JP3196302B2 - Rotating body drive control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in an image forming apparatus such as a color electrophotographic copying machine or a color printer, and controls the driving of a rotating body such as a photosensitive drum and a transfer drum. It is about.

[0002]

2. Description of the Related Art Conventionally, as a technique related to this type of rotating body drive control device, there is one disclosed in, for example, JP-A-63-75759. In the image forming apparatus for forming an image on an image carrier that moves endlessly, the drive control device for the image carrier carries the image carrier through a reduction gear train having an integer ratio of teeth as a mechanism for moving the image carrier. A stepping motor to be driven, a memory storing a pulse generation pattern for canceling a rotation change of one rotation of the gear of the last gear of the gear train for one rotation of the last gear, and a detecting means of a home position of the last gear. A pulse is generated based on the pulse generation pattern when the image carrier is moved, and the stepping motor is driven.

However, in the case of the drive control apparatus for an image carrier according to the above proposal, a pulse generation pattern for canceling the rotation fluctuation of the image carrier is stored in a memory in advance as a fixed pattern, and is stored in this memory. A pulse is generated based on the fixed pulse generation pattern, and a stepping motor is driven by the pulse, thereby preventing rotation fluctuation of the image carrier. Therefore, if the state of the rotational fluctuation of the reduction gear train for driving the image carrier changes due to environmental change such as temperature change or temporal change due to long-term use, the pulse generation pattern for canceling this rotational fluctuation is stored in the memory. Since the fixed pattern is stored in the memory, it is not possible to cope with an unexpected rotation fluctuation due to an environmental change or the like. As a result, it is not possible to sufficiently suppress the rotation fluctuation of the image carrier caused by environmental change or aging change, and the rotation fluctuation remains on the image carrier, so that a color shift or the like occurs in a formed image. there were.

In order to solve the above-mentioned problems, the present applicant has already proposed a rotation control method and apparatus in a multiple transfer apparatus disclosed in Japanese Patent Application Laid-Open No. 2-43574. The rotation control method according to this proposal is based on the transfer roll when a drive motor for driving the transfer roll is previously rotated at a constant angular speed in a multiple transfer device in which a plurality of images are transferred in a multiplex manner onto a common transfer roll. The information on the change in the angular velocity is stored in a storage means, the information on the change in the angular velocity is read from the storage means at the time of transfer, and the angular velocity of the drive motor is changed based on the information.

The rotation control method in the multiple transfer apparatus according to this proposal uses a transfer roll stored in a storage means in advance even if a new rotation fluctuation occurs in the image carrier due to environmental change or aging. When the angular velocity of the drive motor is changed based on this information, the angular velocity can be corrected as a change in the angular velocity, so that it can cope with environmental changes and changes over time. Has become.

[0006]

However, the above-mentioned prior art has the following problems. That is, in the case of the rotation control method in the multiple transfer device according to the proposal of the present applicant, the information on the change in the angular velocity of the transfer roll is stored in the storage means as it is, and the information on the change in the angular velocity is read out from the storage means. Thus, the angular velocity of the drive motor is directly changed based on the information. Therefore, when the change information of the angular velocity of the transfer roll to be stored in the storage unit is increased and the number of divisions of the angular velocity is greatly increased, thereby increasing the accuracy of the rotation control of the transfer roll, the amount of change due to the correction gradually increases. The size of the system becomes a vibration source for the system from the drive motor to the rotation axis of the transfer roll via the gear, and there is a problem that the oscillation may occur or the amplitude of the natural frequency of the system may increase. . In this case, it is necessary to use a high-precision encoder as the encoder for detecting the change information of the angular velocity of the transfer roll in order to increase the precision of the rotation control of the transfer roll, and to increase the cost accordingly. There was also a problem of inviting.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art, and it is an object of the present invention to provide a method for controlling the speed of a rotating body even when the speed of the rotating body is controlled with high accuracy. It is an object of the present invention to provide a drive control device for a rotating body which does not cause oscillation or increase the cost.

