JPH09197911A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve fixing performance in a halftone density part, and simultaneously setting a required fixing condition for each image density. SOLUTION: In this digital image forming device for processing the image data as the multi-valued digital image data for instance, in the case of the density data application processing of the image data in the image signal processing circuit, the density data as the multi-valued digital image data is inputted by density data detecting means (step S10), a ratio of the halftone density data to the density data of whole image is calculated (Step S11), and corresponding to the ratio, the fixing condition for instance, the fixing temp. is set to any one of the normal mode, the intermediate temp. mode or the high temp. mode (step S12 to S14).

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 using an electrophotographic system.

[0002]

2. Description of the Related Art In the conventional image forming apparatus, the control of the fixing temperature control temperature is performed by switching the fixing temperature control temperature step by step according to the number of copies or the number of output sheets, or the fixing temperature control depending on the paper size (transfer material size). There is a method of switching the temperature control temperature, or a method of switching a partial temperature control temperature of the fixing device depending on the paper passing size such as heating only the paper passing area for each paper size in the longitudinal direction of the fixing device.

The type of transfer material (thickness, weighing, OHP
There is also used a configuration in which the fixing speed is changed by a special paper such as a sheet or a postcard, and for a paper type that is difficult to fix, the fixing speed is changed such as increasing the fixing time.

[0004]

However, in the above-mentioned conventional example, the fixing temperature is controlled stepwise by the number of copies (the number of outputs), the sheet size (size of the transfer material) and the paper type (type of the transfer material). Or, the fixing speed is changed, but since the fixing control based on the image density is not performed, the fixability is particularly high in the high density part (generally the halftone or highlight part). It may become worse than the solid part called solid black).
In some cases, the fixability of a photographic image is significantly deteriorated as compared with a normal character image.

Further, conditions such as fixing temperature and speed necessary for actual image density are not set for temperature control depending on the number of output sheets, size and type of transfer material, and the density is changed. In some cases, fixing failure may occur when the image density is changed by performing image processing.

Therefore, an object of the present invention is to provide an image forming apparatus capable of improving the fixing property in the halftone density portion and at the same time setting necessary fixing conditions for each image density.

[0007]

According to the first invention of the present application, the above-mentioned object is to carry out multi-value quantization processing at least once between the input of image data and the output to the exposure means. Means, an image carrier on which an electrostatic latent image corresponding to image data is formed by exposure from the exposing means, and a developing device for visualizing the electrostatic latent image on the image carrier with a developer image A transfer means for transferring the developer image onto the transfer material, and a fixing device for fixing the developer image on the transfer material by heating and pressing the transfer material and the developer image on the transfer material. In a provided digital image forming apparatus, density data detecting means for calculating a ratio of predetermined density data in a predetermined image area or in a predetermined range, and the fixing device gives the density data based on the ratio detected by the density data detecting means. Heat or pressure Properly it is achieved by having a control means for increasing or decreasing both.

According to the second invention of the present application,
In the first aspect of the invention, the control means for increasing or decreasing the heat and / or the pressure applied by the fixing device is a means for varying the fixing temperature, the fixing speed, the fixing pressure, or the fixing nip width. Is,
Alternatively, it is achieved by being a means for controlling the variable means.

Further, according to a third invention of the present application, the above object is the same as that of the first invention or the second invention, wherein the control means is connected to a means for detecting a concentration change, or This is achieved by providing a means for detecting a density fluctuation and setting a control value determined by calculating a ratio of predetermined density data so as to be corrected corresponding to the density fluctuation.

According to the fourth invention of the present application,
The above-mentioned object is, in the above-mentioned first invention or second invention, the control means is connected to a means for detecting a concentration fluctuation, or is provided with a means for detecting the concentration fluctuation,
This is achieved by setting the reference value of the ratio of the predetermined density data, which serves as a reference when switching the control value, so as to be corrected corresponding to the density fluctuation.

