JP3880391B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus for forming an image by an electrophotographic image forming system. Place It is about.
[0002]
Examples of the electrophotographic image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (for example, an LED printer, a laser beam printer, etc.), an electrophotographic facsimile apparatus, and an electrophotographic word processor.
[0003]
Further, as the process cartridge, a charging unit, a developing unit or a cleaning unit and an electrophotographic photosensitive member are integrally formed into a cartridge, and the cartridge can be attached to and detached from the image forming apparatus main body. In addition, at least one of the charging unit, the developing unit, and the cleaning unit and the electrophotographic photosensitive member are integrally formed into a cartridge that can be attached to and detached from the image forming apparatus main body. Further, it means that at least the developing means and the electrophotographic photosensitive member are integrated into a cartridge so that it can be attached to and detached from the apparatus main body.
[0004]
[Prior art]
Conventionally, a color image forming apparatus called a so-called in-line system in which a plurality of image carriers (electrophotographic photosensitive drums) are arranged in a line is known. This is because the transfer material, which is a sheet-like recording medium such as recording paper, is carried and conveyed by an electrostatic transfer belt stretched by a plurality of rollers, and is arranged along the transfer material conveyance path. A toner image composed of yellow, magenta, cyan, and black is sequentially transferred onto a sheet by a photosensitive drum, and a color image is formed by superimposing each color.
[0005]
This configuration has attracted attention in recent years because it can print at high speed. However, since each color is formed by four photosensitive drums, a color image is formed in a configuration in which colors are superimposed on each photosensitive drum via four conveyance paths for each color (four-pass method). Compared to the apparatus, a higher accuracy is required for rotational driving of the photosensitive drum.
[0006]
Generally, a gear train is used to drive the electrophotographic photosensitive drum, and rotation unevenness due to gear accuracy always occurs. However, in the case of the 4-pass system, the reduction ratio of the drive gear train is an integer combination. Accordingly, it is possible to avoid the influence of low-frequency rotation unevenness such as one rotation component of the gear and to match the image forming positions of the respective colors.
[0007]
In contrast, in the case of the in-line method in which a plurality of electrophotographic photosensitive drums are arranged, the driving gear train is also independent because the plurality of electrophotographic photosensitive drums are independent, and a workaround such as the above-described four-pass method. Therefore, color misregistration is likely to occur due to misalignment of image forming positions of the respective colors.
[0008]
As a countermeasure against such color misregistration, conventionally, in a configuration in which driving is driven from one motor to drive a plurality of electrophotographic photosensitive drums, it is assumed that the electrophotographic photosensitive drum is almost a perfect circle. In addition, there is a method (see Japanese Patent Laid-Open No. 11-258966) in which the phases of the gears are assembled and assembled so that only the relative phases of the gears are not shifted. Also, by detecting the angular velocity of the electrophotographic photosensitive drum, etc., the rotation of the motor is controlled so as to cancel out the uneven speed of each electrophotographic photosensitive drum, and the relative rotational phase of the electrophotographic photosensitive drum is adjusted. Measures to reduce color misregistration by adjusting to a desired state (see Japanese Patent Laid-Open No. 09-146329) have been taken. Excellent accuracy.
[0009]
[Problems to be solved by the invention]
However, according to the above conventional technique, in the method of adjusting the rotational phase of the electrophotographic photosensitive drum by the control means, when the process cartridge including the electrophotographic photosensitive drum is attached or detached, the phase of the driving side and the electrophotographic photosensitive drum is adjusted. Therefore, it is necessary to detect the speed irregularity of the electrophotographic photosensitive drum by obtaining an image signal of the detection pattern by a CCD or the like every time the process cartridge is attached / detached. It will end up.
[0010]
For an apparatus that does not have a means for detecting the phase and controlling the drive, a method has been proposed to prevent the drive side and the electrophotographic photosensitive drum from being out of phase (Japanese Patent Laid-Open No. 07-199732). (Refer to the above), the effect of reproducing the phase cannot be obtained unless the drive unit is specially devised. In addition, since the drive is transmitted by a key provided separately from the drive-side or driven-side component, there is a risk of fluctuations in angular velocity due to looseness with the keyway.
