JP2006171104A - Image forming apparatus and method for setting control value therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently and appropriately adjust the density and the glossiness of an output image. <P>SOLUTION: After preferentially setting a density control value (developing bias or the like), based on detected density from a patch image first (S8 and S9), a glossiness control value (fixing temperature or the like) is set by adding the set result of the density control value (developing bias or the like) in addition to the detected glossiness from the patch image (S10 and S11). Then, recording material where a toner image has been thermally fixed is reconveyed to a detecting position by a sensor for detecting the density and the glossiness of the image on the recording material to which thermal fixing has not been performed yet (S6), and the glossiness thereof after the thermal fixing is detected (S7), thereby using the sensor both as a density detection sensor and a glossiness detection sensor. Before performing image formation based on a printing requirement (S13), the patch image is formed on an opposite surface to the image formation surface (S3) so as to set the density control value and the glossiness control value. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that forms a toner image on an image carrier, transfers the toner image to a predetermined recording material, and heat-fixes the image forming apparatus, and a method for setting control parameter setting values (control values). .

In an electrophotographic image forming apparatus configured as a printer, a copier, a facsimile, or a complex machine thereof, light is irradiated onto a photosensitive drum (a typical example of an image carrier) charged by a charging device. An electrostatic latent image is written, and toner is supplied to the photosensitive drum by a developing device to develop the electrostatic latent image as a toner image (form a toner image), and the toner image is recorded on a predetermined recording medium such as recording paper. The image is directly transferred to the material or indirectly via an intermediate transfer material such as an intermediate transfer belt, and finally heated and fixed by a heating roller or the like provided in the fixing device.
By the way, as a representative index for quality evaluation of an image (toner image) formed on a recording material by such an image forming apparatus, there are a density and a glossiness of the image. Here, in general, the image density is the intensity (light quantity) obtained by one or a combination of the intensity of light irradiating the target image and the intensity (light quantity) of scattered light and specular reflected light. Assessed by relative comparison. Further, the gloss level of an image is generally evaluated by a relative comparison between the intensity of light irradiating the target image and the intensity of the regular reflection light.
Hereinafter, this glossiness is referred to as glossiness. The glossiness referred to in this specification is the so-called specular glossiness (75-degree specular gloss when the recording material is paper or the like, or the recording material is plastic, coating film This is a concept that includes all indexes representing the glossiness of an image. Similarly, the image density (or density) referred to in this specification is log (I ₁ / I ₂ ) [where I _{1 is} the intensity of incident light on the image, I _{2 is} the intensity from the image. This is a concept that includes not only the density determined by the intensity of the reflected light] but also all indexes representing the density of the image.
Conventionally, in order to obtain an image of an appropriate density, a predetermined test patch image is formed on a photosensitive drum, and the image on the photosensitive drum or the image after it is transferred to an intermediate transfer member A density is detected by a density sensor, and a parameter setting value (hereinafter referred to as a density control value) used for density control of an image (toner image) is set according to the difference between the detected value and a target density that should be detected. Has been.
For example, in Patent Document 1, the density of a patch image is obtained based on a difference value between a regular reflection light quantity and an irregular reflection light quantity (scattering light quantity) from the image, and a developing bias potential and a photoconductor are obtained based on the obtained image density. An image forming apparatus is shown that determines setting values (an example of the density control value) such as a charging potential of a drum and an exposure intensity with respect to a photosensitive drum.
Japanese Patent Application Laid-Open No. 2004-228867 discloses image formation for controlling the fixing temperature of a fixing device and the conveyance speed of a recording material in the fixing device based on a gloss value (glossiness) after heat fixing of a test image (corresponding to the patch image). The device is shown.
Further, Patent Document 3 discloses a sensor that simultaneously detects scattered light and specularly reflected light irradiated on an image.
JP 2001-194443 A JP 11-119484 A JP-A-9-218097

However, when image density adjustment (control) and glossiness adjustment (control) are performed independently, there are the following problems.
That is, the density control value used for adjusting the image density is a parameter that mainly controls the amount of toner attached to the photosensitive drum during development. If the amount of toner attached changes for image density adjustment, the change occurs. Since the glossiness is also affected, there is a problem that the glossiness must be readjusted. Further, if the glossiness is adjusted after the image density is adjusted first, the time required for these adjustments becomes long, and there is a problem that time, power, and toner used are wasted and not efficient.
Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image forming apparatus capable of efficiently and appropriately adjusting the density and glossiness of an output image and a method for setting control values thereof. There is to do.

