JP5119755B2 - Image forming apparatus and control apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus and a control apparatus.

In an electrophotographic color image forming apparatus such as a printer or a copying machine, a laser beam is emitted for each color from an exposure device, and the photosensitive member is scanned and exposed. At that time, in order to adjust the position of each color image, the exposure position of each color laser beam on each photoconductor is adjusted.
For example, in Patent Document 1, registration marks for each color are formed at two locations on both ends of the conveyance belt, and these are detected by mark detectors arranged at two locations on both ends of the conveyance belt. Based on this, it is described that the exposure position of each color laser beam is adjusted.

JP-A-1-142567

Here, in general, it is effective to adjust both the start point position and the end point position of the scanning line on the photosensitive member in order to accurately adjust the exposure position of the laser beam in the entire scanning region. However, providing a plurality of detection means for detecting the scanning line position or a mechanism for moving the detection means for that purpose has a disadvantage of increasing the manufacturing cost.
An object of the present invention is to realize an exposure position adjustment mechanism in an image forming apparatus with an inexpensive configuration.

The invention according to claim 1 is directed to an image carrier, an exposure unit that scans and exposes the image carrier with a light beam emitted from a light source, a drive unit that drives the light source based on image data, and the light source. Storage means for storing adjustment data for adjusting the output timing of the image data from the drive means, and a predetermined pattern image formed on the image carrier by the exposure means scanning and exposing the light flux. Detection means for detecting the position as a position on the image holding body or on the transfer body on which the pattern image is transferred from the image holding body, and the storage means starts scanning from the scanning central portion of the luminous flux. The adjustment data obtained based on the position in the main scanning direction with respect to the pattern image formed in the region on the image holding body on the side is stored, and the detection means stores the image holding Of the position is detected and the driving means of the pattern image formed in the region of the scanning end point from the scanning center of the light beam, the output start timing of the image data in the one scan line with respect to said light source set based on the more stored the adjusted data in the storage unit, set on the basis of the information on the position of more said detected pattern image output end timing of the image data to said detecting means in one scan line The image forming apparatus is characterized in that the light source is driven.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the detecting means includes a first arrangement position corresponding to a scanning end point from the scanning center portion of the light beam and a scanning central portion of the light beam. Based on the position of the pattern image detected by the detection means at the second arrangement position at a predetermined time, the storage means is provided to be movable to each of the second arrangement positions corresponding to the scanning start point side. The obtained adjustment data is stored, and the driving unit is configured to determine the output timing of the image data within one scanning line, and information on the position of the pattern image detected by the detection unit at the first arrangement position. The light source is driven based on the setting.
According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the image forming apparatus further includes a scanning start timing detecting unit that detects a scanning start timing of the light beam emitted from the light source to the image carrier, The drive means sets the output start timing based on information relating to the scan start timing detected by the scan start timing detection means and the adjustment data, and drives the light source.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, the image forming apparatus further includes a scanning start timing detecting unit that detects a scanning start timing of the light beam emitted from the light source to the image carrier, The storage unit further stores information on the scan start timing detected by the scan start timing detection unit at a predetermined time, and the drive unit stores information on the scan start timing stored in the storage unit and the adjustment. The output start timing is set based on the data, and the light source is driven.
According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the storage means is a position of the pattern image detected by the detection means at the second arrangement position under a predetermined temperature environment. The adjustment data obtained based on the information and information on the scanning start timing detected by the scanning start timing detection means under a predetermined temperature environment are stored.

According to a sixth aspect of the present invention , in the image forming apparatus according to the first aspect, a plurality of the image holding bodies are arranged, and the exposure unit corresponds to each of the plurality of image holding bodies. Scanning exposure is performed with light beams emitted from the plurality of light sources provided, and the storage unit adjusts the adjustment data for adjusting the output timing of the image data for each of the plurality of light sources from the driving unit. It is memorized.
According to a seventh aspect of the present invention , in the image forming apparatus according to the first aspect, a plurality of the image holding bodies are arranged, and the exposure unit corresponds to each of the plurality of image holding bodies. Scanning exposure is performed with light beams emitted from the plurality of light sources provided in the sub-scanning direction, and the storage unit is arranged in the sub-scanning direction obtained based on positions in the sub-scanning direction with respect to the pattern image on the plurality of image carriers. Position information is further stored, and the drive means drives the light source by adjusting a time difference set between the light beams emitted from each of the plurality of light sources based on the position information in the sub-scanning direction. It is characterized by.
The invention according to claim 8 is the image forming apparatus according to claim 2, further comprising holding means for holding the detection means at the first arrangement position and / or the second arrangement position. And

According to a ninth aspect of the present invention, there is provided storage means for storing adjustment data for adjusting the output timing of the image data from the driving means for driving the light source based on the image data to the light source, and light flux from the light source. Information relating to the position on the image carrier with respect to a predetermined pattern image formed on the image carrier by scanning exposure or information on the position on the transfer body to which the pattern image has been transferred from the image carrier is obtained. A position information acquisition unit, and an output start timing of the image data within one scanning line from the driving unit to the light source are instructed based on the adjustment data stored in the storage unit, and within one scanning line and a instruction means for instructing on the basis of the output end timing of the image data to the information on the position of the acquired pattern images by the position information acquiring unit, wherein The storage means stores the adjustment data obtained based on the position in the main scanning direction with respect to the pattern image formed in the region on the image holding body on the scanning start point side from the scanning central portion of the luminous flux, The position information acquisition unit is a control device that acquires information related to the position of the pattern image formed in a region on the scanning end point side from the scanning center portion of the light flux of the image carrier .

According to a tenth aspect of the present invention, in the control device according to the ninth aspect, the storage means outputs the image data to each of the plurality of light sources that emits the light flux to each of the plurality of image carriers. The adjustment data for adjusting is stored.
According to an eleventh aspect of the present invention, the control device according to the ninth aspect further includes scanning start timing acquisition means for acquiring information related to a scanning start timing of the light beam emitted from the light source to the image carrier. The storage means further stores information on the scan start timing acquired by the scan start timing acquisition means at a predetermined time, and the instruction means stores information on the scan start timing stored in the storage means and the information The output start timing is instructed based on the adjustment data.

According to the first aspect of the present invention, the exposure position adjusting mechanism in the image forming apparatus can be realized with an inexpensive configuration as compared with the case where the present invention is not adopted.
According to the second aspect of the present invention, the position of the pattern image used when calculating the adjustment data stored in the storage means can be detected more accurately than when the present invention is not adopted.
According to the third aspect of the present invention, the output start timing of the image data can be set without forming a pattern image for position adjustment.
According to the fourth aspect of the present invention, compared to the case where the present invention is not adopted, the scan start position can be adjusted with high accuracy even when the scan start timing fluctuates.
According to the fifth aspect of the present invention, it is possible to adjust the scanning start position with high accuracy even when the temperature environment fluctuates, compared to the case where the present invention is not adopted.

According to the sixth aspect of the present invention, as compared with the case where the present invention is not adopted, it is possible to reduce the shift amount of the scanning start timing of each light beam for exposing each of the plurality of image carriers.
According to the seventh aspect of the present invention, it is possible to reduce the amount of deviation in the sub-scanning direction between the plurality of light beams that expose each of the plurality of image carriers, compared to the case where the present invention is not adopted.
According to the eighth aspect of the present invention, the position of the pattern image used when calculating the adjustment data stored in the storage means can be detected more accurately than in the case where the present invention is not adopted.

According to the ninth aspect of the present invention, the exposure position adjusting mechanism in the image forming apparatus can be realized with an inexpensive configuration as compared with the case where the present invention is not adopted.
According to the tenth aspect of the present invention, compared to the case where the present invention is not adopted, it is possible to reduce the shift amount of the scanning start timing of each light beam for exposing each of the plurality of image carriers.
According to the eleventh aspect of the present invention, it is possible to adjust the scanning start position with high accuracy even when the scanning start timing fluctuates, compared to the case where the present invention is not adopted.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
[Embodiment 1]
FIG. 1 is a diagram illustrating an example of a configuration of an image forming apparatus 1 to which the exemplary embodiment is applied. An image forming apparatus 1 shown in FIG. 1 is a so-called tandem type digital color printer using an electrophotographic system, and an image forming process unit 70 that forms an image corresponding to image data of each color, and the entire image forming apparatus 1. An image processing unit 81 that performs predetermined image processing on image data received from, for example, an image reading device 4 such as a personal computer (PC) 3 or a scanner, a processing program, and image data are stored. For example, a main storage unit 82 realized by a hard disk drive (Hard Disk Drive), and a power supply unit 85 that converts electric power from a commercial power source into a predetermined voltage and supplies it to each unit are provided.

