JP3583379B2 - Color image recording device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a color image recording apparatus applicable to a color printer, a color copying machine, a color facsimile, and the like.
[0002]
[Prior art]
The configuration of the conventional color electrophotographic apparatus will be described with reference to Japanese Patent Application Laid-Open No. 62-287264. FIG. 6 is an overall configuration diagram of the conventional color electrophotographic apparatus.
[0003]
In the figure, reference numeral 101 denotes a rotating frame for rotatably supporting the four image forming units 102a, 102b, 102c, and 102d of cyan, magenta, yellow, and black. Rotate to fit.
[0004]
The configuration of each image forming unit containing four color toners is the same, and only the toner is different. The structure of the image forming unit and the image forming process of the image forming unit 102a stopped at the image forming position in FIG. 6 will be described in detail.
[0005]
The image forming unit 102a includes a sensitized organic photoconductor photoconductor 108, a primary charger 110, and a cleaner 111. On the other hand, outside the image forming unit 102a, there is a semiconductor laser device (not shown), and light emitted from this laser is exposed and scanned in the axial direction on the photoconductor 108 by a polygon rotated at a constant speed by a motor. I do. The laser light is focused on the photoreceptor by a lens system (not shown) and has f-θ characteristics. In the figure, reference numeral 104 denotes a folding mirror that changes the traveling direction of laser light.
[0006]
A semiconductor laser is modulated by an image signal, the photosensitive member is exposed according to the signal, and the electrostatic latent image is developed by a developing unit 109. On the other hand, the transfer material is fed by a feed roller, and is uniformly wound around the surface of the transfer drum 112. A corona having a polarity opposite to that of the toner is applied from behind to the wound transfer material by a transfer charger 113, and the toner on the photoconductor 108 is transferred to the transfer material.
[0007]
The toner remaining after the transfer is collected by the cleaner unit 111 and stored in the cleaner unit 111. The photosensitive member 108 whose surface has been cleaned receives light on the drum by the pre-exposure illuminating means 105 to reduce various memories accumulated in the photosensitive member 108, and the photosensitive member 108 stops rotating. Next, the rotating frame is rotated by 90 ° and each image forming unit is rotated by 90 °, whereby the image forming unit 102b moves to the lowest image forming position, stops, and is fixed.
[0008]
Next, an image is created using the image forming unit 102b. To this end, the semiconductor laser is modulated according to an image signal corresponding to the color of the toner of the image forming unit 102b, a latent image is formed on the image forming unit 102b, development is performed, and the image on the transfer material wound around the transfer drum 112 is formed. Is transferred onto the toner. The following process is the same as that of the image forming unit 102a.
[0009]
As described above, the image forming process is performed for each of the four image forming units, and the toners of the four colors are stacked on the transfer material on the transfer drum 112. The transfer material onto which the four color toners have been transferred is separated from the transfer drum 112 and fixed by a fixing device.
[0010]
This is the configuration described in Japanese Patent Application Laid-Open No. 62-287264.
[0011]
[Problems to be solved by the invention]
A color electrophotographic apparatus was constructed using such a configuration of the rotating portion of the image forming unit of the conventional example, and a full-color image was formed in the order of black, cyan, magenta, and yellow. When color printing was continued for about 2,000 sheets, the toner overflowed from the cleaner 111 of the yellow image forming unit 102, and a cleaning failure occurred. At this time, when the cleaner 111 of the yellow image forming unit was examined, it was found that the cleaning was defective even though the cleaner 111 had a sufficient waste toner storage capacity. At this time, as shown in FIG. 7, it was found that the waste toner 114 was aggregated and solidified under the cleaning blade 115, and the scraping force of the cleaning blade 115 for scraping off the toner from the photoconductor was reduced. Further, when the waste toner 114 was examined, many yellow, black, cyan and magenta toners were included in the yellow image forming units. It was found that the toner in which these four colors were mixed was significantly inferior in fluidity to the yellow toner alone.In an apparatus using an intermediate transfer belt unit, the cleaning roller is brought into contact with the intermediate transfer belt, and a voltage of -1 kV is applied to smooth the surface of the cleaning roller and prevent toner from adhering. It is desirable not to disturb the toner image on the belt.
[0013]
The present invention has been made in view of the above problems,A toner image can be formed without disturbance,An object of the present invention is to provide a color image recording apparatus capable of always forming a stable image.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, a color image recording apparatus according to the present invention has a rotating body in which a plurality of individual units each having a color toner accommodating portion are collectively arranged in a substantially columnar shape, and formed on a photoconductor. In the color image recording apparatus that transfers the image thus formed to the recording paper via the intermediate transfer body,
The peripheral length of the intermediate transfer member is longer than a length obtained by adding a half of the peripheral length of the photosensitive member to the length in the paper feeding direction of the maximum paper size. The length from the transfer position to the position of the cleaning member for removing the toner image remaining on the intermediate transfer body is reduced by the length in the paper feeding direction of the maximum paper size from the circumference of the intermediate transfer body. Shorter than the length.
