JPH07261499A - Image forming device - Google Patents

Abstract

PURPOSE:To provide a transfer type image forming device capable of preventing the color slurring at the time of superimposing. CONSTITUTION:In the image forming device, by the sensor aperture 59c of a sensor 59 for detecting the test pattern formed at a prescribed distance being transported by a transporting belt 51, the fluctuation of period of the test pattern transported on the transporting belt 51 is detected, then based on the result, the position of starting the rotation of the transporting belt 51, the timing of rotating belt supporting rollers 53 and 52 for rotating the transporting belt 51, and the position of starting the rotation of the worm wheels 114, 124, 134 and 144 for driving the drums 11, 21, 31 and 41 are respectively changed, and by this way, the phase relation is adjusted so as to minimize the color slurring. Moreover, respectively the peripheral length of the drum 11, 21, 31 and 41, the peripheral length of the transfer belt driving roller 53 and 52, and the peripheral length of the transfer belt 51 are set to be an integral ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a color laser printer, a color digital copying machine or the like to form an image for each color component on a plurality of photosensitive drums and then superimpose it on a recording sheet. The present invention relates to a transfer type image forming apparatus.

[0002]

2. Description of the Related Art A transfer type digital color image forming apparatus forms a plurality of photosensitive drums on which a latent image is formed for each image data separated into color components, and a latent image formed on the photosensitive drum. A plurality of developing means for developing and forming an image corresponding to each color component on each photoconductor drum; a plurality of transfer devices for sequentially transferring the images developed through the plurality of developing means to a recording sheet; and recording It has a fixing device for fixing the image transferred on the paper to the recording paper.

As a method of driving a plurality of photosensitive drums, a method of arranging a dedicated motor for each drum and driving each drum (direct drive), or a method of transmitting the driving force of one motor by a worm gear or the like A method of transmitting the data to each drum via a means is known. In the latter method, one motor drives all the photosensitive drums, for example, a color drum corresponding to color components of yellow = Y, magenta = M and cyan = C, and black = An example is known in which a black drum corresponding to B is driven by two motors, a color motor and a black motor.

[0004]

In this type of color digital copying apparatus, there is a problem that color misregistration occurs when the images of the respective color components which are sequentially superposed on the recording paper do not exactly match.

This color misregistration appears in the image every one rotation cycle of the worm wheel or the photosensitive drum when printing lines at equal intervals. This is due to the eccentricity of the worm wheel gear in the worm gear type.
It is considered that this is caused by non-uniform meshing between the worm gear and the worm wheel and fluctuations in the angular velocity of the worm wheel. Even in the direct drive system, similar color shift occurs due to eccentricity of the drum.

These color misregistrations are caused by changing the combination of the image forming units for each color component at the time when the image forming apparatus is shipped from the factory and by the engagement of the worm gear and the worm wheel in each image forming unit. It can be reduced within a certain range by changing the position. However, it is known that a new phenomenon occurs due to changes over time or replacement of the image forming unit.

An object of the present invention is to provide a transfer type image forming apparatus in which a color shift is less likely to occur during superposition.

[0008]

The present invention has been made on the basis of the above problems, and includes a first rotation driving means for rotating a first image carrier and a second rotation driving means for rotating a second image carrier. Two rotation driving means, a conveying means for holding and conveying the images formed on the first and second image carriers, and a detecting means for detecting the image conveyed by the conveying means,
Based on the position of the image detected by the detecting means, a calculating means for calculating an image shift due to eccentricity of each of the first rotation driving means and the second rotation driving means, and calculation of this calculation means. Based on the result, there is provided an image forming apparatus including: a changing unit that changes a timing of urging the second rotation driving unit.

Further, according to the present invention, the first rotation driving means for rotating the first image carrier, the second rotation driving means for rotating the second image carrier, and the first and the first Two
Transporting means for holding and transporting the image formed on the image carrier, and third rotation driving means for rotating the transporting means,
Based on the detecting means for detecting the image conveyed by the conveying means and the position of the image detected by the detecting means, the first rotation driving means, the second rotation driving means, and the third rotation driving means. After changing the image shift due to each eccentricity of the driving means, and changing the timing for urging the third rotation driving means based on the calculation result of this calculating means, the second means is further added. An image forming apparatus is provided that includes a changing unit that changes the timing of urging the rotation driving unit.

Further, according to the present invention, first rotation driving means for rotating the first image carrier, second rotation driving means for rotating the second image carrier, and the first and the first A conveying unit that holds and conveys the image formed on the second image carrier, a third rotation driving unit that rotates the conveying unit, and a detecting unit that detects the image conveyed by the conveying unit; Second for detecting the displacement of the outer circumference of the conveying means
Of the first rotation driving means, the second rotation driving means, and the third rotation driving means based on the position of the image detected by the detection means of FIG. Based on the calculation result of the calculation means and the calculation means for calculating the image deviation due to the displacement of the outer circumference of the conveyance means detected by the second detection means from the calculated eccentricity. An image forming apparatus is provided that includes a changing unit that changes the timing of urging the third rotation driving unit and then changes the timing of urging the second rotation driving unit.

[0011]

According to the present invention, the position of the image conveyed by the conveying means is calculated by the detection result detected by the detecting means, and the first and second image carriers and the rotational driving corresponding to the respective first and second image carriers. Eccentricity of means is required. According to the obtained eccentricity, by changing the timing of energizing either the second rotation driving means or the rotation driving means, the first and second image bearing members and the rotation driving means corresponding to each of them. The phase shift due to the eccentricity can be reduced to a minimum.

Further, by further obtaining the eccentricity of the third rotation driving means for rotating the conveying means, the first and second image carriers and the rotation driving means and the third rotation driving means respectively corresponding thereto are The phase shift due to eccentricity can be reduced to the minimum.

Further, the displacement of the outer circumference of the conveying means is detected,
By removing the influence of the displacement of the outer circumference of the conveying means included in the eccentricity of the first and second image carriers and the rotation driving means and the third rotation driving means respectively corresponding thereto, the phase shift is further reduced. it can.

Therefore, it is possible to provide a color image having no color shift.

[0015]

Embodiments of the present invention will be described below.

1 to 3 show a transfer type color image forming apparatus in which an embodiment of the present invention is utilized.
1 is a block diagram showing an example of control of the image forming apparatus shown in FIG. Also, FIG.
FIG. 3 is a schematic view showing the periphery of the drive device in a state where the periphery of the photosensitive drum and the drive portion of the image forming apparatus shown in FIG. 2 is extracted.

As shown in FIG. 2, the image forming apparatus 1 includes first to fourth image forming units 10, 20, 30 and 40 for forming an image for each color-separated color component, and each image forming unit.
It has a transfer belt 51 that conveys the image formed by 10, 20, 30 and 40 in the direction of the arrow. The image forming units 10, 20, 30 and 40 are arranged in series along the transfer belt 51.

The image forming units 10, 20, 30 and 40 respectively include a photoconductor drum (image carrier) 11 on which an image is formed,
Includes 21, 31, and 41. The axes of the respective photosensitive drums (image bearing members) 11, 21, 31 and 41 are arranged so as to be orthogonal to the direction in which the image is conveyed by the transfer belt 51.

Around the photosensitive drums (image bearing members) 11, 21, 31 and 41, charging rollers 12, 22, which are charging means, are provided.
32 and 42, a solid recording head 13 as a latent image forming means,
23, 33 and 43, developing devices 14, 24 and 34 as developing means
And 44, transfer rollers 15, 25, 35 and 45 as transfer means, and cleaners 16, 26, 36 and 46, respectively, are sequentially arranged along the rotation direction of the corresponding photosensitive drum. There is. In addition, each of the image forming units 10, 20, 30 and 40
Respectively form an image corresponding to the color-separated color components, that is, a yellow image = Y, a magenta image = M, a cyan image = C, and a black image = B. In this example, the image forming unit 10 sets yellow = Y,
20 is magenta = M, and the image forming unit 30 is cyan image = C
, And the image forming unit 40 corresponds to black = B, respectively. Therefore, each developing device 14, 24, 34
And 44 are yellow (Y) and magenta, respectively.
Developers (toners) corresponding to (M), cyan (C), and black (B) are contained. Transfer belt 51
Is rotated in the direction of the arrow as the transfer belt support rollers 52 and 53 rotate counterclockwise. One of the transfer belt support rollers 52 and 53, for example, the image forming unit 10
The roller 52 disposed in the vicinity of is rotated by the transfer belt drive motor 54.

