JP2009186900A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly transfer an image by performing primary transfer of a succeeding image during secondary transfer of the first image while evading jitter due to rush of a sheet into a secondary transfer device. <P>SOLUTION: When a tip of a sheet is carried into a space between an intermediate transfer belt and the secondary transfer device at time t0, the speed of the intermediate transfer belt is reduced due to the influence of sheet rush, but the variation of the speed is gradually reduced while continuing vibration, the speed of the intermediate transfer belt is stabilized at a speed held before sheet carry-in at time t1 after fixed time T1. On the contrary, when the sheet is carried out from the space between the intermediate transfer belt and the secondary transfer device at time t2, the speed is increased due to the influence of the carry-out, but the speed is also stabilized at a speed held before carrying out the sheet at time t3 after fixed time T3. In time T2 between the time t1 and t2, the intermediate transfer belt is rotated at a stabilized speed. In this invention, transfer is controlled so that even during secondary transfer operation, primary transfer can be performed in the time T2 that the intermediate transfer belt is rotated at the stabilized speed. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus and an image forming method, and in particular, performs primary transfer of a next image when the speed of an intermediate transfer belt during paper feeding to a secondary transfer unit is not fluctuating. The present invention relates to an image forming apparatus and an image forming method.

  Generally, an intermediate transfer type image forming apparatus according to the prior art applies an external force to the intermediate transfer belt when the paper enters the secondary transfer unit, because the leading edge of the paper contacts the intermediate transfer belt. This causes a phenomenon that the speed of the belt fluctuates temporarily. For this reason, a difference in surface speed occurs between the intermediate transfer belt and the photosensitive member. Similarly, at the moment when the paper is carried out from the secondary transfer unit, the external force applied to the intermediate transfer belt is reduced, so that a temporary speed fluctuation of the intermediate transfer belt occurs. When the speed of the intermediate transfer belt fluctuates, if the image forming apparatus performs a primary transfer operation for transferring an image from the photosensitive member to the intermediate transfer belt, the image is stretched and contracted to cause image unevenness (shock jitter). ) Will occur.

  As a conventional technique for solving the above-described problem, for example, a technique described in Patent Document 1 is known. In this conventional image forming apparatus, primary transfer and secondary transfer are alternately performed without performing primary transfer during a secondary transfer operation in which an image is transferred from an intermediate transfer belt to paper.

  FIG. 7 is a flowchart for controlling the operation order of the primary transfer and the secondary transfer in the image forming apparatus according to the prior art. The operations of the primary transfer and the secondary transfer according to the prior art will be described with reference to FIG.

(1) After the image is formed on the photoconductor, the image forming apparatus starts a primary transfer operation for transferring the image from the photoconductor to the intermediate transfer belt, and ends the primary transfer (steps 701 and 702).

(2) After the completion of the primary transfer, the image forming apparatus starts a secondary transfer operation for transferring an image from the intermediate transfer belt to the paper, and ends the secondary transfer (steps 703 and 704).

(3) Thereafter, the image forming apparatus determines whether or not there is a job in which the next image is formed on the photosensitive member, that is, whether or not it is a job end. If it is a job end, the process ends here. If there is a next job, the process returns from step 701 to start the primary transfer operation for the next image (step 705).

As can be seen from the operation described above, the image forming apparatus according to the prior art rotates the intermediate transfer belt twice until the image is transferred onto the paper in order to perform the primary transfer and the secondary transfer in order. Will be.
JP 2002-278212 A

  However, since the image forming apparatus according to the related art described above does not perform the primary transfer during the secondary transfer operation, the intermediate transfer belt is rotated twice in order to perform the primary transfer and the secondary transfer. Therefore, there is a problem that the transfer speed is lowered.

  An object of the present invention is to provide an image forming apparatus and an image forming method that solve the above-described problems of the prior art and prevent a shock jitter and do not reduce the transfer speed.

