JP2010276641A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus configured to correct gradation in accordance with a fixing condition for thermal fixation. <P>SOLUTION: The image forming unit 40 of the image forming apparatus 1 is configured to form a toner image on a sheet of paper based on job data including image data, and a fixing unit 50 is configured to thermally fix the toner image formed on the sheet of paper. A CPU 2 is configured to correct the gradation of the image data in accordance with the fixing condition of the toner image which is thermally fixed by the fixing unit 50. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  The image data of the job executed in the image forming apparatus is subjected to gradation correction by various methods including shading correction and γ correction. An image is formed on the sheet based on the obtained correction data. This gradation correction is performed according to job execution conditions such as the type of paper and the paper surface on which an image is formed.

Patent Document 1 describes an image forming apparatus that changes gradation correction characteristics of a gradation correction circuit in accordance with a sheet surface on which an image is formed.
Patent Document 2 describes an image output device that corrects image forming conditions by reading a color patch attached to a recording medium with a light receiving element.
Patent Document 3 describes an image processing apparatus that efficiently updates a γ correction table corresponding to a plurality of screens.

JP-A-5-330148 JP-A-9-171279 JP 2005-96092 A

  Incidentally, in recent years, depending on the type of paper used in the image forming apparatus, stable fixing may not be achieved unless the thermal fixing process of the toner image attached to the paper is performed a plurality of times. For example, heat is not easily transmitted to thick paper, and the thermal fixing process of the toner image attached to the paper may be performed twice. Depending on the type of paper and the image forming surface, it is necessary to determine the fixing conditions for thermal fixing, that is, which side of the paper is to be thermally fixed.

  The manner of deformation of the image formed on the paper differs depending on the fixing conditions. When the thermal fixing of the toner image attached to the paper is performed a plurality of times, it is necessary to perform gradation correction according to the fixing conditions. However, the techniques described in Patent Documents 1 to 3 can perform correction according to paper characteristics and the like, but cannot perform gradation correction according to thermal fixing. In other words, the same gradation correction can be performed only when the number of times of fixing is one or two, and the gradation correction according to the fixing conditions of the thermal fixing cannot be performed.

  The present invention has been made in view of the above problems, and an object of the present invention is to perform gradation correction in accordance with fixing conditions for thermal fixing.

In order to solve the above-mentioned problem, the invention described in claim 1
An image forming apparatus that forms a toner image on a sheet based on job data including image data,
A fixing unit for thermally fixing the toner image formed on the paper;
A control unit that determines a fixing condition of heat fixing by the fixing unit for a toner image to be formed on a sheet based on the job data, and executes gradation correction of image data included in the job data according to the fixing condition When,
It is characterized by providing.

The invention according to claim 2 is the invention according to claim 1,
An image density sensor for measuring the density of the image formed on the paper;
The control unit forms a color patch on a sheet according to the fixing condition, and performs gradation correction of the image data based on an image density obtained by causing the image density sensor to measure the formed color patch. Execute.

The invention according to claim 3 is the invention according to claim 1 or 2,
When executing gradation correction during image formation, the control unit executes gradation correction for each of the image data in accordance with all fixing conditions included in the job data.

The invention according to claim 4 is the invention according to any one of claims 1 to 3,
The control unit determines from the job data whether or not the fixing unit performs fixing a plurality of times on one sheet, and determines that the fixing is performed a plurality of times according to a fixing condition relating to the number of times of fixing. The tone correction of the image data is executed.

  According to the present invention, it is possible to perform gradation correction according to the fixing conditions of thermal fixing.

1 is a front cross-sectional view illustrating an entire image forming apparatus according to an exemplary embodiment. FIG. 2 is a block diagram of the image forming apparatus illustrated in FIG. 1. It is a flowchart of the gradation correction process performed by CPU shown in FIG. It is a flowchart of the fixing pattern detection process performed by CPU shown in FIG. 3 is a flowchart of a paper feed pattern setting process executed by a CPU shown in FIG. It is an example of the patch image printed on paper. It is explanatory drawing at the time of reading a patch image in an image density sensor. It is a conceptual diagram for demonstrating gradation correction.

The configuration of the image forming apparatus according to the present invention will be described below with reference to the drawings.
FIG. 1 is a front sectional view of the image forming apparatus 1. As shown in FIG. 1, the image forming apparatus 1 includes an image reading unit 10, a paper tray 20, a transport unit 30, an image forming unit 40, a primary fixing unit 50 a, a secondary fixing unit 50 b, an image density sensor 60, and a discharge tray 70. Etc. The image forming apparatus 1 forms an image on a sheet, performs various post-processing, and discharges the sheet onto a discharge tray 70.

