Patent Grant
10437182
The entire disclosure of Japanese patent Application No. 2017-215503, filed on Nov. 8, 2017, is incorporated herein by reference in its entirety.
The present invention relates to an image forming apparatus and a control method of the image forming apparatus. More specifically, the present invention relates to an image forming apparatus including a fixing apparatus for fixing a toner image on a sheet, and a control method of the image forming apparatus.
Examples of an electrophotographic image forming apparatus include a multi function peripheral (MFP) including a seamier function, a facsimile function, a copying function, a function as a printer, a data communication function, and a server function, a facsimile machine, a copying machine, a printer, and the like.
An image forming apparatus forms an image on a sheet generally by the following method. The image forming apparatus forms an electrostatic latent image on an image carrier and develops the electrostatic latent image using a developing apparatus to form a toner image. Next, the image forming apparatus transfers the toner image to the sheet, and fixes the toner image on the sheet by the fixing apparatus. Some image forming apparatuses form a toner image on a photoreceptor, transfer the toner image to an intermediate transfer belt using a primary transfer roller, and secondarily transfer the toner image on the intermediate transfer belt to a sheet using a secondary transfer roller.
The fixing apparatus includes a heating member that is heated by a heater and a pressure member that forms a fixing nip between the pressure member and the heating member by pressing the heating member. The heating member comes into contact with a front side of the sheet (a surface on which the toner image to be fixed is formed). The pressure member comes into contact with a back side of the sheet (a surface opposite from the surface on which the toner image to be fixed is formed).
As a technique relating to a fixing apparatus, for example, JP 2012-133034 A or the like discloses a technique for preventing scratches from being generated on a surface layer of a fixing roller due to adhesion of sheet dust to the surface layer of the fixing, roller. JP 2012-133034 A discloses a technique of forming a cleaning image pattern for removing foreign matters adhered to a heating member, in a tip end margin portion or a rear end margin portion of a sheet in a conveyance direction, and heating this sheet by a fixing apparatus. In this technique, the number of image dots in the sheet conveyance direction is counted and integrated, the length in the conveyance direction of the sheet passing through the fixing apparatus is counted and integrated. When a count value of the number of dots with respect to a count value of the length of the sheet in the conveyance direction is equal to or less than a preset set value, the cleaning image pattern is formed in the margin portion in the sheet conveyance direction at the position corresponding to the number of dots that is equal to or less than the set value.
The inventors of the present application have found that, when the identical images are consecutively printed on a plurality of sheets, linear stains along a Sheet conveyance direction are generated on a surface of a pressure member, the stains are transferred also to a heating member, as a result, the stains adhere to both surfaces of the sheet, and the image quality deteriorates.
In recent years, types of sheet used in an image forming apparatus are diverse. Among areas where an image forming apparatus is used, there are areas where a sheet with high whiteness is preferably used. As a method for improving whiteness of a sheet, there are a method of bleaching pulp, a method of increasing calcium carbonate contained in raw materials, and the like. From the viewpoint of cost reduction of a sheet, as a method for improving whiteness of a sheet, there is a tendency to employ the method of increasing calcium carbonate rather than the method of bleaching. The deterioration in image quality described above is conspicuous particularly when printing is performed using a sheet prepared by increasing calcium carbonate.
The present invention is for solving the problem described above and an object of the present invention is to provide an image forming apparatus and a control method of the image forming apparatus capable of suppressing degradation of image quality.
To achieve the abovementioned object, according to an aspect of the present invention, an image forming apparatus reflecting one aspect of the present invention comprises: a fixing apparatus comprising a heating member that is heated by a heater and a pressure member that forms a fixing nip between the pressure member and the heating member by pressing the heating member, the fixing apparatus conveying a sheet on which a toner image is formed in a predetermined conveyance direction while gripping the sheet with the fixing nip to fix the toner image on the sheet; and a supplier that, when toner images of a plurality of images including non-image regions overlapping each other are consecutively fixed by the fixing apparatus, supplies a cleaning sheet on which a cleaning image is formed on one surface, to the fixing nip in a state where the one surface faces the pressure member, the cleaning image including the toner image at least in a part of a region corresponding to the non-image regions overlapping each other, wherein the non-image regions are regions extending along the conveyance direction from an upstream side end in the conveyance direction in an image to a downstream side end in the conveyance direction, and not including a toner image having a length of equal to or more than a first value in the conveyance direction.
