JPH11202715A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device forming a correct image by controlling the rotation driving of a photoreceptor drum or the recording timing of a recording head in response to the decentering of the photoreceptor drum. SOLUTION: An image forming unit 30 is constituted by integrally assembling a developing unit 30-1 and a drum unit 30-2 with a unit frame 30-3 and fixed by being attached to the unit receiving parts 33a and 33b of a main device body 1. A mark member 36 having a fan-shaped bar code is stuck to the prescribed position of a flange 345 forming the end surface of the photoreceptor drum 9. Then, the information of the bar code is detected by a sensor 41 disposed at the receiving part 33b through a detection hole 37 formed at a measurement reference position. A constant for driving the motor 58 of the drum 9 is included in the information of the bar code. By controlling a motor driving circuit 54' based on the information, the rotation driving of the respective drums 9 is controlled every drum by a CPU 51 so as to compensate the eccentric characteristic thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for properly controlling image formation in accordance with the eccentricity of a drum gear or an image carrier drum.

[0002]

2. Description of the Related Art Conventionally, there has been known an electrophotographic image forming apparatus (printer apparatus) that prints on recording paper in accordance with print information output from a host device such as a host computer. This printer device includes an image forming unit including an initialization charger, a recording head, a developing device, a transfer device, and the like around a photosensitive drum. This image forming unit uniformly charges the surface of the photosensitive drum by the initialization charger,
An optical latent image is formed on the surface of the charged photosensitive drum by optical writing according to print information by a recording head, and the electrostatic latent image is visualized by a developing device containing toner. The toner image is transferred to recording paper by a transfer device. The recording paper on which the toner image has been transferred is
The sheet is conveyed downstream of the image forming unit, where the toner image is heat-fixed by a fixing device, and is discharged outside the apparatus.

Printers for recording full-color images are roughly classified into a single drum type having only one photosensitive drum and a tandem type having a plurality of photosensitive drums in multiple stages. The single drum type is M (magenta: red dye) which is a subtractive primary color for one page of paper.
Toner (Y: yellow: yellow), C (cyan: greenish blue), and K (black: black) toner dedicated to characters and black printing. Since printing (image formation) processing is individually performed for each toner in order to transfer images in a superimposed manner, the printing process is repeated four times for one page of paper, so that the printing process requires a long time.

[0004] On the other hand, the tandem type has a processing speed almost four times that of the single drum type because the above-mentioned four types of toners are sequentially superimposed and transferred onto paper in one process. ing. For this reason, in recent years, tandem-type color printer apparatuses have been frequently used. In such a tandem-type full-color printer, the above-described image forming sections are formed around the multi-stage photosensitive drums.

[0005] In the above recording head, the main scanning direction of recording scanning (the width direction of the photosensitive drum, ie, the width direction of the recording paper)
Are provided with a number of light emitting elements arranged in a line. This recording head has approximately 2,000 light emitting elements in the case of a printer capable of printing on A4 size paper in the vertical direction at a printing density of 240 dpi (dots / inch), for example. Further, for example, when the printing density is 30
In the case of 0 dpi, about 2500 light emitting elements are provided. A pulse voltage according to print information output from the host device is applied to each of the light emitting elements, and the light emission of the individual light emitting elements is selectively controlled.

By the way, if the rotation axis of the photosensitive drum is eccentric, even if the cross section of the circumferential surface of the photosensitive drum is a perfect circle, and the rotation speed (rotational angular speed) of the photosensitive drum is constant. The peripheral linear velocity at which the photosensitive drum rotates fluctuates at a constant phase. That is, uneven feeding occurs.

On the other hand, as described above, the interval between the light emitting elements of the recording head (interval and pitch of printing pixels) is extremely fine, typically 300 to 400 dots per inch as described above. If there is unevenness, a stable latent image cannot be formed on the peripheral surface. In particular, in the formation of a color image, the images on the four photosensitive drums are overlaid on the paper surface. If the image dot positions of the respective colors do not match, unevenness will occur in the overlapping of the correct colors. Quality images cannot be obtained.

For this reason, in the tandem type image forming apparatus, high precision is required for the photosensitive drums in order to match the image forming timings of the four photosensitive drums.
High accuracy is also required for the bearing member. Further, the gear for transmitting the rotation drive to the photosensitive drum also requires the accuracy of the rotation center and the feeding accuracy for each tooth. Since such a high precision of the gear cannot be sufficiently obtained by a normal molded product or a sintered product, the precision is increased by adding a gear cutting process.

[0009]

In the process of increasing the dimensional accuracy of the member, the cost increases exponentially according to the required accuracy. On the other hand, since there is a limit in the manufacturing accuracy of any member, the photosensitive drum and its driving system gear always involve mechanical dimensional errors when viewed microscopically. ing. That is, in any case, it is impossible to avoid minute eccentricity of the rotating shaft.

[0010] The object of the present invention is to solve the above-mentioned conventional problems.
An object of the present invention is to provide an image forming apparatus that forms a correct image by controlling the rotation drive of the photosensitive drum or the recording timing of the recording head in accordance with the eccentricity of the photosensitive drum.