  In order to achieve the above object, the first means of the present invention develops the latent image written on the photosensitive member as a toner image, transfers the toner image to an intermediate transfer member, and the intermediate transfer member and the secondary transfer member. An image forming apparatus for transferring the toner image to a recording sheet with a transfer apparatus, wherein the recording sheet onto which the first image developed on the photosensitive member is transferred is the intermediate transfer body and the secondary transfer apparatus. The first time excluding the speed fluctuation time of the intermediate transfer member that occurs when the recording sheet is carried between the intermediate transfer member and the secondary transfer device. First time calculating means for calculating time, and transfer of the toner image from the photosensitive member to the intermediate transfer member of the second image developed on the photosensitive member after the first image is performed. The second time required for transferring the region to the intermediate transfer member is shorter than the first time. Case, the first to perform the transfer to the intermediate transfer body time to the second image, characterized by comprising a write control means for controlling writing to the photosensitive member.

  According to a second means of the present invention, in the first means, the first time calculating means sets the first time as the primary transferable time based on the shape of the paper and the speed of the intermediate transfer member. It is characterized by calculating.

  According to a third means of the present invention, in the first means, the speed of the intermediate transfer member can be set according to the type of recording paper, and a paper type detecting means for detecting the paper type is provided. And the first time calculating means calculates the first time as a primary transferable time from a detection result by the paper type detecting means.

  According to a fourth means of the present invention, in the first means, the writing control means performs intermediate transfer of an area where the toner image is transferred from the photosensitive member to the intermediate transfer member of the second image. Second time calculating means for calculating a second time required for transfer to the body as a next image primary transfer time, the second time calculating means including the range of the image forming area of the formed image and the intermediate time The primary transfer time of the next image is calculated based on the speed of the transfer body.

  According to a fifth means of the present invention, in the first means, the writing control means is a toner image from the photoconductor to the intermediate transfer member of the second image that is then developed on the photoconductor. Transfer of the second image to the intermediate transfer member during the first time when the second time required for transfer to the intermediate transfer member in the region where the transfer of the second image is performed is shorter than the first time. The primary transfer instruction is performed.

  According to a sixth means of the present invention, in the first means, the writing control means is a toner image from the photosensitive member to the intermediate transfer member of the second image that is then developed on the photosensitive member. When the second time required for the transfer to the intermediate transfer member in the region where the transfer is performed is longer than the first time, the primary transfer of the next image is performed after the secondary transfer operation is completed. The timing of writing to the photosensitive member is instructed.

  According to a seventh means of the present invention, in any one of the first to sixth means, a speed fluctuation storage means for measuring and storing a speed fluctuation time of the intermediate transfer member by the recording paper is provided. The speed variation time of the recording sheet having the longest speed variation time among the usable recording sheets is stored.

  According to an eighth means of the present invention, in any one of the first to sixth means, there is provided a speed fluctuation storage means for measuring and storing a speed fluctuation time of the intermediate transfer member by the recording paper. The speed variation time of the intermediate transfer member when the secondary transfer is performed on the first recording sheet is stored.

  According to a ninth means of the present invention, in the eighth means, the speed fluctuation time is re-measured when the image is secondarily transferred to the first recording paper after the power supply to the apparatus is turned on or the paper feeding section is inserted. It is characterized by being.

  The tenth means of the present invention develops the latent image written on the photosensitive member as a toner image, transfers the toner image to an intermediate transfer member, and between the intermediate transfer member and the secondary transfer device. In the image forming method of transferring the toner image to a recording paper, the recording paper on which the first image developed on the photosensitive member is transferred passes between the intermediate transfer member and the secondary transfer device. A first time excluding a speed fluctuation time of the intermediate transfer member that occurs when the recording sheet is carried between the intermediate transfer member and the secondary transfer device, A second image is transferred to the intermediate transfer member in a region where the toner image is transferred from the photosensitive member to the intermediate transfer member of the second image developed on the photosensitive member after the first image. When the second image is shorter than the first time, the second image is displayed at the first time. To perform the transfer to the intermediate transfer member, and controlling writing to the photosensitive member.

  According to the present invention, during the period in which the speed of the intermediate transfer belt is fluctuating due to secondary transfer, the secondary transfer operation in which the speed of the intermediate transfer belt is not fluctuated so that the primary transfer operation of the next image is not performed. Since the primary transfer operation of the next image can be performed, shock jitter can be prevented and a high-speed transfer operation can be performed.

