JP2002062713A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device, capable of automatically setting optimum secondary transfer electric field to a recording medium to be used. SOLUTION: This image forming device is equipped with a test pattern image forming means 84 for forming a monochrome test pattern image and a plural-color test pattern image on an intermediate transfer body 21, a transfer electric field control means 83 for controlling transfer electric field intensity, so that the transfer electric field strength is changed over a prescribed electric field strength range in the case of secondarily transferring the monochrome test pattern image and the plural-color test pattern image on the transfer body 21 to the recording medium P, a fixed image density sensor 90 for measuring the density of the monochrome test pattern image and the plural-color test pattern image transferred secondarily and fixed on the medium P by the transfer electric field controlled by the control means 83, and a transfer electric field strength deciding means 82 deciding the intensity of the transfer electric field, when secondarily transferring a toner image on the transfer body 21 to the medium P, based on the result of measuring the density.

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 used for an electrophotographic copying machine, a printer, and the like.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus used for an electrophotographic copying machine or a printer, electrostatic latent images corresponding to different colors are formed on a plurality of photosensitive drums, respectively. The image is developed with toner of each color to form a toner image of each color on each image carrier, and the toner images of each color are sequentially superimposed on an intermediate transfer belt rotating in a predetermined direction so as to be primary. 2. Description of the Related Art A so-called intermediate transfer type color image forming apparatus is known in which an image is recorded on a recording medium by transferring and fixing the primary-transferred toner image to a predetermined recording medium.

FIG. 6 is a diagram showing a schematic configuration of a conventional intermediate transfer type color image forming apparatus.

As shown in FIG. 6, this image forming apparatus includes, for example, four photosensitive drums 11 corresponding to yellow (Y), magenta (M), cyan (C) and black (K), respectively. Four charging devices 12 for uniformly charging the surface of each photoconductor drum 11 and four charging devices 12 for irradiating the surface of each photoconductor drum with exposure light based on image information corresponding to each color to form an electrostatic latent image Exposure device 13, four developing devices 14 for developing the electrostatic latent images formed on the respective photosensitive drums with toners of the respective colors, four photosensitive member cleaners 15 for cleaning the surfaces of respective photosensitive drums 11, and respective photosensitive members A belt-shaped intermediate transfer member 21 arranged so as to be in contact with the surface of the drum 11 and rotating in the direction of arrow B; a driving roll 22 for driving the intermediate transfer member 21; a driven roll 23 for supporting the intermediate transfer member 21; 24, 25, 7, the intermediate transfer body 21 interposed therebetween respective photosensitive drums 11 arranged in a position facing the four primary transfer bias roller 31, a backup roller 26 which is a counter roll and the secondary transfer bias roller 32,
Feed roll 42 for supplying recording medium P, tray 4
3, a registration roller 44, a transport belt 45, a fixing device 5 for fixing a toner image on the recording medium P, a belt cleaner 6 for cleaning an intermediate transfer member disposed downstream of the secondary transfer bias roll 32, An operation panel 81 for inputting / displaying operation information relating to printing conditions in accordance with an operation, a test pattern image forming unit 84 for forming a test pattern image for a test patch, and a density of a test pattern image formed on the intermediate transfer body 21. Toner image density detection sensor 71 to detect, temperature and humidity sensor 7 for monitoring temperature and humidity inside the device
3. Determine the intensity of the transfer electric field at the time of the secondary transfer based on the information from the recording medium information detecting means 74 for detecting information on the recording medium in the tray 43, the in-machine temperature / humidity sensor 73 and the recording medium information detecting means 74. Transfer electric field strength determining means 8
2. transfer electric field control means 8 for controlling the intensity of the secondary transfer electric field based on the signal from the transfer electric field intensity determination means 82;
3, etc. are provided.

An image forming operation is performed by the image forming apparatus configured as described above as follows.

