, the CPU 50
9 is the target speed table 5 stored in the ROM 510
The target speed at the start of acceleration is acquired from 11 and set in the target speed setting unit 505. Subsequently, after a predetermined time, the next target speed during acceleration is acquired and set in the target speed setting unit 505. By repeating the above process, the target speed at constant speed is finally set in the target speed setting unit 505, and the process ends.

Next, at the time of constant speed, in this case, since the target speed at the time of constant speed has already been set in the final stage of the process at the time of acceleration, there is no need for the CPU 509 to do anything. Absent.

Next, when deceleration is started, the CPU 50
9 is the target speed table 5 stored in the ROM 510
The target speed at the start of deceleration is acquired from 11 and set in the target speed setting unit 505. Subsequently, after a predetermined time, the next deceleration target speed is obtained and set in the target speed setting unit 505. By repeating the above process, finally, the target speed at the constant speed after deceleration or, when stopping, the speed = 0 is set in the target speed setting unit 505, and the process ends.

The ultrasonic motors as drive sources are connected to the photosensitive drums 342 to 345 and the transfer belt 333 in the image processing apparatus having the structure as shown in the present embodiment. High-precision driving is performed by the speed feedback loop control of FIG.

However, each of the photosensitive drums 342 to 34
5 and the transfer belt 333, friction is always generated.
It is inevitable that the surfaces of the transfer belt 5 and the transfer belt 333 are worn.

When such wear increases, the fluctuation width of the correction by the driving pulse width and the driving frequency for stably performing the constant-speed rotation relatively increases, and the speed followability in performing the constant-speed stable driving gradually increases. Decrease. As a result, a speed shift during rotation of each of the photosensitive drums 342 to 345 and the transfer belt 333 and a shift of the rotation position, which is an integrated value thereof, occur. The occurrence of such a speed shift or a rotational position shift is a major obstacle to high-precision image formation. Particularly, in each of the photosensitive drums 342 to 345, a toner image must be formed on the surface thereof, so that the influence is great.

Therefore, in order to guarantee a certain level of image quality, the photosensitive drums 342 to 342 can be used even during the constant speed rotation in which the CPU 509 does not need to perform the target speed setting process.
It is necessary to constantly detect the speed deviation and the rotational position deviation of the transfer belt 345 and the transfer belt 333 and to continuously monitor the occurrence of the error. In this control system, the CPU 509 performs the above-described error detection processing.

(Error Detection Processing) The error detection processing performed by the CPU 509 will be described in detail.

First, the CPU 509 controls the speed deviation detecting section 50.
7 and the output of the displacement detection unit 508 are obtained.

Subsequently, the speed deviation allowable value and the position deviation allowable value at the time of constant speed rotation are acquired from the speed deviation allowable value table 512 and the position deviation allowable value table 513.

Next, each output of the speed shift detecting section 507 and the position shift detecting section 508 and the speed shift allowable value table 512
Then, the speed deviation allowable value and the position deviation allowable value acquired from the position deviation allowable value table 513 are compared, and one of the outputs of the speed deviation detecting unit 507 and the position deviation detecting unit 508 exceeds each allowable value. In this case, it is determined that a drive error has occurred, and the fact is determined as shown in FIG.
/ F357 to the CPU 401, and
U401 displays on the operation unit 402 that an error has occurred to notify the operator, and also provides an instruction for stopping each of the photosensitive drums 342 to 345 driven by the ultrasonic motor and the transfer belt 333. 5 for the CPU 509.

The CPU 509 performs deceleration processing by the ultrasonic motor control system according to the instruction received from the CPU 401, and immediately stops the photosensitive drums 342 to 345 and the transfer belt 333.

As described above, it is necessary to perform the above-described error detection processing even during the constant speed rotation in which the CPU 509 does not need to perform the target speed setting processing. It is necessary to perform the error detection processing even during the middle or deceleration processing.

However, if the target speed is set in a short time to accelerate and decelerate at high speed, the ultrasonic motor cannot follow the speed in time.
Speed deviation and position deviation occur. However, the occurrence of the speed deviation and the position deviation in such a case is to be tolerated to some extent. By doing so, it is necessary to avoid being determined as an error. For the same reason, it is needless to say that even during the same acceleration and deceleration, it is necessary to change the setting of the allowable value depending on the situation.

In consideration of the above points, in this embodiment, the relationship between the data stored in the target speed table 511, the allowable speed deviation table 512 and the allowable position deviation table 513 in FIG. 5 is shown in FIG. Show.