Below the transfer belt 51, a cassette 55 for accommodating a recording medium such as a sheet P is arranged.
The paper P accommodated in the cassette 55 is taken out of the cassette 55 by the paper feed roller 56 rotated at a predetermined timing under the control of the control unit 100, and is guided to the aligning roller 58 via the transport roller 57.

The process of forming yellow (Y) will be described below with reference to the first image forming section 10. Needless to say, the second to fourth image forming units 20, 30 and
40 works similarly.

The photosensitive drum 11 rotates in the direction of the arrow in the drawing, and its surface is uniformly charged by the charging roller 12. After that, by being exposed by the solid recording head 13,
An electrostatic latent image corresponding to the image data (Y) is formed on the surface of the photosensitive drum 11. The latent image formed on the drum 11 is developed by the developing device 14 containing yellow (Y) toner and converted into a Y toner image.

The Y toner image on the photosensitive drum 11 is transferred to the cassette 55 at a position where the photosensitive drum 11 and the transfer belt 51 face each other.
The transfer roller 15 transfers the transfer paper P to the transfer paper P, which is taken out from the transfer paper 51 and attracted and aligned on the transfer belt 51 at a predetermined timing by the aligning roller 58.

Hereinafter, the M toner images formed on the respective photosensitive drums 21, 31 and 41 by the second image forming section 20, the third image forming section 30 and the fourth image forming section 40, respectively,
The C toner image and the B toner image are sequentially superposed on the paper P conveyed by the transfer belt 51. That is, in the case of printing in a plurality of colors, each image forming unit 10, 20, 30
By 40 and 40, the image forming operation of the process of one cycle of charging → exposure → developing → transfer is executed, and the toner images of a plurality of colors are multi-transferred onto the transfer paper P. In addition, each photosensitive drum 1
Untransferred toner on 1, 21, 31 and 41 is cleaner 16, 2
Cleaned by 6, 36 and 46 respectively.

Here, when the operation mode of the image forming apparatus 2 is the adjustment mode, the image formed by each of the image forming units 10, 20, 30 and 40 by the timing detecting device 59 is used.
The position of the (test line) is detected and the phase shift of each image forming unit is detected.

The transfer paper P on which the respective toner images have been transferred is separated from the transfer belt 51 and conveyed to the fixing device 60, where it is fixed.
The toner image heated by is fused and fixed, and then discharged to the tray 62. Further, each toner adhering to the transfer belt 51 and paper dust generated from the paper P are removed by the belt cleaner 63.

Referring to FIG. 3, the image forming units 10, 20,
The drums 11, 21, 31 and 41 of 30 and 40 are rotated by drive shafts 110, 120, 130 and 140, respectively, which are arranged along the axis of the drums 11, 21, 31 and 41, respectively. Worm wheels 112, 122, 132 and 142 are arranged on each drive shaft 110, 120, 130 and 140 and are arranged in position on the rotary shafts 102 and 104 of the first and second motors 101 and 103. Worm gear 11
The rotations of the first and second motors 101 and 103 are transmitted via 1, 121, 131 and 141. The drive shafts 120 and 1 of the second image forming unit 20 and the third image forming unit 30 are
30 is provided with electromagnetic clutches 125 and 135 for selectively transmitting the rotation of the first motor 101 to the worm gears 121 and 131, and electromagnetic brakes 126 and 136 for stopping the rotation of the drive shafts 120 and 130. Has been done. Therefore, each of the photoconductor drums 11, 21, 31, and 41 can be independently rotated.

The drive shafts 110, 120, 130 and 140 are provided with eccentricities generated by each rotation of the drive shafts 110, 120, 130 and 140 and the drums 11, 21, 31 and 41 connected to the drive shafts. Pulse plates for detecting
3, 133 and 143, and photo interrupters 114, 124, 134 and 1 corresponding to the respective pulse plates
44 are arranged. A similar pulse plate 153 and photo interrupter 154 are also provided on the rotary shaft 150 of the transfer belt support roller 53.
Similar photo interrupters 151 are arranged at positions where the rotation cycle can be detected.

By the way, as described above, in the transfer type image forming apparatus as shown in FIG. 2, when the images of the respective color components which are sequentially superposed on the recording paper do not exactly match, the color shift occurs. There is a problem that occurs. This color misregistration can be obtained by printing lines at equal intervals every one rotation cycle of the photosensitive drum, every one rotation of the transfer belt 51, or one transfer belt support roller 53 (52).
Appears in the image with each rotation.

Here, considering the cause of color misregistration, the relationship between the drums 11, 21, 31 and 41 of the image forming units 10, 20, 30 and 40 and the rotating shafts 110, 120, 130 and 140 is considered. Eccentricity, eccentricity between each rotating shaft 110, 120, 130 and 140 and each worm wheel 112, 122, 132 and 142, or transfer belt 51 during one rotation of transfer belt 51.
It is thought that this is due to swells and the like. Therefore, FIG.
As shown in, the phase alignment of the transfer belt 51, that is, "waviness" is detected (STP1) and the phase of each drum is detected (S
TP2) and phase combination of each drum (STP3)
After that, the correction amount for each drum is averaged (STP
4) By changing the printing conditions of each color component according to the degree of eccentricity of the drum and belt obtained in each step (STP5) and printing (STP6),
A color image without color shift is formed.

Next, the eccentricity and the color shift of the image will be considered.

In FIG. 5, the first photosensitive drum 11 is
Assume that neither the rotating shaft 110 nor the worm wheel 112 is eccentric. On the other hand, the second photosensitive drum
It is assumed that either or both of the worm wheel 122 and the rotating shaft 120 are eccentric to 21.

Here, the recording head 13 and
If the image is exposed by 23 and lines are printed, lines are equally spaced on the first drum 11 because the angular velocity of the drum is constant. On the other hand, the distance between the lines printed by the second drum 21 is expanded or contracted according to the degree of eccentricity.

[0034] Specifically, in FIG. 5, a ₁ on the first photosensitive drum 11, a _2, a _3, ..., when a _n points indicating the exposure points for each line, between a ₁ and a ₂ Distance (a ₁ ~
(denoted by a ₂ ) is the line interval between the first line and the second line, and the distance between a _n-1 and a _n (similarly a _{n-1 to} a _n ) is n.
This corresponds to the line interval between the -1st line and the nth line. On the other hand, since the angular velocity of the second drum 21 is not constant (θ _b1 ≠
θ _b2 ≠ θ _b3 ≠ θ _b4 ≠ ...), even if exposure is performed at equal time intervals, b ₁
˜b ₂ ≠ b ₂ ˜b ₃ ≠ b ₃ ˜b ₄ ≠ ...

Therefore, when the image formed by the drum 11 and the image formed by the drum 21 are superposed, a color shift occurs even though the image formed by the drum 11 is output at a constant interval. .

More specifically, FIG. 6A and FIG.
As shown in (b) and FIGS. 7 (a) and 7 (b), the first and second drums have a drum 1 rotation cycle (that is, a worm wheel) due to eccentricity of the worm wheel and the rotation shaft. It is considered that the sine wave is rotated with a sine wave-shaped swell every one rotation cycle of the rotation axis. In each figure, a smooth sine wave is used, but in reality, other fluctuation components are also superimposed, so as shown in the circle in Fig. 6 (b), the small amplitude Is included. Also, it goes without saying that there are different swell amplitudes and waveforms for each drum and the corresponding driving device.

