JP3321709B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus in which a process of forming a pattern-like electrostatic latent image on an image carrier using, for example, a laser light source and developing it with a color toner is repeated a plurality of times. The present invention relates to an image forming apparatus which forms a color image using color toners of a plurality of colors, so as to faithfully obtain a desired color image even when fixing conditions are changed.

[0002]

2. Description of the Related Art A conventional color image system for obtaining a desired color image by superposing color toners by an electrophotographic system will be described. First, FIG. 1A shows that VS charges are applied to an image carrier E2 for forming a color toner image, and 1
A second charge is applied. Next, only a portion where an image, that is, a character or a line image is to be formed, is exposed with a laser beam or the like as shown in FIG. After the exposure is completed, the charges VS are erased only in the exposed portions, and the charges in the other non-image portions are not erased. Next, FIG.
As shown in (1), the image carrier E2 is moved in the direction of the arrow by the developing device D to perform the first or first color development. By the main development, the toner is erased by the well-type potential charge erasing method by the exposure shown in FIG. 1B, and the first color toner adheres to the erased portion and is developed. Next, as shown in FIG. 1 (d), a second charging is performed on the band electrode E1 including on the developing toner of the first color, and the toner of the first color is separated from the image carrier E2 for the sake of explanation, and the charge amount VS Is shown in the position. Next, FIG.
By performing the second exposure on the first color toner as shown in FIG. 1E, only the exposed portions are erased by the well-type potential charge erasing method as in FIG. 1B. Then, the next second color toner is superimposed on the first color toner on the image carrier 29 shown in FIG. The above is the basic process of forming a color image by superimposing color toners. The above-described toner image formation by superimposition of toner is specifically input by key input means as shown in a display 100 incorporating a computer (hereinafter referred to as CPU) as shown in FIG. Then, a character, a line, a solid image, or the like is stored in the CPU or recorded in the magnetic recording unit and output to the printer control 101. The printer control scans with a video signal, for example, the character A is sequentially output as a dot image, and only the character portion is input to the laser printer 102 as a dot signal. ), (C), (d), (e),
(f), the toner image is formed in this order.

[0003]

In order to obtain a color image by the above-described color toner superimposition method, there are a pulse control method and a laser light intensity control method for exposure. For example, yellow and magenta are used. When creating a red color, it is necessary to delicately adjust the color in the case where yellow is weakened and magenta is weakened, in contrast to the case where yellow is weakened and magenta is weakened, changing the above exposure conditions A desired color image is obtained by adjusting the mixing ratio by superimposing the color toners. In the above-described color image formation, particularly when charging and exposing on the color toner on the first color, exposure for the second color has a disadvantage that the influence of the toner layer of the first color is extremely large and development control of the color toner is difficult.

However, the formation of such a color toner image has the following disadvantages. That is, FIG.
As shown in the figure, the image signal output from the CPU to the printer control 101 includes a dot image signal as a character, a dotted line, and a solid image signal. Next, referring to FIG. 3, the printer control shown in FIG.
An image signal is input to 101 as a pulse-like electric signal as shown in FIG. Assuming that signals are sequentially input from the left side of FIG. 3B, first, a solid image signal is input at intervals of a dot image signal, and the input signal is output from the printer control 101 to the laser printer 102 as a video signal. Is done.

The video signal is converted to a pulse signal as shown in the laser printer 102, an ON signal is generated by outputting a dot image, and a pulse having a constant width is formed. Next, a video signal of a solid image is input to the laser printer 102 at intervals, and the signal is emitted when a pulse signal having a fixed width and a fixed interval is turned on. When this is illustrated by the intensity of light energy as shown in FIG. 3A, a large difference occurs in light intensity between a dot image of, for example, 50% duty and a solid image of 50% duty. That is, since the sum of the energies of the dots adjacent to the solid image is obtained,
The average energy is larger than the energy of the single edge portion, and the difference from the light intensity of Duty 100% is reduced. FIG. 3C shows a charge erasure curve obtained by exposing the image bearing member shown in FIG. 1B to the image carrier shown in FIG.
At 0% and 100% Duty, the value of charge erasure is wide open like VS1. That is, when the duty is 100% with respect to the duty 50%, the value of the charge erasure is increased by VS1.

In such a state, the solid image portion is Dut.
Even if the charge erasure is performed at y50% and Duty100%, the value of the charge erasure is extremely small like VS2 as shown in the figure. After performing the charging and exposure processes as described above and performing the developing process, the developing process when performing the image processes as shown in the order of FIGS. 1 (c), (d), (e), and (f) above. To explain the processing status, first, Duty5
When charge erasure is performed at 0%, as shown in FIG. 3 (c), in the dot image portion and the solid image portion, the charge erasure is small in the dot image portion. When the development is performed by the apparatus D, the amount of toner adhered is extremely small, and a large amount of charge is erased in the solid image portion, so that the toner is sufficiently adhered. Next, as shown in FIG. 4B, charging is performed from above the toner of the first color development, and FIG.
100% duty at the second exposure for the second color development
In general, after the development on the image carrier E2, the charge is performed, and the light energy used for the second exposure as the second color is exposed from the toner. Light energy of 100% Duty is projected on both the solid image and the solid image.
In this case, during the development of the first color, the dot image portion is projected on the image carrier E2 with a large amount of light energy due to a small amount of toner adherence, so that a large amount of electric charge is dropped. There is less energy projection, and thus less charge erasure than the dot portion as shown. As described above, a great difference occurs in the potential attenuation rate between the dot image and the solid image. Here, when the second color toner is developed by the developing device E1, a large amount of toner adheres to the dot portion since the dot portion is largely erased, so that the amount of the second color toner adhered is extremely large compared to the amount of the first color toner. Color adjustment is not possible. However, in the solid image portion, the toner adhesion amounts of the first color and the second color are uniform, and a substantially desired color image can be obtained. For the above reasons, there is a disadvantage that if the dot portion and the solid image portion are fixedly charged and the exposure light intensity is kept the same, a good color tone cannot be obtained.