In the image forming process unit 70, four image forming units 10Y, 10M, 10C, and 10K (hereinafter also collectively referred to as “image forming unit 10”) are arranged in parallel in the vertical direction (substantially vertical direction) at regular intervals. . The image forming unit 10 develops a photosensitive drum 11 as an example of an image carrier, a charging roll 12 that charges the surface of the photosensitive drum 11, and an electrostatic latent image formed on the photosensitive drum 11 with each color toner. A developing unit 13 and a drum cleaner 14 for cleaning the surface of the photosensitive drum 11 after transfer are provided.
Each image forming unit 10 is configured to be detachable from the main body of the image forming apparatus 1. For example, when the toner in the developing device 13 is consumed or the photosensitive drum 11 reaches the end of its life, the image forming unit 10 Exchanged in units of 10 forming units.

The charging roll 12 is composed of a roll member in which a conductive elastic layer and a conductive surface layer are sequentially laminated on a conductive core metal such as aluminum or stainless steel. Then, a charging bias voltage is supplied from a charging power source (not shown), and the surface of the photosensitive drum 11 is uniformly charged at a predetermined potential while being driven to rotate relative to the photosensitive drum 11.
The developing device 13 holds a two-component developer composed of yellow (Y), magenta (M), cyan (C), and black (K) toners and a magnetic carrier in each of the image forming units 10, and is photosensitive. The electrostatic latent image formed on the body drum 11 is developed with each color toner.
The drum cleaner 14 brings a plate-like member formed of a rubber material such as urethane rubber into contact with the surface of the photosensitive drum 11 to remove toner, paper dust, and the like attached on the photosensitive drum 11.

Further, the image forming apparatus 1 according to the present embodiment is provided with a laser exposure unit 20 as an example of an exposure unit that exposes the photosensitive drum 11 provided in each image forming unit 10. The laser exposure unit 20 acquires image data for each color from the image processing unit 81, and scans the photosensitive drum 11 of each image forming unit 10 with laser light whose lighting is controlled based on the acquired color image data. Exposure.
Further, a paper transport belt 30 that transports the paper P that is a recording material (recording paper) is disposed so as to move in contact with the photosensitive drum 11 of each image forming unit 10. The paper transport belt 30 is formed of a film-like endless belt that electrostatically attracts the paper P. Then, the paper P is stretched across the drive roll 32 on the upper side (paper discharge side) and the idle roll 33 on the lower side (paper feed side), and the paper P is moved substantially downward in the vertical direction between the photosensitive drum 11. A sheet conveyance path M1 that is conveyed upward from the sheet is formed.

Transfer rolls 31 are arranged at positions inside the paper conveyance belt 30 and facing the respective photosensitive drums 11. Each transfer roll 31 forms a transfer electric field with the photosensitive drum 11, so that each color toner image formed by each image forming unit 10 is formed on the paper P held and transported by the paper transport belt 30. Transfer sequentially. Further, on the outer side of the sheet conveying belt 30 and on the downstream side of each transfer roll 31, a static elimination lamp 35 that neutralizes the photosensitive drum 11 after the transfer is provided.
An adsorption roll 34 that charges the paper transport belt 30 is disposed at the most upstream portion of the paper transport belt 30 on the photosensitive drum 11 side. The surface of the paper transport belt 30 is electrostatically attracted to the paper P by being charged to a predetermined potential by the suction roll 34.

The detection means used when adjusting the exposure position of the laser exposure device 20 on the photosensitive drum 11 is positioned at one end side position in the width direction of the region where the paper transport belt 30 is stretched over the drive roll 32. As an example, a detection sensor 60 is arranged. The detection sensor 60 detects the position on the paper transport belt 30 of a position correction pattern made up of each color toner image formed on the paper transport belt 30. Then, position data regarding the detected position correction pattern for each color is transmitted to the control unit 80.
The detection sensor 60 of the present embodiment is configured to be detachable from the apparatus main body. When adjustment before factory shipment, which will be described later with respect to the laser exposure device 20, is performed, the paper conveyance belt 30 is removed from one width direction end side position and moved to the other width direction end side position. The

Further, the position correction pattern held on the sheet conveyance belt 30 after the position is detected is removed on the opposite side of the sheet conveyance belt 30 from the area where the image forming units 10 are arranged. A belt cleaner 36 is provided.
In addition, a fixing device 40 that performs a fixing process by heat and pressure on an unfixed toner image on the paper P is disposed on the downstream side of the paper transport belt 30 along the paper transport path M1.

Further, as a paper transport system other than the paper transport belt 30, a paper storage unit 50 that stores the paper P on the paper feed side, a pickup roll 51 that feeds out the paper P stored in the paper storage unit 50 at a predetermined timing, and a pickup A transport roll 52 that transports the paper P fed by the roll 51 and a registration roll 53 that feeds the paper P to the paper transport belt 30 in accordance with an image forming operation are provided.
On the other hand, on the paper discharge side, a paper discharge roll 54 that conveys the paper P fixed by the fixing device 40, and in the case of single-sided printing, the paper P is directed toward a paper discharge unit 90 provided at the top of the apparatus main body. In the case of double-sided printing, the paper P on which one side is fixed by the fixing device 40 is directed to the double-sided conveyance path M2 by reversing from the rotation direction toward the paper discharge unit 90 at a predetermined timing. A reversing roll 55 that is fed out is disposed. In addition, the double-sided conveyance path M2 is provided with a plurality of conveyance rolls 56 along the double-sided conveyance path M2.

  In the image forming apparatus 1 of the present embodiment, image data input from the PC 3, the image reading apparatus 4, or the like is subjected to predetermined image processing by the image processing unit 81, and the laser exposure device 20 of the image forming process unit 70. To be supplied. In the black (K) image forming unit 10K of the image forming process unit 70, the surface of the photosensitive drum 11 is uniformly charged with a predetermined potential by the charging roll 12, and further, based on the black image data by the laser exposure unit 20. The electrostatic latent image is formed by scanning exposure with the laser light whose lighting is controlled. The formed electrostatic latent image is developed by the developing device 13, and a black (K) toner image is formed on the photosensitive drum 11. Similarly, in the image forming units 10Y, 10M, and 10C, yellow (Y), magenta (M), and cyan (C) toner images are formed.

On the other hand, when the formation of each color toner image in each image forming unit 10 is started, the paper P fed out from the paper storage unit 50 is supplied to the paper transport belt 30 by the resist roll 53 in accordance with the toner image formation timing. Is done. The surface of the paper transport belt 30 is charged to a predetermined potential by the suction roll 34. As a result, the paper P is electrostatically attracted onto the paper transport belt 30 and is transported along the paper transport path M1 by the paper transport belt 30 that circulates and moves in the direction of the arrow in FIG. In the middle of the process, the color toner images are sequentially transferred onto the paper P by the transfer electric field formed by the transfer roll 31.
The sheet P on which each color toner image is electrostatically transferred is peeled from the sheet conveying belt 30 downstream of the image forming unit 10K and conveyed to the fixing device 40. In the fixing device 40, the unfixed toner image on the paper P is fixed to the paper P by receiving a fixing process using heat and pressure. The paper P on which the color toner images are fixed is stacked on a paper discharge unit 90 provided in a discharge unit of the image forming apparatus 1. On the other hand, during double-sided printing, the same image forming operation is performed again via the double-sided conveyance path M2, and then the paper is stacked on the paper discharge unit 90.

Next, adjustment of the exposure position on the photosensitive drum 11 performed with respect to the laser exposure device 20 of the present embodiment will be described.
First, the configuration of the laser exposure device 20 of the present embodiment will be described. FIG. 2 is a side view showing a schematic configuration of the laser exposure device 20 of the present embodiment. As shown in FIG. 2, the laser exposure device 20 of the present embodiment includes a light source 21 composed of, for example, four semiconductor lasers, and a scanning optical system. As an optical member constituting the scanning optical system, four collimator lenses 22 and cylindrical lenses 23 provided corresponding to the respective laser beams (light beams) emitted from the light source 21, for example, a rotating polyhedron formed of a regular hexahedron. A mirror (polygon mirror) 24, a plurality of folding mirrors 25, and an fθ lens 26 are provided.
Further, the light source 21 and the scanning optical system provided in the laser exposure device 20 are arranged in a housing 27 as an example of a holding member. The housing 27 is provided with a dustproof window 28 made of, for example, a glass plate, at a portion where each color laser beam is emitted toward the photosensitive drum 11. As a result, the light source 21 and various optical members constituting the scanning optical system are sealed in the housing 27, and leakage of laser light to the outside and adhesion of dust and the like to the light source 21 and various optical members are suppressed.