[0008]

According to the present invention, there is provided a rotating body drive control device for controlling the driving of a rotating body used in an image forming apparatus, wherein a low-precision first speed detecting means detects a rotation speed of the rotating body. Rotation detection means, used only during the manufacture of the image forming apparatus, high-precision second rotation detection means for detecting the rotation speed of the rotating body, and a driving means for rotating the rotating body at a constant speed Storage means for storing, at the time of driving, rotation speed information detected by the first rotation detection means and the second rotation detection means for each predetermined division section;
During image formation, and detects the rotational speed of the rotating body by said first rotation detection means, reads the rotational speed information of the first rotation detecting means and the second rotation detecting means stored in said storage means, said The second time stored in the storage means
A predetermined number of sections before the rotation speed information of the rotation detection means is detected
Averaged over the FILS and stored in the storage means
Integrated value of the ideal value up to one section ahead of the specified correction operation
And the first rotation detection means read in real time
Detects the calculated value of the difference from the integrated value of rotation speed information up to the section
FILD averaged over a predetermined number of sections before the hour
And the rotation speed of the second rotation detection means stored in the storage means
Is averaged over a predetermined number of sections before detection.
And the rotation of the first rotation detection means stored in the storage means
Average speed information over a predetermined number of sections before detection
Section when the difference data from the detected value is detected from the zero-phase pulse
And a control means for controlling a driving means for rotating and driving the rotating body based on the ΣDIFF integrated up to the above.

As the rotating body, for example, a photosensitive drum is used. However, the rotating body is not limited to this, and the rotating body may be a belt-shaped photosensitive body, a transfer drum, or a transfer for transferring a transfer sheet. Of course, a rotating body such as a belt may be used.

Although the number of the photosensitive drums may be plural, the present invention can be applied to a single photosensitive drum.

Further, as a driving means for driving the rotating body, for example, a stepping motor is used.
In addition, the control can be performed by a DC servo motor or a direct drive motor.

[0012]

According to the present invention, when the image forming apparatus is manufactured, the first rotation detecting means and the second rotation detecting means are attached to the rotating shaft of the rotating body, and the driving means for rotating the rotating body is driven at a constant speed. And stores the rotation speed information detected by the first rotation detection means and the second rotation detection means in the storage means for each predetermined divided section. When the image forming apparatus is used, the rotation speed of the rotating body is detected by the first rotation detection unit, and the rotation speeds of the first rotation detection unit and the second rotation detection unit stored in the storage unit are detected. The control means reads out the information, averages the rotation speed information detected by the first rotation detection means and the rotation speed information of the first rotation detection means and the second rotation detection means stored in the storage means, Based on the averaged rotation speed information, the control unit controls the driving unit that rotationally drives the rotating body. Therefore, the speed information of the rotating body to be stored in the storage means is greatly increased by increasing the number of divided sections. 2
The rotation speed information detected by the rotation detection means is averaged by the control means, and the control is performed based on the averaged rotation speed information. Oscillation and an increase in the amplitude of the natural frequency of the system can be prevented. Also,
The high-accuracy second rotational speed detecting means is used only at the time of manufacturing the image forming apparatus, and the detection information of the second rotational speed detecting means is stored in the storage means and used for correction control. Even when the speed is increased, the cost of the image forming apparatus does not increase.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the illustrated embodiment.

FIG. 2 shows an embodiment of a color image forming apparatus to which the rotating body drive control device according to the present invention is applied.

In FIG. 2, reference numerals 1Y, 1M, 1C, and 1K denote photosensitive drums on which toner images of yellow, magenta, cyan, and black are formed, respectively. 1C and 1K are arranged in parallel at a predetermined interval from each other. After the surfaces of the photosensitive drums 1Y, 1M, 1C and 1K are uniformly charged by the primary chargers 2Y, 2M, 2C and 2K,
The images are sequentially exposed by exposure optical systems 3Y, 3M, 3C, and 3K including a semiconductor laser and a polygon mirror to form an electrostatic latent image. Each of these photosensitive drums 1Y,
The electrostatic latent images formed on the surfaces of 1M, 1C, and 1K are respectively yellow and yellow by developing units 4Y, 4M, 4C, and 4K.
After being developed with magenta, cyan, and black toners to form visible toner images, these visible toner images are neutralized by pre-transfer neutralizers 5Y, 5M, 5C, and 5K.
The images are sequentially transferred onto the transfer paper 10 by the charging of the transfer chargers 6Y, 6M, 6C, and 6K.

The photosensitive drums 1Y, 1M, 1C, 1K
The transfer paper 10 that receives the transfer of the toner image sequentially from the transfer drum 10 is supplied from a paper feed cassette (not shown), and is conveyed while being electrostatically held on the transfer body conveyance belt 12. The sheet is sequentially conveyed to a transfer position located below 1C and 1K. Then, each photosensitive drum 1Y,
The transfer paper 10 onto which the toner images of each color are sequentially transferred from 1M, 1C, and 1K is separated from the transfer body transport belt 12 and transported to the fixing unit 13 by the fixing unit 13. And the color image is fixed.

