JP2022131328A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that appropriately sets the peripheral lengths of photoreceptor drums and a transfer drive roller to separate their rotational phases with a simple arithmetic processing, and performs control considering the period of unevenness in speed.SOLUTION: An image forming apparatus 1 comprises: photoreceptor drums 13; an intermediate transfer belt 21; a transfer drive roller 22; a driving unit 51; a control unit 54a; a rotation position sensor that detects the rotational positions of the photoreceptor drums 13 and the transfer drive roller 22; an image detection sensor 43 that detects toner images; and an operation unit 54b that calculates drum speed variation signals in the photoreceptor drums 13 and a roller speed variation signal in the transfer drive roller 22. The peripheral length of the photoreceptor drums 13 and the peripheral length of the transfer drive roller 22 are set such that one of the quotients of both peripheral lengths divided by their least common multiple is an even number and the other is an odd number.SELECTED DRAWING: Figure 3

Description

The present invention relates to an image forming apparatus having an intermediate transfer belt onto which toner images are transferred.

2. Description of the Related Art Currently, in an electrophotographic image forming apparatus, a toner image is transferred from a photosensitive drum onto a sheet of paper via an intermediate transfer belt. Here, the photosensitive drums and the intermediate transfer belt are rotated at a constant speed so as to avoid problems such as color misregistration. rice field. Therefore, in order to eliminate color misregistration, it has been proposed to correct speed unevenness during image formation (see, for example, Japanese Laid-Open Patent Publication Nos. 2002-200000 and 2002-300002).

JP 2006-171312 A JP 2016-212307 A

The image forming apparatus disclosed in Patent Document 1 controls a driving roller that drives a belt, a driven roller that is driven to rotate in contact with the belt, a detection object provided on the outer periphery of the driven roller, and the conveying speed of the belt. The outer circumference of the driving roller is set to an even multiple of the outer circumference of the driven roller, and control is performed so as to cancel out the velocity component due to the eccentricity of the driving roller.

In the image forming apparatus described above, after obtaining the angular velocity of the driven roller from the detection result of the detected object, the velocity component due to the eccentricity of the driving roller is extracted by, for example, integrating changes in the angular velocity accompanying rotation. are processing.

The image forming apparatus described in Patent Document 2 includes a photoreceptor, an intermediate transfer belt on which a toner image is transferred from the photoreceptor, a transfer driving roller around which the intermediate transfer belt is stretched, and driving of the photoreceptor and the transfer driving roller. and an adjustment detection unit that detects the adjustment pattern on the intermediate transfer belt. feedback control.

In the image forming apparatus described above, there is a problem that the operation of separating the phase relationship between the photoreceptor and the transfer driving roller is complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems. An object of the present invention is to provide an image forming apparatus that performs control in consideration of the cycle of speed unevenness.

An image forming apparatus according to the present invention drives a plurality of photosensitive drums having the same circumferential length, an intermediate transfer belt onto which toner images formed on the plurality of photosensitive drums are transferred, and the suspended intermediate transfer belt. a driving roller, a driving unit that transmits driving forces to the photosensitive drum and the driving roller, respectively, a control unit that controls driving conditions in the driving unit, and each of the photosensitive drum and the driving roller a rotational position sensor for detecting a rotational position; an image detection sensor for detecting a toner image transferred onto the intermediate transfer belt; and a roller speed fluctuation signal at the drive roller, wherein the peripheral length of the photosensitive drum and the peripheral length of the drive roller are , the quotient of the least common multiple of both is set so that one is an even number and the other is an odd number. , the image detection sensor detects a speed unevenness detection image formed at a constant pitch and outputs a pitch detection signal, and the computing unit detects from the pitch detection signal the speed variation at the coincident lap length. The first half and the second half are extracted, and the drum speed fluctuation signal and the roller speed fluctuation signal are calculated by a predetermined calculation using the first half and the latter half.

In the image forming apparatus according to the present invention, the calculation section may calculate the drum speed fluctuation signal and the roller speed fluctuation signal by adding and subtracting the former half and the latter half.

In the image forming apparatus according to the present invention, when one of the circumferential length of the photosensitive drum and the circumferential length of the drive roller is A, the other is B, and two arbitrary integers are α and β, The circumferential length of the photosensitive drum and the circumferential length of the drive roller may satisfy the relationship Aβ=B(α+0.5).