[0011]

The structure of the image forming apparatus of the present invention will be described below. First, an image forming apparatus according to the first aspect of the present invention is an image forming apparatus comprising: an image carrier drum exchangeably disposed on an apparatus main body; and an optical writing unit for performing optical writing on the image carrier drum in accordance with image information. A toner image developing means for converting a record written by the optical writing means into a toner image, and a transfer material to be brought into contact with the image carrier drum for carrying the toner image developed by the toner image developing means. What is claimed is: 1. An image forming apparatus, comprising: at least a conveying unit; and a transfer unit disposed to face the image carrier drum and transferring the toner image on the image carrier drum to the transfer material conveyed by the conveying unit. A notification member provided on the image carrier drum for notifying rotation information of the image carrier drum, and a transmission unit for transmitting rotation information of the image carrier drum by the notification member to the apparatus main body; Recognition means for recognizing the rotation phase of the image carrier drum based on the rotation information transmitted from the transmission means, and the image carrier drum based on the rotation phase of the image carrier drum recognized by the recognition means It is provided with a rotation modulation control means for modulating the rotation of.

The image carrier drum is rotated based on the rotation phase of the image carrier drum recognized by the recognition means in synchronization with the modulation control by the rotation modulation control means. The optical writing modulation control means for modulating the optical writing timing by the optical writing means.

According to a third aspect of the present invention, the notification means is configured to include eccentricity information of the drum gear as the eccentricity information of the image carrier drum. The eccentricity amount and the eccentricity peak point information are reported as the eccentricity information of the carrier drum. The apparatus body is configured as a color image forming apparatus having at least three image bearing drums, for example.

Next, an image forming apparatus according to a sixth aspect of the present invention includes a plurality of image bearing drums which are detachably mounted on the apparatus main body and which correspond to color printing, and image information on the image bearing drums respectively. Optical writing means for performing optical writing according to the following, a toner image developing means for converting a record written by the optical writing means into a toner image, and a transfer material for transferring the toner image developed by the toner image developing means Image forming apparatus comprising at least transfer means for transferring the toner image on the image carrier drum and transfer devices for transferring the toner images on the image carrier drum to the transfer material conveyed by the transport means, respectively. A detection unit for detecting an initial rotation start position for each of the plurality of image carrier drums, and individually controlling rotation of the plurality of image carrier drums until the detection unit detects the initial rotation start position An initial position setting control unit, wherein the detection unit sets the interval between the image carrier drums to L, sets the drum diameter of the image carrier drum to D, and sets the peripheral surface of the image carrier drum to D. Are sequentially displaced by a distance such that Δ = πDL.

The initial rotation start position may be, for example,
As described, it is a position for detecting a mark corresponding to the maximum eccentric point of the image carrier drum, and, for example, at a position of the same eccentric amount of a plurality of the image carrier drums as described in claim 8. This is the position where the corresponding mark is detected.

The mark is provided on an end face of the image carrier drum, for example, as set forth in claim 9, and is provided outside the image forming area of the image carrier drum, as set forth in claim 10, for example. Is provided on the peripheral surface of the end.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side sectional view schematically illustrating an internal configuration of an image forming apparatus (color printer) according to an embodiment. The overall configuration will be described with reference to FIG.

A color printer (main device) 1 shown in FIG.
Is provided with a paper cassette 2 which is detachable from the front (right side in the figure) at the lower part, and a large number of sheets are placed and stored in the paper cassette 2. A power switch (not shown), a liquid crystal display, a plurality of input keys, and the like are provided on a front upper surface 3 of the main body device 1, and an upper lid 4 is provided substantially over the entire rear side. The upper cover 4 forms an upper discharge tray 5 with a rear portion and a rear upper surface of the main body device 1.

A paper transport belt (hereinafter simply referred to as a belt) 6 is disposed substantially in the center of the main unit 1 in a flat loop shape in the front and rear direction, and both ends thereof are held by a driving roller 7 and a driven roller 8. Then, it circulates in the counterclockwise direction indicated by arrow A in the figure. Four photosensitive drums 9 (9 a, 9 b, 9 c, 9 d) are arranged in a multistage manner in the paper transport direction (from right to left in the drawing) in the upper circulating portion of the belt 6, and each photosensitive drum 9 is individually arranged. The cleaner 11, the initialization charging brush 12, the optical writing head 13, the developing device 14, and the transfer brush 15 are arranged so as to surround them (typically, only the peripheral devices around the photosensitive drum 9d are numbered). Are located.

Each of the optical writing heads 13 is supported by the upper lid 4 via a supporting member 16, and draws an arc from an obliquely upper side as the upper lid 4 is closed. 14 and is positioned so as to face the photosensitive drum 9 to form a recording section.

Each of the developing units 14 includes magenta (M), yellow (Y), and cyan from the developing unit 14 corresponding to the photosensitive drum 9a to the developing unit 14 corresponding to the photosensitive drum 9d. (C) and black (K) toner, respectively. In the lower opening of the developing device 14,
The developing roller 17 is rotatably supported and the photosensitive drum 9
The developing part is formed on the peripheral surface.

The photosensitive drum 9, the cleaner 11, the initialization charging brush 12, and the developing device 14 are integrally mounted on a unit frame as an image forming unit.
The main body device 1 is configured to be detachable and replaceable.

