JP5031316B2 - Speed control device and image forming apparatus - Google Patents

Description

  The present invention relates to a control technique for correcting a speed fluctuation of a rotating body such as a photosensitive drum.

  In an image forming apparatus such as a copying machine or a printer using an electrophotographic process, it is known that speed fluctuations of a rotating body such as a photosensitive drum cause deterioration of an image.

  Here, an image forming apparatus using an electrophotographic process which is a premise of the present invention will be outlined.

  FIG. 15 shows the configuration of the image forming apparatus.

  15, the image forming apparatus includes four sets of image forming units 1200Y, 1200M, 1200C, and 1200K that form images for each color of Y (yellow), M (magenta), C (cyan), and K (black). Is provided. Each image forming unit includes a photosensitive drum 1201, a developing device 1206, a cleaner 1207, a charger 1208, a primary transfer roller 1209, and a laser optical system 1210, and forms images of different colors on the intermediate transfer belt 1202.

The image forming operation is controlled by the system controller 1220, and color image data supplied from the image reading device 1221 and the image processing device 1222 is supplied to each image forming unit. The photosensitive drum 1201 of each image forming unit is formed with an optical semiconductor layer whose electrical characteristics are changed by light irradiation, and the following (1) to (7) are performed while rotating at a constant speed during the image forming operation. Operates according to steps.
(1) Charging: The photo semiconductor layer of the photosensitive drum 1201 is uniformly charged by the charger 1208.
(2) Laser exposure: An image pattern (electrostatic latent image) is irradiated by the laser optical system 1210 toward the photosensitive drum 1201 (broken line portion B).
(3) Development: A toner is attached to the electrostatic latent image by the developing device 1206.
(4) Primary transfer: The image is transferred onto the intermediate transfer belt 1202 by the primary transfer roller 1209.

The operations (1) to (4) are performed in each image forming unit.
(5) Secondary transfer: The toner image on the intermediate transfer belt 1202 driven by the intermediate transfer roller 1204 is transferred to the recording paper P by the secondary transfer unit 1211.
(6) Fixing: The recording paper P is heated and pressurized by the fixing device 1212 to fix the toner on the recording paper P and then discharged to the outside.
(7) Cleaning: Toner remaining on the photosensitive drum 1201 without being completely transferred onto the intermediate transfer belt 1202 is removed by the drum cleaner 1207. Further, the toner remaining on the intermediate transfer belt 1202 without being completely transferred onto the recording paper P is removed by the belt cleaner 1213.

  The secondary transfer device 1211 and the belt cleaner 1213 described above are separated from the intermediate transfer belt 1202 when the image forming apparatus is in a stopped state.

  The separation of the secondary transfer device is because it is necessary for the user to secure a space for the user to remove the recording paper in the secondary transfer unit when a “paper jam” or the like occurs in the image forming apparatus. Further, the belt cleaner 1213 is separated from the intermediate transfer belt 1202 due to contact with the intermediate transfer belt 1202 for a long time when the unit is stopped when the unit performs cleaning by pressing a cleaning paper such as a web. It is for preventing.

  Then, the secondary transfer device 1211 and the belt cleaner 1213 are attached to the intermediate transfer belt 1202 at the start of the preparatory rotation (pre-rotation) drive for starting the image forming operation.

  Through the above series of operations, the toner images of the image forming units 1200Y, 1200M, 1200C, and 1200K are formed on the intermediate transfer belt 1202 so as to overlap each other. At this time, fluctuations in the rotational speed of the photosensitive drum 1201 and the intermediate transfer roller 1204 cause a so-called “magnification fluctuation” in which the image size of the formed toner image changes, and when a toner image of a certain color is formed. If the moving speed of the intermediate transfer belt 1202 does not match the moving speed of the intermediate transfer belt 1202 when the next toner image is formed, a so-called “color shift” in which each toner image is shifted. appear.

  The main speed fluctuation component of the rotating body that causes such “magnification fluctuation” and “color shift” is a component that exists constantly and has a relatively low frequency. That is, “color misregistration” is caused by uneven rotation of the rotating body where the time integral value (displacement) in the speed fluctuation becomes large, or when the rotating body is driven via the driving gear, the uneven rotation of the gear ratio. is doing.