In the laser exposure device 20 of the present embodiment, the four laser beams emitted from the light source 21 are converted into parallel beams by the collimator lenses 22 and are converted by the cylindrical lens 23 having a refractive power (power) only in the sub-scanning direction. A line image that is long in the main scanning direction is formed on the deflecting / reflecting surface 24a of the polygon mirror 24. Each laser beam is reflected by the deflecting / reflecting surface 24a of the polygon mirror 24 that rotates at a high speed at a constant speed, and is scanned at a constant angular velocity. Each laser beam passes through the fθ lens 26 and is redirected toward the surface of the photosensitive drum 11 by a plurality of folding mirrors 25, and from the dustproof window 28 to the surface of the photosensitive drum 11 of each image forming unit 10. Scanning exposure.
Here, the fθ lens 26 has a function of equalizing the scanning speed of the light spot of each of the four laser beams on the surface of the photosensitive drum 11.
Further, as described above, the four laser beams from the respective light sources 21 are formed as line images on the deflection reflection surface 24 a of the polygon mirror 24 by the cylindrical lens 23. Further, the fθ lens 26 forms an image of the light spot on the surface of the photosensitive drum 11 with the deflection reflection surface 24a as an object point in the sub-scanning direction. Thereby, the scanning optical system of the laser exposure device 20 has a function of correcting the surface tilt of the deflecting / reflecting surface 24a.

In addition to the light source 21 and the scanning optical system shown in FIG. 2, the laser exposure device 20 of the present embodiment is provided with a laser light detection system used for adjusting the exposure position of each color laser light. . FIG. 3 is a diagram for explaining a laser beam detection system used for adjusting the exposure position of each color laser beam, taking one laser beam among four laser beams as an example. In FIG. 3, the description of the folding mirror 25 is omitted for easy understanding.
As shown in FIG. 3, the laser exposure device 20 of the present embodiment has a laser beam detection system that detects the scanning start timing of each laser beam provided corresponding to each of the four laser beams. As an example of the start timing detection means, four SOS (Start of Scan) sensors (light receiving elements) 291, four reflection mirrors 292, and a laser drive circuit 29 are provided.
In FIG. 3, the constituent elements of the laser light detection system relating to one laser beam are shown, but similar constituent elements are also provided for the other three laser lights. Further, depending on the configuration of the scanning optical system, a common laser beam detection system may be used for a plurality of laser beams.

Each of the four laser beams enters the SOS sensor 291 via the reflection mirror 292 prior to scanning exposure on the surface of the photosensitive drum 11. That is, the first laser beam of each scanning line is incident on the SOS sensor 291 every time each color laser beam scans the surface of the photosensitive drum 11. The SOS sensor 291 detects the timing at which the laser beam starts scanning the photosensitive drum 11 (scanning start timing) for each scanning line, and serves as a reference signal for synchronizing the image writing timing of each scanning line ( Hereinafter, this is referred to as an “SOS signal”.
The SOS sensor 291 is connected to the control unit 80 and the laser drive circuit 29. Then, during normal image formation, the generated SOS signal is transmitted to the laser drive circuit 29. On the other hand, when calculating the output start timing adjustment amount described later, the generated SOS signal is transmitted to the laser drive circuit 29 and the control unit 80.
The laser drive circuit 29 acquires each color image data subjected to predetermined processing from the image processing unit 81. Then, a laser drive signal corresponding to each color image data is output to each light source 21 at a predetermined timing. That is, the laser drive circuit 29 is an example of a drive unit that drives the light source 21 made of a semiconductor laser. Note that the driving means is not limited to the case where the driving means is configured only by the laser driving circuit 29. For example, the laser driving circuit 29 includes a control unit 80 and other functional units to form a driving unit.

  Next, adjustment of the exposure position on the photosensitive drum 11 relating to the laser exposure device 20 of the present embodiment will be described. In the laser exposure device 20, there are usually variations such as component accuracy and assembly accuracy among various optical members constituting the above-described scanning optical system and laser light detection system. In addition, due to the temperature rise in the apparatus during the image forming operation, fluctuations occur in the component dimensions and assembly positions of various optical members, as well as optical performance and laser wavelength. For this reason, in each image forming unit 10, variations occur in the position where each color laser beam on the surface of each photosensitive drum 11 starts scanning (scanning start point position) and the position where scanning ends (scanning end point position). Therefore, in general, the exposure position is adjusted in order to match the scanning start point position and the scanning end point position. However, in order to detect both the scan start point position and the scan end point position on the photosensitive drum 11, it is necessary to provide detection means at both the scan start point position and the scan end point position. As a result, it has been an impediment to reducing the manufacturing cost of the image forming apparatus 1 conventionally.

Therefore, in the image forming apparatus 1 of the present embodiment, the scanning start point position of each color laser beam is within one scanning line of each laser driving signal in the laser driving circuit 29 based on the position adjustment data obtained in advance. By adjusting the output start timing, the variation in the scanning start point position of each color laser beam is reduced.
As for the scanning end point position of each color laser beam, a predetermined position correction pattern is formed on the paper conveyance belt 30 at a position corresponding to the scanning end point position, and the main scanning of the position correction pattern on the paper conveyance belt 30 is performed. Detect the direction position. Each color is adjusted by adjusting the output end timing (also referred to as “print width” or “image magnification”) of each laser drive signal within one scanning line based on the position in the main scanning direction of the detected position correction pattern. Variations in the scanning end point position of the laser light are reduced.
As a result, the number of detection means for detecting the position of the scanning line on the photosensitive drum 11 installed in the image forming apparatus 1 is minimized, thereby reducing the manufacturing cost of the image forming apparatus 1. Yes.

  Here, FIG. 4 is a block diagram showing an example of a functional configuration for adjusting the exposure position of the laser beam in the control unit 80. As shown in FIG. 4, the control unit 80 according to the present embodiment is a functional unit that adjusts the exposure position of the laser beam, and serves as an example of a scan start timing acquisition unit that receives an SOS signal input from the SOS sensor 291. An SOS signal input unit 801 and a position data input unit 802 as an example of a position information acquisition unit that receives input of position data related to a position correction pattern from the detection sensor 60 are provided. Further, a calculation unit 803 that calculates an adjustment amount (output start timing adjustment amount) related to the output start timing of image data for each light source 21, a memory that stores output start timing adjustment amount data generated by the calculation unit 803, and the like. As an example, a storage unit 804, an adjustment data output unit 805 that outputs output start timing adjustment amount data stored in the storage unit 804 to the laser drive circuit 29, an instruction signal for changing the image clock (image clock instruction signal) ) Is output to the laser drive circuit 29. The image clock instruction signal output unit 806 is provided.

Here, in the control unit 80, a main memory stores a program in which a CPU (not shown) realizes the functions of the SOS signal input unit 801, the position data input unit 802, the calculation unit 803, the adjustment data output unit 805, and the image clock instruction signal output unit 806. Various processes are performed by reading from the unit 82 into a ROM or the like in the control unit 80.
The “image clock” described above is a clock that serves as a reference when image data is read from a memory that stores image data, for example. The laser drive circuit 29 adjusts the output end timing (print width, image magnification) of each laser drive signal by changing the setting of the time required to output image data for one scanning line by adjusting the image clock. Do.

Subsequently, adjustment of the scanning start point position of each color laser beam will be described.
In the laser drive circuit 29 of the present embodiment, the output start timing of the laser drive signal corresponding to each color image data is set as follows. That is, the control unit 80 stores output start timing adjustment amount data as an example of adjustment data described later in a storage unit 804 provided in the control unit 80. For example, when the main switch of the image forming apparatus 1 is turned on, the control unit 80 downloads the output start timing adjustment amount data stored in the storage unit 804 to the laser driving circuit 29. Therefore, the control unit 80 also functions as an instruction unit that instructs setting of the output start timing.
The laser drive circuit 29 stores the output start timing adjustment amount data acquired from the control unit 80 in a storage unit (not shown) provided in the laser drive circuit 29. At the time of image formation, the laser drive circuit 29 starts outputting the laser drive signal to each light source 21 based on the SOS signal acquired from the SOS sensor 291 and the output start timing adjustment amount data stored in the storage unit. Set the timing (output start timing).

  Here, the output start timing adjustment amount data stored in the storage unit 804 of the control unit 80 will be described. In the image forming apparatus 1 according to the present embodiment, for example, the output start timing adjustment amount for each light source 21 is calculated by the control unit 80 before the image forming apparatus 1 is shipped from the factory, and the output start timing adjustment amount data is stored in the storage unit. Stored in 804. The image forming apparatus 1 is shipped from the factory with the output start timing adjustment amount data stored in the storage unit 804.