[0011]
Also, in the case of an apparatus that controls the driving by detecting the speed of the electrophotographic photosensitive drum as described above, it is required that the rotational accuracy of the electrophotographic photosensitive drum of each color be high, so that the higher accuracy. An engagement means (coupling) that satisfies the above is required.
[0012]
The present invention has been made in view of the above-mentioned unsolved problems of the prior art, shortens the waiting time for adjusting the phase after attaching / detaching the process cartridge, reduces the occurrence of angular velocity fluctuations, and is convenient for the user. Image forming device with excellent color misalignment Place Is intended to provide.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus of the present invention is an image forming apparatus for forming an image on a recording medium, (A) a motor, (b) an electrophotographic photosensitive member, and a driven side coupling provided at an end of the electrophotographic photosensitive member for transmitting a rotational driving force from the motor to the electrophotographic photosensitive member. A driven side coupling having a helical shape portion of a substantially triangular prism twisted shape and a center hole having a recess; A plurality of process cartridges with (C) plural Above Process cartridge Have Each said The electrophotographic photosensitive member Transmit rotational drive force , Coupled with the driven side coupling Multiple drive A side coupling that engages with the spiral shaped portion; The rotational driving force is Electrophotographic photosensitive The twisted shape of a roughly triangular prism for transmission to the body A driving-side coupling having a helical hole; and (d) a boss that engages with the central hole disposed in the helical hole, wherein the driving-side coupling and the driven-side coupling are coupled to each other. When the driven side coupling and the driven side coupling are At a given rotational phase Combined For A boss having a protrusion that engages with the recess; (e) an axial phase detection means that directly detects the rotational phase of each drive side coupling; and (f) a detection transferred by each electrophotographic photosensitive member. Angular velocity fluctuation detecting means for detecting periodic speed unevenness of the electrophotographic photosensitive member by reading a pattern image; and (g) individually determining at least one of the rotational speed and rotational phase of the plurality of drive side couplings. Rotation control means for controlling It is characterized by that.
[0014]
[0015]
Above The rotation control means Above When the process cartridge is replaced Above Based on the output of the angular velocity fluctuation detection means The electrophotographic photosensitive It is good to control the rotation speed and rotation phase of the body.
[0016]
Above Same rotation control means Above When a process cartridge is installed or removed Above Based on the output of the axis phase detection means The electrophotographic photosensitive It is good to control the rotational phase of the body.
[0017]
Above Process cartridge replacement detection means for detecting that the process cartridge has been replaced may be provided.
[0018]
[0019]
[0020]
[0021]
[Action]
When you replace a process cartridge with a new one, Electrophotographic photosensitive Color shifts due to fluctuations in the body's angular velocity (velocity unevenness) are detected from the detection pattern image. Electrophotographic photosensitive Color misregistration is prevented by controlling the rotational speed and rotational phase of the body.
[0022]
When the same process cartridge is attached and detached, the driving force transmitting member of the apparatus main body having the first and second engaging portions Electrophotographic photosensitive By means of body rotation transmission means, Electrophotographic photosensitive Highly accurate coupling performance without phase shift between the bodies is reproduced and maintained, so only a simple adjustment operation that controls only the rotational phase by detecting the phase shift of the driving force transmission member with the axial phase detection means Thus, it is possible to prevent color misregistration equivalent to the above.
[0023]
When attaching and detaching the same process cartridge, the waiting time of the user is greatly reduced by substituting the above simple method without performing complicated and time-consuming adjustment for detecting color misregistration based on the detection pattern image. An easy-to-use high-quality and high-performance image forming apparatus can be realized.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
[0025]
FIG. 1 shows an image forming apparatus according to a first embodiment, which is a longitudinal sectional view showing a full-color laser beam printer which is an embodiment of a color image forming apparatus.
