JP6810507B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus.

Conventionally, electrophotographic image forming devices have been known as printers, copiers, and the like. When forming an image on paper, this image forming apparatus executes a series of processes of transferring the image to the paper and fixing the image on the paper.

For example, Patent Document 1 discloses an image forming apparatus that forms an image on paper by a process of transferring an image and fixing an image. This image forming apparatus includes a transport direction correction device that corrects the bending in the transport direction of the paper on which the image is transferred so as to be returned by the fixing device. According to this image forming apparatus, it is possible to prevent the occurrence of image distortion by returning the bending of the paper with the fixing apparatus.

Further, there is also known a method of periodically swinging the fixing device to shift the passing position of the paper edge. For example, Patent Document 2 describes a fixing member shifting means for moving a fixing member in a direction orthogonal to the sheet transporting direction, and a direction in which the sheet fed to the toner image transfer unit is orthogonal to the sheet transporting direction. An image forming apparatus including a sheet shifting means for moving is disclosed. According to this image forming apparatus, it is possible to reduce scratches on the fixing member by effectively shifting the traveling positions of the fixing member and the sheet, and to print a high-quality image on the sheet.

Japanese Unexamined Patent Publication No. 2007-193087 Japanese Unexamined Patent Publication No. 2012-78679

Generally, in the image forming apparatus, various elements are designed so that the center position of the paper transported along the transport path (paper transport center) coincides with the center position (center of the transport path) in the transport path. This is also the case with the fixing device that performs the fixing process. Therefore, the ideal paper transport position (fixed ideal center) in the fixing device coincides with the paper transport center.

However, in an actual fixing device, the fixing ideal center may exist at a position deviated from the center of the transport path. In this case, in the process of passing through the fixing device, a phenomenon occurs in which the paper is displaced, that is, the paper transport center moves toward the fixing ideal center. This is because the pressure distribution of the fixing nip is formed based on the ideal center of fixing, so that the pressure distribution is not evenly formed on the paper passing through the center of the transport path with the center position of the paper as the boundary, and the pressure distribution is not evenly formed on the left and right sides of the paper. This is because an unbalanced force acts.

If the paper is misaligned when the paper remains in the transfer nip, the image on the paper will be bent. Further, when the paper is bent between the fixing nip and the transfer nip to form a loop, the formation of the loop cannot be appropriately controlled, which may lead to contact between the guide plate and the paper. There is. Since the image before fixing is supported on the paper, the contact may cause damage to the image.

Further, since the deviation of the ideal fixing center is unique to the apparatus, it is difficult to adjust the deviation by a uniform adjustment common to all image forming apparatus.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an image forming apparatus capable of suppressing the displacement of paper due to the characteristics peculiar to the fixing device and suppressing the deterioration of image quality. Is.

In order to solve such a problem, the present invention acquires a fixing device for fixing an image on paper and a paper type of the paper in an image forming apparatus including an image forming unit for forming an image and transferring the image to paper. deviation of the sheet type acquisition unit, and the paper type of the paper, and fixing the ideal center sheet transport center toward a central position in the sheet width direction of the paper when the paper passes through the fixing device and the sheet conveyance center of By searching the storage unit that stores the table that defines the correspondence with the amount and the table stored in the storage unit, the deviation amount corresponding to the paper type of the paper acquired by the paper type acquisition unit can be obtained. a shift amount obtaining unit that acquires, before the sheet enters the fixing device, the fixing device, the shift amount of the frequency to the sheet width direction, has a position control section for controlling to move the ing.
Further, another image forming apparatus of the present invention is an image forming apparatus comprising a forming the image image forming unit that transfers the image onto a sheet, a pair of resist rollers for conveying the sheet to a transfer position by the image forming section when a fixing device having a fixing roller for fixing an image on a sheet, the paper type acquisition unit that acquires paper type of paper, and paper type of the paper sheet in the sheet width when the paper passes through the fixing device Searching for a storage unit that stores a table that defines the correspondence between the ideal fixing center toward which the paper transport center, which is the center position in the direction, and the amount of deviation from the paper transport center, and the table stored in the storage unit. Accordingly, a shift amount obtaining unit that obtains the displacement amount corresponding to the paper type of the paper obtained by the paper type acquisition unit, while the sheet is sandwiched between the pair of resist rollers, the pair of registration rollers , said paper width min the deviation amount in the direction controls to move, and the formation position of the image by the prior SL image forming unit has a position control section for controlling to correct.
Further, another image forming apparatus of the present invention is an image forming apparatus including an image forming unit that forms an image and transfers the image to paper, and the paper fed into the conveying path is parallel to the paper conveying direction. For a fixing device having a pair of side edge regulating plates for regulating the position of the paper side edge, a fixing roller for fixing an image on the paper, a paper type acquisition unit for acquiring the paper type, and a paper type . A storage unit that stores a table that defines the correspondence between the ideal fixing center toward which the paper transport center, which is the center position in the paper width direction of the paper, and the amount of deviation from the paper transport center when the paper passes through the fixing device. By searching the table stored in the storage unit, the deviation amount acquisition unit for acquiring the deviation amount of the paper corresponding to the paper type of the paper acquired by the paper type acquisition unit, and the paper feeding unit. prior to, the pair of side edge regulating plate, the sheet width direction to the minute of the shift amount, and controls to move, performs control to correct the formation position of the image by the prior SL image forming unit It has a position control unit.