The advantages and features provided by one or more embodiments of the invention will become more fully understood from the detailed description given hereinbelow and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention:
Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments.
In the following embodiments, a case where an image forming apparatus is an MFP will be described. The image forming apparatus may be a facsimile machine, a copying machine, a printer, or the like, in addition to the MFP.
First, a configuration of an image forming apparatus in the present embodiment will be described.
Referring to
The sheet conveyance unit 10 conveys a sheet M along conveyance paths TR1 and TR2. The sheet conveyance unit 10 includes a sheet feed tray 11, a sheet feed roller 12, a plurality of conveyance rollers 13, a sheet discharge roller 14, a sheet discharge tray (sheet accommodation unit) 15, and a manual feed tray 16. The sheet feed tray 11 accommodates the sheet M (an example of a recording material) for forming an image. A plurality of sheet feed trays 11 may be used. The sheet feed roller 12 is provided between each of the sheet feed tray 11 and the manual feed tray 16 and the conveyance path TR1. Each of the plurality of conveyance rollers 13 is provided along the conveyance paths TR1 and TR2. The sheet discharge roller 14 is provided at the most downstream portion of the conveyance path TR1. The sheet discharge tray 15 is provided at the top of a main body of the image forming apparatus. The manual feed tray 16 is attached to a side surface of the main body of the image forming apparatus 1 and is used for placing a manual feed sheet or a cleaning sheet which will be described later.
The toner image forming unit 20 composes images of four colors of yellow (Y), magenta (M), cyan (C), and black (K) by a so-called tandem system to form a toner image on a sheet. The toner image forming unit 20 includes an image forming unit 21 for each color of Y, M, C, and K, an intermediate transfer belt 22, a primary transfer roller 23 for each color of Y, M, C, and K, a secondary transfer roller 24, and an exposure apparatus 27.
The image forming unit 21 for each color of Y, M, C, and K includes a photosensitive drum 25, a charging roller 26, a developing apparatus 28, and the like. The photosensitive drum 25 is driven to rotate in a direction indicated by an arrow α in
The intermediate transfer belt 22 is provided above the image forming unit 21 for each color of Y, M, C, and K. The intermediate transfer belt 22 is annular and spans a rotating roller. The intermediate transfer belt 22 is driven to rotate in a direction indicated by an arrow β in
The fixing apparatus 30 fixes a toner image on a sheet by conveying the sheet carrying the toner image along the conveyance path TR1 while gripping the sheet.
The control unit 60 controls the overall operation of the image forming apparatus 1. The control unit 60 includes an image processing unit 61, a non-image region extraction unit 62, a cleaning control unit 63, a storage unit 64, and the like. The control unit 60 includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and the like.
Under the control of the control nit 60, the operation panel 70 displays various information and accepts various operations.
The image reading unit 80 reads an image of a document.
The image forming apparatus 1 rotates the photosensitive drum 25 to charge a surface of the photosensitive drum 25 with the charging roller 26. The image forming apparatus 1 exposes the charged surface of the photosensitive drum 25 in accordance with a separation signal for each color of image data by the exposure apparatus 27 to form an electrostatic latent image on the surface of the photosensitive drum 25.
Next, the image forming apparatus 1 supplies a toner from the developing apparatus 28 to the photosensitive drum 25 on which the electrostatic latent image has been formed, develops the toner image, and forms a toner image on the surface of the photosensitive drum 25.
Next, the image forming apparatus 1 sequentially transfers the toner image formed on the photosensitive drum 25 to the surface of the intermediate transfer belt 22 by using the primary transfer roller 23 (primary transfer). In the case of a full-color image, a toner image obtained by composing toner images of each color of Y, M, C, and K is formed on the surface of the intermediate transfer belt 22.
