Patent ID: 12259672

DETAILED DESCRIPTION

Hereinafter, an embodiment of the present disclosure will be described with reference to the attached drawings. It is noted that the following embodiment is an example of embodying the present disclosure and does not limit the technical scope of the present disclosure.

[Configuration of Image Forming Apparatus100]

First, a configuration of an image forming apparatus100according to the embodiment of the present disclosure will be described with reference toFIG.1andFIG.2.

It is noted that for convenience of descriptions, a vertical direction in a state where the image forming apparatus100is installed in a usable state (state shown inFIG.1) is defined as an up-down direction D1. In addition, a front-rear direction D2is defined with a surface of the image forming apparatus100on a left side of the diagram shown inFIG.1being a front surface (front side). In addition, a left-right direction D3is defined using the front surface of the image forming apparatus100in the installed state as a reference.

The image forming apparatus100is an image processing apparatus having a printing function for forming an image based on image data. Specifically, the image forming apparatus100is a multifunction peripheral having a plurality of functions including the printing function. It is noted that the image forming apparatus according to the present disclosure may also be a printer, a facsimile apparatus, or a copying machine that is capable of forming an image using electrophotography.

As shown inFIG.1andFIG.2, the image forming apparatus100includes an ADF (Auto Document Feed)1, an image reading portion2, an image forming portion3, a sheet feed portion4, an operation display portion5, a storage portion6, and a control portion7.

The ADF1conveys a document sheet an image of which is to be read by the image reading portion2. The ADF1includes a document sheet setting portion, a plurality of conveying rollers, a document sheet holder, and a sheet discharge portion.

The image reading portion2realizes a scanning function for reading an image on a document sheet. The image reading portion2includes a document sheet table, a light source, a plurality of mirrors, an optical lens, and a CCD (Charge Coupled Device).

The image forming portion3realizes the printing function. Specifically, the image forming portion3forms a color or monochrome image on a sheet supplied from the sheet feed portion4using electrophotography.

The sheet feed portion4supplies a sheet to the image forming portion3. The sheet feed portion4includes a sheet feed cassette, a manual feed tray, and a plurality of conveying rollers.

The operation display portion5is a user interface of the image forming apparatus100. The operation display portion5includes a display portion and an operation portion. The display portion displays various types of information in response to control instructions from the control portion7. The display portion is, for example, a liquid crystal display. The operation portion is used for inputting various types of information to the control portion7in accordance with user operations. The operation portion is, for example, a touch panel.

The storage portion6is a nonvolatile storage device. For example, the storage portion6is a nonvolatile memory such as a flash memory. It is noted that the storage portion6may also be an SSD (Solid State Drive) or an HDD (Hard Disk Drive).

The control portion7collectively controls the image forming apparatus100. As shown inFIG.2, the control portion7includes a CPU11, a ROM12, and a RAM13. The CPU11is a processor which executes various types of calculation processing. The ROM12is a nonvolatile storage device in which information such as control programs for causing the CPU11to execute various types of processing is stored in advance. The RAM13is a volatile or nonvolatile storage device which is used as a temporary storage memory (working area) for the various types of processing executed by the CPU11. The CPU11executes the various control programs stored in advance in the ROM12, to thus collectively control the image forming apparatus100.

It is noted that the control portion7may be a control portion provided separately from a main control portion that collectively controls the image forming apparatus100. Alternatively, the control portion7may be constituted by an electronic circuit such as an integrated circuit (ASIC).

[Configuration of Image Forming Portion3]

Next, a configuration of the image forming portion3will be described with reference toFIG.1toFIG.4. Herein,FIG.3is a cross-sectional view showing a configuration of an image forming unit24.

As shown inFIG.1, the image forming portion3includes a plurality of image forming units21to24, a laser scanning unit25, an intermediate transfer belt26, a secondary transfer roller27, a fixing device28, and a sheet discharge tray29. Further, the image forming portion3includes an optical sensor30shown inFIG.3andFIG.4.