When the image forming apparatus 1 according to the present embodiment is shipped from the factory as a finished product, the detection sensor 60 is located at a position facing the region where the paper transport belt 30 is stretched over the drive roll 32, and each image The forming unit 10 is disposed at the position in the width direction of the sheet conveying belt 30 corresponding to the scanning end point position on the surface of the photosensitive drum 11 (this is referred to as “first arrangement position”) (see FIG. 12 in the subsequent stage). ).
In contrast, as shown in FIG. 5 (a diagram illustrating a state in which the detection sensor 60 has been moved from the first arrangement position to the second arrangement position), the image forming apparatus 1 is not yet shipped from the factory. The detection sensor 60 is removed from the first arrangement position. Then, the detection sensor 60 is moved to a position corresponding to the scanning start position of the laser beam on the surface of each photosensitive drum 11 (this is referred to as a “second arrangement position”). The detection sensor 60 is installed at the second arrangement position by a holding member (not shown) so as to maintain the same positional relationship as that between the detection sensor 60 and the paper transport belt 30 at the first arrangement position. .

As a method of installing the detection sensor 60 at the second arrangement position, a method of providing a holding member on the main body side of the image forming apparatus 1 or a method of using a holding jig is used. Further, as a method of moving the detection sensor 60, a jig may be used in addition to the manual method. Furthermore, in the present embodiment, the same detection sensor 60 installed at the first arrangement position is used as the detection sensor 60 installed at the second arrangement position, but the second arrangement position is used. Different detection means may be used as installed.
Further, the second arrangement position is set to any position as long as it is an area on the photosensitive drum 11 on the scanning start point position side from the center of scanning which is an intermediate position between the scanning start point position and the scanning end point position. May be.

  The output start timing adjustment amount data is generated as follows. First, the image forming apparatus 1 in which the detection sensor 60 is installed at the second arrangement position is operated in a factory where, for example, the temperature environment is maintained in a predetermined state before shipment from the factory. Then, each image forming unit 10 forms a position correction pattern made up of each color toner image of a predetermined pattern on the paper transport belt 30 corresponding to the second arrangement position. The detection sensor 60 installed at the second arrangement position detects the position of each position correction pattern on the paper transport belt 30. The detected position of the position correction pattern is transmitted to the control unit 80 as position data of the position correction pattern. In the control unit 80, the position data input unit 802 acquires the position data of the position correction pattern and sends it to the calculation unit 803.

  At the same time, the control unit 80 detects the reception timing for receiving the SOS signal sent from each SOS sensor 291. Specifically, in the control unit 80, the SOS signal input unit 801 acquires the SOS signal from each SOS sensor 291. Then, information indicating the reception timing of the SOS signal is sent to the calculation unit 803. The calculation unit 803 uses the reception timing of the SOS signal with the black laser beam as a reference signal, and the relative time difference Tk1 (black), Tc1 (cyan), Tm1 between the reference signal and the reception timing of the SOS signal with each color laser beam. (Magenta) and Ty1 (yellow) are calculated (see FIG. 6 in the subsequent stage). The time differences Tk1 (= 0), Tc1, Tm1, and Ty1 are examples of information related to the scan start timing. For example, the time differences Tk1 (= 0), Tc1, Tm1, and Ty1 The reference time of the SOS signal is stored in the storage unit 804.

The calculation of the reference times Tk1, Tc1, Tm1, Ty1 of each SOS signal here is performed, for example, by counting the reference clock in the control unit 80. That is, the arithmetic unit 803 of the control unit 80 starts the counting operation by the reference clock by acquiring the reference signal (here, the SOS signal of the black laser light) from the laser driving circuit 29, and before receiving each SOS signal. Reference times Tk1, Tc1, Tm1, and Ty1 are calculated from the counted number of reference clocks. Then, the reference times Tk1, Tc1, Tm1, and Ty1 are stored in the storage unit 804 as an example of information related to the scan start timing.
The reference time of each SOS signal here is used to adjust the output timing shift of the SOS signal during the image forming operation described later.
The reference signal may be any signal as long as it is a reference for calculating the time differences Tk1, Tc1, Tm1, Ty1 from the reception timing of each SOS signal. For example, the reception timing of the SOS signal with yellow laser light may be used as the reference signal.

FIG. 6 is a timing chart for explaining the SOS signal reception timing of each color laser beam and the output start timing of the laser drive signal (image signal) at the initial setting before factory shipment.
As described above, various optical members constituting the scanning optical system and laser light detection system of the laser exposure device 20 have variations in component accuracy and assembly accuracy. Therefore, as shown in FIG. 6, the timing (reference time Tk1, Tc1, Tm1, Ty1) at which the SOS signal is received from each SOS sensor 291 in the laser drive circuit 29 has a unique value that differs for each color laser beam. Have. On the other hand, the time Tk2, Tc2, Tm2, and Ty2 from the reception timing of the SOS signal to the output of each image signal in the laser driving circuit 29 is the same time (design value) when the image forming apparatus 1 is initially set. Is set. That is, Tk2 = Tc2 = Tm2 = Ty2 is set as a design value. For this reason, the reference times Tk1, Tc1, Tm1, and Ty1 each having a unique value are affected, and the timing at which the image signals in the respective color laser beams are output varies. As a result, the scanning start point position on the surface of the photosensitive drum 11 of each image forming unit 10 varies.

FIG. 7 is a diagram for explaining the variation of the scanning start point position on the surface of each photosensitive drum 11 at the time of initial setting. As shown in FIG. 7, the timing (reference time Tk1, Tc1, Tm1, Ty1) at which each SOS signal is received by each SOS sensor 291 has a unique value and the image signal is output. Since the time Tk2 = Tc2 = Tm2 = Ty2 is set, the scan start point position on the surface of each photosensitive drum 11 is shifted. For example, assuming that the scanning start point position of the black laser light on the paper P is the reference position on the scanning start side, cyan laser light, magenta laser light, and yellow laser light are each on the paper P. A positional deviation amount of ΔDc, ΔDm, ΔDy occurs. These misregistration amounts ΔDc, ΔDm, and ΔDy cause color misregistration on the image.
The positional deviation amounts ΔDc, ΔDm, and ΔDy for the cyan laser light, magenta laser light, and yellow laser light are respectively the time deviation amounts of the output start timing of the image signal on the timing chart of FIG. Appears as That is, the time shift amount of the output start timing of the image signal of each color laser beam corresponds to the positional shift amount ΔDc, ΔDm, ΔDy on the paper P, and ΔTc2 for magenta laser light, magenta laser For light, ΔTm2, and for yellow laser light, ΔTy2. In FIG. 6, the position on the timing chart of the output start timing of the image signal for the black laser light (scanning start point side reference position on the paper P) is indicated by a broken line as “SOS (Start of Scan) side reference”. Show.

On the other hand, in the control unit 80 that has acquired the position correction pattern position data transmitted from the second arrangement position detection sensor 60 described above, the calculation unit 803 generates a black color based on the position correction pattern position data of each color. The positional deviation amount of the position correction pattern for each color with respect to the position correction pattern is calculated. The calculated positional deviation amount of the position correction pattern corresponds to the positional deviation amounts ΔDc, ΔDm, ΔDy in FIG. Based on the calculated positional deviation amount (deviation amounts L1, L2, and L3 in 45 ° inclination patterns LK, LC, LM, and LY in FIG. 11 to be described later), the control unit 80 displays the timing chart of FIG. The time shift amounts ΔTc2, ΔTm2, and ΔTy2 of the output start timing of the image signals with the respective color laser beams are calculated.
That is, the calculation unit 803 of the control unit 80 determines the time shift related to the output start timing of the image signal based on the calculated positional shift amount of the position correction pattern for each color and the scanning speed of the laser beam on the surface of the photosensitive drum 11. The amounts ΔTc2, ΔTm2, and ΔTy2 are obtained as output start timing adjustment amount data ΔTk2, ΔTc2, ΔTm2, and ΔTy2 as an example of adjustment data. When obtaining the output start timing adjustment amount data, for example, the positional relationship between the photosensitive drum 11 and the paper conveyance belt 30 is taken into consideration. The obtained output start timing adjustment amount data ΔTk2, ΔTc2, ΔTm2, and ΔTy2 are stored in the storage unit 804. In the present embodiment, since the output start timing of the image signal with the black laser light is set as a reference, the output start timing adjustment amount data regarding the black laser light is ΔTk2 = 0.

  When the image forming apparatus 1 actually operates in the market, the laser drive circuit 29 outputs the output start timing adjustment amount data ΔTk2 (= 0), ΔTc2, ΔTm2, Δ from the storage unit 804 of the control unit 80. Get Ty2. For example, the image data is downloaded from the adjustment data output unit 805 to the laser drive circuit 29 when the main switch of the image forming apparatus 1 is turned on. Then, the laser drive circuit 29 uses the output start timing adjustment amount data ΔTk2, ΔTc2, ΔTm2, and ΔTy2 to determine the time Tk2, Tc2 from the actual SOS signal reception timing to the output of each image signal. , Tm2, Ty2 are adjusted to reduce the amount of deviation of the scanning start point position of each color laser beam.

