JP2005352379A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To satisfy both image quality and usability regardless of an image type. <P>SOLUTION: When printing is requested, determination is made whether output data is image data or text data (S2). The output data is determined to be the image data when the area of an image is equal to or above a threshold as a result of determination from a ratio between the area of an image section calculated from a dot counter and the area of the image calculated from the area of paper outputted. When the output image is the image data, a sheet counter determines whether the count of the output sheets after the previous process control is greater than the threshold of the number of sheets corresponding to the image data (S3). When the count is greater than that, a process control is executed (S4). In the case that the output image is determined to be text data, image formation is started without performing the process control (S6). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a copying machine, a printer, a facsimile, a plotter, or an image forming apparatus that combines any of them.

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, a technique for testing image forming performance such as image forming performance at a predetermined timing using an image density sensor is known for the purpose of stabilizing image quality.
Specifically, first, a patch pattern is formed on an intermediate transfer belt as an image carrier. After the patch pattern is formed, the toner adhesion amount on the patch pattern is measured by an image density sensor. A process control technique is known in which the image forming performance is discriminated based on the measured image density, and the result is fed back to change the image forming condition to control the image density to be constant.
Since the image forming ability changes depending on temperature and humidity changes and changes over time, a constant image quality is maintained by automatically executing the process control described above every predetermined number of prints or every predetermined time.

JP 2003-91109 A

However, if process control is frequently executed in order to maintain a constant image quality, print output cannot be performed during process control, and thus a time during which the user cannot use, that is, downtime occurs.
When downtime occurs when you want to output a document in a hurry, it is often inconvenient and uncomfortable because you cannot print out.
Further, if the frequency of process control is reduced in order to reduce downtime, the image quality deteriorates and often causes a problem when outputting image data.

  Therefore, an object of the present invention is to provide an image forming apparatus that can achieve both image quality and usability regardless of the type of image.

In order to achieve the above object, the present invention frequently performs process control when outputting image data that requires high image quality, and performs process control when outputting text data that requires speed. The frequency was lowered to achieve both image quality and usability.
Specifically, according to the first aspect of the present invention, the patch pattern creating means for creating a patch pattern on the image carrier, the means for detecting the image density of the patch pattern, and the detected image density information In an image forming apparatus having process control means for feeding back to formation conditions and automatically executing process control under predetermined conditions, process control is performed depending on whether the output image is text data or image data. The conditions for automatic execution are different.

  According to the second aspect of the present invention, in the image forming apparatus according to the first aspect, the condition that the frequency of executing the process control is higher when the output image is image data than when the output image is text data. It is characterized by.

  According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, when the output image is text data, the process control is not executed before the start of image formation. It is characterized in that the control may be executed.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the second aspect, the interval between execution of process control and execution of the next process control is such that image data is output rather than output of text data. Is shorter.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the first aspect, the determination as to whether the image to be output is text data or image data is output as the area of the image portion calculated from the image dot count. It is made based on the area ratio of the image portion calculated from the area of the paper.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the threshold value of the area ratio of the image portion for determining whether the data is text data or image data is 3% to 30%, If it is less than the threshold value, it is determined that the data is text data, and if it is greater than the threshold value, it is determined that the data is image data.

  According to a seventh aspect of the present invention, in the image forming apparatus according to the first aspect, the determination as to whether the output image is text data or image data is based on the type of document instructed by the engine controller or the host computer. It is made to be made.

  According to the first aspect of the present invention, the patch pattern creating means for creating a patch pattern on the image carrier, the means for detecting the image density of the patch pattern, and the detected image density information as image forming conditions In an image forming apparatus having process control means for feedback and automatically executing process control under a predetermined condition, the process control is automatically performed depending on whether the output image is text data or image data. Since the execution conditions are different, the frequency of process control can be changed according to the type of image, and both image quality and usability can be achieved.