The belt 6 is constantly urged downward by a tension roller 18 pressed against the back surface on the downstream side of the lower circulating portion to maintain an appropriate tension. Belt 6
A feed roller 19 is pressed against the upstream end of the upper circulation section to form a paper carry-in section. The transfer brush 15 is pressed against the photosensitive drum 9 via the belt 6 to form a transfer portion.

Upstream from the belt 6 in the transport direction (right side in the figure)
A pair of standby rollers 21, a paper feed guide path 22 below the pair,
A feed roller pair 23 is provided at the lower end. A paper feed end of the paper cassette 2 is located below the feed roller pair 23, and a paper feed roller 24 is disposed above the paper feed end.

On the other hand, downstream of the belt 6 in the paper transport direction (left side in the figure), a pressure contact roller, a heat roller, a separation claw, a peripheral cleaning device, an oil application roller, a temperature measurement A fixing device 25 is provided. A discharge roller pair 26 is disposed downstream (rearward) of the fixing device 25, and a paper discharge path 27 that reverses from above the main body device to the front is formed behind the discharge roller pair 26, and the terminal of the paper discharge path 27 is an upper discharge path. The paper tray 5 opens above the rear part. A paper discharge roller pair 28 is provided in this opening.

An electrical unit 29 having a predetermined circuit board mounted thereon is disposed between the belt 6 and the paper cassette 2, and a control device including a plurality of electronic components is mounted on the circuit board as shown in FIG. (a) is a partially exploded perspective view showing the configuration of the above-described image forming unit and the arrangement of a sensor for detecting a mark member of the photosensitive drum, and (b) is an enlarged view of a part thereof. FIG. In FIG. 2A, an image forming unit 30 includes a developing unit 14 and the like, each of which includes a developing device 14 and the like.
-1, and a drum unit 30-2 including the photosensitive drum 9, the cleaner 11, the initialization charging brush 12, and the like are integrally assembled via a unit frame 30-3.

From the side of the unit frame 30-3,
A developing roller shaft 31 and a photosensitive drum shaft 32 project outside. Incidentally, the photosensitive drum 9 which is taken out and shown in FIG. The same applies to FIG.

The image forming unit 30 includes the main unit 1
When one of the developing roller shaft 31 and the photosensitive drum shaft 32 is mounted on the unit receiving portions 33a and 33b, the other end (the end in the obliquely upward direction in the drawing) of the developing roller shaft 31 and the photosensitive drum shaft 32 becomes a bearing portion 33a-1 of the unit receiving portion 33a. 33a-2, and the other end (the end in the obliquely forward direction in the drawing) is fixed to the same bearing portion (not visible in the drawing) of the unit receiving portion 33b.

The photosensitive drum 9 is supported by the fixed photosensitive drum shaft 32, and drum gears 34 integrally formed with the photosensitive drum 9 are engaged with the corresponding drive systems of the main unit 1. . The developing roller 17 is supported by the fixed developing roller shaft 31, and a roller gear (not shown) is driven by engaging with a drum gear 34. The end face of the photosensitive drum 9 opposite to the drum gear 34 is a flange 3
5 formed. At a predetermined position on the end surface of the flange 35, an appropriate mark member 36 in a fan shape (although it is not necessary to limit the fan shape to a fan shape) is attached. In this mark member 36,
For example, a bar code or the like is formed in black and white.

On the other hand, on the side wall of the drum unit 30-2 of the image forming unit 30 facing the flange 35,
When the mark member 36 comes to the measurement reference position as the photosensitive drum 9 rotates, the detection hole 3
7 are drilled. Also, the unit frame 30-3
A detection hole 38 is formed in a side wall facing the detection hole 37.

Then, the unit receiving portion 3 of the main unit 1
A detection hole 39 is formed in the wall surface of the surface 3b facing the detection hole 38. A sensor 41 is provided inside the unit receiving portion 33b corresponding to the detection hole 39. Sensor 41
Is a reflection type photo sensor, and as shown in FIG. 3 (b), the irradiation light 42a is emitted from the light emitting portion to the above-described detection holes 39 and 38.
And 37, the reflected light 42b is radiated to the rotating surface of the flange 35, and the reflected light 42b is received by the light receiving portion.

FIG. 3 is a diagram showing a system configuration of the image forming apparatus 1 which drives and controls each section having the above configuration. As shown in FIG. 1, the system of the image forming apparatus 1 includes an I / F (interface) controller 45, a printer controller 46, and various load units 47.

Print data is input to the I / F controller 45 from a host computer 48. The I / F controller 45 analyzes the print data output from the host computer 48 and creates dot pattern data to be output to each optical writing head 13 described above. The I / F controller 45 is connected to a display unit 49 arranged on the front upper surface 3 of the main body device 1 and formed of a liquid crystal or the like.

The printer controller 46 includes a CPU 51,
ROM 52, EEPROM 53, LED head (optical writing head 13) controller 54, driver 55, and buffer 5
6. The CPU 51 performs system control of the entire color image forming apparatus 1 in the present embodiment,
The control according to the program stored in the ROM 52 is performed.

