The present invention contains subject matter related to Japanese Patent Application No. JP 2013-014388 filed in the Japanese Patent Office on Jan. 29, 2013, the entire contents of which being incorporated herein by reference.
1. Technical Field
The present invention relates to an image forming apparatus such as a color printer, a color copier and the like.
2. Background Art
In a recent image forming apparatus, there may be a case where any color shifts occur when registering respective color toner images. This is because a diameter of a driving roller of an intermediate transfer belt varies due to temperature rise inside the image forming apparatus during image forming operation and a speed of the intermediate transfer belt chronologically changes. The image forming apparatus has carried out a color registration correction on a regular basis in order to correct the color shifts.
For example, as shown in
Japanese Patent Application Publication No. H01-269958 discloses an image forming apparatus in which a color registration sensor reads respective color registration marks that are independently formed between pages (image forming regions) on the transfer belt and a color shift correction starts from each read color registration mark.
The image forming apparatus disclosed in Japanese Patent Application Publication No. H01-269958 has performed a color registration correction between pages. In such a color registration correction, by taking into consideration any variation in a cycle of photosensitive drum and/or a cycle of belt, the color registration marks are formed while an interval between the sheets of paper lengthens as compared with an interval between the sheets of paper during normal printing time. This causes less numbers of sheets of paper that are printable within a fixed time so that its print efficiency deteriorates.
The color registration correction carries out at timing of temperature rise around a process or at timing when predetermined sheets of paper pass through the apparatus. When any previously carried out jobs heat the apparatus (or in a condition where the apparatus is not cool), the inside of the apparatus keeps high to a certain extent. When the apparatus starts in this state and the registration correction carries out at timing of temperature rise, there may be a case where the apparatus does not shift to any color registration correction even if color shifts occur because of the high temperature in the apparatus. On the other hand, when the temperature in the apparatus reaches a fixed temperature, there may be a case where the apparatus carries out the color registration correction even if no color shifts occur actually. This causes any print efficiency to deteriorate and any toners to be wasted.
In a case of carrying the color registration correction out at timing when a predetermined sheets of paper passes through the apparatus, there may be a case where when the passed sheets of paper reaches the predetermined sheets of paper, the apparatus does not shift to any color registration correction even if color shifts occur. On the other hand, before the passed sheets of paper reaches the predetermined sheets of paper, there may be a case where the apparatus carries out the color registration correction even if no color shifts occur.
This invention addresses the above-mentioned issues and has an object to provide an image forming apparatus that can carry out a color registration correction efficiently.
To achieve the above-mentioned object, an image forming apparatus reflecting one aspect of this invention, which forms a color image by transferring images of respective colors formed on photosensitive members to an intermediate transfer member, contains an image forming portion that forms a decision mark for deciding whether or not a color registration correction for correcting color shifts in the color image carries out, the decision mark being obtained by registering the respective color marks on the intermediate transfer member, a detection portion that detects a width of the decision mark formed on the intermediate transfer member by the image forming portion, and a control portion that is configured to decide whether or not the color registration correction carries out based on the width of the decision mark detected by the detection portion.
According to the image forming apparatus reflecting one aspect of this invention, the image forming portion forms the decision mark by registering respective color marks on the intermediate transfer member. The detection portion detects the width of the decision mark formed on the intermediate transfer member. Based on the detection results by the detection portion, the control portion decides whether or not the color registration correction carries out.
In the image forming apparatus reflecting one aspect of this invention, the color mark constituting the decision mark contains color registration marks of respective colors such as yellow, magenta, cyan, black and the like, which are used in the color registration correction. The width of the decision mark means that a period of detection time taken between edges of the decision mark along a width direction thereof. The intermediate transfer member contains an intermediate transfer belt, drum and the like.
It is desirable to provide the image forming apparatus wherein the control portion controls the image forming portion to set writing timings of the respective color marks so that the decision mark is formed on the intermediate transfer member between sheets of paper.
It is also desirable to provide the image forming apparatus wherein timing of forming the decision mark is optionally changed.
It is still desirable to provide the image forming apparatus wherein the image forming portion contains plural photosensitive members corresponding to the respective colors, and the control portion controls the image forming portion to form the decision mark on the intermediate transfer member by using two photosensitive members which are set on positions that are farthest from each other among the plural photosensitive members.