  Embodiments of an image forming apparatus and an image forming apparatus according to the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a perspective view showing configurations of a photoconductor, an intermediate transfer belt, and a secondary transfer device in an image forming apparatus according to an embodiment of the present invention.

  The image forming apparatus shown in FIG. 1 is an image forming apparatus that forms a color image, and a photoreceptor on which single color toner images of yellow (Y), cyan (C), magenta (M), and black (K) are formed. 1-4, the intermediate transfer belt 13 on which each single color toner image formed on each photoconductor is superimposed and transferred as a full color composite color image, and the full color composite color image transferred onto the intermediate transfer belt 13 And a secondary transfer device 16 for transferring the image onto the recording paper. The photosensitive members 1 to 4 are connected to motors 9 to 12 having encoders 5 to 8 to be controlled in rotation, and the intermediate transfer belt 13 has an encoder 14 connected to an intermediate transfer belt driving roller 17 (not shown). The rotation is controlled by a motor.

  In the above description, when the start key of the image forming apparatus is pressed, the image forming apparatus starts the rotation of the intermediate transfer belt 13, and at the same time, each of the photoconductors 1 to 4 starts to rotate. A latent image is written on the surface, the latent image is developed as a toner image, and an operation for forming Y, C, M, and K single-color toner images is started. Then, the toner images of the respective colors formed on the respective photoreceptors are superposed on the intermediate transfer belt 13 that rotates in the clockwise direction and sequentially transferred to perform the primary transfer. A full-color composite color image is formed.

  On the other hand, when the start key is pressed, the paper is fed out from a selected paper feed tray or manual feed tray (not shown), and the fed paper passes through the conveyance path and hits the registration roller 15 shown in FIG. Stop temporarily. Thereafter, the registration roller 15 is controlled to rotate at an accurate timing in accordance with the composite color image on the intermediate transfer belt 13 and starts rotating, and the temporarily stopped paper is transferred to the intermediate transfer belt 13 and the secondary transfer device 16. The secondary transfer device 16 performs secondary transfer, and a color image is transferred onto the recording paper.

  During the transfer operation described above, the speed of the intermediate transfer belt 13 is always detected by the encoder 14, and the speeds of the photoreceptors 1 to 4 are also detected by the encoders 5 to 8. Are controlled to be equal.

  As described in the section of the prior art, since an external force is applied to the intermediate transfer belt 13 at the moment when the leading edge of the sheet is carried between the intermediate transfer belt 13 and the secondary transfer device 16, The speed varies, and a difference occurs between the intermediate transfer belt 13 and the surface speed of the photoreceptors 1 to 4. Similarly, since the external force applied to the intermediate transfer belt is lost at the moment when the trailing edge of the sheet is carried out between the intermediate transfer belt 13 and the secondary transfer device 16, the speed of the intermediate transfer belt 13 fluctuates temporarily. Occurs. At this time, if the image forming apparatus performs the above-described primary transfer operation, a shift called a jitter occurs in the image formed on the intermediate transfer belt 13, and the image is finally transferred onto the second-transferred sheet. Color misregistration will occur.

  FIG. 2 is a diagram for explaining the relationship between the sheet position and the speed fluctuation of the intermediate transfer belt.

  As shown in FIG. 2, when the leading edge of the paper is carried between the intermediate transfer belt 13 and the secondary transfer device 16 at time t0, the speed of the intermediate transfer belt 13 decreases due to the influence of paper entry. However, as described above, since the speed of the intermediate transfer belt 13 is controlled to be kept constant, the fluctuation of the speed of the intermediate transfer belt 13 gradually decreases while vibrating, and the constant time T1. At a later time t1, the speed is stabilized at the speed before carrying in the paper. On the contrary, when the sheet is carried out between the intermediate transfer belt 13 and the secondary transfer device 16 at time t2, the speed increases due to the influence. However, in this case as well, for the same reason as described above, at the time t3 after the predetermined time T3, the speed is stabilized at the speed before carrying out the paper. At time T2 between times t1 and t2, the intermediate transfer belt 13 is rotated at a stable speed.