  In addition, when the rotating body rotates, speed fluctuations of a relatively high frequency component due to gear pitch, natural vibration of the rotating body, load fluctuation applied to the rotating body, and the like occur simultaneously with the rotation unevenness of the low-frequency component described above. These speed fluctuation components mainly cause deterioration of the image called “pitch unevenness”.

Patent Document 1 discloses a technique for correcting the rotation unevenness. This is because the number of pulses of the encoder is determined from the number of teeth of the drive gear, the low frequency component is extracted by simple moving average processing, the low frequency component is corrected by feedforward control (driving pattern is fixed), and the high frequency component is simultaneously corrected. Correction is performed by feedback control.
Japanese Patent Laid-Open No. 10-066373

  In Patent Document 1, low frequency components that cause rotation unevenness and high frequency components that cause pitch unevenness, that is, a frequency band for feedforward control and a frequency band for feedback control cannot be clearly separated. It has the disadvantage of being easy to do.

  In addition, when the above correction control is applied to the rotation control of the photosensitive drum and intermediate transfer roller of the image forming apparatus, load fluctuation due to high voltage application, toner transfer, unit attachment / detachment, etc. is applied to the photosensitive drum and intermediate transfer roller in the image forming operation. Always occurs. For this reason, there is a high possibility that stable rotation drive cannot be performed due to the above-mentioned disadvantages.

  The present invention has been made in view of the above problems, and its object is to realize the suppression of the speed fluctuation of the rotating body and the stable driving for a long time, and the “magnification fluctuation” and “color misregistration” which are image deterioration factors in the image forming apparatus. ", To realize a technology to reduce" pitch unevenness ".

In order to solve the above problems and achieve the object, the present invention includes a rotating body, a drive unit that drives the rotating body at a predetermined rotation ratio, a detection unit that detects the speed of the rotating body, A control unit that calculates a frequency of a drive signal to be output to the drive unit based on the detected speed data and corrects the calculated drive signal to control the drive unit; The unit extracts a first speed fluctuation component having one or more frequency components and a second speed fluctuation component having one or more frequency components from speed data during one rotation of the rotating body. First correction control by feedforward using the correction table of the drive signal to converge the first speed fluctuation component to a target value, and the second speed fluctuation component as a target value. Converge Perform a second correction control by feedback for, in the correction table, the driving signal is fixed to the value at the time the converged to a range in which the first speed fluctuation component is predetermined, the first In the second correction control, feedback control is executed by using a value obtained by correcting the drive signal fixed in the correction table with a correction value calculated from the speed data up to the previous time .

The present invention also provides an image forming apparatus for controlling the rotational speed so that the photosensitive member and the transfer member rub against each other and transferring the electrostatic latent image formed on the photosensitive member to the transfer member. A driving unit that drives the photosensitive member and the transfer member at a predetermined rotation ratio, a detection unit that detects the speeds of the photosensitive member and the transfer member, and a driving signal that is output to the driving unit based on the detected speed data And a controller that controls the drive unit by correcting the calculated drive signal, and the control unit is a speed during one rotation of either the photosensitive member or the transfer member. A first speed fluctuation component is extracted from the data, and a first correction control by feedforward using the correction table of the drive signal is performed to converge the first speed fluctuation component to a target value; Either photoconductor or transfer body From the speed data during one rotation, a speed fluctuation component due to a first frequency is extracted, and feedforward using a correction table of the drive signal is used to converge the first speed fluctuation component to a target value. First correction control is executed, a second speed fluctuation component is extracted from speed data during one rotation of the photosensitive member and the transfer body, and the speed fluctuation component due to the second frequency is converged to a target value. Second correction control based on feedback is executed, and in the correction table, the drive signal is fixed to a value at the time when the first speed fluctuation component converges in a predetermined range, In the correction control, feedback control is executed using a value obtained by correcting the driving signal fixed in the correction table with a correction value calculated from the speed data up to the previous time. That.

  According to the present invention, it is possible to suppress the speed fluctuation of the rotating body and to stably drive for a long time, and to reduce “magnification fluctuation”, “color shift”, and “pitch unevenness” that are image deterioration factors in the image forming apparatus. Can do.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

  The embodiment described below is an example as means for realizing the present invention, and should be appropriately modified or changed according to the configuration and various conditions of the apparatus to which the present invention is applied. It is not limited to the embodiment.