The image forming unit21forms a Y (yellow) toner image. The image forming unit22forms a C (cyan) toner image. The image forming unit23forms an M (magenta) toner image. The image forming unit24forms a K (black) toner image. As shown inFIG.1, the image forming units21to24are arranged next to one other along the front-rear direction D2of the image forming apparatus100in the stated order of yellow, cyan, magenta, and black from the front side of the image forming apparatus100.

As shown inFIG.3, the image forming unit24includes a photoconductor drum31, a charging roller32, a developing device33, a primary transfer roller34, and a drum cleaning portion35. The image forming units21to23also have configurations similar to that of the image forming unit24. Moreover, each of the image forming units21to24includes a toner container36shown inFIG.1.

An electrostatic latent image is formed on a surface of the photoconductor drum31. For example, the photoconductor drum31includes a photosensitive layer31A formed of an organic photosensitive material. Upon receiving a rotational driving force supplied from a motor (not shown), the photoconductor drum31rotates in a rotation direction D4shown inFIG.3. Thus, the photoconductor drum31conveys an electrostatic latent image formed on the surface thereof. It is noted that the photosensitive layer31A may alternatively be formed by other photosensitive materials such as amorphous silicon.

Upon being applied with a preset charging voltage, the charging roller32charges the surface of the photoconductor drum31. For example, the charging roller32charges the surface of the photoconductor drum31to a positive polarity. Light that is emitted from the laser scanning unit25and is based on image data is irradiated onto the surface of the photoconductor drum31charged by the charging roller32. Thus, an electrostatic latent image is formed on the surface of the photoconductor drum31.

The developing device33develops the electrostatic latent image formed on the surface of the photoconductor drum31. The developing device33includes a pair of stirring members and a developing roller. The pair of stirring members stir developer that is stored inside the developing device33and contains toner and carriers. By this stirring, the toner and carriers contained in the developer are frictionally charged. For example, the toner contained in the developer is charged to a positive polarity by friction with the carriers. The developing roller draws the developer stirred by the pair of stirring members and conveys the developer to an opposing area between the developing roller and the photoconductor drum31. Moreover, upon being applied with a preset developing bias voltage, the developing roller supplies the toner conveyed to the opposing area to the photoconductor drum31. Thus, the toner is selectively supplied to an exposure area of the photoconductor drum31where light emitted from the laser scanning unit25has been irradiated, and thus the electrostatic latent image formed on the surface of the photoconductor drum31is developed. It is noted that the toner from the toner container36is supplied to the developing device33.

Upon being supplied with a preset primary transfer current, the primary transfer roller34transfers the toner image formed on the surface of the photoconductor drum31onto an outer circumferential surface of the intermediate transfer belt26. As shown inFIG.3, the primary transfer roller34is provided opposed to the photoconductor drum31with the intermediate transfer belt26interposed therebetween.

The drum cleaning portion35removes toner that has remained on the surface of the photoconductor drum31after the transfer of the toner image by the primary transfer roller34.

The laser scanning unit25emits light that is based on image data toward the surface of the photoconductor drum31of each of the image forming units21to24.

The intermediate transfer belt26is an endless belt member onto which the toner image that has been formed on the surface of the photoconductor drum31of each of the image forming units21to24is transferred. The intermediate transfer belt26is stretched by a drive roller, a tension roller, and the four primary transfer rollers34at a predetermined tension. By the drive roller rotating upon receiving a rotational driving force supplied from a motor (not shown), the intermediate transfer belt26rotates in a rotation direction D5shown inFIG.1andFIG.3. The intermediate transfer belt26carries a toner image to be transferred onto a sheet. The intermediate transfer belt26is an example of an image-carrying member according to the present disclosure.

The secondary transfer roller27transfers the toner image transferred onto the surface of the intermediate transfer belt26onto a sheet supplied from the sheet feed portion4.

The fixing device28fixes the toner image transferred onto the sheet by the secondary transfer roller27onto the sheet.

The sheet onto which the toner image has been fixed by the fixing device28is discharged onto the sheet discharge tray29.