In the image forming apparatus according to the present invention, the pitch detection signal records the time points at which the speed non-uniformity detection images are detected, and the computing unit interpolates between the time points at which the speed non-uniformity detection images are detected. The drum speed fluctuation signal and the roller speed fluctuation signal may be calculated.

In the image forming apparatus according to the present invention, the reference time at which the speed unevenness detection image is detected for the first time and the ideal detection timing calculated from the reference time based on the pitch to be formed are set. The calculation unit may be configured to calculate a difference between the time when the speed unevenness detection image is detected and the ideal detection timing.

In the image forming apparatus according to the present invention, the control section may correct the drive conditions based on the drum speed fluctuation signal and the roller speed fluctuation signal.

In the image forming apparatus according to the aspect of the invention, the calculation unit generates an antiphase signal obtained by inverting the phase of at least one of the drum speed fluctuation signal and the roller speed fluctuation signal, and the control unit generates the A configuration may be adopted in which the drive condition in which the speed fluctuation is canceled is set by the opposite phase signal for the target drive unit that generated the opposite phase signal.

In the image forming apparatus according to the aspect of the invention, the control section may correct the driving condition according to the rotational positions of the photosensitive drum and the driving roller.

In the image forming apparatus according to the present invention, the drum speed fluctuation signal is associated with the rotational position of the photosensitive drum, the roller speed fluctuation signal is associated with the rotational position of the drive roller, and the control unit The driving condition may be adjusted according to the rotational positions of the photosensitive drum and the driving roller when the positional relationship between the rotational position of the photosensitive drum and the rotational position of the driving roller changes.

In the image forming apparatus according to the aspect of the invention, a plurality of driving conditions are set according to the rotational speeds of the photosensitive drum and the driving roller, and the computing unit calculates the driving conditions based on the plurality of driving conditions. The drum speed fluctuation signal and the roller speed fluctuation signal may be calculated.

According to the present invention, by setting the circumferential lengths of the photosensitive drum and the driving roller so that the lengths of the rotations are the same in a specific rotation, the speed unevenness due to the eccentricity is configured to periodically fluctuate. can be done. Then, by performing calculations in consideration of the cycle of the speed unevenness, it is possible to separate and extract speed fluctuation components between the photosensitive drum and the drive roller.

1 is a schematic side view of an image forming apparatus according to an embodiment of the invention; FIG. FIG. 2 is an explanatory diagram of a main part extracting and showing the vicinity of an intermediate transfer belt device; 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention; FIG. FIG. 5 is an explanatory diagram showing detection results of an image detection sensor; FIG. 4 is an explanatory diagram showing an example of a pitch detection signal; FIG. 5 is an explanatory diagram showing the positional relationship between a portion of a pitch detection signal, a photoreceptor drum, and a transfer drive roller; FIG. 4 is an explanatory diagram showing the relationship between the first and second halves of a pitch detection signal and a drum speed fluctuation signal; FIG. 4 is an explanatory diagram showing the relationship between the former half and latter half of the pitch detection signal and the roller speed fluctuation signal;

An image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic side view of an image forming apparatus according to an embodiment of the invention.

The image forming apparatus 1 includes an image forming section 1a that forms multicolor and monochromatic images on a predetermined sheet of paper in accordance with image data transmitted from the outside.

The image forming section 1a includes an exposure device 11, a developing device 12, a photosensitive drum 13, a cleaning device 14, a charger 15, an intermediate transfer belt device 16, a fixing device 17, a paper feed tray 18, a paper discharge tray 19, and a paper feeder. It is configured to include the device 20 .

The image data handled by the image forming apparatus 1 corresponds to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y). Accordingly, four developing devices 12, photosensitive drums 13, chargers 15, and cleaning devices 14 are provided so as to form four types of latent images corresponding to the respective colors, respectively black, cyan, magenta, and yellow. , and these constitute four image stations.

