JP2007121477A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that is not made to stop operating and can improve productivity. <P>SOLUTION: In the image forming apparatus comprising an image carrier, a recording material carrier, a cleaning means, a storage means of storing recording materials, a conveyance path for conveying a recording materials to the recording material carrier, a size detecting means of detecting the size of the recording material disposed on the conveyance path, a comparing means of comparing the size of the recording material detected by the size detecting means with the size of a toner image, a storage means of storing the position of toner transferred onto the recording material carrier based upon the result of the comparison made by the comparing means, and a conveyance timing control means of controlling the timing where the recording material is conveyed from the conveyance path to the recording material carrier, the conveyance timing control means performs control so that the toner image on the recording material carrier and the recording material on the recording material carrier do not overlap each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using an electrophotographic system, for example, an image forming apparatus such as a copying machine, a printer, and a FAX.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic copying machine, a recording material on which an image is formed is discharged out of the apparatus after the recording material is fed to the recording material, and the image on the transferred recording material is fixed. It is usual to have such a series of conveyance paths. In particular, when a toner image is transferred to a recording material, there is an apparatus that employs a configuration in which the recording material is electrostatically attracted to a transfer belt and then conveyed to a transfer position (see Patent Document 1).

  In addition, when the toner image transferred onto the transfer belt is not transferred to the recording material and adheres to the recording material, the back surface of the recording material is contaminated with toner, so that a cleaning member is generally brought into contact with the transfer belt. (See Patent Document 2).

Although this cleaning member is suitable for collecting a small amount of toner on the transfer belt, it cannot collect a large amount of toner transferred to the transfer belt at one time. Image forming apparatus that transfers the recording material while avoiding the density correction toner image when performing control such that the toner image is transferred, read by a toner sensor, and image forming parameters are changed (Patent Document) 3), and an image forming apparatus (see Japanese Patent Application Laid-Open No. H10-228707) that controls separately a region for transferring a toner image for density correction and a region for conveying a recording material.
JP-A-5-346741 Japanese Patent Laid-Open No. 10-031394 JP 2001-215859 A Japanese Patent Application Laid-Open No. 6-043729

  However, in the conventional technology, it is assumed that the toner image size is the same as the recording material size or smaller than the recording material size, and the toner image size is larger than the recording material size. Since the cleaning of the toner image transferred onto the transfer belt was not taken into consideration, when such a state occurred, the operation of the apparatus had to be stopped as an abnormal state.

  The present invention has been made in view of the above problems, and the intended processing is that the operation is not stopped, productivity can be improved, and even if a plurality of toner images are on the transfer belt, An object of the present invention is to provide an image forming apparatus that can be controlled while avoiding them.

In order to achieve the above object, according to the first aspect of the present invention, there is provided an image carrier on which a toner image is formed, a recording material carrier on which a recording material is carried and conveyed, and a toner image transferred from the image carrier. Cleaning means that contacts the surface of the recording material carrier after separating the recording material and cleans the surface of the recording material carrier, storage means for storing the recording material, and storage means stored in the storage means A conveyance path for conveying the recording material to the recording material carrier, a size detection means for detecting the size of the recording material disposed on the conveyance path, a size of the recording material detected by the size detection means, and a toner image Comparison means for comparing the size, storage means for storing the position of the toner transferred onto the recording material carrier based on the comparison result of the comparison means, and recording material from the conveyance path to the recording material carrier Transport A transfer timing control means for controlling the timing, an image forming apparatus having a,
The conveyance timing control unit controls the toner image on the recording material carrier so that the recording material on the recording material carrier does not overlap.

  According to the present invention, the case where the size of the toner image is larger than the size of the recording material is detected, the conveyance of the recording material is avoided while avoiding the toner image, and the normal conveyance control is performed after the cleaning of the toner image is completed. By returning, the operation is not stopped and productivity is improved. Even if a plurality of toner images are on the transfer belt, they can be controlled while avoiding them.