Here, in the present invention, the image forming apparatus further has a storage unit for storing information defining the correspondence between the paper type and the ideal fixing position, and the position acquisition unit is acquired by the paper type acquisition unit. It is preferable to acquire the fixing ideal position by searching the storage unit based on the paper type.

Further, in the present invention, it is preferable that the paper type includes at least one of the size of the paper, the thickness of the paper, and the surface property of the paper.

Further, in the present invention, the fixing ideal center stored in the storage unit detects the position of the paper side edge parallel to the paper transport direction for the paper passing through the fixing device, and is based on the amount of deviation of the side edge position. It is preferable that it is determined by.

Further, in the present invention, the fixing ideal center stored in the storage unit is preferably determined by reading an image on paper that has passed through the fixing device and based on the amount of bending of the read image.

Here, it is preferable that the reading of the image is started from a position advanced by a predetermined distance from the tip of the paper, and the predetermined distance is the distance from the transfer position by the image forming unit to the fixing device.

According to the present invention, by acquiring the fixing ideal position peculiar to the fixing device according to the paper type, this can be matched with the paper conveying position. As a result, it is possible to suppress the occurrence of paper misalignment. As a result, it is possible to suppress the occurrence of situations such as bending of the image and damage to the image due to contact with the guide plate, so that deterioration of image quality can be suppressed.

A block diagram schematically showing the image forming apparatus according to the first embodiment. The block diagram which shows the structure of the control system of the image forming apparatus which concerns on 1st Embodiment Explanatory drawing showing the details of the position control executed by the control unit A flowchart showing a control operation of the image forming apparatus according to the first embodiment. Explanatory drawing showing the table of the fixing ideal center Explanatory drawing showing the outline of position control The block diagram which shows the structure of the control system of the image forming apparatus which concerns on 2nd Embodiment Explanatory drawing which shows the concept of swing control in the image forming apparatus which concerns on 2nd Embodiment Explanatory drawing which shows the outline of swing control and fixing control

(First Embodiment)
FIG. 1 is a configuration diagram schematically showing an image forming apparatus 1 according to the present embodiment. The image forming apparatus 1 is an electrophotographic type image forming apparatus such as a copier, and is a so-called tandem type color image forming apparatus that forms a full-color image.

The image forming apparatus 1 is mainly composed of a document reading apparatus SC, an image forming unit 10Y, 10M, 10C, 10K, a fixing device 40, and a control unit 50.

The document reading device SC illuminates an image of a document with an illuminating device, reads the reflected light with a line image sensor, and obtains an image signal. This image signal is input to the control unit 50 as image data after being subjected to processing such as A / D conversion, shading correction, and compression. The image data input to the control unit 50 is not limited to the data read by the document reading device SC, and is, for example, the data received from a personal computer connected to the image forming device 1 or another image forming device 1. , USB memory and the like may be stored in a portable recording medium.

The image forming units 10Y, 10M, 10C, and 10K are an image forming unit 10Y that forms a yellow (Y) image, an image forming unit 10M that forms an image of Magenda (M), and an image that forms an image of cyan (C). The forming unit 10C corresponds to the image forming unit 10K that forms an image of black (K).

The image forming unit 10Y is composed of a photoconductor drum 11Y, a charging unit arranged around the photoconductor drum 11Y, an optical writing unit 12Y, a developing device, and a drum cleaner.

The surface of the photoconductor drum 11Y is uniformly charged by the charged portion, and a latent image is formed on the photoconductor drum 11Y by scanning exposure by the optical writing unit 12Y. Further, the developing apparatus visualizes the latent image on the photoconductor drum 11Y by developing with toner. As a result, an image (toner image) of a predetermined color corresponding to yellow is formed on the photoconductor drum 11Y. The image formed on the photoconductor drum 11Y is sequentially transferred to a predetermined position on the intermediate transfer belt 15 by the primary transfer roller.

The image forming units 10M, 10C, 10K are composed of the photoconductor drums 11M, 11C, 11K, a charging unit arranged around them, an optical writing unit 12M, 12C, 12K, a developing device, and a drum cleaner. The details of these elements are the same as those of the image forming unit 10Y.