The photosensitive drum 13 is arranged substantially in the center of the image forming section 1a of the image forming apparatus 1, and is rotationally driven by a connected drive section 51 (see FIG. 3 described later). The charger 15 uniformly charges the surface of the photosensitive drum 13 to a predetermined potential. The exposure device 11 exposes the surface of the photosensitive drum 13 to form an electrostatic latent image. The developing device 12 develops the electrostatic latent image on the surface of the photoreceptor drum 13 to form a toner image on the surface of the photoreceptor drum 13 . Through the series of operations described above, a toner image of each color is formed on the surface of each photoreceptor drum 13 , and the toner image on the photoreceptor drum 13 is transferred onto the intermediate transfer belt 21 . The cleaner device 14 removes and collects residual toner on the surface of the photosensitive drum 13 after development and image transfer.

The intermediate transfer belt device 16 is arranged above the photosensitive drum 13 and includes an intermediate transfer belt 21 , a transfer driving roller 22 (an example of a driving roller), a transfer driven roller 23 , a transfer pressure contact roller 24 , and an intermediate transfer belt cleaning device 25 . It has Four transfer pressure contact rollers 24 are provided corresponding to the image stations of each color for YMCK.

The intermediate transfer belt 21 is stretched and supported by a transfer driving roller 22 , a transfer driven roller 23 , and a transfer pressing roller 24 . The transfer drive roller 22 is connected to the drive unit 51 and rotationally driven to rotate the intermediate transfer belt 21 in the arrow C direction. An intermediate transfer belt cleaning device 25 removes and collects residual toner from the intermediate transfer belt 21 , and the toner images of the respective colors formed on the surfaces of the photosensitive drums 13 are sequentially transferred and superimposed to form the intermediate transfer belt 21 . A color toner image is formed on the surface. Note that the operation of the intermediate transfer belt device 16 will be described in detail with reference to FIG. 2, which will be described later.

The image forming section 1a further includes a secondary transfer device 27 including a transfer roller 27a. A nip area is formed between the transfer roller 27a and the intermediate transfer belt 21, and the paper P transported through the paper transport path S is sandwiched in the nip area and transported. The toner image on the surface of the intermediate transfer belt 21 is transferred to the paper P while passing through the nip area.

The paper feed tray 18 is a tray for storing paper P used for image formation, and is provided below the exposure device 11 . Further, the paper discharge tray 19 is provided on the upper side of the image forming section 1a, and is a tray for placing paper P on which an image has been formed.

Further, the image forming section 1a of the image forming apparatus 1 is provided with a paper conveying device 20 for conveying the paper P in the paper feed tray 18 to the paper discharge tray 19 via the secondary transfer device 27 and the fixing device 17. ing. The paper conveying device 20 has an S-shaped paper conveying path S. Along the paper conveying path S, there are a pickup roller 31, a pair of separation rollers 31a and 31b, a registration roller 32, a pre-registration roller 33, and a fixing device 17. , and a discharge roller 34 are arranged.

The pickup roller 31 is provided near the end of the paper feed tray 18 and is a pickup roller that feeds the paper P from the paper feed tray 18 to the paper transport path S one by one. One separation roller 31a passes the paper P between itself and the other separation roller 31b, and conveys the paper P to the paper conveyance path S while separating the paper one by one. The registration roller 32 temporarily holds the paper P conveyed from the paper feed tray 18, and conveys the paper P to the transfer roller 27a at the timing when the leading edge of the toner image on the photosensitive drum 13 and the leading edge of the paper P are aligned. . The pre-registration rollers 33 are small rollers for promoting and assisting the transportation of the paper P. As shown in FIG.

The fixing device 17 is of a belt fixing type. A fixing belt 173 is wound around a fixing roller 171 and a heating roller 172 , and a pressure roller 174 is pressed against the fixing roller 171 via the fixing belt 173 . ing. The fixing device 17 receives the paper P on which the unfixed toner image is formed, and conveys the paper P while sandwiching it between the fixing belt 173 and the pressure roller 174 . After fixing, the paper P is discharged onto the paper discharge tray 19 by the paper discharge rollers 34 . Although the fixing device 17 is a belt fixing type fixing device, the fixing device 17 is not limited thereto, and may be a type in which the pressure roller 174 directly presses the fixing roller 171 .

The photoreceptor drum 13 and the transfer drive roller 22 may not be directly connected to the driving unit 51, and a gear or a clutch may be interposed therebetween. may be driven at different speeds or may be driven at different timings.

FIG. 2 is an explanatory diagram of a main part extracting and showing the vicinity of the intermediate transfer belt device.

