JP3943758B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus that forms a color image or a monochrome image using an electrophotographic system.
[0002]
[Prior art]
In recent years, with the widespread use of electrophotographic color image forming apparatuses, there has been an increasing demand for speeding up color output in addition to the demand for recording quality of color images.
In order to meet this demand, several proposals have been made for image forming methods, among which Bk (black) toner, C (cyan) toner, M (magenta) toner, and Y (called tandem type) are used. There is a color image forming system in which each image of a yellow toner is formed on a drum-shaped image carrier, transferred sequentially to each transfer material conveyed by an electrostatic conveyance belt, and finally fixed. .
[0003]
A conventional tandem color image forming apparatus is described in, for example, Japanese Patent Application Laid-Open No. 09-288396. FIG. 5 is a sectional side view showing an example of a tandem type color image forming apparatus. In this color image forming apparatus, a transfer material cassette 50 is mounted on the lower right side of the main body apparatus. The transfer material set in the transfer material cassette 50 is taken out one by one by the paper feed roller 51 and fed to the image forming unit by the pair of transport rollers 52 and 53.
In the image forming unit, an electrostatic conveyance belt 54 that conveys the transfer material is stretched flat in the transfer material conveyance direction (from right to left in FIG. 5) by a plurality of rotating rollers. By applying a bias to the suction roller 55 on the upper surface of the electric transport belt 54, the transfer material is electrostatically attracted to the electrostatic transport belt 54. Further, four photosensitive drums 56 as image bearing members in the form of drums are arranged in a straight line so as to face the belt conveying surface to constitute an image forming unit. Each of the photosensitive drums 56 sequentially surrounds the vicinity of the peripheral surface thereof, and a transfer member 59 is arranged with the charging device 57, the developing device 58, and the electrostatic conveyance belt 54 interposed therebetween. Bk (black) toner, C (cyan) toner, M (magenta) toner, and Y (yellow) toner are placed in the housing of each developing unit 58 from the downstream side in the transfer material conveyance direction (left side in FIG. 5). Each is housed. Further, a predetermined gap is provided between the charger 57 and the developing unit 58, and exposure irradiation is performed from the exposure means 60 to the peripheral surface of the photosensitive drum 56 through this gap.
[0004]
In this color image forming apparatus, when the electrostatic conveyance belt 54 circulates in the counterclockwise direction in the drawing and conveys the transfer material, each charger 57 applies a predetermined charge to the peripheral surface of the photosensitive drum 56 corresponding thereto. The exposure means 60 exposes the peripheral surface of the charged photosensitive drum 56 in accordance with image information to form an electrostatic latent image, and the developing device 58 outputs the electrostatic latent image. The toner is transferred to the low potential portion to form a toner image (development).
[0005]
The toner images formed (developed) on the peripheral surfaces of the photosensitive drums 56 are attracted and transferred to the charges generated on the transferred transfer material by the transfer electric field formed by the transfer members 59 corresponding to the toner images. It is transferred to the material surface. The transfer material onto which the toner image has been transferred is heat-fixed on the paper surface by a fixing unit 61 including a pressure roller and a heat generating roller, and is discharged out of the apparatus by a pair of paper discharge rollers 62.
[0006]
Subsequently, an image forming mode of the apparatus will be described. Image formation is not always determined by multicolor printing, that is, full-color recording, and the frequency of black-color recording, that is, monochrome recording is also quite high. In order to cope with such usage, there has been proposed a tandem type color image forming apparatus capable of switching between full color recording and monochrome recording.
[0007]
FIG. 6A shows a full-color recording, and FIG. 6B shows a monochrome recording. This configuration contacts the inside of the electrostatic conveyance belt 54 and rotates the transfer portion of a color other than black together with the electrostatic conveyance belt 54 with a support roller 63 provided upstream of the black image forming portion as a fulcrum. By moving and retracting, the entrance path from the suction roller 55 and the black image forming unit 64 to the fixing unit 61 does not change between full color recording and monochrome recording, and stable transport performance is obtained in both. Yes.