Further, the intermediate transfer body of the present invention has a rotating body in which a plurality of individual units partially having a color toner storage section are collectively arranged in a substantially cylindrical shape, and an image formed on a photoconductor is transferred to the intermediate transfer body. In an intermediate transfer member used for a color image recording device for transferring to recording paper through a body,
The circumferential length is longer than a length obtained by adding a half of the circumferential length of the photoconductor to the length in the paper feeding direction of the maximum paper size, and the circumferential length from the transfer position to the recording paper in the intermediate transfer body. The length to the position of the cleaning member for removing the toner image remaining on the intermediate transfer body is shorter than the length obtained by subtracting the length of the maximum paper size in the paper feed direction from the circumference of the intermediate transfer body, It is characterized by the following.
Further, the color image recording apparatus of the present invention has a plurality of developing devices partially having a color toner storage unit,
A photoreceptor,
And an intermediate transfer member,
The peripheral length of the intermediate transfer member is longer than a length obtained by adding a half of the peripheral length of the photosensitive member to the length in the paper feeding direction of the maximum paper size. The length from the transfer position to the position of the cleaning member for removing the toner image remaining on the intermediate transfer body is reduced by the length in the paper feeding direction of the maximum paper size from the circumference of the intermediate transfer body. Shorter than the length.
Further, the intermediate transfer body unit of the present invention, a plurality of developing devices partially having a color toner storage unit,
A photoreceptor,
An intermediate transfer member, which is used in a color image recording apparatus having an intermediate transfer member,
The circumferential length is longer than a length obtained by adding a half of the circumferential length of the photoconductor to the length in the paper feeding direction of the maximum paper size, and the circumferential length from the transfer position to the recording paper in the intermediate transfer body. The length to the position of the cleaning member for removing the toner image remaining on the intermediate transfer body is shorter than the length obtained by subtracting the length of the maximum paper size in the paper feed direction from the circumference of the intermediate transfer body, It is characterized by the following.
According to the above configuration,A toner image can be formed without disturbance,It is possible to provide a color image recording apparatus that can always form a stable image.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
A color image recording apparatus according to a first aspect of the present invention includes a photoreceptor that rotates at least, a developing unit having a toner of a different color and a cleaner unit, and a toner image of a different color on the photoreceptor. A plurality of movable image forming units, a plurality of image forming units arranged in a ring shape, and a rotatable movable image forming unit group; and an intermediate transfer receiving a toner image formed on the photoconductor. A color image forming apparatus comprising: a body, a single exposure position and a single transfer position, wherein the image forming unit and the intermediate transfer body are in contact with each other to form an image. A color electrophotographic apparatus having a configuration in which an image forming operation is performed in a state in which the developing unit is disposed above the body axis in the direction of gravity and the cleaner unit is disposed below the axis of gravity.
Further, the following configuration may be adopted.
A color image recording apparatus according to another aspect of the present invention includes a photoconductor that rotates at least, a developing unit having a toner of a different color, and a cleaner unit, and forms toner images of different colors on the photoconductor. A plurality of movable image forming units to be formed, a plurality of image forming units arranged in a ring shape, and a rotatable movable image forming unit group; and an intermediate transfer member for receiving a toner image formed on the photoconductor. A color electrophotographic apparatus comprising a single exposure position and a single transfer position, wherein the image forming unit and the intermediate transfer member are in contact with each other to form an image, and wherein the image forming unit is The color electrophotographic apparatus has a configuration in which an image forming operation is performed in a state where the image forming operation is arranged above the axis of the unit group in the direction of gravity.
[0016]
The configuration and operation of a color electrophotographic apparatus using an intermediate transfer body unit as an intermediate transfer body will be described with reference to FIG. Reference numeral 1 denotes an outer casing of the color electrophotographic printer, and a right end face side in the drawing is a front face. Reference numeral 1A denotes a printer front plate. The front plate can be freely opened and closed and raised and closed with respect to the printer outer casing 1 around a lower hinge shaft 1B. The state in which the front plate 1A is folded down and opened is indicated by a chain line. The operation of attaching / detaching the intermediate transfer unit 2 to / from the inside of the printer, maintenance inside the printer such as when a paper jam occurs, etc. is performed by opening the front plate 1A to open the inside of the printer. The attachment / detachment operation of the intermediate transfer unit 2 is designed so as to be in a direction perpendicular to the rotation axis generatrix direction of the photoconductor, that is, in the direction of the printer front plate 1A. The intermediate transfer body unit 2 includes a transfer belt 3, a first transfer roller 4, a second transfer roller 5, a cleaning roller 6, a scraper 7, a waste toner reservoir 8, a waste toner full detector 9, a backup roller 10, and a position detector 11. , A tension roller 12, a front cover 13, and a rear cover 14. Details will be described later.