[0026]
[Description of overall configuration]
The color image forming apparatus shown in FIG. 1 has four pieces arranged in a vertical direction. Electrophotographic photosensitive The electrophotographic photosensitive drum 1 (1a, 1b, 1c, 1d) is provided. Each electrophotographic photosensitive drum 1 is driven to rotate counterclockwise in FIG. Around each electrophotographic photosensitive drum 1, a charging device 2 (2a, 2b, 2c, 2d) for uniformly charging the surface of the electrophotographic photosensitive drum 1 in order according to the rotation direction, and a laser based on image information. A scanner unit 3 (3a, 3b, 3c, 3d) that irradiates a beam to form an electrostatic latent image on the electrophotographic photosensitive drum 1, and a developing device 4 that attaches toner to the electrostatic latent image and develops it as a toner image. (4a, 4b, 4c, 4d), an electrostatic transfer device 5 that transfers the toner image on each electrophotographic photosensitive drum 1 to a transfer material S that is a recording medium, and the surface of each electrophotographic photosensitive drum 1 after transfer. A cleaning device 6 (6a, 6b, 6c, 6d) for removing the remaining transfer residual toner is provided.
[0027]
Here, the electrophotographic photosensitive drum 1, the charging device 2, the developing device 4, the cleaning device 6 and the like are integrally formed as a cartridge to form a process cartridge 7 (7a, 7b, 7c, 7d). The process cartridge 7 can be attached to and detached from the apparatus main body by mounting means (not shown) provided in the apparatus main body.
[0028]
Each electrophotographic photosensitive drum 1 is configured by coating an organic photoconductive layer (OPC photosensitive member) on the outer peripheral surface of an aluminum cylinder having a diameter of 30 mm, for example. Each electrophotographic photosensitive drum 1 is rotatably supported at both ends by a support member, and one shaft of each electrophotographic photosensitive drum 1 is provided via a driving force transmission mechanism shown in FIGS. A rotational driving force by a motor 40 (described later) disposed on the apparatus main body side of the color image forming apparatus is transmitted to the end portion, thereby being rotated counterclockwise.
[0029]
As the charging device 2, a contact charging type can be used. The charging member is a conductive roller formed in a roller shape. Each of the electrophotographic photosensitive members is brought into contact with the surface of the electrophotographic photosensitive drum 1 and a charging bias voltage is applied to the roller. The surface of the drum 1 is uniformly charged.
[0030]
Each scanner unit 3 is arranged in a substantially horizontal direction of each electrophotographic photosensitive drum 1, and image light corresponding to an image signal is rotated at high speed by a scanner motor (not shown) by a laser diode (not shown). 8 (8a, 8b, 8c, 8d). The image light reflected by each polygon mirror 8 selectively exposes the surface of each charged electrophotographic photosensitive drum 1 through an imaging lens 9 (9a, 9b, 9c, 9d) to form an electrostatic latent image. It is configured to form an image.
[0031]
Each developing device 4 applies yellow, magenta, cyan, and black toners to the outer periphery of the developing roller 10 (10a, 10b, 10c, 10d) that rotates in the clockwise direction in the figure, and applies a charge to the toner.
[0032]
Then, by applying a developing bias to the developing roller 10 facing each electrophotographic photosensitive drum 1 on which the latent image is formed, toner development is performed on each electrophotographic photosensitive drum 1 in accordance with the latent image. .
[0033]
An electrostatic transfer belt 11 that circulates and moves so as to face and contact all the electrophotographic photosensitive drums 1a, 1b, 1c, and 1d is disposed. The electrostatic transfer belt 11 is 10 ¹¹ -10 ¹⁴ It is composed of a film-like member having a volume resistivity of Ω · cm and a thickness of about 150 μm. The electrostatic transfer belt 11 is supported by four rollers in the vertical direction and electrostatically attracts the transfer material S to the left outer peripheral surface in the drawing so that the transfer material S comes into contact with each electrophotographic photosensitive drum 1. It moves cyclically. As a result, the transfer material S is conveyed to the transfer position by the electrostatic transfer belt 11, and the toner image on each electrophotographic photosensitive drum 1 is transferred.
