JP2009300695A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device which shortens a warming up time and also suppresses abnormal excessive heat or unevenness in temperature which occurs in a fixing roller even when a plurality of sheets of paper having size smaller than the total width of the fixing device are printed, and an image forming apparatus. <P>SOLUTION: When the plurality of sheets of paper 1 having the size smaller than the total width of the fixing device are continuously printed, the following processes are carried out. First, proceeding direction for the first sheet of paper 1 to which a toner image is transferred is changed only by an angle θ by a timing roller 181. Then, the proceeding direction for the paper 1 is made to be in parallel with the former proceeding direction by a timing roller 183. Next, the paper 1 which had its paper passing path changed is transported to the fixing device 160 and is pressed and fixed by the fixing roller 161. After the first sheet of paper 1 passes an auxiliary roller 182, the angle θ of the timing roller 181 and the auxiliary roller 182 is changed. Next, the second sheet of paper 1 is transported to the fixing device 160 through a paper passing path which is different from that for the first sheet of paper 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fixing device and an image forming apparatus for fixing a transfer image onto a sheet. More specifically, the present invention relates to a fixing device capable of suppressing temperature unevenness in the axial direction of the fixing roller and an image forming apparatus using the same.

  Some image forming apparatuses apply toner to an electrostatic latent image formed on the surface of a photoreceptor and develop the image, transfer the developed toner image onto a sheet, and fix the toner image on the sheet. is there. When a transfer image is fixed on a sheet, a system in which the sheet and a toner image on the surface thereof are heated and pressed by a heated fixing roller is generally used.

  When printing on paper smaller than the entire width of the fixing roller, as shown in FIG. 1, a region through which the paper passes (paper passing region) and a region other than that (non-paper passing region) are generated on the fixing roller. In the paper passing area of the fixing roller, the heat of the fixing roller is transmitted to the paper, but in the non-paper passing area, the heat is not transferred to the paper. For this reason, there is a risk that the temperature of the non-sheet passing area of the fixing roller will rise excessively and cause abnormal overheating. In addition, the temperature difference between the paper passing area and the non-paper passing area may increase. This may cause image unevenness on the printed paper. This tendency is particularly noticeable when printing out continuously on small size paper.

  Patent Document 1 discloses a fixing device that uses two external heating rollers having different calorific value distributions in order to make the temperature distribution of the fixing roller uniform. Here, the external heating roller is a roller that heats the fixing roller from the outside. One of the two external heating rollers uses a heater that generates a large amount of heat at the center, and the other external heating roller uses a heater that generates a large amount of heat at both ends. By using these rollers properly according to the paper size, it is said that abnormal overheating in the non-sheet passing portion can be prevented.

JP-A-11-084934

  By the way, in recent years, energy saving has been attempted to cope with environmental problems. Along with this, measures are being taken to shorten the warm-up time in image forming apparatuses used in printers, copiers, facsimiles, or multifunction peripherals thereof. As a specific example, the heat capacity can be reduced by reducing the thickness of the fixing roller. This is because the waiting time for warming the fixing roller can be shortened.

  However, in such a thinned fixing roller, the temperature difference between the sheet passing area and the non-sheet passing area tends to increase. This is because the heat capacity of the thinned fixing roller is small. Another reason is that the thickness of the fixing roller is thin and long in the width direction, so that heat in the non-sheet passing area is not easily transmitted to the sheet passing area. On the other hand, in the fixing device of Patent Document 1, since it is assumed that the temperature distribution of the fixing roller is bilaterally symmetric, it is unavoidable to adopt a method of conveying the sheet to the center of the fixing roller. Further, since the image forming apparatus is configured on the premise that heat is mainly taken from the vicinity of the center in the fixing roller, the temperature distribution tends to be biased in the first place. Therefore, it takes time to uniformly bring the surface of the fixing roller to a desired temperature. This cannot reduce the warm-up time.

  The present invention has been made to solve the above-described problems of the prior art. In other words, the problem is to reduce the warm-up time and to suppress abnormal overheating and temperature unevenness that can occur on the fixing roller even when printing a plurality of sheets having a size smaller than the entire width of the fixing device. It is an object of the present invention to provide a fixing device and an image forming apparatus that can be used.

  The image forming apparatus of the present invention, which has been made for the purpose of solving this problem, includes an image forming unit that forms a toner image, a transfer unit that transfers the toner image formed by the image forming unit onto a transfer target, and the transfer unit. An image forming apparatus having a fixing unit that fixes a toner image on the transfer medium that has passed through the transfer unit onto the transfer object; a passing position changing unit that changes a passing position of the transfer object in the width direction of the fixing unit; When the image is continuously formed on the transfer body having a lateral width smaller than the entire width of the fixing unit, the passing position of the transfer body is changed by the passing position changing unit for each transfer object or a group thereof. And a passage position control unit. Such an image forming apparatus can change the pressure location on the fixing roller for each transfer target. For this reason, heat is not taken away only from the same portion of the fixing roller by the transfer target.

  In the above, the passage position changing unit includes a swing roller pair for changing the sheet passing direction of the transfer body to the width direction of the fixing unit, and the sheet passing direction of the transfer body in a direction parallel to the original traveling direction. The swing roller pair and the fixed roller pair may be disposed between the transfer unit and the fixing unit. This is because there is no change in that the pressure location on the fixing roller can be changed for each transfer target.

  In the above, the passing position changing unit may be a fixing unit moving unit that moves the fixing unit in the width direction. This is because the sheet passing path of the transfer target does not change, but the pressing location on the fixing roller can be changed for each transfer target.

  In the above, the passing position changing unit is upstream of the transfer unit on the sheet passing path, and the toner image forming position in the image forming unit is matched with the sheet passing path changed by the passing position changing unit. The image forming position control unit may be changed. This is because the sheet passing path is changed for each transfer target, and the pressing location on the fixing roller can be changed for each transfer target.

  In the above, the passage position changing unit has a plurality of paper feed cassettes that can be provided with transfer bodies of the same size, and the plurality of paper feed cassettes are stacked with the transfer bodies in the width direction of the fixing unit. The positions may be different, and the passing position control unit may change which paper feeding cassette is used for each transferred object or its group. This is because there is no change in that the pressure location on the fixing roller can be changed for each transfer target.