  According to the second aspect of the present invention, in the image forming apparatus according to the first aspect, the process control is executed more frequently when the output image is image data than when the output image is text data. Therefore, when outputting image data that requires high image quality, process control is frequently performed, and when outputting text data that requires speed, the frequency of process control is reduced, and Both quality and usability can be achieved.

  According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, when the output image is text data, the process control is not executed before the start of image formation. In some cases, process control may be executed in some cases, so that both image quality and usability can be achieved.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the second aspect, the interval between the execution of the process control and the execution of the next process control is greater than the output of text data. Since the case of doing so is shorter, it is possible to achieve both image quality and usability.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the first aspect, the determination of whether the output image is text data or image data is based on the area of the image portion calculated from the image dot count. Since the determination is made based on the area ratio of the image portion calculated from the area of the sheet to be output, the determination accuracy can be improved.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the threshold of the area ratio of the image portion for determining whether the data is text data or image data is 3% to 30%. Yes, when it is less than the threshold value, it is determined that the data is text data, and when it is equal to or higher than the threshold value, it is determined that the data is image data, so that the accuracy of the determination can be further improved.

  According to the seventh aspect of the present invention, in the image forming apparatus according to the first aspect, the determination as to whether the image to be output is text data or image data is made based on the document type designated by the engine controller or the host computer. Since it is based on this, it is possible to achieve both image quality and usability.

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
First, an overview of the overall configuration of an electrophotographic laser printer (hereinafter simply referred to as “printer”) as an image forming apparatus according to the present embodiment will be described with reference to FIG.
The printer 100 includes four process cartridges 6Y, 6M, 6C, and 6K for generating toner images of yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K). These use Y, M, C, and K toners of different colors as the image forming material, but the other configurations are the same and are replaced when the lifetime is reached.

The structure of the process cartridge 6Y for generating a Y toner image will be described as a representative. As shown in FIG. 2, a drum-shaped photosensitive member 1Y as an image carrier, a drum cleaning device 2Y, a charge eliminating device (not shown). ), A charging device 4Y, a developing device 5Y, and the like.
The developing device 5Y includes a developing roller 51Y, a doctor blade 52Y that regulates the layer thickness of the developer supplied onto the developing roller 51Y, a developer supply unit 53Y and a toner replenishing unit 54Y of the developing casing. It has a conveying member 55Y and a toner density sensor 56Y. Based on the detection information of the toner density sensor 56Y, the control motor 57Y controls the drive motor 41Y so that the toner is replenished and the developer is stirred and conveyed.

The process cartridge 6Y is detachable from the apparatus main body of the printer 100, and consumable parts can be exchanged at once (collectively).
The charging device 4Y uniformly charges the surface of the photoreceptor 1Y that is rotated clockwise in the drawing by a driving unit (not shown). The surface of the uniformly charged photoreceptor 1 </ b> Y is exposed and scanned by the laser beam L to carry an electrostatic latent image for Y. The Y electrostatic latent image is developed into a Y toner image by the developing device 5Y using Y toner. The Y toner image is intermediately transferred onto the intermediate transfer belt 8.
The drum cleaning device 2Y removes the toner remaining on the surface of the photoreceptor 1Y after the intermediate transfer process. The static eliminator neutralizes residual charges on the photoreceptor 1Y after cleaning. By this charge removal, the surface of the photoreceptor 1Y is initialized and prepared for the next image formation.

The other process cartridges 6M, 6C, and 6K have the same configuration. Similarly, M, C, and K toner images are formed on the photoreceptors 1M, 1C, and 1K, and the intermediate transfer belt 8 has an intermediate state. Transcribed.
In FIG. 1, an exposure device 7 is disposed below the process cartridges 6Y, 6M, 6C, and 6K in the drawing. The exposure device 7 serving as a latent image forming unit irradiates the respective photosensitive members in the process cartridges 6Y, 6M, 6C, and 6K with a laser beam L emitted based on the image information.
By this exposure, electrostatic latent images for Y, M, C, and K are formed on the photoreceptors 1Y, 1M, 1C, and 1K. The exposure apparatus 7 has a well-known configuration that irradiates the photosensitive member through a plurality of optical lenses and mirrors while scanning the laser beam L emitted from the light source with a polygon mirror that is rotationally driven by a motor. .