When the surface of each photoconductor drum 11 is irradiated with exposure light corresponding to each color by a well-known electrophotographic process, an electrostatic latent image corresponding to each color is formed on each photoconductor drum 11. . The electrostatic latent images formed on the respective photosensitive drums are developed with the respective color toners by the four developing devices 14 to form the respective color toner images on the respective photosensitive drums.

[0007] The toner images of these colors are applied to the respective photosensitive drums 1.
1 and the primary transfer section T where the intermediate transfer body 21 contacts
At 1, the image is sequentially transferred from each photosensitive drum 11 to the intermediate transfer body 21. In each primary transfer section T1, a semi-conductive primary transfer bias roll 31 is disposed on the back side of the intermediate transfer body 21 so as to face each photoconductor drum 11, and the primary transfer bias roll 31 is provided. To the photosensitive drums 11 by applying a voltage having a polarity opposite to the charging polarity of the toner.
The upper toner image is electrostatically transferred so as to be sequentially superimposed on the intermediate transfer body 21. Each photosensitive drum 1 after primary transfer
The toner remaining on the photoconductor 1 is removed by each photoconductor cleaner 15.

The toner image primarily transferred onto the intermediate transfer member 21 is conveyed to a secondary transfer portion T2 facing the conveyance path of the recording medium P as the intermediate transfer member 21 rotates.

The recording medium P is carried out from the tray 43 to the registration roll 44 by the feed roll 42, and is supplied to the nip portion between the secondary transfer bias roll 32 and the intermediate transfer body 21 at a predetermined timing by the registration roll 44.
On the back side of the intermediate transfer body 21 in the secondary transfer portion T2, a backup roll 26 serving as a counter electrode of the secondary transfer bias roll 32 is provided, and toner is applied to the secondary transfer bias roll 32 at a predetermined timing. Is applied to the backup roll 26, and the toner image carried on the intermediate transfer body 21 is electrostatically secondarily transferred onto the recording medium P by the action of the charge.

The recording medium P onto which the toner image has been transferred is separated from the intermediate transfer member 21 and sent to the fixing device 5 by the transport belt 45 to perform a fixing process of the toner image. On the other hand, the intermediate transfer member 21 on which the secondary transfer of the toner image has been completed removes residual toner by the belt cleaner 6 located downstream of the secondary transfer portion T2.

The intermediate transfer member 21 is made of a resin such as polyimide, polycarbonate or polyamide containing an appropriate amount of an antistatic agent such as carbon black, and has a volume resistivity of 10 ⁶ Ω · cm to 10 ¹⁴ Ω.・ Cm
The thickness is set to, for example, 0.1 mm.

In the image forming process of the conventional image forming apparatus described above, in order to obtain a good image on the recording medium P, the toner image formed on the photosensitive drum 11 is subjected to primary transfer and secondary transfer. It is necessary to faithfully transfer the toner image on the photosensitive drum 11 onto the intermediate transfer body 21 and whether the toner image on the intermediate transfer body 21 can be faithfully transferred onto the recording medium P. And whether the transfer electric field is set to an appropriate value.

Conventionally, the transfer electric field is controlled by a control table or a control method which is set in advance based on the monitoring result of the temperature and humidity in the apparatus by the temperature and humidity sensor 73 and the detection result of the system resistance of the transfer section mainly before and after image formation. (Less than,
These values are collectively referred to as a control table). In order to control the transfer electric field to an appropriate value, a huge variety of control tables corresponding to various environments and various system resistances are indispensable, and the more precise the control table is, the more various An appropriate operation can be performed according to the condition.

In the primary transfer, the components that are subject to the system resistance of the transfer section include components that do not depend on the operator's will, such as the photosensitive drum 11, the intermediate transfer member 21, the primary transfer bias roll 31, and toner. Only. In addition, environmental changes and changes over time of these components have been already confirmed, and it is possible to predict these changes and create the control table precisely based on the predicted changes.
Further, for the primary transfer, a control method is also disclosed in which a test patch is created while changing the primary transfer electric field, and an optimum value is selected from the patch toner image density detection result by the toner image density detection sensor 71 on the intermediate transfer body 21. (For example, see Japanese Patent Application Laid-Open No. H11-212315).