  The image reading unit 10 includes an ADF (Auto Document Feeder), a scanner, and the like, reads an image of a document, and generates image data. Various types of paper are stored in the paper tray 20, and an image is formed on the paper based on job data received from the image reading unit 10 or an externally connected personal computer.

  The conveyance unit 30 includes a conveyance unit 30a for conveying the paper stored in the paper tray 20 to the image forming unit 40, a conveyance unit 30b for conveying the image-formed paper to the primary fixing unit 50a, and duplex printing. A transport unit 30c, which is a transport unit for performing printing, and a transport unit 30d for discharging paper to the discharge tray 70 via the secondary fixing unit 50b and the image density sensor 60.

  The image forming unit 40 is composed of a photosensitive drum, a YMCK four-color toner bottle, and the like, and forms a toner image on a sheet by an electrophotographic process based on job data on the sheet supplied via the conveying unit 30a. To do. Job data including image data is input from the image reading unit 10, an operation unit 5 described later, or a personal computer (not shown) via a network. Information for identifying single-sided printing / double-sided printing, information for identifying the fixing unit 50 to be used, and the like are included. The image forming unit 40 performs image formation based on correction data obtained by performing various gradation corrections on the image data instructed to form an image under the control of the CPU 2.

  The toner image attached to the sheet by the image forming unit 40 is fixed by being heated by the primary fixing unit 50a or the secondary fixing unit 50b. In the case of a job for duplex printing, the sheet on which one side is fixed by the primary fixing unit 50a is reversed by the conveyance unit 30b, and image formation on the back side is executed by the image forming unit 40. The toner image attached to the back surface of the sheet is fixed by the primary fixing unit 50a.

  The primary fixing unit 50a thermally fixes the toner image formed on the paper P conveyed via the conveyance unit 30b. The secondary fixing unit 50b thermally fixes the toner image formed on the paper P conveyed via the conveyance unit 30c. Under the control of the CPU 2 to be described later, the fixing conditions are determined based on the job data, and the fixing process of the primary fixing unit 50a and the secondary fixing unit 50b is executed. The fixing condition in the present embodiment is that the primary fixing unit 50a and the secondary fixing unit 50b are used, and “single side” that is single-sided printing, “double-sided” that is double-sided printing, and only the primary fixing unit 50a are used. There is “primary fixing” in which heat fixing is performed, or “secondary fixing” in which heat fixing is performed using the primary fixing unit 50a and the secondary fixing unit 50b.

  The image density sensor 60 includes a light emitting diode, a light receiving diode, and the like, measures the density of the image formed on the sheet based on the amount of reflected light, and outputs the read density signal to the CPU 2. In the present embodiment, it is possible to measure the density of four colors of YMCK.

  The discharge tray 70 stacks sheets on which images are formed.

  FIG. 2 shows a block diagram of a control system of the image forming apparatus 1. As shown in FIG. 2, the image forming apparatus 1 includes a CPU 2, a RAM (Random Access Memory) 3, a storage unit 4, an operation unit 5, an image reading unit 10, an image forming unit 40, a fixing unit 50, an image density sensor 60, and the like. Consists of The description of what has been described with reference to FIG. 1 will be omitted below.

  The CPU 2 performs various calculations in cooperation with the control program stored in the storage unit 4 and controls the operation of each unit of the image forming apparatus 1. The CPU 2 controls image formation of the image forming unit 40 based on the input job data, or causes the primary fixing unit 50a and the secondary fixing unit 50b to perform fixing processing.

  The RAM 3 functions as a work area for temporarily expanding the control program and various data stored in the storage unit 4.

  The storage unit 4 includes a large-capacity memory and the like, and stores a control program, parameters, and the like. The storage unit 4 stores print conditions (details will be described later) necessary for tone correction in association with the paper feed pattern.

  The operation unit 5 includes operation keys, a touch panel, and the like. Various kinds of information for job execution and an input instruction for executing a gradation correction process described later can be input via the operation unit 5. It is also possible to specify a fixing condition through an operation screen (not shown) together with an input operation of an instruction to execute gradation correction processing from the operation unit 5. The operation unit 5 outputs an operation signal corresponding to the operation of the operation key or the like to the CPU 2.

  The fixing unit 50 includes the primary fixing unit 50a and the secondary fixing unit 50b described above.