On the lower side of the exposure apparatus 7 in the drawing, a sheet feeding means having a sheet feeding cassette 26, a sheet feeding roller 27 incorporated in the structure of the sheet feeding cassette 26, a registration roller pair 28, and the like are disposed.
In the paper feed cassette 26, a plurality of transfer sheets S as recording media are stacked and stored, and a paper feed roller 27 is in contact with the uppermost transfer paper S. When the paper feeding roller 27 is rotated counterclockwise in the figure by a driving means (not shown), the uppermost transfer paper S is fed toward the roller (nip) of the registration roller pair 28.
The registration roller pair 28 rotationally drives both rollers so as to sandwich the transfer sheet S, but temporarily stops rotating immediately after the sandwiching. Then, the transfer sheet S is sent out toward a secondary transfer nip described later at an appropriate timing. In the sheet feeding unit having such a configuration, a conveying unit is configured by a combination of the sheet feeding roller 27 and a registration roller pair 28 as a timing roller pair.
This transport means transports the transfer paper S from a paper feed cassette 26 as a storage means to a secondary transfer nip described later.

Above the process cartridges 6Y, 6M, 6C, and 6K in the figure, an intermediate transfer unit 15 that moves the endlessly the intermediate transfer belt 8 as an intermediate transfer member while stretching is disposed. In addition to the intermediate transfer belt 8, the intermediate transfer unit 15 includes four primary transfer bias rollers 9Y, 9M, 9C, and 9K, a cleaning device 10, and the like.
A secondary transfer backup roller 12, a cleaning backup roller 13, a tension roller 14 and the like are also provided. The intermediate transfer belt 8 is endlessly moved in the counterclockwise direction in the figure by the rotational drive of at least one of the rollers while being stretched around these three rollers. The primary transfer bias rollers 9Y, 9M, 9C, and 9K sandwich the intermediate transfer belt 8 that is moved endlessly in this manner from the photoreceptors 1Y, 1M, 1C, and 1K to form primary transfer nips, respectively. Yes.
In these methods, a transfer bias having a polarity opposite to that of toner (for example, plus) is applied to the back surface (loop inner peripheral surface) of the intermediate transfer belt 8.

All the rollers except the primary transfer bias rollers 9Y, 9M, 9C, and 9K are electrically grounded. The intermediate transfer belt 8 sequentially passes through the primary transfer nips for Y, M, C, and K along with the endless movement thereof, and Y, M, and C on the photoreceptors 1Y, 1M, 1C, and 1K. , K toner images are superimposed and primarily transferred.
As a result, a four-color superimposed toner image (hereinafter referred to as “four-color toner image”) is formed on the intermediate transfer belt 8.
The secondary transfer backup roller 12 sandwiches the intermediate transfer belt 8 between the secondary transfer roller 19 and forms a secondary transfer nip. The four-color toner image formed on the intermediate transfer belt 8 is transferred to the transfer paper S at the secondary transfer nip.
Untransferred toner that has not been transferred to the transfer sheet S adheres to the intermediate transfer belt 8 after passing through the secondary transfer nip. This is cleaned by the cleaning device 10.

In the secondary transfer nip, the transfer sheet S is sandwiched between the intermediate transfer belt 8 and the secondary transfer roller 19 whose surfaces move in the forward direction, and is conveyed in the opposite direction to the registration roller pair 28 side.
When the transfer sheet S sent out from the secondary transfer nip passes between rollers of the fixing device 20, the four-color toner image transferred to the surface is fixed by heat and pressure. Thereafter, the transfer sheet S is discharged out of the apparatus through the pair of discharge roller pairs 29. A stack unit 30 is formed on the upper surface of the printer main body, and the transfer sheets S discharged to the outside by the discharge roller pair 29 are sequentially stacked on the stack unit 30.
Under the stack unit 30, toner tanks 32Y, 32M, 32C, and 32K are arranged.