Further, according to a fifth invention of the present application, in the above-mentioned object, in any one of the first invention to the fourth invention, the control means is a fixing temperature, a fixing speed,
This is achieved by setting the fixing pressure and the fixing nip width to be variable at least two or more at the same time.

That is, according to the first invention of the present application, the image signal at the time of image formation is detected, and the fixing condition is made variable according to the ratio of the image signal of the halftone density portion in the image signal. Therefore, an image having a halftone density, which easily deteriorates the fixability, is satisfactorily formed.

Further, according to the second invention of the present application,
Since the fixing condition is the fixing temperature, the fixing speed, the fixing pressure, or the fixing nip width, it is possible to apply sufficient heat and / or pressure to an image of a halftone density which easily deteriorates the fixing property. Get fixability.

Further, according to the third invention of the present application, the control means is connected to the means for detecting the concentration fluctuation, or has a means for detecting the concentration fluctuation.
Since the control value determined by calculating the ratio of the predetermined density data is corrected in accordance with the density fluctuation, for example, even in a device in which the density can be adjusted by the user, sufficient heat or pressure or Both are imparted to obtain good fixability.

According to a fourth aspect of the present invention,
The control means is connected to the means for detecting the concentration fluctuation,
Alternatively, a means for detecting the density fluctuation is provided, and the reference value of the ratio of the predetermined density data, which serves as a reference when switching the control value, is corrected according to the density fluctuation, so that the user can freely adjust the density. Even in the apparatus described above, sufficient heat and / or pressure are applied to the image having the halftone density to obtain good fixing property.

Further, according to the fifth invention of the present application, the control means is set so that at least two fixing temperatures, fixing speeds, fixing pressures, and fixing nip widths can be simultaneously changed. Further, heat and / or pressure are more appropriately applied to the image having a halftone density to obtain a better fixing property.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment according to the present invention will be described with reference to FIGS. FIG. 3 shows an electrophotographic digital copying machine as an image forming apparatus in this embodiment. In FIG. 3, reference numeral 31 is a document to be copied, and the image of this document 31 is the lens 3
The image is projected onto the CCD device 61 by 2. CCD device 6
Reference numeral 1 decomposes the image of the original 31 into a large number of pixels and generates a photoelectric conversion signal corresponding to the density of each pixel. And this C
The analog image signal output from the CD device 61 is sent to the image signal processing circuit 34, where it is converted into a pixel image signal having an output level corresponding to the density of the pixel and sent to the laser driver substrate 70. To be

The laser driver substrate 70 forms and outputs a laser drive pulse having a width (time length) corresponding to the level of each pixel image signal input, and the laser drive pulse is sent to the laser emitting device 71. Supplied,
The laser light emitting device 71 is caused to emit light for a time corresponding to the pulse width thereof, and electrostatic latent images having different dot sizes are formed on the photosensitive drum 40 corresponding to the density of the pixel.

That is, the laser beam 36a emitted from the laser emitting device 71 is swept by the rotary polygon mirror 37, and the lens 38 such as an f / θ lens and the laser beam 36 are scanned.
A fixed mirror 39 that directs a toward the photosensitive drum 40 forms a spot image on the photosensitive drum 40 as an image carrier. Thus, the laser beam 36a scans the photosensitive drum 40 in a direction (main scanning direction) substantially parallel to the rotation axis of the photosensitive drum 40 to form an electrostatic latent image.

The photosensitive drum 40 is an electrophotographic photosensitive drum that has amorphous silicone, selenium, OPC, etc. on its surface and rotates in the direction of the arrow. After being uniformly discharged by the exposing device 41, it is uniformly discharged by the primary charging device 42. Be charged to. Then, the laser beam 36a modulated corresponding to the above-mentioned image information signal is exposed and scanned, whereby an electrostatic latent image corresponding to the image information signal is formed.

The electrostatic latent image is reversely developed by the developing device 43 using a developer such as toner particles to form a visible image (toner image), and then the electrostatic latent image is stretched between the two rollers 45 and 46. It is stretched and transferred to the transfer material 48 held on the transfer material carrying belt 47 which is endlessly driven in the direction of the arrow in the figure by the action of the transfer charger 49 as a transfer means.