The optical sensor30is used to sense a toner concentration of a toner image formed on the intermediate transfer belt26. As shown inFIG.3, the optical sensor30is disposed on a downstream side of the image forming unit24in the rotation direction D5of the intermediate transfer belt26and on an upstream side of the secondary transfer roller27in the rotation direction D5.

The optical sensor30is a so-called reflective optical sensor. As shown inFIG.4, the optical sensor30includes a light-emitting portion30A, a first light-receiving portion30B, and a second light-receiving portion30C.

The light-emitting portion30A emits light L1toward the intermediate transfer belt26. It is noted that inFIG.4, the light L1is indicated by a bold line with an arrow. For example, the light-emitting portion30A is a light-emitting element such as a light-emitting diode that emits light of a predetermined wavelength. It is noted that the light-emitting portion30A may also include a light guide member that guides light emitted from the light-emitting diode to the intermediate transfer belt26.

The first light-receiving portion30B receives regular reflection light L2out of light that is emitted from the light-emitting portion30A and is reflected by the intermediate transfer belt26, and outputs a sensing value corresponding to a received light amount. It is noted that inFIG.4, the regular reflection light L2is indicated by a broken line with an arrow. For example, the first light-receiving portion30B is a light-receiving element such as a phototransistor. The first light-receiving portion30B outputs an electric signal indicating a sensing value corresponding to the received light amount of the regular reflection light L2. The sensing value output from the first light-receiving portion30B is input to the control portion7.

The second light-receiving portion30C receives diffuse reflection light L3out of light that is emitted from the light-emitting portion30A and is reflected by the intermediate transfer belt26, and outputs a sensing value corresponding to a received light amount. It is noted that inFIG.4, the diffuse reflection light L3is indicated by a dotted line with an arrow. For example, the second light-receiving portion30C is a light-receiving element such as a phototransistor. The second light-receiving portion30C outputs an electric signal indicating a sensing value corresponding to the received light amount of the diffuse reflection light L3. The sensing value output from the second light-receiving portion30C is input to the control portion7.

Hereinafter, the first light-receiving portion30B and the second light-receiving portion30C may collectively be referred to as a “light-receiving portion30X”.

The control portion7senses a toner concentration of a toner image formed on the intermediate transfer belt26based on the sensing value input from the light-receiving portion30X. Specifically, the control portion7senses a toner concentration of a black toner image formed on the intermediate transfer belt26based on the sensing value input from the first light-receiving portion30B. In addition, the control portion7senses a toner concentration of a cyan, magenta, or yellow toner image formed on the intermediate transfer belt26based on the sensing value input from the second light-receiving portion30C. The configuration including the optical sensor30and the control portion7is an example of a toner concentration sensing apparatus according to the present disclosure.

Incidentally, in the image forming apparatus100, a surface condition of the intermediate transfer belt26changes along with an increase in the number of uses of the apparatus. When the surface condition of the intermediate transfer belt26changes, an amount of light that is emitted from the light-emitting portion30A and is reflected by the intermediate transfer belt26changes, to thus result in lowering of an accuracy of the control portion7in sensing a toner concentration of a toner image. In contrast, there is known, as the related art, an image forming apparatus which corrects, based on a sensing value that is output from the light-receiving portion30X and corresponds to light reflected by a region of the intermediate transfer belt26where a toner image is not formed, a sensing value that is output from the light-receiving portion30X and corresponds to light reflected by a toner image formed on the intermediate transfer belt26.

Herein, it is considered that the sensing value output from the light-receiving portion30X includes a first component corresponding to light reflected by the surface of the intermediate transfer belt26and a second component corresponding to light reflected by toner adhered onto the surface. Further, it is considered that even if the surface condition of the intermediate transfer belt26changes, the amount of light reflected by toner adhered onto the surface of the intermediate transfer belt26does not change.

However, in the image forming apparatus according to the related art described above, the first component and the second component included in the sensing value output from the light-receiving portion30X are not distinguished from each other, and a correction that is based on a sensing value that is output from the light-receiving portion30X and corresponds to light reflected by a region of the intermediate transfer belt26where a toner image is not formed, is carried out with respect to the entire sensing value. Therefore, in the image forming apparatus according to the related art described above, a toner concentration of a toner image cannot be sensed accurately.