[0017]
At the center of the left side of the printer, four fan-shaped image forming units 15Bk, 15Y, 15M, and 15C for each color of black, cyan, magenta, and yellow form an image forming unit group 16, and form an annular shape as shown in the figure. Are located. Each image forming unit is detachable at a predetermined position of the image forming unit group 16 by opening the printer left face plate 1C of FIG. 1 around the hinge shaft 1D. When the image forming unit 15 is properly mounted in the printer, the mechanical drive system and the electric circuit system on both the image forming unit side and the printer side are connected via a mutual coupling member (not shown). And mechanically and electrically integrated.
[0018]
The image forming units 15Bk, 15C, 15M, and 15Y arranged in an annular shape are supported by a support (not shown), and are driven by a moving motor 17 as moving means as a whole, and fixed. It is configured to be rotatable about a cylindrical shaft 18 that is not rotated. At the time of image formation, each image forming unit can be sequentially positioned at an image forming position 19 facing the first transfer roller 4 supporting the above-described intermediate transfer belt 3 by rotational movement. The image forming position 19 is also an exposure position by the signal light 20.
[0019]
FIG. 2 shows the black image forming unit 15Bk in detail. Each image forming unit is made of the same constituent members except for the developer put in the image forming unit. Therefore, for simplification of description, the image forming unit 15Bk for black will be described, and other colors will be omitted. Note that the same reference numerals are assigned to the same parts for each color, and when it is necessary to distinguish the configuration of each color, a letter indicating each color is added to the code. In this description, the development method applied by the inventors to Japanese Patent Application Laid-Open No. 4-43759 is used, but it goes without saying that any development method may be used as long as it is a development method used in normal electrophotography. For example, a magnetic brush developing method, an elastic rubber roller developing method, a jumping developing method, an impression developing method, or the like can be used. In FIG. 2, reference numeral 21 denotes an organic photoreceptor mainly composed of a polycarbonate-based binder resin using phthalocyanine as a photosensitive material; 22, a non-rotating magnet fixed coaxially with the photoreceptor 21; Reference numeral 20 denotes a laser beam signal light; 24, an exposure window which is an opening of the image forming unit where the laser beam enters the image forming unit; and 25, a developer hopper. In the developer hopper 25, a two-component developer 28Bk obtained by mixing 10% of a ferrite carrier 26Bk having a particle diameter of 50 μm coated on the surface with a silicone resin and a negatively chargeable black toner 27Bk in which a black pigment is dispersed in a polyester resin is mixed. , And is directly attached to the surface of the photoconductor 21 by the magnetic force of the magnet 22. 29 is a rotatable aluminum collection electrode roller, 30 is a coaxially fixed non-rotating magnet inside, 31 is a scraper made of phosphor bronze that scrapes toner collected on the collection electrode roller 29, and 32 is a collection This is an AC high-voltage power supply that applies a voltage to the electrode roller 29. Reference numeral 33 denotes a cleaner for cleaning the toner remaining on the surface of the photoconductor 21 after the transfer. The photoreceptor 21 was 30 mm in diameter and rotated in the direction of the arrow at a peripheral speed of 60 mm / s, and the recovery electrode roller 29 was 16 mm in diameter and was also rotated in the direction of the arrow at a peripheral speed of 60 mm / s.
[0020]
Next, the configuration of the intermediate transfer body unit 2 will be described with reference to FIG. The intermediate transfer body unit 2 cleans the unit housing 2a with an intermediate transfer belt 3, a first transfer roller 4 formed of an aluminum roller, a second transfer roller 5 formed of a conductive elastic rubber roller, and a toner image remaining on the intermediate transfer belt 3. Aluminum cleaning roller 6, scraper 7 for scraping collected toner, waste toner reservoir 8 for storing scraped toner, and waste toner full detection for detecting that the amount of toner in waste toner reservoir 8 is full. Device 9, a backup roller 10 made of conductive rubber facing the cleaning roller 6, a position detector 11 for detecting the transfer start position of the intermediate transfer belt 3, and a tension roller 12 for adjusting the tension of the intermediate transfer belt 3 and preventing meandering. , Is included. The intermediate transfer body unit 2 is detachable from a predetermined storage portion in the printer outer casing 1 by opening the printer front plate 1A in FIG.
[0021]
When the intermediate transfer unit 2 is mounted on the printer main body, the first transfer roller 4 is at the retreat position 4b in FIG. 3 where the intermediate transfer belt 3 does not contact the photoconductor 21. When the intermediate transfer body unit 2 is mounted on the printer main body and the image forming operation is started, the first transfer roller 4 moves to the transfer position 4a, and the intermediate transfer belt 3 is pressed against the photoconductor 21 with a force of about 1.0 kg. Is done.
[0022]
When the intermediate transfer unit 2 is located in a predetermined storage section of the printer and used for image formation, the front cover 13 and the rear cover 14 move to the positions shown in FIG. When the intermediate transfer unit 2 is taken out of the printer, the front cover 13 and the rear cover 14 move to positions 13a and 14a indicated by dotted lines to protect the surface of the intermediate transfer belt 3.