Specifically, assuming that the time (after adjustment) until each laser drive signal after adjustment is output is Tk2 ′, Tc2 ′, Tm2 ′, Ty2 ′, the laser drive circuit 29 has the following ( The post-adjustment times Tk2 ′, Tc2 ′, Tm2 ′, Ty2 ′ are calculated by the calculations of equations 1) to (4). Here, the adjustment amount of the laser beam in the scanning direction is positive.
Tk2 ′ = Tk2 (1)
Tc2 ′ = Tc2 + ΔTc2 (2)
Tm2 ′ = Tm2 + ΔTm2 (3)
Ty2 ′ = Ty2 + ΔTy2 (4)

The laser drive circuit 29 changes the setting of the time from when the SOS signal is received until each laser drive signal is output to the adjusted time Tk2 ′, Tc2 ′, Tm2 ′, Ty2 ′.
FIG. 8 is a timing chart showing a state in which the timing at which each image signal is output is set to the adjusted time Tk2 ′, Tc2 ′, Tm2 ′, Ty2 ′ in the laser driving circuit 29. As shown in FIG. 8, by using the adjusted times Tk2 ′, Tc2 ′, Tm2 ′, and Ty2 ′, the deviation of the output start timing of each image signal is adjusted. As a result, as shown in FIG. 9 (a diagram for explaining the scan start point position on the surface of each adjusted photosensitive drum 11), the amount of deviation of the scan start point position generated in each image forming unit 10 is reduced. The

Here, a procedure in which the detection sensor 60 installed at the second arrangement position generates position data of the position correction pattern will be described.
First, the control unit 80 instructs each image forming unit 10 to form a position correction pattern made up of each color toner image of a predetermined pattern. Further, the detection sensor 60 is instructed to detect the position of the position correction pattern transferred onto the paper transport belt 30 on the paper transport belt 30.
FIG. 10 is a diagram illustrating an example of the configuration of the detection sensor 60 of the present embodiment. As shown in FIG. 10, the detection sensor 60 emits light along the width direction of the paper transport belt 30 (direction perpendicular to the moving direction of the paper transport belt 30), for example, a light emitting element 61 such as an LED, and the light emitting element. A light receiving element 63 configured to receive, for example, a photodiode, and the like, and a condenser lens 62 that condenses the light reflected from the paper transport belt 30 on the light receiving element 63. Has been. In other words, in the detection sensor 60 of the present embodiment, light is emitted from the light emitting element 61 along the width direction of the paper conveyance belt 30 and from the position correction pattern held on the paper conveyance belt 30 along the width direction. The reflected light is condensed on the light receiving element 63 by the condenser lens 62. Then, the position of the position correction pattern on the paper transport belt 30 is detected by the light received by the light receiving element 63. The detected position of the position correction pattern is transmitted to the control unit 80 as position data of the position correction pattern.

As the light receiving element 63, besides a photodiode or the like, a position detecting element (PSD: Position Sensitive Detector) can also be used. PSD performs measurement in units of several μm with a high-speed response of about 0.1 μsec, and is suitable for detecting a position correction pattern.
Further, the detection sensor 60 of the present embodiment detects the position of the position correction pattern transferred onto the paper transport belt 30 on the paper transport belt 30, but the photosensitive drum 11 is sensitive to the position correction pattern. You may comprise so that the position on the body drum 11 may be detected.

FIG. 11 is a diagram illustrating an example of a position correction pattern. In each image forming unit 10 of the present embodiment, a position correction pattern as shown in FIG. 11 is formed.
As shown in FIG. 11, the image forming unit 10 </ b> K forms a black parallel pattern PK and a 45 ° inclined pattern LK, which serve as a reference when the scanning start point positions of the respective color laser beams are matched in the present embodiment. . Further, the image forming unit 10C forms a cyan parallel pattern PC and a 45 ° inclined pattern LC. The image forming unit 10M forms a magenta parallel pattern PM and a 45 ° inclined pattern LM. The image forming unit 10Y forms a yellow parallel pattern PY and a 45 ° inclined pattern LY. In each image forming unit 10, the image forming timing is controlled so that the position correction patterns are formed in the order shown in FIG.

For adjusting the shift amount of the scanning start point position, 45 ° inclination patterns LK, LC, LM, LY are used. That is, after the position adjustment of the scanning line of each color laser beam in the sub-scanning direction using parallel patterns PK, PC, PM, and PY, which will be described later, is performed, the detection sensor 60 is subjected to a 45 ° inclined pattern LK by the light receiving element 63. , LC, LM, and LY are detected in the width direction of the sheet conveying belt 30. Then, the detected position is sent to the control unit 80 as position data in the main scanning direction. The control unit 80 calculates the shift amounts of the 45 ° inclination patterns LC, LM, and LY with reference to the position in the width direction of the 45 ° inclination pattern LK. That is, as shown in FIG. 11, the shift amount L1 between the 45 ° tilt pattern LK and the 45 ° tilt pattern LC, the shift amount L2 between the 45 ° tilt pattern LK and the 45 ° tilt pattern LM, and the 45 ° tilt pattern LK A deviation amount L3 from the 45 ° inclination pattern LY is calculated. Then, the control unit 80 converts the calculated deviation amounts L1, L2, and L3 into time by using the scanning speed of the laser beam on the surface of the photosensitive drum 11 and the like, thereby outputting the output start timing correction amount. Data ΔTk2, ΔTc2, ΔTm2, and ΔTy2 are calculated.
The calculated shift amounts L1, L2, and L3 in the 45 ° tilt patterns LK, LC, LM, and LY correspond to the positional shift amounts ΔDc, ΔDm, and ΔDy shown in FIG. is there.

Subsequently, adjustment of the scanning end point position of each color laser beam will be described.
In the image forming apparatus 1 of the present embodiment, when the image forming apparatus 1 is shipped from the factory, the detection sensor 60 corresponds to the scanning end point position on the surface of the photosensitive drum 11 of each image forming unit 10. The sheet conveying belt 30 is fixed to a position in the width direction (first arrangement position) by a fixing member (not shown). Note that the first arrangement position is set to any position as long as it is an area on the photosensitive drum 11 on the scanning end position side from the scanning central portion, which is an intermediate position between the scanning start point position and the scanning end point position. May be.
In the image forming apparatus 1 of the present embodiment, the output end timing of each laser drive signal (printing width, image, etc.) at a predetermined interval (time interval, number of prints, etc.) when the apparatus is started up or during the image forming operation. Magnification) is adjusted to reduce the variation in the scanning end position of each color laser beam.

  The adjustment of the output end timing of each laser drive signal in the image forming apparatus 1 of the present embodiment is performed, for example, during a non-image forming operation between the image forming operation and the image forming operation. Here, FIG. 12 is a diagram showing a state in which the detection sensor 60 installed at the first arrangement position detects the position of the position correction pattern on the paper transport belt 30. At the time of adjusting the output end timing of each laser drive signal, a position correction pattern made up of each color toner image shown in FIG. 11 is formed on the paper transport belt 30 corresponding to the first arrangement position. Then, the position of the position correction pattern on the paper transport belt 30 is detected by the detection sensor 60 installed at the first arrangement position. The detected position of the position correction pattern is transmitted to the control unit 80 as position data of the position correction pattern.

  When adjusting the output end timing of each laser drive signal, the position of each color laser beam in the sub-scanning direction is adjusted using the parallel patterns PK, PC, PM, and PY described later, and then the detection sensor 60 The light receiving element 63 detects the positions of the 45 ° inclined patterns LK, LC, LM, LY in the width direction of the sheet conveying belt 30. The detected position is sent to the control unit 80 as position data in the main scanning direction at the scanning end point position of each color laser beam. The control unit 80 calculates the shift amounts of the 45 ° inclination patterns LC, LM, and LY with reference to the position in the width direction of the 45 ° inclination pattern LK. That is, as shown in FIG. 11, the positional deviation amount L1 between the 45 ° inclination pattern LK and the 45 ° inclination pattern LC, the positional deviation amount L2 between the 45 ° inclination pattern LK and the 45 ° inclination pattern LM, and the 45 ° inclination pattern. A positional deviation amount L3 between LK and 45 ° inclined pattern LY is calculated.