[0015]

On the other hand, in the secondary transfer, a backup roll 2 constituting a secondary transfer device is used.
6. Not only the secondary transfer bias roll 32 and the intermediate transfer body 21 but also the recording medium itself has a great effect on the system resistance of the transfer unit. As with the primary transfer, in the case of rolls and intermediate transfer bodies, it is possible to create a control table by grasping each environmental change and changes over time, but the recording medium is basically free to the operator. This is determined, and it is almost impossible to predict in advance what kind of recording medium to use.

Conventionally, to solve this problem, a recording medium that is widely used for each type of recording medium, such as plain paper / coated paper / 0HP film, is set as a representative paper. In the case of (1), the representative paper is further set for each basis weight, and the secondary transfer electric field is optimized for each of the representative papers. How many types of recording media can be optimally controlled depends on how finely the types of recording media are classified, and the characteristic that representative paper (or OHP film) can represent the type of recording media. It depends on whether or not.

However, the characteristics of the recording medium, especially the characteristics of the paper, are various, and it is difficult to obtain an optimum image unless individual control tables are prepared for all types of paper. However, in view of the fact that there are a wide variety of papers and that new paper types are being developed day by day, there is a natural limit to the above-described methods. Optimization can be performed by limiting the types of paper that can be used in the image forming apparatus, but this would greatly impair the universality of the recording medium of the electrophotographic image forming apparatus.

As a method for improving the above problem, Japanese Patent Application Laid-Open
Japanese Patent Application Laid-Open Nos. 209948 and 10-048939 disclose a method of forming a test pattern image while changing the transfer output, monitoring the density of an unfixed image on recording paper, and selecting an optimum value. I have. In Japanese Patent Application Laid-Open No. Hei 10-193689, two types of test images of a single color and a plurality of colors are formed with a single transfer output, the density of a fixed image on a recording paper is monitored, and the difference between the two types of test images is determined. Accordingly, a method of calculating an optimum value of an image forming condition is disclosed.

However, regarding the secondary transfer, since the point at which the transferability of a single-color image and the transferability of a plurality of color images are compatible is the optimum point, an optimum value can be obtained from an unfixed toner image that can monitor only the transferability of a single color. Can not. Further, even if both a single color image and a plurality of color images are monitored at the fixed image density, the calculation formula required to calculate the optimum value from the monitor value differs for each recording medium, so that the above problem can be solved. This is inadequate as a measure.

An object of the present invention is to provide an image forming apparatus capable of automatically setting an optimum secondary transfer electric field for a recording medium to be used in view of the above circumstances.

[0021]

An image forming apparatus according to the present invention, which achieves the above object, forms electrostatic latent images corresponding to different colors on a plurality of image carriers, and forms the electrostatic latent images on the plurality of image carriers. The electrostatic latent image formed on the image carrier is developed with toner of each color to form a toner image of each color on the plurality of image carriers, and the toner images of each color are sequentially primary-transferred to a predetermined intermediate transfer body. An image is formed on the recording medium by secondarily transferring the toner image primarily transferred on the intermediate transfer member to a predetermined recording medium and fixing the secondary transferred toner image on the recording medium. In the image forming apparatus, a test pattern image forming means for forming a single color test pattern image composed of a single color toner and a multicolor test pattern image composed of a plurality of color toners on the intermediate transfer body, and the test pattern image forming means When the single-color test pattern image and the multi-color test pattern image formed on the intermediate transfer body are secondarily transferred to the recording medium, the transfer electric field intensity is changed so that the transfer electric field intensity changes over a predetermined electric field intensity range. A transfer electric field control unit for controlling the transfer electric field, and a density of the single-color test pattern image and the multi-color test pattern image after the secondary transfer onto the recording medium and further fixing by the transfer electric field controlled by the transfer electric field control unit are measured. Determining the intensity of a transfer electric field when the toner image on the intermediate transfer body is secondarily transferred to a recording medium based on the result of the density measurement by the fixed image density measurement means and the fixed image density measurement means. Means.