In contrast, in the image forming apparatus100according to the embodiment of the present disclosure, it is possible to accurately sense a toner concentration of a toner image formed on the intermediate transfer belt26as will be described below.

[Configuration of Control Portion7]

Next, a configuration of the control portion7will be described with reference toFIG.2.

As shown inFIG.2, the control portion7includes a first acquisition processing portion51, a second acquisition processing portion52, and a third acquisition processing portion53.

Specifically, a specific control program for causing the CPU11of the control portion7to function as the respective portions described above is stored in advance in the ROM12of the control portion7. Then, the CPU11of the control portion7executes the specific control program stored in the ROM12to thus function as the respective functional portions described above. It is noted that some or all of the functional portions included in the control portion7may be constituted by an electronic circuit. Alternatively, the specific control program may be a program for causing a plurality of processors to function as the respective functional portions included in the control portion7.

The first acquisition processing portion51acquires a first sensing value that is output from the light-receiving portion30X and corresponds to light that is emitted from the light-emitting portion30A and is reflected by a first region of the intermediate transfer belt26where a toner image is not formed.

Specifically, the first acquisition processing portion51causes the light-emitting portion30A to emit light L1toward the first region. Moreover, the first acquisition processing portion51acquires the first sensing value output from the first light-receiving portion30B in accordance with the emission of the light L1by the light-emitting portion30A. In addition, the first acquisition processing portion51acquires the first sensing value output from the second light-receiving portion30C in accordance with the emission of the light L1by the light-emitting portion30A.

The second acquisition processing portion52acquires a second sensing value that is output from the light-receiving portion30X and corresponds to light that is emitted from the light-emitting portion30A and is reflected by a second region of the intermediate transfer belt26where a toner image has been formed.

Specifically, the second acquisition processing portion52forms a predetermined first specific toner image on the intermediate transfer belt26using the image forming unit24. The first specific toner image is a black toner image that is formed based on predetermined image data. Further, at a timing at which the first specific toner image formed on the intermediate transfer belt26is conveyed to an irradiation position of the light L1by the light-emitting portion30A, the second acquisition processing portion52causes the light-emitting portion30A to emit the light L1. Furthermore, the second acquisition processing portion52acquires the second sensing value that is output from the first light-receiving portion30B in accordance with the emission of the light L1by the light-emitting portion30A.

Further, the second acquisition processing portion52forms a predetermined second specific toner image on the intermediate transfer belt26using any of the image forming units21to23. The second specific toner image is a cyan, magenta, or yellow toner image that is formed based on predetermined image data. Further, at a timing at which the second specific toner image formed on the intermediate transfer belt26is conveyed to the irradiation position of the light L1by the light-emitting portion30A, the second acquisition processing portion52causes the light-emitting portion30A to emit the light L1. Furthermore, the second acquisition processing portion52acquires the second sensing value that is output from the second light-receiving portion30C in accordance with the emission of the light L1by the light-emitting portion30A.

Herein, in the image forming apparatus100, it is assumed that the sensing value output from the light-receiving portion30X is constituted by the first component corresponding to light reflected by the surface of the intermediate transfer belt26and the second component corresponding to light reflected by toner adhered onto the surface of the intermediate transfer belt26.

Also in the image forming apparatus100, a relationship between the first component and a component ratio of the second component in the sensing value output from the light-receiving portion30X is defined by a first relational expression that is determined based on the first sensing value acquired by the first acquisition processing portion51. For example, the first relational expression is a primary expression that is shown inFIG.5and indicated by the following Expression (1). It is noted that “Sb” inFIG.5and Expression (1) is a symbol that indicates the first component. Moreover, “Y” inFIG.5and Expression (1) is a symbol that indicates the component ratio of the second component in the sensing value output from the light-receiving portion30X. In addition, “Sg” inFIG.5and Expression (1) is a symbol that indicates the first sensing value acquired by the first acquisition processing portion51.
Sb=−Sg×Y+Sg(1)