In order to achieve the above object, the present invention forms a toner image on an image carrier, typically a photosensitive drum, and the toner image is directly or via an intermediate transfer material such as an intermediate belt. The present invention is applied as an image forming apparatus for transferring a toner image to a predetermined recording material and heat-fixing the toner image on the recording material, or a method for setting control parameter setting values (control values) in such an image forming apparatus. A predetermined one or a plurality of test toner images (so-called patch images) are formed on the image carrier, and further transferred to the recording material and heat-fixed, while before or after heat-fixing Based on the detection result of the density detecting means for detecting the density of the test toner image, a density control value that is a parameter setting value used for toner image density control is set. Based on the detection result of the gloss detecting means for detecting the gloss of the test toner image and the density control value set as described above, a gloss control value which is a set value of a parameter used for gloss control of the toner image is obtained. It is to set.
Here, as the density control value, for example, a setting value of a developing bias potential, a setting value of a charging potential of the image carrier, an exposure intensity for the image carrier (exposure intensity for electrostatic latent image writing or static elimination) 1 of the set value of the ratio of the peripheral speed of the rotating image carrier and the peripheral speed of the developing roller rotating in opposition thereto (so-called peripheral speed ratio). A thing including plural is conceivable.
Further, as the gloss control value, for example, a value including one or both of a set value of the temperature of heat fixing and a set value of the conveyance speed of the recording material when the heat fixing is performed can be considered.
In this way, first, the setting of the density control value (adjustment of image density) is preferentially performed based on the detected density from the test toner image (patch image), and then the detection from the test toner image is performed. By setting the gloss control value (adjustment of the glossiness of the image) in consideration of the setting result of the density control value in addition to the gloss level, the number of times of output of the test toner image is suppressed to a small number (less) Once), both image density and glossiness can be adjusted efficiently and appropriately.

Further, as the test toner image formed at one time, a plurality of toner images are formed under conditions in which the density control value is set differently, and the density is determined based on the density detection result for each of the test toner images. By setting the control value, it is possible to grasp the correspondence relationship of the actual toner image density change with respect to the change (change) of the density control value. Therefore, rather than using the same correspondence relationship set in advance, Highly accurate density adjustment (setting of density control value) according to environmental changes becomes possible.
When a plurality of test toner images are output, a more specific example of the gloss control value setting method is to set (adjust) the test toner image from the plurality of test toner images. The test toner image formed with the density control value setting state that matches or is closest to the density control value is selected, and the gloss control value is determined based on the gloss level detection result for the test toner image. Can be set.
As another specific example of the method for setting the gloss control value, the density control is performed based on the detection result of the gloss level of the test toner image and the density control value set (adjusted) previously. It is conceivable to estimate the detection result of the test toner image when a value (a previously adjusted density control value) is set, and to set the gloss control value based on the estimation result.
In any of these specific examples, the gloss control value is set in consideration of the setting result of the density control value. Therefore, both the density and the glossiness of the image are reduced while suppressing the number of times of output of the test toner image. It becomes possible to adjust efficiently and appropriately.

By the way, in general, when a recording material (recording paper or the like) is passed through a heating roller (so-called fixing roller) that contacts and heats the toner image on the recording material, the heat held by the heating roller is transmitted to the recording material side. As a result, the temperature of the heating roller (generally, the surface temperature) drops rapidly. The temperature drop is most significant from the start of contact of the first recording material to the heating roller until the heating roller makes one revolution. From the second week onward, the temperature control of the heating roller is significant. Follows and the temperature is relatively stable. Therefore, it is not appropriate to perform density adjustment or glossiness adjustment based on the test toner image that has been heat-fixed in a state where the temperature drop is abrupt and unstable.
Therefore, the test toner image is formed in a region (region on the rear end side in the transport direction) excluding a region corresponding to a substantially circumferential length of the heating roller used for the heat fixing from the front end in the transport direction of the recording material. Is preferred.
Thus, appropriate density adjustment (when detecting the density of the toner image after heat fixing) and glossiness adjustment are performed based on the test toner image that has been heat-fixed in a relatively stable temperature state.

A re-conveying means for re-conveying the recording material on which the toner image has been heat-fixed to a detection position of the density detecting means for detecting the density of the toner image on the recording material before the heat-fixing; And detecting the intensity (light quantity) of scattered light and the intensity (light quantity) of specularly reflected light on the toner image on the recording material by the density detection means, and based on those intensities of the toner image If the density is detected, and the gloss of the toner image is detected based on the detected intensity of the regular reflection light, the density detection means can also be used as the gloss detection means, so that the number of sensors can be reduced. This is preferable. In particular, in an image forming apparatus equipped with a double-sided image forming means (so-called double-sided printing function) that sequentially forms toner images on both sides of the sheet-like recording material, the recording material after heat fixing is turned back to the image transfer unit. Since the re-conveying means is provided, it is preferable that various conveying means for realizing the double-sided printing function can be used only by providing means for switching between the state where the recording material is turned back and the state where the recording material is not turned back.
In the case where the double-sided image forming means is provided, when there is a predetermined image formation request, first, the test toner image is formed on one side (back side) of the recording material and the density control value is set. After setting and setting of the gloss control value, it is conceivable to perform image formation based on the image formation request on the other surface (front surface) of the recording material.
This makes it possible to perform density adjustment and glossiness adjustment by effectively utilizing the back side of the recording material on which an image corresponding to the image formation request is formed, and before the original image corresponding to the image formation request is formed, Since the test toner image is formed and the density and glossiness are adjusted, appropriate density adjustment and the like can be performed without being affected by the density of the back image (image according to the image formation request).