[0023]
The intermediate transfer belt 3 is a 100 μm-thick endless belt-shaped film made of semiconductive (medium resistance) urethane as a base material, and a surface layer made of a fluororesin such as PFA / PTFE and having a total thickness of 100 to 500 μm. Consisting of The intermediate transfer belt 3 is wound around a first transfer roller 4, a second transfer roller 5, a backup roller 10, and a tension roller 12, and is configured to be movable in an arrow Y direction.
[0024]
Here, the circumferential length of the intermediate transfer belt 3 is a length (62 mm) slightly longer than half of the circumferential length of the photosensitive drum 21 (diameter 30 mm) to the longitudinal length (298 mm) of A4 paper, which is the maximum paper size. ) Is set to 360 mm. At this time, the circumferential length of the intermediate transfer belt 3 from the contact portion between the second transfer roller 5 and the third transfer roller 34 to the contact portion between the cleaning roller 6 and the backup roller 10 is shorter than the distance of 62 mm and becomes 55 mm. It is set to be.
[0025]
The moving speed of the intermediate transfer belt 3 is set to be 1.5% faster than the image forming speed of the image forming unit 15 (60 mm / s equal to the peripheral speed of the photoreceptor 21) in order to prevent the hollow transfer of the toner image. Have been.
[0026]
The second transfer roller 5 and the backup roller 10 are both made of conductive rubber, and are grounded via 20 MΩ resistors 35 and 36, respectively, in order to prevent scattering during transfer of the color toner image.
[0027]
The medium-resistance elastic layer of the second transfer roller 5 and the backup roller 10 is formed by mixing and dispersing carbon or metal oxide in an elastic material such as silicon rubber, Teflon (R) rubber, chloroprene rubber, urethane rubber, or EPDM. Electric resistance (volume resistivity) is 10⁵-10¹⁷It consists of a solid or foamed layer treated to have a medium resistance of Ωcm.
[0028]
The first transfer roller 4 is movable between a transfer position 4a and a retreat position 4b. When the first transfer roller 4 is located at the transfer position 4a by a driving source (not shown) controlled by an electric signal, the intermediate transfer belt 3 is moved. The toner image formed in contact with the photoconductor 21 can be transferred, and when located at the transfer position 4b, the intermediate transfer belt 3 moves away from the photoconductor 21 to a non-contact position.
[0029]
When transferring the toner image on the photoconductor 21, a voltage of about +2.5 kV (100 μA) is applied to the first transfer roller 4 and the tension roller 12 by the high voltage power supply 37. At this time, if the first transfer roller 4 is brought into direct contact with the photoconductor 21 to transfer the toner image to the intermediate transfer belt 3, a so-called “forward jump” phenomenon occurs before the intermediate transfer belt 3 comes into contact with the photoconductor 21. The image is disturbed, and it becomes difficult to uniformly adjust the contact pressure between the first transfer roller 4 and the photoconductor 21. However, when the first transfer roller 4 is moved and the intermediate transfer belt 3 stretched between the two rollers is brought into contact with the photosensitive drum 21 as in the present invention, these problems do not occur.
[0030]
The third transfer roller 34 made of aluminum is in pressure contact with the second transfer roller 5 via the intermediate transfer belt 3. While a color image is being formed on the intermediate transfer belt 3, a voltage of -1 kV is applied by the high voltage power supply 38a in order not to disturb the toner image on the belt. When transferring the color toner image onto the image receiving paper (recording paper) 39, a voltage of +3 kV is applied by the high voltage power supply 38b. The configuration of the third transfer roller 34 may be a conductive elastic roller like the second transfer roller 5, but a metal image having a smooth surface is used to synthesize a color image on the intermediate transfer belt 3. This is more preferable because the surface of the toner image is not disturbed during the operation.
[0031]
Reference numeral 40 denotes a static elimination needle for preventing the toner image from being disturbed when the paper 39 is separated from the intermediate transfer belt 3. The third transfer roller 34 is configured to be rotatable 1.5% slower than the intermediate transfer belt 3 in order to prevent a hollow phenomenon when transferring a toner image.
[0032]
The cleaning roller 6 cleans the intermediate transfer belt 3. During the formation of a color image on the intermediate transfer belt 3, a voltage having the same polarity as the toner, that is, a negative voltage here, is supplied from the high voltage power supply 41 a to the cleaning roller 6 in order to prevent the toner from transferring from the intermediate transfer belt 3. Has been applied. When cleaning the toner remaining on the intermediate transfer belt 3, a positive voltage for electrostatically attracting the toner is applied by the high voltage power supply 41b.
[0033]
FIG. 4 is a perspective view showing a configuration of the position detector 11 using a photo interrupter provided inside the intermediate transfer body unit 2. A detection hole 42 is provided at the end of the intermediate transfer belt 3, and the position detector 11 determines the leading end position of the toner image by optically detecting the passage of the detection hole 42, and This is a configuration for performing color image alignment.