In FIG. 1, a reflection type photosensor 40 as an image density detection means is disposed above the secondary transfer backup roller 12 so as to output a signal corresponding to the light reflectance on the intermediate transfer belt 8. It is configured.
In this reflection type photosensor 40, the difference between the amount of reflected light on the surface of the intermediate transfer belt 8 and the amount of reflected light of a reference pattern image to be described later can be set to a sufficient value between the diffuse light detection type and the regular reflection light detection type. Is used. The role of the reflective photosensor 40 will be described later.

FIG. 3 is a block diagram showing a part of the electric circuit of the laser printer. In the figure, control unit 150 is electrically connected to toner image forming units (process cartridges) 6Y, 6M, 6C, 6K, optical writing unit 7, paper feed cassette 26, registration roller pair 28, transfer unit 15, reflection type. The photo sensor 40 and the like are controlled.
The control unit 150 includes a CPU 150a that controls a calculation unit and the like, and a RAM 150b that stores data.
The control unit 150 performs the toner image forming units 6Y and 6M at predetermined timings such as when a main power supply (not shown) is turned on, when waiting after a predetermined time has elapsed, or when waiting for a predetermined number of prints to be output. , 6C, and 6K image forming performances are tested, and the test results are fed back to the image forming conditions to stabilize the image quality.

  Specifically, when this predetermined timing comes, first, the photosensitive drums 1Y, 1M, 1C, and 1K are uniformly charged while being rotated. With respect to this charging, unlike the uniform charging (for example, −700 V) during normal printing, the potential is gradually increased. Then, development is performed with the developing units 6Y, 6M, 6C, and 6K while forming an electrostatic latent image for a reference pattern image as a patch pattern by scanning with the laser light L. By this development, bias development pattern images of the respective colors are formed on the photosensitive drums 1Y, 1M, 1C, and 1K. During development, the control unit 150 performs control so that the value of the developing bias applied to the developing roller 51 of each developing device 5 is gradually increased.

The bias development pattern images of these colors are transferred so as to be arranged on the intermediate transfer belt 8 without overlapping. By this transfer, a pattern block constituted by the reference pattern image of each color is formed on the intermediate transfer belt 8.
When the reference image of each reference pattern image in the pattern block passes through the position facing the reflective photosensor 40 as the intermediate transfer belt 8 moves endlessly, the amount of reflected light is detected and an electric signal is detected. It is output to the control unit 150.
The control unit 150 calculates the light reflectance of each reference image based on the output signals sequentially sent from the reflection type photosensor 40, and stores it in the RAM 150a as density pattern data.
The pattern block that has passed the position facing the reflective photosensor 40 is cleaned by the cleaning device 10.

FIG. 4 is a schematic diagram showing the reference pattern image P (Py, Pm, Pc, Pk). In the figure, the reference pattern image P is composed of three reference images arranged at intervals of 15 mm.
In this laser printer, each reference image 101 is 15 mm long × 15 mm wide and is formed through a 15 mm gap. Therefore, the lengths of the reference pattern images Py, Pm, Pc, and Pk on the intermediate transfer belt 8 are L2 = 75 mm, respectively.
The reference pattern images Py, Pm, Pc, and Pk are transferred so as to be arranged on the intermediate transfer belt 8 without overlapping, unlike the toner images of the respective colors formed during the printing process. By such transfer, one pattern block PB composed of the reference pattern images Py, Pm, Pc, and Pk of each color is formed on the intermediate transfer belt 8.

FIG. 5 is a schematic diagram showing the installation pitch of the photosensitive drum 1. As shown in the figure, the photosensitive drums 1Y, 1M, 1C, and 1K are set at intervals of L1 = 90 mm. As described above, the length L2 of each of the reference pattern images Py, Pm, Pc, and Pk is 75 mm, which is shorter than the installation pitch L1 of the photosensitive drum 1. For this reason, the reference pattern images Py, Pm, Pc, and Pk can be independently transferred so as not to overlap the respective end portions.
FIG. 6 is a schematic diagram showing the pattern block formed on the intermediate transfer belt 8. On the intermediate transfer belt 8, two pattern blocks PB composed of four reference patterns Pk, Pc, Pm, and Py are formed. Specifically, a pattern block PB1 composed of the reference pattern images Pk1, Pc1, Pm1, and Py1 and a pattern block PB2 composed of the reference pattern images Pk2, Pc2, Pm2, and Py2 are formed.