The intermediate transfer belt 15 is an endless belt, and is hung on a plurality of rollers including a secondary transfer opposed roller and a belt driven roller. The image composed of each color transferred on the intermediate transfer belt 15 is transferred by the secondary transfer roller 16 to the paper P transported at a predetermined timing by the paper transport unit 20. The secondary transfer roller 16 is a roller-shaped rotating member, and is pressed against the secondary transfer opposed roller via the intermediate transfer belt 15 (transfer nip).

The paper transport unit 20 transports the paper P fed from the paper feed units 22 and 24 according to the transport path.

The paper P is stored in the paper tray 21, and the paper P stored in the paper tray 21 is taken in by the paper feeding unit 22 and sent out to the transport path. The paper tray 21 is provided with a pair of side edge restricting plates 21a that regulate the position of the paper side edge parallel to the paper transport direction for the paper P to be fed into the transport path. With the pair of side edge regulation plates 21a, the position of the paper P to be conveyed along the transfer path, that is, the transfer position of the paper P can be set. Normally, the transport position of the paper P is set to coincide with the reference position on the transport path for transporting the paper, and the positions of the pair of side edge restricting plates 21a are also set to match the transport position of the paper P. It is set.

In this specification, the transport position of the paper P is defined with reference to the center position of the paper P transported along the transport path in the paper width direction, and is hereinafter referred to as "paper transport center". Further, the reference position on the transport path is defined by the center position in the paper width direction in the transport path, and is hereinafter referred to as "the center of the transport path".

Further, at the side end of the main body housing of the image forming apparatus 1, a paper feed tray 23 for introducing paper P such as manual feed paper and long paper into the machine is arranged. The paper P placed on the paper feed tray 23 is taken in by the paper feed unit 24 and sent out to the transport path. The paper feed tray 23 is provided with a pair of side edge restricting plates 23a that regulate the position of the paper side edge parallel to the paper transport direction for the paper P to be fed into the transport path. The positions of the pair of side edge restricting plates 23a are set along with the paper transport center.

The paper P that has been fed is conveyed in the machine by a plurality of transfer roller pairs such as a pair of loop rollers 27 and a pair of resist rollers 26, so that the transfer nip, that is, the image transfer position by the secondary transfer roller 16. Is supplied to. Specifically, when the fed paper P is conveyed by the pair of loop rollers 27 and the transfer roller pair on the upstream side of the loop rollers 27, the tip of the paper P abuts against the pair of resist rollers 26 in the rotation stopped state. .. In this state, the pair of loop rollers 27 continue to rotate, so that a loop is formed on the paper P. By this operation, the bending of the paper P is corrected. After that, the pair of resist rollers 26 start rotating at a predetermined timing to feed the paper P to the transfer position.

The fixing device 40 is a device that performs a fixing process for fixing an image on the paper P on which the image is transferred. The fixing device 40 includes a pair of fixing rollers 41 that form a nip (fixing nip) by being placed in pressure contact with each other, and a heating means for heating the fixing roller 41. As the heating means, a heater such as a halogen lamp can be used. The fixing device 40 conveys the paper P, and fixes the image on the paper P by performing pressure fixing by a pair of fixing rollers 41 and heat fixing by a heater.

The paper P that has been fixed by the fixing device 40 is discharged by the paper ejection roller 28 to a paper ejection tray (not shown) attached to the side surface of the housing. Further, when the image is formed on the back surface of the paper P, the paper P that has finished forming the image on the front surface of the paper is conveyed to the reversing roller below by the switching gate 29. The reversing roller sandwiches the rear end of the conveyed paper P and then reverse-feeds the paper P to invert the paper P and feed it to the re-feeding and conveying path. The paper P fed to the re-feeding transfer path is conveyed by a plurality of transfer roller pairs and returns to the transfer position.

The operation panel 45 is a touch panel type input unit capable of inputting information according to the information displayed on the display. The user can set information about the paper P (paper type, etc.), image density, magnification, and the like through the operation on the operation panel 45, and the information is acquired by the control unit 50. In addition, the operation panel 45 also functions as a display unit that displays various information to the user via the operation panel 45 by being controlled by the control unit 50.

The control unit 50 has a function of integrally controlling the image forming apparatus 1. As the control unit 50, a microcomputer mainly composed of a CPU, a ROM, a RAM, and an I / O interface can be used. The control unit 50 forms an image by controlling the image forming units 10Y, 10M, 10C, 10K, etc. and transfers the image to the paper P, or controls the fixing device 40 to transfer the image to the paper P. The paper P is fed and transported by fixing the paper and controlling the paper transport unit 20 and the like.

FIG. 2 is a block diagram showing a configuration of a control system of the image forming apparatus 1 according to the present embodiment. Further, FIG. 3 is an explanatory diagram showing details of position control executed by the control unit 50. Here, "Cst" shown in FIG. 3 indicates the center of the transport path. In relation to the present embodiment, the control unit 50 has the following functions.