FIG. 13 is a timing chart for explaining the SOS signal reception timing of each color laser beam and the image signal output end timing Tk3, Tc3, Tm3, Ty3 before the scanning end point position adjustment. In FIG. 13, the output end timings Tk3, Tc3, Tm3, and Ty3 of the image signal are represented as the time from the SOS signal of each color laser beam.
As described above, various optical members constituting the scanning optical system and laser light detection system of the laser exposure device 20 have variations in component accuracy and assembly accuracy. In addition, due to the temperature rise in the apparatus during the image forming operation, fluctuations occur in the component dimensions and assembly positions of various optical members, as well as optical performance and laser wavelength. Therefore, as shown in FIG. 13, the print width (image magnification) on the surface of the photosensitive drum 11 from the start to the stop of the output of the image signal in the laser drive circuit 29 is different for each color laser beam. It becomes. As a result, variation occurs in the scanning end point position on the surface of the photosensitive drum 11 of each image forming unit 10.

  Here, the “EOS (End of Scan) side reference” shown in FIG. 13 is a timing chart on which each color laser beam passes through a position on the surface of each color photosensitive drum 11 corresponding to the scanning end point position of the black laser beam. It is expressed as the position of. Accordingly, for example, the deviation of the scanning end point position of each color laser beam when the scanning end point position of the black laser beam is used as a reference is the output end timing Tk3, Tc3, Tm3, Ty3 of the image signal on the timing chart of FIG. Appears as a time difference from the EOS side reference. That is, the shift of the scanning end point position of each color laser beam is a time shift amount of ΔTc3 for the cyan laser beam, ΔTm3 for the magenta laser beam, and ΔTy3 for the yellow laser beam. Become.

On the other hand, the time shift amounts ΔTc3, ΔTm3, and ΔTy3 for each color laser beam shown in the timing chart of FIG. 13 are the shift amounts L1 of the position correction patterns for the respective colors calculated by the calculation unit 803 of the control unit 80. , L2, L3.
Therefore, the calculation unit 803 outputs image signal output end timings Tk3, Tc3 based on the calculated displacement amounts L1, L2, L3 of the position correction patterns for the respective colors and the scanning speed of the laser light on the surface of the photosensitive drum 11. , Tm3, Ty3, adjustment amount data ΔTk3, ΔTc3, ΔTm3, ΔTy3 are obtained. When obtaining the adjustment amount data related to the output end timing, for example, the positional relationship between the photosensitive drum 11 and the paper transport belt 30 is taken into consideration. In the present embodiment, since the output end timing of the image signal with the black laser light is set as a reference, the adjustment amount data regarding the output end timing of the black image signal is ΔTk3 = 0.

Based on the adjustment amount data ΔTk3, ΔTc3, ΔTm3, ΔTy3, the calculation unit 803 is an image in which the time difference between the output end timings Tk3, Tc3, Tm3, Ty3 of the image signal and the EOS side reference is “0”. Calculate the clock. Then, an instruction signal (image clock instruction signal) for changing the image clock is output to the laser driving circuit 29. Therefore, the control unit 80 also functions as an instruction unit that instructs setting of the output end timing. The laser drive circuit 29 outputs an image signal with an image clock corresponding to the image clock instruction signal.
FIG. 14 is a diagram illustrating a timing chart in a state where the image clock is adjusted in the laser driving circuit 29. As shown in FIG. 14, the time required to output the image signal for one scanning line is adjusted (magnification correction), so that the output end timing of each image signal is the output end timing Tk3 ′, Tc3 ′, Tm3. ', Ty3'. Thereby, the deviation of the output end timings Tk3 ′, Tc3 ′, Tm3 ′, Ty3 ′ is adjusted, and the deviation amount of the scanning end point position generated in each image forming unit 10 is reduced.
In adjusting the image clock, a method of changing the frequency of the image clock or a method of shifting the phase is used.
Further, when adjusting the print width, the image processing unit 81 may perform thinning or interpolation of the image signal.

Here, the position adjustment of the scanning lines of each color laser beam in the sub-scanning direction will be described. When adjusting the position of each color laser beam in the sub-scanning direction, the detection sensor 60 detects the position of each of the parallel patterns PK, PC, PM, and PY on the paper transport belt 30 by the light receiving element 63. The obtained position is sent to the control unit 80 as sub-scanning direction position data. For example, using the timing at which the sub-scanning direction position data is transmitted, the control unit 80 calculates the time interval of the timing at which each of the other color parallel patterns PC, PM, PY passes the detection sensor 60 using the parallel pattern PK as a reference. . That is, as shown in FIG. 11, the time interval P1 between the passage timing of the parallel pattern PK and the passage timing of the parallel pattern PC, the time interval P2 between the passage timing of the parallel pattern PK and the passage timing of the parallel pattern PM, the parallel pattern A time interval P3 between the passage timing of PK and the passage timing of parallel pattern PY is calculated. Then, the control unit 80 adjusts the exposure positions in the sub-scanning direction of the laser light from the laser exposure device 20 in each of the image forming units 10 based on the calculated time intervals.
As described above, in the image forming apparatus 1 according to the present embodiment, the exposure position in the main scanning direction and the sub-scanning direction on the photosensitive drum 11 with respect to the laser exposure device 20 is detected using one detection sensor 60. Adjustments are made.

By the way, the various optical members constituting the scanning optical system and the laser light detection system of the laser exposure device 20 are subject to fluctuations in component dimensions and assembly position due to the temperature rise in the apparatus during the image forming operation. Variations in optical performance, laser wavelength, etc. occur. Therefore, there may be a deviation in the output timing of the SOS signal in each SOS sensor 291. In that case, even if the adjusted time Tk2 ′, Tc2 ′, Tm2 ′, Ty2 ′ for adjusting the deviation between the output start timing of the image signal and the SOS side reference is used, the output start timing of the image signal is shifted. Will occur.
Further, for the same reason, the print width (image magnification) on the surface of the photosensitive drum 11 from the start to the stop of the output of the image signal in the laser drive circuit 29 also varies.
FIG. 15 is a diagram showing a timing chart in the case where the output timing shift of the SOS signal and the fluctuation of the print width occur. As shown in FIG. 15, when a shift in the output timing of the SOS signal and a change in the print width occur, a shift between the output start timing of the image signal and the SOS side reference, and the output end timing of the image signal and the EOS Both deviation from the side reference occurs.

Therefore, for example, when the in-machine temperature of the image forming apparatus 1 or the temperature in the laser exposure device 20 exceeds a predetermined temperature, the control unit 80 is the initial setting of the image forming apparatus 1 stored in the storage unit 804 ( The reference time Tk1 (= 0), Tc1, Tm1, Ty1 of each SOS signal under a predetermined temperature environment) is sent to the laser drive circuit 29.
The laser drive circuit 29 performs a process of correcting the SOS signal transmitted from each SOS sensor 291 based on the reference times Tk1, Tc1, Tm1, and Ty1. Then, an image signal is output using the adjusted times Tk2 ′, Tc2 ′, Tm2 ′, Ty2 ′ with the corrected SOS signal (corrected SOS signal) as a reference. For this reason, even when a deviation occurs in the output timing of the SOS signal, the image signal is output at the same timing as the initial setting of the image forming apparatus 1. Thereby, the deviation between the output start timing of the image signal and the SOS side reference is reduced.
Further, regarding the adjustment of the output end timings Tk3, Tc3, Tm3, and Ty3 of each image signal, the adjustment based on the position data of the position correction pattern from the detection sensor 60 is performed as described above. Thereby, the deviation between the output end timing of the image signal and the EOS side reference is reduced.

  In this case, the control unit 80 downloads the reference times Tk1, Tc1, Tm1, and Ty1 of each SOS signal stored in the storage unit 804 to the laser drive circuit 29 in advance when the image forming apparatus 1 is initially set. Alternatively, the above adjustment process may be performed when the reception timing of the actually detected SOS signal deviates from the reference time of each SOS signal.

  FIG. 16 is a timing chart when the output start timing and the output end timing of the image signal are determined based on the corrected SOS signal. As shown in FIG. 16, even when the SOS signal transmitted from each SOS sensor 291 shifts or the print width varies, the shift between the output start timing of the image signal and the SOS side reference, and the image signal Deviation between the output end timing and the EOS side reference is reduced.

As described above, in the image forming apparatus 1 of the present embodiment, the output start timing of each laser drive signal in the laser drive circuit 29 is the output start timing of each light source 21 stored in the storage unit 804 in advance. Make adjustments based on the adjustment amount. Further, the output end timing of each laser drive signal is adjusted based on the position data of the position correction pattern from the detection sensor 60.
As a result, the exposure position can be adjusted by providing a minimum number of position correction pattern detection means, and the exposure position adjustment mechanism in the exposure apparatus can be made inexpensive.