The pattern blocks PB1 and PB2 are formed as follows. That is, the control unit 150 determines that the most upstream reference pattern Py1 is the most downstream side from the point when the reference pattern images Pk1, Pc1, Pm1, and Py1 in the first pattern block PB1 are transferred to the intermediate transfer belt 8. Control is performed so that the reference pattern image moves on the intermediate transfer belt 8 until it passes through the transfer nip of the photosensitive drum 1K.
In addition, the control unit 150 causes the reference pattern images Pk2, Pc2, Pm2, and Py2 of the second pattern block PB2 to be formed on the photosensitive drums 1Y, 1M, 1C, and 1K at a predetermined timing.
Specifically, the predetermined timing means that the rear end (reference pattern image Py1) of the first pattern block PB1 has moved further by a predetermined amount after passing through the transfer nip of the most downstream photosensitive drum 1K. This is the timing at which the reference pattern images Pk2, Pc2, Pm2, and Py2 of the pattern block PB2 start to be transferred onto the intermediate transfer belt 8 from the time point.

In FIG. 6, a reflection type photosensor 40 as an image detecting means is disposed on the upper right side of the transfer unit 15 including the intermediate transfer belt 8 in the drawing. Each reference pattern image on the intermediate transfer belt 8 is moved with endless movement and detected by the reflective photosensor 40, and then removed by the cleaning device 10 of the transfer unit 15.
The reflective photosensor 40 reflects the amount of light reflected from each reference image 101 constituting the reference pattern images Pk1, Pc1, Pm1, and Py1 from the front end to the rear end of the first pattern block PB1 in the following order. Detect.
That is, in order of three reference images 101 of the reference pattern image Pk1, three reference images 101 of the reference image Pc1, three reference images 101 of the reference image Pm1, and three reference images 101 of the reference image Py1. Detect. At this time, a voltage signal corresponding to the light reflection amount of each reference image 101 is detected by a method described later and sequentially output to the control unit 150.
The control unit 150 sequentially calculates the image density of each reference image 101 based on the voltage signals sequentially sent from the reflection type photosensor 40 and stores it in the RAM 150b. Note that the diffused light detection type is desirable for the reflective photosensor 40 in that it can detect a high density portion of color toner.

Based on the flowchart of FIG. 7, the execution timing of the process control for testing the printing operation accompanied by the determination in the present embodiment and the image forming performance such as the image forming performance described above will be described.
When there is a print request (S1), the control unit 150 determines whether the output data is image data or text data (S2). Whether image data is determined is determined by the area ratio of the image calculated from the area of the image portion calculated from the dot counter and the area of the output paper.
For example, when the area of the image portion calculated from the dot counter is 124.6 cm ² , the output paper size is A4 (623 cm ² ), and the threshold of the area ratio of the image portion is 10%, the area ratio of the image is 124.6. / 623 = 20%, and the image data is determined to be 10% or more of the threshold value. In the case of image image data, since the white portion is usually smaller than text data, the image area tends to increase. Therefore, the method for determining the image data as the image data is effective as described above, and the method for determining the image data when the image area is equal to or larger than the threshold is effective.
In the case of a full-color image forming apparatus, data of the image area ratio of four colors can be obtained. However, even if the area ratio of one color exceeds 10%, it is determined as image data.

Here, when the output image is image data, the control unit 150 determines whether or not the number counter that counts up the number of output sheets after the previous process control execution is larger than the image data number threshold (S3). If larger, process control is executed (S4).
In this way, when image adjustment is necessary when outputting image data, process control is executed before the start of image formation, so image quality can be kept high.
In addition, the image data number threshold value is set short so that the image quality does not change, so that the image data can be continuously output with the image quality being high. When the process control is executed, the number counter is cleared (S5).