Here, the test pattern image forming means includes a single color test pattern image formed of a single color toner and a plurality of single color test pattern images formed on the intermediate transfer member from electrostatic latent images having the same image density for at least the same color. It is preferable to form a multi-color test pattern image composed of color toners.

When the fixed image density measuring means measures the density of the multi-color test pattern image formed on the recording medium, it measures the density of each single-color toner constituting the multi-color test pattern image. When the fixed image density measuring unit measures the density of the multi-color test pattern image formed on the recording medium, each of the single-color toners constituting the multi-color test pattern image may be used. The fixed image density measuring means may measure the density of the multi-color test pattern image formed on the recording medium. In the meantime, among the single-color toners constituting the multi-color test pattern image, the density of the single-color toner first primary-transferred onto the intermediate transfer body is determined. It may perform a constant.

The apparatus further comprises storage medium information detection means for detecting the type of storage medium, and when the storage medium information detection means detects a new type of storage medium, secondary transfer to a new type of storage medium is performed. It is also a preferable embodiment to provide a transfer electric field intensity determination sequence control means for executing a sequence for determining the intensity of the transfer electric field when the transfer is performed.

Further, the apparatus has an operation panel for inputting operation information relating to printing conditions in response to an operation of the operator, and when new operation information relating to printing conditions is inputted by the operation panel, the new operation information which is inputted It is also a preferable embodiment to provide a transfer electric field intensity determination sequence control means for executing a sequence for determining the intensity of the transfer electric field at the time of the secondary transfer based on the above.

[0026]

Embodiments of the present invention will be described below.

FIG. 1 is a schematic diagram showing an embodiment of a color copying machine to which the image forming apparatus of the present invention is applied.

As shown in FIG. 1, this image forming apparatus has the same configuration as the conventional image forming apparatus shown in FIG.
For example, four photosensitive drums 11, four charging devices 12, four exposing devices 13, corresponding to yellow (Y), magenta (M), cyan (C) and black (K), respectively.
Four developing devices 14, four photoconductor cleaners 15, an intermediate transfer member 21, a driving roll 22, and driven rolls 23, 24, 2
5, 27, four primary transfer bias rolls 31, secondary transfer bias rolls 32, and backup rolls 2
6, feed roll 42, tray 43, registration roll 4
4, conveying belt 45, fixing device 5, belt cleaner 6, operation panel 81, test pattern image forming means 84, toner image density detecting sensor 71, in-machine temperature / humidity sensor 73, recording medium information detecting means 74, transfer electric field strength determining means 82, and a transfer electric field control unit 83 and the like. These components are the same as those of the conventional color image forming apparatus shown in FIG.

In the image forming apparatus of the present embodiment, a fixed image density sensor 90 is provided downstream of the fixing device 5 in addition to these constituent elements.

The photosensitive drum 1 according to the present embodiment
Reference numeral 1 corresponds to an image carrier according to the present invention, and the fixed image density sensor 90 according to the present embodiment corresponds to a fixed image density measuring unit according to the present invention.

FIG. 2 is a diagram showing a test pattern (a) used in the present embodiment and the intensity (b) of a control electric field when the test pattern is secondarily transferred.

In this embodiment, four types of test patterns as shown in FIG. 2A are formed as electrostatic latent images on each photosensitive drum 11 by the test pattern image forming means 84 shown in FIG. .

As shown in FIG. 2A, a test pattern is a continuous patch of a single color of Y (yellow) and K (black) formed of an electrostatic latent image of the same image density for one color.
(Green: G = Y + C), and PK (process black: PK = Y + M + C). Here, as the same image density, 20% is used for a single color, and 100% is used for a plurality of colors.