To describe the change in fixing conditions, in a mono-color or full-color image forming apparatus, a toner image may be transferred to a transparent resin film (usually called an OHP sheet) for an overhead projector. In the case of an OHP sheet, it is necessary to have good transparency, but under the fixing conditions for plain paper, there are many irregular reflections on the surface. Therefore, it is necessary to apply heat more sufficiently to the transfer material than in the case of plain paper to improve the surface properties of the toner layer. This can be realized by, for example, increasing the temperature of the fixing device or decreasing the feeding speed of the transfer material. On the other hand, in the case of plain paper, it is not desirable that the heat and the linear velocity become excessively slow. Therefore, when printing on plain paper and an OHP sheet, it is effective to switch the fixing condition depending on the transfer material. However, if the fixing conditions change, the way in which the dots and lines are crushed changes.
Therefore, for example, the OHP sheet has a disadvantage that the line width and the dot diameter become large. In a color image, hue and saturation may be affected.

That is, a normal fixing temperature (about 180 ° C.) is applied to plain paper for performing general transfer by fixing OHP paper.
), The transparency is poor because the surface smoothness of the OHP paper is insufficient. Therefore, if the linear velocity is reduced to about 1/6, the toner layer is sufficiently dissolved in the OHP paper and the transparency is improved. However, there are disadvantages that the dot portion of the toner image is too thick or the line is thick.

For image formation in which the fixing conditions are changed, for example, it is conceivable to control the changing of the fixing conditions so as to obtain a desired glossy image. In this case, however, the gloss is obtained by simply lowering the fixing conditions by reducing the linear speed. Can be changed, but if you change it, the dots and lines will become thicker. Therefore, in the present invention, when the toner image transferred onto the transfer paper is fixed by using a fixing device, the toner image is fixed by the state of heat welding between the recording paper and the toner image and the fixing speed even when there are a plurality of fixing modes. A first object is to obtain a good toner image without changing the dot diameter and line width of the toner image.

Further, the present invention provides a method for improving the above-mentioned drawbacks, for example, by outputting characters output from a CPU or an image memory.
When performing color recording in which a plurality of color toners are superimposed to form a color image based on image information such as a dot, a line, and a solid image, the second color toner is completely identical to the first color toner. SUMMARY OF THE INVENTION It is a first object of the present invention to solve the problem that a desired color cannot be reproduced due to the inability to adhere. In particular, it was found that the difference in the amount of toner adhesion between the center and the edge of the image area was a problem in color reproduction. After the image information is input to an image forming apparatus such as a printer using a photoconductor, when performing modulation by an image signal of an exposure unit that performs image exposure on the photoconductor, a desired control is performed on the exposure unit by performing desired control. Is reproduced.

The first object can be achieved by utilizing the control means for the exposure means. That is, the correction of the change of the fixed image due to the change of the fixing condition is changed by changing the control by the exposure control means, so that a good image or an image with good color reproducibility is obtained regardless of the change of the fixing condition. In particular, in order to smooth diagonal lines, at least one of the dot position to be exposed and the dot diameter is controlled.However, if fixing conditions are changed, for example, if the line speed is reduced, even if it is intended to make the diagonal lines smooth, It is an object to solve a problem that a smooth oblique line cannot be reproduced due to an excessively large dot diameter.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a method of transferring a toner image formed on an image carrier by performing charging by a charging unit, exposing by an image exposing unit, and developing by a developing unit. In the image forming apparatus in which the toner image is fixed to the transfer material by the fixing unit after the image is transferred to the transfer material, when the fixing condition in the fixing unit is changed, the image is formed in accordance with an image signal in order to smooth oblique lines. The image forming apparatus further includes means for changing the dot size controlled by the exposure means according to the fixing condition.

According to another aspect of the present invention, a toner image formed on an image carrier by performing charging by a charging unit, exposing by an image exposing unit, and developing by a developing unit is transferred to a transfer material. In an image forming apparatus for fixing the toner image to the transfer material by a fixing unit, when the fixing temperature of the fixing unit is increased or the fixing speed is changed to be slow, an image signal is formed to smooth oblique lines. A means for controlling the dot size controlled by the image exposure means in accordance with the image exposure means.