[0034]
The transfer roller 12 (12a, 12b, 12c, 12d) is arranged in parallel at a position in contact with the inside of the electrostatic transfer belt 11 and facing the four electrophotographic photosensitive drums 1a, 1b, 1c, 1d. A positive charge is applied from each transfer roller 12 to the transfer material S via the electrostatic transfer belt 11, and the electrophotographic photosensitive drum 1 is applied to the sheet in contact with the electrophotographic photosensitive drum 1 by the electric field generated by the charge. The negative toner image on the upper side is transferred.
[0035]
The electrostatic transfer belt 11 is a belt having a circumferential length of about 700 mm and a thickness of 150 μm. As a result, the above-described electrostatic transfer belt 11 circulates and the toner image is transferred while the transfer material S is conveyed from the driven roller 14a side to the drive roller 13 side.
[0036]
The paper feed unit 16 feeds and conveys the transfer material S to the image forming unit, and a plurality of transfer materials S are stored in the paper feed cassette 17. At the time of image formation, the paper feed roller 18 (half-moon roller) and the registration roller pair 19 are driven and rotated according to the image forming operation to separate and feed the transfer material S in the paper feed cassette 17 one by one. The leading edge of the transfer material S abuts against the registration roller pair 19 and temporarily stops. After forming a loop, the rotation of the electrostatic transfer belt 11 and the image writing position are synchronized, and the registration roller pair 19 moves to the electrostatic transfer belt 11. The paper is fed.
[0037]
The fixing unit 20 fixes a plurality of color toner images transferred to the transfer material S, and includes a heating roller 21a that rotates, and a pressure roller 21b that presses and applies heat and pressure to the transfer material S. Consists of.
[0038]
That is, the transfer material S to which the toner image on each electrophotographic photosensitive drum 1 is transferred is conveyed by the fixing roller pair 21a and 21b when passing through the fixing unit 20, and heat and pressure are transferred by the fixing roller pair 21a and 21b. Is given. As a result, the toner images of a plurality of colors are fixed on the surface of the transfer material S.
[0039]
As an image forming operation, the process cartridges 7a, 7b, 7c, and 7d are sequentially driven in accordance with the printing timing, and the electrophotographic photosensitive drums 1a, 1b, 1c, and 1d are rotated counterclockwise in accordance with the drive. Is driven to rotate. The scanner units 3 corresponding to the process cartridges 7 are sequentially driven. By this driving, the charging device 2 applies a uniform charge to the peripheral surface of the electrophotographic photosensitive drum 1, and each scanner unit 3 exposes the peripheral surface of each electrophotographic photosensitive drum 1 according to an image signal. An electrostatic latent image is formed on the circumferential surface of each electrophotographic photosensitive drum. The developing roller 10 in each developing device 4 forms (develops) a toner image on the peripheral surface of each electrophotographic photosensitive drum 1 by transferring the toner to the low potential portion of the electrostatic latent image.
[0040]
At the timing when the leading edge of the toner image formed on the peripheral surface of the most upstream electrophotographic photosensitive drum 1 is rotationally conveyed to the point facing the electrostatic transfer belt 11, printing of the transfer material S is started at the point facing the toner image. The registration roller pair 19 starts rotating so that the positions coincide with each other, and the transfer material S is fed to the electrostatic transfer belt 11.
[0041]
The transfer material S is pressed against the outer periphery of the electrostatic transfer belt 11 so as to be sandwiched between the electrostatic adsorption roller 22 and the electrostatic transfer belt 11. Then, by applying a voltage between the electrostatic transfer belt 11 and the electrostatic adsorption roller 22, charges are induced in the transfer material S that is a dielectric and the dielectric layer of the electrostatic transfer belt 11, and the transfer material S Is electrostatically attracted to the outer periphery of the electrostatic transfer belt 11. As a result, the transfer material S is stably adsorbed to the electrostatic transfer belt 11 and conveyed to the most downstream transfer unit.