<Embodiment 1>
First, FIG. 1 shows a schematic sectional view of an image forming apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, 100 is an image forming apparatus main body, and 280 is an automatic document feeder (DF). Reference numeral 201 denotes a platen glass as a document placement table, and 202 denotes a scanner, which includes a document illumination lamp 203, a scanning mirror 204, and the like. The scanner is reciprocated in a predetermined direction by a motor (not shown), and the reflected light of the original passes through the lens 207 via the scanning mirrors 204 to 206 and forms an image on the CCD sensor in the image sensor unit 208.

  Reference numeral 210 denotes an exposure control unit composed of a laser, a polygon scanner, and the like. The exposure control unit 210 sensitizes a laser beam 219, which is converted into an electric signal by the image sensor unit 208 and modulated based on an image signal subjected to predetermined image processing to be described later. The body drum 211 is irradiated. Around the photosensitive drum 211, a primary charger 212, a developing device 213, a transfer roller 216, a pre-exposure lamp 214, and a cleaning device 215 are provided.

  In the image forming unit 209, the photosensitive drum 211 is rotated in the direction of the arrow shown in the figure by a motor (not shown). After being charged to a desired potential by the primary charger 212, the laser from the exposure control unit 210 is supplied. Light 219 is irradiated to form an electrostatic latent image. The electrostatic latent image formed on the photosensitive drum 211 is developed by the developing device 213 and visualized as a toner image.

  On the other hand, the recording paper fed from the right cassette deck 221, the left cassette deck 222, the upper cassette 223 or the lower cassette 224 by the pickup rollers 225, 226, 227, 228 is fed by the paper feeding rollers 229, 230, 231, 232. It is sent to the conveyance path, and is fed to the transfer belt 234 by the registration roller 233. Then, the toner image visualized on the photosensitive drum 211 is transferred onto the recording paper by the transfer roller 216. After the transfer, the photosensitive drum 211 is cleaned of residual toner by the cleaner device 215, and the residual charge is erased by the pre-exposure lamp 214. The transfer belt 234 has a home position flag 258, and the home position flag 258 is disposed so as to pass through a home position sensor 259 that detects passage of the flag.

  The recording sheet after transfer moves along with the transfer belt 234, is separated from the transfer belt 234 by the separation charger 217, and is sent to the fixing device 235 as it is. The toner transferred from the photosensitive drum 211 to the area outside the recording paper adheres to the transfer belt 234, and this attached toner is cleaned by the transfer belt cleaner 218. The recording paper sent to the fixing device is fixed with toner by pressurization and heating, and is discharged out of the main body 100 by the inner discharge roller 236 and the discharge roller 244.

  The main body 100 is equipped with a deck 250 that can store 4000 sheets of recording paper. The lifter 251 of the deck 250 is raised according to the amount of recording paper so that the recording paper always abuts against the pickup roller 252, and the recording paper is sent to the transport path in the main body by the paper feed roller 253.

  Further, a multi-manual feed 254 capable of accommodating 100 recording sheets is provided, and this is also transported to the registration roller 233 by a paper feed roller 255 and a transport roller 256. Reference numeral 257 denotes a registration sensor that detects the passage of the recording paper, and is disposed in front of the registration roller 233.

  Further, in FIG. 1, reference numeral 237 denotes a paper discharge flapper, which switches the path between the conveyance path 238 side and the discharge path 243 side. A lower conveyance path 240 guides the recording paper fed from the inner paper discharge roller 236 to the refeeding path 241 by turning the recording paper over the reverse path 239. The recording paper fed from the left cassette deck 222 by the paper feed roller 230 is also guided to the refeed path 241. A refeed roller 242 refeeds the recording sheet to the image forming unit 209. A discharge roller 244 is disposed in the vicinity of the discharge flapper 237 and discharges the recording paper switched to the discharge path 243 side by the discharge flapper 237 to the outside of the apparatus.

  During double-sided recording (double-sided copying), the paper discharge flapper 237 is raised upward, and the copied recording paper is guided to the refeeding path 241 through the reverse path 239 and the lower transport path 240. At this time, the reverse roller 245 pulls the reverse end of the recording paper to the reverse path 239 and reverses the reverse roller 245 to send it to the lower conveyance path 240. When the recording paper is reversed and discharged from the main body, the discharge flapper 237 is lifted upward, and the reverse roller 245 leaves the rear end of the recording paper and draws it into the reverse path 239, and reverses the reverse roller 245. The recording paper is turned over and sent to the discharge roller 244 side.