Further, the transfer material 48 on which the toner image is transferred in this manner is separated from the transfer material carrying belt 47 and conveyed to the fixing device 51, and is nipped by the fixing roller 52 having the heater 53 and the pressure roller 54. It is conveyed, heated and pressed to be fixed on the transfer material 48 as a permanent image.

The residual toner remaining on the photosensitive drum 40 after the transfer is removed by the cleaner 50 thereafter.

Next, FIG. 2 shows a block diagram of the image signal processing circuit 34 and its periphery in the image forming apparatus of the present embodiment as described above. In FIG. 2, reference numeral 1 denotes a data processing circuit which constitutes the above-mentioned image signal processing circuit 34, and CC
It is a circuit for converting an image signal read by the D device 61 into multi-valued digital image data. Further, 2 is a density processing circuit for converting the multivalued digital image data into density data, and 3 is D / A conversion for converting the digital image signal sent from the density processing circuit 2 into an analog signal for laser emission. In the circuit.

The density data from the density processing circuit 1 is output not only to the D / A conversion circuit 3 but also to the density data detecting means 4, and the output of the density data detecting means 4 is the temperature control temperature controlling means 5. It is designed to be output to.

In the above-mentioned structure, multi-valued digital image data (8b in this embodiment) created by the data processing circuit 1 after being read by the CCD device 61.
(it 256 gradation digital image data) is input to the density processing circuit 2, the density processing circuit 2 performs a brightness density (LOG) conversion for converting the data that was the brightness data into the density data. The image data obtained by the processing up to this point is converted into output data according to the mode in which the data is output (character mode, character photo mode, etc.) (for example, 50H data is converted to 60H).
(80H data is converted to 85H), and the data is output to the D / A conversion circuit 3 as output data.

The digital image data sent to the D / A conversion circuit 3 is converted in the D / A conversion circuit 3 from the digital image data up to that time into analog data for laser output data (this is converted to D / A). (Referred to as conversion), and sent to the laser driver substrate 70 which is the exposure means.

After that, the laser is emitted by the laser emitting device 71 based on the data created as the laser output data in the laser driver substrate 70 as described above, and the photosensitive laser 40 is exposed by the emitted laser. A latent image is formed on the surface of the transfer material, a developing device 34 visualizes the latent image with toner, a transfer charger 49 transfers the image to a transfer material 48, and a fixing device 51 fixes the toner on the transfer material 18, and the transfer material is discharged from the paper exit. 18 is discharged and a copy output is made.

The multivalued digital image data that has passed through the density processing circuit 2 described above is not only output to the D / A conversion circuit 3 of the image signal processing circuit 34 for image formation as described above, but also It is output to the concentration data detection means 4,
Based on the detection result, the temperature control temperature control unit 5 controls the fixing temperature control temperature according to the image density.

FIG. 1 shows a flow chart of the temperature control temperature control by the concentration data detecting means 4 and the temperature control temperature control means 5.
Shown in As shown in FIG. 1, first, the multi-valued digital image data determined by the density processing circuit 2 is input (step S10), and based on the multi-valued digital image data, the halftone density occupying in the whole image data is input. The ratio of the data of the set is determined (step S11).

In the present embodiment, hexadecimal numbers are used as the 256 gradation 8-bit image data, for example, 00.
H has the lowest density, FFH has the highest density, and is around 80H, which represents the vicinity of the halftone density. Therefore, for each image data, one pixel is counted for each density or for each range of certain density, and the ratio of the data of 50H to A0H (hexadecimal number), which is considered to be halftone, in the counted density is the entire image. The ratio shown in is calculated.