According to the present invention, after setting the density control value (adjusting the image density) preferentially based on the detected density from the test toner image, in addition to the detected glossiness from the test toner image Since the gloss control value is set (adjustment of the glossiness of the image) in consideration of the setting result of the density control value, the number of times of outputting the test toner image is suppressed to a small number (one time if it is small). Both density and glossiness of the image can be adjusted efficiently and appropriately.
Further, the test toner image is formed in a region (region on the rear end side in the transport direction) excluding a region corresponding to a substantially circumferential length of the heating roller used for heat fixing from the front end in the transport direction of the recording material. Thus, based on the test toner image that has been heat-fixed at a relatively stable fixing temperature, the density is adjusted (without being affected by unstable fixing temperature) (the toner image density after heat-fixing is adjusted). Detection) and glossiness adjustment.
Further, there is provided means for re-transporting the recording material on which the toner image has been heat-fixed to a detection position of a density detecting means for detecting the density of the toner image on the recording material before the heat-fixing has been performed, If the means is also used as a glossiness detecting means, the number of sensor points can be reduced, which is preferable.
In the case where the double-sided image forming means is provided, when there is a predetermined image forming request, first, the test toner image is formed on one side (back side) of the recording material to set the density control value and If the image formation based on the image formation request is performed on the other surface (front surface) after setting the gloss control value, the back surface of the recording material can be used effectively, and the test is performed first. Since the toner image is formed and the density and glossiness are adjusted, the density can be adjusted with high accuracy without being affected by the density of the back image (image according to the image formation request).

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
FIG. 1 is a schematic sectional view of the image forming apparatus A according to the embodiment of the present invention, FIG. 2 is a flowchart showing a procedure of control value setting processing relating to image density and glossiness in the image forming apparatus A, and FIG. 6 is an explanatory diagram regarding control value setting processing regarding density and glossiness in the image processing apparatus A. FIG.

First, the configuration and the like of the image forming apparatus A according to the embodiment of the present invention will be described using the schematic cross-sectional view of FIG.
The image forming apparatus A includes an image forming unit or a color forming a color copying machine that forms a multicolor or single color image on a recording sheet (recording material) such as paper according to image data input from the outside. A printer or the like. Of course, the image forming apparatus A is not limited to a color printer or the like, and may be, for example, a printer or a copier that forms an image of only a single color. In this embodiment, the image forming apparatus A uses black (K) for magenta (M), cyan (C), and yellow (Y), which are three subtractive primary colors obtained by color separation of a color image. A description will be given of a tandem color printer that forms an image using image data corresponding to each of the four color components (hues) added.
As shown below, the image forming apparatus A forms toner images on the photosensitive drums 3a to 3d (an example of an image carrier), and the toner image is transferred to an intermediate transfer belt 7 (an example of an intermediate transfer material). An electrophotographic image forming apparatus that transfers the toner image to a recording material such as paper and heat-fixes the toner image on the recording material.
As shown in FIG. 1, the image forming apparatus A includes an exposure unit 1, development units 2a to 2d (generally 2), photosensitive drums 3a to 3d (generally 3), and cleaner units 4a to 4d (generic name). 4), chargers 5a to 5d (collectively 5), intermediate transfer rollers 6a to 6d (collectively 6), intermediate transfer belt unit 8, first to third transport paths R1 to R3, paper feed tray 10, a static eliminator 13, a fixing device 12, a registration roller 14, a paper discharge tray 15, a pickup roller 16, transport rollers 25-1 to 25-8 (collectively 25), and the like.
The image forming apparatus A further includes a storage unit (such as an EEPROM) that stores a program for executing control of the image forming process and setting processing of various control parameters, setting values of various control parameters (hereinafter referred to as control values), and the like. (Not shown), and a control unit (not shown) that includes a CPU, a RAM, and other peripheral devices and executes the program. Control value setting processing relating to image density and gloss level control, which will be described later, is performed by executing a predetermined program by the control unit.
The developing unit 2, the photosensitive drum 3, the cleaner unit 4, the charger 5, and the intermediate transfer roller 6 are provided in four units according to each color component, and black, cyan, magenta, Toner cartridges 40a to 40d (collectively referred to as 40) containing toners corresponding to yellow color components are respectively mounted to constitute four image forming portions Pa to Pd (collectively referred to as P). Each of these image forming portions P is sequentially arranged in a row from the most upstream side in the transport direction B (arrow B in the figure) of the intermediate transfer belt 7 to the downstream, and black, cyan, magenta, and yellow toners. The visible image is developed on the intermediate transfer belt 7.

Here, the charger 5 is a charging means for uniformly charging the surface of the photosensitive drum 3 to a predetermined potential. The exposure unit 1 transfers the charged photosensitive drum 3 to an external device. By exposing according to image data transmitted from a computer or the like or test image data (patch image data) generated by the control unit, the surface of the photosensitive drum 3 is electrostatically charged according to the image data. An apparatus for forming a latent image. The exposure unit 1 can be configured by a laser scanning unit (LSU) provided with a laser irradiation unit and a reflection mirror, or an EL or LED writing head in which light emitting elements are arranged in an array.
Each of the developing units 2 stores toner of each color of black, cyan, magenta and yellow supplied from each of the toner cartridges 40, and each color latent image formed on each of the photosensitive drums 3 is used as a toner image. Visualize (develop). The cleaner unit 4 removes and collects toner remaining on the surface of the photosensitive drum 3 after development and image transfer.
The intermediate transfer belt unit 8 is stretched between an intermediate transfer belt drive roller 71, an intermediate transfer belt driven roller 72, and between the intermediate transfer belt drive roller 71 and the intermediate transfer belt driven roller 72, and on the loop. An intermediate transfer belt 7 that forms a moving path, and the tension of the intermediate transfer belt 7 is adjusted to be constant by an intermediate transfer belt tension mechanism (not shown). The intermediate transfer belt drive roller 71 is rotationally driven, so that the intermediate transfer belt 7 is rotationally driven in the arrow B direction. The outer peripheral surface of the intermediate transfer belt 7 faces each of the photosensitive drums 3, and each of the intermediate transfer rollers 6 is disposed at a position facing each of the photosensitive drums 3 across the intermediate transfer belt 7. Yes. The intermediate transfer belt 7 is formed in an endless shape using, for example, a film having a thickness of about 100 μm to 150 μm.