On the other hand, the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K on which the transfer of the toner images has been completed are subjected to the charge of the post-transfer chargers 7Y, 7M, 7C, and 7K, and are discharged and cleaned. After the residual toner and the like are removed by the devices 8Y, 8M, 8C, and 8K, the erase lamps 9Y,
The charge is removed by 9M, 9C, and 9K to prepare for the next image formation.

FIG. 3 shows a mechanism for rotationally driving the photosensitive drum.

In FIG. 1, reference numerals 1Y, 1M, 1C and 1K denote the respective photosensitive drums. Each of the photosensitive drums 1Y, 1M, 1C and 1K has a drive motor 15 comprising a stepping motor and A first gear 16 fixed to the drive shaft of the drive motor 15, a second gear 17 meshing with the first gear 16, a third gear 18 fixed to the same shaft as the second gear 17, The third gear 18 is rotatably driven by a photoreceptor gear 19 fixed to the rotating shafts of the photoreceptor drums 1Y, 1M, 1C and 1K meshing with each other. In addition, the photosensitive drums 1Y, 1M, 1
A flywheel 30 as an inertial body is attached to each of the rotation shafts C and 1K.

The photosensitive drums 1Y, 1M, 1M
A rotary encoder 21 and a calibration rotary encoder 22 are attached to the rotation shafts of C and 1K. The rotary encoder 21 and the calibration rotary encoder 22 are mounted on the photosensitive drums 1Y, 1M,
This is for detecting the angular velocity of rotation of 1C and 1K. The rotary encoder 21 and the calibration rotary encoder 22 are connected to a control unit 20, and a drive motor 15 is connected to the control unit 20. A relatively low-precision rotary encoder is used as the rotary encoder 21, for example, one that outputs 180 or 360 pulses per rotation. On the other hand, the calibration rotary encoder 2
As 2, a high-precision one that outputs, for example, 10,000 thousands of pulses per rotation is used.
The calibration rotary encoder 22 is attached to the rotating shafts of the photosensitive drums 1Y, 1M, 1C, and 1K only when adjusting the color image forming apparatus before shipment at a factory, for example. When it is removed from the device.

FIG. 1 is a block diagram showing a circuit configuration of the control unit.

In the drawing, reference numeral 23 denotes a photosensitive drum 1Y, 1
M, 1C, and 1K control the CPU, 24 is a PROM that stores programs executed by the CPU 23 and predetermined data, and 25 is the rotary encoder 2
RA that stores the time interval of each divided section, which is data read from the calibration rotary encoder 22 and the like.
M and 21 are photosensitive drums 1Y and 1 at the time of image recording.
A rotary encoder for detecting the rotation speeds of M, 1C and 1K, 22 is a calibration rotary encoder for calibrating the rotary encoder 21 at the time of adjustment before shipment of the apparatus, and 26 is a pulse output from the calibration rotary encoder 22. A pulse counter 27 for dividing the pulse signal output from the pulse oscillator 28 and outputting a drive pulse of a predetermined command frequency, and 29 based on the drive pulse output from the interval counter 27 A drive motor driver for rotating the drive motor 15.

Before the drive control of this embodiment is performed, the drive mechanism for rotating the photosensitive drum includes a drive motor 15 for rotating the photosensitive drums 1Y, 1M, 1C, and 1K.
Even if the command frequency to the photosensitive drum 1 is kept constant,
Y, 1M, 1C, 1K eccentricity of the rotating shaft and the drive gear 1
Due to a meshing error of 6, 17, 18, and 19, the rotation of the photoconductor drums 1Y, 1M, 1C, and 1K causes a position error (a rotation angular velocity fluctuation in the photoconductor shaft portion) as shown in FIG. Which represents the deviation from the ideal position).

The relationship between the fluctuation of the rotational angular velocity and the position error when the photosensitive drum rotates is generally expressed by the following equation (1). The integration of the position error X (t) is performed from 0 to t.

[0025]

(Equation 1)

FIG. 5 shows the result of the fast Fourier transform (FFT) analysis of the angular velocity of the photosensitive drum.