First, the control unit 50 acquires a paper type related to the paper P when forming an image (paper type acquisition unit 50a). For example, the control unit 50 can acquire the paper type from the job information set by the user through the operation panel 45 or the like. Here, the paper type is configured to include information on the size of the paper P, the thickness of the paper P, and the surface property of the paper P.

Since the thickness of the paper P correlates with the basis weight of the paper P, the thickness is treated using the basis weight in this specification. Further, the surface property of the paper P indicates the degree of surface roughness thereof, and in the present embodiment, for convenience, two surface properties of coated paper and uncoated paper will be described as an example.

Second, the control unit 50 acquires the ideal fixing position based on the paper type (position acquisition unit 50b (deviation amount acquisition unit) ). In the present embodiment, the control unit 50 acquires the ideal fixing position from the storage unit 51 that stores information in which the ideal fixing position peculiar to the fixing device 40 is associated with each paper type.

Here, the ideal fixing position indicates the ideal conveying position of the paper P in the fixing device 40, and is determined as being unique to the device. In the present specification, the ideal fixing position is defined with reference to the center position of the paper P passing through the ideal fixing position, and is hereinafter referred to as "ideal fixing center".

Generally, in the image forming apparatus 1, various elements are designed so that the paper transport center coincides with the transport path center Cst. This is also the case with the fixing device 40. Therefore, originally, the ideal fixing center and the paper transport center coincide with each other. However, in the actual fixing device 40, the fixing ideal center may exist at a position deviated from the transport path center Cst. In this case, in the process of passing through the fixing device 40, a phenomenon occurs in which the paper P moves from the center Cst of the transport path toward the ideal center of fixing.

Such deviation of the fixing ideal center includes a manufacturing error of the crown shape (or inverted crown shape) given to each fixing roller 41, a pressure welding balance between both fixing rollers 41, and distortion (roller) at the time of assembling each fixing roller 41. Alignment) and other factors. That is, this deviation is due to a de facto error that does not occur at the design stage. Then, the deviation of the ideal fixing center appears for each fixing device in a state peculiar to the device. The deviation of the ideal center of fixing depends on the paper type such as the paper size in the paper width direction (direction intersecting the paper transport direction), the thickness of the paper P, and the surface property of the paper P, while being determined based on each device. Is also different.

A storage unit 51 is connected to the control unit 50. The storage unit 51 stores a table that defines the correspondence between the paper type and the ideal fixing center. This table is created at the time of product manufacturing or by executing the adjustment mode of the image forming apparatus 1 and specifying the fixing ideal center for each paper type.

The anchoring ideal center is determined by, for example, the following method.

The first method is a method using a detection means for detecting the position of the paper side edge such as a CCD line sensor. Specifically, the paper P is transported along the center of the transport path, and the position of the paper side edge is detected by the detecting means for the paper P passing through the fixing device 40. Then, the amount of deviation of the side edge position is monitored between the time when the front end of the paper reaches the fixing device 40 and the time when the rear end of the paper exits the fixing device 40. The ideal fixing center is determined based on this amount of deviation.

The second method is a method using an image reading device mounted on the image forming apparatus 1 or mounted on an apparatus arranged on the downstream side of the image forming apparatus 1. Specifically, the paper P is transported along the center of the transport path, a predetermined test image is transferred to the paper P by the image forming units 10Y, 10M, 10C, and 10K, and the image is fixed on the paper P by the fixing device 40. Further, with respect to the paper P that has passed through the fixing device 40, the image on the paper is read by the image reading device. Then, the fixing ideal center is determined based on the bending amount of the read image.

It should be noted that the transferred image is bent only after the tip of the paper P has entered the fixing device 40. Therefore, it is preferable to start reading the image by the image reading device from a position advanced by a predetermined distance from the tip of the paper P. Here, the predetermined distance corresponds to the distance from the transfer position to the fixing nip.

Thirdly, the control unit 50 performs position control for matching the paper transport center and the fixing ideal center (position control unit 50c). The position control is executed by at least one of a control of moving the pair of side edge restricting plates 21a and 23a, a control of moving the pair of resist rollers 26, and a control of moving the fixing device 40.

First, a control method for moving the fixing device 40 will be described. The fixing device 40 includes, for example, a fixing drive unit 57 composed of an electric motor, a power transmission mechanism such as a gear, and the like, and the fixing drive unit 57 is controlled by the control unit 50. By driving the fixing drive unit 57, the control unit 50 can move the fixing device 40 along the paper width direction. Therefore, by moving the fixing device 40 before the paper P reaches the fixing device 40, the paper transport center and the fixing ideal center can be aligned with each other.