On the other hand, the sheet feeding tray 10 accommodates a sheet-like recording material such as a sheet used for image formation, and the sheet discharge tray 15 provided at the upper part of the image forming apparatus A prints (images). This tray is a discharge destination of the recording material that has been formed.
The recording material stored in the paper feed tray 10 is conveyed by the conveying roller 25, the pickup roller 16, the registration roller 14, the transfer belt unit 8, the fixing device 12 and the like for promoting and assisting the conveyance. The first transport path R1 is transported via the transfer belt unit 8 and the fixing device 12, and is discharged to a paper discharge tray 15. Here, since the recording material being conveyed by the transfer belt 7 is electrostatically attracted to the intermediate transfer belt 7, it is separated from the intermediate transfer belt 7 by the static eliminator 13 to which an alternating current is applied. Guided to the fixing device 12.
The intermediate transfer roller 6 transfers the toner image on the photosensitive drum 3 onto the recording material when the recording material is conveyed by the transfer belt 7 and to the intermediate transfer belt when the recording material is not conveyed. 7, a high-voltage transfer bias (a high voltage having a polarity (+) opposite to the charging polarity (−) of the toner) is applied. As a result, the toner images of the respective colors formed on the respective photosensitive drums 3 are sequentially transferred onto the recording material on the intermediate transfer belt 7 or the outer peripheral surface of the intermediate transfer belt 7 and input from the outside. An image corresponding to the image data or the test image data generated by the control unit is formed.
The image density and glossiness of the image formed on the recording material or the intermediate transfer belt 7 in this way are detected by the reflected light detection sensor Sn1 disposed in the vicinity of the intermediate transfer belt drive roller 71.
The reflected light detection sensor Sn1 includes one light source and two light receiving elements as in the sensor disclosed in Patent Document 3, for example, and the intensity (scattered reflected light) intensity of light irradiated on the toner image from the light source ( Light intensity) is detected by one light receiving element, the intensity of specular reflection light is detected by the other light receiving element, the density of the toner image is detected based on at least the intensity of the detected scattered light, and the detected regular reflection is further detected. The glossiness of the patch image is detected based on the light intensity. Thereby, the reflected light detection sensor Sn1 serves as both a density detection sensor (density detection means) and a glossiness detection sensor (gloss detection means).
Here, for example, the density of the image is obtained by using a value obtained based on the ratio of the intensity of the irradiation light and the intensity of the scattered light as an index, or, as disclosed in Patent Document 1, the scattered light. A value (for example, a difference) obtained by combining the intensity of the light and the intensity of the regular reflection light may be used as an index.
In general, the lower the intensity of the scattered light, the higher the density, and the higher the intensity of the regular reflection light, the higher the glossiness.
The fixing device 12 is a device that heat-fixes the toner image on the recording material by heating and pressing, and includes a heating roller 12-1 and a pressure roller 12-2. The heating roller 12-1 is controlled to have a predetermined fixing temperature by the control unit based on a signal from a temperature detector (not shown).
The toner adhering to the intermediate transfer belt 7 is removed and collected by an intermediate transfer belt cleaning unit 9 provided with a cleaning blade or the like that contacts the intermediate transfer belt 7 and peels off the adhering toner.

Further, the image forming apparatus A can perform double-sided printing on a sheet-like recording material. During double-sided printing, the recording material transport path after passing through the fixing device 12 is used for discharging the recording material from the fixing device 12. The recording material that is switched to the second transport path by the path switching claw 24-1 provided in the path to the transport roller 25-3 and transported to the second transport path by the transport roller 25-6 is the transport roller. It is turned back by the reverse rotation of 25-6 and the operation of the path switching claw 24-3 and guided to the third transport path R. The recording material is again guided to the first transport path R1 by transport rollers 25-7 and 25-8 disposed along the third transport path R3. At this time, the recording material is guided to the first transport path R1 in a state where the front and back surfaces and the front and rear ends are reversed by the turnback, so that the recording material is printed on the surface opposite to the surface on which the printing is first performed.
Further, in this image forming apparatus A, the operation of the path switching claw 24-1 and the other path switching claw 24-2 allows the recording material after heating and fixing to pass through the third transport path R2 without passing through the second transport path R2. It is also possible to guide directly to the transport path and guide to the first transport path R1 without turnback.
The exposure unit 1, the image forming portion P, the intermediate transfer belt unit 8, the fixing device 12, the path switching claws 24-1, 24-3, the first to third transport paths R1, R2, R3. In addition, an example of a double-sided image forming unit that sequentially forms toner images on both sides of a sheet-like recording material is configured by a conveyance roller or the like provided in each path.
Further, the recording material on which the toner image is heated and fixed is heated by the path switching claws 24-1, 24-2, 24-3, the third transport path R3, and transport rollers provided in the transport path. An example of a re-conveying unit that re-conveys to a detection position of the reflected light detection sensor Sn1 (an example of a density detecting unit) that detects the density of the toner image on the recording material before fixing is configured.