The image density at the time of forming a test pattern is preferably a highlight which is easily affected by retransfer or the like for a single color, and 100% at which transferability is the worst for a plurality of colors. However, the density may be higher or lower in consideration of the frequency of use and the detection sensitivity of the fixed image density sensor. Although any color may be basically used as the single color in the test pattern, the number of times that the primary transfer is performed on the intermediate transfer member 21 and then passes through the primary transfer portion of another color is the largest, and the occurrence of retransfer is most likely. It is preferable to select the most likely first color (yellow in FIG. 6) or black, which is the most frequently used monochrome image. It is preferable to adopt one color each from the secondary colors (green, red, blue) and the tertiary colors (PK) as the plural colors. It is acceptable to use only secondary colors.

In this embodiment, as shown in FIG. 2A, two rows of test patterns are formed in the paper width direction intersecting with the process direction.
The number of rows may be equal to or more than the number of rows, and may be set according to how many fixed image density sensors 90 are mounted in the paper width direction.

A test pattern of such an electrostatic latent image is formed on each of the photosensitive drums 11 and is developed by each of the developing devices 14 to form a test image of a toner image. The primary transfer is sequentially performed on the intermediate transfer body 21 by the primary transfer bias roll 31.

As shown in FIG. 2B, the test pattern image of each color primary-transferred to the intermediate transfer body 21 has a lower limit value to an upper limit value for each color test pattern image.
Secondary transfer is performed on the recording medium by the control electric field whose intensity increases by ΔE at the stage. The number of steps of the control electric field strength is set to an appropriate value according to the number of patches of the test pattern.

Next, a monochromatic image is formed by a fixed image density sensor 90, which is provided downstream of the fixing device 5 and includes a light emitting diode (LED) and a photodiode, as shown in, for example, Japanese Patent Application Laid-Open No. 10-193689. Image density and multi-color image density are measured.

FIG. 3 is a diagram showing a measurement result of the fixed image density sensor according to the present embodiment.

FIG. 3 shows the relationship between the secondary transfer electric field strength and the fixed image density for a test pattern image of K single color having an image density of 20% and a test pattern image of a plurality of colors of PK having an image density of 100%. ing.

In general, when the transfer electric field intensity is too weak, the toner image on the intermediate transfer member 21 cannot be transferred to the recording medium P, so that the fixed image density becomes low. When the transfer electric field intensity is too strong, the toner is injected by charge injection. , And the secondary transfer to the recording medium is stopped, so that the fixed image density also becomes low. For this reason, the fixed image density draws an upwardly convex curve, which initially increases with an increase in the transfer electric field intensity and decreases with the electric field intensity as a peak.

In particular, a highlight of a single color and a low density is easily affected by charge injection, and when the transfer electric field is increased, the density lowers before a plurality of colors.
In the case of a plurality of colors, the toner image which is the lowermost layer of the toner layers on the intermediate transfer body 21 in a region where the transfer electric field is weak, that is, the toner image which is the uppermost layer on the recording medium (in the image forming apparatus shown in FIG. The first color yellow toner image)
Is particularly difficult to be secondary-transferred. In addition, since the second color has twice the amount of toner on the intermediate transfer body 21 even at the same density as that of the single color, and the third color has three times the amount of toner on the intermediate transfer body 21,
In order to transfer the lowermost yellow toner image of the toner layers to the recording medium, an electric field stronger than that of the monochromatic image is required.

Therefore, as shown in FIG. 3, while the density peak position of the 20% K monochromatic image is located in the region where the transfer electric field is relatively weak, the Y color density peak position of the uppermost layer in the 100% PK image is obtained. Is in a region where the transfer electric field is relatively strong. That is,
It can be seen that the latter having a larger amount of toner to be transferred is shifted to the strong electric field side.