In FIG. 2, a part of the configuration related to the intermediate transfer belt device 16 is extracted from the image forming apparatus 1, and the photosensitive drum 13, the intermediate transfer belt 21, the transfer drive roller 22, the transfer driven roller 23, the transfer roller 27a, the rotating Position sensors (photoreceptor sensor 41, transfer sensor 42) and image detection sensor 43 are shown.

As described above, the intermediate transfer belt 21 is stretched around the transfer driving roller 22 and the transfer driven roller 23 . A plurality of transfer pressure rollers for pressing the intermediate transfer belt may be provided inside the intermediate transfer belt 21, and the four transfer pressure rollers are located between the transfer driving roller 22 and the transfer driven roller 23. , are provided at positions facing the inner circumferential surface on the lower side of the intermediate transfer belt 21 . The intermediate transfer belt 21 has a structure that expands and contracts depending on the position of the stretched rollers. Transform at will. Four photosensitive drums 13 are arranged below the intermediate transfer belt 21 .

The photoreceptor drum 13 is provided with a portion to be detected such as a rib or a projection, and a photoreceptor sensor 41 for detecting the presence or absence of the portion to be detected is arranged nearby. The part to be detected rotates along the trajectory as the photoreceptor drum 13 rotates, and the photoreceptor sensor 41 detects the timing when the part to be detected passes a predetermined point on the trajectory. Thus, the rotational position of the photoreceptor drum 13 can be detected from the detection result of the photoreceptor sensor 41 .

Further, the transfer drive roller 22 is also provided with a portion to be detected similar to that of the photosensitive drum 13, and a transfer sensor 42 for detecting the presence or absence of the portion to be detected is arranged in the vicinity. The detection result of the transfer sensor 42 can also detect the rotational position of the transfer driving roller 22 in the same manner as the photoreceptor sensor 41 .

An image detection sensor 43 is arranged near the surface of the intermediate transfer belt 21 between the most downstream photosensitive drum 13 and the transfer drive roller 22 in the direction of rotation of the intermediate transfer belt 21 . The image detection sensor 43 detects the toner image transferred onto the intermediate transfer belt 21 and outputs a pitch detection signal.

In the image forming apparatus 1, when measuring the speed variation of the intermediate transfer belt 21, the speed unevenness detection image KG is formed on the intermediate transfer belt 21 at a constant pitch. A plurality of speed unevenness detection images KG are formed over a preset range (detection image formation range KGa). It is supposed to be the length. When the length of the detection image forming range KGa is changed, the number of speed non-uniformity detection images KG to be formed may be appropriately adjusted accordingly. Also, the measurement of the speed variation on the intermediate transfer belt 21 will be described later with reference to FIG.

FIG. 3 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the invention.

In FIG. 3, a part of the configuration related to the intermediate transfer belt device 16 is extracted from the image forming apparatus 1, and other members may be provided.

The drive unit 51 is, for example, a motor, and rotates the four photosensitive drums 13 and the transfer drive rollers 22 respectively.

The separation/contact portion 52 causes the intermediate transfer belt 21 and the photoreceptor drum 13 to be separated from each other by causing the transfer pressure contact roller, which is swingably supported, to be separated from and contact with the photoreceptor drum 13 .

The control unit 54 a controls driving of the driving unit 51 . Specifically, the control unit 54a instructs the driving unit 51 to start or stop driving, or to change the driving speed.

The storage unit 53 is a storage medium such as an HDD, and stores detection results from the sensor, calculation results from the calculation unit 54b, and the like.

The calculation unit 54b calculates a drum speed fluctuation signal for the photosensitive drum 13 and a roller speed fluctuation signal for the transfer driving roller 22 based on the detection results of the rotation position sensor and the image detection sensor 43. FIG. The drum speed fluctuation signal and the roller speed fluctuation signal will be described later with reference to FIGS. 7A and 7B.

The control unit 54a and the calculation unit 54b are stored as a program preinstalled in the CPU 54 provided in the image forming apparatus 1. FIG. The CPU 54 executes the processing described later by executing the stored program.

Next, the operation of detecting the speed unevenness detection image KG in the image forming apparatus 1 will be described with reference to the drawings.

FIG. 4 is an explanatory diagram showing the detection result of the image detection sensor.