Then, as a result of the discrimination, if the ratio of the halftone density portion is, for example, 20% or less with respect to all the image data, the fixing temperature control temperature is determined to be 185 ° C. in the normal mode (step). S12). In addition, the ratio of the detected halftone density portion is, for example, 20% for all image data.
If it is ~ 40%, 200 ℃ as medium temperature mode
The fixing temperature control temperature is determined (step S13). Further, when the ratio of the detected halftone density portion is, for example, 40% or more with respect to all the image data, the fixing temperature control temperature is determined to be 215 ° C. as the high temperature mode (step S14).

Consider, for example, A4 size data of 400 dpi 256 gradations.
There is data of about 15 million pixels, and each pixel of the data has data of 256 gradations of 00H to FFH. Then, if the data of the halftone density portion (density of density 0.3 to 0.8 in Macbeth densitometer) of the data of 256 gradations is, for example, 50H to A0H, the total number of pixels is 15 million pixels. Of these, the number of pixels having data of 50H to A0H is counted. Result 5
For example, when the ratio of 0H to A0H in all pixels is 20% or less, the fixing temperature is adjusted to 185 ° C., 20 to 40% to 200 ° C., and 40% or more to 215 ° C., respectively. Change the temperature.

This is because, even if fixing is carried out at the same temperature, the fixability varies greatly depending on the image density, and therefore the fixability is particularly high in the halftone density area as compared with the low density area and the high density area. This is to prevent the deterioration. Further, if the fixing temperature is set to be high as an initial setting state from a normal time, there is a concern that a high temperature offset or an excessive temperature rise in the machine may adversely affect other parts. Therefore, it is effective to raise the fixing temperature as much as necessary only for an image having many halftone density portions.

Therefore, out of the total of 15 million pixels, the halftone density portion has approximately 1.5 million pixels (for example, a document containing only characters).
If so, the halftone density portion in the whole is 10%,
At this time, the temperature adjustment temperature control is performed in the normal mode, and the fixing device adjusts the fixing temperature at 185 ° C. In addition, the halftone density area is approximately 4.5 million pixels (for example, a document with mixed text and photographs).
If so, it is 30% with respect to the whole, and at this time, the temperature control temperature control is performed as the medium temperature mode, and the fixing device controls the fixing temperature at 200 ° C. If the halftone density portion is about 7.5 million pixels (for example, a manuscript only for a photograph), it is 50% of the whole. At this time, the temperature adjustment temperature control is performed in the high temperature mode, and the fixing device sets the fixing temperature at 215 ° C. Adjusted. Therefore, the higher the halftone density of the image, the higher the fixing temperature,
It is possible to improve the fixability.

As described above, the fixing temperature control temperature can be changed according to the image ratio of the halftone density portion to the entire image of the digital image data, so that better fixing performance can always be obtained regardless of the image. In addition, in order to determine the temperature control temperature for each sheet (for each image), it is possible to prevent offsets at high and low temperatures, and prevent adverse effects on other parts and units due to excessive temperature rise inside the machine. It will be possible.

Further, in the present embodiment, the detection is set to three stages of 20% or less, 20 to 40%, and 40% or more for convenience, but a method of setting the detection percentage or changing the switching stage is also possible. It is possible, for example, to make it possible to change the setting for each machine type, region, etc. (difference in the type of paper used), and how to increase the number of switching steps and perform more detailed control. It is also a very effective means when considering the harmful effects on the machine body.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 4 is a flowchart of the fixing speed control in the second embodiment of the present invention. First, the multivalued digital image data determined by the density processing circuit 2 is input (step S20), and this multivalued Based on the digital image data, the ratio of the data of the halftone density portion in the entire image data is determined (step S21). Next, when the ratio is 20% or less with respect to all the image data, the fixing speed is determined to be 100 mm / sec which is equal to the process speed as the normal mode (step S).
22). Similarly, when it is 20 to 40%,
8 which is 0.8 times the process speed as a low speed mode
The fixing speed is determined to be 0 mm / sec (step S2
3). Similarly, if it is 40% or more, it is 0.5 times the process speed as the ultra-low speed mode.
The fixing speed is determined to be 0 mm / sec (step S2
4).