Further, according to the present invention for solving the above-mentioned problems, an image is formed on an image carrier by performing charging by a charging unit, exposure by an image exposing unit, and development by a plurality of developing units having toners of different colors. In an image forming apparatus in which a color toner image is transferred onto a transfer material and then the color toner image is fixed on the transfer material by a fixing unit, when the fixing conditions in the fixing unit are changed, the oblique lines are smoothed. And a means for changing a dot size controlled by the image exposure means in accordance with an image signal in accordance with the fixing condition.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, exposure control for obtaining a desired image quality will be described. The means for charging the entire surface of the image carrier 29 shown in FIG. 6 with the band electrode 40 of the scorotron method is shown in FIG.
Same as (a). Next, as shown in FIGS. 2A and 2B, characters, lines, dotted lines, and the like are output as dots in the video signal output from the printer control 101, and the first color is output as a solid image signal. Means for selecting the dot signal or solid image signal is used, that is, the video signal generated by the printer
02 receives. As shown in FIG. 2B, the laser printer 102 has a means for determining what the fixing mode is, an edge detection circuit 104 which is a dot, and a color recording correction circuit 1.
05, a gamma correction unit 106, an image density adjustment unit 103A, and a recording image signal processing unit 103 each having a color tone adjustment unit 103B, and a mechanical control control unit 107 and a laser drive unit 108 are further provided. In the example shown in FIG. 2A from the video signal with the above configuration, when the character A is output as a dot image, the edge detection circuit unit 104 detects an edge portion. In this edge portion detection, a matrix of 3 × 3 pixels is scanned to determine whether the edge portion or the non-edge portion is one pixel at a time. Further, the color recording correction circuit unit 10
In 5, the color recording image is corrected and the gamma correction is performed in the gamma correction unit 106, input / output control is performed with the mechanical control control unit 107, and also between the mechanical control control unit 107 and the laser driving unit 108. I / O control is being performed. A signal for discriminating the edge portion or the non-edge portion for each pixel is sent to the laser driving portion 108.

First, when the plain paper fixing mode is selected, when there is no superposition, the solid portion is set to 80%, and the edge or isolated dot is set to 100%. As a result, blurring of isolated dots and one-dot-width lines can be prevented.

At the time of superposition, the first color: a solid portion is 50% and an isolated dot or edge is 60%
Then, as shown in FIG. 5A, the potential becomes the same in the solid and dot portions. When this is developed by the developing device 30, the toner adhesion amount is not changed between solid, dot, and line as shown in FIG. 5C.

Second color: Duty is increased because toner becomes difficult to adhere due to the influence of the first color toner. In this case, the solid color, the edge, and the isolated dot may be changed. However, if the Duty of the first color is adjusted as described above, since the thickness of the developed toner is the same in both the dot portion and the solid image portion, the charge is erased. 5F, the thickness of the toner finally developed using the developing device 31 for the second color becomes uniform and the color tone becomes uniform, as shown in FIG. 5F. When the OHP or gloss mode is selected, the entire image is crushed. Therefore, the duty is set smaller than that in the plain paper fixing mode.

When there is no superposition, the solids may be 80%, but the edges or isolated dots are set to 50% to prevent the dots and lines from being crushed. The conditions of the superimposed solid are the same as those in the plain paper fixing mode. In the case of the edge or the isolated dot, the first color is set to 40% and the second color is set to 60% to prevent the dots and lines from being broken.

Next, the configuration of a printer using the process of the image forming apparatus will be described. In FIG. 6, reference numeral 1 denotes a lower frame of the image forming apparatus, in which a half-moon-shaped paper feed roller 2 for feeding recording paper P, which is a transfer body, is provided. A built-in paper feed cassette 3 is detachably provided on the lower frame 1. A push-up plate 4 that is pushed up by a spring 5 is provided in the paper feed cassette 3. The recording paper P is placed on the push-up plate 4, and a separation claw 6 rotatably provided on a part of the paper feed cassette 3 is recorded. The paper P is locked at the top of the tip. Reference numeral 7 denotes a guide plate for guiding both sides of the recording paper P, which is provided so as to be adjustable depending on the size of the recording paper.
The above configuration is provided in the paper feed cassette 3. Reference numeral 8 denotes a transport roller for the recording paper P provided on the lower frame 1 and is provided between a guide plate 9 for guiding the leading end of the recording paper P fed by the paper feed roller 2 and a reverse guide plate 10. .

Reference numeral 11 denotes a guide plate for guiding the recording paper P to a registration roller 12 after the recording paper P is reversely fed, and guides the recording paper P to the registration roller 12. 13 is the registration roller 12
The sensor S1 for detecting the recording paper P at the position
A swing member that turns N and OFF. 14 is a registration roller 12
A guide plate that guides the recording paper P that has passed through the transfer belt 15 toward the transfer belt 15.
17 and a drive roller 18. Reference numeral 15a denotes cleaning means for cleaning the surface of the transfer belt 15. Reference numeral 19 denotes a fixing device for fixing the image transferred onto the recording paper P, which comprises a fixing heating roller 21 and a pressure roller 20, and a cleaning roller 20a is pressed against the fixing heating roller 20, and the cleaning is performed according to the rotation. I do. 22 is the fixing device 19
A swinging roller 2 for turning on and off a sensor S2 to check the discharge of the recording paper P by a discharge roller for discharging the recording paper P more.
3 is operated by recording paper at the time of paper ejection. The discharged recording paper P is transferred to the upper frame 1 by a recording paper guide member 24, a guide passage 25 formed in the upper frame 1c, and guide conveyance rollers 26 and 27.
The recording paper P is configured to be discharged to a paper discharge tray 28 provided on substantially the entire upper part c. Next, an image carrier 29 (hereinafter referred to as a photosensitive drum) for forming an image is provided substantially at the center of the upper frame 1c.
There is a developing device frame 30a in which four sets of developing devices 30, 31, 32, and 33 can be respectively disposed from above along the surface of the photosensitive drum 29. 34 is a polygon mirror which reflects the laser light emitted from the laser light source 35 to the reflection mirror 3
The light is reflected at 6, 37 and 38, and the photosensitive drum 29 is exposed. Three
Reference numeral 9 denotes an optical system frame in which optical systems such as the polygon mirror 34 and the reflection mirrors 36, 37, and 38 are integrally incorporated. The optical system frame 9 is incorporated in the uppermost portion of the upper frame 1c.

