JP2006251727A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly accurately and effectively control the contact and the separation timing of a transfer roller for transferring an image to transfer paper. <P>SOLUTION: An image forming apparatus comprises: a photoreceptor on which an electrophotographic latent image is formed; a developing unit for developing the image formed on the photoreceptor by a plurality of colors; an intermediate transfer body for transferring an image of the plurality of colors which is developed on the photoreceptor from the photoreceptor; a transfer roller for bringing transfer paper into contact with the intermediate transfer body to transfer the image from the intermediate transfer body to the transfer paper; and a means for separating the transfer roller from the intermediate transfer body when transfer to the transfer paper is not performed. The contact timing of the transfer roller in transferring the image from the intermediate transfer body to the transfer paper is controlled on the basis of a time elapsed from the active state of a final color writing signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus.

  In a color image forming apparatus that forms a color image, such as a color printer, an electrostatic latent image formed on a photoconductor is developed with B (black), Y (yellow), C (cyan), and M (magenta) colors. The developed image data of each color is superimposed on the color on the intermediate transfer member to form a color image, and then transferred to transfer paper. Such an image forming apparatus has a transfer roller for bringing the paper into contact with the intermediate transfer member, and the transfer roller performs transfer onto the transfer paper by bringing the transfer paper into contact with the intermediate transfer member. That is, when forming a color image, in order to perform color superposition on the intermediate transfer member, the transfer roller makes the transfer paper contact the intermediate transfer member only when transferring the transfer paper, and removes it at other times. There is a need.

In order to perform the timing of contact and separation of the transfer roller with respect to the intermediate transfer member, Patent Document 1 discloses that time measurement is started from the time when the transfer paper is fed, and the measured time reaches a specified time. It is described that control is performed so that the transfer roller is brought into contact with / separated from the intermediate transfer member at the time point.
JP 2000-75689 A

  In the control described in Patent Document 1, since the time until the roller is brought into contact / separated differs depending on the position of the tray to be fed, accurate time control cannot be performed. Further, this time is easily influenced by the transfer speed of the transfer paper. Furthermore, the length of the fed transfer paper may differ from the set value.For example, if the transfer paper is shorter than the set value, the transfer roller will continue to contact the intermediate transfer body even if the transfer paper passes by, The image on the intermediate transfer member adheres to the transfer roller, causing a problem of soiling the back surface of the transfer paper at the next transfer.

  The present invention has been made in consideration of such problems, and contact and separation of a transfer roller for transferring an image to a transfer sheet without using an elapsed time from the start of transfer sheet feeding. An object of the present invention is to provide an image forming apparatus capable of controlling the timing with high accuracy and good control.

  According to the first aspect of the present invention, there is provided a photosensitive member on which an electrostatic latent image is formed, a developing device for developing an image on the photosensitive member with a plurality of colors, and a plurality of colors developed on the photosensitive member. An intermediate transfer body for transferring from the body, a transfer roller for bringing the transfer paper into contact with the intermediate transfer body for transferring an image from the intermediate transfer body to the transfer paper, and an intermediate transfer of the transfer roller when the transfer to the transfer paper is not performed. A means for separating from the body, and controlling the transfer roller contact timing when the image is transferred from the intermediate transfer body to the transfer paper based on the elapsed time from the activation of the write signal of the final color. Features.

  According to a second aspect of the present invention, in the first aspect of the invention, the trailing edge of the transfer paper passes through the designated sensor according to the separation timing of the transfer roller from the intermediate transfer member after the image is transferred from the intermediate transfer member to the transfer paper. It is performed based on the elapsed time from.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the length of the transfer paper is measured by measuring the passing time of the designated sensor, and the measured length is sub-scanned on the intermediate transfer member. A warning is given when the direction is different.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the length of the transfer paper is different from the sub-scanning direction of the image generated on the intermediate transfer member. When image forming is continuously performed, if transfer paper is supplied from the same paper feed stage, whether or not to interrupt image forming is selected.

  The invention described in claim 5 is characterized in that, in the invention described in claim 4, there is provided display means for displaying a warning when the image forming is interrupted.

  A sixth aspect of the invention is characterized in that, in the fourth or fifth aspect of the invention, there is provided a non-volatile memory for storing the selection of whether or not to interrupt.