  A paper discharge processing apparatus 290 aligns and closes the recording paper discharged from the main body 100 and stacks the recording paper discharged one by one on the processing tray 294 so as to be aligned. When the discharge of a part of the image formation is completed, the recording paper bundle is stapled and discharged to the discharge tray 292 or 293 as a bundle. The paper discharge tray 293 is controlled to move up and down by a motor (not shown) and moves to the position of the processing tray 294 before starting the image forming operation. Thereafter, when the discharged recording paper is stacked, The height is moved to the position of the processing tray 294.

  Further, reference numeral 291 denotes a paper tray on which separator sheets to be inserted between the discharged recording sheets are stacked, and reference numeral 295 denotes a Z-folding machine that Z-folds the discharged recording sheets. Further, reference numeral 296 denotes a bookbinding machine that performs bookbinding by collectively folding a part of the discharged recording paper and performing stapling, and the bound paper bundle is discharged to a discharge tray 297.

  Next, a toner image transferred onto the transfer belt 234 in the present embodiment will be described with reference to FIG.

  Usually, the image size is determined in accordance with the size of the recording material P, and the exposure control unit 210 irradiates the photosensitive drum 211 with laser light.

  Since the size of the recording material P is designated by the user, when the user designates the size of the recording material P as a size larger than the actual size, the exposure is stopped when the registration sensor 257 detects the trailing edge of the recording material P. .

  However, when the distance from the registration sensor 257 to the transfer position is shorter than the distance from the exposure position to the transfer position, a toner image having a difference between the lengths indicated by T is transferred to the transfer belt 234. become.

  Next, an outline of the control of the present embodiment will be described with reference to a block diagram for explaining the control of the image forming apparatus of FIG.

  First, a sheet size determination unit 501 measures the time from when the registration roller 233 is turned on until the trailing edge of the recording material passes through the registration sensor 257, and the length of the recording material in the sub-scanning direction is determined as the passage time * conveying speed. From the above, the sheet size is determined. A conveyance timing control unit 502 includes a conveyance motor 504 (not shown in FIG. 1), a belt motor 505 that drives the transfer belt 234, a conveyance clutch 506, and a registration clutch 507 that transmits the drive of the conveyance motor 504 to the registration roller 233. By controlling, the recording material is transported from each storage (right cassette deck 221, left cassette deck 222, upper cassette 223, lower cassette 224, multi-manual feed 254) to the transfer position. Further, the conveyance timing control unit 502 notifies the video control unit 508 of the exposure start timing of the exposure control unit 210.

  Next, reference numeral 503 denotes a toner position determination unit. When the sheet size determination unit 501 determines the sheet size, the result is compared with the image size to be transferred, and whether or not the toner image is transferred onto the transfer belt 234. Judging.

  The toner position determination unit 503 stores the position of the transferred toner image using the signal from the transfer belt home position sensor 259 as a reference position. Using the determination result of the toner position determination unit 503, the conveyance timing control unit 502 controls the conveyance timing so that the toner image on the transfer belt does not overlap the recording material.

  Reference numeral 509 denotes a timer, which performs counting at a predetermined cycle. By referring to the count value of the timer 509 at an arbitrary timing, the elapsed time between the arbitrary timings can be obtained. The toner position determination unit 503 obtains the density information (video count value) of the exposed image from the video control unit 508, thereby calculating the toner concentration of the toner image transferred onto the transfer belt. In order to clean the toner image, it is determined how many times the cleaner 218 should be passed.

  Next, control of the sheet size determination unit 501 and the toner position determination unit 503 will be described using the flowchart of FIG. This control is performed when the trailing edge of the recording material passes the registration sensor 257.