Also in the image forming apparatus100, a relationship between the second component and the component ratio of the second component in the sensing value output from the light-receiving portion30X is defined by a second relational expression that is determined without using the first sensing value acquired by the first acquisition processing portion51. For example, the second relational expression is a primary expression that is shown inFIG.6and indicated by the following Expression (2). It is noted that “St” inFIG.6and Expression (2) is a symbol that indicates the second component. Moreover, “A” inFIG.6and Expression (2) is a coefficient indicating the sensing value obtained in a case where the component ratio of the second component in the sensing value output from the light-receiving portion30X is 100%. For example, the coefficient is acquired by forming a toner image that fully covers the surface of the intermediate transfer belt26and causing the light-receiving portion30X to output a sensing value corresponding to the toner image. Alternatively, the coefficient may be acquired by a simulation that is based on information such as light-emitting characteristics of the light-emitting portion30A, light-receiving characteristics of the light-receiving portion30X, a positional relationship among the light-emitting portion30A, the light-receiving portion30X, and the intermediate transfer belt26, a color of toner, a material of toner, a shape of toner, a size of toner, and the like.
St=A×Y(2)

Further, the sensing value output from the light-receiving portion30X can be expressed by the following Expression (3) using Expression (1) and Expression (2). It is noted that “Sout” in Expression (3) is a symbol that indicates the sensing value output from the light-receiving portion30X.
Sout=Sb+St=(−Sg×Y+Sg)+(A×Y)  (3)

Furthermore, by modifying Expression (3), the following Expression (4) with which the component ratio of the second component in the sensing value output from the light-receiving portion30X can be calculated is acquired.
Y=(Sout−Sg)/(A−Sg)  (4)

The third acquisition processing portion53uses a specific calculation formula that is determined based on the first relational expression and the second relational expression, and the second sensing value acquired by the second acquisition processing portion52, to acquire a component ratio of the second component in the second sensing value.

Specifically, the third acquisition processing portion53substitutes the first sensing value of the first light-receiving portion30B acquired by the first acquisition processing portion51and the second sensing value of the first light-receiving portion30B acquired by the second acquisition processing portion52into Expression (4) described above, to thus acquire the component ratio of the second component in the second sensing value. In addition, the third acquisition processing portion53substitutes the first sensing value of the second light-receiving portion30C acquired by the first acquisition processing portion51and the second sensing value of the second light-receiving portion30C acquired by the second acquisition processing portion52into Expression (4) described above, to thus acquire the component ratio of the second component in the second sensing value. In other words, the specific calculation formula is Expression (4) described above.

[Toner Concentration Sensing Processing]

Hereinafter, with reference toFIG.7, a toner concentration sensing method according to the present disclosure will be described along with toner concentration sensing processing executed by the control portion7in the image forming apparatus100. Herein, Step S11, Step S12. . . respectively represent numbers of processing procedures (steps) executed by the control portion7. For example, the toner concentration sensing processing is executed upon arrival of an execution timing of adjustment processing for adjusting an image forming condition of the image forming portion3.

The toner concentration sensing processing is processing for sensing a toner concentration of a black toner image. It is noted that processing for sensing a toner concentration of a cyan, magenta, or yellow toner image is similar to the toner concentration sensing processing described below, so descriptions thereof will be omitted.

<Step S11>

First, in Step S11, the control portion7forms the first specific toner image on the intermediate transfer belt26using the image forming unit24.

<Step S12>

In Step S12, the control portion7acquires the first sensing value that is output from the first light-receiving portion30B and corresponds to light that is emitted from the light-emitting portion30A and is reflected by the first region of the intermediate transfer belt26. Herein, the processing of Step S12is an example of a first acquisition step according to the present disclosure and is executed by the first acquisition processing portion51of the control portion7.

Specifically, the control portion7causes the light-emitting portion30A to emit light L1toward the first region. Further, the control portion7acquires the first sensing value that is output from the first light-receiving portion30B in accordance with the emission of the light L1by the light-emitting portion30A.