In addition to the above-mentioned reflection type sensor 41, detection information is input to the CPU 51 from each sensor 57 via a buffer 56, and based on this detection information, the CPU 51
Executes a printing process according to a program and data stored in the ROM 52. In the present embodiment, the CP
The rotation of the four drum motors 58 is controlled in accordance with the input data from the reflection type sensor 41 generated during the control processing of U51.

The LED head controller 54 includes an optical writing head (LED head) 13 (13a, 13b, 1) corresponding to the photosensitive drums 9a, 9b, 9c and 9d shown in FIG.
3c, 13d) are connected. The LED head control unit 54 converts the magenta (M), cyan (C), yellow (Y), and black (K) print data output from the I / F controller 45 into the corresponding optical writing heads 13a, The output is controlled to 13b, 13c and 13d.

The driver 55 includes, in addition to the drum motor 58 described above, a heat source 61 of a heating roller of the fixing device 25, the initialization charging brush 12, the developing roller 17, and the transfer brush 15.
High-voltage power supply 62 for applying a high voltage to the photosensitive drum 9
Other than the drive roller 7, the feed roller 19, and the feed roller pair 2
3 and other motors 63 for driving the driven parts to be rotated, a motor 6 for moving the belt 6 up and down in accordance with the full-color printing mode and the monochrome printing mode
4. A fixing clutch 65 for switching the static / moving of the rotation of the roller unit of the fixing device 25, a paper feeding clutch 66 for switching the static / moving of the paper feed roller 24, and a standby clutch 67 for switching the static / moving of the rotation of the standby roller pair 21. And other devices are driven.

FIG. 4 is a diagram showing a configuration of a drive circuit for driving the drum motor (pulse motor) 58. As shown in FIG. The pulse motor 58 is driven under the control of the CPU 51, and the drive circuit 54 'of the pulse motor 58 includes four buffers 71 to 74 and four transistors 75 to 78 as shown in FIG.

The CPU 51 operates according to the program in the ROM 52, and supplies pulse signals output from the ports O1 to O4 of the CPU 51 to the corresponding buffers 71 to 74.
The transistors 75 to 78 corresponding to these are turned on and off at a predetermined timing to configure the pulse motor 58.
The outputs of the transistors 75 to 78 corresponding to the coils A, A, B, and B are supplied to the coils A, A, B, and B to rotate the rotating shaft of the pulse motor 58 by a predetermined angle. Although not shown in FIG. 4, four drive circuits 54 'are connected to the CPU 51 so as to correspond to the four drum motors 58, respectively.

The CPU 51 rotates the photosensitive drum 9 when it detects that the upper cover 4 has been closed at the initial stage of the start-up of the main body device or after the image forming unit 30 is reattached or replaced by a maintenance operation. Meanwhile, information such as a bar code provided by a mark member 36 on the end surface of the photosensitive drum 9 (see the flange 35 in FIG. 2) is read by the reflection type photo sensor 41, and the read information (data) is stored in the EEPROM 53. Write.

The EEPROM 53 is provided with an area for storing drive control data for each of the M, C, Y, and K drum motors 58. The CPU 51 stores data read from the end surfaces of the respective photosensitive drums 9 into these. The data is written in the drive control data area of the corresponding drum motor 58.

The control data for rotating the photosensitive drum 9 at the time of this reading is stored in the ROM 52 as default value data (unique data not including eccentricity correction). Using the default value data, the CPU 51 controls the rotation drive of each photosensitive drum 9 for reading barcode information. In this case, the rotation control based on the default value data of the ROM 52 is sufficient because the rotation control can be performed with an accuracy enough to read the bar code information without performing the precise rotation control corresponding to the eccentricity. is there.

The drum drive control information (bar code information) adapted to the characteristics of each image forming unit read by this reading operation is used for the drums M, C, Y, and K in the actual printing process. The drive control of the motor 58 is performed.

The bar code information read from each of the photosensitive drums 9 includes a drum motor 58 (stepping motor, see FIG. 4) corresponding to those photosensitive drums 9.
Control constants for driving the
U51 reads out, and based on this information, port O1-
A pulse signal is output from O4 to the buffers 71 to 74 to drive and control the motor drive circuit 54 '. As a result, for each of the photosensitive drums 9, a rotational drive control for canceling the eccentricity is performed.

Next, the image forming processing operation in the color printer 1 shown in FIG. 1 configured as described above will be described with reference to FIGS. 1 to 4 again. This color printer 1 is turned on, and the quality of the paper to be used is
When the number of sheets, print mode, and other designations are input as a key input or a signal from a connected host device, printing (printing) is started.

First, the paper feed roller 24 takes out one sheet of the uppermost sheet stored in the paper cassette 2 every one rotation and feeds it to the feed roller pair 23, which feeds the sheet. The sheet is fed to the standby roller pair 21. The standby roller pair 21 temporarily stops the rotation, stops the advance of the sheet, and waits for the transport timing.

Subsequently, the driving roller 7 and the driven roller 8 rotate counterclockwise to start the circulating movement of the belt 6. The photosensitive drum 9 and the developing device 14 of each image forming unit 30 are sequentially driven by the drum motor 58 corresponding to the photosensitive drum 9 in accordance with the printing timing.