[0042]
While being conveyed in this manner, the toner image on each electrophotographic photosensitive drum 1 is sequentially transferred to the transfer material S by an electric field formed between each electrophotographic photosensitive drum 1 and the transfer roller 12.
[0043]
The transfer material S onto which the four color toner images have been transferred is separated from the electrostatic transfer belt 11 by the curvature of the driving roller 13 and is carried into the fixing unit 20. After the toner image is thermally fixed by the fixing unit 20, the transfer material S is discharged out of the main body by the paper discharge roller pair 23 with the image surface facing down from the paper discharge unit 24.
[0044]
[Description of process cartridge drive mechanism]
Each process cartridge 7 is based on FIGS. As an electrophotographic photoreceptor A drive mechanism for rotating the electrophotographic photosensitive drum 1 will be described.
[0045]
The driving mechanism of each electrophotographic photosensitive drum 1 has a driving force transmission member 30 shown in FIG. 2, which includes a gear 31a for transmitting a rotational driving force from the apparatus main body to the process cartridge 7, and a gear 31a. And a shaft 31b that is integral with the shaft 31b, and a driving-side coupling 31c that rotates integrally with the shaft 31b and transmits the rotational driving force to the process cartridge 7. The part can be a resin molded product.
[0046]
As shown in FIG. 3, the shaft portion 31 b of the driving force transmission member 30 is supported by a cylinder 32 installed in the apparatus main body of the color image forming apparatus so as to freely rotate and move, and the driving force transmission member 30 extends in the axial direction. It is movable and is pressed in the direction of the electrophotographic photosensitive drum 1 by the leaf spring 33.
[0047]
A drum shaft 34 that rotates integrally with the electrophotographic photosensitive drum 1 is fixed to each electrophotographic photosensitive drum 1 using a parallel pin 35, and the drum shaft 34 is connected to the color image forming apparatus via a bearing 36. It is accurately positioned on the device body. A coupling 37 constituting the rotation transmission means of the electrophotographic photosensitive drum 1 on the driven side is fixed to the shaft end portion of the drum shaft 34, and meshes with the coupling 31c on the driving side to transmit the rotational driving force. .
[0048]
The driving-side coupling 31c and the driven-side coupling 37 are each provided with a spiral hole 31d (first engagement portion) having a substantially triangular prism shape as shown in FIG. The spiral shape portion 37a (first engagement portion) is provided. When the spiral hole 31d and the spiral portion 37a are fitted and rotated in a predetermined rotational direction, the two are surely engaged with each other. In this configuration, the relative positions of the driving side and the driven side are determined at three points, and this position does not move during rotation. Therefore, the angular velocity fluctuation does not occur in the coupling portion, and the electrophotographic photosensitive drum 1 is high. It is rotationally driven with accuracy.
[0049]
Further, a boss portion 31f (second engagement portion) having a protrusion 31e is provided inside the driving side coupling 31c, and the driven side coupling 37 has a center hole 37c (having a recess 37b). A second engagement portion) is formed. Therefore, the coupling between the driving-side coupling 31c and the driven-side coupling 37 can be fitted only in the rotational phase where the protrusion 31e and the recess 37b coincide.
[0050]
Note that the second engagement portion is between the protrusion 31e and the recess 37b by the saddle eye in the above-described triangular spiral first engagement portion so as not to be involved in the transmission of the rotational driving force. Has a large backlash to prevent contact during rotation. In addition, since the first and second engaging portions are in a positional relationship in which they are simultaneously engaged / separated, the coupling portion engaging / separating operation and driving force transmission accuracy are not adversely affected.
[0051]
FIG. 5 shows a driving force transmission member 30 (30a, 30b, 30c, 30d) by means of a motor 40 (40a, 40b, 40c, 40d) on the apparatus main body provided exclusively for the electrophotographic photosensitive drums 1a, 1b, 1c, 1d. The control unit for driving the electrophotographic photosensitive drums 1a, 1b, 1c, and 1d through FIG. Each driving force transmitting member 30 is provided with a target 41 (41a, 41b, 41c, 41d) for detecting a rotational phase, and an optical or magnetic phase detecting device 42 (42a, 42a, 42) serving as an axial phase detecting means. 42b, 42c, and 42d), a phase signal can be detected once per rotation. Further, a pattern detection unit 43 is provided so as to face the electrostatic transfer belt 11, and an image of a detection pattern on the electrostatic transfer belt 11 can be optically detected.
