JPH0990809A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of exerting optimum fixing-temperature-control according to an output image which is printed. SOLUTION: Data on Y(yellow), M(magenta), C(cyan), and K(black), converted in a signal processing part 101, is once written in a FiFo memory 106, and before an output goes a laser driver 111, the presence of half tone density, that is, the presence of an image is judged for each line by means of a density detection part 108. Also, the data length of each lines is judged under address control exerted at the time of writing and reading into/from the FiFo memory 106 by means of an address counter 107. Further, the type of a recording medium and whether the image has one color or a plurality of colors are judged by a paper/color detector 110. The result of the judgment about them is outputted to a selector 109 by means of Flags. In the selector 109, in order to reflect the contents of each Flag, for example in the case of the presence of the image, an output is applied to a heater control part so as to increase a fixing temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic type or electrostatic recording type image forming apparatus,
For example, the present invention relates to an image forming apparatus capable of fixing control when fixing a toner on a sheet for outputting a formed image via a transfer drum.

[0002]

2. Description of the Related Art FIG. 1 shows an example of a conventional image forming apparatus.
1 and 12 show the configuration of a laser beam printer.

This laser beam printer is a terminal device which is connected to a computer via a predetermined interface cable and outputs the result of information processed by the computer onto a recording sheet which is a recording medium.

In FIG. 11, reference numeral 1101 denotes a signal processing unit. When image information is input to the signal processing unit 1101 as R, G, and B input signals, the corresponding yellow (Y) and magenta (M). ), Cyan (C), and black (K) density image signals. The Y, M, C, K image data output from the signal processing unit 1101 is sent to the laser driver 1102, and the laser driver 1102 modulates the input Y, M, C, K image information. Then, the modulation signal for each color is sent to the amplifier 1103 to drive the semiconductor laser 1104 which is the exposure means.

First, a laser emitted from a semiconductor laser 1104 based on yellow (Y) image information scans a photosensitive drum 1108 which is an image carrier through a polygon mirror 1105, an f-θ lens 1106 and a reflection mirror 1107. Then, an electrostatic latent image corresponding to yellow (Y) image information is formed on the photosensitive drum 1108.

This electrostatic latent image is developed by a developing device 1109 which faces the photosensitive drum 1108 as shown in FIG.
Among them, it is developed by the developing device 1109a containing the yellow toner, and further transferred onto the recording paper by the transfer drum 1110.

Next, by the same process, an electrostatic latent image corresponding to image information of magenta (M), cyan (C), and black (K) is developed by the developing device 11 containing toner of each color.
09b to 1109d, the transfer drum 111
0 is transferred onto the recording paper, and toner of each color is laminated on the recording paper.

After that, the recording paper is conveyed to the fixing device 1111. The fixing device 1111 heats and presses the stacked toners to fix the image on the recording paper, and the recording paper is printed by the printer. It is discharged to the outside.

Therefore, in order to obtain a good output image in such a laser beam printer, it is necessary to properly fix the toner image on the recording paper. However, this laser beam printer has a full-color image as described above. In addition, since a mono-color image can be formed, the number of toner layers transferred on the recording paper is different between the full-color mode and the mono-color mode, so that the temperature required for fixing changes.

Further, since the recording papers having various thicknesses are used and not only the recording paper but also the OHT can be used, the temperature required for fixing varies depending on the kind of the recording medium. Become.

Therefore, in the conventional laser beam printer, a control for changing the fixing temperature according to the type of recording medium and the color mode is performed to always obtain a good image.

[0012]

However, in the above-mentioned conventional example, although the control for adjusting the fixing temperature according to the type of recording medium and the color mode is performed, it is performed for each fixing step for one recording medium. Since the fixing temperature has been determined, for example, even for an image in which the print portion is only on the leading edge of the recording paper, heat the non-printed portion that occupies most of the recording paper at the temperature required for fixing the printed portion. In some cases, it can be said that the power is wasted.

This is also the case when an image image and a normal character image are mixed, and even if the character image portion has a larger area, the character image is fixed in order to secure the fixing property of the image. The entire fixing was carried out at a temperature higher than that required for.