Reference numeral 40 denotes a band electrode for charging the entire surface of the photosensitive drum 29, which is provided on a part of the upper frame 1c. 41
Is a cleaning blade for transferring the image from the photosensitive drum 29 to the recording paper P and then cleaning the residual developer adhering to the surface of the photosensitive drum 29. A device 43 for transporting the developer scraped by the cleaning blade;
A developer receiving member 42 that efficiently sends the developer 43 is provided below the cleaning blade 41. The developer conveyed to the outside by the conveying device 43 is conveyed to the container 44 by the conveyor 45 so that an appropriate amount of the developer can be accumulated in the container 44, and the developer can be removed and discarded. Reference numeral 46 denotes a developer container for supplying a developer to each of the developing devices 30, 31, 32, and 33. Although only one set of the illustrated developer containers is provided, four sets are provided side by side. For example, cyan, magenta, yellow, and black color developers are supplied to 30, 31, 32, and 33 to perform color development. Reference numeral 47 denotes a manual feed stand that can manually supply the recording paper P. The lower frame 1 and the upper frame 1c are assembled so that the conveyance path of the recording paper P can be opened around the support shaft 1b. Is not reached at least to the fixing device 19, the upper frame 1c is opened around the support shaft 1b, and the recording paper P can be taken out. Further, a guide plate 1a is provided to enable the recording paper P provided on the lower frame 1 to be supplied from another paper feeding device (not shown).

The photosensitive drum 29 is provided on a frame 41a on which a cleaning blade 41 is provided via a support shaft 29a, and the support shaft 29a is supported by the upper frame 1c.

Reference numeral 48 denotes an opening / closing lid provided above the developer container 46 and constituting a part of the upper frame 1c. A part of the opening / closing lid 48 is flush with the surface of the paper discharge tray. A double discharge tray surface 48a is formed, and a recording paper blocking portion 49 for preventing the recording paper P from dropping is provided integrally with the opening / closing lid 48 so as to protrude from the double discharge tray surface 48a. And the opening / closing lid 48 is a spindle
At 50, it is pivotally attached to the upper frame 1c.

Using the above-described image forming apparatus, the photosensitive drum 29 emits light in accordance with an image signal from a laser light source 35 through an output means from a CPU as shown in FIG.
The surface of the photoreceptor drum 29 which has been primary charged is exposed. In this exposure, the primary exposure shown in FIG. 1B is performed as described above.

Next, the developing device 30 develops a yellow color toner as the first color, and as shown in FIG.
And the laser light source 35 as shown in FIG.
After the second exposure, the developing device 31 superimposes and develops the magenta color toner.

Thereafter, similarly, a cyan color toner as the third color and a black toner as the fourth color are successively superposed and charged and exposed to develop, thereby forming a color toner image of four colors on the surface of the photosensitive drum 29.

As described above, charging, exposure, and development are sequentially performed on the surface of the rotating photosensitive drum 29, color toner is superimposed, and a toner image formed into an accurate color image by exposure control is transferred to the recording paper P. The toner image is transferred on the belt 15 and fixed on the recording paper by the fixing device 19.

FIG. 7 shows an embodiment utilizing another color image forming process of the present invention. In the present embodiment, a band electrode 2021, an exposure unit 203, and a developing unit 204 are provided on a photosensitive drum 29 serving as an image carrier.
A first image forming unit, a band electrode 205, an exposing unit 206, and a developing unit 207 as a set.
A third set of the band electrode 208, the exposure unit 209, and the developing unit 210;
Of the first image forming unit, a yellow color toner is supplied to the developing unit 204, a magenta color toner is supplied to the developing unit 207, and a cyan color toner is supplied to the developing unit 210. After a charge is applied to the photosensitive drum 29 by the band electrode 202, light control by Duty is performed by the exposure unit 203 in the same manner as in the image forming process, and then the yellow developing unit 204 develops the yellow color toner. In the next stage, the photosensitive drum 29 and the yellow color toner are immediately charged, and the exposure unit 209 performs the charge erasure control by the pulse width control, and the developing unit 207 develops the magenta color toner. Alternatively, the image is superposed and developed using cyan color toner of the third image forming means. This method is a method in which the photosensitive drum 29 can be processed by one-turn image formation. The transfer roller 211 transfers a color image onto the recording paper P,
The color toner transported between the roller 12 and the pressure roller 213 is fixed on the recording paper P.