  In the above, the passage position changing unit includes a swing roller pair for changing the sheet passing direction of the transfer body to the width direction of the fixing unit, and the sheet passing direction of the transfer body in a direction parallel to the original traveling direction. It is good to have a fixed roller pair to return. This is because there is no change in that the pressure location on the fixing roller can be changed for each transfer target.

  In the above, it is preferable that the passage position changing unit is a stacking position changing unit that changes the stacking position of the transfer target in the sheet feeding cassette. This is because there is no change in that the sheet passing area for each transfer target can be changed and the pressure location on the fixing roller can be changed.

  According to the present invention, it is possible to shorten the warm-up time and to fix the abnormal overheating and temperature unevenness that can occur in the fixing roller even when printing a plurality of sheets having a size smaller than the entire width of the fixing device. An apparatus and an image forming apparatus are provided.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the accompanying drawings. In this embodiment, the present invention is embodied with respect to a fixing device that hardly causes temperature unevenness and an image forming apparatus using the same. The fixing device and the image forming apparatus of the present invention change the sheet passing area in the fixing device for each sheet when printing out a plurality of sheets on a sheet having a size smaller than the entire width of the fixing apparatus.

[First embodiment]
The mechanical configuration of the image forming apparatus 100 of this embodiment will be described with reference to FIGS. As shown in FIG. 2, the image forming apparatus 100 includes a paper feed cassette 101, image forming units 10Y, 10M, 10C, and 10K, an intermediate transfer belt 152, a secondary transfer roller 153, a fixing device 160, and a timing. A roller 181, an auxiliary roller 182, a timing roller 183, an auxiliary roller 184, a drive unit 190, and a control unit 191 are included.

  The image forming units 10Y, 10M, 10C, and 10K form images corresponding to respective colors of Y (yellow), M (magenta), C (cyan), and K (black), respectively. The image forming unit 10Y includes a photoreceptor 110Y, a charging device 120Y, an exposure device 130Y, a developing device 140Y, a primary transfer roller 151Y, and a cleaner 170Y. The same applies to other colors. Hereinafter, the color symbols (Y, M, C, K) are omitted unless particularly necessary.

  FIG. 3 is a schematic diagram schematically showing the sheet passing path in the image forming apparatus 100. In FIG. 3, the image forming unit 10 is shown for only one color. In FIG. 3, the image is drawn so as to be directly transferred from the photosensitive member 110 to the paper 1 by the secondary transfer roller 153, but the actual transfer is performed via the intermediate transfer belt 152 as is apparent from FIG. 2. Made.

  The photoconductor 110 has a cylindrical shape and is an image carrier on which an electrostatic latent image is written on the surface. The charging device 120 is for uniformly charging the surface of the photoconductor 110. The exposure device 130 is for applying light to the surface of the uniformly charged photoreceptor 110 to form an electrostatic latent image. The developing device 140 is for applying toner to the electrostatic latent image formed on the surface of the photoconductor 110.

  The fixing device 160 is a fixing unit for fixing the toner to the paper so that the toner does not peel from the paper. The paper feed cassette 101 is for storing the paper 1. In addition, the paper 1 is supplied to the transfer device 153 when printing. Here, the sheet 1 is a transfer target body onto which a toner image is transferred.

  Here, in the image forming apparatus 100, a state in which the passage path of the sheet after transfer is changed is shown in FIG. The timing roller 181 is a pair of swing rollers for adjusting the paper passing direction of the transferred paper 1. The auxiliary roller 182 is a pair of rollers for feeding the paper 1 in the paper passing direction changed by the timing roller 181 and stabilizing the paper passing direction.

  The timing roller 183 is a pair of fixed rollers that returns the paper passing direction of the paper 1 changed by the timing roller 181 to a direction parallel to the paper passing direction before the change. Further, it adjusts the sheet passing timing at the leading end position of the transferred sheet 1 and corrects the skew of the sheet. The auxiliary roller 184 is a pair of rollers for feeding the paper 1 in the paper passing direction changed by the timing roller 183 and stabilizing the paper passing direction. Note that the timing roller 181 and the timing roller 183 are passage position changing units that change the sheet passing path of the paper 1.

  The drive unit 190 is for changing the angles of the timing roller 181 and the auxiliary roller 182 as shown in FIG. The drive unit 190 includes a rack 193 and a pinion 192, and the rack 193 reciprocates in the direction of the arrow X1 by the rotation of the pinion 192. Further, the timing roller 181 and the auxiliary roller 182 are connected to the drive unit 190 at the movable end 181a and the movable end 182a, respectively. Therefore, the movable end 181a and the movable end 182a are moved by the drive unit 190. Thereby, the direction of the timing roller 181 and the auxiliary roller 182 is changed. The timing roller 181 whose angle has been changed in this way changes the path through which the paper 1 passes. The driving unit 190 may be a known mechanism other than the rack 193 and the pinion 192 as long as it swings the timing roller 181 and the auxiliary roller 182.

  On the other hand, the position of the fixed end 181b opposite to the movable end 181a of the timing roller 181 is fixed. The position of the fixed end 182b opposite to the movable end 182a of the auxiliary roller 182 is also fixed. Therefore, the timing roller 181 and the auxiliary roller 182 perform a swing motion. Even in this case, the timing roller 181 and the auxiliary roller 182 are maintained in parallel. In addition, the control unit 191 controls the entire image forming apparatus 100 in addition to changing the sheet passing path of the sheet 1 by controlling the driving unit 190.

  Here, the operation of the image forming apparatus 100 of this embodiment will be described with reference to the flowchart of FIG. This flow is executed when a print instruction is given by the user. First, the control unit 191 confirms the print setting of the image forming apparatus 100. This is for determining whether printing for setting a sheet passing area, which will be described later, or normal printing is performed. Therefore, the width of the paper to be printed is confirmed (S1). Subsequently, the number of prints is confirmed (S2).