As described above, before the drive control of the photosensitive drum is performed, the frequency f _i and the system resonance frequency f _{n are controlled.}
In addition, a high amplitude level peak appears near a high frequency caused by the driving gear, and color shift or color unevenness occurs in a color image sequentially transferred on the transfer paper 10 due to the rotation fluctuation of the angular velocity of the photosensitive drum. Appears.

The rotation fluctuation of the angular velocity of the photosensitive drum is
Low-frequency fluctuations or the eccentricity component is generated by a rotation of the photosensitive drum as one period, variation of the intermediate frequency corresponding to the resonant frequency f _n of the system, or the like variations in the high-frequency component due to the drive gear.

By the way, in this embodiment, each photosensitive drum 1Y, 1M, 1C,
A rotary encoder 22 for calibration is attached to the rotation shaft of 1K in addition to the rotary encoder 21, and the following correction table creation operation is performed. here,
The operation of creating a correction table for the photosensitive drum 1Y will be described, but the same operation is performed for the other photosensitive drums 1M, 1C, and 1K.

First, in order to create a correction table for the photosensitive drum 1Y, the photosensitive drum 1Y is driven to rotate at a constant angular velocity. In other words, as shown in FIG. 1, the output pulse S _OSC of the pulse oscillator 28 is _divided by the interval counter 27 into a drive pulse S _DP having a predetermined frequency in the drive motor 15 for rotationally driving the photosensitive drum 1Y. Supplied. The frequency of the driving pulse S _DP is P
It is stored in advance in the ROM 24 as the standard frequency f _S. CPU23 reads the data in the standard frequency f _S from PROM24, loaded into the interval counter 27 as the preset data S _PS. Interval counter 27 counts the pulses output from the pulse oscillator 28 outputs a drive pulse S _DP whenever the count value of the pulse reaches the preset data S _PS. The photosensitive drum 1Y is connected to a drive motor driver 2
9 is supplied to the drive motor 15 via the predetermined frequency f _S
Is rotationally driven by the driving pulse S _DP of

Then, with the rotation of the photosensitive drum 1Y, the rotary encoder 21 and the calibration rotary encoder 22 attached to the rotating shaft of the photosensitive drum 1Y output the signals shown in FIGS. d) As shown in (e), the output pulses S1 _RE and S2 _RE and the zero-phase pulse S
1 ₀ is output to the CPU 23. At this time, the output pulse S2 _RE of the rotary encoder 22 for calibration is output to the CPU 23 via the pulse counter 26. The output pulses S1 _RE and S2 _RE are output from the rotary encoder 2
1 and a signal output each time the calibration rotary encoder 22 rotates by a predetermined angle. Further, the zero phase pulse S1 ₀ is for the rotary encoder 21 is output at the reference position upon rotation, both encoders 2
The reference positions 1 and 22 are set to the same position.
Incidentally, the pulse counter 26, as shown in FIG. 6 (c), divides the output pulse S2 _RE output from the rotary encoder 22 for calibration, C as an interrupt signal S _INT
The data is output to the PU 23.

When the correction table is created, the fluctuation of the rotation of the photosensitive drum 1Y is changed by the rotary encoder 2.
1 and the rotary encoder 22 for calibration. Pulses S1 _RE and S2 output from the rotary encoder 21 and the calibration rotary encoder 22
_RE is output at almost constant intervals unless the rotation of the photosensitive drum 1Y is changed, and the number of pulses output in a predetermined divided section is always constant. However, if the rotation of the photosensitive drum 1Y fluctuates, the output intervals of the pulses S1 _RE and S2 _RE output from the rotary encoder 21 and the calibration rotary encoder 22 change.
As shown in (1), the time interval output in a predetermined divided section differs depending on each divided section.

For this reason, every time an interrupt signal S _INT obtained by _dividing the output pulse S 2 _RE of the calibration rotary encoder 22 by the pulse counter 26 is input, the CPU 23 drives the interval counter 27 b driven by the output of the pulse oscillator 28. Is read and stored in the RAM 25 as shown in FIG. That is, the CPU 23
It is zero phase pulse S1 ₀ from the rotary encoder 21
Is input, when the first interrupt signal _SINT causes an interrupt, the count value of the interval counter 27b is read and the interval T corresponding to the first interval is read.
_It is stored in the RAM 25 as ₁ . Then, when the interrupt signal S _INT corresponding to the next section is inputted, the reading is performed in the same manner, the difference from the count value of the previously read interval counter 27b is calculated, and the interval T _{2 of the} section is measured. It is stored in the RAM 25. This operation is repeated for one cycle of the calibration rotary encoder 22.