Subsequently, the image forming apparatus 1 conveys the toner image formed on the surface of the intermediate transfer belt 22 to a position facing the secondary transfer roller 24 by rotating the intermediate transfer belt 22.
Meanwhile, in the image forming apparatus 1, the sheet M placed on the manual feed tray 16 or the sheet M accommodated in the sheet feed tray 11 is fed by the sheet feed roller 12 and conveyed by each of the plurality of conveyance rollers 13 along the conveyance path TR1 to a conveyance direction AR1. The image forming apparatus 1 corrects tilt of the sheet M by a resist roller pair 13a of the conveyance roller 13 and then guides the sheet M between the intermediate transfer belt 22 and tire secondary transfer roller 24. Then, the image knitting apparatus 1 transfers the toner image formed on the surface of the intermediate transfer belt 22 to the front side of the sheet M by the secondary transfer roller 24.
The image forming apparatus 1 guides the sheet M holding the toner image (unfixed image) to the fixing apparatus 30, and fixes the toner image on the front side of the sheet M by the fixing apparatus 30. Thereafter, the image forming apparatus 1 discharges the sheet M on which the toner image has been fixed, to the sheet discharge tray 15 by the sheet discharge roller 14.
In the case of duplex printing, the image forming apparatus 1 switches back the sheet M on which the toner image has been formed on the front side thereof with the discharge roller 14, and guides the sheet M into the conveyance path TR2. The image forming apparatus 1 conveys the sheet M in the conveyance direction AR1a and guides the sheet M again into the conveyance path TR1 from a merging position with the conveyance path TR2 provided on the downstream side of the secondary transfer roller 24 in the conveyance path Mt. Thereafter, the image forming apparatus 1 forms a toner image on the back side of the sheet M by the toner image forming unit 20, fixes the toner image on the back side of the sheet M by the fixing apparatus 30, and discharges the sheet M to the sheet discharge tray 15 by the sheet discharge roller 14.
The image formed by the image forming apparatus 1 may be an image based on a print signal received from an external apparatus or may be an image of a document read by the image reading unit 80.
As an example of the performance of the image forming apparatus 1, the process speed of the image forming apparatus 1 is 325 mm/sec, the printing speed in monochrome prating is 75 sheets min, and the printing speed in color printing is 65 sheets/min.
Referring to
The fixing belt 31 is an endless thin-walled nickel (Ni) belt, and is wound around the outer circumference of the fixing roller 32. The fixing belt 31 includes, for example, a cylindrical nickel (Ni) layer having a thickness of 35 μm to 45 μm, a copper (Cu) layer provided on the outer circumference of the Ni layer and having a thickness of 9 μm to 11 μm, a Ni layer provided on the outer circumference of the Cu layer and having a thickness of 1 μm, a silicone rubber layer provided on the outer periphery thereof and having a thickness of 120 μm to 190 μm, and a release layer provided on the outer circumference of the silicone rubber layer with an adhesive layer interposed therebetween and formed of a fluororesin (PFA) tube having a thickness of 30 μm to 45 μm.
The fixing roller 32 has a cylindrical shape.
The heater 33 is an induction heating (IH) heater, and is provided in the vicinity of the fixing belt 31. The heater 33 generates a magnetic flux and heats the fixing belt 31 by induction heating.
The pressure roller 34 presses the fixing belt 31 to form the fixing nip NP between the pressure roller 34 and the fixing belt 31. The pressure roller 34 is pressed against the fixing roller 32 by pressure applier (not shown). The pressure roller 34 has a cylindrical shape and has a diameter of 40 mm. The pressure roller 34, includes a metal core having a hollow cylindrical shape and formed of metal, a silicone rubber layer provided on the outer circumference of the metal core with an adhesive layer interposed therebetween and having a thickness of 6 mm, a release layer provided on the outer circumference of the silicone rubber layer, formed of a PFA resin tube, and having a thickness of 40 μm, and a gear provided at one end along a central axis R of the pressure roller 34 and transmitting power to the pressure roller 34.