The drive roller 7, the standby roller pair 21,
The feed roller pair 23 and the paper feed roller 24 are driven to rotate by engaging with a drive system including the other motor 63 and the gear train shown in FIG. The driven portion of the fixing device 25 on the downstream side of the belt 6 in the sheet conveying direction is rotated by being engaged with a driving system including another motor and this gear train, and is driven by a discharge roller pair 26 and a discharge roller pair 28. Engages with the fixing device 25 and is driven indirectly with the gear train.

The photosensitive drums 9a, 9b, 9c and 9d are driven by a drum motor 58 which engages with the drum gear 34 (see FIG. 2A). Under the clockwise rotation. Each developing roller 17 is engaged with a drum gear 34 of the photosensitive drum 9 and driven to rotate.

The initialization charging brush 12 is connected to the photosensitive drum 9
A uniform high negative charge is applied to the peripheral surface so that the write head 13
Performs an exposure on the peripheral surface of the photosensitive drum 9 in accordance with an image signal to form an electrostatic latent image including a high negative potential portion by the initialization and a low negative potential portion by the exposure.
The developing roller 17 of the developing device 14 transfers the toner 21 to a low potential portion of the electrostatic latent image to form a toner image on the peripheral surface of the photosensitive drum 9 (reversal development).

When the leading end of the toner image on the peripheral surface of the photosensitive drum 9a at the most upstream position is rotated and conveyed to a point facing the belt 6, the printing start position of the paper coincides with the point. The standby roller pair 21 starts rotating and feeds the sheet to the sheet carry-in section. The feed roller 19 presses the belt 6 while applying a suction bias to the sheet, and the belt 6
Paper is electrostatically attracted to the paper. The sheet is attracted to the belt 6 and is conveyed to the first transfer section formed by the photosensitive drum 9a and the transfer brush 15.

The transfer brush 15 applies a transfer current output from a transfer bias power supply (not shown) to the sheet via the belt 6 to transfer the magenta (M) toner image on the photosensitive drum 9a to the sheet. . Subsequently, a second transfer portion by the photosensitive drum 9b and the transfer brush 15 transfers the yellow (Y) toner image, and a third transfer portion by the photosensitive drum 9c and the transfer brush 15 transfers the cyan (C) toner image. The toner image is transferred, and the lowermost transfer portion by the photosensitive drum 9d and the transfer brush 15 transfers the black (K) toner image.

The sheet on which the four color toner images are transferred is separated from the belt 6 and conveyed to the fixing device 25. The fixing device 25 discharges the sheet backward while fixing the toner image on the sheet by heat. . The sheet is discharged with the toner image downward onto the upper discharge tray 5 via a discharge guide path 27 and a discharge roller pair 28 disposed at the end of the guide path.

As described above, in the above-described embodiment, the rotational drive is controlled so as to offset the rotational eccentricity characteristic of the photosensitive drum 9 so that the peripheral linear velocity (peripheral velocity) of the photosensitive drum 9 becomes constant. In this way, the overlapping position of the four color images is prevented from being shifted. As another solution to the eccentricity of the photosensitive drum 9, the optical writing timing by the optical writing head 13 is set to each photosensitive member. There is also a method of exposing while correcting according to the eccentric characteristic of the drum.

Also, information for correcting the exposure drive timing of the optical writing head 13 is written in the information such as the bar code written on the end face of each photosensitive drum 9, and the CPU 51 writes the information in the same manner as described above. The data is read and stored in the area of the EEPROM 53 corresponding to each color. This data is
The PU 51 outputs to the LED head control unit 54 to correct and control the writing cycle in controlling the exposure to the optical writing head 13.

In other words, in a portion where the peripheral speed of the surface of the photosensitive drum 9 is accelerated due to the eccentricity, correction is made so that the one-line exposure cycle of the optical writing head 13 is shortened, and the peripheral speed is reduced. Is corrected so that the one-line exposure cycle becomes longer.

The one-line exposure cycle of the optical writing head 13 is as follows.
It is controlled by a horizontal synchronization signal (HSYNC) based on a one-line write signal Tw generated from an exposure drive control circuit of the LED head control unit 54. The length of the one-line exposure cycle is determined by the count number of the reference clock signal CLK which is a reference for temporal control of the exposure drive control circuit. The eccentricity correction information read from the bar code information is The count number is written as a value that offsets the eccentricity characteristic of each photosensitive drum. This eccentricity correction information is read out in synchronization with the detection of the rotational position of the photosensitive drum 9 (detection of the eccentric peak point mark), and exposure is performed at an appropriate cycle corresponding to the rotational position of the photosensitive drum 9. Thus, an image is formed in which the eccentricity of each photosensitive drum 9 is absorbed.

That is, in the image forming apparatus according to the other embodiment, the overall configuration is almost the same as the image forming apparatus 1 shown in FIG.
0, that is, each photosensitive drum 9 is not driven by an independent drum motor, but is driven by a single drive motor, a gear train, and a clutch.

Each of the photosensitive drums 9 is provided with a detection mark at a position corresponding to the eccentric peak point (maximum eccentric diameter or minimum eccentric diameter). A photo sensor or a lead sensor is provided. At the time of the initial setting control, the CPU 51 controls the alignment so that the start positions of the respective photosensitive drums 9 have the above-described positional relationship (the clutch of the photosensitive drum 9 is continued until the mark is detected).