  Next, it is determined whether the printing to be performed is a sheet passing area setting printing or a normal printing (S3). That is, when a sheet other than A3 is selected and the setting for printing on 20 or more sheets is made, the sheet passing area setting printing for changing the sheet passing area for each sheet is performed (S10). In cases other than the above, normal printing is performed (S4). It should be noted that the paper size and the number of printed sheets used as criteria for determination in S3 can be set differently.

  Hereinafter, the paper passing area setting printing (S10) will be described. First, the driving unit 190 is driven in order to change the orientation of the timing roller 181 and the auxiliary roller 182 in the sheet passing path changing unit. As a result, the timing roller 181 and the auxiliary roller 182 change their angles around the fixed end portions 181b and 182b as shown in FIG.

  On the other hand, in the image forming unit, the toner image developed on the surface of the photoreceptor 110 is transferred onto the paper 1 by the transfer device 153. Next, the sheet 1 to which the toner image is transferred is sent onto the timing roller 181. At this time, the axes of the timing roller 181 and the auxiliary roller 182 and the traveling direction of the paper 1 are inclined by a certain angle θ from the vertical (FIG. 4). Further, the timing roller 181 and the auxiliary roller 182 are parallel. The sheet passing direction of the sheet 1 is changed by the timing roller 181. Here, the new traveling direction is a direction perpendicular to the timing roller 181.

  Next, the sheet 1 is sent onto the timing roller 183. The timing roller 183 changes the traveling direction of the paper 1 again. Here, the traveling direction after being changed by the timing roller 183 is parallel to the original traveling direction before being changed by the timing roller 181. The new traveling direction is perpendicular to the axis of the fixing roller 161 of the fixing device 160. Here, the position where the sheet 1 passes through the fixing device 160 is a position different from the position where the sheet 1 comes straight without being moved by the timing roller 181.

  Next, the sheet 1 is conveyed to the fixing device 160. Then, the fixing device 160 fixes the transferred image on the paper 1. As a result, printing on the paper 1 is completed. During the fixing, the sheet 1 takes heat from the sheet passing area of the fixing roller 161 of the fixing device 160. For this reason, the temperature of the sheet passing area of the fixing roller 161 is lowered and becomes lower than the temperature of the non-sheet passing area.

  The control unit 191 is driven after the trailing edge of the first sheet 1 passes through the timing roller 181 and the auxiliary roller 182 and before the leading edge of the second sheet 1 is conveyed to the timing roller 181. Move part 190. That is, the angle θ between the timing roller 181 and the auxiliary roller 182 is changed. As a result, the second sheet 1 passes through a different sheet passing path from the first sheet 1. This is because the second sheet 1 is fed in different directions by the timing roller 181. In this way, the location where the sheet passes through the fixing roller 161 is changed between the first sheet and the second sheet.

  Further, the third sheet 1 passes through a different sheet passing area from the second sheet. In other words, after that, the sheet 1 may pass through a portion different from the route through which the sheet was passed immediately before. For example, the first, third, fifth, and subsequent odd-numbered sheets 1 are placed on the right end of the fixing roller 161, the second, fourth, sixth, and even-numbered sheets 1 thereafter. May be passed through the left end of the fixing roller 161.

  Thereby, it is possible to avoid paper passing only to the same portion of the fixing roller 161. Therefore, it is possible to prevent heat from being removed only from the same portion of the fixing roller 161. Further, the degree of temperature unevenness that occurs in the fixing roller 161 can be suppressed.

  Thereafter, the direction of the timing roller 181 and the auxiliary roller 182 is changed every time a sheet is passed. Thereby, it is possible to avoid the sheet 1 from continuously passing through the same portion of the fixing roller 161. For this reason, temperature unevenness can be prevented from occurring in the fixing roller 161. Note that the control unit 191 moves the timing roller 181 and the auxiliary roller 182 through the drive unit 190 after the trailing edge of the sheet 1 is finished and before the leading edge of the next sheet 1 is supplied to the timing roller 181. Move it. The discharged printed paper 1 may be aligned by a general paper discharge alignment mechanism.

  Here, a modification of this embodiment will be described. In the above, a method of alternately passing the right end and the left end is given as an example. There are other methods for changing the paper path. For example, the first sheet is passed to the right end, the area to be passed after the second sheet is gradually shifted to the left, and for example, the tenth sheet is set to reach the left end. Then, you may make it reciprocate from the left end to the right end. Further, instead of reciprocating, the paper passing area change from the right end to the left end may be repeated.

  In the above description, the passage position of the sheet 1 is changed for each sheet. However, the passage position may be changed for each group of several sheets. For example, if two sheets form one group, after passing one group to the same portion of the fixing device 160, the next group may be passed to another portion. Even in this way, it is possible to prevent heat from being taken only from the same location.

  As described above in detail, the image forming apparatus 100 according to the present embodiment is configured to pass the continuously supplied paper 1 to different portions of the fixing roller 161 of the fixing device 160. is there. For this reason, a large number of sheets 1 do not pass only through the same location. Therefore, it can be avoided that the plurality of sheets 1 take heat only from the same portion of the fixing roller 161. That is, temperature unevenness hardly occurs on the fixing roller 161 of the fixing device. As a result, the image forming apparatus 100 that does not cause unevenness in the image even after printing on a plurality of small-sized sheets is realized.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the fixing device may not be a roller type. A belt system or the like may be used. Also, the heating method of the fixing device may be a pressure fixing method in addition to a lamp method such as halogen, a resistance heating element method, an induction heating method, or the like.

  In this embodiment, the paper passing area of the paper 1 is changed when printing on a large number of small-sized papers. However, even when one small-size sheet is printed out, it may be changed from the previous sheet passing area. This is because a plurality of users may continuously print out.

[Second form]
Hereinafter, the second embodiment will be described. In the image forming apparatus 100 according to the first embodiment described above, the sheet passing path of the sheet 1 is changed. On the other hand, the image forming apparatus 200 of the present embodiment presses the paper 1 at different locations of the fixing roller 261 by moving the fixing device 260 itself in the width direction.