[0008]
[Problems to be solved by the invention]
In the above apparatus, when black and white output is performed, the yellow, magenta, and cyan photosensitive drums are separated from the electrostatic conveyance belt 54 as shown in FIG. However, when monochrome output is applied to a transfer material such as a strong envelope or thick paper, sufficient electrostatic attraction is not obtained, and the leading register misalignment is caused by the misalignment of the envelope tip before reaching the black photosensitive drum. And problems such as jamming are likely to occur. In particular, in a high-humidity environment, the resistance of the electrostatic conveyance belt 54 and the transfer material is reduced due to moisture absorption, and the electric charge between the transfer material and the electrostatic conveyance belt 54 is likely to escape, so that the transfer material adsorption force is reduced.
[0009]
In order to solve the above problem, it is conceivable to increase the resistance of the electrostatic conveyance belt 54 and increase the attracting force between the transfer material and the electrostatic conveyance belt 54. However, increasing the resistance value causes the electrostatic conveyance belt 54 to be charged up, resulting in poor transferability. When the image-formed transfer material is separated from the electrostatic conveyance belt 54, the transfer material or electrostatic conveyance There is a problem that a special device for forcibly eliminating the static electricity from the belt 54 is required, resulting in an increase in size of the device and an increase in price.
[0010]
The present invention has been made in view of the above-described conventional points, and the object thereof is not influenced by a low-humidity-high-humidity environment without increasing the size of the apparatus and increasing the price, and even a strong transfer material. The present invention provides an image forming apparatus capable of carrying out monochrome output by conveying without causing misalignment, skew, and jam.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a representative configuration according to the present invention includes an image carrier that respectively carries a plurality of color toner images and a transfer material carrier that carries a transfer material, and the plurality of image carriers. In an image forming apparatus capable of sequentially superimposing and transferring the plurality of color toner images on a body onto a transfer material carried on the transfer material carrier, a transfer material to be conveyed is brought into contact with all of the plurality of image carriers. a color recording mode for performing color recording, a first monochrome mode for performing predetermined in contact only one monochromatic recording of the transfer material carrying said plurality of image bearing members, wherein the plurality of the transfer material conveying A second monochrome mode in which monochrome recording is performed in contact with all of the image carrier, and either the first monochrome mode or the second monochrome mode is selected according to the type of transfer material. To do.
[0012]
In the above configuration, when carrying out monochrome recording by transporting a transfer material that is strong and easily lifted from the transfer material carrier, the transfer material is transferred to each image carrier by selecting the second monochrome mode. By carrying the sheet while holding it, it is possible to carry the sheet stably without causing any misalignment, skewing, jamming, or the like of the transfer material, and monochrome recording can be performed.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Next, a multicolor image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.
[0014]
[First Embodiment]
1 and 2 show an image forming apparatus according to the first embodiment, and FIG. 1 is a longitudinal cross-sectional explanatory view showing an overall configuration of a four-color full-color laser beam printer which is an embodiment of a color image forming apparatus. FIG. 2 is an explanatory diagram of a state when image recording is performed.
[0015]
{Overall configuration of image forming apparatus}
First, the overall configuration of the color image forming apparatus will be described with reference to FIG. A color image forming apparatus A shown in FIG. 1 includes photosensitive drums 1 (1a, 1b, 1c, 1d) as four image carriers arranged in parallel in the horizontal direction. The photosensitive drum 1 is rotationally driven in a clockwise direction in FIG. 1 by driving means (not shown). Around the photosensitive drum 1, a charging device 2 (2a, 2b, 2c, 2d) for uniformly charging the surface of the photosensitive drum 1 in order according to the rotation direction, and a laser beam is irradiated on the basis of image information. A scanner unit 3 (3a, 3b, 3c, 3d) for forming an electrostatic latent image on the drum 1, and a developing device 4 (4a, 4b, 4c, 4d) for developing the toner image by attaching toner to the electrostatic latent image ), An electrostatic conveyance transfer device 5 for transferring the toner image on the photosensitive drum 1 to a transfer material, and a cleaning device 6 (6a, 6b, 6c, 6) for removing post-transfer toner remaining on the surface of the photosensitive drum 1 after transfer. 6d) and the like are provided.