  As can be seen from the description of FIG. 2, the primary transfer is performed during the time T2 during which the intermediate transfer belt 13 is rotated at a stable speed even during the sheet passing to the secondary transfer portion. By doing so, it is possible to avoid jitter due to paper entry. That is, unlike the prior art, it is not necessary to perform primary transfer and secondary transfer alternately, and primary transfer is not performed only for a certain period of time T1 and T3 during which the speed of the intermediate transfer belt varies. By using the sequence, it is possible to avoid jitter due to paper entry.

  For the processing as described above, the embodiment of the present invention includes a controller (not shown) that is also provided in a normal image forming apparatus for controlling the mechanism shown in FIG. In addition, a primary transferable time calculation unit for obtaining the above-described time T2 during which no speed fluctuation occurs during paper passing to the secondary transfer unit, and a primary transfer time calculation unit for calculating the primary transfer time of the next image As a result of these calculations, a start signal is generated to start writing on the photoconductor so that the primary transfer of the next image is started at a time when the speed fluctuation during the paper passing to the secondary transfer portion does not occur. Part.

  In the embodiment of the present invention, the above-described time T2 during which no speed fluctuation occurs during the passage of paper to the secondary transfer unit is calculated by the primary transferable time calculation unit, and at the same time, the primary image for the next image is also calculated. The transfer time calculation unit calculates a primary transfer time T4 as a primary transfer operation pattern of an image to be subjected to primary transfer and secondary transfer (referred to as a second image) next, and then a write start signal generation unit Thus, a writing start signal to the photosensitive member is generated based on the calculation results of T1 to T4, and writing or primary transfer operation is executed.

  FIG. 3 is a flowchart for explaining the calculation operation in the primary transferable time calculation unit. Next, this will be described.

(1) When power is supplied to the apparatus, the primary transferable time calculating unit detects the size of the recording paper contained in each paper feed tray. In the example shown in FIG. 3, it is assumed that there are three paper feed trays, but there may be any number of paper feed trays (steps 301 to 303).

(2) Next, the time for performing the secondary transfer on the recording paper (time T1 + T2 described with reference to FIG. 2) is obtained. Usually, the speed of the intermediate transfer belt (process linear speed) at the time of secondary transfer is model-specific. Therefore, by dividing the detected paper size length by the process linear speed, The transfer time (time T1 + T2 described with reference to FIG. 2) can be obtained (steps 304 to 306).

(3) From the obtained time T1 + T2, the speed after the leading edge of the paper described with reference to FIG. 2 is carried between the intermediate transfer belt 13 and the secondary transfer device 16 is constant until the original speed is stabilized. By subtracting the time T1, a time T2 at which no speed fluctuation occurs during the secondary transfer is obtained. The time T1 at this time is a value in which the speed fluctuation value of the paper having the largest speed fluctuation of the intermediate transfer belt among the papers usable in the image forming apparatus is stored in advance (steps 307 to 309).

(4) Thereafter, the obtained time T2 is stored in the memory for each paper feed tray, and the processing in the primary transferable time calculating unit is terminated (steps 310 to 312).

  In the above-described processing, when the image forming apparatus has a mode (thick paper mode) in which the process linear speed is changed and set according to the paper thickness, the image forming apparatus includes the paper size of each paper feed tray. A means for detecting the thickness is provided, and the time T1 + T2 can be obtained by dividing the length of the detected paper size by the process linear velocity set corresponding to the thickness of the paper. The above-described calculation process is performed when the apparatus is turned on or when a paper feed tray is inserted.

  FIG. 4 is a flowchart for explaining the calculation operation for calculating the primary transfer time for the next image (second image) in the primary transfer time calculation unit, and FIG. 5 is a diagram showing an example of the second image. These will be described below.

(1) Now, assuming that the second image has an image only in a part of the entire sheet in the sub-scanning direction as in the example shown in FIG. 5, the area where the primary transfer is to be performed is sub-scanning. There are only L regions in the direction. Therefore, the primary transfer time calculation unit detects the length of the region L, that is, the length in the sub-scanning direction, and divides the detected length of the second image in the sub-scanning direction by the process linear velocity. The primary transfer operation pattern T4 of the second image (the time required for the primary transfer operation of the second image) is obtained. In the case of a monochrome image, this division result is T4. In the case of a color image, since primary transfer is performed by four photoconductors, T4 is obtained by dividing (the length of the second image in the sub-scanning direction + the distance between the photoconductors) by the process linear velocity ( Step 401).