  The present invention can also be realized by supplying a storage medium (or recording medium) storing software program codes for realizing speed fluctuation correction control, which will be described later, to a system or apparatus. In this case, it goes without saying that this can be achieved by reading and executing the program code stored in the storage medium by the computer (or CPU or MPU) of the system or apparatus.

[Speed control device]
FIG. 1 is a block diagram of a speed control apparatus according to an embodiment of the present invention.

  In FIG. 1, reference numeral 101 denotes a rotating body. A drive gear 102 is concentrically attached to the drive shaft of the rotating body 101, and has a predetermined number of teeth Ngear (Ngear is an arbitrary integer) so as to have a reduction ratio designed in advance with respect to the output shaft of the motor 103. Have A motor 103 drives the rotating body 101, and a gear having a predetermined number of teeth Nshaft (Nshaft is an arbitrary integer) meshing with the drive gear 102 is formed on the output shaft. In the present embodiment, the motor 103 is a stepping motor (pulse motor), but it is needless to say that the present invention is not limited to this.

The stepping motor 103 is driven according to a frequency Fstm (Pulse Per Second: time per pulse: hereinafter, pps) of a drive signal (drive pulse) output to the motor. In the stepping motor 103, a rotation angle θ0 [rad] per pulse in the drive signal is defined. The number of pulses Mstm (integer) required for one rotation of the stepping motor 103 is given by the following equation (1).
Mstm = 2π / θ0 (1)
Therefore, the rotation speed Vstm (Rotary Per Minitus: number of rotations per minute: hereinafter, rpm) of the stepping motor 103 is given by the following formula 2.
Vstm = (Fstm / Mstm) × 60 [Second] (2)
For example, in the case of a two-phase stepping motor, the rotation angle per pulse θ0 [rad] = 0.01π [rad]. Therefore, the number of pulses Mstm required per rotation is 200 pulses, and when the driving frequency Fstm = 3000 [pps], the rotational speed Vstm = 900 [rpm].

Therefore, when the rotating gear 101 is rotated by driving the drive gear 102 by the stepping motor 103, the rotational angular velocity (= rotational frequency) Vrot [rpm] of the rotating body 101 is given by the following equation (3).
Vrot = Vstm / (Ngear / Nshaft) = Vstm / Rgear (3)
However, Rgear = Ngear / Nshaft
Here, Rgear is a gear ratio (reduction ratio: arbitrary integer) between the drive gear and the gear formed on the output shaft of the motor. In the above example, when the gear ratio = 10, the rotational angular velocity Vrot of the rotating body = 900/10 = 90 [rpm].

Reference numerals 105 and 106 denote encoders attached concentrically to the end of the drive shaft of the rotating body 101. The encoders 105 and 106 output encoder signals synchronized with the slit pattern input interval of the code wheel 107 having a predetermined number Nwheel of slit patterns having a predetermined width Lwheel [m] designed in advance. In addition, 105 is an encoder A, 106 is an encoder B, and they are set to mutually opposite phases. The reason for this is that the rotational speed of the rotating body 101 usually cancels the influence of the speed fluctuation due to the eccentric component of the rotating body itself and the eccentric component of the code wheel 107. In other words, the angular velocity of the rotating body 101 is often used as a reference, and the purpose of this embodiment is to detect the fluctuation of the angular velocity of the rotating body 101 based on the following formula 4 in the same manner. Here, the angular velocity ωR of the rotating body 101 is given by the following equation 4 when the velocity data VencA detected by the signal from the encoder A105 and the velocity data VencB detected by the signal from the encoder B106 are used.
ωR = (VencA + VencB) / 2 (4)
Reference numeral 108 denotes a home position sensor that detects the reference phase of the rotating body 101. Reference numeral 109 denotes a control unit, which has a CPU 110 that controls the entire drive mechanism by performing a speed correction control calculation described later. Reference numerals 111 and 112 count the slit pattern input interval of the code wheel 107 using the output signal of the reference clock C0 [Hz] (one clock cycle = 1 / C0 [sec]) A105 and encoder B106. A pulse generator 113 outputs a driving pulse for driving the stepping motor 103 to the motor driver 104.

Assuming that the value set by the CPU 110 in the control unit 109 for the pulse generator 113 is Spls (Spls is an arbitrary integer), the frequency Fstm [pps] of the pulse signal output from the pulse generator 113 is given by Given by.
Fstm = CO / Spls (5)
FIG. 2 is a timing chart for explaining a method of detecting the angular velocity fluctuation of the rotating body 101 using the output signals of the encoders A105 and B106.