It is further desirable to provide the image forming apparatus wherein the control portion controls the image forming portion to form the decision mark on the intermediate transfer member during a printing operation in a job, and when it is decided that the color shifts occur in the decision mark, the control portion controls the image forming portion to stop the printing operation in the job and start the color registration correction.
It is additionally desirable to provide the image forming apparatus wherein the control portion controls the image forming portion to change timing of forming the decision mark based on a variation amount in the widths of respective decision marks formed on the intermediate transfer member by plural times.
It is still further desirable to provide the image forming apparatus wherein the control portion controls the image forming portion to change timing of forming the decision mark based on a length of a width of the decision mark detected by the detection portion.
It is still additionally desirable to provide the image forming apparatus wherein the control portion is configured to decide whether or not the color registration correction carries out by using a reference width of the decision mark that is a reference when the color shifts occur in the color image and the reference width is optionally changed.
It is still desirable to provide the image forming apparatus wherein the control portion controls the image forming portion to set writing timing of the respective color marks so that the decision mark is formed on the intermediate transfer member between jobs.
It is still desirable to provide the image forming apparatus wherein the control portion calculates an average value of the widths of respective decision marks formed on the intermediate transfer member by plural times and is configured to decide whether or not the color registration correction carries out based on the calculated average value.
The concluding portion of this specification particularly points out and directly claims the subject matter of the present invention. However, those skilled in the art will best understand both the organization and method of operation of the invention, together with further advantages and objects thereof, by reading the remaining portions of the specification in view of the accompanying drawing(s) wherein like reference characters refer to like elements.
The following will describe configuration examples of the image forming apparatus as preferred embodiments relating to the invention with reference to drawings. It is to be noted that the description in the embodiments is exemplified and any technical scope of the claims and/or meaning of term(s) claimed in the claims are not limited thereto.
The image forming apparatus 100 according to the invention forms on an intermediate transfer belt 8 a decision color registration mark 12U for deciding whether or not the color registration correction carries out before the color registration correction carries out. The image forming apparatus 100 decides whether or not the color registration correction carries out based on a detection width of the decision color registration mark 12U (a color shift amount). This enables its print efficiency to be improved. The decision color registration mark 12U is formed by registering four color registration marks 12Y, 12M, 12C and 12K, which will be described later.
As shown in
The apparatus main body 102 contains a manipulation/display portion 70, the image reading portion 90, an image forming portion 10, an intermediate transfer belt 8, which is an example of the intermediate transfer member, color registration sensors 110, 112, a fixing portion 44 and an auto duplex unit (ADU).
The manipulation/display portion 70 contains a touch panel in which a display unit made of liquid crystal or the like and a positional detection unit of pressure-sensitive resistance film type or electrostatic capacitance type are combined, and key buttons such as ten keys, a start key and the like, which are provided around the touch panel. The manipulation/display portion 70 displays a manipulation screen and receives setting of image forming conditions such as a size and/or a species of a sheet of paper input by a user through the manipulation screen.
The image reading portion 90 scans and exposes the document mounted on the document table using an optical system in a scanning and exposure device. The image reading portion 90 performs photoelectric conversion on a scanned image of the document by a charge-couple device (CCD) image sensor to obtain an image information signal. The image reading portion 90 then performs a predetermined processing on this image information signal and outputs it to the image forming portion 10.
The image forming portion 10 forms an image based on an electrophotographic method. The image forming portion 10 includes an image forming unit 10Y which forms a yellow (Y) image, an image forming unit 10M which forms a magenta (M) image, an image forming unit 10C which forms a cyan (C) image and an image forming unit 10K which forms a black (K) image. The image forming units 10Y, 10M, 10C and 10K are arranged in a line from an upstream (upper) side in order along a moving direction of the intermediate transfer belt 8. In this embodiment, in order to indicate a color relative to common function or name, Y, M, C or K will be attached to the number of the common function or name, for example, 10Y.
The image forming unit 10Y includes a photosensitive drum 1Y, a charging portion 2Y arranged around the photosensitive drum 1Y, a writing (exposure) portion 3Y, a developing portion 4Y and a cleaning portion 6Y. The image forming unit 10M includes a photosensitive drum 1M, a charging portion 2M arranged around the photosensitive drum 1M, a writing portion 3M, a developing portion 4M and a cleaning portion 6M. The image forming unit 10C includes a photosensitive drum 1C, a charging portion 2C arranged around the photosensitive drum 1C, a writing (exposure) portion 3C, a developing portion 4C and a cleaning portion 6C. The image forming unit 10K includes a photosensitive drum 1K, a charging portion 2K arranged around the photosensitive drum 1K, a writing portion 3K, a developing portion 4K and a cleaning portion 6K.