Therefore, it is an object of the present invention to provide an image forming apparatus capable of performing more optimized fixing temperature control according to an output image to be printed.

[0015]

According to the first invention of the present application, the above object is to provide an image carrier having a photosensitive layer, a charging unit for charging the image carrier, and a digital device having a predetermined resolution. An exposing unit that is driven based on the processed image data and scans and exposes the charged image carrier, and an electrostatic latent image formed on the image carrier by the exposure is visualized by a developer. Developing means, transfer means for transferring the developer image formed on the image carrier to a recording medium,
In an image forming apparatus provided with a fixing means for fixing the developer image transferred onto the recording medium by heating and pressurizing,
The image data group corresponding to one scanning area is set as one unit, and the data length and the image density of the data contributing to visualization are discriminated for each one unit or a plurality of units, and the above-mentioned is performed based on the data length and the image density. An image forming apparatus, wherein the amount of heat applied to the developer image is controlled by a fixing unit.

According to the second aspect of the present invention,
According to the first aspect of the present invention, there is provided a means for determining the type of recording medium, a means for determining whether the color of an image to be formed is a single color or a plurality of colors, and in addition to the data length and the image density,
This is achieved by controlling the amount of heat applied to the developer image by the fixing means based on the type of recording medium and the color of the image.

Further, according to the third invention of the present application, the above object is achieved by controlling the fixing temperature or the fixing speed in the first invention or the second invention. .

That is, according to the first invention of the present application, an image data group corresponding to one scanning region is set as one unit,
The data length and the image density of the data contributing to the visualization are discriminated for each one unit or a plurality of units, and the amount of heat applied to the developer image by the fixing unit is controlled based on the data length and the image density. For example, in the case of an image in which the area where the developer image is transferred is only a part of the recording medium, the area and other blank area are separated at the image data stage before the transfer is executed. It is determined that the amount of heat is increased only when the area is fixed. In addition, even when character images and image images are mixed, before transfer is performed,
The two images are discriminated at the stage of image data, and control is performed so that the amount of heat is larger than that of the character image portion when fixing the image portion.

According to the second aspect of the present invention,
In the first aspect of the present invention, the recording medium is provided with a unit for determining the type of recording medium and a unit for determining whether the color of an image to be formed is a single color or a plurality of colors. Since the amount of heat applied to the developer image is controlled by the fixing means based on the color of the image, the control according to the first aspect of the present invention is performed, and when OHT is used as the recording medium, when recording paper is used, for example. The control is performed so that the amount of heat is larger than that in the case of a single color image in the case of a full-color image.

Further, according to the third invention of the present application, in the first invention or the second invention, the control of the amount of heat controls the fixing temperature or the fixing speed.
For example, in the case of an image in which the area to which the developer image is transferred is only a part of the recording medium, before the transfer is performed,
At the stage of image data, the area is discriminated from other blank areas, and control is performed such that the fixing temperature is increased only when fixing the area or the fixing speed is decreased.

[0021]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. In this embodiment, the image forming apparatus of the present invention is applied to a laser beam printer as shown in FIG. 2, and this laser beam printer uses a photosensitive drum and a transfer drum to produce three colors (Y,
M, C) or 4 colors (Y, M, C, K) toner
A method is adopted in which a color image is obtained by transferring each color three or four times. It is also possible to obtain a single-color image by individually transferring the toner of each color. The configuration of the laser beam printer in this embodiment will be described below.

In FIG. 2, reference numeral 201 designates a photosensitive drum which is an image bearing member, and the surface layer of the photosensitive drum 201 is constituted by laminating a photoconductor on a conductive substrate and is rotatably arranged in the direction of the arrow. There is.

A primary charger 202 is disposed above the photosensitive drum 201, and constant current control or the like is performed so that the surface potential of the photosensitive drum 201 becomes constant regardless of environmental conditions and the history of the photosensitive drum. Then, the surface of the photosensitive drum 201 is uniformly charged.

The photosensitive drum 201 thus charged is
An electrostatic latent image is formed on the photosensitive drum 201 by an electrostatic force corresponding to the laser light by scanning with the laser light emitted from the laser beam scanner 203 which is an exposing unit.