The image forming apparatus 1 first instructs the surface of the photosensitive drum 13 to form the speed unevenness detection image KG at a predetermined pitch. At this time, the ideal detection timing for reaching the detection position of the image detection sensor 43 is calculated from the timing at which the speed unevenness detection image KG is formed and the transport speed at each part. By the way, in the image forming apparatus 1, speed fluctuations may occur due to eccentricity of the photosensitive drum 13, the transfer driving roller 22, and the like, and the conveying speed of the speed unevenness detection image KG on the intermediate transfer belt 21 may fluctuate. . Therefore, the timing at which the image detection sensor 43 detects the speed unevenness detection image KG is deviated from the ideal detection timing, and the speed fluctuation is estimated by checking the difference.

In FIG. 4, the upper part shows the detection signal (ideal signal) of the speed unevenness detection image KG at the ideal detection timing, and the lower part shows an example of the actual detection signal (actual measurement signal) of the speed unevenness detection image KG. The image detection sensor 43 outputs "High" when the speed unevenness detection image KG is detected, and outputs "Low" when the speed unevenness detection image KG is not detected. For the sake of explanation, the change when the output is switched from "Low" to "High" is sometimes called a pulse.

Specifically, in the ideal signal, a plurality of pulses (first ideal pulse RP1 to fourth ideal pulse RP4) exist at a predetermined pitch (ideal interval RW). Here, the time corresponding to the first ideal pulse RP1 is used as the reference time, and the time corresponding to the subsequent second ideal pulse RP2 can be grasped from the reference time and the ideal interval RW. Also, in the measured signal, the same number of pulses (first measured pulse KP1 to fourth measured pulse KP4) are detected at timings slightly shifted from the ideal signal. Then, the difference (first difference d1) between the detection time "t1" of the first ideal pulse RP1 and the first measured pulse KP1 corresponding to the first ideal pulse RP1 is calculated. Similarly, the second difference d2 is calculated from the comparison between the second ideal pulse RP2 and the second measured pulse KP2, the third difference d3 is calculated from the comparison between the third ideal pulse RP3 and the third measured pulse KP3, A fourth difference d4 is calculated from a comparison between the fourth ideal pulse RP4 and the fourth measured pulse KP4. FIG. 4 shows a comparison of four pulses, but actually, the number of pulses that form the speed unevenness detection image KG is detected, and the detection results of all the speed unevenness detection images KG are put together to form a pitch detection signal PS. should be output. By providing an index for comparing the detection timings in this manner, erroneous detection due to noise or the like can be avoided, and measurement accuracy can be improved.

FIG. 5 is an explanatory diagram showing an example of the pitch detection signal.

FIG. 5 shows changes in the conveying speed of the intermediate transfer belt 21 over time as the pitch detection signal PS. The horizontal axis in FIG. 5 represents the time change in angle according to the rotation of the photosensitive drum 13 and the transfer driving roller 22 . Note that the horizontal axis is not limited to this, and an index indicating rotation of the photosensitive drum 13 and the transfer drive roller 22 may be used, or may be appropriately converted into time, length, or the like. The vertical axis in FIG. 5 indicates changes in the transport speed of the intermediate transfer belt 21, and the transport speed increases upward and decreases downward.

As shown in FIG. 5, the speed non-uniformity detection image KG is formed at a predetermined pitch, and the pitch detection signal PS is discrete data examined at the location where the speed non-uniformity detection image KG is formed. Therefore, the calculation unit 54b may perform calculation so as to interpolate between the times when the speed unevenness detection image KG is detected. Here, the pitch detection signal PS itself may be interpolated, or a drum speed fluctuation signal HS1 and a roller speed fluctuation signal HS2, which will be described later, may be interpolated. In this way, from the speed non-uniformity detection image KG formed at a constant pitch, by interpolating and calculating so as to obtain a continuous signal, the speed fluctuation in the section where the speed non-uniformity detection image KG is not detected Ingredients can be determined with high accuracy.

In this embodiment, the pitch detection signal PS changes periodically. Specifically, the pitch detection signal PS changes in the same manner in the first period S1 from 0 degrees to 720 degrees and the second period S2 from 720 degrees to 1440 degrees.

Next, the configuration of this embodiment will be described with reference to FIG. 6 in which the first period S1 of the pitch detection signal PS is extracted.

FIG. 6 is an explanatory diagram showing the positional relationship between a portion of the pitch detection signal, the photosensitive drum, and the transfer driving roller.