According to FIGS. 6 (a) and 6 (b), the drum at the time when the first drum is exposed by the first head and at the time when the second drum is exposed by the second head The phase of is exactly the opposite phase.

Here, assuming that n equal-spaced line images are printed, the description will be given focusing on the i-th line.

I of the first color printed by the first head
The line A is the point A on the phase waveform of Fig. 6 (a).
When the i-th line of the second color is represented by the point B in FIG. 6 (b), each image (line) shows that the i-th line of the first color is as shown in FIG. 6 (c). On the paper, the i-th line of the second color is displaced toward the paper front end in the paper rear end direction. That is, when the images written on the first drum and the second drum are superposed on the paper on the transfer belt,
As shown in (c), a leading image and a delayed image are provided for the ideal line. The shift caused by the condition shown in FIG. 6 is a reverse phase shift and has a shift amount indicated by E.

On the other hand, for example, the i-th line of the first color printed by the first head is point A on the phase waveform of FIG. 7 (a), and the i-th line of the second color is the same. 7 (b)
When represented by point B of, each image (line) is
As is clear from FIG. 7C, both the i-th line of the first color and the i-th line of the second color deviate from the ideal line on the paper in the front end direction of the paper. The shift caused by the condition shown in FIG. 7 is a shift in phase and has a shift amount indicated by e.

According to FIG. 6 and FIG. 7, it is possible to reduce the deviation amount by aligning the phases of the drum driving systems when the heads of the respective colors start exposure so as to be the same phase.

An embodiment of phase matching will be described below.

As is apparent from FIG. 3, each drum 11, 2
1, 31 and 41 rotating shafts 110, 120, 130 and 140
Pulse plates 113, 123, 133 and 14 located at
3 and photo interrupters 114, 124, 134 and
The 144 corresponds to the pulse holes 119 (129, 139 and 149) once per revolution of the drum (that is, the drum, the rotary shaft and the worm wheel are assembled together) as shown in FIG. The pulse is formed so as to be output at a position at a predetermined angle from the exposure position of each recording head.

Therefore, for example, based on the timing when the recording paper P is fed from the aligning roller 58,
The relationship between the reference position signal generated by this reference and the phase of the drum drive system is fixed in structure. From this, the rotary shafts 110, 12 of the drums 11, 21, 31 and 41 are
0, 130 and 140 and each worm wheel 112, 12
The phase shift including the eccentricity of 2, 132 and 142 can be managed as the time until the output from the reference signal and each pulse hole 119, 129, 139 and 149 is obtained.

9 (a) and 9 (b) show the phase relationship of each drum drive system before and after the phases are matched. For comparison with the reference signal, the signal from the photo interrupter corresponding to each drum is also shown.

In FIG. 9A, the exposure timing of each recording head is adjusted as shown in FIG.
It is assumed that t ₁ , t ₂ , t ₃ , and t ₄ seconds have passed since the switch 58 was turned on. In this case, as shown in FIG. 9 (b), the phases of the second drum, the third drum, and the fourth drum are t _x seconds after the photointerrupter signal of the first drum is output, respectively, and t The phases of the respective drums are matched by rotating the second to fourth drums so that the photo interrupter signals of the respective drums are output after _y seconds and t _z seconds. That is, since the dotted line shown in each column of Y, M, C, and Bk in FIG. 9A is the exposure timing, the phase (swell) of each drum is utilized by using the output from each photointerrupter signal. Y of FIG. 9 (b),
It suffices to rotate the second to fourth drums so that the dotted lines shown in the columns M, C, and Bk are equal. In the first and fourth drums, when the fourth drum is used as a reference, the first drum photointerrupter signal may be output t _z ′ seconds after the fourth drum photointerrupter signal is output. .

Referring again to FIG. 3, the color motor 1
01 is the worm gear 111, 1 arranged on the shaft 102
21 and 131 and the respective drums 11, 21 and 31 are driven by worm wheel gears 112, 122 and 132 mounted on respective shafts (rotating shafts) 110, 120 and 130 of the drums. The worm gears 122 and 132 of the second and third drums are electromagnetic clutches, respectively.
125 and 135 coupled to motor shaft 102 to excite electromagnetic clutch 125 (or 135)
It is mechanically coupled to the motor shaft 102 by (on) and released by deenergizing (off). Electromagnetic brakes 126 and 136 are attached to the shafts 120 and 130, respectively, so that the drums 20 and 30 can be stopped at arbitrary positions.

The black motor 103 includes the worm gear 141 arranged on the shaft 104 and the shaft of the fourth drum 40.
The fourth drum is driven via a worm wheel gear 142 attached to 140. Note that neither the electromagnetic clutch nor the electromagnetic brake is attached to the black worm gear.

On the other hand, the transfer belt 51 is a transfer belt motor.
It is wound around a driving roller (supporting roller) 52 driven by 54 and a transfer belt supporting roller 53, and is rotated at a predetermined speed by a motor 54. The photo interrupter 154 and the pulse plate 153 shown in FIG. 8 are mounted on one of the driving roller (supporting roller) 52 and the transfer belt supporting roller 53, similarly to the drums. Also, transfer belt
A mark is provided on the belt 51 so that the reference position of the transfer belt can be determined, and one pulse is output every time the photo interrupter 151 as the reference position signal generator detects the mark.

The photosensitive drums 11, 21, 31 and 41
Peripheral length, transfer belt drive roller 52 and support roller 53
The outer peripheral length and the belt (whole circumference) length of the transfer belt 51 are formed to have an integer ratio to each other. As an example, in the example shown in FIG. 3, each photosensitive drum outer peripheral length: transfer belt driving roller (supporting roller) outer peripheral length: transfer belt belt length = 2: 1: 12.

According to FIG. 1, each drum 11, 21, 31 and
The outputs of the photo interrupters 114, 124, 134 and 144 arranged at 41 are the interrupt ports INTA, INTB, INTC and IN of the main CPU 200 of the control unit 100.
It is connected to TD. Therefore, if the interrupt is permitted, the interrupt is input to the CPU 200 each time the signal from each photo interrupter is output. Also, CPU 2
From 00, start / stop signals for each motor, acceleration /
The deceleration signal and the electromagnetic clutch on / off signal are output,
It is driven at a predetermined timing via the respective drivers 202 and 203. In addition, each electromagnetic clutch 225 and
The on / off signal of 235 is inverted and becomes the on / off signal of the electromagnetic brakes 226 and 236, respectively. When each electromagnetic clutch is on, the corresponding electromagnetic brake is off. The output of the photo interrupter 154 of the transfer belt driving roller 54 is the interrupt port I of the CPU 200.
The output of the photo interrupter 151 of the transfer belt 51 is connected to the NTE and is connected to the interrupt port INTG, respectively, and if interrupts are enabled, each time the signals from the photo interrupters 154 and 151 are output,
The CPU 200 is interrupted.

Referring now to FIGS. 43 and 46, C
The PU 200 rotates the drum motors 101 and 103 and the transfer belt motor 54.

The photo interrupter 114 of the first drum 11
When an interrupt is input to the interrupt port INTA by the output from (STP71), the CPU 200 starts time measurement.
(STP72), transfer belt drive roller 52 (support roller 5
Until the signal of the photo interrupter 154 of 3) is output and an interrupt is input to the interrupt port INTE (STP73)
Measure the time (STP74). This measured time t
The _ae, determined in advance certain value t _g, t _ae = As a t _g (STP75), the drum motor 101 and 103 and the transfer belt motor 54 accelerates or decelerates (STP76). In this case, t
_g = 0, that is, the signals of the photo interrupter 154 may be simultaneously output.

By performing this operation each time before printing is started, the phase of the drum drive system and the phase of the transfer belt drive roller are fixed to a predetermined cycle (STP77).