The pressure roller 34 is rotated in a direction indicated by an arrow AR11 by power from a drive source (not shown). The fixing belt 31 and the fixing roller 32 rotate in a direction indicated by an arrow AR12 following the pressure roller 34.
The counter (discharge mechanism sensor) 35 is provided, for example, on the downstream side of the fixing nip NP. The counter 35 counts the number of sheets passing through the fixing nip NP.
Referring to
The image IM formed on the front side of the sheet M is divided into the image region R1 and the non-image region R2. The image region R1 is a region extending along the conveyance direction AR1 from an upstream side end e1 in the conveyance direction AR1 in the image IM to a downstream side end e2 in the conveyance direction AR1, and including a toner image PP1 having a length of equal to or larger than a first value (for example, 40 to 60 mm) in the conveyance direction AR1.
The non-image region R2 is a region extending along the conveyance direction AR1 from an upstream side end e1 in the conveyance direction MU in the image MI to a downstream side end e2 in the conveyance direction AR1, and not including a toner image PP1 having a length of equal to or larger than a first value in the conveyance direction AR1.
Here, the region R2a in the image IM is a region extending along the conveyance direction AR1 from the upstream side end et in the conveyance direction AR1 in the image IM to the downstream side end e2 in the conveyance direction AR1. The region R2a includes a toner image PP1a that is a part of the toner image PP1. A length W (an example of the first value) of the toner image PP1a in the conveyance direction AR1 is less than the first value. Therefore, the region R2a is classified as the non-image region R2.
It should be noted that the non-image region R2 may be defined as a region extending along the conveyance direction AR1 from an upstream side end e1 in the conveyance direction AR1 in the image IM to a downstream side end e2 in the conveyance direction AR1, and not including a toner image at all. In this case, the region R2a is classified as the image region R1 instead of the non-image region R2.
In the image IM, the image region R1 and the non-image region R2 are alternately arranged along a longitudinal direction AR2 of the fixing nip NP. The longitudinal direction AR2 of the fixing nip NP is a direction orthogonal to the conveyance direction AR1.
The inventors of the present application found that a phenomenon in which stains adhere to both sides of a sheet and image quality deteriorates occurs in a case where toner images of a plurality of images including non-image regions R2 overlapping each other (the plurality of images in this case may be identical images or images different from each other) are consecutively fixed by the fixing apparatus 30.
Referring to
Referring to
Referring to
When toner images of n images (n is an integer of 2 or more) including non-image regions overlapping each other are consecutively fixed by the fixing apparatus 30, the image forming apparatus 1 supplies the cleaning sheet to the fixing nip NP with its front side facing the pressure roller 34 by using the sheet conveyance unit 10 (an example of a supplier) so that the image quality degradation described above is prevented.
Referring to
When the non-image region indicated by the non-image region position data JM does not exist (in the case where there is no overlapping non-image region in the most recently printed images), the non-image region extraction unit 62 stores the extracted non-image region R2 of the image IM1 as new non-image region position data JM1 in the storage unit 64 (updating the non-image region position data JM to the non-image region position data JM1).
Referring to
Referring to
The fact that the count value of the counter 35 reaches n sheets means that toner images of n images including non-image regions overlapping each other are consecutively fixed by the fixing apparatus 30. When the count value of the counter 35 reaches a sheets, the cleaning control unit 63 (an example of the image former) forms the cleaning image on the front side of the sheet on the basis of the non-image region position data JM stored in the storage unit 64, thereby making a cleaning sheet. The cleaning control unit 63 clears the count value of the counter 35. The sheet conveyance unit 10 switches back the made cleaning sheet with the discharge roller 14 and conveys the cleaning sheet along the conveyance path TR2, thereby reversing the front and back sides of the cleaning sheet and guiding the cleaning sheet again to the conveyance path TR1. As a result, the cleaning sheet is supplied to the fixing nip NP while the front side of the cleaning sheet (the surface on which the cleaning image is formed) faces the pressure roller 34.