Since the image forming units 10Y, 10M, 10C and 10K of respective colors have the same configuration as each other, the description on the configuration of the image forming units other than the image forming unit 10Y will be omitted in the following description. The charging portion 2Y uniformly charges static charges around a surface of the photosensitive drum 1Y. The writing portion 3Y contains LED print head (LPH) including LED array and an image formation lens, and a laser scanning and exposure apparatus with polygon mirror system. The writing portion 3Y scans by laser light based on the image information signal to form electrostatic latent images on the photosensitive drum 1Y which rotates to the sub scanning direction D2 under a motor control. The developing portion 4Y develops the electrostatic latent images formed on the photosensitive drum 1Y using yellow toner. Thus, a toner image that is a visible image is formed on the photosensitive drum 1Y.
The intermediate transfer belt 8 is an endless belt. The intermediate transfer belt 8 runs on plural rollers with it being stretched and supported by them. When the intermediate transfer belt 8 runs under control of a motor, the yellow toner image formed on the photosensitive drum 1Y is transferred on a transferred position of the intermediate transfer belt 8 (Primary Transfer). When transferring the yellow toner image, the intermediate transfer belt 8 moves toward the next photosensitive drum 1M which is arranged at a downstream (lower) side of the photosensitive drum 1Y.
Similar to a case of the yellow, the magenta toner image is formed on the photosensitive drum 1M. The magenta toner image formed on the photosensitive drum 1M is transferred on the transferred position of the intermediate transfer belt 8 while the magenta toner image is overlaid on the yellow toner image. The intermediate transfer belt 8 then moves toward the photosensitive drums 1C, 1Y and the cyan toner image and the black toner image are transferred on the transferred position of the intermediate transfer belt 8 while the cyan toner image and the black toner image are overlaid in order to form a color image.
Color registration sensors 110, 112 are examples of the detection portion and they are arranged at positions of the apparatus which respectively correspond to both ends of the intermediate transfer belt 8 along the main scanning direction D1 (see
The feeder 20 has plural feeding trays 20a, 20B each containing sheets of paper with a size such as A3, A4 or the like. The feeder 20 feeds the sheets of paper P one by one from the selected feeding tray and conveys the fed sheet of paper P to the registration rollers 32 through conveying rollers 22, 24, 26 and 28 and loop-forming rollers 30. Numbers of the feeding trays are not limited to two. A single or plural large capacity sheet feeder(s), which can contain a large number of sheets of paper P, may connect the image forming apparatus depending on the situation.
The registration rollers 32 include a driving roller and a driven roller. The loop-forming rollers 30 hit a forward end of the sheet of paper P to the registration rollers 32 to form a loop so that a skew (inclination) of the sheet of paper P can be corrected. The registration rollers 32 conveys the sheet of paper P to a secondary transfer portion 34, which contains a transfer roller and a follower roller, at desired timing. The secondary transfer portion 34 transfers the color image formed by overlaying respective toner images on each other on the transferred position of the intermediate belt 8 to a surface of the sheet of paper P fed from the feeder 20 altogether (Secondary Transfer). The secondary transfer portion 34 then conveys to the fixing portion 44 the sheet of paper P on which the color image is formed.
The fixing portion 44 contains a pressure roller and a heating roller. The fixing portion 44 fixes the toner images transferred on a surface side of the sheet of paper P by applying pressure to the sheet of paper P to which the toner images are transferred in the secondary transfer portion 34 and/or heating the same.
A conveying path changeover portion 48 for changing over the conveying path of the sheet of paper P to a sheet discharging side or a side of ADU 60 is provided at a downstream side of the fixing portion 44 along a sheet-conveying direction. The conveying path changeover portion 48 is composed of, for example, a solenoid, a motor and the like. The conveying path changeover portion 48 performs changeover control of the conveying path based on a selected printing mode (single surface printing mode or duplex printing mode).
Ejection rollers 46, which is provided at downstream side of the fixing portion 44 along the sheet-conveying direction, eject onto an sheet-ejection tray, not shown, the sheet of paper P fixed by the fixing portion 44. At this time, a single surface of the sheet of paper P has been printed in the single surface printing mode or both surfaces of the sheet of paper P have been printed in the duplex printing mode.