Also in this embodiment, the color printer 1 has a full-color print (print) mode and a monochrome print (print) mode. In the monochrome printing mode, the belt 6 is lowered, and the image forming unit 30 of K color is
However, the photosensitive drum 9 and the belt 6 do not come into contact with each other at the transfer portion, and the image forming units 30 of M, Y, and C are disengaged from the clutch and do not operate.

Therefore, when printing is performed again in the color printing mode, the mutual positional relationship between the photosensitive drums 9 is out of order. Therefore, it is necessary to perform the above-described initial position setting operation when executing the color print mode after the print processing in the monochrome print mode is performed. Also,
The image forming units 30 of the respective colors can be detached individually, and may be replaced when the consumables or the photosensitive drum 9 has expired. Therefore, the mounting portion of each image forming unit 30 includes
There is a sensor for detecting the mounting of the image forming unit 30,
The image forming unit 3 is provided with any one of the detection sensors.
When the exchange of 0 is recognized, the above-described initial position setting control is executed.

While the main unit is turned off, the image forming unit 30 is replaced or the image forming unit 3 is replaced.
Even if the mutual positional relationship between the photosensitive drums 9 is deviated by extracting 0, the above-described positioning operation is always executed as an initial setting process when the apparatus main body is turned on. Although the power of the apparatus main body is not turned off, the above-described positioning operation may be performed after the upper lid 4 is closed, in response to detection of a so-called roof open operation of opening the upper lid 4 of the apparatus main body.

FIG. 5 is a diagram showing the transition of the surface linear velocity at the exposure point (recording portion) of each photosensitive drum 9 when the respective photosensitive drums 9 are synchronized by performing the above-described positioning. is there. In the figure, the vertical axis represents the surface linear velocity, the horizontal axis represents time, and the photosensitive drum 9a of magenta M from the top,
The transition of the surface linear velocity of the photosensitive drum 9b of yellow Y, the photosensitive drum 9c of cyan C, and the photosensitive drum 9d of black K is shown. As shown in the drawing, the surface linear velocities of the four photosensitive drums 9a to 9d are changed from the upstream photosensitive drum 9a to the downstream photosensitive drums 9b and 9c by a predetermined time in a cycle due to eccentricity. And 9d. As a result, the transfer is performed on the sheet by the surface linear velocity portion having the same cycle. In other words, it is possible to obtain the alignment of the printing position for each line of each color to be overlaid.
Hereinafter, this will be further described.

FIG. 6 shows a detection mark corresponding to the eccentric peak point applied to each photosensitive drum 9 and a reflection type photo sensor (or lead sensor) provided in the apparatus main body for detecting this mark. It is a figure showing a positional relationship. FIG. 3 is a drawing in which the end faces of the photosensitive drums 9a to 9d of four colors are overlapped. The eccentric peak point detection sensors 81a to 81d composed of the reflection type photo sensors shown in FIG.
It is disposed at a rotation start position detection point for a to 9d, and detects the detection marks 82a to 82d on the peripheral surface of the photosensitive drum 9 respectively.

The detection marks 82a to 82d are peak point identification marks provided on the end surfaces of the respective photosensitive drums 9, and are marked at locations corresponding to the eccentric peak points. Then, each of these eccentric peak point detection sensors 81a-81
The arrangement point of d is the diameter D of the photosensitive drum 9 = 30 mm, that is, the circumference S of the photosensitive drum 9 = πD = 94.2 mm,
Distance between transfer units (arrangement interval of each photosensitive drum 9) L = 8
Assuming that the length is 9 mm, the circumference of the photosensitive drum 9 is shifted in the order of M, Y, C, and K in terms of the arc Δ = SL = 5.2 mm of the circumference in terms of the circumference. The reason will be described below.

As described above, each image forming unit 30
Since the can be removed individually, it is necessary to adjust the initial position of rotation. In this initial setting process, first, the drive clutch of each photoconductor drum 9 is controlled to rotate each photoconductor drum 9a to 9d to a fixed position so as to have the relationship shown in FIG. Thus, the eccentric peak points of the respective photosensitive drums 9 are set in a positional relationship shifted by Δ = S−L = 5.2 mm by the circumference of the photosensitive drums 9. From this state, rotation for printing processing is started.

FIG. 7 is a diagram for explaining the operation of the above-described printing process. As shown in FIG.
The eccentric peak point Pm is exposed at the recording portion (exposure point) Rm, is developed in the middle, the image passes through the transfer point Tm, and the image position of the paper transferred at the transfer point Tm is Y color. The distance that the eccentric peak point Pm of the photosensitive drum 9a moves before reaching the transfer point Ty of the photosensitive drum 9b is
It is “a + L”, and the time is “(a + L) / V” (V: rotating peripheral surface speed of the photosensitive drum).

At this point, similarly, the Y-color photosensitive drum 9b
In order to make the image exposed to the eccentric peak point Py of the Y color coincide with the transfer point Ty, the eccentric peak point Py of the Y-color photosensitive drum 9b is a / V seconds before the point of coincidence with the Ty. Must pass through the exposure point Ry.