  First, in S301, as described above, the sheet size is obtained from the time from when the registration clutch 506 is turned on until the trailing edge of the recording material passes through the registration sensor 257. For example, when the time is x, the sheet size y is obtained by y = a + x * b, where a is the distance between the registration roller 233 and the registration sensor 257 and b is the conveyance speed.

  Next, the process proceeds to S302, and if the exposure control unit 210 is exposing the photosensitive drum 211, the process proceeds to S303 and the exposure is turned off. As described above, in S303, since the toner image is transferred to the transfer belt 234, the process proceeds to S304, and the apparatus is set in the cleaning mode.

  In step S305, the size of the toner image transferred to the belt is calculated. Specifically, it is the difference between the sheet size calculated in S301 and the exposure size exposed by the exposure control unit 210. Following S305, the process proceeds to S306, where the position of the toner image transferred to the belt is stored, and the process proceeds to S307 to determine the cleaning end condition. This is the number of times the toner image is passed through the cleaner unit 218, which is determined by the toner density of the toner image transferred onto the transfer belt 234 and the size of the toner image.

  On the other hand, if the exposure has already been completed in S302, the process proceeds to S308, where the sheet size and the image size are compared. If the image size is larger, the process proceeds to S304, and if it is smaller, the control is terminated.

  Next, a toner position determination method of the toner position determination unit 503 will be described with reference to FIG.

  First, FIG. 4A will be described. In the graph of FIG. 4A, the vertical axis represents the count value and the horizontal axis represents the time. The count value is a value counted by the timer 509 in FIG. 5, and when the home position flag 258 passes the home position sensor 259, the count value is cleared, so that the count value becomes 0 and immediately before the home position. The count value becomes the maximum. Therefore, when the rear end of the sensor is detected at the timing of the broken line 401, the toner on the photoconductor 211 is transferred to the transfer belt 234 at the timing of 402. By storing the count value indicated by 402, it is possible to know the timing at which the transfer belt 234 makes one round thereafter and the toner image reaches the transfer position again. Reference numerals 403 and 404 denote timings at which the first and second round toner images reach the transfer position, respectively.

  Next, the control of the transport timing control unit in the present embodiment will be described using the flowchart of FIG. This flowchart is executed for each recording material immediately before the recording material reaches the registration sensor 257.

  First, in S701, it waits for the registration sensor 257 to detect the leading edge of the recording material. When the leading edge of the recording material is detected, the process proceeds to S702, and it is checked whether or not the cleaning mode is set. The setting of the cleaning mode state is set by the actions of the sheet size determination unit 501 and the toner position determination unit 503 as described with reference to FIG. In S702, if it is in the cleaning mode state, the process proceeds to S703 to check whether the cleaning end condition is satisfied. The cleaning end condition is the number of rotations of the transfer belt determined in S307 of FIG.

  If the predetermined number of transfer belts have been rotated after the toner image has been transferred to the transfer belt 234, the process proceeds to S708, and if the number of rotations has not been reached, the process proceeds to S704. In S704, an expected arrival time TA when the recording material is conveyed from the registration sensor position to the transfer position is calculated.

  In step S705, the time TB at which the toner image on the transfer belt 234 appears at the transfer position is based on the timing at which the home position sensor 259 detects the home position flag 258 as described with reference to FIG. Asking. Note that the estimated arrival time in S704 is also obtained using the same standard. Then, the process proceeds to S706, where TA and TB are compared. It is determined whether or not there is an overlap between TA until the trailing edge of the recording material exits the transfer position and TB until the trailing edge of the toner image exits the transfer position. If they overlap, the process proceeds to S707 and the registration clutch 507 is activated. The drive timing is delayed so that the toner image and the recording material do not overlap.

  On the other hand, if they do not overlap, the process proceeds to S708, and the registration clutch 507 is driven at the normal drive timing. If the cleaning end condition has been reached in S703, the process proceeds to S708, the cleaning mode state is canceled, the process proceeds to S709, and the registration clutch 507 is driven at the normal drive timing.

  Next, a description will be given of the legion timing control method described in S707 and S709 in the flowchart of FIG. 7 with reference to the diagram of FIG. In the diagram of FIG. 6, the horizontal axis is time, and the vertical axis is distance.