[0034] At this time, the zero-phase pulse S1 ₀ of the rotary encoder 21 is supplied to the CPU 23, as a reference the zero phase pulse S1 ₀ initial value of the address is C
The interval T _(N) of each divided section is set by the PU 23 and thereafter, by adding an address by a fixed value and specifying the address for each section, that is, each time the interrupt signal S _INT is input, the RAM 25. Is stored in

Each time the output pulse S1 _RE of the rotary encoder 21 is input, the CPU 23 outputs an interval counter 27 driven by the output of the pulse oscillator 28.
b, and reads the count value in the RAM as shown in FIG.
25. That is, the CPU 23 controls the rotary encoder 2 similarly to the calibration rotary encoder 22.
After the zero-phase pulse S1 ₀ is input from 1 and the next output pulse S1 _RE is input, the interval counter 2
The count value of 7b is read and stored in the RAM 25 as an interval T _L1 corresponding to the first section. Then, when the output pulse S1 _RE corresponding to the next section is input, the pulse is read in the same manner, the difference from the count value of the previously read interval counter 27b is calculated, and the interval T _{L2 of the} section is measured. Is stored in This operation is also repeated for one cycle of the rotary encoder 21.

At this time, the calibration rotary encoder 22
There number of interrupt signals S _INT output during one rotation is set equal to the number of output pulses S1 _RE to be printed between the rotary encoder 21 rotates once. That is,
The divided sections for counting the time intervals of the pulses S2 _RE and S1 _RE output from the calibration rotary encoder 22 and the rotary encoder 21 are both set to the same number.

The interval counter 27b
Is driven by the output S _OSC of a constant frequency from the pulse oscillator 28, the count value of the interval counter 27b indicates the elapsed time.

Next, the CPU 23 calculates a difference C _(N) = _{TL (N)} between the interval T of the divided section of the rotary encoder 22 for calibration stored in the RAM 25 and the interval _TL of the divided section of the rotary encoder 21. −T _(N) is calculated for each divided section, and the calculation result C _(N) is stored in the RAM 25 for each divided section, as shown in FIG.

Thus, the operation of creating the correction table is completed. The work of creating this correction table is, as described above,
This is performed when adjusting the color image forming apparatus in the factory.

When the user uses the color image forming apparatus, the CPU 23 operates the rotary encoder 21 based on the following correction formula during the image forming operation.
Is corrected, and the photosensitive drum is rotationally driven.

[0041]

(Equation 2)

The correction equation is not limited to the equation (2), and a correction equation as shown in the following equation (3) may be used.

[0043]

(Equation 3)

Here, f _n ; interval frequency after correction f _s ; standard frequency FILS previously stored in PROM 24; interval value T _(N) of rotary encoder 22 for calibration stored in RAM 25 as a correction table; The interval value after averaging over the section from the section (N) to the previous m, ie, FILS = 1 / m (T _{(N-m + 1)} + T _{(N-m + 2)} + T _{(N -m + 3)} +... + T _(N-1) + T _(N) ) FILD; ideal value ΣT _ID one section ahead in correction operation stored in advance in PROM 24 and interval value の T of rotary encoder 22 read in real time. ' _(N) and the value obtained by averaging the calculated value of the difference (ΣT _ID -ΣT' _(N) ) from the section (N) to the preceding m section, ie, FILD = 1 / m ｛(ΣT _ID -ΣT ' _{(N-m + 1)} ) + (ΣT _ID -ΣT' _{(N-m + 2)} ) + (ΣT _{I D−} {T ′ _{(N−m + 3)} ) +... + ({T _{ID −} {T ′ _(N−1) ) + (ΔT _{ID −} {T ′ _(N) )} ΣDIFF; Rotary encoder 21 and rotary encoder for calibration After averaging the respective interval values T _{L (N)} and T _(N) with the interval 22 from the section (N) to the preceding section m as in FILS, the difference data (FILS) of these values is obtained. −FILS) from the zero-phase pulse, that is, ΣDIFF = Σ (FILS−FILS) 0 to _N = Σ ｛1 / m ( _{TL (N−m + 1)} + _{TL (N−m + 2)} + _{TL (N-m + 3)} + ... + _{TL (N-1)} + _{TL (N)} )-1 / m (T _{(N-m + 1)} + T _{(N-m + 2)} + T _{(N-m + 3)} +... + T _(N-1) + T _(N) )｝ (Σ is from 0 to _N ) T _ID ; Ideal calculated value of one section stored in the PROM 24 in advance, that is, the photoconductor In an ideal condition where there is no rotational fluctuation in the rotation axis of the drum, Baru value alpha; constants previously stored feedforward portion PROM24 β; PROM24 constants prestored feedback portion. Each of the above equations employs averaging. However, depending on the system, weighting may be used to change the coefficient of each section.