Next, a control method for moving the pair of resist rollers 26 will be described. The pair of resist rollers 26 include, for example, a resist drive unit 56 composed of a power transmission mechanism such as an electric motor or a gear, and the resist drive unit 56 is controlled by the control unit 50. The control unit 50 can move the pair of resist rollers 26 along the paper width direction by driving the resist drive unit 56. Therefore, by moving the pair of resist rollers 26 while the paper P is being sandwiched by the pair of resist rollers 26, the paper transport center and the fixing ideal center can be aligned with each other.

Finally, a control method for moving the pair of side edge restricting plates 23a will be described. The pair of side end regulation plate 23a includes, for example, a side end regulation plate drive unit 55 composed of an electric motor or a power transmission mechanism such as a gear, and the side end regulation plate drive unit 55 is a control unit 50. Is controlled by. The control unit 50 can move the pair of side edge regulation plates 23a along the paper width direction by driving the side edge regulation plate drive unit 55. Therefore, by moving the pair of side edge restricting plates 23a prior to feeding the paper P, the paper transport center and the fixing ideal center can be aligned. This method can also be applied to the pair of side edge restricting plates 21a on the paper tray 21 side.

When moving the pair of side edge restricting plates 21a, 23a or the pair of resist rollers 26, the control unit 50 uses the image forming units 10Y, 10M, 10C, and 10K according to the moving direction and the amount of movement. The formation position of the above, that is, the writing position corrected by the optical writing units 12Y, 12M, 12C, 12K is further controlled. By this correction control, even when the position of the paper P entering the secondary transfer roller 16 moves in the paper width direction, the image position formed on the paper P and the paper P should be formed on the paper P. It is possible to match the image position.

FIG. 4 is a flowchart showing a control operation of the image forming apparatus 1 according to the present embodiment. The process shown in this flowchart is executed by the control unit 50 with the execution of the job as a trigger.

First, in step 1 (S1), the control unit 50 acquires the paper type of the paper P used for image formation by executing the job. The control unit 50 can acquire the paper type from the job information set by the user via the operation panel 45 or the like. By this step 1, the control unit 50 acquires information on the size (paper width) of the paper P in the paper width direction, the basis weight of the paper P, and whether or not the paper is coated paper.

In step 2 (S2), the control unit 50 determines whether or not the paper P is uncoated paper. If an affirmative decision is made in step 2, that is, if the paper P is uncoated paper, the process proceeds to step 3 (S3). On the other hand, if a negative determination is made in step 2, that is, if the paper P is coated paper, the process proceeds to step 4 (S4).

In step 3, the control unit 50 calculates the shift amount of the paper P based on the table prepared for the uncoated paper. Here, FIG. 5A is an explanatory view showing a table having an ideal fixing center corresponding to uncoated paper. In this table, the ideal fixing center for uncoated paper is defined as the amount of deviation from the original center of paper transport (center of transport path Cst), and the amount of deviation is associated with each paper width and basis weight. .. When the amount of deviation is shown as a minus, the ideal fixing center is shifted to the back side of the device, that is, to the right side when the paper P transport path is viewed from upstream to downstream. On the other hand, when the amount of deviation is shown as positive, the ideal fixing center is displaced toward the front side of the device. The table is stored in the storage unit 51, and the control unit 50 searches the table based on the paper width and the basis weight, and calculates the ideal fixing center (the amount of deviation from the original paper transport center).

In step 4, the control unit 50 calculates the shift amount of the paper P based on the table prepared for the coated paper. Here, FIG. 5B is an explanatory view showing a table having an ideal fixing center corresponding to coated paper. In this table, the ideal fixing center for coated paper is defined as the amount of deviation from the original paper transport center (transport path center Cst), and the deviation amount is associated with each paper width and basis weight. When the amount of deviation is shown as a minus, the ideal fixing center is shifted to the back side of the device. On the other hand, when the amount of deviation is shown as positive, the ideal fixing center is displaced toward the front side of the device. The table is stored in the storage unit 51, and the control unit 50 searches the table based on the paper width and the basis weight, and calculates the ideal fixing center (the amount of deviation from the original paper transport center).

In step 5 (S5), the control unit 50 performs position control based on the fixing ideal center acquired in step 3 or step 4. Here, FIG. 6 is an explanatory diagram showing an outline of position control.

As shown in FIG. 3A, the position control can be performed by, for example, moving the fixing device 40. The control unit 50 moves the fixing device 40 based on the acquired ideal fixing center Cf. For example, when the fixing ideal center Cf is shifted to the back side (upper side in the figure) of the device from the transport path center Cst, the control unit 50 is placed on the front side of the device (upper side in the drawing) by the amount of the deviation of the fixing ideal center Cf. The fixing device 40 is moved to the lower side in the figure). As a result, when the paper feeding of the paper P is started and the paper P enters the fixing device 40, the paper transport center and the fixing ideal center Cf coincide with each other.

