JP2012053390A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which can reduce labor required for releasing jamming of a medium and cleaning time of secondary transfer means even if there occurs a situation such as lagging of time when the recording medium reaches a secondary transfer point because the jamming of the medium or the like happens.SOLUTION: The image forming device comprises: image forming means; a transfer part for transferring a developer image formed by the image forming means to a medium; a member to be transferred for conveying the developer image; a medium conveyance part for conveying the medium; a medium detection part for detecting whether the conveyed medium has reached a predetermined arrival position or not; and a control part which temporarily stops driving of the member to be transferred and forming of the developer image by the image forming means when the medium detection part does not detect an arrival of the medium at the predetermined arrival position, and when the medium detection part detects the arrival of the medium at the predetermined arrival position within predetermined time after the stopping, synchronizes a position of the developer image and a position of the medium and makes the transfer part transfer the developer image to the medium.

Description

  The present invention relates to an intermediate transfer type image forming apparatus.

  Conventionally, in an image forming apparatus that performs color printing or monochrome printing, there has been an image forming apparatus that employs an intermediate transfer method using an intermediate transfer belt as an image forming method.

  In the intermediate transfer method, the developer image formed in the image forming unit is temporarily transferred to the intermediate transfer belt (primary transfer), and then the developer image on the intermediate transfer belt is transferred to the recording medium (secondary transfer). This is a technique for obtaining a printed image by transferring (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2008-077628

  However, in an image forming apparatus having a conventional configuration, after image formation using a developer is started, a situation occurs in which the time for the recording medium to reach the secondary transfer point is delayed due to a medium jam or the like. The developer image formed in advance has soiled the secondary transfer means, causing back-stained printing.

  The present invention has been made in view of such circumstances, and the problem of the present invention is that even when a situation such as a medium clogging or the like occurs and the time for the recording medium to reach the secondary transfer point is delayed occurs. It is another object of the present invention to provide an image forming apparatus capable of shortening the time and labor required for releasing a medium jam and the cleaning time of a secondary transfer unit.

  In order to solve the above problems, an image forming apparatus according to the present invention includes an image forming unit that forms a developer image using a developer, and a transfer unit that transfers the developer image formed by the image forming unit to a medium. A transfer member that conveys the developer image to the transfer unit, a medium conveyance unit that conveys the medium stored in the medium storage unit to the transfer unit, and the medium conveyed by the medium conveyance unit reaches a predetermined arrival position. If the medium detection unit that detects whether or not the medium has been detected and the medium detection unit does not detect the arrival of the medium at a predetermined arrival position, the drive of the transfer member and the formation of the developer image by the image forming unit are temporarily stopped. In addition, when the medium detection unit detects the arrival of the medium at a predetermined arrival position within a predetermined time after the stop, the position of the developer image by the transfer member is synchronized with the position of the medium by the medium conveyance unit, and the transfer is performed. The developer image in the part Characterized in that it comprises a control unit for transferring.

  According to the present invention, even when a medium jam or the like occurs and the time for the recording medium to reach the secondary transfer point is delayed, it takes time to clear the medium jam and the cleaning time of the secondary transfer unit. It is possible to provide an image forming apparatus capable of shortening the length.

It is a schematic sectional drawing for demonstrating the principal part of a printer. It is a schematic sectional drawing for demonstrating the principal part of an image forming means. 2 is a block diagram illustrating a circuit configuration of a printer. FIG. It is a block diagram explaining the internal structure of a control part. FIG. 6 is a diagram illustrating a state where a sheet fed from a sheet cassette is within an image writing position adjustable range with respect to a developer image transferred onto an intermediate transfer belt. It is a graph showing the relationship between the control time and the remaining distance to the secondary transfer point. FIG. 10 is a diagram illustrating a state in which a sheet fed from a sheet cassette is not in an image writing position adjustable range, a sheet delay amount is within a specified range, and it is not determined that the sheet is jammed. It is a graph showing the relationship between the control time and the remaining distance to the secondary transfer point. 6 is a flowchart illustrating secondary transfer timing error control. It is the figure which represented the content demonstrated with the flowchart of FIG. 9 with the time chart. FIG. 10 is a diagram illustrating an image of a printing result when secondary transfer timing error control is applied and a printing result when secondary transfer timing error control is not applied. 6 is a flowchart illustrating secondary transfer timing error control. It is a graph showing the relationship between the control time and the remaining distance to the secondary transfer point. 6 is a flowchart illustrating secondary transfer timing error control. It is the figure which represented the content demonstrated with the flowchart of FIG. 14 with the time chart.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to the following description, In the range which does not deviate from the summary of this invention, it can change suitably.

[First embodiment]
FIG. 1 is a schematic cross-sectional view for explaining a main part of the printer 1 according to the first embodiment. FIG. 2 is a schematic cross-sectional view for explaining the main part of the image forming means 5 provided in the printer 1. The printer 1 is an intermediate transfer type image forming apparatus capable of forming a color image on a recording medium.