Referring to
As an exceptional handling of the toner image PP2 included in the cleaning image CIM, a plurality of image regions Rth having a length of the fixing nip NP of equal to or less than L1 in the longitudinal direction AR2 exist in the A2 part in the non-image region position data JM (
As an exceptional handling of the toner image PP2 included in the cleaning image CIM, a non-image region R2b exists in an end portion of the fixing nip NP in the longitudinal direction AR2 in the image region of the non-image region position data JM. The toner image PP2 included in the cleaning image CIM may not be formed in the region corresponding to the non-image region R2b. This is because the possibility of stain generation is low in the region of the surface of the pressure roller 34 corresponding to the non-image region R2b.
It should be noted that the toner image PP2 included in the cleaning image CIM is not limited to the case of being formed in the region determined by the method described with reference to
Referring to
As shown in
Referring to
Referring to
In step S103, when it is determined that a print signal has been received (YES in S103), the control unit 60 determines whether the image based on the print signal is an image including toner images aligned in the conveyance direction (S105).
If it is determined in step S105 that the image based on the print signal is an image including toner images aligned in the conveyance direction (YES in S105), the control unit 60 extracts a non-image region from the image (S107), and updates non-image region position data on the basis of the extracted non-image region (S109). Subsequently, the control unit 60 determines whether a non-image region is included in the updated non-image region position data (S111).
If it is determined in step S105 that the image based on the print signal is not an image including toner images aligned in the conveyance direction AR1 (NO in S105), or if it is determined in step S111 that the non-image region position data JM after updating does not include a non-image region (NO in S111), the control unit 60 proceeds to the process of step S123.
If it is determined in step S111 that a non-image region is included in the updated non-image region position data (YES in S111), the control unit 60 acquires the count value from the counter 35 (S113), and determines whether the count value has reached n (sheets) (S115).
In step S115, if it is determined that the count value has not reached n (sheets) (NO in S115), the control unit 60 proceeds to the processing in step S101.
In step S115, if it is determined that the count value has reached n (sheets) (YES in S115), the control unit 60 generates a cleaning image based on the non-image region indicated by the non-image region position data (S117). Next, the control unit 60 prints the generated cleaning image on the sheet to prepare the cleaning sheet (S119), and discharges the cleaning sheet through a reverse path (conveyance path TR2) (S121). Thereafter, the control unit 60 clears the non-image region position data and the count value (S123), and proceeds to the processing of step S101.
According to the present embodiment, when the cleaning sheet on which the cleaning image is formed is supplied to the fixing nip NP, the fogging toner and the sheet dust adhered to the surface of the pressure roller 34 are moved to the cleaning sheet by the adhesive force of the cleaning image and is removed. As a result, stains of the pressure roller 34 can be removed, stains of the sheet can be suppressed, and deterioration of image quality can be suppressed. Since it is unnecessary to provide a cleaning member for a new pressure roller 34, so complication of the apparatus configuration can be avoided.
In JP 2012-133034 A, a cleaning image pattern is formed in a blank portion at a predetermined timing irrespective of whether or not a plurality of printed images include non-image regions overlapping each other. For this reason, a cleaning image pattern different from the image desired by the user is formed in the blank space at unnecessary timing on a sheet, and it is impossible to sufficiently prevent deterioration of the image quality.
Referring to
When viewing the message displayed on the operation panel 70, the user of the image forming apparatus 1 places the cleaning sheet CRM (
Upon receipt of an execution instruction of sheet passing through the operation panel 70, the sheet conveyance unit 10 supplies the cleaning sheet CM1 placed on the manual feed tray 16 to the fixing nip NP along the conveyance path TR1, and then discharges the sheet to the sheet discharge tray 15. The front side of the cleaning sheet CM1 is supplied to the fixing nip NP While facing the pressure roller 34. No new image is formed on the cleaning sheet CM1.