[0052]
In this configuration, the main component of the angular velocity unevenness (angular velocity fluctuation) is only one drum rotation cycle, so that the detection pattern formed on each electrophotographic photosensitive drum 1 at equal time intervals is transferred to the electrostatic transfer belt 11. Then, when the image is read by the pattern detection unit 43 and the accumulated fluctuation component of the pattern interval is obtained for each color, a sine waveform as shown in FIG. 6 is obtained. In the figure, the horizontal axis represents the distance from the leading edge of the image, and the vertical axis represents the amount of displacement.
[0053]
In order to obtain the phase relationship of the four colors, the control circuit 44 creates one color at a time while managing the image formation start timing of each color by the speed unevenness detection unit 45, which is an angle fluctuation detection means, based on the output of the pattern detection unit 43. The motor 40 may be controlled by the motor control unit 47 that is a rotation control means after performing processing such as calculating and detecting the image, obtaining a sine waveform by the calculation unit 46, correcting the comparison with the start timing interval, and comparing them. .
[0054]
For example, in FIG. 6, when black K is used as a reference, color misregistration with black K can be reduced by shifting yellow Y to the image leading end side by a distance y. Similarly, magenta M may be shifted by distance m, and cyan C may be shifted by distance c. However, since this pattern detection requires a predetermined time, if it is frequently performed, the consumption time on the user side increases.
[0055]
The generation level and phase of the angular velocity unevenness are not determined only on the driving side, but are determined by the whole including the electrophotographic photosensitive drum. Therefore, when the process cartridge including the electrophotographic photosensitive drum is replaced with a new one, the image by the pattern detection unit described above is used. It is necessary to perform detection. However, when the coupling is separated / engaged in other cases, for example, only when the same cartridge is detached, the pattern detection is possible if the phase of the driving side and the electrophotographic photosensitive drum is reproduced with high accuracy as described above. It is not necessary to perform image detection work by the unit.
[0056]
That is, the phase detectors 42a, 42b, 42c, and 42d that detect the rotational phases of the driving force transmission members 30a, 30b, 30c, and 30d that rotate the electrophotographic photosensitive drums 1a, 1b, 1c, and 1d are used. Based on this phase information, the rotational phase is controlled by the shaft phase detector 48, and only when the process cartridge 7 is replaced, the speed unevenness by the above-described image detection is adjusted.
[0057]
If a process cartridge replacement detection means (not shown) for detecting that a process cartridge has been replaced with a new one is provided, it is possible to detect that the process cartridge has been replaced.
[0058]
When only the same cartridge is attached and detached, the phases of the driving side and the electrophotographic photosensitive drum 1 are reproduced by the high-precision coupling unit shown in FIG. 4, so that each phase is detected instead of performing time-consuming image detection. Based on the output of the detection device 42, the phase shift of the driving force transmission member 30 of each process cartridge 7 is detected, and the phase adjustment operation for adjusting the shaft phase on the motor side is performed.
[0059]
For example, when the phase waveform detected by the axial phase detector 48 based on the outputs of the phase detectors 42a, 42b, 42c, and 42d is as shown in FIG. 7, the time y corresponding to the distance y in FIG. ₁ If the phase of the yellow driving force transmission member 30a is controlled so as to rotate as quickly as possible, the color misregistration between black and yellow decreases. Similarly, the magenta driving force transmission member 30b has a time m corresponding to the distance m. ₁ Faster, the cyan driving force transmitting member 30c has a time c corresponding to the distance c. ₁ What is necessary is just to carry out phase control so that it may rotate quickly.
[0060]
The phase can be controlled by adjusting the rotational speeds of the motors 40a, 40b, 40c, and 40d for a necessary time in the motor control unit 47 of the control circuit 44.