Next, the procedure of control value setting processing relating to image density and glossiness in the image forming apparatus A will be described using the flowchart shown in FIG. The process shown in FIG. 2 is performed when the control unit executes a predetermined control program.
<Steps S1, S2>
First, the control unit monitors whether or not there is a predetermined print request (image formation request) from an external computer or the like (S1), and when there is a print request, control values relating to the density and glossiness of the image. It is determined whether or not the setting (adjustment) process is to be performed (hereinafter referred to as a density adjustment necessary state) (S2).
Here, whether or not the density adjustment is necessary is determined based on, for example, whether or not an input indicating that the adjustment processing is to be performed is made in advance from an operation unit such as a push button provided in the image forming apparatus A. Alternatively, the determination is made based on whether or not the past cumulative number of image formations has reached a predetermined number of times.
When it is determined that the density adjustment is not necessary, the control unit controls the image forming unit P to form an image according to the print request on one surface of the recording material (sheet). Then, heat fixing is executed, the recording material is discharged to the paper discharge tray 15, and the process is terminated (S14).
Note that the development conditions such as the development bias potential and the fixing conditions such as the fixing temperature at this time are the latest setting conditions stored in the storage unit at that time.

On the other hand, when it is determined that the density adjustment is necessary, the control unit controls the image forming unit such as the image forming unit P and the pickup roller 16 to perform steps S3 to S5 described below. In the procedure, a plurality of patch images, which are predetermined test toner images, are formed on the photosensitive drum 3, transferred to a recording material, and heated and fixed (an example of a test toner image forming unit). The plurality of patch images may be images having the same predetermined intermediate gradation level, but are usually all solid images.
<Step S3>
That is, first, the control unit reads a predetermined development condition from the storage unit, and, according to the condition, a plurality of predetermined patches on one surface (first surface) of the recording material (sheet). The images (test images) are formed side by side in the recording material conveyance direction (sub-scanning direction) (S3).
Here, the plurality of patch images are formed in a state where density control values, which are parameter setting values used for toner image density control, are set to different predetermined values. However, other development conditions are the same.
Further, as the density control value, for example, a setting value of the developing bias potential in the developing unit 2 (developing device), a setting value of the charging potential of the photosensitive drum 3 (image carrier) in the charging device 5, A setting value (exposure intensity as a base) of the exposure intensity for the photosensitive drum 3 in the exposure unit 1, a peripheral speed of the rotating photosensitive drum 3, and a developing roller that rotates in opposition thereto (the developing unit 2 includes). A set value of the peripheral speed ratio (circumferential speed ratio) of the roller) can be considered. These are all parameters that affect the amount of toner attached to the photosensitive drum 3. When these parameters are changed, the amount of toner attached changes, resulting in a change in image density. In the present embodiment, the developing bias potential (hereinafter simply referred to as developing bias) is used as the control value.
In addition, the control unit is configured so that the patch image is a remaining area (after the conveyance direction) of the recording material (sheet) from the front end in the conveyance direction except for an area corresponding to the circumferential length of the heating roller 12-1. Patch image data is generated so as to be formed in the edge region.
Accordingly, it is possible to appropriately adjust the glossiness in the processing of steps S10 and S11 described later, based on the patch image that has been heat-fixed in a relatively stable temperature state.

<Steps S4 and S5>
Next, the control unit detects the density of the toner image on the recording material (patch image) by the reflected light detection sensor Sn1 (an example of density detecting means) that detects the density of the patch image (test toner image) before heat fixing. (Concentration) is detected, and the detection result is acquired (S4).
Further, the control unit controls the fixing device 12 so that the temperature setting value of the heating roller 12-1 in the fixing device 12 is set to a reference fixing temperature as a predetermined reference. The toner image is heated and fixed on the recording material (S5).
Here, the fixing condition in the fixing device 12 greatly affects the glossiness of the image after fixing on the recording material.
In general, in a state where a toner image having a sufficient density is transferred to a recording material, the glossiness increases as the heat fixing temperature (temperature of the heating roller 12-1) in the fixing device 12 increases, and the fixing device 12 increases. The glossiness increases as the recording material conveyance speed is lowered when heat fixing is performed.
That is, as a parameter setting value (hereinafter referred to as gloss control value) used for gloss control of the toner image on the recording material after heat fixing, the heat fixing set temperature in the fixing device 12 or the heating in the fixing device 12 is used. A set value of the recording material conveyance speed (rotation speed of the heating roller 12-1) when fixing is considered. In the present embodiment, a set value of a heat fixing temperature (hereinafter referred to as a fixing temperature) is used as the gloss control value.
<Steps S6 and S7>
Next, the control unit controls the path switching claws 24-1 and 24-2 to turn the recording material after the heat fixing is performed from the third transport path R3 without turning back the recording material. The recording material is circulated and conveyed by the development to the conveying path R1 (S6). As a result, the recording material on which the toner image has been heat-fixed is positioned at the detection position of the reflected light detection sensor Sn1 (an example of the density detection means) that detects the density of the toner image on the recording material before the heat-fixing. Re-conveyed. However, image formation on the recording material is not performed during the re-conveyance.
The control unit detects the toner image on the recording material by the reflected light detection sensor Sn1 (an example of the glossiness detection unit) that detects the density of the patch image (test toner image) after being heated and fixed at the reference fixing temperature. Glossiness (patch image glossiness) is detected, and the detection result is acquired (S7).