The eccentric peak point P on the photosensitive drum 9 is
When the eccentric peak point Pm of the M-color photosensitive drum 9a is located at the transfer point Tm, the eccentric peak point Py of the Y-color photosensitive drum 9b has a circumferential length L = L from the transfer point Ty. It is necessary to pass the position 89 mm before.

Similarly, at the transfer point Tc, the photosensitive drum 9 of M color
In order for the images formed at the eccentric peak points Pm and Py of the photoconductor drum 9b of a and Y colors and transferred to the paper to match the image of the eccentric peak point Pc of the photoconductor drum 9c of C color, When the eccentric peak point Py of the Y-color photoconductor drum 9b is at the transfer point Ty, the eccentric peak point Pc of the C-color photoconductor drum 9c passes through a position which is circumferentially shorter than the transfer point Tc by L = 89 mm. Need to be. Similarly, the photosensitive drum 9d of K color must have the same relationship.

That is, when viewed with reference to the eccentric peak point Pm of the most upstream photosensitive drum 9a, the eccentric peak point Py of the Y photosensitive drum 9b is located at the position "πDL" which is traced back by the distance L. The eccentric peak point Pc of the photosensitive drum 9c of C color is located at a position “πDL” further back by the distance L, and the eccentric peak point Pk of the photosensitive drum 9d of K color is further than the distance. The position “π
D-L ".

That is, the eccentric peak point P (Pm, Py, P
c, Pk) relative to the photosensitive drum 9 (9a,
9b, 9c, and 9d), the point relative to the eccentric peak point P of each photosensitive drum 9 in the order of M, Y, C, and K as described above is determined for each photosensitive drum 9. (The positions are each delayed by L mm in the circumferential length). This is the reason why in FIG. 6, the detection position of the eccentric peak point mark of each photosensitive drum 9 is set to be shifted by Δ = S−L = 5.2 mm by the circumference of the photosensitive drum 9. As a result, the images at the positions of the same eccentricity of the respective photosensitive drums are overlaid and transferred on the sheet.

The eccentric peak point detection sensors 81a-81
d, peak point identification marks 82a to 82d
May be provided on the end surfaces of the respective photosensitive drums 9a to 9d, or may be provided on the peripheral surfaces. And
The peak point identification marks 82a to 82d are
When applied to the peripheral surfaces a to 9d, they are provided in an area other than the area used for image formation at the end of the surface of the photosensitive drum 9.

The peak point identification marks 82a to 82d
Need only correspond to the eccentric peak point of the photosensitive drum 9, and therefore may be assigned to the eccentric lowest peak point or may be defined in another way. In short, it is only necessary that the eccentricity of each photosensitive drum 9 is the same.

FIG. 8 is a diagram showing an example in which the eccentric peak point mark is a through hole in the end surface of the photosensitive drum. FIG.
Components similar to those shown in FIGS. 2A and 2B are shown in FIGS.
The same numbers as in (b) are given (or omitted).
As shown in FIG. 8, the transmission type optical sensors 83 (83a, 83b) are provided on both sides of the image forming unit 30, and all components (the image forming unit 3) on the optical axis of the light emitting unit 83a are provided.
The photosensitive drum 9, the drum unit 30-2, the unit frame 30-3, and the unit receiving portions 33a and 33b) have through holes. The positions of the through holes of the drum gear 34 and the drum flange 35 of the photosensitive drum 9 are set to the same eccentric characteristic position for each color so that the gear accuracy and the maximum shake (or the minimum shake) are set.

Incidentally, the photosensitive drum provided with this through-hole is
Of course, it can be used in the above-described second embodiment, but can also be used in the above-described first embodiment. In such a case, the motors for driving the image forming units of each color are made independent, and each time the photosensitive drum makes one rotation, the transmission type sensor 83 detects once, and the position of the four photosensitive drums for each color is shifted. When the motor is driven by the control, it is only necessary to synchronize by electric control.

[0077]

As described above in detail, according to the present invention, the rotation control of the motor or the timing of optical writing is changed based on the eccentricity information of the photosensitive drum transmitted to the main unit, so that the photosensitive drum is changed. The expansion and contraction of the formed image on the peripheral surface due to the eccentricity can be equalized.Therefore, the color matching of the formed image to be overlaid and synthesized by a plurality of photosensitive drums such as a tandem method is optimized, A high-quality image without color spots can be formed.

[Brief description of the drawings]

FIG. 1 is a side sectional view schematically showing an internal configuration of a color image forming apparatus according to a first embodiment.

2A is a partially exploded perspective view showing a configuration of an image forming unit of a color image forming apparatus and an arrangement of a sensor for detecting a mark member of a photosensitive drum, and FIG. 2B is a partially enlarged view of FIG. is there.

FIG. 3 is a diagram illustrating a system configuration of an image forming apparatus that drives and controls each unit.

FIG. 4 is a diagram illustrating a configuration of a drive circuit that drives a drum motor (pulse motor).

FIG. 5 is an exposure point (recording unit) of each photosensitive drum when synchronization is achieved by performing positioning according to the second embodiment.
FIG. 4 is a diagram showing a change in the surface linear velocity in FIG.

FIG. 6 shows a positional relationship between a detection mark corresponding to an eccentric peak point applied to each photosensitive drum and a reflection type photo sensor (or a lead sensor) provided in the apparatus main body for detecting the mark. FIG.