Next, an embodiment shown in FIG. 8 is an image forming apparatus utilizing the color image forming process of the present invention as described above.
A first image forming unit provided with a band electrode 310, an exposing unit 311 and a developing unit 312 for a photosensitive drum 309 serving as an image carrier, and a band electrode 306, an exposing unit 307 and a developing unit 308 for a photosensitive drum 305. A band electrode 302, an exposure unit 303, and a developing unit 304 with respect to a photosensitive drum 301.
And a third image forming unit provided with the first, second, and third image forming units.
A recording paper transport belt 313 is provided in common contact with the photosensitive drums 309, 305, 301 of the third image forming means, and is further provided at a position facing the photosensitive drums 309, 305, 301 via the recording paper transport belt. The transfer poles 314, 315, and 316 are provided, and the developing device 312 is provided with yellow, the developing device 308 is provided with magenta, and the developing unit 304 is provided with cyan color toner.
First, using the color image forming process of the present invention of the present apparatus, the duty
Developing device 312 by exposing to exposure means 311 which performed light control by
After the development, the recording paper P is conveyed by the recording paper conveyance belt 313 to transfer the yellow image to the transfer pole 314 at the end of the development. To the recording paper P
Exposure with light control by Duty is performed to superimpose on the recording paper P, and then magenta color toner is developed by the developing device 308 to form the magenta color toner formed on the photosensitive drum on the recording paper P. The image is transferred at the transfer pole 315 so as to overlap the yellow color toner. As described above, both the color toners of FIGS. 7 and 8 use the image forming process of the present invention and are configured to transfer the amount of color toner by two-color superposition uniformly. In the above embodiment, only the three primary color toners have been illustrated, but a developing device using a black toner may be added.

Although not shown in the present embodiment, a system in which three or four color toner images are formed on the photosensitive drum, and then the color image is transferred to recording paper via a transfer drum or belt. May be used.

Next, a description will be given of an embodiment which achieves the above object by using an image forming apparatus having the above-mentioned exposure control means. FIG. 9 shows a control system for performing image control when implementing the present invention of the image forming apparatus shown in FIG. Parts common to those in FIG. 6 are described with the same reference numerals. In this embodiment, the feeding of the recording paper P from the paper feed cassette 3 is started by the rotation of the paper feed roller 2 according to the paper feed signal from the CPU. The fed recording paper P is guided and conveyed by a guide plate 9 by conveyance rollers 8, and the sensor S3 of the recording paper P detects whether the recording paper P is plain paper or OHP paper.
Here, whether the sensor S3 is plain paper or OHP paper is detected, and when a signal is sent to the CPU, the voltage of the grid pole 40A provided on the band electrode 40 is adjusted by the signal from the CPU by the voltage adjusting device 40B. For example, the grid voltage is adjusted to -730 V for plain paper and -800 V for OHP paper, and an electric charge is applied to the surface of the photosensitive drum 29 rotated by the band electrode 40. Next, information on whether the paper is plain paper or OHP paper is CP
2A, and as shown in FIGS. 2A and 2B, the printer controller 101 detects edges in the recording image signal processing unit 103 in the laser printer 102, performs color recording correction,
After the image density adjustment, the color tone adjustment, the gamma correction, and the like are performed, the charged surface of the photosensitive drum 29 is exposed by the laser light source 35 from the laser driving unit 108. In the case of a full color image, there is a portion that overlaps with toner of two or more colors in the image.

[0033]

[Table 1]

Table 1 shows the duty ratio of the pulse width of the laser modulation signal at the time of image formation.
Indicates Duty% for paper. Isolated dots for single color without toner superposition. Plain paper Du for edges only.
OHP paper has a duty of 50% compared to ty100% (one dot corresponds to the amount of image exposure for attaching toner to one pixel).
Drop. Also, in the case of superimposition, the duty ratio is changed by judging the edge in the case of a superimposed portion and a portion of a single color. It may be changed in the case of superposition and a solid image, and in the case of plain paper and OHP paper. In the case of an isolated dot and an edge so that the line width and the dot diameter do not change depending on the fixing mode, 1 is set when plain paper is input.
If OHP paper is input with Duty 60% for Duty and Duty 100% for Second Color, Duty 40% for First Color and Duty 60% for Second Color will be reduced by 10% to 70% respectively. And Duty for the first and second colors
The ratio can be input from the operation panel so as to have a preferable value depending on the color tone. The switching of the fixing speed shown in Table 1 will be described later.

[0035]

[Table 2]

Table 2 shows the duty ratio of the pulse width of the laser modulation signal at the time of forming a monocolor image. The duty ratio is 100% for a plain image and 100% for a solid image in OHP paper. O only for isolated dots and edges
HP paper is exposed at a Duty of 50%. In Table 2, switching of the fixing speed will be described later.

As described above, the exposure is performed by controlling the duty ratio of the plain paper and the OHP paper detected by the sensor S3. Next, development is sequentially performed by the developing devices 30, 31, 32, and 33. As shown in FIG. 13, a bias power supply 300 is connected to the developing device 30, and a drive control power supply 301 is connected to the developing sleeve rotating motor M1. . A bias power supply 310 is connected to the developing device 31, and a drive control power supply 311 is connected to the developing sleeve rotating motor M2. A bias power supply 320 is connected to the developing device 32, and a drive control power supply 321 is connected to the developing sleeve rotating motor M3. A bias power supply 330 is connected to the developing device 33, and a drive control power supply 331 is connected to the developing sleeve rotating motor M4.

When the development is performed using the four developing devices constructed as described above, in the case of the monochrome development, the latent images on the surface of the photosensitive drum 29, each of which has been exposed and adjusted at the duty ratio shown in Table 1 above, are used. The developing is performed by using any one of the developing devices 30, 31, 32, and 33. The bias voltage is supplied to each image by a bias power supply 300, 310, 320, or 330 provided in each of the developing devices. And the developing sleeve rotating motors M1, M2, M3, M4 are controlled by the drive power sources 301, 311, 32.
CPUs 1 and 331 are adjusted according to each image and rotated.