After the phase is fixed according to FIG. 43, subsequently, FIG. 47 is executed, and the paper is fed according to FIG. 47 (S
TP 101), aligned by aligning roller 58 (S
TP102). After that, the interrupt of the photo interrupter 151 of the transfer belt 51 is permitted, the signal of the photo interrupter is output, and the interrupt is input to the interrupt port INTG (STP 103). At the same time, the aligning motor 158
Rotate (Aligning motor on, STP 104),
Feed the paper to the transfer belt and start printing. The exposure timing of each recording head is controlled with the ON signal of the aligning motor 158 as a reference.Therefore, at the time of printing, each drum is exposed to the same position on each drum and further transferred to the same position on the transfer belt. It That is, STP 105
Through execution of steps 109 to 109, a color image is formed on the paper P.

Next, each image forming section 10 in the adjustment mode,
Phase shift of 20, 30, and 40, undulation of transfer belt 51,
And the belt resulting from the belt support rollers 52 and 53
A method for detecting the rotational irregularity of 51 will be described in detail.

That is, the phase fixing routine of FIG. 4 is executed prior to the printing operation shown in FIG. ST in Figure 4
P1 has shown the operation | movement of FIG. 43 already demonstrated. Therefore, first, the phase alignment of the transfer belt 51, that is, the "waviness" is detected and the phase is fixed (STP1).

Subsequently, the phase of each photosensitive drum drive system is detected (STP2).

Specifically, as shown in FIGS. 37 and 38, any one of the first to fourth image forming units 10, 20, 30 and 40 (here, the Y image forming unit 10 is Is used to generate the reference position signal.
Referring to FIG. 37, at the same time when the Y reference position signal is generated, the aligning motor 158 is turned on and the aligning roller 58 is rotated. A predetermined line is exposed by the Y exposure head 13 t ₁ seconds after the aligning motor 158 is turned on.

Referring to FIG. 38 in detail, after the drum motors 101 and 103 and the belt drive motor 154 are turned on (STP 211) and the repeat counter is reset (STP 212), the first drum is started. When the 11 reference position signals are input to the interrupt port INTA (STP
213) at the same time, the aligning motor is rotated (aligning motor on, STP 214), and exposure is started by the first recording head 13 after t ₁ seconds (STP 215).
Lines in the main scanning direction are printed (marking) (ST
P 216). After the start of exposure, the same line is printed at equal time intervals (t _id ). The line on the photoconductor drum 11 is transferred to the transfer belt 51 at the transfer point and is conveyed to the sensor 59.
Are sequentially detected by (STP 217). The detection principle is shown in FIG. That is, the test pattern exposed by each recording head at a predetermined timing.
The multiple (test lines at regular intervals) are developed by the corresponding developing device, then transferred to the transfer belt 51 by the transfer roller, conveyed by the transfer belt 51, and passed through the sensor 59. ) Deviation is detected.

Specifically, as shown in FIG. 36, the sensor output is tested on the transfer belt 51 by a sensor aperture 59c having a shape shown in FIG. 36B, that is, a notch extending in the main scanning direction. When the pattern is incident, Fig. 36
The output waveform of (c) is output from the sensor 59. The sensor 59 has a sensor aperture 59c located between the detector 59a and the transfer belt 51, as shown in FIG.
The light source 59b and the reflection plate 59d located behind the belt 51.

According to this method, the phase of each drum drive system, which can be measured only by a large-sized image evaluation apparatus as shown in FIG. 33, can be easily detected by a low-cost sensor. The image evaluation device will be briefly described. A microscope 301 including a CCD camera 303 and an automatic X-ray
-Y stage 302, image processing unit 316, storage device 315,
The calculation unit 314, the image output unit 313, the controller 311 including the XY stage controller 312, and the like,
An image taken by a CCD camera is taken into an image processing unit, binarized, etc., and then the density and line interval are calculated to obtain a waveform of an error between lines. The image evaluation device itself is large and expensive. In addition, it cannot be incorporated in an image forming apparatus, and as a result, it is used only for inspection and adjustment before shipping in a factory or the like. Therefore, there is a problem that it is not possible to cope with aging or drum replacement in the environment where the image forming apparatus is used.

The sensor output is input to the + side of the comparator 213 shown in FIG. 35, and the output from the comparator 213 is input to the interrupt port INTF of the CPU 200. The CPU 200 alternately repeats the start and stop of the timers 294 (timer 1) and 298 (timer 2) each time the INTF is interrupted (STP 218).
When the sensor output of the first line is input to INTF, C
PU 200 outputs a timer start signal, starts timer 1, and starts time measurement. When the sensor output of the second line is input to the INTF, the CPU 200 outputs a timer stop signal to stop the timer 1, finish the time measurement, record the measured time in the memory, and then the timer 1
To clear. Since the timer stop signal is the start signal of the timer 2, the timer 1 starts the measurement at the same time when the timer 1 finishes the measurement. Then, when the sensor output of the third line is input to INTF, the CPU 2
00 outputs the timer start signal again, ends the measurement of the timer 2, records the measurement time in the memory, and then clears the timer 2. Since the timer start signal is the stop signal of the timer 2, the timer 2 finishes the measurement, and at the same time, the timer 1 starts the time measurement again (STP 219 to 220).
.

This operation is repeatedly measured up to the final line (repetition of STP 217 to 220), and each obtained time is recorded. The time is recorded in the memory from t _e1 to t _en , and the amount of deviation from the theoretical value is obtained by calculating Er _n = V _p · t _en −V _p · t _id (ST
P 221). However, Er _n represents a deviation amount, and V _p represents a process speed.

Thus, if Er _n is plotted, the first
The phase of the drum drive system is known.

This operation is performed by each of the image forming units 10, 20, 30 and
Performed for each of the 40. The phase detecting operation shown in FIG. 38 may be replaced with the detecting operation shown in FIG. That is, in FIG. 39, the time detection by the timer 1 and the timer 2 is replaced by the time counting by the CPU 200.

Next, as STP3 in FIG. 4, the phases of the respective photosensitive drum drive systems are matched.

FIG. 29 shows the outline of the phase matching routine. That is, based on the phase of the drum drive system of each image forming unit detected by the method in FIG. 38 or FIG. 39, first, the phase of Y = yellow and M = magenta is determined.
(STP51), secondly, the phases of Y = yellow and C = cyan are (STP52), and thirdly, Y = yellow and B.
The phases of k = black (black) (STP53) are respectively matched.

More specifically, as described above, the color motor 101 includes the worm gear 1 via the shaft 102.
11, 121 and 131 and worm wheel gear 112 mounted on the shaft of each color drum 11, 21 and 31
122 and 132 drive each drum 11, 21 and 31. Worm gear 12 of second and third drums 21 and 31
1 and 131 are connected to the motor shaft by electromagnetic clutches 125 and 135 to energize the electromagnetic clutch.
It is mechanically coupled to the motor shaft by turning it on, and the coupling is released by deenergizing it. Also, the shafts 120 of the second and third drums and
Since the electromagnetic brakes 126 and 136 are mounted on the 130, the drums 21 and 31 are stopped at arbitrary positions.

The black motor 103 includes the worm gear 141 arranged on the shaft 104 and the shaft of the fourth drum 41.
The fourth drum is driven via a worm wheel gear 142 attached to 140. No electromagnetic clutch or brake is attached to the black worm gear.

With reference to FIGS. 15 to 19 and FIGS. 22 to 24, the reference position stop routine of the drums 11, 21, 31 and 41 and the phase alignment of the drive system of each drum will be described in detail.

The outputs of the photo interrupters 114, 124, 134 and 144 of the drums 11, 21, 31 and 41 are output by the CPU.
If 200 are connected to the interrupt ports INTA, INTB, INTC, and INTD, and interrupts are enabled, the CPU 200 is interrupted each time the signal of each photo interrupter is output.