As shown in the figure, the target speed table 51
The speed deviation allowable value and the position deviation allowable value corresponding to the respective target speeds at the time of acceleration, constant speed, and deceleration stored in No. 1 are stored in the speed deviation allowable value table 512 and the position deviation allowable value table 513, respectively. . The speed deviation allowable value and the position deviation allowable value stored in the speed deviation allowable value table 512 and the position deviation allowable value table 513 are, for example, specific numerical values such as 701;
In some cases, it is the designation itself as to whether or not to perform the error detection based on the speed deviation and the position deviation as shown in FIG.

The CPU 509 sets the target speed according to each of the acceleration, constant speed, and deceleration conditions of the ultrasonic motor, and at the same time, sets the corresponding speed deviation allowable value and position deviation allowable value. The value is obtained from the speed deviation allowable value table 512 and the position deviation allowable value table 513, and error detection processing is performed in accordance with the values. Since the details of the error detection process at this time are the same as those of the error detection process described above, the duplicate description is omitted here.

(Other Embodiments) 1) In the above embodiment, an image forming apparatus using an ultrasonic motor as a photosensitive drum drive source has been described. However, a motor controlled by another speed feedback loop control method is used. In addition, a motor that can perform acceleration / deceleration and constant-speed rotation control by switching the target speed in that case can be used instead of the ultrasonic motor.

2) In the above embodiment, as a criterion for detecting a drive error of the motor, the super-speed calculated based on the output of the encoder 506 in the speed feedback loop control system and the target speed set in the target speed setting section 505. Although the rotational speed deviation value and the position deviation value of the sound wave motor 501 are used, it is also possible to detect a motor drive error based on other measured values capable of estimating the rotational state of the motor.

3) In the above embodiment, the motor is controlled by the speed feedback control method.
In addition, the image forming apparatus that detects an error based on the rotational speed deviation value and the position deviation value of the ultrasonic motor 501 calculated based on the output of the encoder 506 and the target speed set in the target speed setting unit 505 has been described. However, it is of course possible to apply a similar mechanism to a general control device.

4) In the above embodiment, an image forming apparatus of a photosensitive system using a plurality of photosensitive drums has been described. However, the present invention may be applied to an image forming apparatus in which a single photosensitive drum is used for exposure. Of course.

5) In the above embodiment, the image forming apparatus using the transfer system using the transfer belt has been described. However, it is needless to say that the present invention is applied to an image forming apparatus in which transfer is performed by using a transfer drum instead of the transfer belt. May be.

6) In the above embodiment, the image forming apparatus using the ultrasonic motor for the photosensitive drum drive system and the transfer belt drive system has been described. Of course, the same applies to motor drive systems other than these drive systems. It is, of course, possible to apply a different mechanism.

[0092]

As described above, according to the present invention,
In a speed feedback loop control system such as an ultrasonic motor, a rotation speed detection signal is set in advance, not only during acceleration / deceleration of the motor but also during constant speed rotation that does not require processing procedures such as updating the target speed. Drive speed deviation obtained from the difference from the set target speed, and the drive position deviation obtained from the difference between the sum of the motor rotation amount calculated from the rotation speed detection signal and the integral value of the target speed set as needed. Detects the occurrence of a drive abnormality by periodically acquiring various measured values that can estimate the motor drive status to be estimated, and constantly monitoring the magnitude of the difference between these measured values and a preset standard value. It was possible to do.

Further, according to the present invention, when the process of updating the target speed is frequently performed during the monitoring of the drive abnormality, for example, during acceleration / deceleration, depending on the followability of the ultrasonic motor, In consideration of the fact that the difference between the various measured values for estimating the motor driving situation and the preset standard value becomes large, it is possible to correct the standard value set according to the situation during control. Thereby, it is possible to prevent occurrence of erroneous error detection in that case.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of the overall configuration of an image forming apparatus.

FIG. 2 is a configuration block diagram of a control unit.

FIG. 3 is a block diagram illustrating a configuration of a digital image processing unit.

FIG. 4 is a configuration block diagram of a printer processing unit.

FIG. 5 is a block diagram showing an embodiment of a control method of the ultrasonic motor.

FIG. 6 is a diagram showing the relationship between the drive frequency and the number of revolutions of an ultrasonic motor.

FIG. 7 is a diagram showing a relationship among a target speed table, a speed deviation allowable value table, and a position deviation allowable value table according to the embodiment.