[0061]
After performing such phase control, the above-described phase relationship is obtained as shown in FIG. 8, and the color misregistration can be reduced to about ½ or less.
[0062]
Further, when variable speed control of each motor 40 is possible, each color is based on the phase and amplitude information as shown in FIG. 6 obtained by the speed unevenness detection unit 45 based on the output of the pattern detection unit 43. The speed control is performed so as to cancel out the speed unevenness, that is, in the opposite phase to that of FIG. As a result, as shown in FIG. 9, the speed unevenness of the electrophotographic photosensitive drums 1a, 1b, 1c, and 1d can be greatly improved, and a full-color image forming apparatus without color misregistration can be realized.
[0063]
FIG. 10 shows a color image forming apparatus according to the second embodiment. As an electrophotographic photoreceptor A conveyor belt 111 is stretched over the electrophotographic photosensitive drum 101 (101a, 101b, 101c, 101d) so as to transfer a toner image formed on the surface of each electrophotographic photosensitive drum 101 to a transfer material.
[0064]
On the other hand, the transfer material fed from the feeding cassette 117 by the pickup roller 118 is separated and fed one by one by a separation means (not shown), and then sent to the registration roller pair 119b by the conveying roller pair 119a, and the registration roller pair 119b. Thus, the toner image is conveyed to the conveyor belt 111 at a predetermined timing, and a toner image is transferred from each electrophotographic photosensitive drum 101.
[0065]
The transfer material onto which the toner image has been transferred is fixed by the fixing means 120 and then conveyed by the discharge roller pair 123 to be discharged onto a discharge tray 124 provided at the top of the apparatus main body.
[0066]
The drive unit of each electrophotographic photosensitive drum 101 is positioned on the left side of the machine and applies a rotational driving force to the electrophotographic photosensitive drums 101a, 101b, 101c, and 101d of the four color process cartridges arranged in the substantially horizontal direction. Each process cartridge includes an electrophotographic photosensitive drum 101, a developing device, a cleaning unit, and the like, and supplies all of these driving forces.
[0067]
Each process cartridge is detachable for each color independently, and the driving force transmission unit is also arranged for each color independently in a substantially horizontal direction. The rotation transmission means of each electrophotographic photosensitive drum 101 is connected to the device of the color image forming apparatus. The coupling unit that transmits the rotational driving force from the driving force transmitting member of the main body is the same as that shown in FIGS. 2 to 4 and has a control unit similar to the control unit shown in FIG.
[0068]
In the color image forming apparatus having the structure in which the four electrophotographic photosensitive drums are horizontally arranged in this way, the apparatus main body side and each electrophotographic photosensitive drum are coupled by the coupling having the first and second engaging portions. By reproducing this phase, as in the first embodiment, it is possible to reduce the waiting time of the user when attaching or detaching the process cartridge, and to realize a color image forming apparatus excellent in usability.
[0069]
【The invention's effect】
Since this invention is comprised as mentioned above, there exists an effect as described below.
[0070]
Electrophotographic photosensitive member drive unit and process cartridge of image forming apparatus body By providing a coupling with extremely high accuracy and no phase shift between them, it is possible to simplify the color misalignment adjustment work associated with the attachment and detachment of the process cartridge, and to greatly reduce the waiting time of the user.
[0071]
As a result, there is no color misregistration and user-friendly high-quality, high-performance image forming equipment. Place Can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a color image forming apparatus according to a first embodiment.
2 is a perspective view showing a drive unit of the electrophotographic photosensitive drum of FIG. 1. FIG.
3 is a schematic cross-sectional view showing a relationship between a shaft end portion of the electrophotographic photosensitive drum of FIG. 1 and a driving unit of FIG.
FIG. 4 is a perspective view showing a driving portion and a coupling portion of an electrophotographic photosensitive drum.
FIG. 5 is a diagram illustrating a configuration of a control unit of an electrophotographic photosensitive drum.
FIG. 6 is a graph showing a color shift of each color before adjustment.