  According to the present invention, since the contact timing of the transfer roller when the image is transferred from the intermediate transfer member to the transfer paper is controlled based on the elapsed time from the activation of the write signal of the final color, The set value of the contact time of the transfer roller does not differ depending on the paper feed position, and there is no need to change the time associated with the change in paper feed control. For this reason, it is possible to satisfactorily control the contact and separation timing of the transfer roller for image transfer with high accuracy.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. 1 is an overall view of a color laser printer to which the present invention is applied, FIG. 2 is a block diagram for control, FIGS. 3 to 7 are flowcharts showing operations, and FIGS. 8 to 10 are front views showing examples of warning display. FIG.

  In the color laser printer 1, as shown in FIG. 1, the surface of the belt-like photosensitive member 2 that runs endlessly is uniformly charged by the charging member 3, and then the image information from the writing unit 4 is used. Exposure by scanning with a laser beam forms an electrostatic latent image. The electrostatic latent image is developed and visualized by the developing device 5 as the photosensitive member 2 travels.

  The developing device 5 includes a magenta developing device 5a, a cyan developing device 5b, a yellow developing device 5c, and a black developing device 5d. The photosensitive member 2 is developed by each of these developing devices, and the developed image is an intermediate transfer member. (Intermediate transfer belt) The toner images are sequentially transferred onto the intermediate transfer belt 6 and the colors are superimposed on the intermediate transfer body 6. That is, a developing voltage is applied by bringing the magenta developing device 5a into contact with the photosensitive member 2 to develop magenta toner (magenta image) on the photosensitive member 2, and a voltage is applied from the primary transfer brush 9 to the intermediate transfer member 6. Thus, the magenta image is primarily transferred to the intermediate transfer body 6. Next, the cyan developer 5 b is brought into contact with the photosensitive member 2 to develop cyan toner on the photosensitive member 2, and then a cyan image is primarily transferred to the intermediate transfer member 6. Thereafter, the primary transfer of the yellow image and the primary transfer of the black image are performed on the intermediate transfer body 6 in the same manner. By these operations, four color images are transferred to the intermediate transfer body 6.

  The transfer paper 7 is accumulated in a paper feed tray 8 and is conveyed to the intermediate transfer body 6 by a paper feed roller array. The transferred transfer paper 7 is brought into contact with the intermediate transfer body 6 by the transfer roller 10, and the color image of the intermediate transfer body 6 is transferred (secondary transfer) to the transfer paper 7 by this contact. After the transfer onto the transfer paper 7, the transfer roller 10 is released from the contact with the intermediate transfer body 6. This transfer roller 10 is provided with means 16 for making contact with and separating from the intermediate transfer member 6. On the transfer path of the transfer sheet 7, a sheet transfer sensor 11 that monitors the transfer sheet 7 being transferred to the intermediate transfer body 6 is disposed. The transfer paper 7 onto which the image has been transferred from the intermediate transfer body 6 is conveyed to the fixing unit 12 to fix the image.

  In FIG. 1, reference numeral 13 denotes a duplex unit for forming images on both sides of the transfer sheet 7, which operates to invert the transfer sheet 7 onto which the image has been transferred and supply it to the intermediate transfer member 6 again. Reference numeral 14 denotes a photosensitive member cleaning unit that removes toner from the photosensitive member 2, and reference numeral 15 denotes an intermediate transfer member cleaning unit that removes toner from the intermediate transfer member 6.

  In FIG. 2, the CPU 21 performs calculation and controls between other blocks. The writing unit 22 writes an image on the photosensitive member 2, receives and outputs a write signal output control command from the CPU 21, and notifies the CPU 21 of the ON / OFF state. The paper transport sensor 11 notifies the CPU 21 that the transfer paper 7 has passed.

  The operation unit 24 has a display panel and input buttons, receives a parameter setting command from the CPU 21, performs parameter setting, and notifies the CPU 21 of the set value. The memory 25 and the nonvolatile memory 26 store information, and the CPU 21 writes information and reads information. In particular, the nonvolatile memory 26 stores information (such as a machine type) that needs to be stored even when the power is turned off. The timer unit 27 is an interrupt process, and the CPU 21 is activated by setting a cycle and the like, and after the activation, an interrupt is generated at a fixed cycle to update the timer counter value.

  FIG. 3 is a flowchart showing control of a write signal during image formation in the present embodiment. When the power is turned on, first, in step S301, a print request is waited. When a print request is received, the process proceeds to step S302, in which the print conditions such as the image size (main scanning direction and sub-scanning direction) and the color to be developed received together with the print request are stored in the memory, and the process proceeds to step S303. In step S303, after the write signal is turned on, the process proceeds to step S304. In step S304, a timer for turning off the write signal is started, and the process proceeds to step S305. In step S305, it is determined whether the signal is the final color write signal. If it is the final color, the process proceeds to step S306. If it is not the final color, the process proceeds to step S307.