  In FIG. 2, (a) in the first stage represents the reference clock of the counter A111 (or B112). The second stage (b) represents the home position (HP) input signal of the rotating body 101, and HP is detected at the rising edge. The third stage (c) represents the encoder A105 (or B106) input, and the encoder output signal after the HP input signal is detected is the zeroth input. The fourth stage (d) represents the count number measured with reference to the rising edge of the encoder output signal. The fifth row (e) represents speed data detected by the count number.

When the rising edge of an arbitrary Nth encoder output signal is measured, the CPU 110 acquires the N−1th encoder data e (N−1) _data. Here, the encoder data e (N−1) _data acquired by the CPU 110 is synonymous with “time: Second”, and the N−1th speed data Ve (N−1) is given by the following Equation 6. .
Ve (N-1) = Lwheel [m] / e (N-1) _data [sec] (6)
Here, since Lwheel is a constant value, the angular velocity fluctuation of the rotating body 101 in an arbitrary phase can be detected from the acquired encoder data.

  Next, the angular velocity fluctuation correction control of the rotating body according to the present embodiment will be described.

  FIG. 3 is a flowchart showing the angular velocity fluctuation correction control of the rotating body according to the present embodiment.

  The flow in FIG. 3 is realized by the CPU 110 of the control unit 109 executing a control program stored in the internal memory.

  In FIG. 3, when the driving of the rotating body 101 is started, the angular velocity fluctuation of the rotating body 101 is detected using the encoder data described in FIG. 2 (S201). FIG. 4 shows an angular velocity fluctuation data profile of the rotating body 101 obtained by experiments, where the horizontal axis represents the number of encoder inputs and the vertical axis represents encoder data e (N) _data, which is speed data. FIG. 4 shows a data profile of two rotations of the rotating body, that is, the number of encoder inputs = the number of slits Nwheel × 2 for one rotation of the code wheel. FIG. 5 shows the result of performing an FFT operation (fast Fourier operation) based on the following equation 7 in order to analyze the frequency component ratio of the angular velocity fluctuation of the rotating body 101 from the data profile shown in FIG. ing.

Here, the FFT calculation is outlined (Reference: Introduction to digital signal processing).
X (k) = Σx (n) × exp (-2πknj / N) (7)
Here, x (n) is the acquired n number of sampled data, and corresponds to e (N) _data in the present embodiment. j is an imaginary unit, and j = √-1. Further, k represents a frequency axis unit after frequency component conversion, and X (k) represents a power spectrum (intensity of the corresponding frequency component: arbitrary unit) calculated at the frequency k.

  As shown in FIG. 5, the rotating body 101 rotates with frequency components of various factors, and main frequency components and components calculated therefrom are one rotation unevenness Fr of the rotating body 101 and one of the stepping motor 103. The rotation unevenness Fg0. Further, the component calculated from the one rotation unevenness Fr is Fg0 = Fr × Rgear generated by the gear ratio multiplication of the rotating body 101, the frequency component Fg1 due to the meshing between the drive shaft of the stepping motor 103 and the drive gear 102, the rotation This is the natural vibration component Fp of the body itself.

  In each of the frequency components, one rotation unevenness Fr having a relatively low frequency and one rotation unevenness Fg0 caused by the gear ratio of the rotating body 101 have a time integrated value with respect to the angular velocity fluctuation as described in the background art. For this reason, when the frequency components Fr and Fg0 are generated on the photosensitive drum 1201 and the intermediate transfer roller 1204 as the rotator in the image forming apparatus shown in FIG. 15, this is a main factor of “magnification fluctuation” and “color shift”. . However, these frequency components Fr and Fg0 often show a steady and stable power spectrum when the rotating body 101 is driven.

  For this reason, in the present embodiment, the frequency components Fr and Fg0 are defined as low frequency velocity fluctuation components. Then, a correction drive table for correcting the low-frequency velocity fluctuation component (low-frequency velocity fluctuation component in which a set value to be set for the pulse generator 113 is stored for each phase during which the rotating body 101 rotates once. A generation method and a correction driving method will be described below.

  In S202, a digital signal processing operation is performed on the detected encoder data e (N) _data using the low-frequency component pass filter Filter0 shown in FIG. 6 in order to generate the correction table. The low-frequency component pass filter Filter0 is a digital filter having a cutoff frequency Fc and an attenuation characteristic.