Further, as shown in FIG. 3B, the position control can also be performed by, for example, moving the pair of side end restricting plates 23a. The control unit 50 moves the pair of side end regulation plates 23a based on the acquired ideal center Cf for fixing. For example, when the fixing ideal center Cf is shifted to the back side of the device (upper side in the figure) from the transport path center Cst, the control unit 50 is placed on the back side of the device (upper side in the drawing) by the amount of the deviation of the fixing ideal center Cf. The pair of side edge regulation plates 23a are moved to the upper side in the figure). Due to the movement of the pair of side edge restricting plates 23a, the paper feeding position of the paper P shifts in the paper width direction. Therefore, when the paper P is started to be fed and the paper P enters the fixing device 40. The paper transport center and the fixing ideal center Cf coincide with each other. This method can also be applied to the pair of side edge restricting plates 21a on the paper tray 21 side.

When moving the pair of side edge restricting plates 21a, 23a, the control unit 50 uses the image forming units 10Y, 10M, 10C, depending on the amount and direction of the displacement of the paper P by the pair of side edge restricting plates 23a. Further control is performed to correct the image formation position by 10K, that is, the image writing position by the optical writing units 12Y, 12M, 12C, 12K. In the above example, the control unit 50 moves the image writing position to the back side (upper side in the drawing) of the device by the amount of deviation of the fixing ideal center Cf. By this correction control, even when the position of the paper P entering the secondary transfer roller 16 moves in the paper width direction, the image position formed on the paper P and the paper P should be formed on the paper P. It is possible to match the image position.

In step 6 (S6), the control unit 50 starts feeding the paper P.

As described above, the position control can also be performed by moving the pair of resist rollers 26. In this case, the execution order of steps 5 and 6 is reversed, and as shown in FIG. 6C, the pair of resist rollers 26 are moved while the paper P is sandwiched by the pair of resist rollers 26. Let me. For example, when the fixing ideal center Cf is shifted to the back side of the device (upper side in the figure) from the transport path center Cst, the control unit 50 is moved to the back side of the device (upper side in the drawing) by the amount of the deviation of the fixing ideal center Cf. The pair of resist rollers 26 are moved to the upper side in the figure). Since the transport position of the paper P is shifted in the paper width direction by the pair of resist rollers 26, the paper P is started to be fed, passes through the pair of resist rollers 26, and is transferred to the fixing device 40. When P enters, the paper transport center and the fixing ideal center Cf coincide with each other. Further, in this method, it is necessary to further perform control for correcting the image formation position by the image forming units 10Y, 10M, 10C, and 10K.

As described above, in the present embodiment, the image forming apparatus 1 includes the image forming portions 10Y, 10M, 10C, 10K for forming an image and transferring the image to the paper P, and the fixing device 40 for fixing the image on the paper P. , And a control unit 50. Here, the control unit 50 has a function of acquiring the paper type for the paper P (paper type acquisition unit 50a) and a function of acquiring the fixing ideal center Cf according to the paper type (position acquisition unit 50b). It has a function (position control unit 50c) for performing position control for matching the paper transport center and the fixing ideal center Cf.

According to this configuration, by acquiring the fixing ideal center Cf peculiar to the fixing device 40 according to the paper type, it can be matched with the paper conveying center. As a result, it is possible to suppress the displacement of the paper due to the characteristics peculiar to the fixing device. As a result, it is possible to suppress the occurrence of situations such as bending of the image and damage to the image due to contact with the guide plate, so that deterioration of image quality can be suppressed.

In particular, for paper P having a long size in the paper transport direction such as roll paper and long paper, the deviation of the paper P tends to accumulate according to the transport distance. Therefore, in the image forming apparatus 1 using such a paper P, it is effective to perform the position control according to the present embodiment.

Further, in the present embodiment, the image forming apparatus 1 further has a storage unit 51 for storing information defining the correspondence between the paper type and the fixing ideal center Cf. The control unit 50 acquires the fixing ideal center Cf by searching the storage unit 51 based on the acquired paper type.

According to this configuration, since the storage unit 51 holds the necessary information, it is possible to appropriately acquire the fixing ideal center Cf along with the paper type. However, the information of the fixing ideal center Cf does not have to be possessed by the image forming apparatus 1 itself, and the information may be acquired by the user inputting or communicating with an external device as necessary. ..

Further, in the present embodiment, the paper type includes at least one of the size of the paper P, the thickness of the paper P, and the surface property of the paper P.

The deviation of the paper P according to the deviation of the fixing ideal center Cf is due to the deviation of the pressure distribution acting on the paper P. Further, even if the pressure distribution is the same, the degree of deviation of the paper P differs depending on the paper type, so that the fixing ideal center Cf differs depending on the paper type. For example, if the paper width of the paper P is small, the deviation of the paper P tends to be large. Further, the smaller the thickness of the paper P or the smoother the surface of the paper P, the larger the deviation of the paper P tends to be. In this way, the ideal fixing center Cf can be accurately obtained by appropriately considering the paper type, that is, the parameter acting on the displacement of the paper P.