[0034]
Returning to FIG. Reference numeral 43 denotes a laser beam scanner disposed on the upper side of the inside of the printer outer casing 1, and includes a semiconductor laser, a scanner motor 43a, a polygon mirror 43b, a lens system 43c, and the like. The pixel laser signal light 20 corresponding to the time-series electrical pixel signal of the image information from the scanner unit 43 passes through the optical path window 44 formed between the image forming units 15Bk and 15C in FIG. The light enters a mirror 46 fixed in the shaft 18 through a window 45 opened in the section, is reflected and enters the image forming unit 15Bk from the exposure window 24 of the image forming unit 15Bk at the image forming position 19 to form an image. The light passes through a passage between a developer reservoir 25 and a cleaner 33 disposed vertically in the unit and is incident on an exposure portion on the left side surface of the photosensitive drum 21 to be scanned and exposed in the generatrix direction.
[0035]
Here, since the optical path from the optical path window 44 to the mirror 46 uses the gap of the wall surface between the adjacent image forming units 15Bk and 15C, the image forming unit group 16 has almost no wasteful space. Further, since the mirror 46 is provided at the center of the image forming unit group 16, the mirror 46 can be constituted by a single fixed mirror, and has a simple configuration and easy alignment.
[0036]
Reference numeral 34 denotes a third transfer roller disposed inside the printer front plate 1A and above the feeding roller 47, and a nip portion where the intermediate transfer belt 3 and the third transfer roller 34 are pressed against each other is attached to the printer front plate 1A. The paper transport path is formed so that the paper is fed by a paper feed roller 47 provided below the printer.
[0037]
Reference numerals 48a and 48b denote fixing rollers provided on the upper inside of the printer, and a halogen lamp 49 is provided inside 48a. A polyimide film 50 is stretched between 48a and 49b. This film 50 is used for the purpose of giving gloss of a color print. Reference numeral 51 denotes a backup roller provided to face the fixing roller 48a, and reference numeral 52 denotes a pair of paper discharge rollers provided on the paper exit side. The above is the description of the main configuration of the color electrophotographic apparatus of the present invention.
[0038]
Next, the configuration and operation when the image forming unit 15 and the intermediate transfer body unit 2 are replaced will be described. The state shown in FIG. 1 is a state in which an image is being formed. This is a state in which the first transfer roller 4 has moved to the position 4a in FIG. 3 in order to transfer the toner image formed on the photoconductor 21 to the intermediate transfer belt 3. When the image forming unit group 16 is rotationally moved or when the printer is stopped, the first transfer roller 4 is retracted to the position 4b. In this state, the photoconductor 21 does not contact the intermediate transfer belt 3. In this retracted state, the printer stops the printing operation, and by opening the printer front plate 1A, the replacement of the intermediate transfer body unit 2 can be taken out. Even if the intermediate transfer body unit 2 is moved in and out in this state, the photoconductor 21 and the intermediate transfer belt 3 are not strongly pressed during the operation, and both are not damaged. At the same time, by opening the left face plate 1C of the printer, replacement of each image forming unit 15 can be taken out. When replacing another image forming unit 15, the image forming unit group 16 stops rotating 90 ° from this state.
[0039]
The surface of the intermediate transfer belt 3 gradually deteriorates due to toner sticking or the like as it is used for a long time. If the deterioration of the belt becomes remarkable, an image is partially chipped or white streaks or black streaks occur in the image. For this reason, it is desirable to replace this intermediate transfer belt before it deteriorates and affects the image. However, it is extremely difficult to automatically detect the deterioration phenomenon of the intermediate transfer belt in the printer. In the present invention, as shown in FIG. 3, the intermediate transfer belt 3 and the waste toner reservoir 8 are integrated into a unit, and the waste toner is simultaneously discarded when the intermediate transfer belt 3 is replaced. In such a configuration, the size of the waste toner reservoir 8 may be designed to be a small eye volume so that the waste toner reservoir 8 is filled with waste toner before the end of the life of the intermediate transfer belt 3. Thus, before the intermediate transfer belt 3 is deteriorated and an image defect occurs, the waste toner full detector 9 installed inside the waste toner reservoir detects that the toner is full, and instructs the user to replace the intermediate transfer body unit 2. can do. Such a configuration is not only effective for an intermediate transfer belt on which a toner image is directly formed, but is similarly effective for an intermediate transfer body having a configuration in which an image receiving paper is wound around.
[0040]
With the above configuration, the photosensitive member 21 of the image forming unit 15 does not come into contact with the intermediate transfer belt 3 during the rotational movement operation of the image forming unit group, so that the photosensitive member 21 is not damaged. Further, since the intermediate transfer belt 3 does not come into direct contact with the photoconductor 21 when the intermediate transfer unit 2 is replaced, the photoconductor 21 is not damaged during maintenance.
[0041]
Further, in this method, the position of the intermediate transfer belt 3 is fixed, and the image forming unit 15 is moved to the transfer position at the time of image formation, and the exposure position on the photoconductor 21 And the color registration accuracy at the time of color image composition is improved.
[0042]
In the color electrophotographic apparatus having such a configuration, defective cleaning which occurs in the related art occurs due to the following causes.