This electrostatic latent image is transferred to the photosensitive drum 20.
By the rotation of 1, the toner is conveyed to a portion facing the developing device 204, which is a developing means, and is developed by the developing device 204 with each color toner.

The developing device 204 comprises a yellow developing device 204a with yellow toner, a magenta developing device 204b with magenta toner, a cyan developing device 204c with cyan toner, and a black developing device 204d with black toner. In each developing device, fixed magnets 300a, 300b, 300c, 300d are provided.
And developing rollers 302a, 302b, 302c, 302d each having a magnetic cylinder (sleeve) 301a, 301b, 301c, 301d for rotating the outer circumference thereof.
It is charged to a predetermined potential by friction with a, 301b, 301c, 301d.

Further, each developing device is supported by a support 207 which rotates in the direction of the arrow, and is sequentially moved to a portion facing the photosensitive drum 201. In the state shown in FIG. 2, the yellow developing device 204a is the photosensitive drum 20.
In this state, an interval of several hundred μm is maintained between the photosensitive drum 201 and the sleeve 301a, and an alternating electric field is generated by the bias generator (not shown). . Therefore, the electrostatic latent image is visualized by adhering the toner onto the photosensitive drum 201 in accordance with the electrostatic latent image formed by laser exposure while causing the toner to fly in this alternating electric field.

On the other hand, the transfer drum 208, which is a transfer means,
The recording paper supplied from the supply roller 209 is brought into contact with the photosensitive drum 201 in synchronism with the above-described image forming process, and the transfer charger 208a applies an electric charge having a polarity opposite to that of the toner to the surface of the recording paper to form the photosensitive drum. The toner on 201 is transferred onto a recording paper.

Photosensitive drum 201 on which a visible image is captured
In the drum cleaning unit 210, the residual toner on the photosensitive drum 201 is removed by a cleaning blade (not shown) to prepare for the image forming process with the toner of the next color.

Then, such exposure step, development step,
The transfer process and the drum cleaning process are performed three times depending on the number of colors used, for example, three times for Y, M, and C.
If M, C and K are repeated 4 times.

When the transfer is completed for all colors, the recording paper on which the toner image has been transferred in the above-mentioned transfer step is separated from the photosensitive drum 201 by the separating means 211, and is transferred onto the recording paper by the fixing device 212 which is the fixing means. The toner image is fixed on the recording paper by heating and fixing the toner, and then the recording paper on which the toner image is fixed is ejected by the paper ejection roller 213.

Here, thermal fixing will be described with reference to FIG. In the fixing device 212 according to the present exemplary embodiment, the heater 301 is incorporated inside the upper fixing roller 302, and the upper fixing roller 302 is warmed by the heater to set the surface temperature of the roller to about 160 to 200 ° C. Further, a lower fixing roller 304 is arranged so as to come into pressure contact with the upper fixing roller 302, and a predetermined nip portion is formed by these rollers. Then, the recording paper 305 is inserted into this nip portion, the toner 303 is melted by heat, and the toner melted by the pressure of the roller is melted and fixed to the recording paper 305.

The surface of the upper fixing roller 302 is coated with fixing oil (silicone oil) so that toner or recording paper does not adhere to it.

As described above, the toner on the recording paper is melted by being heated and pressed in the nip portion, and the temperature required for melting is the number of toner layers on the recording paper, that is, the color image. Or a monochrome image,
Further, it is different when OHT is used instead of recording paper.

Further, the image is not always printed on the entire recording paper, and there are cases in which only a few lines are printed and there are more blank areas. Also, even if one line of the image is taken, one line The width of the image in is also large and small. Furthermore, character images and image images may be mixed.

In such a case, fixing the entire recording paper at the same temperature is performed by heating which is partially unnecessary or is performed at a temperature higher than necessary. This means that energy is wasted.

Therefore, in the present embodiment, not only the color information of the image and the information of the type of the recording medium are taken into consideration, but also the image data length and the image density are discriminated for each line to be printed, and the fixing temperature is determined according to these. By changing the, the fixing temperature control is optimized. The temperature control in this embodiment will be described below.