[Embodiment 2]
In the first embodiment, the configuration in which the output start timing of each laser beam in the main scanning direction is adjusted based on the adjustment amount related to the output start timing in each light source 21 stored in advance in the storage unit 804 has been described. In the present embodiment, a configuration in which the output start timing of each laser beam in the sub-scanning direction is similarly adjusted based on the adjustment amount related to the output start timing in each light source 21 stored in advance in the storage unit 804 will be described. . In addition, the same code | symbol is used about the structure similar to Embodiment 1, and the detailed description is abbreviate | omitted here.

In the laser drive circuit 29 of the present embodiment, the output timing of the synchronization signal (Vsync) for setting the write start timing on the paper P in each image forming unit 10 is set as follows. That is, the control unit 80 stores Vsync output timing adjustment amount data as an example of adjustment data described later in a storage unit 804 as an example of a storage unit provided in the control unit 80. Then, the control unit 80 adjusts the output timing of Vsync.
The laser drive circuit 29 acquires the adjusted Vsync (adjustment Vsync) from the control unit 80 during image formation. The laser drive circuit 29 starts writing on the paper P based on the SOS signal acquired from the SOS sensor 291 and the adjustment Vsync acquired from the control unit 80.

FIG. 17 is a timing chart showing the relationship between Vsync for setting the writing timing in each image forming unit 10 and each color image forming area. As shown in FIG. 17, in the laser drive circuit 29 of each image forming unit 10, each image forming unit 10 is arranged at a different position along the paper transport belt 30, and thus each image forming unit 10 is provided with each image forming unit 10. The output start timing of the image signal is set by the first SOS signal after Vsync is output.
That is, the control unit 80 uses the predetermined reference signal (trigger signal) as a reference for a predetermined time from the trigger signal so that image formation is performed in order from the image forming unit 10 positioned upstream in the conveyance direction of the paper conveyance belt 30. Later, Vsync is output to each image forming unit 10. Here, as TVy1 <TVm1 <TVc1 <TVk1, yellow (Y) Vsync is output after time TVy1 from the trigger signal, and similarly, magenta (M) Vsync after time TVm1 from the trigger signal, and cyan after time TVc1 from the trigger signal. (C) Vsync and black (K) Vsync are output after a time TVk1 from the trigger signal. Then, each image forming unit 10 starts outputting an image signal as shown in FIG. 8, for example, upon receiving Vsync. In FIG. 17, an area on the timing chart where an image signal is output to each image forming unit 10 is expressed as each color image forming area.

However, in the image forming apparatus 1, there are variations in the arrangement positions of the image forming units 10 in the conveyance direction of the paper conveyance belt 30, variations in the arrangement positions of the components in the image forming units 10, and the like. Therefore, the position adjustment in the sub-scanning direction of each color laser beam is usually performed at a predetermined timing during image formation using the parallel patterns PK, PC, PM, and PY shown in FIG. 11 with reference to the output timing of Vsync. Is going. However, since a predetermined time is required for the position adjustment in the sub-scanning direction using the parallel patterns PK, PC, PM, and PY, it is one of the factors that reduce the image productivity.
Therefore, in the image forming apparatus 1 according to the embodiment, Vsync output timing adjustment amount data for adjusting the output timing of Vsync is stored in the storage unit 804 provided in the control unit 80. At the time of image formation, the control unit 80 adjusts the Vsync output timing based on the Vsync output timing adjustment amount data stored in the storage unit. The laser driving circuit 29 sets the writing timing in the sub-scanning direction on the paper P based on the SOS signal acquired from the SOS sensor 291 and the adjustment Vsync acquired from the control unit 80. This simplifies the position adjustment of each color laser beam in the sub-scanning direction at the time of image formation, and suppresses a decrease in image productivity.

  In the image forming apparatus 1 of the present embodiment, in order to generate the Vsync output timing adjustment amount data, each SOS sensor 291 as an example of the scan start timing detection unit is, for example, a two-dimensional direction such as a position detection element (PSD). A sensor capable of detecting the position of the laser beam is used. Each SOS sensor 291 detects data relating to the passage position of the laser beam in the sub-scanning direction (sub-scanning direction position data) in addition to the passage timing of the laser beam in the main scanning direction.

Here, FIG. 18 and FIG. 19 are diagrams showing an example of a sensor that can detect the position of laser light in a two-dimensional direction other than the position detection element (PSD). In FIG. 18, the SOS sensor 291 is configured using a photodiode formed in a triangular shape having a length in the main scanning direction along the sub-scanning direction (FIG. 18A). With such a configuration, the output waveform of the signal from the SOS sensor 291 differs depending on the position (a, b, c) of the laser light passing through the photodiode as shown in FIG. Different signals are obtained. Thereby, the sub-scanning direction position of each scanning line is detected.
Note that, as the SOS sensor 291 using a photodiode, the photodiode itself has a shape having the same length in the main scanning direction along the sub-scanning direction such as a square, and the like in the main scanning direction along the sub-scanning direction. You may comprise so that the surface of a photodiode may be covered with the mask which has the opening formed in the triangle shape where length becomes long.
In FIG. 19, a line CCD (Charge Coupled Devices) arranged in a line along the sub-scanning direction is used as the SOS sensor 291 (FIG. 19A). With such a configuration, as shown in FIG. 19B, output signals having different output timings from the SOS sensor 291 are obtained according to the positions (a, b, c) of the laser light passing through the line CCD. Thereby, the sub-scanning direction position of each scanning line is detected.
Such a SOS sensor 291 detects not only the main scanning direction but also the passing position of the laser beam in the sub-scanning direction.

On the other hand, as described above, the detection sensor 60 as an example of the detection unit is moved to the second arrangement position before the image forming apparatus 1 is shipped from the factory, and is moved to the second arrangement position by a holding member (not shown). Install. The Vsync output timing adjustment amount data is generated as follows.
First, the image forming apparatus 1 in which the detection sensor 60 is installed at the second arrangement position is operated in a factory where, for example, the temperature environment is maintained in a predetermined state before shipment from the factory. Then, each image forming unit 10 forms, for example, the position correction pattern shown in FIG. 11 on the paper conveyance belt 30 corresponding to the second arrangement position. The detection sensor 60 installed at the second arrangement position detects the position of each of the parallel patterns PK, PC, PM, and PY in the position correction pattern on the paper transport belt 30 and determines the detected position. The data is sent to the control unit 80 as sub-scanning direction position data. For example, using the timing at which the sub-scanning direction position data is transmitted, the control unit 80 calculates the time interval of the timing at which each of the other color parallel patterns PC, PM, PY passes the detection sensor 60 using the parallel pattern PK as a reference. .

  That is, as shown in FIG. 11, the time interval P1 between the passage timing of the parallel pattern PK and the passage timing of the parallel pattern PC, the time interval P2 between the passage timing of the parallel pattern PK and the passage timing of the parallel pattern PM, the parallel pattern A time interval P3 between the passage timing of PK and the passage timing of parallel pattern PY is calculated. Based on the calculated time interval and the conveyance speed of the sheet conveyance belt 30, the control unit 80 adjusts the time shift amounts ΔTVy1, ΔTVm1, ΔTVc1, and ΔTVk1 related to the output timing of Vsync as adjustment data. Vsync output timing adjustment amount data ΔTVy1, ΔTVm1, ΔTVc1, ΔTVk1 as an example. When obtaining the Vsync output timing adjustment amount data, for example, the positional relationship between each image forming unit 10 and the sheet conveying belt 30 is taken into consideration. Then, the obtained Vsync output timing adjustment amount data ΔTVy1, ΔTVm1, ΔTVc1, ΔTVk1 is stored in the storage unit 804. In this embodiment, since the Vsync output timing for the black image forming unit 10K is set as a reference (sub-scanning position reference), the Vsync output timing adjustment amount data for the black image forming unit 10K is ΔTVk1. = 0.

20 is based on the time interval P1 relating to the passage timing of the parallel pattern PC, the time interval P2 relating to the passage timing of the parallel pattern PM, the time interval P3 relating to the passage timing of the parallel pattern PY, and the conveyance speed of the paper conveyance belt 30. It is the figure which showed the time shift amount (DELTA) TVy1, (DELTA) TVm1, (DELTA) TVc1, and (DELTA) TVk1 regarding the output timing of Vsync calculated.
The time lag amounts ΔTVy1, ΔTVm1, ΔTVc1, and ΔTVk1 shown in FIG. 20 are on the sheet conveying belt 30 of each of the parallel patterns PK, PC, PM, and PY of the position correction pattern detected by the detection sensor 60. This corresponds to the amount of misalignment.