The transfer electric field strength determining means 82 of this embodiment
In FIG. 1 (see FIG. 1), the optimum secondary transfer electric field strength under the current environment is determined from the density curve obtained as described above. For example, in the example of FIG. 3, the secondary transfer electric field strength of the star at which the density of the composite curve C (broken line) of the density curve A of the 20% K single color and the density curve B of the Y color in 100% PK becomes a peak is shown. The optimum secondary transfer electric field intensity is obtained.

In this manner, the optimum secondary transfer electric field for the recording medium to be used under the current environment can be automatically determined. When deciding the optimum value, it is also possible to assign a weight to each of the single-color density and the color density of the uppermost layer among a plurality of colors, and to determine the optimum value based on the sum thereof.

By storing the optimum value determined in this way, the optimum transfer state can be realized in the print mode following the test pattern output mode.

Note that, when the fixed image density sensor 90 measures the density of the multi-color test pattern image formed on the recording medium, as in the above-described embodiment, each of the single-color toners forming the multi-color test pattern image is measured. Intermediate transfer member 2
The density measurement may be performed on the single-color toner (for example, Y) that is first primary-transferred onto the first unit 1. Alternatively, only one of the single-color toners constituting the multi-color test pattern image may be used. May be measured, or the density of each single-color toner constituting the multi-color test pattern image may be measured separately.

As described below, it is preferable to measure a plurality of color image densities separately for each component toner color. [Example 1] Next, an example of secondary transfer electric field control in this embodiment will be described.

FIG. 4 is a flowchart of the process of optimizing the secondary transfer electric field in the first embodiment.

The first embodiment shows a processing flow of the secondary transfer control when no control table is provided.

The optimization processing in the first embodiment is executed before each print job.

First, as shown in FIG. 2, the control electric field defined by the difference ΔE between the upper limit electric field and the lower limit electric field and the center value Ecnt is set (FIG. 4: Step S0).
1). The number of steps of the control electric field intensity is set by the number of patches of the test pattern.

A test pattern (see FIG. 2A) formed on each photosensitive drum 11 and developed by the test pattern image forming means 84 (see FIG. 1) is formed on the intermediate transfer body 21 by primary transfer. (Step S02).

Next, the test pattern formed on the intermediate transfer body 21 is transferred onto the recording medium P by the control electric field described with reference to FIG. 2B (step S0).
3). The test pattern transferred to the recording medium P passes through the fixing device 5 and is fixed, and the density is measured by a fixed image density sensor 90 provided downstream of the test pattern (step S04). Based on the measurement result by the fixed image density sensor 90, it is determined whether or not both the density curve A of the single-color image and the density curve B of the multi-color image have peaks as shown in the graph of FIG. 3 (step S05). .

If the result of determination in step S05 is that neither has a peak or only one of them has a peak,
The gradient of the density curve is calculated (step S06), the central value Ecnt (see FIG. 2) is shifted in the direction of increasing the density (step S07), and the process returns to step S02 to form a test pattern again.

If the result of determination in step S05 is that both have peaks, the optimum value of the secondary transfer electric field strength as indicated by the asterisk in FIG. 3 is determined. After the secondary transfer electric field strength is determined in this way, test printing for confirmation is performed (step S08).

Next, the operation panel 81 (see FIG. 1)
A message "Is this setting acceptable?" Is displayed (step S09), and if the operator determines that further optimization is necessary, a more detailed setting is made by narrowing the control transfer electric field [Delta] E. Can be performed (step S010 and step S02 and subsequent steps). If the operator determines that this setting is sufficient, the determined value is stored in the memory after the secondary transfer electric field is determined. The same environment,
This is because it is sufficiently assumed that printing on the same recording medium is repeated.

Further, the operator may freely assign a name or a comment together with the temperature and humidity at the time of the optimization and store it in the memory. By doing so, before the next time, before entering the processing flow of the secondary transfer electric field optimization, the optimization list up to the previous time can be read, and the operator can select from the list at any time or select a new optimization. it can.

As a pattern for trial printing, a pattern built in the image forming apparatus may be used, or an operator may specify an image pattern to be actually printed.