First, the outline of the signal processing unit of this embodiment will be described with reference to FIG. In FIG. 1, R, G,
The image data of B is input to the LOG conversion units 102, 103, 104 of the image data processing unit 101. The LOG converters 102, 103, and 104 are composed of an LUT (look-up table) and a ROM (read-only memory), and convert the input R, G, B luminance signals into Y, M, C density data. To be done. In addition, UCR (Under C
The color remove unit 105 uses the known undercolor removal method to input the three primary color signals (Y, M,
C) is masked, and Y, M, and
The C and K signals are sequentially output to the FiFo memory 106.
Write once to.

The written data is read at a predetermined reading rate. At this time, the density level of each line is detected by the density detector 108 and the presence or absence of halftone density is sent to the selector unit 109 as Flag1.

As shown in FIG. 4, the density detector 108 uses a digital comparator 401, 402 to detect the image density. That is, the digital comparator 401 compares the input image data with the preset value P _1, and when the image density of the input image data is smaller than the preset value, the output becomes H, and the digital comparator 402 outputs the image density of the input image data with the preset value. The output becomes H when it is larger than P ₂ . Therefore, if the preset value P ₁ of the comparator 401 is set as the lower limit value of the halftone density and the preset value P ₂ of the comparator 402 is set as the upper limit value of the halftone density, the output of the comparator 401, the comparator 402 and the OR gate 403 for the input image data is set. Is as follows.

[0042]

[Table 1]

As described above, only when the image density of the input image data is halftone, the output of the OR gate 403, that is, F
lag1 becomes L. That is, when the input image is an image image, Flag1 is L because there is a halftone image.
In the case of a text image, Flag1 becomes H.

Then, the selector unit 109 uses this Fl
In order to reflect the content of ag1 in the heater control, a predetermined output to the heater control unit described later is performed.

Next, as described above, the FiFo memory 106
A method of discriminating the data length of one line written and read in will be described.

The determination of the data length is performed by the address counter 107 shown in FIG. 1. First, address control by the main scanning counter and the sub scanning counter will be described with reference to FIG.

The HSync signal input to the main scanning counter and the sub scanning counter is a synchronizing signal in the main scanning direction, and defines the main scanning start position in the "H" section. Further, the VSync signal input to the sub-scanning counter is a synchronization signal in the sub-scanning direction, and defines an image valid period during which the image is valid in the "H" section. The timing chart in FIG. 5 shows HSy in the main scanning direction.
This is an enlarged view of one cycle of the nc signal. The main scanning counter is reset by the HSync signal and generates an address as an n-bit counter by the clock (CLK) signal. The sub-scanning counter is reset by VSync and counts up the HSync signal to form an image line. In FIG. 5, the portion drawn as an ellipse is image data, and the numerical value in the ellipse indicates the data density.

As a result, in FIG. 5, the image data of the density FFHEX to 0AHEX of the first line has a data length of 8 addresses, and the density FFH of the second line is FFHEX.
The image data of EX to CCHEX has a data length of 7 addresses.

Therefore, the data length for one line can be grasped by counting this address.

The address counter 107 shown in FIG. 5 grasps the write address counter 601 managing the write address of the FiFo memory 106 as shown in FIG. 6 and the amount of written data in order to count such addresses. In order to hold the final address value updated by the write address counter at HSync, a read address counter 603 for reading the written data in synchronization with R-CLK, and a latched write address value. And a comparator 604 for comparing read address values.

Therefore, in the timing diagram shown in FIG. 7, when the write address counter 601 is reset by W-RST synchronized with the falling edge of W-CLK during the L period of HSync, thereafter, W-Dat synchronized with W-CLK is reset.
a is input to the FiFo memory 106 and written in the FiFo memory 106 at the falling edge of W-CLK, and at the same time, the write address (W-ADD) is also incremented by the write address counter 601. In addition, W-
CLK is configured to be generated by the number of W-Data.

Then, the written final address value is
The latch 602 latches and holds at the falling edge of HSync.