FIG. 7 is a graph showing a signal obtained by detecting a rotational phase of a driving force transmission member by a phase detection device.
FIG. 8 is a graph showing the color shift of each color after adjusting the axial phase.
FIG. 9 is a graph showing color misregistration of each color after motor speed control.
FIG. 10 illustrates a color image forming apparatus according to a second embodiment.
[Explanation of symbols]
1 (1a, 1b, 1c, 1d), 101 (101a, 101b, 101c, 101d) electrophotographic photosensitive drum
2 (2a, 2b, 2c, 2d) Charging device
3 (3a, 3b, 3c, 3d) Scanner unit
4 (4a, 4b, 4c, 4d) Development device
5 Electrostatic transfer device
6 (6a, 6b, 6c, 6d) Cleaning device
7 (7a, 7b, 7c, 7d) Process cartridge
8 (8a, 8b, 8c, 8d) Polygon mirror
9 (9a, 9b, 9c, 9d) Imaging lens
10 (10a, 10b, 10c, 10d) Developing roller
11 Electrostatic transfer belt
12 (12a, 12b, 12c, 12d) Transfer roller
16 Paper feeder
20 Fixing part
24 Paper output unit
30 (30a, 30b, 30c, 30d) Driving force transmission member
31a gear
31b Shaft
31c Driving side coupling
31d spiral hole
31e protrusion
31f Boss
32 cylinders
33 leaf spring
34 Drum shaft
35 parallel pins
36 Bearing
37 Driven side coupling
37a Spiral shape part
37b recess
37c Center hole
40 (40a, 40b, 40c, 40d) Motor
41 (41a, 41b, 41c, 41d) target
42 (42a, 42b, 42c, 42d) Phase detector
43 Pattern detector
44 Control circuit
45 Speed unevenness detector
46 Calculation unit
47 Motor controller
48 axis phase detector
111 Conveyor belt
117 Feed cassette
120 Fixing means
124 Output tray

Claims (4)

An image forming apparatus for forming an image on a recording medium,
(A) a motor;
(B) an electrophotographic photosensitive member and a driven-side coupling provided at an end of the electrophotographic photosensitive member for transmitting a rotational driving force from the motor to the electrophotographic photosensitive member, A plurality of process cartridges having a spiral-shaped portion having a twisted shape and a driven side coupling having a central hole having a recess ;
Transmitting the rotational driving force to each of the electrophotographic photosensitive member (c) a plurality of said process cartridge has said a plurality of drive-side coupling for coupling the driven side coupling, and the spiral-shaped portion A drive-side coupling having a helically shaped hole having a substantially triangular prism twist shape for transmitting the rotational driving force to the electrophotographic photosensitive member to be fitted ;
(D) a boss that engages with the center hole disposed in the spiral hole, and the driven side coupling and the driven side coupling are coupled when the driven side coupling and the driven side coupling are coupled to each other; a boss having the order, a projection for engaging with said recess to couple said drive side coupling at a predetermined rotational phase,
(E) axial phase detection means for directly detecting the rotational phase of each of the drive side couplings;
(F) angular velocity fluctuation detecting means for detecting periodic velocity unevenness of the electrophotographic photosensitive member by reading an image of a detection pattern transferred by each of the electrophotographic photosensitive members;
(G) rotation control means for individually controlling at least one of the rotation speed and rotation phase of each of the plurality of drive side couplings;
An image forming apparatus comprising Rukoto to have a. Said rotation control means, an image according to claim 1, characterized in that to control the rotational speed and rotational phase of the electrophotographic photosensitive member based on the output of the angular speed variation detecting means when replacing the process cartridge Forming equipment. Image according to claim 1 or 2, wherein the rotation control means, and controlling the rotational phase of the electrophotographic photosensitive member based on the output of the shaft phase detecting means upon detaching the same said process cartridge Forming equipment. The image forming apparatus according to 3 any one claims 1, characterized in that the process cartridge replacement detecting means for detecting that it has replaced the process cartridge is provided.

Images