Next, when a full-color image is developed, the latent images on the surface of the photosensitive drum 29 whose exposure has been adjusted at the duty ratio shown in Table 1 are sequentially developed by the developing devices 30, 31, 32, and 33. In the embodiment, the line width dot diameter is controlled by the exposure condition. Next, an example in which the line width dot diameter is controlled by the developing bias will be described.

[0040]

[Table 3]

As shown in Table 3, when developing the yellow color using the developing device 30, the peak to peak of the AC bias voltage is set to 2.4K for the plain paper from the bias power supply 300.
V and OHP paper is developed at 2.0 KV. Below magenta,
When color images are formed by the cyan and black developing devices 31, 32, and 33, the AC bias voltage is set to 2.4 for all plain papers.
KV, and OHP paper is set at 2.0 KV. Therefore, the OHP paper has an AC bias voltage of 10% to 50% lower than that of plain paper, and the higher the AC bias, the more the development is promoted. At this time, however, edges such as lines and dots are particularly emphasized and tend to be thick. . Accordingly, in the OHP paper mode, the AC bias is lowered so that the line width and the dot diameter are the same as those in the plain paper mode.

According to the method described above, the recording paper P is made of plain paper or O.
After selecting HP paper and controlling exposure and development,
The image formed on the photosensitive drum 29 is transferred onto the recording paper P by the transfer belt 15. In addition, uniform control of the image quality is also effective in actual cases in which variable control of the pulse width of the laser modulation signal and variable control of the developing bias are used to cope with changes in the fixing conditions.

The fixing speed of the recording paper P on which a monochrome or color image has been transferred is changed depending on whether it is plain paper or OHP paper. The motor 2004 shown in FIG. 9 is a heating roller for fixing.
The transfer belt 15 may be simultaneously driven as shown in FIG. A heat source 20A is provided in the fixing heating roller 21 as shown in FIG.

To fix the image transferred to the recording paper P,
The recording paper P is caused to enter the fixing heating roller 21 and the pressure roller 20 to be thermally fixed. At this time, when the recording paper P is plain paper, the fixing speed of the monochrome or color image is conveyed at a fixing speed of 74 mm / s as shown in Tables 1 and 2, and in the case of OHP paper, the fixing speed is 12 mm / s. By conveying at a fixing speed, fixing can be performed with the highest image quality.

A heating roller for fixing provided in the fixing device 19 will be described below.
An embodiment of a fixing device for fixing a toner image on recording paper P so as to be clearer by changing the heat amount of 21 or the pressure contact force of the pressure roller 20 and the fixing speed will be described.

The fixing device 19A shown in the embodiment of FIG.
The description will be made using the same reference numerals as those of the fixing device 19 shown in FIG. Fixing device 19
A includes a heating roller 21 for fixing and a pressure roller 20. A heating heat source 20A is provided in the heating roller 21 for fixing.

As described above, the voltage is adjusted by the voltage adjusting unit 191 which adjusts the voltage from the power supply 192 for the heating heat source 20A by the recording image signal processing unit 103 which receives the image signal from the printer controller 101 shown in FIG. The voltage is adjusted by the voltage adjusting unit 191 to apply the voltage to the heat source 20A. Now, an image signal based on a video signal is received from the printer controller 101, and the photosensitive drum 29 is
It is charged by the band electrode 40 and performs exposure and development based on the image signal. At this time, as described above, the character A shown in FIG. 2A, that is, image information is output, and the laser light source 35 controlled by the recording image signal processing unit 103 in the laser printer 102.
Generates an ON signal.

After the adjusted exposure of the photosensitive drum 29, the developing device 30 and other development are completed, the toner image is transferred to the transfer paper P, and when the recording paper P enters the fixing device 19A, for example, heating is performed. The temperature is set to 180 degrees, the toner image is controlled in accordance with the set temperature, is thermally fixed by the fixing heating roller 21, and is discharged by the discharge roller 22.

As a pressure adjusting method, a fixing device 19 shown in FIG.
B includes a heating roller 21 for fixing and a pressure roller 20. A heat source 20B for heating is provided in the heating roller 21 for fixing. On the other hand, the shaft 20C of the pressure roller 20 has a bearing 20
D is provided, and an intermediate member 20G is provided in contact with the bearing 20D via a lever 20F to adjust the pressing force of the pressure roller 20 by the rotation of the cam 20E.

The cam 20E has a drive motor with a speed reducer.
An output means 201 is provided for controlling the rotation of the drive motor 20H in conjunction with 20H. 202 is a power supply for the driving motor 20H. In this embodiment, an image signal based on a video signal is now received from the printer controller 101, the photosensitive drum 25 is charged by the band electrode 40 as described above, and exposure and development based on the image signal are performed. At this time, as described above, FIG.
A, ie, image information, is output, an ON signal of the laser light source 35 controlled by the recording image signal processing unit 103 in the laser printer 102 is generated, and synchronized with the image control signal controlled as described above. Then, the current of the power supply 202 is turned on and off by the output means 201 to drive the drive motor 20H. The driving causes the cam 20E to rotate, press the intermediate member 20G via the lever 20F, and press the bearing 20D provided on the shaft 20C of the pressure roller 20. Meanwhile, the photosensitive drum 29
On the other hand, when the developing device 30 and other development are completed after the adjusted laser light exposure, the toner image is transferred to the transfer paper P, and the recording paper P enters the fixing device 19B according to the pressure. An image is formed, and the fixing heating roller 21 is kept in a pressed state between the pressure roller 20 by the cam 20E. The output means 201 is controlled so that the pressing force is maintained until the rear end of the recording paper P passes the sensor S2. The recording paper P on which the heat fixing has been completed is discharged by a discharge roller 22.