Herein, the first region is preferably a region in the vicinity of the first specific toner image formed in Step S11, that is, the second region. In other words, the emission timing of the light L1by the light-emitting portion30A is desirably a timing right before the first specific toner image formed in Step S11is conveyed to the irradiation position of the light L1by the light-emitting portion30A or right after the first specific toner image has passed through the irradiation position.

<Step S13>

In Step S13, the control portion7acquires the second sensing value that is output from the first light-receiving portion30B and corresponds to light that is emitted from the light-emitting portion30A and is reflected by the second region of the intermediate transfer belt26. Herein, the processing of Step S11and Step S13is an example of a second acquisition step according to the present disclosure and is executed by the second acquisition processing portion52of the control portion7.

Specifically, at a timing at which the first specific toner image formed on the intermediate transfer belt26is conveyed to the irradiation position of the light L1by the light-emitting portion30A, the control portion7causes the light-emitting portion30A to emit the light L1. In addition, the control portion7acquires the second sensing value that is output from the first light-receiving portion30B in accordance with the emission of the light L1by the light-emitting portion30A.

<Step S14>

In Step S14, the control portion7uses the specific calculation formula and the second sensing value acquired by the processing of Step S13, to acquire the component ratio of the second component in the second sensing value. Herein, the processing of Step S14is an example of a third acquisition step according to the present disclosure and is executed by the third acquisition processing portion53of the control portion7.

Specifically, the control portion7substitutes the first sensing value acquired by the processing of Step S12and the second sensing value acquired by the processing of Step S13into Expression (4) described above, to thus acquire the component ratio of the second component in the second sensing value. The component ratio of the second component in the second sensing value, that is acquired by the processing of Step S14, is treated as a value that indicates a toner concentration of the first specific toner image formed by the processing of Step S11.

<Step S15>

In Step S15, the control portion7outputs the component ratio of the second component in the second sensing value, that has been acquired by the processing of Step S14.

Specifically, the control portion7outputs the component ratio of the second component in the second sensing value, that has been acquired by the processing of Step S14, to an adjustment processing portion which executes the adjustment processing. The adjustment processing portion may be provided in the control portion7, or may be provided outside the control portion7.

The adjustment processing portion adjusts, for example, the image forming condition such as the developing bias voltage to be applied to the developing roller of the image forming unit24based on the component ratio of the second component in the second sensing value, that has been output by the processing of Step S15.

In this manner, in the image forming apparatus100, it is assumed that the sensing value output from the light-receiving portion30X is constituted by the first component and the second component. Further, the relationship between the first component and the component ratio of the second component in the sensing value output from the light-receiving portion30X is defined by the first relational expression that is determined based on the first sensing value. Further, the relationship between the second component and the component ratio of the second component in the sensing value output from the light-receiving portion30X is defined by the second relational expression that is determined without using the first sensing value. Then, in the image forming apparatus100, the specific calculation formula that is determined based on the first relational expression and the second relational expression, and the second sensing value are used to acquire the component ratio of the second component in the second sensing value. Thus, it is possible to acquire the first component based on the current surface condition of the intermediate transfer belt26, and acquire the second component irrespective of the current surface condition of the intermediate transfer belt26. Therefore, the toner concentration of the toner image formed on the intermediate transfer belt26can be sensed more accurately than in the conventional configuration in which a correction that is based on a sensing value that is output from the light-receiving portion30X and corresponds to light reflected by the region of the intermediate transfer belt26where a toner image is not formed, is carried out with respect to the entire sensing value output from the light-receiving portion30X.

It is noted that the first relational expression may alternatively be an n-th degree expression (n≥2). Also, the second relational expression may alternatively be an n-th degree expression (n≥2).

Furthermore, the optical sensor30may be used to sense a toner concentration of a toner image formed on the photoconductor drum31. In this case, the photoconductor drum31is an example of the image-carrying member according to the present disclosure.

It is to be understood that the embodiments herein are illustrative and not restrictive, since the scope of the disclosure is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds thereof are therefore intended to be embraced by the claims.