As shown in FIG. 22, a large flow for phase adjustment is as follows: the third (C) and second (M) drum 31
And 21 are stopped at the reference position, and the third and second electromagnetic clutches 135 and 125 are turned off (STP32). At this time, at the same time, the corresponding electromagnetic brakes 126 and 136 are turned on to hold the positions of the drums. Then the first
The phases of the (Y) and fourth (Bk) drums are aligned (S
TP33), and then the phases of the second and third drums are sequentially aligned (STP34 and 35).

More specifically, as shown in FIG. 23, first, the second and third electromagnetic clutches 125 and 135 are turned on to connect the color motor 101 and the second and third worm gears 121 and 131. The second and third drums
Allow 21 and 31 to rotate (STP 121).

Next, the color drum motor 101 is started to rotate the drums 21 and 31 (STP 122).
. Then, the CPU 200 is enabled to interrupt (STP 12
5) When the signal from the third drum photo interrupter 134 is input to the interrupt port INTC, the clutch 135 is turned off to stop the third drum (STP 126). Similarly, the second drum is also stopped at the reference position (STP 127
And 128).

Subsequently, as shown in FIG. 17, the first
(Y) Drum and 4th (Bk) drum are in phase.
That is, the fourth drum photo interrupter signal is output t _z seconds after the first drum photo interrupter signal is output, or t _z ′ seconds after the fourth drum photo interrupter signal is output. The first drum photo interrupter signal may be output.
(See STP 151-154, FIGS. 9 and 10).

Specifically, as shown in FIG. 24, the CPU
200 is a color drum motor 101, a black drum motor 103
Is rotated, the time measurement is started by the interrupt signal input first, and the time measurement is ended by the interrupt signal input later (STP41 to 44). When INTA comes first, each motor is accelerated / decelerated and adjusted so that the measurement time becomes t _z seconds. If INTB comes first, each motor is accelerated and decelerated so that the measurement time becomes t _z ′ seconds and adjustment is performed (STP45
~ 46).

Next, the phase of the second drum is adjusted. Figure
As shown in 15, when an interrupt enters the interrupt port INTA (STP 131), the time is measured (STP 13
2) At time t _x seconds (STP 133), turn on the electromagnetic clutch of the second drum to rotate the second drum.
(STP 134).

Finally, the third drum is similarly phase-matched (FIG. 16, STP 141 to 144).

In this case, the first to third drums 11 and 21
For and 31, the second and third electromagnetic clutches 1
Since the phase relationship is fixed unless 25 and 135 are turned off, it is not necessary to perform the phase adjustment for each print, and only the first drum 11 and the fourth drum 31 need to be phase adjusted for each print.

When the phases in the image forming sections are matched, as shown in FIG. 18, the paper P is fed from the cassette 55 (STP61) and aligned by the aligning roller 58 (STP62). After that, when the interrupt of the signal of the photo interrupter 114 of the first drum 11 is enabled and the interrupt signal is input to the interrupt port INTA (ST
In (P63), the aligning motor 158 is rotated (aligning motor on, STP64), the paper is fed to the transfer belt, and printing is started (STP65). Since the exposure timing of each recording head is controlled with the aligning motor ON signal as a reference, when printing, the exposure is performed at the same position of the phased drum (STP 66 to 68).

Prior to this printing operation (STP61-68), the correction amount for each drum is averaged by STP4 and STP5 shown in FIG. It goes without saying that the printing conditions for each color component are changed according to the degree of eccentricity of the belt.

Next, a phase shift detection method and phase matching for a drive device different from the drive device shown in FIG. 3 will be described.

FIG. 11 shows a form in which three of the first, second and third drums are driven by color motors, and the fourth drum is driven by a black motor.

The color motor 101 includes worm gears 111, 121 and 131 connected to the shaft 102 and shafts 110, 120 and 130 of the color drums 11, 21 and 31, respectively.
The drums 11, 21 and 31 are driven by worm wheel gears 112, 122 and 132 attached to the drums. The black motor 161 is a motor whose speed cannot be changed, and a motor substantially similar to the motor 101 is used. Therefore, according to FIG. 12, two sets of the motor driver 202 and the black driver 261 are prepared, but one set may be represented.

The worm gears 121 and 131 of the second and third drums 21 and 31 have electromagnetic clutches 125 and 1
35 is coupled to the shaft 102 by mechanical engagement with the shaft 102 by energizing (on) the respective electromagnetic clutches 125 and 135, and released (uncoupled) by deenergizing (off). It

The shafts of the second and third drums
Electromagnetic brakes 126 and 136 are attached to 120 and 130 so that the drums 21 and 31 can be stopped at arbitrary positions. The shafts 110, 120 and 1 of each drum
30 includes pulse plates 113, 123 and 123 shown in FIG.
133 and photo interrupters 114, 124 and 13
4 is installed.

On the other hand, an electromagnetic brake 146 is attached to the shaft 140 of the drum of the fourth drum (black) 41,
The drum 41 can be stopped at any position. A pulse plate 143 shown in FIG. 8 and a photo interrupter 144 are attached to the shaft 140 of the drum, as in the second and third color drums.

According to FIG. 12, the outputs of the photo interrupters 114, 124, 134 and 144 of each drum are the CPU 200
Connected to the interrupt ports INTA, INTB, INTC, and INTD of, and if interrupts are enabled, CP is output each time a photointerrupter signal is output.
An interrupt occurs at U 200. Further, the CPU 200 outputs the start / stop signals of the respective motors and the ON / OFF signals of the electromagnetic clutch, and the respective drivers 202 and
Driven at 261. Further, the ON / OFF signal of the electromagnetic clutch is inverted and becomes an ON / OFF signal of the electromagnetic brake, and when each electromagnetic clutch is ON, the electromagnetic brake corresponding to it is OFF.

Referring to FIG. 13, the large flow for phase matching is as follows: the second, third and fourth drums 21, 31 and
41 is the position at which the signals of the photo interrupters 124, 134 and 144 are output (hereinafter referred to as the reference position),
Turn off the third and second electromagnetic clutches 145, 135 and 125. At this time, the electromagnetic brakes 146, 136 and
126 are turned on at the same time and the position of each drum is retained
(STP12). Then the first and second drums 11 and 2
The phase of 1 is aligned (STP13), then the phases of the first and third drums 11 and 31 (STP14), and the phases of the first and fourth drums 11 and 41 are sequentially aligned.
(STP15).

Specifically, as shown in FIG. 14, all the electromagnetic clutches are turned on, the motor shaft and the worm gear are coupled, and the drum is made rotatable (STP21). Then, the drum motors 101 and 161 are started to rotate the drums (STP22). Next, the interrupt is enabled, and the signal of the photo interrupter 144 of the fourth drum is changed to C.
If it is input to PU 200 (STP23), the 4th drum is stopped and the electromagnetic clutch is turned off at the same time (STP24).
. Similarly, the third drum 31 and the second drum 21
And stop in order (STP25-28). That is, the second,
The third and fourth drums 21, 31, and 41 are respectively
Stopped at the reference position.

Subsequently, as shown in FIG. 17, the phases of the first drum 11 and the fourth drum 41 are matched. The fourth drum time t _z after the first drum photo interrupter signal is output,
The drum photo interrupter signal may be output. When the first drum photo interrupter signal is output, an interrupt is input to the interrupt port INTA of the CPU. When an interrupt signal is input, the CPU starts measuring time, and when t _z seconds have elapsed, the fourth drum electromagnetic clutch is turned on and the worm gear is connected to the motor shaft. Since the drum motor is still rotating, the 4th drum is the 1st
It rotates with a phase difference of t _z seconds from the drum.