In the above configuration, the method of processing multi-valued digital image data and the method of calculating the ratio of halftone density portion data are the same as those in the first embodiment. In this embodiment, the image ratio of the detected halftone density portion is detected. To change the fixing speed,
Improves fixability.

Even if the method of changing the fixing speed is used as described above, it is possible to improve the fixing property depending on the density as in the first embodiment.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIGS. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 5 is a flow chart of the fixing pressure control in the third embodiment of the present invention. First, the multivalued digital image data determined by the density processing circuit 2 is input (step S30), and this multivalued Based on the digital image data, the ratio of the data of the halftone density portion in the entire image data is determined (step S31). next,
The calculated ratio of halftone density area is 2 for all image data.
When it is less than 0%, it is 7kg as normal mode.
Then, the fixing pressure is determined (step S32). Similarly, when it is 20 to 40%, the fixing pressure is set to 10 kg as the intermediate pressure mode (step S33).
Further, similarly, when it is 40% or more, the fixing pressure is set to 15 kg as the high pressure mode (step S3).
4).

FIG. 6 shows a fixing pressure adjusting means in this embodiment. In FIG. 6, reference numeral 52 is an upper fixing roller, and the fixing heater 5 is provided inside the upper fixing roller 52.
3, the upper fixing roller 52 is in pressure contact with the lower fixing (pressing) roller 54. A fixing pressure member 56 is attached to the lower fixing roller shaft 55, and one end of the fixing pressure member 56 is swingably supported by a shaft 57. Further, the other end of the fixing pressure member 56 is connected to the movable portion of the solenoid 58, and the spring 5
It is urged downward by 9.

In such a structure, as shown in FIG. 6, the fixing pressure is determined by the pressure at the contact point between the upper fixing roller 52 and the lower fixing roller 54 (referred to as the Nip portion), so that the halftone density data By driving the solenoid 58 by the fixing pressure control means (not shown) and moving the fixing pressure member 56 according to the ratio, the fixing pressure can be changed to the above-mentioned normal mode, intermediate pressure mode, and high pressure mode. It is possible to improve the fixability.

As a means for adjusting the fixing pressure, a stepping motor or the like can be used instead of the solenoid described in this embodiment, and the pressure can be controlled more finely.

Also in the above configuration, the method of processing multivalued digital image data and the method of calculating the ratio of halftone density portion data are the same as those in the first embodiment.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the present embodiment, in addition to the contents described in the first embodiment, the image density adjustment that can be adjusted by the user is also taken into consideration and controlled. The control in this embodiment will be described based on Table 1.

[0051]

[Table 1]

In Table 1, in the case of a normal image, the density adjustment is set to 0, and the normal mode is 20% or less, the medium temperature mode is 20 to 40%, and the high temperature mode is 40% or more.
However, if the user changes the density by +3 by the density adjustment function that can be arbitrarily adjusted, the image density becomes darker as a whole, so the normal mode setting is 20% and the image density is 20%.
What was below was 29% or less at setting +3, medium temperature mode was 20-40% to 29-49%, and high temperature mode was 4%.
The detection ratio is changed from 0% or more to 49% or more. On the other hand, when the concentration adjustment is set to -4, the detection ratios in the normal mode, the medium temperature mode, and the high temperature mode are 8% or less and 8% to 8%, respectively.
The fixing temperature is set to 28%, 28% or more, and in each case, the fixing control temperature is set in the same manner as described in the first embodiment.

By thus changing the detected image ratio in conjunction with the density adjustment, the fixing temperature can be determined more finely depending on the image.

In the present embodiment, the image density adjustment is not performed in the image signal processing circuit 34, but the density conversion is performed in a circuit downstream of the density processing circuit 2, and the density data detection means 4 changes the density. This method is particularly effective for the case where the above process is not incorporated, or for the configuration in which the density is changed by the laser light amount, the developing bias, and the like.