  In step S306, control is started to bring the secondary transfer roller (transfer roller) 10 that performs transfer onto the transfer paper 7 into contact with the intermediate transfer body 6, and the process proceeds to step S307. Step S306 controls contact with the secondary transfer roller 10, and operates according to the flowchart shown in FIG.

  In step S307, the timer activated in step S304 waits for time-up, and when time-up occurs, the process proceeds to step S308. In step S308, the write signal is turned OFF and the process proceeds to step S309. In step S309, it is determined whether the signal is the write signal for the final color. If the color is the final color, the process returns to step S301 to wait for a print request again. If not, the process returns to step S303 and the next color is written.

  FIG. 4 is a flowchart showing the transfer (secondary transfer) of the color image onto the transfer paper in step S306 of FIG. 3, and shows the control of the operation for bringing the activated secondary transfer roller 10 into contact with the intermediate transfer body 6. . In step S306 described above, when the control is activated, the process proceeds to step S401, the timer for bringing the secondary transfer roller 10 into contact with the intermediate transfer member 6 is activated, and the process proceeds to step S402. In step S402, the timer started in step S401 is waited for time-up, and when time is up, the process proceeds to step S403. In step S403, the secondary transfer roller 10 is brought into contact with the intermediate transfer member 6, and the process is terminated. By performing such control, the set value of the contact time of the secondary transfer roller 10 does not differ depending on the paper feed position of the transfer paper 7, and it is not necessary to change the time associated with the change in paper feed control. . For this reason, the contact and separation timing of the secondary transfer roller 10 for image transfer can be well controlled with high accuracy.

  FIG. 5 is a flowchart showing the control when the transfer paper 7 is fed and passes through the paper transport sensor 11. When the transfer paper 7 is fed from the paper feed tray 8, this control is activated.

  In FIG. 5, in step S501, the process waits for the leading edge of the transfer paper 7 to pass the paper transport sensor 11, and if it is detected that the leading edge of the transfer paper 7 has passed the paper transport sensor 11, the process proceeds to step S502. . In step S502, a timer for measuring the length of the transfer paper 7 in the sub-scanning direction is started, and the process proceeds to step S503.

  In step S503, the process waits for the rear end of the transfer paper 7 to pass the paper transport sensor 11, and if it is detected that the rear end of the transfer paper 7 has passed the sensor 11, the process proceeds to step S504. In step S504, the timer started in step S502 for measuring the length of the transfer sheet 7 in the sub-scanning direction is stopped, and the process proceeds to step S505. In step S505, control for detaching the secondary transfer roller 10 that performs transfer onto the transfer paper from the intermediate transfer member 6 is activated, and the process proceeds to step S506.

  Step S505 controls the separation of the secondary transfer roller 10 from the intermediate transfer member 6, and operates according to the flowchart shown in FIG.

  In step S506 in FIG. 5, the value when the measurement timer is stopped is read to measure the length of the transfer paper 7 in the sub-scanning direction, and the process proceeds to step S507. In step S507, the transfer paper 7 obtained from the sub-scanning direction length of the write signal of the printing condition stored in step S302 and the timer value read in step S506 after receiving the print request in the flowchart of FIG. Are compared with the length in the sub-scanning direction. As a result of comparison, if the lengths are different, the process proceeds to step S508, and if the lengths are the same, the process proceeds to step S509.

  When the length of the transfer signal in the sub-scanning direction is different from that of the transfer sheet 7, a warning is displayed on the operation panel as shown in step S508, and the process proceeds to step S509. FIG. 8 shows an example of warning displayed on the operation panel. By giving a warning in this way, it is possible to notify the operator of a transfer sheet selection error.

  In step S509, it is stored whether the measured transfer sheet length and writing length match or do not match, and the process ends.

  FIG. 6 is a flowchart showing the control of the operation for detaching the activated secondary transfer roller 10 from the intermediate transfer member 6 in the processing step S505 in FIG. In step S601 where the control is started, a timer for causing the secondary transfer roller 10 to be detached from the intermediate transfer member 6 is started, and the process proceeds to step S602. In step S602, the process waits for the timer started in step S601 to expire, and proceeds to step S603 if the timer expires. In step S603, the secondary transfer roller 10 is detached from the intermediate transfer member 6, and the process is terminated. In such control, the secondary transfer roller 10 is separated from the intermediate transfer member 6 based on the elapsed time from the passage of the rear end of the transfer paper 7 through the paper transport sensor 11. When the sub-scanning length is different, the secondary transfer roller 10 can be prevented from being stained.