[Embodiment 2] FIG. 5 is a flowchart of a process for optimizing the secondary transfer electric field in the second embodiment.

The second embodiment shows a processing flow of the secondary transfer control when a simple control table is provided.

The optimization processing in the second embodiment is performed when the operator determines that the print image quality needs to be improved.
1 (see FIG. 1).

The second embodiment is different from the first embodiment in that the image forming apparatus of this embodiment is provided with a simple secondary transfer electric field control table, so that the Ecnt (see Fig. 2) of the control electric field should be set near the optimum value in advance from available recording medium information (recording medium type, basis weight, coated / uncoated, etc.) and environmental information (temperature and humidity). There is a point that can. That is,
By the transfer electric field strength determination sequence control means of the present invention,
It is possible to perform the fine adjustment for each recording medium.

The flowchart in the second embodiment is as follows.
As shown in FIG. 5, it is basically similar to the flowchart of the first embodiment (see FIG. 4).

First, environment information and recording medium information are obtained (step S21), and Ecnt (see FIG. 2) is selected from a control table provided in the image forming apparatus (step S22).

The steps from step S23 to step S31 are exactly the same as the steps from step S02 to step S10 in the first embodiment, and a description thereof will be omitted.

In step S32, an inquiry is made to the operator as to whether the current set value is to be used regularly in the future, and if it is to be used regularly, the flow advances to step S34 to update the control table and end all the processing. I do. If it is not used regularly, the process proceeds to step S33, the determined value is stored in the memory, and all processing ends.

When a fixed value is stored in the memory, if a simple secondary transfer electric field control table is provided, the control table itself may be rewritten. Further, as in the first embodiment, the determined value itself may be stored as a list, or the storage form may be left to the operator's judgment based on the frequency of use of the recording medium.

[0069]

As described above, according to the image forming apparatus of the present invention, a single color test pattern image composed of a single color toner and a multicolor test pattern image composed of a plurality of color toners are formed on an intermediate transfer member. The transfer electric field intensity is a predetermined electric field intensity when the single-color test pattern image and the multi-color test pattern image formed on the intermediate transfer member by the test pattern image forming means are secondarily transferred to the recording medium. A transfer electric field control means for controlling a transfer electric field intensity so as to vary over a range, and a single-color test pattern image and a plurality of single-color test patterns after being secondarily transferred onto a recording medium by a transfer electric field controlled by the transfer electric field control means and further fixed A fixed image density measuring means for measuring the density of the color test pattern image, and a density measurement result based on the fixed image density measuring means. A transfer electric field intensity determining means for determining the intensity of the transfer electric field when the toner image on the intermediate transfer member is secondarily transferred to the recording medium, so that the secondary image is optimized for many types of recording media. An image can be formed by a transfer electric field. Moreover, a series of automatic processes for the optimization process can be realized by a simple operation.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a color copying machine to which an image forming apparatus of the present invention is applied.

FIG. 2 is a diagram illustrating a test pattern (a) used in the present embodiment and a control electric field strength (b) when the test pattern is secondarily transferred.

FIG. 3 is a diagram showing measurement results of a fixed image density sensor according to the embodiment.

FIG. 4 is a flowchart of a process of optimizing a secondary transfer electric field in the first embodiment.

FIG. 5 is a flowchart of a secondary transfer electric field optimizing process in the second embodiment.

FIG. 6 is a diagram illustrating a schematic configuration of a conventional intermediate transfer type color image forming apparatus.