When re-feeding the sheet of paper P to the secondary transfer portion 34 during the duplex printing mode, the sheet of paper P, on a surface side of which an image is formed, is conveyed to ADU 60 via the conveying path changeover portion 48. The conveying rollers 62 or the like convey the sheet of paper, which is conveyed to the ADU 60, to a switchback route. In the switchback route, ADU rollers 64 perform a reverse rotation control on the sheet of paper P to convey the sheet of paper P to a U-turn path with a rear end of the sheet of paper P being lead. The conveying rollers 66, 68 and the like provided in the U-turn path re-feed the sheet of paper P to the secondary transfer portion 34 while front and back of the sheet of paper P is reversed. The sheet of paper P re-fed to the secondary transfer portion 34 is subject to any image forming process which is similar to the image forming process that has been carried out in the front surface side of the sheet of paper P.
The following will describe a configuration example of the decision registration mark 12U.
As shown in
The decision registration mark 12U contains a pattern 12Ua extending to the main scanning direction D1 and a pattern 12Ub extending diagonally with respect to the pattern 12Ua. The decision registration mark 12U is configured so that it is seen as roughly “V” shaped, as seen in a plane. It is to be noted that a shape of each of the color registration marks 12Y, 12M, 12C and 12K constituting the decision registration mark 12U is not limited to the rough shape of “V” and another shape may be adapted.
The following will describe a configuration example of the image forming apparatus 100 according to the first embodiment of the invention.
The control portion 50 connects the color registration sensors 110, 112, the manipulation/display portion 70, a storage portion 150, the image forming portion 10, a conveying portion 140, the feeder 20 and the fixing portion 44, respectively. The color registration sensors 110, 112 respectively detect the decision registration mark 12U and the color registration marks 12Y, 12M, 12C and 12K formed on the intermediate transfer belt 12U during the color registration correction and the decision operation on whether or not the color registration correction carries out. The color registration sensors 110, 112 supply an analog detection signal (voltage value) thus obtained by this detection to the control portion 50.
The storage portion 150 contains nonvolatile semiconductor element, hard disk drive and the like. The storage portion 150 stores image data read by the image reading portion 90. The storage portion 150 also stores data on the respective color registration marks, threshold values Th, periods of detection time T1, T2 and the like.
The manipulation/display portion 70 displays a predetermined manipulation screen based on any display control by the control portion 50 and receives an input of frequency of forming the decision registration mark 12U on the manipulation screen to supply the manipulation signal to the control portion 50. This allows a user to change the frequency of forming the decision registration mark 12U optionally. This also allows the periods of detection time T1, T2 to change optionally based on their required accuracies.
The conveying portion 140 contains an intermediate transfer belt driving portion 120 and a photosensitive member driving portion 130. The intermediate transfer belt driving portion 120 is composed of, for example, a stepping motor. The intermediate transfer belt driving portion 120 rotates based on a driving signal received from the control portion 50 to move the intermediate transfer belt 8 to the sub scanning direction D2. The photosensitive member driving portion 130 is composed of, for example, a stepping motor. The photosensitive member driving portion 130 rotates based on a driving signal received from the control portion 50 to rotate the respective photosensitive drums 1Y, 1M, 1C and 1K to the sub scanning direction D2.
The image forming portion 10 performs writing on the respective photosensitive drums 1Y, 1M, 1C and 1K using laser light based on the image data read out of the storage portion 150 under the control of the control portion 50. The image forming portion 10 also performs writing on the respective photosensitive drums 1Y, 1M, 1C and 1K using laser light by controlling writing timing based on the registration mark data read out of the storage portion 150 under the control of the control portion 50 so that respective color registration marks 12Y, 12M, 12C and 12K can be transferred on the intermediate transfer belt 8.
The feeder 20 takes the sheet of paper P, which corresponds to image forming condition such as a size of the sheet of paper input on the manipulation screen of the manipulation/display portion 70, out of the feeding tray 20a or 20B to feed it to the secondary transfer portion 34 based on an instruction from the control portion 50.
The fixing portion 44 adjusts temperature or the like based on the control of the temperature, pressure and the like by the control portion 50 to fix the toner images on the sheet of paper P.