  The relative distances of the registration sensor 257, the registration roller 233, and the transfer position when the position of the recording material storage is 0 is shown. The solid lines in the graph indicate the positions of the leading and trailing edges of the recording material, and FIG. 6 shows how the three recording materials (P1, P2, P3) are conveyed. If the size of the image is larger than the size of the recording material in P1, the toner image I1 is transferred to the transfer belt at the timing shown in the drawing. Since this toner image I1 appears at the transfer position with a period of one round of the belt (I2 in the figure), I2 appears at the transfer position after a lapse of one belt round from I1.

  Next, when the arrival timing at the transfer position and the appearance timing of I2 are compared when the recording material P2 is registered at a normal timing (P1's reion timing + T1), the recording material P2 starts to be conveyed at the normal regio timing. I understand that I can do it. Accordingly, the recording material P2 can be started to be transferred to the transfer position with a normal region period T.

  The recording material P3 calculates the arrival timing at the transfer position when conveyance is started in the normal regione cycle T1, and the appearance timing of the toner image I2 calculated earlier is compared, and the trailing edge of the recording material P3 and the toner image I2 are compared. Therefore, the conveyance is started by setting the reion cycle to T2 so as not to overlap. The registration cycle T2 is a timing at which the recording material P3 is turned on at the registration sensor 257. When the recording material P3 is conveyed at the timing indicated by the broken line, the recording material P3 reaches the transfer position. Calculate and determine the arrival time. The calculation can be easily calculated from the conveyance speed, the distance between the sensor, the roller, and the transfer position, the size of the recording material P3, and the time that the recording material P3 waits at the position of the registration roller 233.

  On the other hand, the appearance timing of the toner image I2 is as described with reference to FIG. 4A, and by comparing these, the registration period T2 that prevents the toner image I2 and the recording material P3 from overlapping is calculated. Is possible. The time TD from when the trailing edge of the toner image I2 passes the transfer position to when the leading edge of the recording material P3 whose timing is delayed passes increases according to the number of rotations of the toner image, thereby cleaning. As a result, it is possible to cope with the diffusion of the toner image on the transfer belt 234 to enlarge the area.

<Embodiment 2>
In the first embodiment, the home position flag 258 and the home position sensor 259 are arranged to store the position of the toner image on the transfer belt 234. However, the position of the toner image can be stored without them. Is possible. The embodiment will also be described with reference to FIG.

  In the graph of FIG. 4B, the vertical axis is the count value and the horizontal axis is the time, as in FIG. The count value is a value counted by the timer 509 in FIG. 5, and the timer 509 is a free-run timer that next becomes 0 when the count value becomes FFFFh. From the timer period, the belt circumferential length, and the belt conveyance speed, the number of counts for one belt revolution is obtained.

  Assuming that the belt circumference is L, the belt conveyance speed is V, and the timer period is T, the count number N is obtained by N = L / V / T. That is, when the registration sensor 257 detects the trailing edge of the recording material in 410, if the toner image is transferred to the transfer belt 234 at the timing of 411, the count number N is added to the count value of the timer 509 at the timing of 411. By adding, the count value at the timing 412 at which the next toner image appears can be obtained.

<Embodiment 3>
FIG. 8 shows a configuration around the transfer belt of the image forming apparatus according to the third embodiment. In this configuration, a toner sensor 260 is arranged with respect to the image forming apparatus 100 described with reference to FIG.

  The toner on the transfer belt 234 is detected by the toner sensor 260. In the case of the present embodiment, the output value of the toner sensor that determines that the cleaning is completed is determined in S307 of the flowchart of FIG. In the case of the present embodiment, the cleaning end determination performed in S703 of the flowchart of FIG. 7 is performed by comparing the output value of the toner sensor with a predetermined value instead of the number of rotations of the transfer belt 234.

<Embodiment 4>
The control of the image forming apparatus in the fourth embodiment will be described. The image forming apparatus in the fourth embodiment has the same configuration as the image forming apparatus in the first embodiment.