(Fifth Embodiment) Next, a fifth embodiment of the present invention will be described. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The present embodiment has an image density adjusting function in addition to the contents described in the first embodiment, and controls in accordance with the function. In the present embodiment, the fourth
As in the above embodiment, the reference value of the halftone density image signal is set to 50.
In contrast to the method of fixing H to A0H and changing the ratio when classifying by mode, a method of changing the reference value of the halftone density image signal and fixing the ratio when classifying by mode is used. Used. Hereinafter, the control of the present embodiment will be described based on Table 2.

[0057]

[Table 2]

In Table 2, in the case of a normal image, the density adjustment is set to 0, and the halftone density signal value is 50H to A0H.
The data of is counted, and as a result, the normal mode, medium temperature mode, and high temperature mode are changed.

At this time, the density is increased by adjusting the image density.
When it is set to 3 and is set to the dark side, the halftone density signal value set from 50H to A0H at 0 is set to 3
The data of 8H to 88H is counted, and the fixing temperature control temperature switching to each mode is performed without changing the ratio of the image ratio to the entire image in each of the normal mode, the medium temperature mode, and the high temperature mode. On the other hand, when the image density adjustment is set to -4, the halftone density signal value is 70H to
Since the data of C0H is used, it is possible to switch to the fixing temperature control temperature without changing the ratio of the halftone density signal in the image.

By using this method, since only the reference signal value is changed in conjunction with the density adjusting function, the fixing temperature can be finely set by a simple control method.

(Sixth Embodiment) Next, a sixth embodiment of the present invention will be described. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the present embodiment, in addition to the contents described in the first embodiment, when the density adjusting function is provided, the fixing temperature control temperature is switched more finely. The control of this embodiment will be described below based on Table 3.

[0063]

[Table 3]

As shown in Table 3, when the image density adjustment is changed, the setting of the fixing temperature control temperature in each mode is changed.

As described above, by directly changing the fixing temperature control temperature with respect to the density adjustment, it becomes possible to set finer and more appropriate fixing conditions.

(Seventh Embodiment) Next, a seventh embodiment of the present invention will be described. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

This embodiment is the fourth embodiment and the fifth embodiment.
As described in the sixth embodiment, in the case where the fixing property is improved in consideration of the density change by the density adjusting function, the fixing temperature control temperature is not controlled, but the fixing temperature is adjusted in the second and third embodiments. As described above, the fixing speed and the fixing pressure are changed.

Also in this embodiment, the fixing property can be improved by a simple control system in cooperation with the density adjusting function.

(Eighth Embodiment) Next, an eighth embodiment of the present invention will be described. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

This embodiment is based on the first embodiment described above.
By combining the respective methods described in the seventh embodiment, for example, by changing the fixing temperature and speed at the same time, or by interlocking with the density adjusting function, the + side changes the halftone density signal value, and the-side changes the intermediate density signal value. A method such as changing the ratio of the density signal is used.

According to this embodiment, it is possible to further improve the fixability.

(Ninth Embodiment) Next, a ninth embodiment of the present invention will be described. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In this embodiment, the input data is multivalued and the output data is a binary image. In this case, the density data detection is performed at the stage of the multivalued data before the image data is binarized. The same processing can be performed by determining the halftone density ratio by the means 4.

(Tenth Embodiment) Next, the first embodiment of the present invention will be described.
No. 0 embodiment will be described. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The present embodiment is a case where even a part of the data from the input data to the output data is multivalued.
The processing of the first to eighth embodiments is performed on the multi-valued data.

That is, according to the present invention, the position or timing at which the halftone density data is discriminated by the density data detecting means is not limited to the case of the above-described embodiment, and the position at which the data is multi-valued is appropriately selected. Or you can do it at the right time.

[0077]

As described above, the first embodiment according to the present application is described.
According to the invention, the image signal at the time of image formation is detected, and the fixing condition is made variable according to the ratio of the image signal of the halftone density portion in the image signal. It is possible to improve the fixability of an image with a large number of characters (a document including a mixture of characters and photographs, a FAX, an LBP, a file image in a photograph original).