FIG. 6 shows the first cycle S1 of the pitch detection signal PS and the corresponding detection results of the photoreceptor sensor 41 and the transfer sensor 42 . In the photoreceptor sensor 41, during the first cycle S1, 0 degrees (first photoreceptor signal DS1), 360 degrees (second photoreceptor signal DS2), and 720 degrees (third photoreceptor signal DS3) are detected. This indicates that the photoreceptor drum 13 has made two turns. In the transcription sensor 42, 0 degrees (first transcription signal RS1), 240 degrees (second transcription signal RS2), 480 degrees (third transcription signal RS3), and 720 degrees (fourth transcription signal RS3) during the first cycle S1. The detected part is detected by the signal RS4), which indicates that the transfer drive roller 22 has made three turns.

In order to configure the pitch detection signal PS to change periodically, it is necessary to set the circumferential length of the photosensitive drum 13 and the circumferential length of the transfer drive roller 22 in a predetermined relationship in advance. Specifically, the circumferential length of the photosensitive drum 13 and the circumferential length of the transfer driving roller 22 are set so that the quotient of the least common multiple of both is an even number and the other is an odd number. In other words, when one of the circumferential length of the photosensitive drum 13 and the circumferential length of the transfer driving roller 22 is A, the other is B, and two arbitrary integers are α and β, then the circumference of the photosensitive drum 13 is The circumferential length and the circumferential length of the transfer driving roller 22 satisfy the relationship Aβ=B(α+0.5). Here, the length corresponding to the least common multiple of the circumferential length of the photosensitive drum 13 and the circumferential length of the transfer drive roller 22 is defined as the coinciding circumference length. corresponds to the length of the coinciding cycle.

When calculating a drum speed fluctuation signal HS1 and a roller speed fluctuation signal HS2, which will be described later, the calculation section 54b extracts the first half SE1 and the second half SE2 of the same lap length from the pitch detection signal PS. Here, the first half SE1 corresponds to the pitch detection signal PS from 0 degrees to 360 degrees, and the second half SE2 corresponds to the pitch detection signal PS from 360 degrees to 720 degrees.

Next, a method of calculating the drum speed fluctuation signal HS1 and the roller speed fluctuation signal HS2 from the pitch detection signal PS will be described with reference to FIGS. 7A and 7B.

FIG. 7A is an explanatory diagram showing the relationship between the first and second halves of the pitch detection signal and the drum speed fluctuation signal.

In FIG. 7A, the first half SE1 (first half signal PS1) and the second half SE2 (second half signal PS2) extracted from the pitch detection signal PS are shown superimposed. In this embodiment, the drum speed fluctuation signal HS1 is calculated by adding the first half signal PS1 and the second half signal PS2.

As shown in FIG. 6, the photosensitive drum 13 makes one turn during the first half SE1 and one turn during the second half SE2, and rotates in the same way between the first half SE1 and the second half SE2. ing. On the other hand, the transfer drive roller 22 makes one and a half revolutions during the first half SE1, and the phase at the beginning of the second half SE2 is opposite to that at the beginning of the first half SE1. After that, the transfer driving roller 22 returns to the initial phase by making one and a half rotations during the second half SE2. In other words, the transfer driving roller 22 rotates so that the front half SE1 and the rear half SE2 are in opposite phases. Therefore, when the first half signal PS1 and the second half signal PS2 are added, the fluctuation component at the transfer driving roller 22 is canceled and only the fluctuation component at the photosensitive drum 13 remains. By adding the first half signal PS1 and the second half signal PS2, the fluctuation component at the photosensitive drum 13 is added. good.

FIG. 7B is an explanatory diagram showing the relationship between the first and second halves of the pitch detection signal and the roller speed fluctuation signal.

In FIG. 7B, as in FIG. 7A, the first half signal PS1 and the second half signal PS2 extracted from the pitch detection signal PS are superimposed. In this embodiment, the roller speed fluctuation signal HS2 is calculated by subtracting the second half signal PS2 from the first half signal PS1. In other words, by subtracting the second half signal PS2 from the first half signal PS1, contrary to the drum speed fluctuation signal HS1, the fluctuation component at the photosensitive drum 13 is canceled and only the fluctuation component at the transfer drive roller 22 is eliminated. Since it remains, the value should be adjusted to calculate the roller speed fluctuation signal HS2.