Further, the control unit performs the processing in steps S8 and S9 described below, based on the density of each of the plurality of patch images detected by the reflected light detection sensor Sn1 (an example of the detection result of the density detection unit). Development bias (an example of density control value) is set (adjusted) (an example of density control value setting means).
That is, the control unit first determines the relationship between the development bias and the image density based on the values of the development bias set as the development conditions of the patch image and the density of the patch image actually obtained for each value. An expression is derived (S8).
The graph indicated by a solid line in FIG. 3A outputs three types of patch images under the three development bias conditions Vb1, Vb1, and Vb3, and the patch image densities I1, I2, and I3 are determined from the patch images. When obtained, a line graph representing a relational expression between the developing bias Vb and the image density I when representing them by a combination of line formats (that is, a line) is shown.
In order to derive this relational expression, in addition to the polygonal line approximation as shown in FIG. 3A, each relational expression between the developing bias Vb and the image density I is obtained in advance by experiments or the like, and the coefficient is set as an unknown number. It is also conceivable to obtain the coefficient of the relational expression by a predetermined approximate calculation so that the error when applying the density Ii obtained from the image is minimized. Further, if one coefficient is set as an unknown, the relational expression can be obtained from one patch image.
<Step S9>
Next, the control unit sets the target image density Is as the content of the patch image (for example, as a solid image) based on the relational expression between the developing bias Vb and the image density I obtained in step S8. The developing bias Vbs necessary for obtaining is obtained, and this is set as the developing bias value and stored in the storage unit (S9).
In subsequent image formation, the developing bias Vbs is set (controlled) as a target potential of the developing bias potential in the developing unit 2.

Next, the control unit performs the following steps S10 and S11 to detect the patch image glossiness by the reflected light detection sensor Sn1, and steps S8 and S9 (an example of processing of the density control value setting means). Based on the set developing bias setting value Vbs (an example of density control value), the fixing temperature setting value Ts (an example of a gloss control value that is a parameter setting value used for gloss control of a toner image) is obtained. Set (an example of gloss control value setting means).
<Step 10>
That is, the control unit first detects the gloss level detected from each of the plurality of patch images by the reflected light detection sensor Sn1 (an example of the gloss detection unit) and the process of step S9 (the process of the density control value setting unit). Based on the developing bias setting value Vbs (an example of the density control value) set in (Example), the glossiness estimation value Gx when the developing bias setting value Vbs is set is obtained (S10, Glossy). Estimation of the detection result of the detection means).
More specifically, based on each value of the development bias set as the development condition of the patch image and the glossiness of the patch image actually obtained for each, a relational expression between the development bias and the glossiness is obtained. The glossiness estimation value Gx is obtained by applying the developing bias setting value Vbs set in step S9 to the relational expression.
The graph indicated by the solid line in FIG. 3B outputs three types of patch images under the three development bias conditions Vb1, Vb1, and Vb3, and the glossiness G1, G2, and G3 are obtained from the patch images. In this case, a line graph representing a relational expression between the developing bias Vb and the glossiness G when the values are approximated by a combination of line formats (that is, a broken line) is shown. If the developing bias set value Vbs is applied to this relational expression, the glossiness estimation value Gx is obtained.
As in the case of concentration, each relational expression can be derived by preparing a relational expression with a coefficient as an unknown in advance in addition to the polygonal line approximation and obtaining the coefficient of the relational expression by a predetermined approximation calculation. .

<Step 11>
Next, the control unit sets a setting value (an example of gloss control value) of the fixing temperature based on the glossiness estimation value Gx (estimation result) obtained in step S10, and sends it to the storage unit. Store (S11).
More specifically, for example, as in the solid line graph shown in FIG. 3C, for a patch image that satisfies the target density, the fixing temperature (an example of the gloss control value) is a value (here, a value used when the patch image is formed). , A relational expression or relation table between the fixing temperature and the glossiness when changed within a predetermined control range including the reference fixing temperature Tm3) is stored in advance, and the relational expression or relation table is used to estimate the glossiness. Correction is performed based on the value Gx.
The broken line graph shown in FIG. 3C is an example in which the solid line graph representing the relational expression or relation table is corrected according to the difference between the glossiness Gm3 corresponding to the reference fixing temperature Tm3 and the glossiness estimation value Gx. Represents.
As a result, the gap between the apparatus condition when the relational expression or the relation table is determined and the current condition of the image forming apparatus A is corrected, and the corrected relational expression or relation table is stored in the image forming apparatus A. The relationship between the present fixing temperature T and the glossiness G is expressed with higher accuracy.
The control unit obtains the fixing temperature Ts necessary for obtaining the target glossiness Gs as the contents of the patch image (for example, as a solid image) in the corrected relational expression or relation table. This is the set value of the fixing temperature.
In the subsequent image formation, the fixing temperature Ts is set (controlled) as a heating target temperature in the fixing device 12.
The relational expression or the relational table may be corrected by other methods such as the difference between the glossiness Gm3 corresponding to the reference fixing temperature Tm3 and the glossiness estimation value Gx, or their ratio. It is done.