[Forming Example and Detection Example of Registration Mark when Color Shifts do not Occur]
The following will describe forming example and detection example of the decision registration mark 12U during the decision operation on whether or not the color registration correction carries out if color shifts do not occur.
In a normal case where color shifts do not occur, as shown in
During the decision operation on whether or not the color registration correction carries out, the color registration sensor 110 detects edges E1, E2, respectively, of the pattern 12Ua in the decision registration mark 12U, in order to decide whether or not the color shifts occur along the sub scanning direction D2. The edges E1, E2 are edges of the pattern 12Ua along the sub scanning direction D2. The control portion 50 calculates a period of detection time (width) T11 between the edges E1 and E2 based on the positions of the edges E1, E2 detected by the color registration sensor 110 and a previously set threshold value Th. When color shifts do not occur, the period of detection time along the sub scanning direction D2 is T11.
Similarly, the color registration sensor 110 detects edges E3, E4, respectively, of the pattern 12Ub extending diagonally with respect to the sub scanning direction D2 in the decision registration mark 12U in order to decide whether or not the color shifts occur along the main scanning direction D1. The edges E3, E4 diagonally intersect the sub scanning direction D2. The control portion 50 calculates a period of detection time T21 between the edges E3 and E4 based on the positions of the edges E3, E4 detected by the color registration sensor 110 and the previously set threshold value Th. When color shifts do not occur, the period of detection time along the main scanning direction D1 is T21.
[Forming Example and Detection Example of Registration Mark when Color Shifts Occur Along Sub Scanning Direction]
The following will describe forming example and detection example of the registration mark 12U during the decision operation on whether or not the color registration correction carries out if color shifts occur along the sub scanning direction D2.
In a case where color shifts occur along the sub scanning direction D2, as shown in
During the decision operation on whether or not the color registration correction carries out, the color registration sensor 110 detects an edge E1 of the pattern 12Ka in a black registration mark 12K along the sub scanning direction D2. The color registration sensor 110 then detects an edge E2 of the pattern 12Ya in a yellow registration mark 12Y along the sub scanning direction D2. In this case, a period of detection time when detecting the edge E2 becomes later than the normal time when the color shifts do not occur by the shift amount of the respective color registration marks 12Y, 12M and 12C along the sub scanning direction D2. The control portion 50 calculates a period of detection time T12 between the edges E1 and E2 based on the positions of the edges E1, E2 detected by the color registration sensor 110 and a previously set threshold value Th, as shown in
In this embodiment, it is decided whether or not the color shifts occur along the sub scanning direction D2, as shown in
[Forming Example and Detection Example of Registration Mark when Color Shifts Occur Along Main Scanning Direction]
The following will describe forming example and detection example of the registration mark 12U during the decision operation on whether or not the color registration correction carries out if color shifts occur along the main scanning direction D1.
In a case where color shifts occur along the main scanning direction D1, as shown in
During the decision operation on whether or not the color registration correction carries out, the color registration sensor 110 detects an edge E3 of the pattern 12Kb, which diagonally intersects the sub scanning direction D2, in a black registration mark 12K. The color registration sensor 110 then detects an edge E4 of the pattern 12Yb, which diagonally intersects the sub scanning direction D2, in a yellow registration mark 12Y. In this case, a period of detection time when detecting the edge E4 becomes later than the normal time when the color shifts do not occur by a shift amount of the respective color registration marks 12Y, 12M and 12C along the main scanning direction D1. The control portion 50 calculates a period of detection time T22 between the edges E3 and E4 based on the positions of the edges E3, E4 detected by the color registration sensor 110 and the previously set threshold value Th.
In this embodiment, as shown in
The following will describe an operation example of the image forming apparatus 100 when performing the decision operation on whether or not the color registration correction carries out with reference to
As shown in
At the step S110, the control portion 50 forms the respective color registration marks 12Y, 12M, 12C and 12K constituting the decision registration mark 12U within a space S, which is provided between the sheets of paper P, P, on a surface of the intermediate transfer belt 8 with them being registered in order. The control portion 50 may form the decision registration marl 12U for each sheet of paper or for every predetermined sheets of paper. The user may manipulate the manipulation/display portion 70 to set the timing (frequency) of forming the decision registration mark 12U optionally. The control portion 50 goes to a step S120 after it forms the decision registration mark 12U.