Next, the fixing device 19C shown in FIG. 12 will be described. The fixing device of FIG. 12 is also described with the same reference numerals as in FIG. The fixing device 19C includes a heating roller 21 for fixing and a pressure roller.
The fixing heat roller 21 has a heat source for heating.
200 are provided.

A driving gear is provided on the shaft 2001 of the pressure roller 20.
An intermediate gear 2003 is provided on the driving gear 2002, and a motor 2004 for driving the intermediate gear 2003 is provided coaxially or via another reduction means. The motor 2004
It is appropriate to use a servomotor whose rotation speed can be freely changed.

Reference numeral 2005 denotes control means for controlling the rotation of the motor 2004.
The rotation is controlled by the information. In the present embodiment, an image signal based on a video signal is now received from the printer controller 101, and as described above, the photosensitive drum
29 is charged by the band electrode 40, and exposure and development based on the image signal are performed. At this time, as described above, the character A shown in FIG.
O of laser light source 35 by recorded image signal processing unit 103 in 102
An N signal is generated, and the control means 2005 controls the current of the power supply 2006 to control the rotation of the motor 2004 in synchronization with the control signal controlled as described above. On the other hand, when the developing device 30 and other development are completed after the adjusted laser beam is exposed to the photosensitive drum 29, the toner image is transferred to the transfer paper P, and the recording paper P enters the fixing device 19C. For example 74mm
The motor 2004 is controlled at / sec, and an image is formed so as to be suitable for the controlled speed, so that the fixing heating roller 21 is rotated at a speed suitable for the transferred image and is thermally fixed.

FIG. 13 is a diagram showing the internal configuration of the developing device 30.
Denotes a developing device frame. A developing sleeve 302 is rotatably provided in the developing device frame 301 at a position facing the photosensitive drum 29, and N and S are magnetized in the developing sleeve 302. The magnet 303 is fixed and provided. Reference numerals 304 and 305 denote developer 3 composed of carrier and toner provided in the developing device frame 301.
The developer 306 that has been agitated by the agitating member 06 regulates the developer 306 conveyed by the developing sleeve 302 to a constant layer thickness and amount by the conveyance regulating member 307. A bias power generator 308 is connected to the developing sleeve 302 via a bias voltage adjuster 309. The bias voltage adjuster 309 is connected to the printer controller 101 via the laser printer 102. In the present embodiment, as described above, when the pressure contact force between the fixing heating roller 21 and the pressure roller 20 or the fixing speed or the heating temperature is changed, the changed value is changed to the printer controller 101.
To the bias voltage regulator 30 according to the changed value.
At 9, only the bias voltage is adjusted and applied to the developing sleeve 302, and development is performed with a bias voltage suitable for the value obtained by changing the fixing device 19.

As described above, as a method of transferring a color or monochrome image to the recording paper P and fixing it effectively, a method of controlling a heat source for fixing, a method of adjusting a pressing force of a pressure roller 20 and a method of fixing a heat roller 21 are described. The three methods of adjusting the rotation speed have been described with reference to the respective embodiments. However, one of the three methods most suitable for the image according to the image is combined without using the three methods individually. Combine methods and 3 more
Of course, it is also possible to use the methods simultaneously.

As described above, the present invention changes the conditions of the toner image forming process in accordance with the change of the fixing conditions. In other words, non-edge portions or solid images are formed as the latent image forming conditions formed on the photosensitive drum 29, and the charging potential and the exposure condition, or light intensity modulation is performed only as the charging potential or the exposure condition, based on the image information of the isolated dot and the edge portion. Means for changing charging and exposure conditions in consideration of conditions such as the presence or absence of superposition of color toner, and changing the bias voltage including, for example, a DC component or an AC component in a developing bias as a developing condition, or a sleeve. Control of the amount of toner adhering to the electrostatic latent image on the photosensitive drum 29 as a method of changing the developer conveyance speed, or the distance between the surface of the photosensitive drum 29 and the sleeve surface of the developing device and the DSD interval immediately. Then, after transferring the toner onto the recording paper P, as a means for fixing the toner on the recording paper P, the temperature of the heat fixing roller is controlled or A method using a means for changing the linear velocity of the formation roller or a method using a combination thereof, and a means for changing the pressure between the heat fixing roller and the pressure roller are used alone or in combination with the image information to form a good image. To get.

In the above-described embodiment, the change of the exposure condition in accordance with the change of the fixing condition was performed by changing the duty ratio. Changing the exposure conditions is the same as changing the duty ratio.
It can also be performed by changing the dot position and dot size by M modulation (pulse exposure width modulation).

FIG. 14 is similar to FIG.
1 shows a circuit for scanning and exposing an image signal input from 1 to a laser printer 405. In the figure, an image signal is input to the laser printer 405 as a video signal via the print controller 403. At this time, dot position and dot size control data determined in consideration of fixing conditions are also input at the same time.

In the laser printer 405, based on the input dot position and dot size control data, a PWM
A desired toner dot is formed by controlling the laser driver by the control.