According to the second aspect of the present invention,
Since the fixing condition is the fixing temperature, the fixing speed, the fixing pressure, or the fixing nip width, it is possible to apply sufficient heat and / or pressure to an image of a halftone density which easily deteriorates the fixing property. Fixability can be obtained.

Further, according to the third invention of the present application, the control means is connected to the means for detecting the concentration fluctuation, or is provided with the means for detecting the concentration fluctuation,
Since the control value determined by calculating the ratio of the predetermined density data is corrected in accordance with the density fluctuation, for example, even in a device in which the density can be adjusted by the user, sufficient heat or pressure or Both of them can be imparted to obtain good fixability.

According to the fourth aspect of the present invention,
The control means is connected to the means for detecting the concentration fluctuation,
Alternatively, a means for detecting the density fluctuation is provided, and the reference value of the ratio of the predetermined density data, which serves as a reference when switching the control value, is corrected according to the density fluctuation, so that the user can freely adjust the density. Also in the apparatus described above, sufficient heat and / or pressure can be applied to an image having a halftone density to obtain good fixing property.

Further, according to the fifth aspect of the present invention, the control means is set so that at least two fixing temperatures, fixing speeds, fixing pressures, and fixing nip widths can be varied simultaneously. Further, it is possible to more appropriately apply heat and / or pressure to an image having a halftone density to obtain a better fixing property.

[Brief description of drawings]

FIG. 1 is a flowchart of fixing condition control by halftone density detection according to the first embodiment of the present invention.

FIG. 2 is a block diagram around an image signal processing circuit according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a schematic configuration of an image forming apparatus according to a first embodiment of the present invention.

FIG. 4 is a flow chart of fixing condition control by halftone density detection according to the second embodiment of the present invention.

FIG. 5 is a flowchart of fixing condition control by halftone density detection according to the third embodiment of the present invention.

FIG. 6 is a diagram illustrating a mechanism for changing a fixing pressure in a third embodiment of the present invention.

[Explanation of symbols]

 4 Concentration Data Detecting Means 5 Temperature Controlling Temperature Control Means (Control Means) 40 Photosensitive Drum (Image Carrier) 43 Developing Device 48 Transfer Material 49 Transfer Charger (Transfer Means) 51 Fixing Device 70 Laser Driver Substrate (Exposure Means) 71 Laser Light emitting device (exposure means)

Claims (5)

[Claims] 1. A means for multi-value processing image data at least once during the period from the input of the image data to the output to the exposure means, and a static image corresponding to the image data by the exposure from the exposure means. An image carrier on which a latent image is formed,
A developing device that visualizes the electrostatic latent image on the image carrier with a developer image, a transfer unit that transfers the developer image to a transfer material, and the transfer material and the developer image on the transfer material. In a digital image forming apparatus provided with a fixing device for fixing the developer image to the transfer material by heating and pressurizing, a density data detecting means for calculating a ratio of predetermined density data in a predetermined image area or in a predetermined range. An image forming apparatus, comprising: a control unit that increases or decreases heat and / or pressure applied by the fixing device based on a ratio detected by the density data detection unit. 2. The control means for increasing or decreasing the heat and / or pressure applied by the fixing device is a means for changing the fixing temperature, the fixing speed, the fixing pressure, or the fixing nip width, or the variable. The image forming apparatus according to claim 1, wherein the image forming apparatus is a unit that controls the setting unit. 3. The control means is connected to a means for detecting density fluctuation, or comprises means for detecting the density fluctuation, and the control value determined by calculating the ratio of predetermined density data is used as the density fluctuation. The image forming apparatus according to claim 1 or 2, wherein the image forming apparatus is set so as to be corrected in accordance with. 4. The control means is connected to a means for detecting density fluctuations, or comprises means for detecting the density fluctuations, and is a reference for a ratio of predetermined density data to be a reference when switching control values. The image forming apparatus according to claim 1, wherein the value is set so as to be corrected according to the density variation. 5. The control means is set so that at least two or more fixing temperatures, fixing speeds, fixing pressures, and fixing nip widths can be varied at the same time. The image forming apparatus according to item 1.