  First, control of the sheet size determination unit 501 and the toner position determination unit 503 will be described with reference to the flowchart of FIG. This control is performed when the trailing edge of the recording material passes the registration sensor 257.

  First, in S901, as described above, the sheet size is obtained from the time from when the registration clutch 506 is turned on until the trailing edge of the recording material passes through the registration sensor 257. For example, when the time is x, the sheet size y is obtained by y = a + x * b, where a is the distance between the registration roller 233 and the registration sensor 257 and b is the conveyance speed.

  In step S902, if the exposure control unit 210 is exposing the photosensitive drum 211, the process advances to step S903 to turn off the exposure. As described above, since the toner image is transferred to the transfer belt 234 in the case of S903, the process proceeds to S905, and the leading end position of the toner image transferred to the belt is determined.

  In step S906, the rear end position of the toner image transferred to the belt is determined. Specifically, the count value of the timer 509 when the sensor is OFF is read out, and the count value corresponding to the distance from the sensor OFF position to the transfer position is added to the count value to obtain the leading edge of the toner image transferred to the belt. Position. Similarly, the trailing edge position of the toner image transferred to the belt is obtained by adding the count value corresponding to the length of the toner to the leading edge position information of the toner image transferred to the belt.

  Specifically, the toner length is obtained from the difference between the sheet size calculated in step S901 and the exposure size exposed by the exposure control unit 210. Next to S906, the process proceeds to S907 to determine the cleaning end condition. This is the number of times the toner image is passed through the cleaner unit 218, which is determined by the toner density of the toner image transferred onto the transfer belt 234 and the size of the toner image.

  On the other hand, if the exposure has already been completed in S902, the process proceeds to S908, where the sheet size and the image size are compared. If the image size is larger, the process proceeds to S905, and if it is smaller, the control is terminated. The control in FIG. 9 is performed for each sheet when the sheet passes the registration sensor 257, whereby the position of the toner image transferred to the transfer belt 234 on the transfer belt is determined. As for the position on the transfer belt, data as shown in FIG. 11 is stored in a storage unit in the toner position determination unit 503. Reference numeral 1101 denotes the leading edge position of the toner image determined in S905. Reference numeral 1102 denotes the trailing edge position of the toner image determined in step S906. 1103 is the remaining number of times obtained by subtracting the number of times of passing the cleaner unit 218 from the number of times determined in S907.

  Next, the control of the conveyance timing control unit 502 in the fourth embodiment will be described using the flowchart of FIG. This flowchart is executed for each recording material immediately before the recording material reaches the registration sensor 257.

  First, in S1001, it waits for the registration sensor 257 to detect the leading edge of the recording material. When the leading edge of the recording material is detected, the process proceeds to S1002, and the count value of the timer 509 at the time when the registration sensor 257 detects the leading edge of the recording material is read, and the required count number from the registration sensor to the transfer position is added to the value. Calculate the position of the transfer belt on the transfer belt. Let Ps be the calculated position. Further, a value obtained by converting the sheet length into a count value is added to Ps, and the position of the rear end of the sheet on the transfer belt is calculated.

  Since the value of the timer 509 is initialized (reset to 0) at the timing when the transfer belt HP sensor 259 detects the transfer belt home position flag 258, the value of the timer 509 is set on the transfer belt with the home position as the origin. It means absolute position.

  In addition, the regione timing is calculated in the same manner as Pr. In step S1003, it is checked whether there is a toner image on the transfer belt 234. Specifically, it is determined whether or not data is registered in the storage unit described with reference to FIG. 11 and, if data is registered, whether or not all data has been evaluated in the flow after S1004.

  If there is no toner image, the process advances to step S1012 to control sheet conveyance at the registration-on timing Pr. If there is a toner image, the process proceeds to S1004, where the position of the toner tip on the transfer belt is read out and set to Ts. In step S1005, the position of the trailing edge of the toner on the transfer belt is read out and set as Tk.