As described above, the photoreceptor drum 13 and the transfer drive roller 22 are rotated in a specific rotation, and by setting the circumference so that the length of the circumference is the same, the speed unevenness due to the eccentricity is changed periodically. can be Then, by performing calculations in consideration of the cycle of speed unevenness, it is possible to separate and extract speed fluctuation components between the photosensitive drum 13 and the transfer driving roller 22 .

Further, the drum speed fluctuation signal HS1 and the roller speed fluctuation signal HS2 can be separately calculated from one pitch detection signal PS by simple arithmetic processing such as addition and subtraction. In the present embodiment, the drum speed fluctuation signal HS1 is calculated by addition, and the roller speed fluctuation signal HS2 is calculated by subtraction. By , addition and subtraction may be interchanged.

The control section 54a corrects the drive conditions in the drive section 51 based on the drum speed fluctuation signal HS1 and the roller speed fluctuation signal HS2. In this way, by correcting the drive speed in consideration of the speed fluctuation due to eccentricity, it is possible to eliminate the speed unevenness due to eccentricity.

As for the control of the driving section 51, the rotational positions of the photosensitive drum 13 and the transfer driving roller 22 may be taken into consideration. In other words, speed fluctuations due to eccentricity correspond to the rotational positions of the photosensitive drum 13 and the transfer driving roller 22, and by correcting the driving speed in consideration of these, speed unevenness can be eliminated with high accuracy. can.

It is preferable that the drum speed fluctuation signal HS1 is associated with the rotational position of the photosensitive drum 13 and the roller speed fluctuation signal HS2 is associated with the rotational position of the transfer drive roller 22 . When the positional relationship between the rotational position of the photosensitive drum 13 and the rotational position of the transfer driving roller 22 changes, the control section 54a adjusts the driving conditions according to the rotational positions of the photosensitive drum 13 and the transfer driving roller 22. Just do it. That is, even if the rotational positions of the photosensitive drums 13 and the transfer driving roller 22 are changed by moving the photosensitive drums 13 away from the intermediate transfer belt 21, etc., the speed fluctuation component can be grasped by considering the rotational positions. , can be controlled in accordance with each rotational position.

A plurality of drive conditions may be set according to the rotational speeds of the photosensitive drum 13 and the transfer drive roller 22 . At this time, the calculation unit 54b calculates the drum speed fluctuation signal HS1 and the roller speed fluctuation signal HS2 based on a plurality of driving conditions. By calculating the drum speed fluctuation signal HS1 and the roller speed fluctuation signal HS2 corresponding to the rotational speeds of the photosensitive drum 13 and the transfer drive roller 22 in this way, it is possible to perform control according to the respective drive conditions. .

In the control for eliminating the speed unevenness, first, the calculator 54b generates an antiphase signal obtained by inverting the phase of at least one of the drum speed fluctuation signal HS1 and the roller speed fluctuation signal HS2. Then, the control unit 54a sets a driving condition in which the speed fluctuation is canceled by the anti-phase signal for the drive unit 51 for which the anti-phase signal is generated. For example, when an anti-phase signal is generated with respect to the drum speed fluctuation signal HS1, driving conditions for canceling the drum speed fluctuation signal HS1 are set by adding the anti-phase signal to the driving speed of the photosensitive drum 13. In this case, the control unit 54a controls the driving unit 51 of the photoreceptor drum 13 so as to generate speed fluctuations based on the opposite phase signal while synchronizing with the detection timing of the detection target detected by the photoreceptor sensor 41. FIG. In controlling the drive unit 51 of the photoreceptor drum 13 , the speed is varied so as to have an opposite phase to the speed variation phase due to the eccentricity of the photoreceptor drum 13 . As a result, the speed fluctuation component is canceled, and the photosensitive drum 13 can be rotated at a constant speed without speed fluctuation. Similarly, when the target for generating the opposite phase signal is the transfer drive roller 21, it can be rotated at a constant speed.

In addition, the embodiment disclosed this time is an example in all respects, and does not serve as a basis for a restrictive interpretation. Therefore, the technical scope of the present invention is not to be interpreted only by the above-described embodiments, but is defined based on the description of the claims. In addition, all changes within the meaning and range of equivalence to the claims are included.