  The configuration of the image forming apparatus 200 of this embodiment will be described with reference to FIGS. As shown in FIG. 6, the image forming apparatus 200 includes a paper feed cassette 101, a photoreceptor 110, a charging device 120, an exposure device 130, a developing device 140, a transfer device 153, a fixing device 260, and a cleaner. 170, a toner collection container 171, and a control unit 291. FIG. 6 is a schematic diagram corresponding to FIG. 3 of the first embodiment. The timing roller 181, the auxiliary roller 182, the timing roller 183, and the auxiliary roller 184 in FIG. 3 are not shown in FIG.

  Here, the fixing device 260 is a fixing unit having a fixing roller 261 as shown in FIG. The fixing roller 261 is for fixing the toner image on the paper 1. The pinion 262 is a rotating gear whose rotation axis is fixed to the image forming apparatus 200. The rack 263 is provided in the fixing device 260 and moves in the direction of the arrow X2 in FIG. 7 by the rotation of the pinion 262. Since the rack 263 is fixed to the fixing device 260, the fixing device 260 also moves in the direction of the arrow X2 in FIG. That is, the pinion 262 and the rack 263 are fixing unit moving units. Further, the control unit 291 performs other control in addition to controlling the fixing unit moving unit. The functions of other devices are the same as in the first embodiment.

  Here, FIG. 8 shows a case where the fixing device 260 is moved to the left end with respect to the sheet passing path. That is, the fixing device 260 and the rack 263 are close to the left end. On the other hand, the sheet passing path of the sheet 1 and the position of the pinion 262 are not changed from FIG. In this state, the sheet 1 passes through a position on the right side of the fixing device 260.

  FIG. 9 shows a case where the fixing device 260 is close to the right end with respect to the sheet passing path. At this time, while the fixing device 260 and the rack 263 are close to the right end, the sheet passing path of the sheet 1 and the position of the pinion 262 are not changed. In this state, the sheet 1 passes through the position on the left side of the fixing device 260.

  Here, the operation of the image forming apparatus 200 of this embodiment will be described. The image forming apparatus 200 operates as shown in the flowchart of FIG. 5 as a whole as in the first embodiment. The difference from the first embodiment is the sheet passing area setting printing (S10). In the sheet passing area setting printing of the image forming apparatus 200, the sheet 1 is pressed at different pressure points of the fixing roller 261 by moving the fixing device 260 itself instead of changing the path of the sheet 1. Hereinafter, the paper passing area setting printing in this embodiment will be described.

  Here, in the fixing unit, the fixing device 260 is positioned at the left end as shown in FIG. 8 as an initial state. Otherwise, the fixing device 260 is moved to the position shown in FIG. Therefore, the first sheet 1 passes through the right side of the fixing device 260.

  On the other hand, in the image forming unit, the toner image developed on the surface of the photoreceptor 110 is transferred onto the paper 1 by the transfer device 153. Next, the sheet 1 is conveyed to the fixing device 260. Then, the fixing roller 261 of the fixing device 260 fixes the toner image on the paper 1. As a result, printing on the paper 1 was performed. On the other hand, the undeveloped toner on the surface of the photoconductor 110 is collected in the toner collection container 171 by the cleaner 170.

  After the fixing of the first toner image to the paper 1 is completed, the fixing device 260 is moved to the right with respect to the traveling direction of the paper 1. Therefore, the second sheet 1 is conveyed to the left side of the fixing device 260 as shown in FIG. Then, the transfer image is fixed on the sheet 1 at the left end of the fixing roller 261. That is, the second sheet 1 is pressed by the fixing roller 261 different from the first sheet. For this reason, it is possible to avoid paper passing only to the same portion of the fixing roller 261. Further, it is possible to prevent heat from being taken only from the same portion of the fixing roller 261. Further, temperature unevenness hardly occurs in the fixing roller 261.

  Thereafter, the control unit 291 changes the position of the fixing device 260 every time a sheet is passed. For example, the area where the fixing roller 261 presses the sheet 1 is different between the third sheet 1 and the second sheet 1. In other words, after that, the sheet 1 may pass through a portion different from the route through which the sheet was passed immediately before.

  The control unit 291 moves after the trailing edge of the sheet 1 passes through the fixing roller 261 and before the leading edge of the next sheet 1 is supplied to the fixing roller 261. The discharged printed paper 1 may be aligned by a known paper discharge alignment mechanism.

  Here, a modification of this embodiment will be described. Similarly to the first embodiment, the first sheet can be passed to the right end, and the area through which the second and subsequent sheets are passed is gradually shifted to the left. For example, the 10th sheet can be set to reach the left end. Then, you may make it reciprocate from the left end to the right end. Further, instead of reciprocating, the paper passing area change from the right end to the left end may be repeated.

  In the above description, the passage position of the sheet 1 is changed for each sheet. However, the passage position may be changed for each group of several sheets. For example, if two sheets form one group, after passing one group to the same portion of the fixing device 160, the next group may be passed to another portion. This is because it is possible to prevent the heat from being removed only from the same location.

  As described above in detail, the image forming apparatus 200 according to the present embodiment is configured to pass the sheet 1 through different portions of the fixing roller 261 of the fixing device 260. For this reason, temperature unevenness hardly occurs in the fixing roller 261 of the fixing device. As a result, the image forming apparatus 200 that does not cause unevenness in the image even after printing on a plurality of small size sheets is realized.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the fixing device 260 may not be a roller type. A belt system or the like may be used. Also, the heating method of the fixing roller 261 may be a pressure fixing method in addition to a lamp method such as halogen, a resistance heating element method, an induction heating method, or the like. In this embodiment, the rack 263 and the pinion 262 are used. However, any device that can reciprocate such as a ball screw or a linear motor can be applied.

  In this embodiment, the paper passing area of the paper 1 is changed when printing on a large number of small-sized papers. However, even when one small-size sheet is printed out, it may be changed from the previous sheet passing area. This is because a plurality of users may continuously print out.

[Third embodiment]
The third embodiment will be described below. The sheet passing area setting printing of the image forming apparatus 300 of the present embodiment uses a plurality of sheet feeding cassettes to provide a plurality of sheet passing paths according to the arrangement of sheets in the sheet feeding cassette. Then, a toner image is formed at the position of the photoconductor 110 corresponding to the sheet passing path.