Next, as shown in FIG. 15, the phase of the second drum is matched. This is the same as the fourth drum, CPU
When an interrupt signal is input to INTA of, the time measurement starts, and when t _x seconds elapse, the electromagnetic clutch of the second drum is turned on,
Rotate the second drum. Finally, as shown in FIG. 16, the third drum is phase matched as well. This matches the phase of all drums. The electromagnetic clutches for the first, second and third drums 11, 21 and 31 are
Since the phase relationship is fixed unless 125 and 135 are turned off, only the first and fourth phase adjustments need to be adjusted for each print.

When the phase adjustment is completed, printing is performed along the line of FIG. 18 as in the example of FIG. 3 described above. In addition,
In this configuration, the phase of the group of color drums 11, 21 and 31 and the black drum 41 can be matched, but the phase of each color drum remains fixed.

Next, a phase shift detection method and phase matching for a drive device different from the drive device shown in FIG. 3 will be described.

In the example shown in FIG. 20, the color motor 101 includes a worm gear 111, 1 via a shaft 102.
21 and 131 and worm wheel gears 112, 122 and 132 mounted on the shafts of each color drum 11, 21 and 31 drive each drum 11, 21, and 31. The worm gears 121 and 131 of the second and third drums 21 and 31 are connected to the motor shaft by electromagnetic clutches 125 and 135, and are mechanically connected to the motor shaft by exciting (turning on) the electromagnetic clutch. The binding is solved by solving (off).
Also, the shafts 120 and 1 of the second and third drums
Since the electromagnetic brakes 126 and 136 are mounted on the drum 30, the drums 21 and 31 are stopped at arbitrary positions.

The black motor 103 includes the worm gear 141 arranged on the shaft 104 and the shaft of the fourth drum 41.
The fourth drum is driven via a worm wheel gear 142 attached to 140. Neither the electromagnetic clutch nor the electromagnetic brake is attached to the black worm gear.

Referring to FIG. 21, each drum 11, 21, 31
And 41 photo interrupters 114, 124, 134 and
The output of 144 is the interrupt port INTA of the CPU 200,
Connected to INTB, INTC and INTD,
If the interrupt is permitted, the CPU 200 is interrupted each time the signal of each photo interrupter is output.
Start / stop signal of each motor, acceleration / deceleration signal,
The C and INT / OFF signals of the electromagnetic clutch are output,
It is driven by respective drivers 202 and 203. Further, the ON / OFF signal of the electromagnetic clutch is inverted and becomes an ON / OFF signal of the electromagnetic brake, and when each electromagnetic clutch is ON, the electromagnetic brake corresponding to it is OFF.

As shown in FIG. 22, a large phase matching flow is as follows: the third (C) and second (M) drum 31
And 21 are stopped at the reference position, and the third and second electromagnetic clutches 135 and 125 are turned off (STP32). At this time, at the same time, the corresponding electromagnetic brakes 126 and 136 are turned on to hold the positions of the drums. Then the first
The phases of the (Y) and fourth (Bk) drums are aligned (S
TP33), and then the phases of the second and third drums are sequentially aligned (STP34 and 35).

More specifically, as shown in FIG. 23, first, the second and third electromagnetic clutches 125 and 135 are turned on to connect the color motor 101 and the second and third worm gears 121 and 131. Then, the second and third drums 21 and 31 are made rotatable (STP 121).

Next, the color motor 101 is started to rotate the drums 21 and 31 (STP 122).
Then, enable interrupt to CPU 200 (STP 125)
When the signal of the third drum photo interrupter 134 is input to the interrupt port INTC, the clutch 135 is turned off to stop the third drum (STP 126). Similarly, the second drum is also stopped at the reference position (STP 127 and 128).

Then, as shown in FIG. 24, the first
(Y) Drum and 4th (Bk) drum are in phase.
That is, the fourth drum photo interrupter signal is output t _z seconds after the first drum photo interrupter signal is output, or t _z ′ seconds after the fourth drum photo interrupter signal is output. The first drum photo interrupter signal may be output.
(See STP 151-154, FIGS. 9 and 10).

Specifically, as shown in FIG. 24, the CPU
200 rotates the color motor 101 and the black drum motor 103, starts the time measurement with the interrupt signal input earlier, and finishes the time measurement with the interrupt signal input later (STP41 to 44). When INTA comes first, each motor is accelerated / decelerated and adjusted so that the measurement time becomes t _z seconds. When INTB comes first, each motor is accelerated and decelerated so that the measurement time is t _z ′ seconds and adjustment is performed (STP45 to 46).
.

Next, the phases of the second drum 21 and the third drum 31 are matched according to the routines shown in FIGS.

At the time when the phases are matched, the image is printed on the paper P according to the routine shown in FIG.

Next, a method of detecting a phase shift and a phase adjustment for a drive device different from the drive device shown in FIG. 3 will be described.

According to FIG. 25, all the photosensitive drums 11, 2 are
1, 31 and 41 are driven by one motor 101. In this type, since all the drums are mechanically connected by worm gears and worm wheel gears, the phase relationship of each drum drive system is fixed. , The mechanical connection is released.

In the example shown in FIG. 25, the drum motor
101 is a worm gear 111 connected to the shaft 102,
121, 131 and 141 and shafts 110, 1 of each drum
Drives the drum through worm wheel gears 112, 122, 132 and 142 mounted on 20, 130 and 140.

Worm gears 111, 121, 131 of each drum
And 141 are electromagnetic clutches 115, 125, 1 respectively.
Connected to shaft 102 by 35 and 145,
By exciting (turning on) each electromagnetic clutch, the shaft 102 and the corresponding gear are mechanically coupled, and
It is released by releasing the excitation (off).

Electromagnetic brakes 116, 126, 136 and 146 are mounted on the shafts of the drums, respectively, so that the drums can be stopped at arbitrary positions. In addition,
The shafts 110, 120, 130 and 140 of each drum are
Similar to the example shown in FIG. 8, pulse plates 113, 123, 133 and 143 and photo interrupters 114, 124, 134 and 144 are attached.

Referring to FIG. 26, the outputs of the photo interrupters 114, 124, 134 and 144 arranged on the shafts of the drums are output from the interrupt port INT of the CPU 200.
Photo interrupter if connected to A, INTB, INTC and INTD and interrupts are enabled
Each time the signals from 114, 124, 134 and 144 are output, the CPU 200 is interrupted. Further, the CPU 200 outputs a motor start / stop signal and an electromagnetic clutch on / off signal, which are driven by a driver. Also, the on / off signal of the electromagnetic clutch is inverted,
An electromagnetic brake on / off signal is generated, and when each electromagnetic clutch is on, the corresponding electromagnetic brake is off.

A large flow of phase matching is the same as the routine of FIG. 13 already described, and therefore detailed description will be omitted. That is, after all the drums are stopped at the reference position along FIG. 14, the phase of the fourth drum is aligned along FIG. 17, and the second and the following phases are aligned along FIG. 15 and FIG. The phase of the third drum is aligned.

Next, a method of detecting a phase shift and a phase matching for a driving device different from the driving device shown in FIG. 3 will be described.

FIG. 27 shows an example in which each drum is directly driven by a dedicated motor.

The respective drums 11, 21, 31 and 41 are independently driven by dedicated drum motors 117, 127, 137 and 147 directly connected to the respective drum shafts 110, 120, 130 and 140. The shaft of each drum has a pulse plate 113, similar to the example shown in FIG.
123, 133 and 143 and photo interrupter 114,
124, 134 and 144 are installed.

Referring to FIG. 28, the outputs from the photo interrupters 114, 124, 134 and 144 arranged on the respective drums are the interrupt ports INTA, I of the CPU 200.
If it is connected to NTB, INTC and INTD and interrupts are enabled, the photo interrupter 114,
Each time the signals from 124, 134 and 144 are output,
The CPU 200 is interrupted.

Further, the CPU 200 outputs a start / stop signal, an acceleration signal and a deceleration signal to the drivers 221, 222, 223 and 224 of the respective motors.