Next, during the L period of HSync, the read address counter 603 is reset by R-RST synchronized with the rising edge of R-CLK. Here, R-RST is reset before W-RST.

After that, from the FiFo memory 106 to RC
Data is read in synchronization with the rising edge of LK, and the read address counter 603 also reads the read address (R-AD
Increment D).

At the same time, the final value of the write address held in the latch 602 and the read address value are compared by the comparator 604. In the comparator 604, the output is L until the read address data and the previously latched address match, and the output becomes H when they match.

FIG. 7 shows the case of the data of the first line shown in FIG. 5. Flag2 becomes L at the start of reading and becomes H when the read address becomes 8 and the write address coincides. . That is, the output of Flag2 is as shown in Table 2 below.

[0057]

[Table 2]

Therefore, the period in which Flag2 is L is grasped as the data length, and this Flag2 is input to the selector unit 109 in FIG.
At 9, in order to reflect the content of this Flag 2, the output to the heater control section is performed as described later.

Next, the paper and color detector 110 shown in FIG.
A method for discriminating the paper type information and the color information will be described.

FIG. 8 is a block diagram of a full-color or mono-color discrimination unit and an output paper discrimination unit. Decoder 8
In 01, full color or mono color is discriminated from the inputted Y, M, C, K image data. The truth table is shown in Table 3.

[0061]

[Table 3]

As shown in Table 3, the output of the decoder 801 becomes H when it is determined to be a single color and L when it is determined to be a color.

In the sense amplifier 802, paper and OHT
Is determined. For this detection, a photocoupler is attached to the paper feeding unit, and in the case of paper, the light of the photocoupler is blocked, so the output of the sense amplifier 802 becomes H, and the OHT
In this case, since light passes through, the output of the sense amplifier 802 becomes L.

Therefore, the output of the OR gate 803, F
lag3 is as shown in Table 4.

[0065]

[Table 4]

This Flag3 is the selector unit 1
09, and the selector unit 109 outputs to the heater control unit so as to reflect the contents of Flag3 as follows. Hereinafter, the selector unit 109 that outputs to the heater control unit based on the content of each Flag described above,
The control by the heater controller will be described.

The Flag signals described above are shown in Table 5 below.
It is summarized like.

[0068]

[Table 5]

As described above, the Flag whose level is H
The larger the number, the smaller the amount of heat required for fixing. Therefore, the selector unit 109 outputs to the heater control unit according to the number of Flags having the level H. In other words, F of level H
When the number of lags is 0, the fixing temperature is the highest, and when the number of Flags with the level H is 3, the fixing temperature is the lowest, the four-stage voltage (hereinafter, referred to as Flag level) is applied. The fixing temperature is controlled by outputting to the heater controller.

This heater controller has a structure as shown in FIG. 9, and the OSC 901 as an oscillator is shown in FIG.
As indicated by A, it oscillates at a predetermined frequency. The signal is converted into a sawtooth waveform as shown in B of FIG. 10 by an integrator 902 composed of OP-AMP.

Next, the value of the thermistor for detecting the temperature or the Flag signal described above is sent to the comparator 903 as shown in FIG.
When it is input like C of 0, the sawtooth waveform is compared with the above input value in the comparator 903, and
The output to the heater driver according to the Flag level is obtained as in the case of D, and the PWM control is performed.

That is, when the Flag level is high in accordance with the Flag level output from the selector unit 109 shown in FIG. 5, the heater driver is controlled to lower the temperature of the heater, and conversely the Flag level is low. And control to raise the temperature of the heater is performed.

The output from the selector unit 109 to the heater control unit takes into consideration the time until the toner image is transferred to the recording paper and reaches the fixing device 212, the delay of heat transfer due to the heat capacity of the fixing roller 302, and the like. Is done.

By carrying out such control, the temperature of the heater becomes higher in the color mode than in the monochrome mode,
Further, the temperature of the heater is lower in the area where the image is not drawn than in the area where the image is continuously written.

As described above, according to the present invention, it is possible to optimize the fixing control according to the image.