[0016]
Here, the photosensitive drum 1, the charging device 2, the developing device 4, and the cleaning device 6 for removing the toner are integrally formed into a cartridge to form a process cartridge 7 (7 a, 7 b, 7 c, 7 d), and color image formation It is detachable from the device A.
[0017]
Next, the configuration of each unit will be described sequentially. The photoconductive drum 1 is configured by applying an organic photoconductive layer (OPC photoconductor) to the outer peripheral surface of an aluminum cylinder having a diameter of 30 mm, for example. Both ends of the photosensitive drum 1 are rotatably supported by a support member, and a driving force from a drive motor (not shown) is transmitted to one end, so that the photosensitive drum 1 is rotated clockwise in the figure. Is done.
[0018]
Each charging device 2 is a conductive roller formed in a roller shape. The roller is brought into contact with the surface of the photosensitive drum 1, and a charging bias voltage is applied to the roller by a power source (not shown). The surface of the body drum 1 is uniformly charged.
[0019]
The scanner unit 3 is arranged in a substantially vertical direction of the photosensitive drum 1, and polygon mirrors 9 (9a, 9b, 9b) in which image light corresponding to an image signal is rotated at a high speed by a scanner motor (not shown) by a laser diode (not shown). 9c, 9d). The image light reflected by the polygon mirror is configured to selectively expose the surface of the charged photosensitive drum 1 through the imaging lens 10 (10a, 10b, 10c, 10d) to form an electrostatic latent image. is doing.
[0020]
Each of the developing devices 4 (4a, 4b, 4c, 4d) is composed of a developer that stores toners of yellow, cyan, magenta, and black in order from the upstream side (right side in FIG. 1) of the transfer material in the transport direction. . At the time of developing the electrostatic latent image on the photosensitive drum 1, the toner in the container of the corresponding developing device is fed to the coating rollers 4a1, 4b1, 4c1, 4d1 by the feeding mechanism, and the developing rollers 4a2, 4b2, 4c2, 4d2 rotating. A thin layer of toner is applied to the outer periphery of the toner, and an electric charge is applied to the toner (friction charging). By applying a developing bias between the developing roller and the photosensitive drum 1 on which the electrostatic latent image is formed, toner is attached to the electrostatic latent image and developed as a toner image.
[0021]
The cleaning device 6 removes the so-called transfer residual toner remaining on the surface of the photosensitive drum 1 without being transferred after the toner developed on the photosensitive drum 1 by the developing device 4 is transferred to the transfer material S. .
[0022]
An electrostatic conveyance belt 11 is disposed as a belt member that circulates and moves so as to face and contact all the photosensitive drums 1a, 1b, 1c, and 1d. The electrostatic transport belt 11 is made of a film-like member having a volume resistivity of 10 ¹² Ω · cm or less and a thickness of about 150 μm.
[0023]
Here, the volume resistivity is a value obtained by applying 100 V with a high resistance meter R8340 manufactured by ADVANTEST using a measurement probe based on JIS method K6911.
[0024]
The electrostatic transport belt 11 is supported by rollers in four directions in the vertical direction, and circulates and moves so that the transfer material is electrostatically attracted to the outer peripheral surface on the upper side in the drawing to bring the transfer material into contact with the photosensitive drum 1. Further, the suction roller 8 abuts on the upstream side (right side in FIG. 1) of the electrostatic conveyance belt 11 in the transfer material conveyance direction. When transporting the transfer material, a bias voltage is applied to the attracting roller 8 to form an electric field with the grounded roller 14a, thereby generating dielectric polarization between the electrostatic transport belt 11 and the transfer material. Thus, an electrostatic adsorption force can be generated in both. A similar effect can be obtained by applying a bias to the roller 14a and setting the roller 8 to face the roller 14a.
[0025]
As a result, the transfer material is conveyed to the transfer position by the electrostatic conveyance belt 11, and the toner images on the photosensitive drum 1 are sequentially transferred.