At the step S120, the color registration sensor 110 detects (reads) the decision registration mark 12U formed on the surface of the intermediate transfer belt 8. The color registration sensor 110 detects the positions of the edges E1, E2 of the decision registration mark 12U to decide whether or not the color shifts occur along the sub scanning direction D2 and outputs the detection results to the control portion 50. The control portion 50 goes to a step S130 when detecting the decision registration mark 12U.
At the step S130, the control portion 50 calculates the period of detection time (detection width) T12 of the decision registration mark 12U along the sub scanning direction D2 from the positions of the edges E1, E2 of the decision registration mark 12U received from the color registration sensor 110 as the detection results (see
At the step S140, the control portion 50 determines whether or not the period of detection time T12 of the decision registration mark 12U along the sub scanning direction D2 exceeds the previously set period of reference time T1. The control portion 50 reads the period of reference time T1 out of the storage portion 150 and compares the period of detection time T12 detected by the color registration sensor 110 with the read period of reference time T1. The control portion 50 determines that color shifts occur along the sub scanning direction D2 when the period of detection time T12 of the decision registration mark 12U along the sub scanning direction D2 exceeds the period of reference time T1 and goes to a step S190. On the other hand, the control portion 50 determines that color shifts do not occur along the sub scanning direction D2 when the period of detection time T12 of the decision registration mark 12U along the sub scanning direction D2 does not exceed the period of reference time T1 and goes to a step S150.
At the step S150, the control portion 50 calculates the period of detection time (detection width) T22 of the decision registration mark 12U along the main scanning direction D1 from the positions of the edges E3, E4 of the decision registration mark 12U received from the color registration sensor 110 as the detection results (see
When determining that the color shifts do not occur along the sub scanning direction D2, the control portion 50 determines whether or not the color shifts occur along the main scanning direction D1, at the step S160. The control portion 50 determines whether or not the period of detection time T22 of the decision registration mark 12U along the main scanning direction D1 exceeds the previously set period of reference time T2. The control portion 50 reads the period of reference time T2 out of the storage portion 150 and compares the period of detection time T22 detected by the color registration sensor 110 with the read period of reference time T2. The control portion 50 determines that color shifts occur along the main scanning direction D1 when the period of detection time T22 of the decision registration mark 12U along the main scanning direction D1 exceeds the period of reference time T2 and goes to the step S190. On the other hand, the control portion 50 determines that the color shifts do not occur along the main scanning direction D1 when the period of detection time T22 of the decision registration mark 12U along the main scanning direction D1 does not exceed the period of reference time T2 and goes to a step S170.
When determining that the color shifts occur along the sub scanning direction D2 or the main scanning direction D1, the control portion 50 determines whether or not the printing operation stops at the step S190. For example, it is determined on whether or not the user selects to stop the printing operation on the manipulation screen of the manipulation/display portion 70. The control portion 50 goes to a step S200 when it determines that the printing operation stops or goes to the step S170 when it does not determine that the printing operation stops.
At the step S200, the control portion 50 stops feeding the sheets of paper P when selecting the stop of the printing operation and stops the continuous printing operation. The control portion 50 goes to a step S210 when stopping the continuous printing operation.
At the step S210, the control portion 50 carries out the color registration correction. In the color registration correction, when forming the decision registration mark 12U on the intermediate transfer belt 8 by registering the respective color registration marks 12Y, 12M, 12C and 12K in order, the color registration sensor 110 detects shift amount thereof along the main scanning direction and/or the sub scanning direction and the control portion 50 calculates a color shift amount in each color. The control portion 50 goes to a step S220 when calculating the color shift amount in each color.
At the step S220, the control portion 50 restarts the printing operation. In the restarted printing operation, by feeding back the correction values based on the color shift amount in each color calculated at the step S210 to the image forming portion 10 and the like, the control portion 50 corrects and controls any writing timing or the like to form a desired image on the sheets of paper P. The control portion 50 goes to the step S170 when restarting the printing operation.
At the step S170, the control portion 50 keeps performing the continuous printing operation based on the contents of job. At a step S180, the control portion 50 determines whether or not the job in the continuous printing operation finishes. The control portion 50 finishes a series of the continuous printing operation when determining that the job in the continuous printing operation finishes. On the other hand, the control portion 50 returns to the step S100 where the control portion 50 performs the above-mentioned decision operation on whether or not the color registration correction carries out in the continuous printing operation when determining that the job in the continuous printing operation does not finish.