[Explanation of symbols]

 Reference Signs List 5 fixing device 6 belt cleaner 11 photoreceptor drum 12 charging device 13 exposure device 14 developing device 15 photoreceptor cleaner 21 intermediate transfer member 22 drive roll 23, 24, 25, 27 driven roll 26 backup roll 31 primary transfer bias roll 32 2 Next transfer bias roll 42 Feed roll 43 Tray 44 Registration roll 45 Conveyor belt 71 Toner image density detection sensor 73 In-machine temperature / humidity sensor 74 Recording medium information detection unit 81 Operation panel 82 Transfer electric field intensity determination unit 83 Transfer electric field control unit 84 Test pattern image Forming means 90 Fixed image density sensor P Recording medium T1 Primary transfer section T2 Secondary transfer section

Continued on the front page (72) Inventor Takashi Kawabata 2274 Hongo, Ebina-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd. ) Inventor Masaaki Takahashi 2274 Hongo, Ebina-shi, Kanagawa Prefecture F-Terminus at Ebina Works, Fuji Xerox Co., Ltd. BB36 BB42 BB54 BB63 2H032 AA05 AA15 BA09 BA21 CA02 CA12 CA15

Claims (7)

[Claims] An electrostatic latent image corresponding to each of different colors is formed on a plurality of image carriers, and the electrostatic latent images formed on the plurality of image carriers are developed with toner of each color. Forming a toner image of each color on the plurality of image carriers, sequentially transferring the toner images of each color to a predetermined intermediate transfer member sequentially, and recording the toner image primarily transferred on the intermediate transfer member in a predetermined recording state. An image forming apparatus that forms an image on the recording medium by secondary-transferring to a medium and fixing the secondary-transferred toner image on the recording medium; A test pattern image forming means for forming a single-color test pattern image and a multi-color test pattern image composed of a plurality of color toners; and the single-color test pattern image and the plurality of colors formed on the intermediate transfer member by the test pattern image forming means. Tess A transfer electric field control unit for controlling a transfer electric field intensity such that a transfer electric field intensity changes over a predetermined electric field intensity range when the pattern image is secondarily transferred to the recording medium; and a transfer electric field controlled by the transfer electric field control unit. A fixed image density measuring unit that measures the density of the single-color test pattern image and the multi-color test pattern image that has been secondarily transferred onto the recording medium and further fixed by the fixing image density measuring unit. Based on
An image forming apparatus comprising: a transfer electric field intensity determining unit for determining an intensity of a transfer electric field when the toner image on the intermediate transfer member is secondarily transferred to a recording medium. 2. A test pattern image forming means comprising: a single-color test pattern image formed of a single-color toner and a plurality of colors formed on the intermediate transfer member from an electrostatic latent image having the same image density for at least the same color; 2. The image forming apparatus according to claim 1, wherein a multi-color test pattern image formed of the toner is formed. 3. The fixed image density measuring means, when measuring the density of the multi-color test pattern image formed on the recording medium, measures the density of each single-color toner constituting the multi-color test pattern image. The image forming apparatus according to claim 1, wherein: 4. When the fixed image density measuring means measures the density of the multi-color test pattern image formed on the recording medium, a predetermined one of the single-color toners constituting the multi-color test pattern image is used. 2. The method according to claim 1, wherein the density is measured only for one single color toner.
The image forming apparatus as described in the above. 5. When the fixed image density measuring means measures the density of the multi-color test pattern image formed on the recording medium, the fixed-image density measuring means includes a monochromatic toner of each of the monochromatic toners constituting the multi-color test pattern image. 5. The image forming apparatus according to claim 4, wherein the density measurement is performed on the single-color toner first primarily transferred onto the intermediate transfer member. 6. A storage medium information detecting means for detecting a type of a storage medium, and when a new type of storage medium is detected by the storage medium information detecting means, secondary transfer to a new type of recording medium is performed. 6. The image forming apparatus according to claim 1, further comprising a transfer electric field intensity determination sequence control unit that executes a sequence for determining the intensity of the transfer electric field when performing the operation. 7. An operation panel for inputting operation information relating to printing conditions in response to an operation of an operator, wherein when the operation panel inputs new operation information relating to printing conditions, the input new operation information The image forming apparatus according to any one of claims 1 to 5, further comprising a transfer electric field intensity determination sequence control unit that executes a sequence for determining the intensity of the transfer electric field at the time of the secondary transfer based on the control information. apparatus.