Specifically, as shown in FIG. 30, the first and second drum motors 117 and 127 are started, and the first and second drums 11 and 21 are rotated.
(STP511). Then allow interrupts, first drum
11 photo interrupter 114 signal is interrupt port I
When input to NTA (STP 512), CPU 200
Time measurement is started (STP 513), and the output signal of the photo interrupter 124 of the second drum is the interrupt port INT.
At the time of inputting to B (STP 514), the time measurement is ended (STP 515). The second (M) drum motor 127 is accelerated and decelerated so that this measurement time t _MM becomes t _x (ST
P 516-517).

Next, as shown in FIG. 31, the third drum motor 137 is started to rotate the third drum.
(STP 521). Similarly, when the signal of the photo interrupter 114 of the first drum 11 is input to the interrupt port INTA (STP 522), the CPU starts time measurement.
(STP 523) Then, the photo interrupter of the third drum 31.
When the output signal of 134 is input to the interrupt port INTC (STP 524), the time measurement is finished. The third drum motor 137 is accelerated and decelerated so that this measurement time t _MC becomes t _y (STP 526 to 527).

Finally, as shown in FIG. 32, the fourth drum motor 147 is started to rotate the fourth drum (STP 531). Similarly, when the signal of the photo interrupter 114 of the first drum is input to the interrupt port INTA (STP 532), the CPU 200 starts time measurement (STP 533) and the photo interrupter of the fourth drum 41 is started. When the 144 output signal is input to the interrupt port INTD (STP534), the time measurement ends.
(STP 535). The fourth drum motor is accelerated and decelerated so that this measurement time t _MK becomes t _z (STP 536 to 53).
7).

When the phases are matched, the image is printed and the paper P is printed in accordance with the routine shown in FIG.
Overlaid on top.

In FIG. 40, in comparison with the device shown in FIG.
An example in which the photo interrupter 151 of the transfer belt 51 is removed and all the drums 11, 21, 31 and 41 are driven by one motor 101 is shown.

In the example shown in FIG. 40, the transfer belt 51
Transfer roller drive roller 52 (support roller 53) that drives the drive roller 1 rotation cycle (hereinafter referred to as transfer belt drive roller phase) color misalignment due to eccentricity, and transfer belt 51 itself thickness unevenness cause belt 1 rotation cycle (Hereinafter, belt phase)
The transfer belt drive roller phase can be removed from the color misregistration.

According to FIGS. 41 to 43, the first drum 11
When a signal is output from the photo interrupter 114 of the above and an interrupt is input to the interrupt port INTA (STP71), C
The PU 200 starts time measurement (STP72), and the photo interrupter of the transfer belt driving roller 52 (supporting roller 53).
Measure the time (STP73) until the 154 signal is output and the interrupt is input to the interrupt port INTE (STP73).
74). The measured time t _ae is set to a certain value t _g in advance, and the drum motors 101 and 103 and the transfer belt motor 54 are accelerated and decelerated so that t _ae = t _g (STP75).
(STP76).

The drum motor 101 includes worm gears 111, 121, 131 and 141 arranged on the shaft 102 and worm wheel gears 112, 122, 132 and 142 mounted on the shafts 110, 120, 130 and 140 of the respective drums. Drive each drum through. The shaft of each drum has pulse plates 113, 123, 133 and 143 shown in FIG. 8 and photo interrupters 114, 124, 134.
And 144 are placed.

The pulse plates 113, 123, 133 and 1
43, and photo interrupters 114, 124, 134 and
The 144 need only be located on one set of drums (image forming station) in this example. Here, the photo interrupter 114 of the first drum 11 is used.

The outer peripheral length of the photosensitive drum and the outer peripheral length of the transfer belt driving roller are formed in an integer ratio. Here, the outer peripheral length of the photosensitive drum: the outer peripheral length of the transfer belt drive roller =
2: 1

According to FIG. 41, the output of the photo interrupter 114 of the first drum 11 is the interrupt port I of the CPU 200.
If it is connected to the NTA and interrupts are enabled, the CPU 200 is interrupted each time a signal is output from the photo interrupter 114. Further, the photo interrupter 154 of the transfer belt driving roller 52 is a CPU
If it is connected to the interrupt port INTE of 200, and interrupts are enabled, the CPU 200 is interrupted each time a signal is output from the photo interrupter 154.

On the other hand, since the CPU 200 outputs the start / stop signal of the transfer belt motor 54, the acceleration signal, and the deceleration signal to the transfer belt motor driver 254, the transfer belt motor 54 is
Driven at 254. Similarly, the drum motor 101
The start / stop signal of, the acceleration signal, and the deceleration signal are output to the drum motor driver 201, and the drum motor 101
Are driven by the drum motor driver 201.

According to FIGS. 42 and 43, first, the CPU 200
Rotates the drum motor 101 and the transfer belt motor 54.

The photo interrupter 114 of the first drum 11
When an interrupt is input to the interrupt port INTA by the output from (STP71), the CPU 200 starts time measurement.
(STP72), transfer belt drive roller 52 (support roller 5
Until the signal of the photo interrupter 154 of 3) is output and an interrupt is input to the interrupt port INTE (STP73)
Measure the time (STP74). This measured time t
The _ae, determined in advance certain value t _g, t _ae = As a t _g (STP75), the drum motor 101 and 103 and the transfer belt motor 54 accelerates or decelerates (STP76). In this case, t
_g = 0, that is, the signals of the photo interrupter 154 may be simultaneously output.

By performing this operation each time before printing is started, the phase of the drum drive system and the phase of the transfer belt drive roller are fixed to a predetermined cycle (STP77).

Hereinafter, similar to the other embodiments already described,
An image is formed according to the flow shown in FIG. Figure 44
Compared to all the drums 11, 2 compared to the device shown in FIG.
An example is shown in which 1, 31, and 41 are driven by one motor 101.

That is, in the example shown in FIG. 44, the thickness unevenness of the transfer belt 51 itself and the transfer belt drive roller 53 (52)
The color misregistration of one belt rotation cycle (hereinafter, belt phase) caused by the phase of can be removed.

Referring to FIGS. 43, 45 and 46, the first
When an interrupt is input to the interrupt port INTA by the output from the photo interrupter 114 of the drum 11 (STP71)
, The CPU 200 starts time measurement (STP72), the signal of the photo interrupter 154 of the transfer belt drive roller 52 (support roller 53) is output, and the interrupt port INTE is output.
The time of (STP73) until an interrupt occurs
(STP74). This measured time t _ae is set to a predetermined value t
_The drum motors 101 and 103 and the transfer belt motor 54 are accelerated and decelerated (STP76) so that t _ae = t _g (STP75). In this case, t _g = 0, that is,
The signals of the photo interrupter 154 may be output at the same time.

By performing this operation each time before printing is started, the phase of the drum drive system and the phase of the transfer belt drive roller are fixed to a predetermined cycle (STP77).

After the phase is fixed according to FIG. 43, the process shown in FIG. 47 is executed and the paper is fed according to FIG. 47 (S
TP 101), aligned by aligning roller 58 (S
TP102). After that, the interrupt of the photo interrupter 151 of the transfer belt 51 is permitted, the signal of the photo interrupter is output, and the interrupt is input to the interrupt port INTG (STP 103). At the same time, the aligning motor 158
Rotate (Aligning motor on, STP 104),
Feed the paper to the transfer belt and start printing. The exposure timing of each recording head is controlled with the ON signal of the aligning motor 158 as a reference.Therefore, at the time of printing, each drum is exposed to the same position on each drum and further transferred to the same position on the transfer belt. It That is, STP 105
Through execution of steps 109 to 109, a color image is formed on the paper P.

Hereinafter, similar to the other embodiments already described,
An image is formed according to the flow shown in FIG.