[0043]
First, the phenomenon in which toner of another color is mixed in the yellow image forming unit will be described. In a color electrophotographic apparatus using a powder toner, a single color image is superposed on an image receiving paper or an intermediate transfer member to form a full color image. At this time, the intermediate color image is a powder toner image that has not been fixed. Therefore, when the toner image is transferred from the photoreceptor onto the image receiving paper or the intermediate transfer member, the toner image of another color previously transferred on the photoreceptor side is partially reverse-transferred to form another color image. Get into the cleaner part of the unit. Even the previously used black, cyan and magenta toners enter the cleaner in the yellow image forming unit used last.
[0044]
All the color toners of each color use the same polarity, that is, a toner that is negatively charged in this case. However, since different pigments are used, the easiness of charging and the charge amount are different. When the toners mix with each other inside the cleaner, they cause triboelectric charging and electrostatically aggregate. The toner in such a state has very poor fluidity and tends to stay inside the apparatus.
[0045]
This state will be described in more detail with reference to FIG. 5A is a state in which the image forming unit 15 is located below the axis 18 of the image forming unit group 16 in the direction of gravity. This state is the image forming position in the conventional example shown in FIG. At the lower position of the photoconductor 21 in FIG. 5A, each color toner image is transferred to an intermediate transfer body (not shown). At this position, when the image forming units were exchanged in the order of black, cyan, magenta, and yellow to perform full-color image formation, the last yellow image forming unit first failed in cleaning. This is because not only the yellow toner but also the black, cyan, and magenta toners on the intermediate transfer body transferred earlier accumulate in the cleaner unit 33. The waste toner 54 in which the four types of toners are mixed causes frictional charging with each other, aggregates, and stays below the cleaner unit 33 as shown in FIG. The waste toner 54 gradually presses the cleaning blade 55 from behind. Since the cleaning blade 55 is made of an elastic material such as urethane rubber, if an excessive pressure is applied from behind, the cleaning blade 55 does not uniformly contact the photoconductor 21 and causes cleaning failure.
[0046]
It has been found that the frequency of occurrence of such a cleaning failure phenomenon due to the pressure of the waste toner 54 inside the cleaner 33 greatly depends on what image forming position the image forming unit is used.
[0047]
Next, the image forming unit group 16 is rotated by 90 °, and an image forming state of the image forming unit 15 at the position of FIG. In this state, the cleaner 33 is located above the photoconductor 21, and the developer hopper 25 is located below. When an image is formed in this state, the waste toner 54 in the cleaner 33 directly presses the cleaning blade 55 in the direction of gravity, and this is a bad position where cleaning failure is most likely to occur. In addition, it is difficult to supply the developer 28 in the developer hopper 25 to the developing section, which is not preferable.
[0048]
5C in which the image forming unit group 16 is further rotated by 90 °, the image forming unit 15 is positioned above the axis 18 of the image forming unit group 16 in the direction of gravity to form an image. It is. In this state, the waste toner 54 does not stay at the tip of the cleaning blade 55 inside the cleaner section 33 and hardly affects the cleaning performance. In this configuration, it is somewhat difficult to supply the developer 28 to the developing section. However, if the supply of the developer is devised, the present invention can be obtained.
[0049]
5D also has a configuration in which the waste toner 54 does not directly press the cleaning blade 55 inside the cleaner section 33. In addition, since the developer hopper 25 is located above the gravitational direction, it is easy to supply the developer 28 to the developing section.
[0050]
Further, when the toner is transferred from the photoreceptor 21 to the intermediate transfer belt 3, even if the toner spills downward from the image forming unit 15 in the direction of gravity, the image forming positions of (C) and (D) of the present invention are directly Does not fall on the image. Therefore, there is also an advantage that there is little fear of image contamination.
Further in the present invention, Can form toner images without disturbance,It is possible to provide a color image recording apparatus that can always form a stable image.
[0051]
【Example】
(Specific Embodiment 1) The operation of a color electrophotographic apparatus according to an embodiment of the present invention will be described below with reference to the drawings.
[0052]
The printer in FIG. 1 is in an image forming state. The operation of the image forming unit 15Bk will be described with reference to FIG. The photoconductor 21 was charged to −450 V by the charging roller 23. The photosensitive member 21 was irradiated with the laser beam scanning light 20 to form an electrostatic latent image. At this time, the exposure potential of the photoconductor 21 was -50V. On the surface of the photoconductor 21, a two-component developer 28Bk was adhered by magnetic force in a developer hopper 25. Next, the surface of the photoconductor 21 was passed in front of the collection electrode roller 29. When the photosensitive member 21 passes through the uncharged area, the AC voltage of 750 V0-p (1.5 kV peak-to-peak), on which a DC voltage of +100 V is superimposed, is applied to the electrode roller 29 by the AC high-voltage power supply 32. Mold wave) was applied. Thereafter, when passing through the surface of the photoreceptor 21 on which the electrostatic latent image is written and charged to -450 V, the electrode roller 29 is superposed by a high voltage power supply 32 on which a DC voltage of -250 V is superimposed. An AC voltage (peak wave having a frequency of 2 kHz) having a peak of 1.5 kV was applied. Then, the developer on the photoconductor 21 and the toner adhering to the non-image portion were collected by the electrode roller 29, and a negative-positive toner image was left on the photoconductor 21 only in the image portion. The developer and toner adhered to the electrode roller 29 rotating in the direction of the arrow were scraped off by the scraper 31, returned to the developer hopper 25 again, and used for the next image formation. Thus, a black toner image was obtained on the photoconductor 21. Similar operations are performed for the other developing units 15C, 15M, and 15Y other than black.