(2) The time T4 required for the primary transfer operation of the second image, which is the primary transfer operation pattern T4 of the second image obtained in the above-described process, is stored in the memory, and the process in the primary transfer time calculation unit is performed. The process ends (step 402).

  FIG. 6 is a flowchart for explaining the processing operation for generating the write start signal in the write start signal generating unit. Next, this will be described.

(1) When the image forming apparatus starts an image forming operation, first, the first image is written on the photoconductor to perform transfer (primary transfer) from each item to the intermediate transfer belt (step 601). ).

(2) Next, it is determined whether or not there is a job end, that is, whether or not there is an image to be transferred next. The secondary transfer for transferring the image transferred on the paper to the paper is started, and the secondary transfer operation is finished (steps 603 and 604).

(3) If it is determined in step 603 that there is a second image to be transferred next instead of a job end, the process of FIG. 4 is performed to calculate a time T4 required for the primary transfer operation of the secondary image. The time T2 during which the speed fluctuation does not occur during the secondary transfer calculated in the process of FIG. 3 is compared with the time T4 required for the primary transfer operation of the second image, and whether or not the time T2 is greater than the time T4 is determined. Determination is made (step 606).

(4) If it is determined in step 606 that the time T2 is greater than the time T4, the writing start signal generation unit determines that the primary transfer of the second image is possible during the secondary transfer operation, and at time T2. Writing of the second image to the photosensitive member is started at the timing of primary transfer of the second image (steps 607 and 608).

(5) After the start of the secondary transfer in step 607, after the start of passing the paper to the secondary transfer portion, after the leading edge of the paper is carried between the intermediate transfer belt 13 and the secondary transfer device 16 After the lapse of a certain time T1 until the speed is stabilized at the original speed, the primary transfer of the second image is started (step 609).

(6) After that, the writing start signal generator waits for the end of the secondary transfer, and after the end of the secondary transfer, returns to the process from step 603 and repeats the process (step 610).

(7) If it is determined in step 606 that the time T2 is not greater than the time T4, the writing start signal generation unit determines that the primary transfer of the second image is impossible during the sheet passing to the secondary transfer unit. After the processing in steps 601 and 602, the secondary transfer is performed as it is, and then the operation is terminated. The processing returns to step 601 and the processing is repeated (steps 611 and 612).

  The processing by the primary transferable time calculation unit, the primary transfer time calculation unit, and the write start signal generation unit in the embodiment of the present invention described above is configured by a program and executed by a CPU provided in the controller. These programs can be provided by being stored in a recording medium such as FD, CDROM, or DVD, and can be provided by digital information via a network.

  In the above-described embodiment of the present invention, the second image is described as an image that is subjected to primary transfer next. However, when the paper size is small, the next image may be displayed. In this case, after calculating T4 in the process of step 606 described with reference to FIG. 6, it is determined whether or not there is a sheet that comes to the secondary transfer portion during the primary transfer of T4. If it is not present (if it is the second sheet), the writing start signal is output as it is, and primary transfer for writing on the photosensitive member is performed. If there is, the time T2 corresponding to the paper size is read from the memory, and it is determined whether or not the time T2 is greater than the time T4. After that, depending on the result of the determination, processing similar to that after step 607 or after step 611 is performed.

FIG. 2 is a perspective view illustrating a configuration of a photoconductor, an intermediate transfer belt, and a secondary transfer device in an image forming apparatus according to an embodiment of the present invention. FIG. 6 is a diagram illustrating a relationship between a sheet position and a speed variation of an intermediate transfer belt. It is a flowchart explaining the calculation operation | movement in a primary transferable time calculating part. It is a flowchart explaining the calculation operation | movement which calculates the primary transfer time about the next image (2nd image) in a primary transfer time calculating part. It is a figure which shows the example of a 2nd image. It is a flowchart explaining the processing operation | movement which produces | generates the write-in start signal in a write-in start signal generation part. 10 is a flowchart for controlling control of the operation sequence of primary transfer and secondary transfer in an image forming apparatus according to a conventional technique.