  FIG. 7 is a flowchart showing control until image formation is started by receiving a print request. When the power is turned on, first, in step S701, a print request is waited. When the print request is received, the process proceeds to step S702. In step S702, it is determined whether or not printing is performed for the second and subsequent sheets during continuous printing. If the second and subsequent sheets are continuously printed, the process proceeds to step S703. If it is not the second and subsequent sheets of continuous printing, the process proceeds to image forming processing in step S706.

  In step S703, which has proceeded to the case of the second and subsequent sheets of continuous printing, the state of matching / mismatching of the writing length with the measured transfer paper 7 stored in the previous printing stored in step S509 in the flowchart of FIG. If YES in step S704, the flow advances to step S704. If they match, the flow advances to image formation processing in step S706.

  In step S704, which proceeds when the measured transfer sheet and writing length do not match, it is determined whether or not the image sub-operation direction length and the paper feed stage in the current printing conditions are the same as those in the previous case. Proceeds to step S705, and if not, the process proceeds to image forming processing in step S706.

  In step S705, which proceeds when the image sub-operation direction length and the paper feed stage in the current printing conditions are the same as the previous one, whether or not to continue printing in such a case is set in advance from the operation panel and is nonvolatile. The value stored in the memory is read, and the process proceeds to step S706. FIG. 9 shows a setting screen on the operation panel in this case. In such a process, when the next image is continuously formed in a state where the length of the transfer sheet 7 is different from the sub-scanning direction of the image generated on the intermediate transfer body 6, the transfer sheet 7 is supplied with the same paper feed. In the case of being supplied from the stage, it is possible to select whether or not the image formation is interrupted, so that it is possible to intentionally perform image formation with different sub-scan sizes, and to eliminate waste of the transfer sheet 7. be able to.

  In step S706, the contents of the set value of the nonvolatile memory read in step S705 are determined. If the result is printing, the process proceeds to the image forming process in step S706. When the image forming process is completed, the process returns to step S701 to generate again. Wait for the image request. On the other hand, if the set value of the non-volatile memory is print stop, the process proceeds to step S708. In step S708, a warning as shown in FIG. 10 is displayed on the operation panel, and the process returns to step S701 to wait for an image formation request again. The reason for the interruption can be known by performing the display as shown in FIG.

1 is an overall structural diagram of a color laser printer to which an embodiment of the present invention is applied. It is a block diagram for performing control. 5 is a flowchart illustrating image formation control. It is a flowchart which shows the control which makes a transfer roller contact an intermediate transfer body. It is a flowchart which shows the control accompanying feeding of a transfer paper. 4 is a flowchart showing control for separating a transfer roller from an intermediate transfer member. It is a flowchart which shows the control which starts image formation. It is a front view of the operation panel which shows a warning. It is a front view of the operation panel which shows selection. It is a front view of the operation panel which shows a warning.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Color laser printer 2 Photoconductor 6 Intermediate transfer body 7 Transfer paper 10 Transfer roller 11 Paper conveyance sensor

Claims (6)

  A photosensitive member on which an electrostatic latent image is formed, a developing unit that develops an image on the photosensitive member with a plurality of colors, an intermediate transfer member that transfers a plurality of colors developed on the photosensitive member from the photosensitive member, and A transfer roller for bringing the transfer paper into contact with the intermediate transfer member in order to transfer an image from the intermediate transfer member to the transfer paper, and means for separating the transfer roller from the intermediate transfer member when the transfer to the transfer paper is not performed. An image forming apparatus, wherein the contact timing of the transfer roller when the image is transferred from the intermediate transfer member to the transfer sheet is controlled based on the elapsed time from the activation of the final color write signal.   2. The timing of detachment of the transfer roller from the intermediate transfer body after the image is transferred from the intermediate transfer body to the transfer paper is performed based on the elapsed time from the passage of the designated sensor at the trailing edge of the transfer paper. The image forming apparatus described.   The length of the transfer paper is measured by measuring the passing time of the designated sensor, and a warning is given when the measured length is different from the sub-scanning direction of the image generated on the intermediate transfer member. The image forming apparatus described.   If the transfer paper is supplied from the same paper feed stage when the next image is continuously formed with the transfer paper length being different from the sub-scanning direction of the image generated on the intermediate transfer body, the image is formed. 4. The image forming apparatus according to claim 1, wherein whether or not to interrupt is selected. 5.   5. The image forming apparatus according to claim 4, further comprising display means for displaying a warning when the image formation is interrupted.   6. The image forming apparatus according to claim 4, further comprising a non-volatile memory that stores a selection as to whether to interrupt.

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