[0053]
Next, returning to FIG. 1, the operation of the apparatus when forming a color image will be described. The image forming unit group 16 is at the position shown in FIG. 1, and the black image forming unit 15Bk is at the image forming position 19 as shown. At this time, the photoconductor 21 is in contact with the intermediate transfer belt 3. In the image forming step of the image forming unit described above, the black signal light is input to the image forming unit 15Bk by the laser exposure device 43, and the image is formed by the black toner. At this time, the moving speed of the intermediate transfer belt 3 is set to be 1.5% faster than the speed of the photoconductor 21 in order to prevent the hollow transfer of the toner image. The black toner image is transferred onto the intermediate transfer belt 3 by the action of the voltage applied to the tension roller 12. At this time, a DC voltage of +2.5 kV was applied to the first transfer roller 4 and the tension roller 12 as described above.
[0054]
Immediately after all the black toner images have been transferred, the first transfer roller 4 moves from the position 4a to the position 4b shown in FIG. 3, and the intermediate transfer belt 3 returns to a position where it does not contact the image forming unit 15Bk. . Next, as a whole, the image forming unit group 16 is driven by the moving motor 17 to rotate and move in the direction of arrow Q in FIG. 1 and stops at the position where the image forming unit 15C reaches the image forming position 19 by rotating exactly 90 °. . The portions of the developer hopper 25 and the cleaner 33 other than the photoconductor of the image forming unit are located inside the rotary arc indicated by the dotted line at the tip of the photoconductor 21. The retreat position 4b of the first transfer roller 4 is located outside the dotted arc. Therefore, the intermediate transfer belt 3 does not come into contact with the image forming units during the rotational movement of the image forming unit group 16.
[0055]
When the rotation of the image forming unit group 16 is completed and the image forming unit 15C reaches the image forming position 19, the laser exposure device 43 inputs a signal light to the image forming unit 15C with a cyan signal, as before, and outputs the cyan light. Is formed and transferred. By this time, the intermediate transfer belt 3 has made one rotation, and the signal from the position detector 11 shown in FIG. 4 has been adjusted so that the next cyan toner image coincides in position with the previously transferred black toner image. Based on the timing, the writing timing of the cyan signal light is controlled. During this time, the third transfer roller 34 is in contact with the intermediate transfer belt 3, but as described above, the surface of the third transfer roller 34 is smooth and a voltage of -1 kV is applied to prevent the toner from adhering. Therefore, the toner image on the intermediate transfer belt 3 is not disturbed. Although the cleaning roller 6 is also in contact with the intermediate transfer belt 3, the surface of the cleaning roller 6 is smooth and a voltage of -1 kV is applied to prevent the toner from adhering. 3 does not disturb the toner image.
[0056]
The same operation as above was performed for magenta and yellow, and the four color toner images were superimposed on the intermediate transfer belt 3 in a position-matched manner to form a color image. After the transfer of the last yellow toner image, the four color toner images were collectively transferred to a sheet (not shown) fed from a sheet feeding cassette by applying a voltage of +3 kV to the third transfer roller 34 in a timely manner. The toner image transferred to the sheet was fixed by fixing rollers 48a and 48b, and then discharged.
[0057]
Such color image formation was continuously performed for about 4000 sheets. However, no cleaning failure occurred in the yellow image forming unit 15Y, and toner did not overflow from the cleaner 33.
[0058]
Thereafter, a voltage of -1 kV was applied again to the third transfer roller 34 to transfer the toner directly attached to the surface of the third transfer roller to the intermediate transfer belt 3. The toner and the transfer residual toner remaining on the intermediate transfer belt 3 were cleaned and recovered by applying a voltage of +3 kV to the cleaning roller 6, and stored in a waste toner reservoir 8 in the intermediate transfer unit 2.
[0059]
When such a printing operation was repeated for about 30,000 sheets, the discharged toner reservoir 8b became full, and the waste toner full detector 9 constituted by an optical sensor output a signal indicating that it was full. At this time, the intermediate transfer belt 3 was in a state where it could be used for printing about 10,000 more sheets.