  In step S1006, the position of the toner image and the position of the recording material are compared to determine whether they overlap. Whether or not the sheet overlaps can be determined by comparing the sheet leading edge position Ps and the toner image leading edge position Ts, and the sheet material trailing edge Pk and the toner image trailing edge Tk. The procedure for determining the overlap between the sheet material and the toner image is Ps <Ts (when the toner image leading edge position Ts is downstream in the conveying direction of the sheet material leading edge position Ps), the sheet material trailing edge position P is more than the toner image leading edge position Ts. If they are on the downstream side, overlap occurs. When Ps> Ts (the sheet material leading edge position Ps is downstream in the transport direction of the toner image leading edge position Ts), Ps <Tk (the toner image trailing edge position Tk is downstream in the transport direction of the sheet material leading edge position Ps). If there is, an overlap occurs.

  In step S1006, if they overlap, the process proceeds to step S1007, and the registration time Pr is changed so that the sheet material leading edge position Ps is downstream of the toner image trailing edge position Tk. The process advances to S1008 to update the sheet material leading edge position Ps and the sheet material trailing edge position P after changing the regione timing Pr, and the process advances to S1009.

  In S1009, data as shown in FIG. 11 is checked, and if there is still a toner image, the process returns to S1004. In step S1004, the toner front end position Ts of the next toner image is set. In step S1005, the next toner image rear end position Tk is set. In other words, a reion timing Pr that does not overlap with all the toner images existing on the transfer belt 234 can be determined by this control.

  If there is no next toner image in S1009, the process proceeds to S1010, where it is checked whether or not the reion timing Pr that does not overlap with all the toner images is obtained. If not, the process proceeds to S1011 and the toner image on the transfer belt 234 is obtained. Waits until at least one cleaning is completed, and then returns to S1004 and again executes a flow for determining a reion timing at which the toner image and the sheet material do not overlap. If it is determined in S1010 that the region timing Pr has been obtained, the process proceeds to S1012 and the conveyance control is performed at the region timing Pr.

  Next, the control of the flowchart described in FIG. 10 will be specifically described using an example of FIG.

  FIG. 12 is a diagram in which the transfer belt 234 is extended to form a straight line, and the left end is the origin (home position flag 258). A description will be given of a procedure for determining the timing of conveying the 400 sheet material with the length counted by the timer 509 when the toner images 1 to 5 of the data shown in FIG. 11 are transferred onto the transfer belt. . At this time, the leading edge arrival position Ts of the sheet material determined in step S1002 is 100, and the trailing edge arrival position Tk is 500.

  First, the data of the toner image 1 in FIG. 11 is read, and the toner image leading edge position Ts is 100 (S1004), and the toner image trailing edge position Tk is 500 (S1005). In this case, since the toner image 1 and the sheet material overlap each other, the registration timing Pr is changed in S1007. In S1008, the sheet material leading edge arrival position Ps becomes 200 after Tk, and the sheet material trailing edge Pk becomes 600. Since the next toner image is present in S1009, the process returns to S1004, and the next toner image 2 is read in S1004 and S1005.

  Since the toner image 2 overlaps with the new sheet material conveyance position (the leading edge position 200 and the trailing edge position 600), the reion timing Pr indicates that the leading edge position Ps of the sheet material is the trailing edge Tk (= 1000) of the toner image 2. ) (S1007). As a result, in S1008, the leading edge position Ps of the sheet material is 1000, and the trailing edge position Pk of the sheet material is 1400. In step S1009, the process further returns to step S1004, where the next toner image 3 is read, and the leading end position Ts (= 1500) of the toner image and the trailing end position Tk (= 1800) of the toner image are read. In step S1006, the sheet material does not overlap. Therefore, the process proceeds to step S1012, and the sheet material is conveyed at a region timing Pr at which the sheet material leading edge position Ts is 1000 and the sheet material trailing edge position Tk is 1400. Because of such control, even if there are a plurality of toner images on the transfer belt 234, the sheet material can be conveyed so as not to overlap the toner image.