Explanation of symbols

1-4 Photosensitive member 5-8, 14 Encoder 9-12 Motor 13 Intermediate transfer belt 15 Registration roller 16 Secondary transfer device 17 Intermediate transfer belt driving roller

Claims (10)

The latent image written on the photosensitive member is developed as a toner image, the toner image is transferred to an intermediate transfer member, and the toner image is transferred to a recording sheet between the intermediate transfer member and a secondary transfer device. A forming device,
Of the time during which the recording paper on which the first image developed on the photoconductor is transferred is passed between the intermediate transfer body and the secondary transfer device, the recording paper is the intermediate transfer body and 2. First time calculating means for calculating a first time excluding the speed fluctuation time of the intermediate transfer member that occurs when being carried into the next transfer device;
A second image is transferred to the intermediate transfer member in a region where the toner image is transferred from the photosensitive member to the intermediate transfer member of the second image developed on the photosensitive member after the first image. Write control means for controlling writing to the photoconductor so that the second image is transferred to the intermediate transfer body at the first time when the time is shorter than the first time. An image forming apparatus comprising: The image forming apparatus according to claim 1.
The image forming apparatus according to claim 1, wherein the first time calculating means calculates the first time as a primary transferable time based on a sheet shape and the speed of the intermediate transfer member. The image forming apparatus according to claim 1.
It is possible to set the speed of the intermediate transfer body according to the type of recording paper, and has a paper type detecting means for detecting the paper type,
The image forming apparatus according to claim 1, wherein the first time calculation unit calculates the first time as a primary transferable time from a detection result by the paper type detection unit. The image forming apparatus according to claim 1.
The writing control means sets a second time required for transferring the second image to the intermediate transfer member in an area where the toner image is transferred from the photosensitive member to the intermediate transfer member. A second time calculating means for calculating the transfer time;
The second time calculating means calculates the primary transfer time of the next image based on the range of the image forming area of the formed image and the speed of the intermediate transfer member. The image forming apparatus according to claim 1.
The writing control unit is configured to transfer a second image developed on the photosensitive member to the intermediate transfer member in a region where the toner image is transferred from the photosensitive member to the intermediate transfer member. When the image forming time is shorter than the first time, an instruction of primary transfer for performing transfer of the second image to the intermediate transfer member is performed within the first time. apparatus. The image forming apparatus according to claim 1.
The writing control unit is configured to transfer a second image developed on the photosensitive member to the intermediate transfer member in a region where the toner image is transferred from the photosensitive member to the intermediate transfer member. If the time is longer than the first time, the timing of writing to the photoconductor is instructed so that the primary transfer of the next image is performed after the end of the secondary transfer operation. apparatus. The image forming apparatus according to any one of claims 1 to 6,
A speed fluctuation storage means for measuring and storing a speed fluctuation time of the intermediate transfer member by the recording paper;
An image forming apparatus for storing a speed fluctuation time of a recording paper having the longest speed fluctuation time among usable recording papers. The image forming apparatus according to any one of claims 1 to 6,
A speed fluctuation storage means for measuring and storing a speed fluctuation time of the intermediate transfer member by the recording paper;
An image forming apparatus for storing a speed fluctuation time of the intermediate transfer member when secondary transfer is performed on a first recording sheet. The image forming apparatus according to claim 8.
2. The image forming apparatus according to claim 1, wherein the speed fluctuation time is re-measured when the image is secondarily transferred to the first recording sheet after the power supply to the apparatus is turned on or the sheet feeding unit is inserted. The latent image written on the photosensitive member is developed as a toner image, the toner image is transferred to an intermediate transfer member, and the toner image is transferred to a recording sheet between the intermediate transfer member and a secondary transfer device. A forming method comprising:
Of the time during which the recording paper on which the first image developed on the photoconductor is transferred is passed between the intermediate transfer body and the secondary transfer device, the recording paper is the intermediate transfer body and 2. Calculating a first time excluding the speed fluctuation time of the intermediate transfer member that occurs when being carried into the next transfer device;
A second image is transferred to the intermediate transfer member in a region where the toner image is transferred from the photosensitive member to the intermediate transfer member of the second image developed on the photosensitive member after the first image. And writing to the photosensitive member is controlled so that the transfer of the second image to the intermediate transfer member is performed at the first time when the time is shorter than the first time. An image forming method.