[0060]
The intermediate transfer body unit 2 in a state where the waste toner reservoir 8b is full with the waste toner is replaced as follows. The image forming unit group 16 is in the state shown in FIG. 1, but the first transfer roller 4 is retracted to the position 4b shown in FIG. Accordingly, the photosensitive member 21 of the image forming unit 15Bk moves to the retracted position where the photosensitive member 21 does not contact the intermediate transfer belt 3 of the intermediate transfer body unit 2, and the apparatus is stopped. The user opens the front plate 1A located at the front of the apparatus main body, and takes out the intermediate transfer unit 2 therefrom. Next, a new intermediate transfer unit having the previously prepared position detector and waste toner full detector adjusted is mounted. Therefore, after the unit is mounted, image formation can be started without any adjustment. When the new intermediate transfer unit is mounted on the main body, the photoconductor 21 of the image forming unit 15Bk does not collide with the intermediate transfer belt 3 or the first transfer roller 4 and is not damaged.
[0061]
The above is the description of the configuration and operation of the embodiment. In the above embodiment, a specific structure of the image forming unit is used. However, the essence and the function and effect of the present invention are also applicable to an image forming unit having a structure using a conventional developing method or a charging method. Does not change. Further, such a configuration is not only effective for an apparatus using an intermediate transfer belt for directly forming a toner image thereon, but is similarly effective for an intermediate transfer body having a configuration in which an image receiving paper is wound around. Needless to say.
[0062]
【The invention's effect】
The present inventionA toner image can be formed without disturbance,It is possible to provide a color image recording apparatus that can always form a stable image.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a positional relationship during image formation of a color electrophotographic apparatus of the present invention.
FIG. 2 is a configuration diagram showing a configuration of an image forming unit used in the color electrophotographic apparatus according to the embodiment of the present invention;
FIG. 3 is a configuration diagram of an intermediate transfer body unit of the present invention.
FIG. 4 is a configuration diagram showing a configuration of a position detector of the intermediate transfer body unit of the present invention.
FIG. 5 is an explanatory diagram illustrating the state of a cleaner and a developer hopper at each rotational position of the image forming unit of the present invention.
FIG. 6 is a configuration diagram of a conventional color electrophotographic apparatus.
FIG. 7 is an explanatory view for explaining a problem of a conventional color electrophotographic apparatus.
[Explanation of symbols]
2 Intermediate transfer unit
3 Intermediate transfer belt
4 First transfer roller
5 Second transfer roller
6 Cleaning roller
10. Backup roller
12 tension roller
15 Image forming unit
16 Image forming unit group
19 Image formation position
20 Laser signal light
21 Photoconductor
25 Developer hopper
33 Cleaner
34 Third transfer roller
43 Laser exposure equipment
55 Cleaning Blade

Claims (4)

It has a rotating body in which a plurality of individual units each having a color toner storage section are collectively arranged in a substantially cylindrical shape, and transfers an image formed on a photoconductor to recording paper via an intermediate transfer body. In a color image recording device,
The circumferential length of the intermediate transfer body, the length of the paper feed direction of the maximum paper size, the photosensitive member of the circumference of the half-length, a well as longer than the length obtained by adding, in the intermediate transfer body, a recording sheet The length from the transfer position to the position of the cleaning member for removing the toner image remaining on the intermediate transfer body is reduced by the length in the paper feeding direction of the maximum paper size from the circumference of the intermediate transfer body. color image recording apparatus according to claim than Shorten the length. It has a rotating body in which a plurality of individual units each having a color toner storage section are collectively arranged in a substantially cylindrical shape, and transfers an image formed on a photoconductor to recording paper via an intermediate transfer body. In an intermediate transfer member used for a color image recording device,
The circumferential length, the length of the paper feed direction of the maximum paper size, the photosensitive member of the circumference of the half-length, a well as longer than the length obtained by adding, in the intermediate transfer body, from the transfer position of the recording sheet The length to the position of the cleaning member for removing the toner image remaining on the intermediate transfer body is shorter than the length obtained by subtracting the length of the maximum paper size in the paper feed direction from the circumference of the intermediate transfer body , An intermediate transfer member, characterized in that: A plurality of developing units partially having a color toner storage unit,
A photoreceptor,
And an intermediate transfer member,
The circumferential length of the intermediate transfer body, the length of the paper feed direction of the maximum paper size, the photosensitive member of the circumference of the half-length, a well as longer than the length obtained by adding, in the intermediate transfer body, a recording sheet The length from the transfer position to the position of the cleaning member for removing the toner image remaining on the intermediate transfer body is reduced by the length in the paper feeding direction of the maximum paper size from the circumference of the intermediate transfer body. A color image recording device, wherein the length is shorter than the length . A plurality of developing units partially having a color toner storage unit,
A photoreceptor,
Intermediate transfer body, and an intermediate transfer body unit used in a color image recording apparatus having
The circumferential length, the length of the paper feed direction of the maximum paper size, the photosensitive member of the circumference of the half-length, a well as longer than the length obtained by adding, in the intermediate transfer body, from the transfer position of the recording sheet The length to the position of the cleaning member for removing the toner image remaining on the intermediate transfer body is shorter than the length obtained by subtracting the length of the maximum paper size in the paper feed direction from the circumference of the intermediate transfer body , An intermediate transfer body unit, characterized in that:

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