REFERENCE SIGNS LIST 1 image forming apparatus 13 photoreceptor drum 21 intermediate transfer belt 22 transfer drive roller (an example of a drive roller)
41 photoreceptor sensor (an example of a rotational position sensor)
42 transfer sensor (an example of a rotational position sensor)
43 image detection sensor 51 drive unit 52 contact/separation unit 53 storage unit 54 CPU
54a control unit 54b calculation unit

Claims (10)

a plurality of photoreceptor drums having the same circumferential length;
an intermediate transfer belt onto which the toner images formed on the plurality of photoreceptor drums are transferred;
a drive roller for driving the suspended intermediate transfer belt;
a driving unit that transmits a driving force to each of the photosensitive drum and the driving roller;
a control unit that controls driving conditions in the driving unit;
a rotational position sensor for detecting respective rotational positions of the photosensitive drum and the drive roller;
an image detection sensor that detects the toner image transferred onto the intermediate transfer belt;
an image forming unit that calculates a drum speed fluctuation signal of the photosensitive drum and a roller speed fluctuation signal of the drive roller based on detection results of the rotational position sensor and the image detection sensor; a device,
The circumferential length of the photosensitive drum and the circumferential length of the drive roller are set so that the quotient of the least common multiple of both is an even number and the other is an odd number,
When the length corresponding to the least common multiple of the circumferential length of the photosensitive drum and the circumferential length of the driving roller is defined as the coinciding circumference length,
The image detection sensor detects a speed unevenness detection image formed at a constant pitch and outputs a pitch detection signal,
The calculation section extracts the first half and the second half of the same lap length from the pitch detection signal, and performs a predetermined calculation using the first half and the second half to calculate the drum speed fluctuation signal and the roller. An image forming apparatus characterized by calculating a speed fluctuation signal. The image forming apparatus according to claim 1,
The image forming apparatus, wherein the calculation section calculates the drum speed fluctuation signal and the roller speed fluctuation signal by addition and subtraction of the first half and the second half. The image forming apparatus according to claim 1 or claim 2,
When one of the circumferential length of the photosensitive drum and the circumferential length of the driving roller is A, the other is B, and two arbitrary integers are α and β,
The image forming apparatus, wherein the peripheral length of the photosensitive drum and the peripheral length of the drive roller satisfy the relationship Aβ=B(α+0.5). The image forming apparatus according to any one of claims 1 to 3,
The pitch detection signal records the time when the speed unevenness detection image is detected,
The image forming apparatus, wherein the calculation unit calculates the drum speed fluctuation signal and the roller speed fluctuation signal by interpolating between points in time when the speed unevenness detection image is detected. The image forming apparatus according to any one of claims 1 to 4,
A reference time, which is the point of time of first detection, and an ideal detection timing calculated from the reference time based on the formed pitch are set for the speed unevenness detection image,
The image forming apparatus, wherein the calculation unit calculates a difference between a time point at which the speed unevenness detection image is detected and the ideal detection timing. The image forming apparatus according to any one of claims 1 to 5,
The image forming apparatus, wherein the control unit corrects the driving condition based on the drum speed fluctuation signal and the roller speed fluctuation signal. The image forming apparatus according to claim 6,
The calculation unit generates an anti-phase signal obtained by inverting the phase of at least one of the drum speed fluctuation signal and the roller speed fluctuation signal,
The image forming apparatus according to claim 1, wherein the control section sets the drive condition in which the speed fluctuation is canceled by the opposite phase signal for the target driving section that generated the opposite phase signal. The image forming apparatus according to claim 6 or 7,
The image forming apparatus, wherein the control section corrects the driving conditions according to rotational positions of the photosensitive drum and the driving roller. The image forming apparatus according to claim 8,
the drum speed variation signal is associated with the rotational position of the photoreceptor drum;
the roller speed variation signal is associated with the rotational position of the drive roller;
The control unit adjusts the driving condition according to the rotational positions of the photosensitive drum and the driving roller when the positional relationship between the rotational position of the photosensitive drum and the rotational position of the driving roller changes. An image forming apparatus characterized by: The image forming apparatus according to any one of claims 6 to 9,
A plurality of driving conditions are set according to the rotational speeds of the photosensitive drum and the driving roller,
The image forming apparatus, wherein the calculation unit calculates the drum speed fluctuation signal and the roller speed fluctuation signal based on the plurality of driving conditions.

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