[0026]
A transfer roller 12 (12a, 12b, 12c, 12d) serving as a transfer member is brought into contact with the inner side (back side) of the electrostatic conveyance belt 11 and corresponding to the four photosensitive drums 1a, 1b, 1c, 1d. It is installed side by side. These transfer rollers 12 are connected to a power supply for transfer bias (not shown). These transfer rollers 12 face the photosensitive drum 1 and form a transfer portion. A positive charge is applied from the transfer roller 12 to the transfer material via the electrostatic conveyance belt 11, and the negative polarity on the photosensitive drum 1 is transferred to the transfer material in contact with the photosensitive drum 1 by the electric field generated by this charge. The toner image is transferred.
[0027]
The electrostatic conveyance belt 11 according to the present embodiment is a belt having a circumference of about 700 mm and a thickness of 150 μm, and is stretched around four rollers of a driving roller 13, driven rollers 14a and 14b, and a tension roller 15, as shown in FIG. Rotates counterclockwise. As a result, the electrostatic conveyance belt 11 circulates and transfers the toner image on the photosensitive drum while the transfer material S is conveyed from the driven roller 14a side to the driving roller 13 side.
[0028]
The feeding unit 16 feeds the transfer material S to the image forming unit, and a plurality of transfer materials S are stored in the feeding cassette 17. At the time of image formation, the feeding roller 18 (half-moon roller) and the registration roller pair 19 are driven and rotated in accordance with the image forming operation to separate and feed the transfer material S in the feeding cassette 17 one by one. The leading edge comes into contact with the registration roller pair 19 and temporarily stops to form a loop. Then, the rotation of the electrostatic conveyance belt 11 and the image writing position are synchronized, and the registration roller pair 19 refeeds the electrostatic conveyance belt 11. It will be done.
[0029]
The fixing unit 20 fixes a plurality of toner images transferred to the transfer material S. The heating roller 21 is driven and rotated, and a pressure roller 22 is pressed against the transfer roller S to apply heat and pressure to the transfer material S. It consists of.
[0030]
That is, the transfer material S onto which the toner image on the photosensitive drum 1 has been transferred is conveyed by the fixing roller pair when passing through the fixing unit 20, and heat and pressure are applied by the fixing roller pair 21 and 22. As a result, the toner images of a plurality of colors are fixed on the surface of the transfer material S.
[0031]
Further, the yellow, magenta, and cyan process cartridges 7a, 7b, and 7c are moved upward from a state in which the photosensitive drums 1a, 1b, and 1c are in contact with the electrostatic conveyance belt 11 by an elevator mechanism (not shown), and the electrostatic conveyance belt It is configured to be movable to a position away from 11. The lifting mechanism is operated according to the selected recording mode.
[0032]
{Recording mode}
Next, an image forming operation of the image forming apparatus configured as described above will be described. In this embodiment, the image forming mode includes a color recording mode for performing color recording and a monochrome mode for performing monochrome recording of only one color. The monochrome mode includes a first monochrome according to the type of transfer material. The mode and the second monochrome mode can be selected.
[0033]
(Color recording mode)
In the color recording mode, as shown in FIG. 2B, image recording is performed in a state where all the photosensitive drums 1a, 1b, 1c, and 1d are in contact with the electrostatic conveyance belt 11. That is, the transfer material S is separated and fed one by one from the feeding unit 16, abuts against the registration roller pair 19, and temporarily stops to form a loop.
[0034]
The photosensitive drum 1 is rotated clockwise in the drawing in synchronization with the rotation of the electrostatic conveyance belt 11, and the transfer material S waiting on the registration roller pair 19 is transferred to the toner image on the peripheral surface of the uppermost photosensitive drum 1a. Is fed again to the electrostatic conveyance belt 11 so that the recording start position of the transfer material S coincides with the opposite point at the timing when the leading end of the sheet is rotated to the opposite point to the electrostatic conveyance belt 11. The surface of each photosensitive drum 1 is uniformly charged by the charging device 2, and the exposure unit 3 exposes the photosensitive drum peripheral surface in accordance with the image signal to electrostatic latent images on the photosensitive drum peripheral surface. Form. The developing roller 4a2 applies a voltage having the same polarity as the charging polarity of the photosensitive drum 1 so that the yellow toner adheres to the electrostatic latent image on the photosensitive drum 1, thereby applying yellow toner to the electrostatic latent image. Develop with adhesion.