Here, it is assumed that the cutoff frequency Fc of the digital filter shown in FIG.
Fr <Fg0 <Fc <Fg1, Fp (8)
The condition shown in Equation 8 does not limit the present invention.
The digital signal processing operation in S202 is outlined below.

  The digital signal processing operation is a product of detected sampling data (equivalent to encoder data e (N) _data) and a coefficient profile hM of the low-frequency component pass filter Filter0 shown in FIG. Defined as sum operation.

  As shown in FIG. 8, when “current” data is input at the head address of the memory area Data_Original [n] (the same size as the number of filter coefficients) for buffering the detected original encoder data, The product-sum operation according to Equation 9 is executed, and the encoder data Data_FilterPass [n] after the operation using the filter coefficient table is output.

  The filter coefficient values h0 to hM are designed to be “1” in total. Further, as shown in FIG. 7, the filter coefficients are weighted so that the center value becomes the largest, and the weighting coefficients are changed with respect to data at an arbitrary point during signal processing. In other words, by changing the frequency characteristics of the digital filter, a data profile having only the necessary frequency components can be obtained.

  9 shows the result of performing the above filter operation on the detected encoder data shown in FIG. 4, and FIG. 10 shows the result of performing the FFT operation on the encoder data profile obtained by the filter operation shown in FIG. Is shown.

  From the filter calculation results shown in FIGS. 9 and 10, it can be seen that the extraction of the low frequency component and the removal of the high frequency component are performed accurately.

  Then, from the encoder data from which the low frequency component has been extracted, a motor drive pulse is calculated by multiplying the reference speed value by a preset correction gain for each rotation of the rotator 101. It is reflected in the rotation. Thereby, the encoder data of the low frequency component can be converged within a predetermined fluctuation range as a preset target after several rotations.

  FIG. 11 shows a result of an experiment in which speed fluctuation correction is performed using low-frequency component encoder data. In the profile shown in FIG. 11, line C represents the center value of the target speed, line U represents the upper limit value of the target speed, and line L represents the lower limit value of the target speed. In FIG. 11, the speed of the rotating body converges within the range of the upper limit value and the lower limit value after five revolutions of the rotating body. Here, the motor driving pulse of the correction table is fixed, and the rotating body 101 is driven using this correction table (S203), thereby suppressing the speed fluctuation due to the low frequency component and rotating the rotating body stably. be able to. The speed control of the rotating body using the correction table described above is defined as low frequency speed fluctuation component correction control (feed forward control).

  Next, it is determined whether the encoder data detected at any time falls within a preset range in a state where the low-frequency velocity fluctuation component correction control is being executed on the rotating body 101 in S203 (S204). If it is not within the preset range (including the case where the set range is “0”), high-frequency speed fluctuation component correction control (real-time control) described later is executed (S205), and within the preset range. If it is, the feedforward control using the low frequency velocity fluctuation component correction table is continued.

  Here, the high-frequency velocity fluctuation component correction control in S205 will be described.

  FIG. 12 shows the high-frequency speed fluctuation component correction control, and shows the state of the rotating body 101 in time series (sequentially from the arbitrary Nth).

  In FIG. 12, (a) in the first stage represents the motor drive pulse set by the low frequency speed fluctuation component correction table. The second stage (b) represents a motor drive pulse supplied to the motor 103. The third stage (c) represents an encoder input signal by the rotation of the rotating body. The fourth row (d) represents the calculation timing of the high-frequency velocity fluctuation component correction value.

The correction value is calculated and the motor drive pulse is supplied in synchronization with the input of the encoder signal. When the Nth encoder signal is input, the control unit 109 acquires N−1th encoder data e (N−1) _data. If the (N-1) th encoder data is not within the preset range (NO in S204), the high-frequency speed fluctuation component correction value Ch is calculated using the following equation (10).
Ch = (e (N-1) _data-e (std) _data) × Gain × CE (10)
Here, e (std) _data is the reference encoder data calculated from the target speed. Gain is a reflection coefficient when calculating the correction value. CE is a coefficient for converting the correction value into a motor drive pulse.