Next, the operation of the image forming apparatus 1 will be described.
FIG. 3 shows a flowchart of the tone correction processing executed in the image forming apparatus 1 in the present embodiment. The gradation correction process is executed in cooperation with the CPU 2 and a program stored in the storage unit 4 when a job execution is instructed to the CPU 2. Note that the gradation correction process may be executed at a predetermined timing, and is not limited to when the job starts. For example, it may be executed when a predetermined signal is input from the operation unit 5 or may be periodically executed at a predetermined cycle.

  First, as shown in FIG. 3, a fixing pattern detection process is executed (step S1).

  FIG. 4 shows a flowchart of the fixing pattern detection process executed in step S1. As shown in FIG. 4, an area for storing information related to the fixing condition is created in the RAM 3, and “one side” is added to the fixing condition (step S11).

  Next, based on the setting value stored in the storage unit 4, it is determined whether or not to perform gradation correction during printing (that is, during job execution) (step S12). This set value is stored in advance in the storage unit 4 by an input from the operation unit 5 or the like.

  If it is determined that gradation correction is to be performed during printing (step S12; YES), it is determined whether this printing is duplex printing (step S13). Specifically, when gradation correction processing is executed during job execution, it is determined whether or not double-sided printing is included in the job to be executed based on the job data, and input from the operation unit 5 When the gradation correction processing is executed, information for identifying whether or not double-sided printing is performed is input by operating the operation unit 5 on an operation screen (not shown) or the like, and this input signal is used for determination.

  When it is not determined that gradation correction is to be performed during printing (step S12; NO), or when it is determined that double-sided printing is performed (step S13; YES), both sides are added to the fixing condition (step S14).

When it is not determined that the duplex printing is performed (step S13; NO), it is determined whether the image forming apparatus 1 has the secondary fixing unit 50b (step S15).
When it is determined that there is the secondary fixing unit 50b (step S15; YES), it is determined whether or not gradation correction is performed during printing (step S16).

  When it is determined that gradation correction is to be performed during printing (step S16; YES), it is determined whether to use the secondary fixing unit 50b (step S17). The determination in step S17 is performed in the same manner as the determination in step S13.

  If it is determined that the secondary fixing unit 50b is to be used (step S17; YES), “secondary” is added to the fixing condition (step S18).

  On the other hand, when it is not determined that the secondary fixing unit 50b is present (step S15; NO), or when it is not determined that the secondary fixing unit 50b is used (step S17; NO), the process returns to FIG. Is executed (step S2).

  FIG. 5 shows a flowchart of the paper feed pattern setting process executed in step S2. As shown in FIG. 5, first, information indicating the paper feed pattern setting is developed in a predetermined area of the RAM 3, and single-sided output is set (step S21). The paper feed pattern setting is information for identifying a patch image to be formed on a paper.

  Next, it is determined what is set in the fixing conditions stored in the RAM 3 (step S22).

  When “single side” is set as the fixing condition and “secondary” is not set (step S22; no single side AND secondary fixing), the single side output is set as the paper feed pattern setting (step S23).

  If “single side” is set as the fixing condition and “secondary” is set (step S22; with single side AND secondary fixing), the output for secondary side is set as the paper feed pattern setting (step S24). .

  When “double-sided” is set as the fixing condition and “secondary” is not set (step S22; double-sided AND no secondary fixing), double-sided surface output is set as the paper feed pattern setting (step S25), and double-sided The rear surface output is set (step S26).

  If “double-sided” is set as the fixing condition and “secondary” is set (step S22; double-sided AND secondary-fixed), the secondary-side surface output is set as the paper feed pattern setting (step S27). Then, the back side output for the secondary both sides is set (step S28).

  In steps S23 to S28, a plurality of paper feed patterns are set depending on the fixing conditions. For example, one job may include one that performs secondary fixing by single-sided printing and one that performs primary fixing by two-sided printing. In this case, “secondary single-sided output setting” is set in the paper feed pattern in step S24, and “double-sided front surface output setting” and “double-sided backside output setting” are set in the paper feeding pattern in steps S25 and S26. Is done.

  Returning to FIG. 3, the paper tray 20 is instructed to feed paper (step S3). Patch image data corresponding to the paper feed pattern stored in the RAM 3 is generated by reading from the storage unit 4 (step S4), and the image forming unit 40 indicates that this patch image is formed on the fed paper. To form a patch image on the paper (step S5).