[0035]
By applying a bias to the roller 8, an electric field is formed between the roller 14 a and the grounded roller 14, and dielectric polarization is generated between the electrostatic transport belt 11 and the transfer material S to transfer the transfer material S to the electrostatic transport belt. The transfer material S is conveyed while being electrostatically attracted to 11. Thereafter, electrostatic adsorption due to the electric field of the transfer portion occurs between the electrostatic conveyance belt 11 and the transfer material S, so that the transfer material S is sequentially conveyed along the electrostatic conveyance belt 11 to the next transfer portion. The
[0036]
While being conveyed in this manner, the toner image on each photosensitive drum 1 is sequentially transferred onto the transfer material S in the order of yellow, magenta, cyan, and black by applying voltages from the transfer rollers 12a, 12b, 12c, and 12d. .
[0037]
The transfer material S to which the four color toner images have been transferred is separated from the electrostatic transport belt 11 by the drive roller 13 and reaches the fixing device 20, where the transfer material S is heat-fixed on the toner image and then the discharge roller. It is discharged to the discharge part 25 by the pair 23, 24.
[0038]
Next, a description will be given of a monochrome mode in which monochrome recording is performed (here, an image forming process of one black color is illustrated).
[0039]
(First monochrome mode)
When the transfer material S is a sheet that is easily attracted to the electrostatic transport belt 11 such as plain paper or a thin sheet, the first monochrome mode is selected for recording.
[0040]
In the first monochrome mode, as shown in FIG. 2A, the lifting mechanism operates to raise the yellow, magenta, and cyan process cartridges 7a, 7b, and 7c, and the photosensitive drums 1a, 1b, and 1c are moved. The other photosensitive drums 1 a, 1 b, and 1 c are separated from the electrostatic conveyance belt 11 and become untransferable positions with respect to the electrostatic conveyance belt 11 except for the photosensitive drum 1 d.
[0041]
Thus, the electrostatic conveyance belt 11 maintains the contact state between the driving roller 13 and the driven roller 14a and the photosensitive drum 1d in exactly the same state as in the case of full-color recording.
[0042]
Subsequent feeding of the transfer material S by the feeding roller 18, standby of the transfer material S by the registration roller pair 19, and circulation movement of the electrostatic conveyance belt 11 by the driven roller 14a and the driving roller 13 are the same as in the above-described color recording mode. It is the same.
[0043]
At the same time, the process cartridge 7d is driven, and the other process cartridges 7a, 7b, 7c are stopped. The rotation of the photosensitive drum 1d corresponding to the process cartridge 7d, the application of charge to the photosensitive drum 1d by the charging device 2d, the formation of an electrostatic latent image on the circumferential surface of the photosensitive drum by the scanner unit 3d, and the development device 4d The electrostatic latent image is converted into a toner image in the same manner as in the color recording mode described above.
[0044]
Then, at the timing when the leading edge of the black toner image on the circumferential surface of the photosensitive drum 1d is rotated and conveyed to a point opposite to the electrostatic conveyance belt 11, the recording start position of the transfer material S coincides with the opposite point. Then, the registration roller pair 19 starts rotating to feed the transfer material S to the transfer material carry-in port of the image forming unit.
[0045]
Also in this case, the roller 8 and the driven roller 14 a convey the transfer material S while sandwiching the fed transfer material S together with the electrostatic conveyance belt 11.
[0046]
Subsequently, the transfer material S is transported by the electrostatic transport belt 11, the black toner image is transferred to the transfer material S by the transfer roller 12d, and then the transfer material S is separated from the electrostatic transport belt 11 by the curvature separation and fixed. The thermal fixing of the toner image by the unit 20 and the discharge of the transfer material S to the discharge unit 25 by the discharge roller pairs 23 and 24 are the same as in the color recording mode described above.