It should be noted that, according to experimental data and logic analysis using only feedforward control, when α = 1, there is no response delay, so that the value known in advance can be corrected by that amount, and the correction effect is the best. Therefore, when α = 1 is substituted into the equation (1) (α is selected to be close to 1 depending on the system), the following equation 4 is obtained.

[0046]

(Equation 4)

In this embodiment, Equation 4 is used as a correction equation.

In the above configuration, the drive control of the photosensitive drum is performed in the following manner in the drive control apparatus for the rotating body according to this embodiment. That is, in order to form a color image in the color image forming apparatus, as shown in FIG. 2, the photosensitive drums 1Y, 1M, 1C, and 1K are rotationally driven, and these photosensitive drums 1Y, 1M, 1C, 1K
, Toner images of each color of yellow, magenta, cyan, and black are formed on the surface of. At this time, the photosensitive drum 1
The rotation states of Y, 1M, 1C, and 1K are controlled as follows.

When starting the formation of a color image, the CP
U23, as shown in FIG. 1, drives the drive motor 15 in the normal frequency f _s, the photoreceptor drums 1Y, 1M, 1
C and 1K are rotated. And the rotor encoder 2
After detecting the zero phase pulse S1 ₀ of 1, the correction and the interval value T table stored _(N), based on the output from the rotary encoder 22 measured interval value T _(N) in each section , And calculates the correction frequency f _n for the next section (N + 1), and outputs it to the drive motor 15.

The correction of the driving frequency based on the equation (4) is as follows.
It is always performed, but may be performed at a predetermined time as needed.

The CPU 23 outputs the corrected data of the drive frequency f _n to the interval counter 27, and the interval counter 27
Counts the pulses output from the count value of the pulse to output a driving pulse S _DP every time reaches the value corresponding to the driving frequency f _n of the corrected. As a result, the photosensitive drum 1Y is driven to rotate by a drive pulse S _DP drive frequency f _n of the corrected to be supplied to the drive motor 15 via the drive motor driver 29.

If there is no fluctuation in the rotation of the photosensitive drum 1Y, FILS, FILD and Σ
Each value of DIFF is, the FILS and FILD is T _ID,
Since ΣDIFF becomes 0, the expression 4, next to f _n = f _s, of course, the drive frequency f _n of the corrected is equal to the standard frequency f _s.

Next, when the interval value of the correction table for the K-th section to be corrected is long, that is, when the angular velocity of the photosensitive drum 1Y when the drive motor 15 is rotated at a constant angular velocity is the K-th section, If it is slow, because the interval value T of the section _'(K) is greater than T _ID, the correction frequency f _n increases as follows. Since the value of T ' _(K) is read in real time, it is not exactly known. That is, in the correction equation 4, the values of FILS, FILD, and $ DIFF are
It looks like this:

FILS is 1 / m (T _{(N−m + 1)} + T
_{(N-m + 2)} + T _{(N-m + 3)} + ... + T _(N-1) + T _(N-1) + T
_(N) ), so it does not change . FILD is 1
/ M ｛(ΣT _ID -ΣT ' _{(N-m + 1)} ) + (ΣT _ID -ΣT'
_{(N-m + 2)} ) + (ΣT _ID −ΣT ' _{(N-m + 3)} ) + ... + (ΣT
Because it is _{ID -ΣT '(N-1)} ) + (ΣT ID -ΣT' (N))}, it is close to T _ID becomes smaller than T _ID. Further, ΣDIFF is Σ ｛1 / m ( _{TL (N-m + 1)} + T
_{L (N-m + 2)} + _{TL (N-m + 3)} + ... + _{TL (N-1)} + _{TL (N)} )-1 /
m (T _{(N-m + 1)} + T _{(N-m + 2)} + T _{(N-m + 3)} + ... + T
_(N-1) + T _(N) )｝, the value is set to 0 if the interval values of the rotary encoders 21 and 22 are equal, and to the value of minus if the interval value of the calibration rotary encoder 22 is larger. If the interval value is larger, it will be positive,
It is a small value close to zero.