  FIG. 6 shows an example of the paper P on which the patch image is formed. As shown in FIG. 6, the patch image formed on the paper P is composed of gradation patches Y, M, C, and K. The gradation patches Y, M, C, and K are printed in yellow (Y), magenta (M), cyan (C), and black (K), respectively, and each has a predetermined gradation (for example, 36 gradations). The band is printed.

  Next, the image density sensor 60 detects the density of the patch image formed on the paper for each of the YMCKs (step S6).

  FIG. 7 is a schematic diagram when the image density sensor 60 detects the paper P on which the patch image is formed. As shown in FIG. 7, when the image density sensor 60 is installed in a direction perpendicular to the conveyance direction of the conveyance unit 30d and the paper P is conveyed, the densities of the gradation patches Y to K are read and output to the CPU 2. To do.

  The print condition corresponding to the paper feed pattern from which the patch image data is read in step S4 is updated (step S7).

  FIG. 8 shows an example of the updated print condition. A gradation curve C1 shown in FIG. 8 is a gradation curve (any one of gradation patches Y to K) obtained by reading the paper P on which the patch image is printed by the image density sensor 60. When a job is executed in the image forming unit 40, tone correction is executed based on the tone curve C1 and an ideal tone curve C2 stored in the storage unit 4 in advance. This correction method is arbitrary, and various known techniques can be applied. For example, the gradation curve C3 subjected to gradation curve density correction is calculated with the gradation curve C1 being line-symmetrical with respect to the gradation curve C2, and the input input to the CPU 2 when the job is executed. Image formation is performed by converting the image density (that is, image data read by the image reading unit 10 or image data received via the network) into a corresponding output image density.

Next, it is determined whether or not there is a paper feed pattern that does not output a patch image on paper (paper pattern output remaining) (step S8). If it is determined that there is (step S8; YES), the process returns to step S3, and the paper tray 20 is instructed to feed paper again.
If it is not determined that there is any (step S8; NO), the process ends.

  As described above, according to the image forming apparatus of the present embodiment, it is possible to perform gradation correction according to the fixing condition of the thermal fixing by the fixing unit, and to fix the toner image formed on the paper. Image formation can be executed based on image data that has undergone tone correction to be corrected.

  Further, by performing image formation using color patches, it is possible to perform gradation correction of four colors of CMYK, and more accurate image formation can be performed. Even when there are a plurality of fixing units, correction according to fixing conditions can be performed.

  Note that the description in the present embodiment described above is an example of a suitable image forming apparatus according to the present invention, and the present invention is not limited to this. For example, although the number of fixing units is two (primary fixing unit and secondary fixing unit), it may be any predetermined number, and is not limited thereto. The number of fixing units may be three, and in this case as well, the printing conditions may be updated so that the fixing pattern corresponding to the fixing conditions is similarly determined by the fixing pattern detection processing of the gradation correction processing. .

  As other computer-readable media other than the storage unit in the present embodiment, a non-volatile memory such as a flash memory such as an SD (Secure Digital) card or a USB (Universal Serial Bus) memory, a CD-ROM, or the like It is possible to apply a portable recording medium. It is also possible to provide various data such as program data and audio data according to the present invention over a carrier wave via a communication line.

  In addition, the detailed operation of the image forming apparatus can be changed as appropriate without departing from the spirit of the present invention.

1 Image forming apparatus 2 CPU
3 RAM
4 storage unit 5 operation unit 10 image reading unit 20 paper tray 30 transport unit 40 image forming unit 50 fixing unit 50a primary fixing unit 50b secondary fixing unit 60 image density sensor 70 discharge tray

Claims (4)

An image forming apparatus that forms a toner image on a sheet based on job data including image data,
A fixing unit for thermally fixing the toner image formed on the paper;
A control unit that determines a fixing condition of heat fixing by the fixing unit for a toner image to be formed on a sheet based on the job data, and executes gradation correction of image data included in the job data according to the fixing condition When,
An image forming apparatus comprising: An image density sensor for measuring the density of the image formed on the paper;
The control unit forms a color patch on a sheet according to the fixing condition, and performs gradation correction of the image data based on an image density obtained by causing the image density sensor to measure the formed color patch. The image forming apparatus according to claim 1, wherein:   3. The control unit according to claim 1, wherein, when performing gradation correction during image formation, the control unit executes gradation correction of each of the image data according to all fixing conditions included in the job data. Image forming apparatus.   The control unit determines from the job data whether or not the fixing unit performs fixing a plurality of times on one sheet. The image forming apparatus according to claim 1, wherein gradation correction of the image data is executed.

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