FIG. 7 is a diagram illustrating an operation of setting an initial position in a printing process.

FIG. 8 is a diagram illustrating an example in which the eccentric peak point mark is a through hole in the end surface of the photosensitive drum.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Color printer (body apparatus) 2 Paper cassette 3 Front upper surface 4 Top cover 5 Upper discharge tray 6 Paper transport belt (belt) 7 Drive roller 8 Follower roller 9 (9a, 9b, 9c, 9d) Photoconductor drum 11 Cleaner 12 Initializing charging brush 13 Optical writing head 14 Developing device 15 Transfer brush 17 Developing roller 18 Tension roller 19 Feeding roller 21 Standby roller pair 22 Feed guide path 23 Feed roller pair 24 Feed roller 25 Fixing device 26 Eject roller pair 27 Discharge guide path 28 Discharge roller pair 29 Electrical unit 30 Image forming unit 30-1 Developing unit 30-2 Drum unit 30-3 Unit frame 31 Developing roller shaft 32 Photoconductor drum shaft 33a, 33b Unit receiving portions 33a-1, 33a -2 Bearing part 34 Drum gear 35 Flange 36 Mark Member 37, 38, 39 Detection hole 41 Reflection sensor 42a Irradiation light 42b Reflection light 45 I / F (interface) controller 46 Printer controller 47 Various load units 48 Host computer 51 CPU 52 ROM 53 EEPROM 54 LED head (optical writing head) ) Control unit 54 'Drive circuit 55 Driver 56 Buffer 58 Drum motor 61 Heat source of heat generating roller 62 High voltage power supply unit 63 Other motor 64 Belt up / down motor 65 Fixing clutch 66 Paper feed clutch 67 Standby clutch 71, 72, 73, 74 Buffers 75, 76, 77, 78 Transistors 81a, 81b, 81c, 81d Eccentric peak point detection sensors 82a, 82b, 82c, 82d Eccentric peak point marks 83a, 83b Transmission optical sensors

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takao Yoto 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Inside Casio Electronics Co., Ltd. (72) Inventor Kuniki 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Casio Electronics (72) Inventor Yasushi Nakamura 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Casio Electronics Co., Ltd.

Claims (10)

[Claims] An image carrier drum replaceably disposed in an apparatus main body, optical writing means for performing optical writing on the image bearing drum in accordance with image information, and data written by the optical writing means. Toner image developing means for converting a recorded image into a toner image, conveying means for conveying a transfer material to contact the image carrier drum carrying the toner image developed by the toner image developing means, and the image carrier drum And a transfer device for transferring the toner image on the image carrier drum to the transfer material conveyed by the conveyance means. A notification member provided on the image carrier drum for notifying the rotation of the image carrier drum by the notification member to the apparatus main body; Recognizing means for recognizing the rotation phase of the image carrier drum based on the rotation information; and rotation for modulating and controlling the rotation of the image carrier drum based on the rotation phase of the image carrier drum recognized by the recognition means. An image forming apparatus, comprising: a modulation control unit. 2. An optical writing unit according to claim 1, wherein said optical writing unit writes the light onto the image carrier drum based on a rotation phase of the image carrier drum recognized by the recognition unit in synchronization with the modulation control by the rotation modulation control unit. 2. The image forming apparatus according to claim 1, further comprising an optical writing modulation control unit that controls the timing. 3. The image forming apparatus according to claim 1, wherein the notifying unit includes eccentricity information of a drum gear as eccentricity information of the image carrier drum. 4. The image forming apparatus according to claim 1, wherein the notifying unit notifies information of an eccentric amount and an eccentric peak point as eccentric information of the image carrier drum. 5. The image forming apparatus according to claim 1, wherein the apparatus main body is a color image forming apparatus having at least three image bearing drums. 6. A plurality of image carrier drums which are detachably provided in the apparatus main body and correspond to color printing, and optical writing means for performing optical writing on the image carrier drums in accordance with image information, respectively. A toner image developing means for converting a record written by the optical writing means into a toner image; a conveying means for conveying a transfer material to transfer the toner image developed by the toner image developing means; An image forming apparatus comprising: at least a transfer unit that is arranged to transfer the toner image on the image carrier drum to the transfer material conveyed by the conveyance unit. Detecting means for detecting an initial rotation start position, and an initial position setting control means for individually controlling the rotation of the plurality of image bearing drums until the detecting means detects the initial rotation start position, The detecting means sets a distance at which an arrangement interval of the image carrier drum is L, a drum diameter of the image carrier drum is D, and an arc Δ of a circumferential surface of the image carrier drum is Δ = πDL. The image forming apparatus is arranged to be sequentially shifted only by one image. 7. The image forming apparatus according to claim 6, wherein the initial rotation start position is a position for detecting a mark corresponding to a maximum eccentric point of the image carrier drum. 8. The image forming apparatus according to claim 6, wherein the initial rotation start position is a position for detecting a mark corresponding to a position of the same eccentricity of the plurality of image bearing drums. 9. The image forming apparatus according to claim 7, wherein the mark is provided on an end face of the image carrier drum. 10. The image forming apparatus according to claim 7, wherein the mark is provided on an end circumferential surface of the image carrier drum outside an image forming area.