  Next, or when the output image is determined to be text data in S2, image formation is started without executing process control (S6). By doing so, priority can be given to shortening the printing time in the case of text data, and priority can be given to image quality in the case of image data. After starting the image formation, the number counter is incremented (S7), and the image formation is terminated (S8).

After completion of image formation, it is determined whether or not there is a next print request (S9). If there is a print request, the process returns to the determination of whether or not the output image is image data.
If there is no print request after completion of image formation, it is determined whether or not the number counter exceeds the text data number threshold (S10). Here, the threshold value for the number of text data is set to a value larger than the threshold value for the number of image data, so that even if the image quality slightly deteriorates, process control is not executed unless a malfunction occurs in the machine (printer). If the number counter exceeds the text data number threshold value under this condition, process control is executed (S11), the number counter is cleared (S12), and the process ends.

By doing so, in the case of text data, the number of times of process control execution can be reduced, so that the printing time can be shortened. In addition, in order to determine whether or not to execute process control when there is no next print request, in the case of text data output, process control is not executed until the end of the print job, and the time can be further reduced.
By adopting the above configuration, it is possible to set the timing for executing process control with priority on image quality in the case of image data output, and speed in the case of text data output.

Whether the output data is image data or text data is determined based on whether the document type classified by the engine controller is text data or image data, not the image area ratio calculated from the dot count. (Second embodiment). Also in the present embodiment, operations such as process control similar to those shown in FIG.
Further, whether the data to be output is image data or text data may be determined based on the document type designated by the host computer (third embodiment). Also in the present embodiment, operations such as process control similar to those shown in FIG.

1 is a schematic front view of a printer as an image forming apparatus according to a first embodiment of the present invention. It is an enlarged schematic front view of a process cartridge corresponding to a yellow image. It is a control block diagram. It is a schematic diagram which shows the arrangement | positioning relationship of a reference | standard pattern image. It is a schematic diagram which shows the arrangement | positioning pitch of a photoconductive drum. It is a schematic diagram of the pattern block formed on an intermediate transfer belt. It is a flowchart which shows control operation.

Explanation of symbols

8 Intermediate transfer belt as image carrier 6 Process cartridge as patch pattern creation means 40 Reflective photosensor as means for detecting image density 150 Control unit as process control means

Claims (7)

A patch pattern creating means for creating a patch pattern on the image carrier, a means for detecting the image density of the patch pattern, and a process control means for feeding back the information on the detected image density to the image forming conditions, In an image forming apparatus that automatically executes process control under the following conditions:
An image forming apparatus characterized in that a condition for automatically executing process control is different depending on whether an output image is text data or image data. The image forming apparatus according to claim 1.
An image forming apparatus characterized in that the frequency of executing process control is higher when image data to be output is image data than when image data is output. The image forming apparatus according to claim 2.
An image forming apparatus, wherein when image data to be output is text data, process control is not executed before the start of image formation, but when image data is output, process control may be executed before the start of image formation. The image forming apparatus according to claim 2.
An image forming apparatus characterized in that an interval between execution of process control and execution of the next process control is shorter when outputting image data than when outputting text data. The image forming apparatus according to claim 1.
Whether the output image is text data or image data is determined based on the area ratio of the image portion calculated from the area of the image portion calculated from the image dot count and the area of the paper to be output. An image forming apparatus. The image forming apparatus according to claim 5.
The threshold of the area ratio of the image portion for determining whether the data is text data or image data is 3% to 30%. If the threshold is less than the threshold, it is determined that the data is text data, and is equal to or higher than the threshold. In this case, the image forming apparatus is characterized in that it is determined as image data. The image forming apparatus according to claim 1.
An image forming apparatus comprising: determining whether an output image is text data or image data based on a document type designated by an engine controller or a host computer.

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