  The configuration of the image forming apparatus 300 of this embodiment will be described with reference to FIGS. As shown in FIG. 10, the image forming apparatus 300 includes a photoconductor 110, a charging device 120, an exposure device 330, a developing device 140, a transfer device 153, a fixing device 160, a cleaner 170, and a toner collection container. 171, a control unit 391, a paper feed cassette 301, and a paper feed cassette 302. FIG. 10 is a schematic diagram corresponding to FIG. 3 of the first embodiment. The timing roller 181, the auxiliary roller 182, the timing roller 183, and the auxiliary roller 184 in FIG. 3 are not shown in FIG.

  Here, the paper feed cassette 301 and the paper feed cassette 302 can set paper 1 of the same size. In this embodiment, as shown in FIGS. 11 and 12, the paper 1 set in the paper feed cassette 301 is placed on the lower side of the paper feed cassette 301 in the drawing, and the paper 1 set in the paper feed cassette 302. Is arranged in the sheet cassette 302 on the upper side in the figure. Here, the upper side in the figure is the right side with respect to the traveling direction of the paper 1, and the lower side in the figure is the left side with respect to the traveling direction of the paper 1. The paper feed cassette 301 and the paper feed cassette 302 are passage position changing sections that change the paper passing path of the paper 1.

  The exposure apparatus 330 includes a polygon mirror 331 and a polygon motor 332. In addition, the control unit 391 controls the image forming position by changing the scanning timing of the polygon mirror 331, selects a paper feeding cassette for paper feeding for each paper, and performs other controls. In addition, the function of each device is the same as in the first embodiment.

  Here, the operation of the image forming apparatus 300 of this embodiment will be described. As a whole, the operation as in the flowchart of FIG. 5 is the same as in the first embodiment. The difference from the first embodiment is the sheet passing area setting printing (S10). Hereinafter, the paper passing area setting printing in this embodiment will be described.

  In the sheet passing area setting printing in the image forming apparatus 300 of this embodiment, the sheet 1 is alternately supplied from the sheet feeding cassette 301 and the sheet feeding cassette 302 to the transfer device 153. First, as shown in FIG. 11, the first sheet 1 is supplied from the paper feed cassette 301 to the transfer device 153. Note that the first sheet may be supplied from the sheet feeding cassette 302.

  On the other hand, the charging device 120 uniformly charges the surface of the photoconductor 110. Then, the polygon mirror 331 of the exposure device 330 forms an electrostatic latent image on the surface of the photoreceptor 110. At this time, the position of the photoconductor 110 where the polygon mirror 331 forms the electrostatic latent image is on the sheet passing path A of the sheet 1, that is, on the left side with respect to the traveling direction of the sheet 1 as shown in FIG. That is, the polygon mirror 331 forms an electrostatic latent image at the position of the photoconductor 110 corresponding to the paper 1 passing path. Further, the developing device 140 applies toner to the electrostatic latent image on the surface of the photoconductor 110. Then, the transfer device 153 transfers the toner image on the surface of the photoconductor 110 to the paper 1.

  Subsequently, the sheet 1 to which the toner image is transferred is conveyed to the fixing device 160. The fixing device 160 fixes the transferred image on the paper 1. As a result, printing on the paper 1 was performed.

  After forming the first image, the control unit 391 changes the timing of the polygon motor 332 of the exposure apparatus 330, that is, the scanning timing of the polygon mirror 331. The second sheet is supplied from the sheet feeding cassette 302 to the transfer device 153. The polygon mirror 331 forms an electrostatic latent image on the surface of the photoconductor 110. At this time, the position of the photoconductor 110 where the polygon mirror 331 forms the electrostatic latent image is on the sheet passing path B of the sheet 1, that is, on the right side with respect to the traveling direction of the sheet 1 as shown in FIG.

  In this way, the control unit 391 changes the scanning timing of the polygon mirror 331 and the paper passing area of the paper 1 every time the printout is performed. For this reason, it is possible to avoid paper passing only to the same portion of the fixing roller 161. Further, it is possible to prevent heat from being taken only from the same portion of the fixing roller 161. In addition, temperature unevenness hardly occurs in the fixing roller 161.

  Here, a modification of this embodiment will be described. In the above description, the passage position of the sheet 1 is changed for each sheet. However, the passage position may be changed for each group of several sheets. For example, if two sheets form one group, after passing one group to the same portion of the fixing device 160, the next group may be passed to another portion. Even in this way, it is possible to prevent heat from being taken only from the same location.

  As described above in detail, the image forming apparatus 300 according to the present embodiment is configured to pass through different portions of the fixing roller 161 of the fixing device 160. For this reason, temperature unevenness hardly occurs in the fixing roller 161 of the fixing device 160. As a result, the image forming apparatus 300 that does not cause unevenness in the image even after printing on a plurality of small size sheets is realized.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the fixing device may not be a roller type. A belt system or the like may be used. Also, the heating method of the fixing device may be a pressure fixing method in addition to a lamp method such as halogen, a resistance heating element method, an induction heating method, or the like.

  In this embodiment, when printing on a large number of small-size sheets, the scanning timing of the polygon mirror 331 and the sheet passing area of the sheet 1 are changed. However, even when one small-size sheet is printed out, it may be changed from the previous sheet passing area. This is because a plurality of users may continuously print out.

[Fourth form]
Hereinafter, the fourth embodiment will be described. The image forming apparatus 400 according to this embodiment includes the timing roller 181 and the timing roller 183 according to the first embodiment provided upstream of the transfer device 153. For this reason, the sheet passing path is changed before the toner image is transferred. Then, image formation is performed at a position corresponding to the changed sheet passing path.

  The configuration of the image forming apparatus 400 of this embodiment will be described with reference to FIGS. As shown in FIG. 13, the image forming apparatus 400 includes a photoconductor 110, a charging device 120, an exposure device 330, a developing device 140, a transfer device 153, a fixing device 160, a cleaner 170, and a toner collection container. 171, a paper feed cassette 101, a timing roller 181, an auxiliary roller 182, a timing roller 183, an auxiliary roller 184, a driving device 190, and a control unit 491. FIG. 13 is a schematic diagram corresponding to FIG. 3 of the first embodiment. The timing roller 181, auxiliary roller 182, timing roller 183, and auxiliary roller 184 in FIG. 3 are upstream of the transfer device 153 in FIG.