<Steps S12 and S13>
Next, the control unit controls the path switching claws 24-1, 24-2, 24-3 and the respective transport rollers to thereby apply the recording material (sheet) after the patch image is heated and fixed to the recording material (sheet). After being guided to the second transport path R2 and being turned back, it is guided again to the first transport path R1 through the third transport path R3 (S12).
Finally, the control unit controls the image forming means such as the image forming unit P and the pickup roller 16 to thereby provide the other side of the recording material (sheet) (the back side of the side on which the patch image is formed). Then, image formation and heat fixing are executed according to the print request, the recording material is discharged to the paper discharge tray 15, and the process is terminated (S13). It is also conceivable that the processing in steps S3 to S11 is repeated until the target image density and glossiness are obtained.
As described above, the image forming apparatus A first sets the density control value (development bias, etc.) preferentially based on the detected density from the patch image (test toner image) ( In S8, S9), the gloss control value (fixing temperature, etc.) is set taking into account the setting result of the density control value (development bias, etc.) in addition to the detected glossiness from the patch image (S10, S11). Thus, it is possible to efficiently and appropriately adjust both the density and the glossiness of the image while suppressing the number of times of outputting the patch image to a small number (one time if it is small).
Further, the recording material on which the toner image has been heat-fixed is re-conveyed to the detection position of the sensor for detecting the density and the glossiness of the image on the recording material before the heat-fixing is performed (S6). Therefore, the density detection sensor and the glossiness detection sensor are used in combination, and the number of sensors can be reduced.
Further, in the image forming apparatus A provided with the double-sided image forming means, when there is a print request (image formation request) by the control section, recording by the image forming section P or the like (an example of a test toner image forming means). Patch image formation on one side of the material (S3), development bias (example of density control value) setting (S8, S9), and fixing temperature (example of gloss control value) setting (S10, S11) are executed After that, the image formation (S13) based on the print request on the other side of the recording material is controlled to be executed (an example of the image forming order control means). Adjustment and gloss adjustment can be performed. At that time, since the patch image is formed and the density and glossiness are adjusted first, appropriate density adjustment is performed without being affected by the density of the back image (image according to the image formation request). It is possible.

In the embodiment described above, the glossiness when the set value is set is estimated based on the glossiness of the patch image and the adjusted setting value of the developing bias (S10), and based on the estimation result, the glossiness is estimated. Although the set value of the fixing temperature is set, it is not limited to this.
For example, in FIG. 2, the setting state of the developing bias that coincides with or is closest to the developing bias setting value Vbs set by the processing in step S9 (processing of the density control value setting unit) by the control unit (example in FIG. 3). Then, it is conceivable to select a patch image formed at Vb2) and set the fixing temperature setting value Ts based on the glossiness detection result (G2 in the example of FIG. 3) for the patch image.
In the example of FIG. 3, if the glossiness detection value G2 is used instead of the glossiness estimation value Gx, the fixing temperature setting value Ts can be set.
Also by such processing, the density control value and the gloss control value can be set with relatively high accuracy.
In the above-described embodiment, the developing bias potential is used as the density control value and the fixing temperature is used as the gloss control value. However, a combination of a plurality of control parameters may be used as the density control value and the gloss control value. Conceivable. For example, for each of the density control value and the gloss control value, one index is provided to represent them, and the index value is set based on the patch image density. If the index value is determined, a plurality of control values are set. Predetermined formulas and data tables that determine the values (developing bias potential and exposure intensity for the density control value, fixing temperature and fixing speed (recording material conveyance speed) for the gloss control value, etc.) It is possible to keep things.

In the above-described embodiment, when the print request (image formation request) is met, the image and the patch image based on the print request are printed on both sides, and the density control value and the gloss control value are set. Although an example has been described, the present invention is not limited to this, and it may be possible to perform patch image formation, density control value, and gloss control value setting processing at a predetermined timing. Further, it may be possible to select which one to perform by setting from a predetermined operation unit.
In the above-described embodiment, an example in which the sensor for detecting density and the center for detecting glossiness are combined has been described. For example, the image forming apparatus A has a post-heating fixing unit on the rear side of the fixing device 12. By separately providing the reflected light detection sensor (same as the sensor Sn1) for detecting the glossiness of the patch image, the density of the patch image is measured on the front side of the fixing device 12, and the glossiness is shown on the rear side. It is also conceivable to provide both sensors separately for detection. In this case, it is not necessary to return the recording material after heat fixing and transport it again.
In the above-described embodiment, the example in which the reflected light detection sensor Sn1 that serves both as a density detection sensor and a glossiness detection center is arranged in the front stage of the fixing device 12 has been described. Alternatively, the reflected light detection sensor Sn1 may be arranged in the conveyance path downstream of the fixing device 12 so that the density and glossiness of the patch image after heating and fixing are detected. This also eliminates the need for returning and re-conveying the recording material after heat fixing. However, when the reflected light detection sensor Sn1 facing the intermediate transfer belt 7 is not provided, a patch image is formed not on the recording material but on the intermediate transfer belt 7 itself, and the density or the like is detected to detect the development density or the like. It is impossible to adjust the developing density that has been conventionally performed, such as adjustment.