1 is a cross-sectional view of an image forming apparatus. FIG. 6 is a diagram illustrating that a toner image is transferred to a transfer belt. 6 is a flowchart illustrating control of a sheet size determination unit and a toner position determination unit. FIG. 6 is a diagram illustrating a method for a toner position determination unit to determine a toner position. It is a control block diagram. It is a conveyance control diagram. It is a flowchart explaining control of a conveyance timing control part. It is a figure explaining the difference of the image forming apparatus of Embodiment 3 of this invention and the image forming apparatus of Embodiment 1. FIG. 10 is a flowchart illustrating control of a sheet size determination unit and a toner position determination unit according to Embodiment 4 of the present invention. It is a flowchart explaining control of the conveyance timing control part in Embodiment 4 of this invention. FIG. 10 is a diagram for explaining a toner position management method on a transfer belt according to a fourth embodiment of the present invention. FIG. 10 is a diagram illustrating an example of a state of a toner image transferred onto a transfer belt for specifically explaining control of a conveyance timing control unit according to a fourth embodiment of the present invention.

Explanation of symbols

100 Image Forming Apparatus Main Body 210 Exposure Control Unit 211 Photosensitive Drum 218 Transfer Belt Cleaner 233 Registration Roller 234 Transfer Belt 257 Registration Sensor 258 Home Position Flag 259 Home Position Sensor

Claims (5)

An image carrier on which a toner image is formed, a recording material carrier that carries and transports a recording material, and a surface of the recording material carrier after separating the recording material onto which the toner image has been transferred from the image carrier. Cleaning means for abutting and cleaning the surface of the recording material carrier, storage means for storing the recording material, a conveyance path for conveying the recording material stored in the storage means to the recording material carrier, The size detection means for detecting the size of the recording material arranged on the conveyance path, the comparison means for comparing the size of the recording material detected by the size detection means and the size of the toner image, and the comparison result of the comparison means A storage means for storing the position of the toner transferred onto the recording material carrier, a conveyance timing control means for controlling the timing of conveying the recording material from the conveyance path to the recording material carrier, An image forming apparatus comprising,
The image forming apparatus, wherein the conveyance timing control unit controls the toner image on the recording material carrier and the recording material on the recording material carrier so as not to overlap each other.   The conveyance timing control means includes a toner image on the recording material carrier and a recording material on the recording material carrier until the toner image on the recording material carrier is completely cleaned by the cleaning means. The image forming apparatus according to claim 1, wherein the image forming apparatuses are controlled so as not to overlap each other.   And measuring means for measuring the number of times that the toner image transferred onto the recording material carrier has passed through the cleaning means, wherein the conveyance timing control means is adapted to determine the conveyance timing according to the number of passages measured by the measurement means. The image forming apparatus according to claim 1, wherein the image forming apparatus is changed. An image carrier on which a toner image is formed, a recording material carrier that carries and transports a recording material, and a surface of the recording material carrier after separating the recording material onto which the toner image has been transferred from the image carrier. Cleaning means for abutting and cleaning the surface of the recording material carrier, storage means for storing the recording material, a conveyance path for conveying the recording material stored in the storage means to the recording material carrier, The size detection means for detecting the size of the recording material arranged on the conveyance path, the comparison means for comparing the size of the recording material detected by the size detection means and the size of the toner image, and the comparison result of the comparison means Based on the storage means for storing the position of the toner image transferred onto the recording material carrier, the density detection means for detecting the density of the toner image transferred on the recording material carrier, and the conveyance path. The record A transfer timing control means for controlling the timing for conveying the recording material to the bearing member, an image forming apparatus having a,
The conveyance timing control means prevents the toner image on the recording material carrier and the recording material on the recording material carrier from overlapping each other until the density detected by the density detection means reaches a predetermined value. An image forming apparatus that controls the image forming apparatus.   The transport timing control means includes a time when the leading end of the recording material reaches the transfer position and a time when the trailing end of the recording material reaches the transfer position when the recording material is transported to the recording material carrier at a normal transport timing. And the time when the leading edge of the toner image stored in the storage means reaches the transfer position is compared with the time when the trailing edge of the toner image reaches the transfer position. 5. The control according to claim 1, wherein when the toner image and the recording material are determined to overlap with each other on the recording material carrier, the conveyance timing is controlled so as not to overlap. Image forming apparatus.

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