Further, in the present embodiment, the position control is a control for moving the fixing device 40 in the paper width direction based on the fixing ideal center Cf before the paper P enters the fixing device 40.

According to this configuration, the paper transport center of the paper P entering the fixing device 40 and the fixing ideal center Cf can be made to coincide with each other.

Further, in the present embodiment, the position control is a control for moving the resist roller 26 in the paper width direction based on the fixing ideal center Cf while the paper P is sandwiched by the pair of resist rollers 26.

According to this configuration, the paper transport center of the paper P entering the fixing device 40 and the fixing ideal center Cf can be made to coincide with each other.

Further, in the present embodiment, the position control is a control for moving the pair of side edge restricting plates 21a and 23a in the paper width direction based on the fixing ideal center Cf prior to feeding the paper P.

According to this configuration, the paper feed center of the paper P entering the fixing device 40 and the fixing ideal center Cf can be matched with each other.

Further, the position control further includes a control for correcting the image formation position by the image forming units 10Y, 10M, 10C, and 10K.

According to this configuration, the formation position of the image can be corrected according to the movement of the paper P. As a result, the image can be formed at an appropriate position on the paper P.

Further, in the present embodiment, the fixing ideal center Cf detects the position of the paper side edge parallel to the paper transport direction for the paper P passing through the fixing device 40, and is based on the amount of deviation of the side end position. I have decided.

According to this configuration, the fixing ideal center Cf can be appropriately determined from the actual behavior of the paper P.

Further, in the present embodiment, the fixing ideal center Cf is determined based on the amount of bending of the scanned image by reading the image on the paper P that has passed through the fixing device 40.

According to this configuration, the fixing ideal center Cf can be appropriately determined from the locus of the image formed on the paper P.

Further, in the present embodiment, reading of the image is started from a position advanced by a predetermined distance from the tip of the paper P. Here, the predetermined distance is the distance from the transfer position (transfer nip) by the image forming units 10Y, 10M, 10C, 10K to the fixing device 40 (fixing nip).

According to this configuration, the image can be read only in the area where the deviation of the paper P is reflected. Thereby, the fixing ideal center Cf can be determined efficiently and appropriately.

(Second Embodiment)
FIG. 7 is a block diagram showing a configuration of a control system of the image forming apparatus 1 according to the second embodiment. Hereinafter, the image forming apparatus 1 according to the second embodiment will be described. The image forming apparatus 1 according to the second embodiment is different from that of the first embodiment in that the control unit 50 controls the swinging of the fixing device 40 from the viewpoint of protecting each fixing roller 41. It has a function (swing control unit 50d). This swing control is a control for swinging the fixing device 40 between papers in the paper width direction. That is, in the swing control, when the preceding paper P passes, the fixing device 40 is moved in the paper width direction before the succeeding paper P arrives, so that the succeeding paper P is at a position different from that of the preceding paper P. Is passed, and the passing position of the paper edge is shifted for each paper.

FIG. 8 is an explanatory diagram showing the concept of swing control in the image forming apparatus 1 according to the second embodiment. Normally, when swing control is performed, the center position of the fixing device is moved to the back side of the device or the front side of the device, starting from the center of paper transport. On the other hand, in the present embodiment, in consideration of the fixing ideal center Cf, the fixing ideal center Cf of the fixing device 40 is moved to the back side of the device or the front side of the device from the paper transport center as a starting point.

Further, in a situation where the ideal fixing center Cf is moving from the center of paper transport due to the swing control, the paper P transported along the center of paper transport becomes the ideal center Cf of fixing when passing through the fixing device 40. It may move toward you.

FIG. 9 is an explanatory diagram showing an outline of swing control and fixing control. Therefore, in the present embodiment, the control unit 50 enters the approaching position of the preceding sheet P and the approaching of the following sheet P after the preceding sheet P has passed and before the succeeding sheet P has entered the fixing device 40. The fixing device 40 is moved so as to be different from the position (swing control). Then, after the fixing device 40 swings, the control unit 50 receives the transfer path center Cst (when the leading end of the subsequent paper P enters the fixing device 40, until the rear end of the paper P passes through the transfer nip. The fixing device 40 is moved so that the ideal fixing center Cf coincides with the paper transport center) (position control).

According to this configuration, when the transfer path center Cst and the fixing ideal center Cf are deviated from each other, the paper P moves to the fixing ideal center Cf, but the fixing device 40 is moved to the transfer path center Cst (paper transfer center). By moving to), both movements will cancel each other out. Therefore, the paper transport center is maintained at the transport path center Cst, and the deviation of the paper P can be suppressed. As a result, both position control and swing control can be achieved at the same time. As a result, it is possible to appropriately protect the fixing device 40 while suppressing the displacement of the paper P.