  The present invention can be used for an image forming apparatus.

1 is a schematic sectional view of an image forming apparatus A according to an embodiment of the present invention. 6 is a flowchart showing a procedure of control value setting processing relating to image density and glossiness in image forming apparatus A. FIG. 5 is an explanatory diagram regarding control value setting processing regarding density and glossiness in the image processing apparatus A.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Exposure unit 2a-2d ... Developing unit 3a-3d ... Photoconductor drum 4a-4d ... Cleaner unit 5a-5d ... Charger 7 ... Intermediate transfer belt 8 ... Intermediate transfer belt unit 10 ... Paper feed tray 12 ... Fixing device 15 Sheet discharge trays 24-1, 24-2, 24-3 ... Path switching claw Sn1 ... Reflected light detection sensors R1, R2, R3 ... Recording material conveyance paths S1, S2, ... Processing procedure (step)

Claims (10)

An image forming apparatus that forms a toner image on an image carrier, transfers the toner image to a predetermined recording material directly or via an intermediate transfer material, and further heat-fixes the toner image on the recording material,
Test toner image forming means for forming a predetermined one or a plurality of test toner images on the image carrier, transferring to the recording material, and heat fixing;
Density detecting means for detecting the density of the test toner image before or after the heat fixing;
Gloss detecting means for detecting the gloss of the test toner image after the heat fixing;
Density control value setting means for setting a density control value that is a parameter setting value used for density control of the toner image based on the detection result of the density detection means;
Gloss control value setting for setting a gloss control value, which is a parameter setting value used for gloss control of the toner image, based on the detection result of the gloss detection means and the density control value set by the density control value setting means Means,
An image forming apparatus comprising: The test toner image forming means forms a plurality of the test toner images having different setting states of the density control values;
The image forming apparatus according to claim 1, wherein the density value setting unit sets the density control value based on a detection result of the density detection unit for each of the plurality of test toner images.   The gloss control value setting means is formed in a setting state of the density control value that matches or is closest to the density control value set by the density control value setting means from among the plurality of test toner images. The image forming apparatus according to claim 2, wherein a test toner image is selected, and the gloss control value is set based on a detection result of the gloss detection unit for the test toner image.   Detection result of the gloss detection unit when the gloss control value is set based on the detection result of the gloss detection unit and the density control value set by the density control value setting unit. The image forming apparatus according to claim 1, wherein the gloss control value is set based on a result of the estimation.   The test toner image forming means forms the test toner image in an area excluding an area corresponding to a substantially circumferential length of a heating roller used for the heating and fixing from the leading end in the conveying direction of the recording material. The image forming apparatus according to any one of 1 to 4. Reconveying means for reconveying the recording material on which the toner image has been heat-fixed to a detection position of the density detecting means for detecting the density of the toner image on the recording material before the heat-fixing is performed. Comprising
The density detecting means detects the intensity of scattered light and the intensity of specularly reflected light irradiated on the toner image, detects the density of the toner image based on at least the detected intensity of the scattered light, and further detects The image forming apparatus according to claim 1, which is also used as the gloss detecting unit by detecting the gloss based on the intensity of the regular reflection light. Double-sided image forming means for sequentially forming toner images on both sides of the sheet-like recording material;
When there is a predetermined image formation request, the test toner image forming unit forms the test toner image on one surface of the recording material, the density control value setting unit sets the density control value, and Image formation for controlling the double-sided image forming means to perform image formation based on the image forming request on the other surface of the recording material after the gloss control value is set by the gloss control value setting means. Order control means;
An image forming apparatus according to claim 1, comprising:   The density control value is a developing bias potential setting value, a charging potential setting value of the image carrier, an exposure intensity setting value for the image carrier, a peripheral speed of the rotating image carrier, and the rotation speed of the image bearing member. The image forming apparatus according to claim 1, wherein the image forming apparatus includes one or a plurality of set values of a ratio of peripheral speeds of the developing rollers.   The image according to any one of claims 1 to 8, wherein the gloss control value includes a set value of a temperature of the heat fixing and / or a set value of a conveyance speed of the recording material when the heat fixing is performed. Forming equipment. A control value of an image forming apparatus that forms a toner image on an image carrier, transfers the toner image to a predetermined recording material directly or via an intermediate transfer material, and further heat-fixes the toner image on the recording material. A setting method,
A test toner image forming step for forming predetermined one or a plurality of test toner images on the image carrier, transferring to the recording material, and heat fixing;
A density control value for setting a density control value, which is a parameter setting value used for density control of the toner image, based on the detection result of the density detection means for detecting the density of the test toner image before or after the heat fixing. A setting process;
Parameters used for gloss control of the toner image based on the detection result of the gloss detection means for detecting the gloss of the test toner image after the heat fixing and the density control value set by the density control value setting means A gloss control value setting process for setting a gloss control value which is a set value of
A control value setting method for an image forming apparatus, comprising:

Images