[0139]

As described above, according to the image forming apparatus of the present invention, the photoconductor drums arranged for each color component, the drive mechanism for driving the photoconductor drums, and the image formed on each photoconductor drum. The eccentricity of either the conveyor belt that conveys the belt or the belt roller that rotates the conveyor belt,
Calculated by detecting the position of the test pattern formed on the conveyor belt, and the timing of urging each drive mechanism and belt roller to minimize the phase shift due to the eccentricity of each drive mechanism and belt roller. By changing, the color shift of the output image can be minimized.

According to this method, for example, in a transfer type image forming apparatus such as a color laser printer,
Even if the phase relationship of the drum drive system changes due to aging, drum replacement, or developing device replacement,
It is possible to provide an image forming apparatus having no color misregistration by adjusting the optimum phase relationship.

This can significantly reduce the adjustment process required for the adjustment work at the time of factory shipment.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an image forming apparatus corresponding to a most preferred embodiment of the present invention.

FIG. 2 is a sectional view showing an example of a color image forming apparatus in which an embodiment of the present invention is incorporated.

FIG. 3 is a first example suitable for the image forming apparatus shown in FIG.
FIG.

FIG. 4 is a flowchart for explaining the first embodiment shown in FIG.

FIG. 5 is a diagram for explaining color misregistration due to angular velocity fluctuation.

FIG. 6 is a diagram for explaining color misregistration due to a phase relationship of a drum.

FIG. 7 is a diagram for explaining color misregistration due to a phase relationship of a drum.

FIG. 8 is a diagram for explaining a photo interrupter.

FIG. 9 is a diagram for explaining phase matching of a drum.

FIG. 10 is a timing chart for explaining the exposure timing of the first embodiment shown in FIG.

11 is a schematic perspective view showing a second embodiment suitable for the image forming apparatus shown in FIG.

12 is a schematic block diagram of an image forming apparatus corresponding to the second embodiment shown in FIG.

FIG. 13 is a flowchart showing an example of a phase matching routine.

FIG. 14 is a flowchart showing an example of a reference position stop routine.

FIG. 15 is a flowchart showing an example of an M phase adjustment routine.

FIG. 16 is a flowchart showing an example of a Y phase adjustment routine.

FIG. 17 is a flowchart showing an example of a Bk phase adjustment routine.

FIG. 18 is a flowchart showing an example of a print routine.

FIG. 19 is a timing chart for explaining the exposure timing of the second embodiment shown in FIG.

20 is a schematic perspective view showing a third embodiment suitable for the image forming apparatus shown in FIG.

21 is a schematic block diagram of an image forming apparatus corresponding to the third embodiment shown in FIG.

FIG. 22 is a flowchart showing an example of a phase matching routine.

FIG. 23 is a flowchart showing an example of a reference position stop routine.

FIG. 24 is a flowchart showing an example of a Bk phase adjustment routine.

FIG. 25 is a schematic perspective view showing a fourth embodiment suitable for the image forming apparatus shown in FIG.

FIG. 26 is a schematic block diagram of an image forming apparatus corresponding to the fourth embodiment shown in FIG.

FIG. 27 is a schematic perspective view showing a fifth embodiment suitable for the image forming apparatus shown in FIG.

28 is a schematic block diagram of an image forming apparatus corresponding to the fifth embodiment shown in FIG.

FIG. 29 is a flowchart showing an example of a phase matching routine.

FIG. 30 is a flowchart showing an example of a phase matching routine.

FIG. 31 is a flowchart showing an example of a phase matching routine.

FIG. 32 is a flowchart showing an example of a phase matching routine.

FIG. 33 is a schematic diagram of an image evaluation apparatus that has been conventionally used.

FIG. 34 is a schematic diagram showing a phase shift detection principle (sixth embodiment).

35 is a schematic block diagram for detecting a phase shift based on the detection principle shown in FIG. 34.

FIG. 36 is a schematic diagram for explaining a sensor for detecting a phase shift based on the detection principle shown in FIG. 34, a test pattern, an aperture shape, and a sensor output.

FIG. 37 is a timing chart for explaining the seventh embodiment shown in FIG. 40.

FIG. 38 is a flowchart for explaining a phase detection routine.

FIG. 39 is a flowchart for explaining a phase detection routine.

FIG. 40 is a schematic perspective view showing a seventh embodiment suitable for the image forming apparatus shown in FIG.

41 is a schematic block diagram of an image forming apparatus corresponding to the seventh embodiment shown in FIG.

42 is a timing chart for explaining the exposure timing of the seventh embodiment shown in FIG.

FIG. 43 is a flowchart for explaining a phase detection routine.

44 is a schematic perspective view showing an eighth embodiment suitable for the image forming apparatus shown in FIG.

45 is a schematic block diagram of an image forming apparatus corresponding to the eighth embodiment shown in FIG. 44.

46 is a timing chart for explaining the exposure timing of the eighth embodiment shown in FIG. 44.

FIG. 47 is a flowchart illustrating a print routine.

[Explanation of symbols]

10, 20, 30, 40 ... Image forming unit 11, 21, 31,
41 ... Photosensitive drum 12, 22, 32, 42 ... Charging roller 13, 23, 33,
43 ... Solid head 14, 24, 34, 44 ... Developing device 15, 25, 35,
45 ... Transfer roller 16, 26, 36, 46 ... Cleaner 51 ... Transfer belt (transfer material support) 52, 53 ... Transfer belt drive roller (support roller) 54 ... Transfer belt motor 55 ... Cassette 56 ... Paper feed roller 57 ... Conveying roller 58 ... Aligning roller 59 ... Sensor 59a ... Sensor 59b ... Lamp 59c ... Sensor aperture 59d ... Reflector 60 ... Fixing device 63 ... Belt cleaner 100 ... Control section 101, 103, 16
1… Motor 102, 104… Shaft 110, 120, 130, 140… Drum shaft 111, 121, 13
1, 141… Worm gear 112, 122, 132, 142… Worm wheel gear 113, 123, 133, 143… Pulse board 114, 124, 134, 144… Photo interrupter 115, 125, 13
5, 145 ... Electromagnetic clutch 116, 126, 136, 146 ... Electromagnetic brake 119, 129, 13
9, 149… Pulse holes

Claims (3)

[Claims] 1. A first rotation driving means for rotating a first image carrier, a second rotation driving means for rotating a second image carrier, and the first and second image carriers. Based on the position of the image detected by the detecting means for detecting the image conveyed by the conveying means, the conveying means for holding and conveying the formed image, the first rotation Calculation means for calculating the image shift due to eccentricity of the drive means and the second rotation drive means, and the timing for energizing the second rotation drive means is changed based on the calculation result of this calculation means. An image forming apparatus having a changing unit. 2. A first rotation drive means for rotating the first image carrier, a second rotation drive means for rotating the second image carrier, and the first and second image carriers. Conveying means for holding and conveying the formed image, third rotation driving means for rotating the conveying means, detecting means for detecting the image conveyed by the conveying means, and detecting means for detecting the image. And a calculating means for calculating the image shift due to the eccentricity of each of the first rotation driving means, the second rotation driving means and the third rotation driving means, based on the position of the image, After changing the timing of energizing the third rotation drive means based on the calculation result,
An image forming apparatus including: a changing unit that changes a timing of urging the second rotation driving unit. 3. A first rotation driving means for rotating the first image carrier, a second rotation driving means for rotating the second image carrier, and the first and second image carriers. Conveying means for holding and conveying the formed image, third rotation driving means for rotating the conveying means, detecting means for detecting the image conveyed by the conveying means, and outer periphery of the conveying means. Second detection means for detecting displacement, and based on the position of the image detected by the detection means, the first rotation drive means, the second rotation drive means, and the third rotation drive means, respectively. A calculating means for calculating the image shift due to the eccentricity and calculating the image shift due to the displacement of the outer circumference of the conveying means detected by the second detecting means from the calculated eccentricity, and the calculating means of the calculating means. Based on the calculation result, After changing the timing of energizing the third rotation drive means,
An image forming apparatus including: a changing unit that changes a timing of urging the second rotation driving unit.