  The correction value calculation process is performed while the Nth encoder signal is being input, and when the N + 1th encoder signal is input, the value offset from the motor drive pulse in the low frequency speed fluctuation component correction table is supplied as the motor drive pulse. To do. The speed control of the rotating body using the correction value described above is defined as high-frequency speed fluctuation component correction control (feedback control).

  In this embodiment, when the encoder signal exceeds a preset range even once, high-frequency speed fluctuation component correction control is performed. Therefore, theoretically, it is possible to correct the velocity fluctuation component of the same level as the frequency of the encoder input signal, that is, the sampling frequency Fs.

  In addition, when an encoder signal exceeding a preset range is continuously input m (m is an integer) times, by performing the high-frequency speed fluctuation component correction control, the frequency component that the control follows is Fs / m It can be. For this reason, the type of load variation, that is, the followability to various high frequency components can be set relatively easily.

  Furthermore, the control response can be verified by analyzing a speed fluctuation frequency component when a predetermined load fluctuation called a step response characteristic is applied, and verifying a time at which the speed fluctuation of the component converges. .

[Second Embodiment]
Next, a second embodiment in which the above-described speed variation control is applied to control of a rotating body (photosensitive drum and intermediate transfer roller) of an image forming apparatus will be described.

  FIG. 13 shows a configuration in which the speed control apparatus of the first embodiment is applied to an image forming apparatus. In FIG. 13, the same components as those in FIG. 15 are denoted by the same reference numerals and description thereof is omitted.

  In FIG. 13, reference numeral 1223 denotes a speed variation control unit including the encoder A 105, the encoder B 106, the code wheel 107, the HP sensor 108, the stepping motor 103, and the motor driver 104 of the speed control device shown in FIG. 1. The control unit 109 controls the rotation of the photosensitive drum 1201 and the intermediate transfer roller 1204 of each of the image forming units 1200Y, 1200M, 1200C, and 1200K according to a command from the system controller 1220.

  FIG. 14 shows a control sequence of the photosensitive drum and the intermediate transfer roller during the image forming operation by the image forming apparatus shown in FIG.

  In FIG. 14, when the control unit 109 receives an image forming operation start (ON command) from the system controller 1220 (S1301), the control unit 109 starts accelerating the output shaft of the motor 103 and reaches a preset target speed. Drive at high speed (S1302).

  Next, the above-described low frequency speed fluctuation component correction control is executed for the photosensitive drum 1201 and the intermediate transfer roller 1204. Here, the photosensitive drum 1201 and the intermediate transfer roller 1204 are not controlled simultaneously. This is because, in the low-frequency speed fluctuation component correction control, there is a state in which the average speeds of the photosensitive drum 1201 and the intermediate transfer roller 1204 as the rotating bodies rotate differently with respect to the target values in the control transition period. If the photosensitive drum 1201 and the intermediate transfer belt 1202 rotate while being rubbed against each other, an unexpected load fluctuation is caused by the fluctuation of the friction coefficient in the rubbing portion, and the correction table is generated (converged). This is because it takes a long time.

  The control unit 109 first performs correction control on the photosensitive drum 1201 (S1303), and when the correction table on the photosensitive drum 1201 is fixed (S1304), the control unit 109 performs similar correction control on the intermediate transfer roller 1204. Implement (S1305).

  When the speed fluctuations of the photosensitive drum 1201 and the intermediate transfer roller 1204 are stabilized (when each correction table is fixed) (S1306), the control unit 109 starts an image forming sequence in accordance with a command from the system controller 1220 ( S1307). Then, for example, a high voltage necessary for the electrophotographic process is applied to the charger 1208, the developing device 1206, and the primary transfer body 1209.

  At this time, as an example of an operation that greatly varies the load on the photosensitive drum 1201 and the intermediate transfer belt 1202, there is a “wearing” operation (S1308) of the secondary transfer device 1211 and the belt cleaner 1213. After that, since it converges after a predetermined time, there is often no need to follow the high-frequency speed fluctuation component correction control according to this embodiment.

  Therefore, the control unit 109 forms a toner image in the image forming operation after convergence of load fluctuations during the “arrival” operation of the secondary transfer device 1211 and the belt cleaner 1213 (S1310). High frequency speed fluctuation component correction control is executed for the drum 1201 and the intermediate transfer roller 1204 (S1309).