Although the image forming apparatus according to the embodiment of the present invention has been described above, it goes without saying that the present invention is not limited to the above-described embodiment and various modifications can be made within the scope of the invention. ..

For example, when moving the fixing device, it is not necessary to move the entire device, and only a pair of fixing rollers may be moved. Further, if the paper is moved upstream of the fixing device, the position may be controlled not only by the resist roller but also by another transport roller or a dedicated moving mechanism.

Further, as a specific example of the position control, a method of automatically moving the fixing device or the paper has been shown, but the position control may simply display the information of the fixing ideal position to the user. In this case, by referring to the information and moving the fixing device or the pair of side edge restricting plates by the user himself / herself, the paper conveying position and the fixing ideal position can be matched.

1 Image forming device 10Y to 10K Image forming part 11Y to 11K Photoreceptor drum 12Y to 12K Optical writing part 15 Intermediate transfer belt 16 Secondary transfer roller 20 Paper transfer part 21 Paper tray 21a Side end regulation plate 22 Feeding part 23 Supply Paper tray 23a Side edge regulation plate 24 Feeding unit 26 Resist roller 40 Fixing device 50 Control unit 50a Paper type acquisition unit 50b Position acquisition unit 50c Position control unit 50d Swing control unit 51 Storage unit

Claims (7)

In an image forming apparatus including an image forming section which forms an image and transfers the image to paper.
A fixing device that fixes the image on paper,
And paper type acquisition unit for acquiring the paper type of the paper,
Provisions and paper type of the paper, the paper is the relationship between the shift amount between the fixing ideal central to the sheet transport center sheet conveyance center is the center position of the paper width direction of the paper is directed as it passes through the fixing device A storage unit that stores the table to be used
By searching the table stored in the storage unit, a deviation amount acquisition unit that acquires the deviation amount corresponding to the paper type of the paper acquired by the paper type acquisition unit, and a deviation amount acquisition unit.
Before the sheet enters the fixing device, the fixing device, the shift amount of the frequency to the sheet width direction, and a position control section for controlling to move,
An image forming apparatus characterized by having. In an image forming apparatus including an image forming section which forms an image and transfers the image to paper.
A pair of resist rollers for conveying the sheet to a transfer position by the image forming section,
A fixing device having a fixing roller for fixing an image on paper,
And paper type acquisition unit for acquiring the paper type of the paper,
Provisions and paper type of the paper, the paper is the relationship between the shift amount between the fixing ideal central to the sheet transport center sheet conveyance center is the center position of the paper width direction of the paper is directed as it passes through the fixing device A storage unit that stores the table to be used
By searching the table stored in the storage unit, a deviation amount acquisition unit that acquires the deviation amount corresponding to the paper type of the paper acquired by the paper type acquisition unit, and a deviation amount acquisition unit.
While the sheet by the pair of registration rollers is sandwiched, wherein the pair of registration rollers, the sheet width direction to the minute of the shift amount, and controls to move, formation of an image by pre Symbol image forming unit A position control unit that controls to correct the position,
An image forming apparatus characterized by having. In an image forming apparatus including an image forming section which forms an image and transfers the image to paper.
For paper fed into the transport path, a pair of side edge control plates that regulate the position of the paper side edge parallel to the paper transport direction,
A fixing device having a fixing roller for fixing an image on paper,
And paper type acquisition unit for acquiring the paper type of the paper,
Provisions and paper type of the paper, the paper is the relationship between the shift amount between the fixing ideal central to the sheet transport center sheet conveyance center is the center position of the paper width direction of the paper is directed as it passes through the fixing device A storage unit that stores the table to be used
By searching the table stored in the storage unit, the deviation amount acquisition unit that acquires the deviation amount of the paper corresponding to the paper type of the paper acquired by the paper type acquisition unit, and the deviation amount acquisition unit.
Prior to the sheet of paper feed, said pair of side edge regulating plate, the sheet width direction to the minute of the shift amount, and controls to move, to correct the formation position of the image by the prior SL image forming unit The position control unit that controls
An image forming apparatus characterized by having. The image forming apparatus according to any one of claims 1 to 3 , wherein the paper type includes at least one of a paper size, a paper thickness, and a paper surface property. The fixing ideal center stored in the storage unit detects the position of the paper side edge parallel to the paper transport direction for the paper passing through the fixing device, and is based on the amount of deviation of the position of the paper side edge. The image forming apparatus according to any one of claims 1 to 3, wherein the image forming apparatus is determined. The fixing ideal central stored in the storage unit from claim 1, wherein the fixing device reads an image on a sheet having passed through the, and characterized in that which is determined based on the curve amount of the read image The image forming apparatus according to any one of 3 . Reading of the image is started from a position advanced by a predetermined distance from the tip of the paper.
The image forming apparatus according to claim 6 , wherein the predetermined distance is a distance from a transfer position by the image forming unit to the fixing apparatus.

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