FIG. 15 shows an example in which oblique lines are printed by the PWM control. By controlling the dot position and the dot size by performing PWM control by the exposure control circuit of FIG. 14 with respect to the conventional dot forming method of FIG.
As shown in FIG. 5, a method of printing oblique lines smoothly by PWM control is shown.

The position of the dot is changed in at least one of the main scanning direction and the sub-scanning direction, the dot diameter is changed, or both are performed so that the outer phosphorus line of the dot does not step up.

Also in this case, if the fixing conditions change, the appropriate conditions for the dot position and the diameter to be smoothed change, so that these are changed in conjunction with the fixing conditions. In the example,
In the case of OHP fixing or gloss fixing, the dot diameter is
Good results have been obtained with 30 to 60%.

By changing the dot position and the dot size according to the change of the fixing condition by the PWM control, the fluctuation of the line width and the dot diameter can be corrected.

[0064]

According to the present invention, the exposure dot diameter for smoothing oblique lines is configured to be changed in accordance with the fixing condition in accordance with the change of the fixing condition, so that even if the fixing condition is changed, Exposure control according to this can be performed, and an excellent effect that slant lines can be smoothly reproduced can be obtained.

[Brief description of the drawings]

1 (a) to 1 (f) show conventional charging, exposure, control, development,
FIG. 3 is a process diagram of an image forming unit showing a two-time development method.

FIGS. 2A and 2B are explanatory diagrams of an arrangement of an image forming apparatus showing up to a laser printer by UPU input;

FIGS. 3A to 3C are explanatory diagrams of exposure control in image dots and solid images.

FIG. 4 is an explanatory diagram showing the development of a color toner in a conventional dot and solid image.

FIGS. 5A to 5F are explanatory diagrams showing the development of a color toner in a dot and solid image of the present invention.

FIG. 6 is a longitudinal sectional view of an image forming apparatus using the image forming unit of the present invention.

FIG. 7 is an image forming apparatus showing another embodiment using the image forming means of the present invention.

FIG. 8 is an image forming apparatus showing another embodiment using the image forming apparatus of the present invention.

FIG. 9 is a block diagram showing the overall control means of the present invention.

FIG. 10 is a front view showing another fixing device of the present invention.

FIG. 11 is a front view showing another fixing device of the present invention.

FIG. 12 is a front view showing another fixing device of the present invention.

FIG. 13 is a longitudinal sectional view showing an image format by bias control of the developing device of the present invention.

FIG. 14 is a block diagram illustrating a signal processing circuit that performs PWM exposure control according to the present invention.

FIG. 15 is a diagram showing a dot image when oblique lines are formed by a conventional technique.

FIG. 16 is a diagram showing a dot image when oblique lines are formed by the PWM exposure control of the present invention.

[Explanation of symbols]

 Reference Signs List 1 lower frame 1c upper frame 2 paper feed roller 3 paper feed cassette 7, 9, 10, 11, 14 guide plate 12 registration roller 15 transfer belt 19, 19A, 19B, 19C fixing device 20 pressure roller 20A, 20B heat source 20a Cleaning roller 21 Heating roller for fixing 28 Discharge tray 29 Photoconductor drum (image carrier) 30, 31, 32, 33 Developing device 30a Developing device frame 34 Polygon mirror 35 Laser light source 36, 37, 38 Reflecting mirror 103 Recorded image Signal processing section 191 Voltage adjustment section 192, 202, 2006 Power supply 201 Output means 2005 Control means

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI H04N 1/29 B41J 3/00 M 1/409 H04N 1/40 101D (72) Inventor Makoto Takeda 2970 Ishikawacho, Hachioji-shi, Tokyo Examiner in Konica Corporation Teruaki Shimomura (56) References JP-A-4-160869 (JP, A) JP-A-4-37887 (JP, A) JP-A-4-192759 (JP, A) 2-193165 (JP, A) JP-A-4-98269 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/00 303 G03G 21/00 370-540 B41J 2 / 44 G03G 15/01-15/01 117 G03G 15/04-15/04 120 H04N 1/29-1/31 H04N 1/40-1/409

Claims (3)

(57) [Claims] An image forming apparatus according to claim 1, wherein the toner image formed on the image bearing member is transferred to a transfer material by performing charging by a charging unit, exposure by an image exposing unit, and development by a developing unit, and then transferring the toner image by a fixing unit. In the image forming apparatus for fixing to a material, when a fixing condition in the fixing unit is changed, a dot size controlled by the image exposing unit in accordance with an image signal to smooth oblique lines according to the fixing condition. An image forming apparatus, comprising: a changing unit. 2. A toner image formed on an image carrier by performing charging by a charging unit, exposing by an image exposing unit, and developing by a developing unit, is transferred to a transfer material, and then the toner image is transferred by a fixing unit. In an image forming apparatus for fixing to a material, when the fixing temperature of the fixing unit is increased or the fixing speed is changed to be slow, the image exposure unit controls the image exposure unit in accordance with an image signal to smooth oblique lines. An image forming apparatus comprising means for controlling a dot size to be reduced. 3. A color toner image formed on an image carrier by charging by a charging unit, exposing by an image exposing unit, and developing by a plurality of developing units having toners of different colors is transferred to a transfer material. Then, in an image forming apparatus for fixing the color toner image to the transfer material by a fixing unit, when the fixing condition in the fixing unit is changed, the image exposure is performed in accordance with an image signal in order to smooth oblique lines. An image forming apparatus comprising: means for changing a dot size controlled by the means in accordance with the fixing condition.