Therefore, in the image forming apparatus 1 of the embodiment, at the time of image formation, the control unit 80 adjusts the output timing of Vsync based on the Vsync output timing adjustment amount data stored in the storage unit 804. Therefore, the control unit 80 also functions as an instruction unit that instructs setting of the output timing of Vsync.
Here, FIG. 21 is a diagram for explaining the adjusted Vsync. As shown in FIG. 21, the control unit 80 determines the output timing of Vsync from the trigger signal based on the Vsync output timing adjustment amount data ΔTVy1, ΔTVm1, ΔTVc1, and ΔTVk1, respectively, TVy1 ′, TVm1 ′, The setting is changed to TVc1 ′, TVk1 ′ (= TVk1). Then, the writing timing in the sub-scanning direction on the paper P is set. This simplifies the position adjustment of each color laser beam in the sub-scanning direction at the time of image formation, and suppresses a decrease in image productivity.

As described above, in the image forming apparatus 1 of the present embodiment, the output start timings of the respective laser drive signals in the laser drive circuit 29 in both the main scanning direction and the sub-scanning direction are stored in the storage unit 804 in advance. Adjustment based on the adjustment amount related to the output start timing of each light source 21 is performed. Further, the output end timing of each laser drive signal is adjusted based on the position data of the position correction pattern from the detection sensor 60.
As a result, the exposure position can be adjusted by providing a minimum number of position correction pattern detection means, and the exposure position adjustment mechanism in the exposure apparatus can be made inexpensive. In addition, a decrease in image productivity is suppressed.

1 is a diagram illustrating an example of a configuration of an image forming apparatus to which the exemplary embodiment is applied. It is a side view which shows schematic structure of a laser exposure apparatus. It is a figure explaining the laser beam detection system used for adjustment of the exposure position of each color laser beam. It is the block diagram which showed an example of the function structure which adjusts the exposure position of the laser beam in a control part. It is a figure explaining the state where the detection sensor was moved to the 2nd arrangement position from the 1st arrangement position. It is the figure which showed the timing chart explaining the reception start timing of the SOS signal of each color laser beam at the time of the initial setting before factory shipment, and the output start timing of a laser drive signal (image signal). FIG. 6 is a diagram for explaining variation in scanning start point position on the surface of each photosensitive drum at the time of initial setting. It is the figure which showed the timing chart of the state where the timing which each image signal is output is set to after-adjustment time Tk2 ', Tc2', Tm2 'and Ty2'. It is a figure explaining the scanning start point position on each photoconductor drum surface after adjustment. It is the figure which showed an example of the structure of a detection sensor. It is the figure which showed an example of the pattern for position correction. FIG. 6 is a diagram illustrating a state in which a detection sensor installed at a first arrangement position detects a position of a position correction pattern on a paper transport belt. FIG. 6 is a timing chart for explaining the SOS signal reception timing of each color laser beam and the image signal output end timing Tk3, Tc3, Tm3, Ty3 before adjusting the scanning end point position. It is the figure which showed the timing chart of the state where the image clock was adjusted. FIG. 5 is a diagram illustrating a timing chart when a shift in output timing of SOS signals and a change in print width occur. FIG. 6 is a timing chart when an output start timing and an output end timing of an image signal are determined based on a corrected SOS signal. FIG. 5 is a timing chart showing the relationship between Vsync for setting the writing start timing in each image forming unit and each color image forming area. It is the figure which showed an example of the sensor which can detect the position of the laser beam of a two-dimensional direction. It is the figure which showed an example of the sensor which can detect the position of the laser beam of a two-dimensional direction. Time shift amounts ΔTVy1, ΔTVm1, ΔTVc1 relating to the output timing of Vsync, calculated based on the time intervals P1, P2, P3 relating to the passage timing of each parallel pattern PC, PM, PY and the conveyance speed of the paper conveyance belt. , ΔTVk1. It is a figure explaining adjusted Vsync.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 10Y, 10M, 10C, 10K ... Image forming unit, 11 ... Photosensitive drum, 20 ... Laser exposure device, 30 ... Paper conveyance belt, 32 ... Drive roll, 60 ... Detection sensor, 80 ... Control part 291 ... SOS sensor 803 ... Calculation unit 804 ... Storage unit

Claims (11)

An image carrier,
Exposure means for performing scanning exposure on the image carrier with a light beam emitted from a light source;
Driving means for driving the light source based on image data;
Storage means for storing adjustment data for adjusting the output timing of the image data from the driving means for the light source;
The position of a predetermined pattern image formed on the image carrier by the exposure means scanning and exposing the light flux is determined on the image carrier or on the transfer body on which the pattern image is transferred from the image carrier. Detecting means for detecting the position,
The storage means stores the adjustment data obtained based on a position in the main scanning direction with respect to the pattern image formed in a region on the image holding body on the scanning start point side from the scanning center portion of the light beam. ,
The detection means detects the position of the pattern image formed in a region on the scanning end point side from the scanning center portion of the light flux of the image carrier,
Said drive means, an output start timing of the image data in the one scan line with respect to the light source is set based on a more stored the adjusted data in the storage unit, the output of the image data in the one scan line and set based on the end timing on the information about the position of the more said detected pattern image on the detection means, the image forming apparatus characterized by driving the light source. The detection means is movably provided at each of a first arrangement position corresponding to the scanning end point side from the scanning center portion of the light beam and a second arrangement position corresponding to the scanning start point side from the scanning center portion of the light beam. And
The storage means stores the adjustment data obtained based on the position of the pattern image detected by the detection means at the second arrangement position at a predetermined time;
The drive means sets the output timing of the image data within one scanning line based on information on the position of the pattern image detected by the detection means at the first arrangement position, and sets the light source The image forming apparatus according to claim 1, wherein the image forming apparatus is driven. A scanning start timing detecting means for detecting a scanning start timing of the light beam emitted from the light source to the image carrier;
The drive means sets the output start timing based on information related to the scan start timing detected by the scan start timing detection means and the adjustment data, and drives the light source. The image forming apparatus according to 1. A scanning start timing detecting means for detecting a scanning start timing of the light beam emitted from the light source to the image carrier;
The storage means further stores information on the scan start timing detected by the scan start timing detection means at a predetermined time,
2. The image according to claim 1, wherein the driving unit sets the output start timing based on the information related to the scanning start timing stored in the storage unit and the adjustment data, and drives the light source. Forming equipment. The storage means includes the adjustment data obtained based on the position of the pattern image detected by the detection means at the second arrangement position under a predetermined temperature environment , and the adjustment data under the predetermined temperature environment. 5. The image forming apparatus according to claim 4, wherein information relating to the scan start timing detected by the scan start timing detecting means is stored. A plurality of the image carriers are arranged,
The exposing means scans and exposes each of the plurality of image carriers with light beams emitted from the plurality of light sources provided corresponding to the plurality of image carriers,
The image forming apparatus according to claim 1, wherein the storage unit stores the adjustment data for adjusting an output timing of the image data for each of the plurality of light sources from the driving unit. A plurality of the image carriers are arranged,
The exposing means scans and exposes each of the plurality of image carriers with light beams emitted from the plurality of light sources provided corresponding to the plurality of image carriers,
The storage means further stores position information in the sub-scanning direction obtained based on positions in the sub-scanning direction with respect to the pattern image in the plurality of image carriers,
2. The driving unit drives the light source by adjusting a time difference set between the light beams emitted from the plurality of light sources based on position information in the sub-scanning direction. The image forming apparatus described. The image forming apparatus according to claim 2 , further comprising a holding unit that holds the detection unit at the first arrangement position and / or the second arrangement position . Storage means for storing adjustment data for adjusting the output timing of the image data from the driving means for driving the light source based on the image data to the light source;
The position of the predetermined pattern image formed on the image carrier by scanning exposure with the light beam from the light source or the position on the image carrier and the pattern image transferred from the image carrier. Position information acquisition means for acquiring information about the position;
The output start timing of the image data within one scanning line from the driving unit to the light source is instructed based on the adjustment data stored in the storage unit, and the output of the image data within one scanning line is ended. Instruction means for instructing the timing based on information on the position of the pattern image acquired by the position information acquisition means ;
The storage means stores the adjustment data obtained based on a position in the main scanning direction with respect to the pattern image formed in a region on the image holding body on the scanning start point side from the scanning center portion of the light beam. ,
The control device characterized in that the position information acquisition means acquires information on the position of the pattern image formed in a region on the scanning end point side from the scanning center of the light beam of the image carrier. . The storage means stores the adjustment data for adjusting the output timing of the image data for each of the plurality of light sources that emit the light flux to each of the plurality of image carriers. 9. The control device according to 9 . A scanning start timing acquisition means for acquiring information related to the scanning start timing of the luminous flux emitted from the light source to the image carrier;
The storage means further stores information related to the scan start timing acquired by the scan start timing acquisition means at a predetermined time,
The control device according to claim 9 , wherein the instruction unit instructs the output start timing based on the information related to the scan start timing stored in the storage unit and the adjustment data.

Images