Referring to
If it is determined in step S115 that the count value has reached n (sheets) (YES in step S115), the control unit 60 causes a message requesting sheet passing of the cleaning sheet to be displayed (S131), and determines whether an execution instruction of sheet passing of the cleaning sheet has been accepted (S133). The control unit 60 repeats the processing of step S133 until it is determined, that the execution instruction of sheet passing of the cleaning sheet has been accepted.
If it is determined in step S133 that execution instruction of sheet passing of the cleaning sheet has been accepted (YES in step S133), the control unit 60 supplies the cleaning sheet to the fixing nip NP (S135). Thereafter, the control unit 60 clears the non-image region position data and the count value (S123), and proceeds to the processing of step S101.
The configuration and operation of the image forming apparatus 1 other than the above is similar to the configuration and operation of the image forming apparatus according to the first embodiment, so description thereof will not be repeated.
According to this embodiment, as in the first embodiment, degradation of image quality can be suppressed. In addition, stains of the pressure roller 34 can be removed, stains of the sheet can be suppressed, and deterioration of image quality can be suppressed by simple processing of displaying a message.
When the n sheets of identical images including the non-image region R2 are consecutively fixed by the fixing apparatus 30, the image forming apparatus 1 may supply the cleaning sheet to the fixing nip NP. In this case, the image forming apparatus 1 only has to count the number of times of fixing the identical images, and it is not necessary to extract the non-image region R2 from the image each time the printing signal is received, and the processing performed by the image forming apparatus 1 can be simplified.
The control unit 60 may set the temperature of the fixing apparatus 30 of when the cleaning sheet is grasped with the fixing nip NP to be higher (for example, about 15 degrees higher) than the temperature of the fixing apparatus 30 of when toner images of a plurality of images IM including non-image regions overlapping each other are fixed. This increases the adhesive force of the cleaning image and makes it easy to remove fogging toner and sheet dust adhered to the surface of the pressure roller 34.
The control unit 60 may set the sheet passing speed of the fixing apparatus 30 of when the cleaning sheet is grasped with the fixing nip NP to be slower (for example, about half speed) than the sheet passing speed of the fixing apparatus 30 of when toner images of a plurality of images including non-image regions overlapping each other are fixed. This increases time of contacting of the cleaning image with the pressure roller 34 and makes it easy to remove fogging toner and sheet dust adhered to the surface of the pressure roller 34.
The fixing apparatus has any configuration as long as including a heating member that is heated by a heater and a pressing member that forms a fixing nip between the pressing member and the heating member by pressing the heating member. The fixing apparatus may include, for example, a fixing belt (an example of the heating member) stretched between a heating belt and a pad and heated by a heater provided inside the heating belt, and a pressure roller (an example of the pressure member) that forms a fixing nip between the pressure roller and the fixing belt by pressing the fixing belt. The heating member may be composed of a fixing roller, and the pressure member may be composed of a belt.
The above-described embodiment and modifications can be appropriately combined.
The processing in the embodiment and the modifications described above may be performed by software or a hardware circuit. It is also possible to provide a program for executing the processing in the above-described embodiment, and the program may be recorded on a recording medium such as a CD-ROM, a flexible disk, a hard disk, a ROM, a RAM, a memory card, and provided to a user. The program is executed by a computer such as a CPU. The program may be downloaded to the apparatus via a communication line such as the Internet.
Although embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are made for purposes of illustration and example only and not limitation. The scope of the present invention should be interpreted not by the above description but by terms of the appended claims, and it is intended that all modifications within meaning and scope equivalent to the claims are included.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-215503 | Nov 2017 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5865121 | Testardi | Feb 1999 | A |
| 20080138127 | Son | Jun 2008 | A1 |
| 20090257793 | Yoshioka | Oct 2009 | A1 |
| Number | Date | Country |
|---|---|---|
| 2010262186 | Nov 2010 | JP |
| 2012133034 | Jul 2012 | JP |
| Entry |
|---|
| Machine Translation of Imaizumi (JP2010262186). Nov. 2010 (Year: 2010). |
| Number | Date | Country | |
|---|---|---|---|
| 20190137911 A1 | May 2019 | US |