[0055] Therefore, the value of Oite number 4 'expression before deploying correction equation Eq. _{4, T ID / (FILD-ΣDIFF} ) is close to 1 becomes a value larger than 1.

The value of β in the correction formula (2) is set as appropriate.

As a result, the value of f _n in equation (4) is f
_s become a value greater than, the correction frequency f _n increases. Thereby, the photosensitive drum 1 driven by the drive motor 15
The angular speed of the rotation of Y is controlled to be constant, and the peripheral speed of the photosensitive drum 1Y is constant.

In addition, due to a change over time, a change in temperature, and the like,
Expansion and contraction of the shape and dimensions affect the runout of the gear tooth space or the total pitch meshing error, thereby changing the eccentric component. Due to this change over time and temperature, K
When the angular velocity of the K-th section increases, that is, when the interval value of the correction table of the K-th section to be corrected is short, the interval value T 'of that section is used.
_{Since (K)} becomes smaller than T _ID , the correction frequency f _n becomes lower as follows. That is, in the four correction equations, the values of FILS, FILD, and $ DIFF are as follows.

The FILS is 1 / m (T _{(N−m + 1)} + T
_{(N-m + 2)} + T _{(N-m + 3)} + ... + T _(N-1) + T _(N-1) + T
_(N) ), so it does not change . FILD is 1
/ M ｛(ΣT _ID -ΣT ' _{(N-m + 1)} ) + (ΣT _ID -ΣT'
_{(N-m + 2)} ) + (ΣT _ID −ΣT ' _{(N-m + 3)} ) + ... + (ΣT
Because it is _{ID -ΣT '(N-1)} ) + (ΣT ID -ΣT' (N))}, it is close to T _ID value larger than T _ID. Further, ΣDIFF is Σ ｛1 / m ( _{TL (N-m + 1)} + T
_{L (N-m + 2)} + _{TL (N-m + 3)} + ... + _{TL (N-1)} + _{TL (N)} )-1 /
m (T _{(N-m + 1)} + T _{(N-m + 2)} + T _{(N-m + 3)} + ... + T
_(N-1) + T _(N) )｝, the value is set to 0 if the interval values of the rotary encoders 21 and 22 are equal, and to the value of minus if the interval value of the calibration rotary encoder 22 is larger. If the interval value is larger, it will be positive,
It is a small value close to zero.

[0060] Therefore, the value of Oite number 4 'expression before deploying correction equation Eq. _{4, T ID / (FILD-ΣDIFF} ) is close to 1 the value smaller than 1.

As a result, the value of f _n in equation (4) is f
_s becomes a smaller value than the correction frequency f _n is low. Thereby, the photosensitive drum 1 driven by the drive motor 15
The angular speed of the rotation of Y is controlled to be constant, and the peripheral speed of the photosensitive drum 1Y is constant.

As described above, according to the present embodiment, not only can the change in the angular velocity of the photosensitive drum unique to each image forming apparatus be corrected, but also the dynamic angular velocity caused by aging, temperature change, etc. Changes can also be corrected.

Moreover, the rotary encoders 21 and 22
Are used for correction after averaging by the CPU 23.
Even if the number of divisions of the angular velocity of the photosensitive drum angular velocity change information stored in the RAM 25 is greatly increased, the interval values output from the rotary encoders 21 and 22 are averaged, and the amount of change due to correction becomes large. Thus, it becomes a vibration source for the system from the drive motor 15 to the rotating shaft of the photosensitive drum via the gear, and it is possible to prevent the possibility of oscillation or an increase in the amplitude of the natural frequency of the system.

The rotary encoder 22 for calibration is used only at the time of adjustment at the factory, and is removed from the color image forming apparatus at the time of shipment from the factory, so that the cost of the color image forming apparatus is increased without increasing the cost. Accuracy can be controlled.

As a result, the four photosensitive drums 1Y, 1Y
The speed of each of the transfer units M, 1C, and 1K becomes constant, and the displacement between the transfer units can be reduced. For example, the position error Δx after the correction becomes very small as shown in FIG.

This position error is measured by a measuring device based on the output of the rotary encoder 21 by the method described below.

That is, the output of the rotary encoder 21 is F / V converted, A / D converted, and the digital value is stored at an appropriate sampling period. Then, the digital values stored in the memory are averaged, and a difference between each digital value and the average value is obtained. Since this difference is a speed difference, the position error is obtained by time integration of the difference.