  The exposure apparatus 330 is the same as that of the third embodiment, and has a polygon mirror 331 and a polygon motor 332 as shown in FIG. Further, the timing roller 181, the auxiliary roller 182, the timing roller 183, and the auxiliary roller 184 are the same as those in the first embodiment. However, these roller pairs are arranged between the paper feed cassette 101 and the transfer device 153. Note that the timing roller 181 and the timing roller 183 are passage position changing units that change the sheet passing path of the paper 1. The control unit 491 controls the image forming position by changing the scanning timing of the polygon mirror 331 to control the operation of the driving device 190 and perform other controls. The functions of other various devices are the same as in the first embodiment.

  Here, the operation of the image forming apparatus 400 of this embodiment will be described. As a whole, the operation as in the flowchart of FIG. 5 is the same as in the first embodiment. The difference from the first embodiment is the sheet passing area setting printing (S10). In the sheet passing area setting printing of the image forming apparatus 400, the sheet 1 is pressed at different pressing points of the fixing roller 161 by changing the sheet passing path of the sheet 1 as in the first embodiment. The difference from the first embodiment is that the sheet passing path of the sheet 1 is changed before the toner image is transferred. Hereinafter, the paper passing area setting printing in this embodiment will be described.

  First, the scanning timing of the polygon mirror 331 of the exposure device 330 and the angle θ of the timing roller 181 and the auxiliary roller 182 are set. On the other hand, the paper feed cassette 101 supplies the paper 1. The sheet passing direction of the sheet 1 is changed by the timing roller 181. For example, as shown in FIG. 14, the sheet passing direction of the sheet 1 is changed by the angle θ. Next, the sheet feeding direction is returned to the original by the timing roller 183. Accordingly, the sheet 1 passes on the right side with respect to the sheet passing direction from the passing position when the direction is not changed by the timing roller 181.

  On the other hand, the charging device 120 uniformly charges the surface of the photoconductor 110. Then, the polygon mirror 331 of the exposure device 330 forms an electrostatic latent image on the surface of the photoreceptor 110. At this time, the position of the photoconductor 110 where the polygon mirror 331 forms the electrostatic latent image is on the sheet passing path of the sheet 1, that is, on the right side with respect to the traveling direction of the sheet 1 as shown in FIG. That is, the polygon mirror 331 forms an electrostatic latent image at the position of the photoconductor 110 corresponding to the paper 1 passing path. Further, the developing device 140 applies toner to the electrostatic latent image on the surface of the photoconductor 110. Then, the transfer device 153 transfers the toner image on the surface of the photoconductor 110 to the paper 1.

  Subsequently, the sheet 1 to which the toner image is transferred is conveyed to the fixing device 160. The fixing device 160 fixes the transferred image on the paper 1. As a result, printing on the paper 1 was performed.

  After forming the first image, the control unit 491 changes the timing of the polygon motor 332 of the exposure apparatus 330, that is, the scanning timing of the polygon mirror 331. Further, the control unit 491 changes the angle θ of the timing roller 181 and the auxiliary roller 182 via the driving device 190. Therefore, the second sheet 1 is passed to the left with respect to the traveling direction as shown in FIG. Note that the image forming position by the image forming unit and the paper passing area of the paper 1 correspond to each other (see FIG. 15).

  In this way, the control unit 491 changes the scanning timing of the polygon mirror 331 and the paper passing area of the paper 1 each time it is printed out. For this reason, it is possible to avoid paper passing only to the same portion of the fixing roller 161. Further, it is possible to prevent heat from being taken only from the same portion of the fixing roller 161. In addition, temperature unevenness hardly occurs in the fixing roller 161.

  Here, a modification of this embodiment will be described. As in the first embodiment, the first sheet is passed to the right edge, and the second and subsequent sheets are gradually shifted to the left. For example, the 10th sheet is set to reach the left edge. Then, you may make it reciprocate from the left end to the right end. Further, instead of reciprocating, the paper passing area change from the right end to the left end may be repeated.

  In the above description, the passage position of the sheet 1 is changed for each sheet. However, the passage position may be changed for each group of several sheets. For example, if two sheets form one group, after passing one group to the same portion of the fixing device 160, the next group may be passed to another portion. Even in this way, it is possible to prevent heat from being taken only from the same location.

  As described above in detail, the image forming apparatus 400 according to the present embodiment is configured to pass the continuously supplied paper 1 to different portions of the fixing roller 161 of the fixing device 160. Therefore, a plurality of sheets 1 do not pass only through the same location. Therefore, it can be avoided that the plurality of sheets 1 take heat only from the same portion of the fixing roller 161. That is, temperature unevenness hardly occurs on the fixing roller 161 of the fixing device 160. As a result, the image forming apparatus 400 that does not cause unevenness in the image even after printing on a plurality of small-sized sheets is realized.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the fixing device may not be a roller type. A belt system or the like may be used. Also, the heating method of the fixing device may be a pressure fixing method in addition to a lamp method such as halogen, a resistance heating element method, an induction heating method, or the like.

  In this embodiment, the angles of the timing roller 181 and the auxiliary roller 182 are changed when printing on a large number of small sheets. However, the angle of the timing roller 181 and the auxiliary roller 182 may be changed when printing out a plurality of sheets at the same time, not limited to a small size sheet. This is because there is no change in that temperature unevenness hardly occurs in the fixing roller 161.

[Fifth embodiment]
Hereinafter, the fifth embodiment will be described. The image forming apparatus 500 according to the present embodiment includes a mechanism for changing the position where the paper 1 is fed to the paper feed cassette 501 itself. As a result, the sheet passing area of the sheet 1 is changed. Further, the adjustment of the image forming position is accordingly the same as in the third and fourth embodiments.