(Second Embodiment) Next, a second embodiment of the present invention will be described. In the above-described first embodiment, not only the determination of the color and the single color and the determination of the type of the output paper sheet is detected by a predetermined detector, but also a plurality of input image continuity and image density are detected. However, the present invention is not limited to this example, and either one of the above can be applied, for example.

Furthermore, in the first embodiment described above, various F
The temperature of the heater was controlled according to the lag signal,
The same effect as in the first embodiment can be obtained not only in the temperature control of the heater but also in the configuration of controlling the motor rotation speed of the fixing roller.

Further, although the laser beam printer is described in the first embodiment of the present invention, the present invention is not limited to this, and an image forming apparatus using toner as a medium (image copying apparatus and It can also be applied to a monochrome image forming apparatus).

[0079]

As described above, the first embodiment according to the present application is described.
According to the invention, the image data group corresponding to one scanning region is set as one unit, and the data length and the image density of the data contributing to visualization are determined for each one unit or plural units, and the data length Since the fixing unit controls the amount of heat applied to the developer image based on the image density, a stable output image can be obtained. Further, since the amount of heat is reduced in the area where the image data is not output, it is possible to reduce the power consumption depending on the output image.

According to the second aspect of the present invention,
In the first aspect of the present invention, the recording medium is provided with a unit for determining the type of recording medium and a unit for determining whether the color of an image to be formed is a single color or a plurality of colors. Since the amount of heat applied to the developer image is controlled by the fixing unit based on the color of the image, a more stable output image can be obtained, and the power consumption can be further reduced.

Further, according to the third invention of the present application, in the first invention or the second invention, the control of the amount of heat controls the fixing temperature or the fixing speed.
It is possible to optimize the fixing process with a simple structure by utilizing the conventional device structure.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of an image data processing unit according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an outline of an image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a diagram showing an outline of a fixing device according to the first embodiment of the present invention.

FIG. 4 is a block diagram showing an outline of an image density detecting unit according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a state of image data developed on a recording sheet according to the first embodiment of the present invention.

FIG. 6 is a block diagram showing an outline of a data length determination unit in the first embodiment of the present invention.

FIG. 7 is a timing chart of reading / writing image data according to the first embodiment of the present invention.

FIG. 8 is a block diagram showing an outline of a paper and color detector according to the first embodiment of the present invention.

FIG. 9 is a block diagram showing an outline of a fixing heater control unit in the first embodiment of the present invention.

FIG. 10 is a timing chart of fixing heater control according to the first embodiment of the present invention.

FIG. 11 is a diagram showing an outline of an electrostatic latent image forming unit in a conventional image forming apparatus.

FIG. 12 is a diagram showing an outline of an entire conventional image forming apparatus.

[Explanation of symbols]

110 paper and color detector (means for discriminating the type of recording medium, 201 of the image to be formed, photosensitive drum (image carrier) 202 primary charger (charging means) 203 laser beam scanner (exposure means) 204 developing device (developing Means) 205 transfer drum (transfer means) 207 fixing device (fixing means)

Claims (3)

[Claims] 1. An image bearing member having a photosensitive layer, a charging unit for charging the image bearing member, and a driven image carrier which is driven based on image data digitally processed at a predetermined resolution to scan the charged image bearing member. And exposing means, and developing means for developing the electrostatic latent image formed on the image carrier by the developer with the developer, and the developer image formed on the image carrier to the recording medium. In an image forming apparatus equipped with a transfer means for pressing and a fixing means for fixing the developer image transferred on the recording medium by heating and pressing, one group of image data corresponding to one scanning region is set as one unit. Alternatively, the data length and the image density of the data contributing to the visualization are discriminated for each unit, and the amount of heat applied to the developer image by the fixing unit is controlled based on the data length and the image density. Do Image forming device. 2. A means for determining the type of recording medium and a means for determining whether the color of an image to be formed is a single color or a plurality of colors, and in addition to the data length and the image density, the type of recording medium and the image The image forming apparatus according to claim 1, wherein the amount of heat applied to the developer image by the fixing unit is controlled based on the color. 3. The amount of heat is controlled by controlling a fixing temperature or a fixing speed.
Alternatively, the image forming apparatus according to claim 2.