Additionally, although, in the above-mentioned embodiment, in the four color registration marks 12Y, 12M, 12C and 12K registered on the same position on the intermediate transfer belt 8, it has been previously determined whether or not the color shifts occur along the sub scanning direction D2, this invention is not limited thereto. It may be previously determined whether or not the color shifts occur along the main scanning direction D1.
As described above, according to the first embodiment, before the color registration correction, the decision registration mark 12U is formed within the space S on the intermediate transfer belt 8 between the sheets of paper P, P while the respective color registration marks 12Y, 12M, 12C and 12K constituting the decision registration mark 12U are registered on the same position. The control portion 50 calculates the color shift amount (periods of detection time) in the decision registration mark 12U. The control portion 50 determines whether or not the color registration correction carries out based on each of the periods of detection time exceeds the set period of reference time T1 or T2. This enables numbers of the carried-out color registration marks to decrease so that the color registration corrections can be efficiently carried out. It is thus possible to realize any improvement in the efficiency of printing. Many color registration marks are not used and each one color registration mark constitutes the decision registration mark 12U so that it is possible to realize a reduction of the amount of consumption of the toner.
Further, by forming the decision registration mark 12U for every predetermined time, it is possible to detect color shifts steady when the color shifts suddenly occur by attaching any scratch and dusty to the intermediate transfer belt 8 or when the temperature rise in the image forming apparatus is in saturation and the temperature in the image forming apparatus does not exceed the threshold temperature. This enables the color registration correction to carry out even in these conditions.
Since the decision registration mark 12U is formed on the intermediate transfer belt 8 within the space S between the sheets of paper P, P, (or between the image forming regions T, T), the image forming apparatus 100 according to this embodiment can deal with even if the space between the sheets of paper P, P is narrow-pitched. Since the decision registration mark 12U is formed by registering the four color registration marks 12Y, 12M, 12C and 12K, it is possible to determine whether or not the color shifts occur under the same conditions as those in the case of actually forming the color image. This enables the decision on whether or not the color registration correction carries out to be more accurately performed.
The second embodiment is different from the first embodiment in that a frequency (timing) of forming the decision registration marks 12U is determined on the basis of variation amounts of widths of the decision registration marks 12U. It is to be noted that since other configurations and functions of the image forming apparatus of the second embodiment is similar to those of the image forming apparatus of the first embodiment, the same symbols are attached to common components and their detailed description will be omitted.
In the second embodiment, the decision registration marks 12U are formed plural times on a surface of the intermediate transfer belt 8. The control portion 50 calculates the variation amounts in plural detection widths of the respective decision registration marks 12U formed plural times. The control portion 50 determines (or changes) the frequency of forming the decision registration marks 12U based on the calculated variation amounts by referring to a Table TB1.
For example, as shown in
The following will describe an operation example of the image forming apparatus 100 according to the second embodiment. In the following description, a case where the color registration sensor 110 detects a decision registration mark 12U of the two decision registration marks 12U, 12U formed on the intermediate transfer belt 8 will be described.
The control portion 50 controls the image forming portion 10 or the like to form the decision registration marks 12U on the space S in the intermediate transfer belt 8 between the sheets of paper P, P. In this embodiment, as shown in
The control portion 50 receives the detection width of each decision registration mark 12U along the sub scanning direction D2 for each time from the color registration sensor 110 to calculate a slope showing variation amount in the color shift amount based on the received detection width of each decision registration mark 12U for each time. In this embodiment, as the calculated slope showing the variation amount in the color shift amount,
For example, when the slope of the calculated variation amount is the slope 1, as shown in
The control portion 50 controls the image forming portion 10 or the like to form the decision registration marks 12U on the intermediate transfer belt 8 based on the set frequency of forming the decision registration marks 12U. The control portion 50 decides whether or not the color registration correction carries out based on the detection widths of the decision registration marks 12U detected by the color registration sensor 110 or the like. The control portion 50 then carries out the color registration correction based on the determination results.
As described above, according to the second embodiment, the control portion 50 determines the frequency of forming the decision registration marks 12U based on the slope showing the variation amount in the detection widths of the decision registration marks 12U so that it is possible to determine that a possibility such that color shift amount exceeds the reference period of detection time T1 is low when the variation amount in the color shift amount is small. In this case, since the frequency of forming the decision registration marks 12U can be decreased, the amount of toner consumption may be also decreased.