  The configuration of the image forming apparatus 500 of this embodiment will be described with reference to FIGS. The image forming apparatus 500 includes a paper feed cassette 501, a photoreceptor 110, a charging device 120, an exposure device 330, a developing device 140, a transfer device 153, a fixing device 160, a cleaner 170, and a toner collection container 171. And a control unit 591. FIG. 16 is a schematic diagram corresponding to FIG. 3 of the first embodiment. The timing roller 181, the auxiliary roller 182, the timing roller 183, and the auxiliary roller 184 in FIG. 3 are not shown in FIG.

  As shown in FIG. 17, the paper feed cassette 501 includes side regulating plates 511 and 512, a ball screw 513, a motor 514, a compression coil spring 515, a push-up plate 516, and a paper feed roller 517. ing. Here, the side regulating plates 511 and 512, the ball screw 513, and the motor 514 are stacking position changing units that change the position where the sheets 1 are stacked. In addition, the exposure apparatus 330 includes a polygon mirror 331 and a polygon motor 332 as shown in FIGS.

  The motor 514 is for moving the side regulating plates 511 and 512 on both sides via the ball screw 513 in the direction of the arrow in FIG. That is, the side regulating plates 511 and 512, the ball screw 513, and the motor 514 are passage position changing units for changing the paper passing path of the paper 1. The control unit 591 controls the image forming position by changing the scanning timing of the polygon mirror 331, and controls the stacking position changing unit and performs other controls. In addition, the function of each device is the same as in the first embodiment.

  Here, the operation of the image forming apparatus 500 of this embodiment will be described. As a whole, the operation as in the flowchart of FIG. 5 is the same as in the first embodiment. The difference from the first embodiment is the sheet passing area setting printing (S10). The difference from the first embodiment is that the sheet passing path of the sheet 1 is changed by the mechanism of the sheet feeding cassette 501 as the sheet passing area setting printing of the image forming apparatus 500.

  Hereinafter, the sheet passing area setting printing in this embodiment will be described with reference to the flowchart of FIG. First, an area for paper passing is set (S11). Next, it is determined whether or not there is a paper gap, and the process waits until the paper gap is reached (S12). Next, as shown in FIG. 17, the control unit 591 controls the motor 514 to set the rotation direction of the motor 514 corresponding to the moving direction of the side regulating plates 511 and 512 (S13). At this time, the rotation amount of the motor 514 is also set. In addition, the scanning timing of the polygon mirror 331 of the exposure apparatus 330 is changed. Next, the motor 514 is rotated by a predetermined amount (S14). Then, as shown below, it prints on a paper (S15).

  Next, as shown in FIG. 18, the paper feed cassette 501 passes the paper 1 to the left side in the traveling direction. On the other hand, the charging device 120 uniformly charges the surface of the photoconductor 110. Then, the polygon mirror 331 of the exposure device 330 forms an electrostatic latent image on the surface of the photoreceptor 110. At this time, the position of the photoconductor 110 on which the polygon mirror 331 forms an electrostatic latent image is on the sheet passing path A of the sheet 1, that is, on the left side with respect to the traveling direction of the sheet 1 as shown in FIG. That is, the polygon mirror 331 forms an electrostatic latent image at the position of the photoconductor 110 corresponding to the paper 1 passing path. Further, the developing device 140 applies toner to the electrostatic latent image on the surface of the photoconductor 110. Then, the transfer device 153 transfers the toner image on the surface of the photoconductor 110 to the paper 1.

  Subsequently, the sheet 1 to which the toner image is transferred is conveyed to the fixing device 160. The fixing device 160 fixes the transferred image on the paper 1. As a result, printing on the paper 1 was performed.

  After forming the first image, the control unit 591 changes the timing of the polygon motor 332 of the exposure apparatus 330, that is, the scanning timing of the polygon mirror 331. At the same time, the direction θ of the timing roller 181 is adjusted. The second sheet is supplied from the paper feed cassette 501 to the transfer device 153. Next, the polygon mirror 331 forms an electrostatic latent image on the surface of the photoconductor 110. At this time, the position of the photosensitive member 110 on which the polygon mirror 331 forms an electrostatic latent image is on the sheet passing path B of the sheet 1, that is, on the right side with respect to the traveling direction of the sheet 1 as shown in FIG.

  As described above, the control unit 591 changes the scanning timing of the polygon mirror 331 and the paper passing area of the paper 1 every time the printout is performed. For this reason, it is possible to avoid paper passing only to the same portion of the fixing roller 161. Further, it is possible to prevent heat from being taken only from the same portion of the fixing roller 161. In addition, temperature unevenness hardly occurs in the fixing roller 161. The above process is repeated from S13 to S15 until all printing is completed. As a result, printing is performed.

  Here, the operation of the side regulating plates 511 and 512 in the paper feed cassette 501 will be described with reference to FIG. First, the motor 514 rotates by a certain step. Accordingly, the ball screw 513 rotates. As a result, the plate having the side regulating plates 511 and 512 moves in the width direction of the paper 1. The side regulating plate 511 can be moved in the width direction according to the size of the paper.

  Here, a modified example of this embodiment will be described. As in the first embodiment, the first sheet is passed to the right edge, and the second and subsequent sheets are gradually shifted to the left. For example, the 10th sheet is set to reach the left edge. Then, you may make it reciprocate from the left end to the right end. Further, instead of reciprocating, the paper passing area change from the right end to the left end may be repeated.

  In the above description, the passage position of the sheet 1 is changed for each sheet. However, the passage position may be changed for each group of several sheets. For example, if two sheets form one group, after passing one group to the same portion of the fixing device 160, the next group may be passed to another portion. Even in this way, it is possible to prevent heat from being taken only from the same location.

  Further, although the paper feed cassette 501 of this embodiment is used, a plurality of paper feed cassettes 501 may be used for the same size paper. In the paper feed cassette 501, the ball screw 513 is used to move the side regulating plates 511 and 512, but a pulley 561 and a wire 562 may be used as shown in FIG. Even in this case, the motor 514 can be used as shown in FIG.