[0047]
(Second monochrome mode)
When performing monochrome recording, if the transfer material S cannot obtain a sufficient electrostatic attraction force from the electrostatic transport belt 11 such as an envelope or a thick sheet, the recording is performed in the first monochrome mode described above. There is a possibility that the leading edge of the transfer material or a jam occurs before the transfer material S reaches the photosensitive drum 1d. Therefore, when performing monochrome recording on an envelope or the like, the second monochrome mode is selected for recording.
[0048]
In the second monochrome mode, as in the color recording mode, all the photosensitive drums 1a, 1b, 1c, and 1d are arranged so as to contact the electrostatic transport belt 11 as shown in FIG. Monochrome recording is performed in the state. The transfer material conveyance and the image forming process are the same as those in the color recording mode described above.
[0049]
In the second monochrome mode, the yellow, magenta, and cyan photosensitive drums 1a, 1b, and 1c rotate in contact with the transfer material S that is conveyed without transferring toner. It fulfills the function of a conveying roller. Accordingly, the transfer material S is stably conveyed to the black photosensitive drum 1d without being lifted from the electrostatic conveyance belt 11 or causing a leading deviation, and black monochrome recording is performed by the drum 1d. At this time, a voltage may be applied to the transfer rollers 12a to 12c to prevent displacement of the transfer material.
[0050]
(Select recording mode)
In the present embodiment, which recording mode is selected for recording is determined by a signal from a printer driver as shown in FIG. In the case of color recording, control is performed so that the color recording mode is selected regardless of the type of transfer material. In the case of monochrome recording, the first monochrome mode is selected when the electrostatic conveyance belt 11 is a transfer material that is easily attracted electrostatically, and the second monochrome mode is selected when the transfer material is difficult to be electrostatically attracted. Be controlled. As described above, in this embodiment, the type of transfer material is not detected by the mechanical mechanism of the apparatus, but is determined based on the signal from the printer driver.
[0051]
Here, the transfer material that is difficult to electrostatically adsorb is, for example, a strong transfer material having a basis weight of 150 g / m ² or more, or a transfer material that has a fold such as an envelope and forms an air gap. . For example, the volume resistivity of the transfer material is 10 ⁷ Ω · cm or less. The volume resistivity in this case is an actual measurement value obtained by applying 100 V with a high resistance meter R8340 manufactured by ADVANTEST, using a measurement probe in accordance with JIS method K6911.
[0052]
In addition, the transfer material that is easily attracted electrostatically is a transfer material that is relatively weak with a basis weight of, for example, less than 150 g / m ² , and is a transfer material that is a plain paper without creases and in which an air gap is not easily formed. When this is exemplified by volume resistivity, for example, the volume resistivity of the transfer material shows a value exceeding 10 ⁷ Ω · cm. In this case, the volume resistivity is an actual value obtained by applying 100 V with a high resistance meter R8340 manufactured by ADVANTEST, using a measurement probe in accordance with JIS method K6911.
[0053]
As described above, when monochrome recording is performed, recording is performed in the first monochrome mode or the second monochrome mode according to the type of transfer material, so that jams or the like can be performed regardless of the type of transfer material such as plain paper or envelopes. This makes it possible to perform monochrome recording without causing any problems.
[0054]
In addition, since the attitude of the electrostatic conveyance belt 11 with respect to the transfer unit that performs monochrome recording is always constant, the transfer timing in the transfer unit that records black toner and the voltage of the transfer roller 12d in both full-color recording and monochrome recording. There is no need to change the control or the like, and in any case, processing can be performed by the same control method. In addition, since the transfer material inlet of the image forming unit with respect to the transfer material feeding unit such as the transfer material cassette and the registration roller pair is always constant, the position of the transfer material cassette and the registration roller are used for both full color recording and monochrome recording. The position of the pair does not need to be moved up and down in accordance with the position of the transfer material carry-in entrance as in the prior art, and can be configured with a simple mechanism as a whole. Also. Since the posture of the transfer material S discharged from the image forming unit is always constant, the guide guide conveyed to the fixing device is changed in accordance with the discharge posture of the transfer material in both the case of full color recording and monochrome recording. This also makes it possible to configure a simple mechanism as a whole.