It is to be noted that although, in the above-mentioned embodiment, the frequency of forming the decision registration marks 12U has been determined on the basis of the detection widths of each of the decision registration marks 12U along the sub scanning direction D2, this invention is not limited thereto. The frequency of forming the decision registration marks 12U may be determined on the basis of the detection widths of each of the decision registration marks 12U along the main scanning direction D1. Further, the frequency of forming the decision registration marks 12U may be determined by taking them into consideration.
The third embodiment is different from the first embodiment in that the frequency of forming the decision registration marks 12U is determined on the basis of lengths of the detection widths of the decision registration marks 12U. It is to be noted that since other configurations and functions of the image forming apparatus of the second embodiment is similar to those of the image forming apparatus of the first embodiment, the same symbols are attached to common components and their detailed description will be omitted.
In the third embodiment, the color registration sensor 110 detects the detection widths of the decision registration marks formed on the surface of the intermediate transfer belt 8 along the sub scanning direction. The control portion 50 determines (or changes) the frequency of forming the decision registration marks 12U based on the lengths of the detection widths of the decision registration marks 12U obtained by this detection by referring to a Table TB2.
For example, as shown in
The following will describe an operation example of the image forming apparatus 100 according to the third embodiment. In the following description, a case where the color registration sensor 110 detects a decision registration mark 12U of the two decision registration marks 12U, 12U formed on the intermediate transfer belt 8 will be described.
The control portion 50 controls the image forming portion 10 or the like to form the decision registration marks 12U on the space S on the intermediate transfer belt 8 between the sheets of paper P, P. The color registration sensor 110 detects a detection width of the pattern 12Ua of each of the decision registration marks 12U, which are formed on the surface of the intermediate transfer belt 8, along the sub scanning direction D2 and outputs it to the control portion 50.
The control portion 50 receives the detection width of each decision registration mark 12U along the sub scanning direction D2 for each time from the color registration sensor 110. The control portion 50 then refers to the table TB2 shown in
For example, when the detection width received from the color registration sensor 110 is Tx, as shown in
The control portion 50 controls the image forming portion 10 or the like to form the decision registration marks 12U on the intermediate transfer belt 8 based on the set frequency of forming the decision registration marks 12U. The control portion 50 decides whether or not the color registration correction carries out based on the detection width of each of the decision registration marks 12U detected by the color registration sensor 110 or the like. The control portion 50 then carries out the color registration correction based on the determination results.
In contrast, as shown in
As described above, according to the third embodiment, the control portion 50 determines the frequency of forming the decision registration marks 12U based on the lengths of the detection widths of the decision registration marks 12U so that it is possible to determine that a possibility such that the detection width rapidly exceeds the reference period of detection time T1 is low when the detection width is close to the normal value. In this case, since the frequency of forming the decision registration marks 12U can be decreased, the amount of toner consumption may be also decreased.
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.
Although it has described in the above-mentioned embodiments that the control portion 50 controls the image forming portion 10 to form the decision registration mark 12U by registering the four color registration marks 12Y, 12M, 12C and 12K using four photosensitive drums 1Y, 1M, 1C and 1K, this invention is not limited thereto. For example, the control portion 50 may control the image forming portion 10 to form the decision registration mark 12U by registering two color registration marks using two photosensitive drums which are set on positions that are farthest from each other among the four photosensitive members. In this embodiment, the control portion 50 controls the image forming portion 10 to form the decision registration mark 12U by registering yellow and black color registration marks 12Y, 12K using two photosensitive drums 1Y and 1K. The two photosensitive drums 1Y and 1K which are set on positions that are farthest from each other are used because they are most subject to any influence when thermal extension occurs. This avoids the photosensitive drums 1M and 1C so that the amount of toner consumption may be further decreased.
Although it has described in the above-mentioned embodiments that the decision registration marks 12U are formed between the sheets of paper P, P, the control portion 50 may control the image forming portion 10 or the like to form the decision registration marks 12U between the jobs.
Further, the control portion 50 may calculate an average value of the detection widths of the respective decision registration marks formed on the intermediate transfer belt 8 plural times and is configured to decide whether or not the color registration correction carries out based on the calculated average value. This enables any suddenly generated color shifts to be avoided, which allows the control portion 50 to more surely determine whether or not the color registration correction carries out.
Number | Date | Country | Kind |
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2013-014388 | Jan 2013 | JP | national |