  As described above in detail, the image forming apparatus 500 according to the present embodiment is configured to pass through different portions of the fixing roller 161 of the fixing device 160. For this reason, temperature unevenness hardly occurs in the fixing roller 161 of the fixing device 160. As a result, an image forming apparatus 500 that does not cause unevenness in an image even after printing on a plurality of small-sized sheets is realized.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the fixing device may not be a roller type. A belt system or the like may be used. Also, the heating method of the fixing device may be a pressure fixing method in addition to a lamp method such as halogen, a resistance heating element method, an induction heating method, or the like.

  In this embodiment, when printing on a large number of small-size sheets, the scanning timing of the polygon mirror 331 and the sheet passing area of the sheet 1 are changed. However, even when one small-size sheet is printed out, it may be changed from the previous sheet passing area. This is because a plurality of users may continuously print out.

FIG. 6 is a plan view for explaining a sheet passing area and a non-sheet passing area in the fixing device. It is a figure for demonstrating the image forming apparatus of this invention. It is a figure for demonstrating the image forming apparatus which concerns on a 1st form. FIG. 6 is a plan view for explaining a sheet passing path of a sheet to which a toner image is transferred in the image forming apparatus according to the first embodiment. 3 is a flowchart for explaining the operation of the image forming apparatus according to the present invention. It is a figure for demonstrating the image forming apparatus which concerns on a 2nd form. FIG. 9 is a plan view for explaining the movement of a fixing device in an image forming apparatus according to a second embodiment. FIG. 10 is a diagram (No. 1) for explaining a relationship between a fixing device and a sheet passing path in an image forming apparatus according to a second embodiment. FIG. 10 is a diagram (No. 2) for explaining the relationship between the fixing device and the sheet passing path in the image forming apparatus according to the second embodiment. It is a figure for demonstrating the image forming apparatus which concerns on a 3rd form. FIG. 10 is a plan view (No. 1) for explaining a relationship between a sheet passing path and an image forming position in an image forming apparatus according to a third embodiment. FIG. 10 is a plan view (No. 2) for explaining a relationship between a sheet passing path and an image forming position in an image forming apparatus according to a third embodiment. It is a figure for demonstrating the image forming apparatus which concerns on a 4th form. FIG. 10 is a plan view (No. 1) for explaining a relationship between a sheet passing path and an image forming position in an image forming apparatus according to a fourth embodiment. FIG. 10 is a plan view (No. 2) for explaining a relationship between a sheet passing path and an image forming position in an image forming apparatus according to a fourth embodiment. It is a figure for demonstrating the image forming apparatus which concerns on a 5th form. It is sectional drawing for demonstrating the paper feed cassette of the image forming apparatus which concerns on a 5th form. FIG. 10 is a plan view (No. 1) for explaining a relationship between a sheet passing path and an image forming position in an image forming apparatus according to a fifth embodiment. FIG. 10 is a plan view (No. 2) for explaining a relationship between a sheet passing path and an image forming position in an image forming apparatus according to a fifth embodiment. 14 is a flowchart for explaining sheet passing area setting printing of an image forming apparatus according to a fifth embodiment. It is a top view for demonstrating the mechanism of the paper feed cassette of the image forming apparatus which concerns on a 5th form. It is sectional drawing for demonstrating another paper feed cassette of the image forming apparatus which concerns on a 5th form. It is a top view for demonstrating the mechanism of another paper feed cassette of the image forming apparatus which concerns on a 5th form.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Paper 10 ... Image forming part 100,200,300,400,500 ... Image forming apparatus 101,301,302,501,551 ... Paper cassette 110 ... Photoconductor 120 ... Charging device 130,330 ... Exposure device 140 ... Developing device 153... Transfer device 160, 260... Fixing device 161, 261... Fixing roller 181, 183... Timing roller 182, 184. 332 ... Polygon motors 511, 512 ... Side regulating plate 513 ... Ball screw 514 ... Motor 561 ... Pulley 562 ... Wire

Claims (7)

An image forming unit that forms a toner image, a transfer unit that transfers the toner image formed by the image forming unit onto the transfer target, and a toner image on the transfer target that has passed through the transfer unit on the transfer target In an image forming apparatus having a fixing unit for fixing,
A passing position changing unit that changes the passing position of the transfer object in the width direction of the fixing unit;
When the image is continuously formed on the transfer body having a lateral width smaller than the entire width of the fixing unit, the passing position of the transfer body is changed by the passing position changing unit for each transfer target or the group thereof. An image forming apparatus comprising: a position control unit. The image forming apparatus according to claim 1,
The passing position changing unit is
A swing roller pair for changing the sheet passing direction of the transfer body to the width direction of the fixing unit;
A pair of fixed rollers for returning the sheet passing direction of the transferred body to a direction parallel to the original traveling direction;
The image forming apparatus, wherein the swing roller pair and the fixed roller pair are disposed between the transfer unit and the fixing unit. The image forming apparatus according to claim 1,
The image forming apparatus, wherein the passing position changing unit is a fixing unit moving unit that moves the fixing unit in a width direction thereof. The image forming apparatus according to claim 1,
The passage position changing section is upstream of the transfer section on the sheet passing path;
An image forming apparatus, comprising: an image forming position control unit that changes a toner image forming position in the image forming unit in accordance with a sheet passing path changed by the passage position changing unit. The image forming apparatus according to claim 4,
The passage position changing unit has a plurality of paper feed cassettes that can be provided with transferred bodies of the same size,
The plurality of paper feed cassettes are different from each other in a stacking position of the transfer object in the width direction of the fixing unit,
2. The image forming apparatus according to claim 1, wherein the passage position control unit is configured to change a paper feed cassette from which the individual transfer target or each group thereof is fed. The image forming apparatus according to claim 4,
The passing position changing unit is
A swing roller pair for changing the sheet passing direction of the transfer body to the width direction of the fixing unit;
An image forming apparatus comprising: a pair of fixed rollers for returning a sheet passing direction of a transfer medium to a direction parallel to the original traveling direction. The image forming apparatus according to claim 4,
2. The image forming apparatus according to claim 1, wherein the passage position changing unit is a stacking position changing unit that changes the stacking position of the transfer medium inside the sheet feeding cassette.

Images