[0055]
[Second Embodiment]
In the first embodiment described above, an example in which the transfer material is conveyed in the horizontal direction has been described. However, the transfer material is also applied to an image forming apparatus in which a component in the conveyance direction of the transfer material by the electrostatic conveyance belt includes a gravity direction component. it can. For example, as shown in FIG. 4, in an image forming apparatus in which a path for transporting the transfer material S by the electrostatic transport belt 11 is formed in the vertical direction, an adsorption force is required by the amount of the transfer material. Even in this case, when the present invention is applied, the transfer material can be stably conveyed regardless of the type of the transfer material, and good color recording or monochrome recording becomes possible.
[0056]
The image forming apparatus shown in FIG. 4 has the same configuration as that of the first embodiment described above except that the transfer material is conveyed in the vertical direction, and the same members are denoted by the same reference numerals.
[0057]
In the above-described embodiment, an example in which four photosensitive drums are provided is shown. However, the number of photosensitive drums is not limited to four, and a plurality of photosensitive drums including at least a photosensitive drum used in a monochrome color mode are included. What is necessary is just to have.
[0058]
【The invention's effect】
Since the present invention is configured as described above, when carrying out monochrome recording by transferring a transfer material that is strong and easily lifts from the transfer material carrier, each image carrier is selected by selecting the second monochrome mode. In this case, the transfer material is conveyed while being held down, so that the transfer material can be stably conveyed without causing a leading position shift, skewing, jamming, etc., and monochrome recording can be performed.
[Brief description of the drawings]
FIG. 1 is a longitudinal cross-sectional explanatory view showing the overall configuration of a four-color full-color laser beam printer that is an embodiment of a color image forming apparatus.
FIG. 2A is an explanatory diagram when recording in the first monochrome mode, and FIG. 2B is an explanatory diagram when in the second monochrome mode or color recording mode.
FIG. 3 is an explanatory diagram of a configuration for determining a recording mode based on a signal from a printer driver.
FIG. 4 is an explanatory diagram of an apparatus in which a transfer material conveyance path is set in a vertical direction.
FIG. 5 is an explanatory diagram of a conventional tandem color image forming apparatus.
FIG. 6 is an explanatory diagram of color recording and monochrome recording according to a conventional example.
[Explanation of symbols]
A ... Color image forming apparatus S ... Transfer material 1 ... Photoconductor drum 2 ... Charging device 3 ... Scanner unit 4 ... Developing device 5 ... Electrostatic transfer device 6 ... Cleaning device 7 ... Process cartridge 8 ... Adsorption roller 9 ... Polygon mirror
10… Imaging lens
11 ... Electrostatic transfer belt
12… Transfer roller
13… Drive roller
14a, 14b ... driven roller
15… Tension roller
16… Feeding department
17… Feed cassette
18… Feeding roller
19… Registration roller pair
20… Fixing part
21… Heating roller
22… Pressure roller
23, 24… discharge roller pair
25… discharge section

Claims (3)

An image carrier for carrying a plurality of color toner images and a transfer material carrier for carrying a transfer material, and carrying the plurality of color toner images on the plurality of image carriers on the transfer material carrier. In an image forming apparatus capable of transferring the image on the transfer material in sequence,
A color recording mode the transfer material conveying in contact with all of said plurality of image bearing members for color printing, and the transfer material conveying contacting only given one of said plurality of image bearing members monochrome A first monochrome mode for performing recording, and a second monochrome mode for performing monochrome recording by bringing a transfer material to be conveyed into contact with all of the plurality of image carriers,
An image forming apparatus , wherein either the first monochrome mode or the second monochrome mode is selected according to a type of transfer material.   The image forming apparatus according to claim 1, wherein the transfer material carrier conveys the transfer material by electrostatic adsorption.   2. The image forming apparatus according to claim 1, wherein the type of transfer material is discriminated by a signal from a printer driver and the first monochrome mode and the second monochrome mode are selected.

Images