  As described above, by executing the low-frequency velocity fluctuation component correction control and the high-frequency velocity fluctuation component correction control on the photosensitive drum 1201 and the intermediate transfer roller 1204, the “magnification fluctuation” of the toner image formed by the image forming unit. And “color misregistration” and “pitch unevenness” can be reduced, and stabilization of image quality can be realized over a long period of time.

It is a block diagram of the speed control device of an embodiment concerning the present invention. It is a timing chart explaining the method to detect the angular velocity fluctuation | variation of a rotary body using the output signal of an encoder. It is a flowchart which shows the angular velocity fluctuation correction control of the rotary body by this embodiment. It is a figure which shows the angular velocity fluctuation data profile of the rotary body obtained by experiment. It is a figure which shows the FFT calculation (fast Fourier calculation) result of the data profile of FIG. It is a figure which shows the relationship between the FFT calculation result of the data profile of FIG. 5, and the low frequency component passage type filter Filter0. It is a figure which shows the coefficient profile of the low frequency component passage type filter Filter0 shown in FIG. It is a figure which shows the signal processing block of a digital filter. It is a figure which shows the result of having performed the filter calculation with respect to the detection encoder data shown in FIG. It is a figure which shows the result of having performed FFT calculation with respect to the encoder data profile obtained by the filter calculation shown in FIG. It is a figure which shows the experimental result which performed the speed fluctuation correction by the encoder data of the low frequency component. It is a figure which shows high frequency speed fluctuation component correction control. 1 is a diagram illustrating a configuration in which a speed control apparatus according to a first embodiment is applied to an image forming apparatus. 14 is a timing chart showing a control sequence of the photosensitive drum and the intermediate transfer roller during an image forming operation by the image forming apparatus shown in FIG. 1 is a diagram illustrating a configuration of an image forming apparatus using an electrophotographic process which is a premise of the present invention.

Claims (4)

A rotator, a drive unit that drives the rotator at a predetermined rotation ratio, a detection unit that detects the speed of the rotator, and a drive signal that is output to the drive unit based on detected speed data. In a speed control device having a control unit that calculates a frequency, corrects the calculated drive signal, and controls the drive unit,
The control unit obtains a first speed fluctuation component having one or more frequency components and a second speed fluctuation component having one or more frequency components from speed data during one rotation of the rotating body. Execute the process to extract,
First correction control by feedforward using the correction table of the drive signal for converging the first speed fluctuation component to a target value, and feedback for converging the second speed fluctuation component to the target value And performing the second correction control by
In the correction table, the drive signal is fixed to a value at the time when the first speed fluctuation component converges to a predetermined range,
The second correction control performs a feedback control using a value obtained by correcting the driving signal fixed in the correction table with a correction value calculated from speed data up to the previous time. . The second correction control is executed when the speed data exceeds a predetermined value after executing the first correction control,
2. The control unit according to claim 1, wherein the control unit calculates a correction value for correcting the second speed fluctuation component, and controls the driving unit using a driving signal corrected by the correction value. Speed control device.   The speed control apparatus according to claim 1, wherein the control unit performs filtering processing on the speed data to extract the first speed fluctuation component. In the image forming apparatus for controlling the rotational speed so that the photosensitive member and the transfer member rub against each other and transferring the electrostatic latent image formed on the photosensitive member to the transfer member,
A drive unit for driving the photosensitive member and the transfer member at a predetermined rotation ratio;
A detector for detecting the speed of the photosensitive member and the transfer member;
A control unit that calculates the frequency of the drive signal output to the drive unit based on the detected speed data, corrects the calculated drive signal, and controls the drive unit;
The controller extracts a first speed fluctuation component from speed data during one rotation of either the photoconductor or the transfer body, and converges the first speed fluctuation component to a target value. Performing the first correction control by feedforward using the correction table of the drive signal;
The drive signal is used to extract a speed fluctuation component due to a first frequency from speed data during one rotation of the other of the photoconductor and transfer body, and to converge the first speed fluctuation component to a target value. The first correction control by feedforward using the correction table is executed,
Second correction control by feedback for extracting the second speed fluctuation component from the speed data during one rotation of the photosensitive member and the transfer body, and for converging the speed fluctuation component due to the second frequency to the target value. the execution,
In the correction table, the drive signal is fixed to a value at the time when the first speed fluctuation component converges to a predetermined range,
The second correction control performs feedback control using a value obtained by correcting the driving signal fixed in the correction table with a correction value calculated from speed data until the previous time. .

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