[Explanation of symbols]

 101 CCD 300 Control unit 312 Document feeder 312 Image processing unit 317 to 320 Each image forming unit 342 to 345 Photosensitive (body) drum 501 Ultrasonic motor 504 Speed control circuit 505 Target speed setting circuit 507 Speed shift detection unit 508 Position shift Detection unit

Claims (21)

[Claims] 1. A target speed setting means for setting a target rotation speed, and a motor controlled by a speed feedback loop control using a rotation speed detection signal corresponding to the target speed set by the target speed setting device. Motor speed adjusting means for adjusting the rotation speed of the motor, driving state detecting means for detecting the driving state of the motor controlled by the motor speed adjusting means, and detecting by the driving state detecting means A motor drive error determining means for determining an error in driving the motor based on the drive status information of the motor, and performing a drive error determination by the motor drive error determining means during the rotation driving; A motor control device characterized in that it performs error monitoring. 2. In particular, even when the control does not require the target speed setting means to update the target speed (hereinafter referred to as a target speed setting unnecessary state), the drive error determination by the motor drive error determination means is periodically performed. The motor control device according to claim 1, wherein the motor control device executes the error monitoring. 3. The motor control device according to claim 2, wherein the target speed setting unnecessary state is a state in which the motor is driven to rotate at a constant speed. 4. A motor whose rotational speed is controlled by a feedback loop control using a rotational speed detection signal in the motor speed adjusting means is an ultrasonic motor by ultrasonic vibration control. The motor control device according to any one of the preceding claims. 5. The motor control device according to claim 4, wherein a rotation speed detection signal used for controlling the rotation speed of the ultrasonic motor is an encoder output signal. 6. The motor control device according to claim 4, wherein the feedback loop control amount during speed adjustment by the motor speed adjustment means is an ultrasonic pulse width or an ultrasonic frequency or both. 7. The motor drive status information includes a difference between a motor drive speed and a target speed (hereinafter, referred to as a drive speed deviation), and a difference between a sum of motor rotation amounts and an integral value of a target speed (hereinafter, drive). The motor drive error determining means determines that a drive error has occurred if the drive speed shift or the drive position shift, or both of the drive speed shifts, exceed a predetermined value. 2. The motor control device according to 1. 8. A target speed setting means for setting a target rotation speed, and a motor provided by a speed feedback loop control using a rotation speed detection signal corresponding to the target speed set by the target speed setting means. Motor speed adjusting means for adjusting the rotation speed of the motor, driving state detecting means for detecting the driving state of the motor controlled by the motor speed adjusting means, and detecting by the driving state detecting means A motor drive error determining unit for determining an error in driving the motor based on the drive status information of the motor. A motor control device for monitoring an error while changing the motor speed. 9. The motor whose rotational speed is controlled by a feedback loop control using a rotational speed detection signal in the motor speed adjusting means is an ultrasonic motor based on ultrasonic guidance control. The motor control device according to any one of the preceding claims. 10. The motor control device according to claim 9, wherein a rotation speed detection signal used for controlling the rotation speed of the ultrasonic motor is an encoder output signal. 11. The motor control device according to claim 9, wherein the feedback loop control amount during speed adjustment by the motor speed adjustment means is an ultrasonic pulse width or an ultrasonic frequency or both. 12. The motor drive status information is defined as a drive speed shift and a drive position shift, and if the drive speed shift or the drive position shift or both of them exceed a predetermined specified value, the motor drive error determination is performed. 9. The motor control device according to claim 8, wherein the means determines a drive error. 13. The drive error determination unit changes the drive error determination reference during the entire period or a part of the period during which the motor is being driven during acceleration, constant speed rotation, or deceleration. The motor control device according to any one of the preceding claims. 14. The drive error determination means does not make a drive error determination during a whole or a partial period of the drive state of the motor during acceleration, constant speed rotation, and deceleration. The motor control device according to claim 8. 15. The motor control device according to claim 14, wherein the partial period when the driving state of the motor is accelerating is an initial acceleration start. 16. The motor control device according to claim 14, wherein the partial period when the driving state of the motor is decelerating is an initial stage of deceleration start. 17. An image forming apparatus comprising: the motor control device according to claim 1; and a photosensitive member and / or a transfer member driven by the motor. 18. The image forming apparatus according to claim 17, wherein the photosensitive member driven by the photosensitive member drive motor is a photosensitive drum. 19. The image forming apparatus according to claim 17, wherein the transfer member driven by the transfer member drive motor is a transfer drum. 20. The image forming apparatus according to claim 17, wherein the transfer member driven by the transfer member drive motor is a transfer belt. 21. The image forming apparatus according to claim 20, further comprising the transfer belt, a plurality of the photosensitive members and a plurality of motors for driving the photosensitive members.