Further, in this embodiment, since the flywheels 30 as the inertial bodies are respectively mounted on the rotating shafts of the photosensitive drums 1Y, 1M, 1C and 1K, the height is increased by gear teeth. It is possible to prevent the frequency component from fluctuating, and to prevent color unevenness from occurring in the image.

That is, the fluctuation of these high frequency components can be suppressed by optimally selecting the flywheel 30 as the inertial body.

It has been found that when the size of the flywheel 30 (moment of inertia J _L ) is within the following range, the high-frequency component can be reduced and the correction control works effectively. J _L ≦ 0.5Kg ・ cm ・ s ²

FIG. 12 shows the photosensitive drums 1Y, 1M, 1C, 1
FIG. 13 shows a case where the flywheel 30 of J _L = 0.25 Kg · cm · s ² is attached to the rotation axis of K, and FIG. 13 shows the flywheel 30 attached to the rotation axis of the photosensitive drums 1Y, 1M, 1C and 1K. No case is shown. As is apparent from these figures, the photosensitive drums 1Y, 1M, 1C, 1
By attaching the flywheel 30 to the K rotation shaft, high-frequency components near 100 Hz can be reduced.

By combining the above methods, the position error and the FFT analysis result due to the fluctuation of the rotational angular velocity at the shaft of the photosensitive drum are as shown in FIGS. 10 and 11.
It can be seen that the rotation fluctuation can be kept very small.

[0073]

[0074]

The present invention has the above configuration and operation. Even when the speed control of the rotating body is performed with high accuracy, the rotating body does not generate oscillation or increase the cost. A body drive control can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a rotating body drive control device according to the present invention.

FIG. 2 is a configuration diagram illustrating an image forming apparatus to which the rotating body drive control device according to the present invention is applied.

FIG. 3 is a configuration diagram showing a drive system.

FIG. 4 is a graph showing rotation fluctuation of a rotating body.

FIG. 5 is a graph showing the relationship between the frequency of rotation fluctuation and the amplitude level.

FIGS. 6A to 6E are timing charts each showing an operation of the control circuit.

FIG. 7 is a diagram showing data.

FIG. 8 is a diagram showing data.

FIG. 9 is a diagram showing data.

FIG. 10 is a graph showing rotation fluctuation of a rotating body.

FIG. 11 is a graph showing the relationship between the frequency of rotation fluctuation and the amplitude level.

FIG. 12 is a graph showing the relationship between the frequency of rotation fluctuation and the amplitude level.

FIG. 13 is a graph showing the relationship between the frequency of rotation fluctuation and the amplitude level.

[Description of Signs] 21 rotary encoder, 22 rotary encoder for calibration, 23 CPU, 24 PROM, 25 R
AM, 26 pulse counter, 27 interval counter, 29 drive motor driver.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kibun Sato 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd. (56) References JP-A-61-266086 (JP, A) JP-A-1-270784 (JP, A) JP-A-2-43574 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02P 5/00 G03G 15/01 H02P 8/14

Claims (1)

(57) [Claims] An image forming apparatus comprising: a rotating body drive control device for controlling a rotating body used in an image forming apparatus; a low-precision first rotation detecting means for detecting a rotating speed of the rotating body; High-accuracy second rotation detection means that is used only during the manufacture of the device and detects the rotation speed of the rotating body;
When the driving means for rotating the rotating body is driven at a constant speed, the rotation speed information detected by the first rotation detecting means and the second rotation detecting means is stored for each predetermined divided section. Means for detecting the rotation speed of the rotating body by the first rotation detection means at the time of image formation, and detecting the rotation speed information of the first rotation detection means and the second rotation detection means stored in the storage means. Read, said memory
The rotation speed information of the second rotation detecting means stored in the means is
FIL averaged over a predetermined number of sections before detection
S and one section at the time of the correction operation stored in the storage means.
Loaded in real time with the integrated value of the ideal value up to
Product of rotation speed information up to the section of the first rotation detection means
The calculated value of the difference from the calculated value is passed over a predetermined number of sections before detection.
And the second stored in the storage means.
A predetermined number of times before the rotation speed information
The value averaged over the interval and the value stored in the storage means
A predetermined number before the rotation speed information of the first rotation detecting means is detected.
The difference data with the value averaged over the section of
Based on ＦＦDIFF integrated from pulse to detection interval
And a control means for controlling a driving means for rotating and driving the rotating body.