  As shown in FIG. 1, the printer 1 includes a driven roller 2, an intermediate transfer belt drive roller 3, an intermediate transfer belt 4 as a transfer member, and image forming means 5K (black), 5Y (yellow), 5M ( Magenta), 5C (cyan), primary transfer rollers 9K, 9Y, 9M, and 9C, secondary transfer rollers 10 and 11 as transfer portions according to the present embodiment, paper feed roller 12, and transport roller 13 , Registration rollers 14, conveyance rollers 15, 16, fixing roller 17, backup roller 18, discharge conveyance rollers 19, 20, 21, registration rollers 22, paper 23 as a recording medium, and conveyance sensor 24. , 25, face-down stacker 26, face-up stacker 27, transport sensor 28, paper feed sensor 29, and paper cassette 30 as a medium storage unit. Comprises an auxiliary feed roller 31.

  The driven roller 2 is a stretching member that stretches the intermediate transfer belt 4 together with the intermediate transfer belt driving roller 3 and the secondary transfer roller 10. The driven roller 2 rotates along with the rotation of the intermediate transfer belt driving roller 3 to drive the intermediate transfer belt 4.

  The intermediate transfer belt drive roller 3 is rotated by a driving force transmitted via a transmission mechanism such as a gear (not shown) as the intermediate transfer belt drive motor 129 is driven, and the intermediate transfer belt 4 is moved in the arrow direction in the drawing. Drive.

  The intermediate transfer belt 4 is an endless belt member, and rotates secondary developer rollers 10 and 11 (hereinafter referred to as secondary transfer rollers) by rotationally driving developer images formed by the respective image forming units 5K, 5Y, 5M, and 5C. The transfer position formed by the rollers 10 and 11 is conveyed to a secondary transfer point).

  The image forming units 5K, 5Y, 5M, and 5C form developer images corresponding to the developers of the respective colors (K: black, Y: yellow, M: magenta, C: cyan), and along the intermediate transfer belt 4. The printer 1 is detachably mounted. Here, the configuration of the image forming units 5K, 5Y, 5M, and 5C will be described with reference to FIG. The image forming units 5K, 5Y, 5M, and 5C are different only in the developer stored in the toner cartridge 6 and other configurations are the same. Therefore, in the description of FIG. The image forming means 5K for forming the image will be described as an example.

  The image forming means 5K includes a toner cartridge 6K that contains a black developer, an exposure device 7K that forms an electrostatic latent image on the surface of the photosensitive drum 8K, and a black developer that adheres to the electrostatic latent image. And a photosensitive drum 8K for forming a developer image. A cleaning member 200K for cleaning the developer remaining on the surface of the photosensitive drum 8K, a charging roller 201K for uniformly and uniformly charging the photosensitive drum 8K, and a photosensitive member from the upstream side in the rotation direction of the photosensitive drum 8K. A developing roller 202K that develops an electrostatic latent image by attaching a developer to the drum 8K and a supply roller 203K that supplies the image agent to the developing roller 202K are provided. Further, the image forming unit 5K includes a toner sensor 204K that detects the amount of developer replenished from the toner cartridge 6K.

  The toner cartridge 6K is a box-shaped member having a storage space for storing unused developer. A shutter (not shown) for supplying the developer to the supply roller 203K is formed below the toner cartridge 6K, and the developer dropped through the shutter (not shown) is rotatably supported. While being stirred by a stirring member (not shown), it is supplied to the supply roller 203K by a transport member (not shown).

  The exposure device 7K is, for example, an LED head having a light emitting element such as an LED element and a lens array, and is a position where irradiation light output from the LED element is imaged on the surface of the photosensitive drum 8K based on image data. It is arranged like this.

  The photosensitive drum 8K includes a conductive support and a photoconductive layer. For example, a charge generation layer as a photoconductive layer and a charge transport layer are sequentially stacked on a metal shaft such as aluminum as a conductive support. Is an organic photoconductor configured.

  The cleaning member 200K is, for example, a urethane rubber member, and one end of the cleaning member 200K is disposed at a position in contact with a predetermined position on the surface of the photosensitive drum 8K. The cleaning member 200K cleans the surface of the photosensitive drum 8K by scraping off the developer remaining on the surface of the photosensitive drum 8K.

  The charging roller 201K is constituted by, for example, a metal shaft and semiconductive epichlorohydrin rubber. The charging roller 201K is in contact with the photosensitive drum 8K with a predetermined pressure, and uniformly charges the surface of the photosensitive drum 8K based on an applied voltage from a high-voltage power source described later.

  For example, the developing roller 202K is provided with urethane rubber in which carbon black is dispersed on the outer periphery of a metal shaft such as stainless steel, and the surface thereof is subjected to an isocyanate treatment. The developing roller 202K is disposed so as to be in pressure contact with the surface of the photosensitive drum 8K, supplies a developer to the electrostatic latent image formed on the photosensitive drum 8K, and develops the developer image.

  The supply roller 203K has a semiconductive foamed silicone sponge layer disposed on the outer periphery of a metal shaft such as stainless steel. The supply roller 203K is in contact with the developing roller 202K with a predetermined pressure, and supplies the developer stored in the toner cartridge 6K to the developing roller 202K.

  The primary transfer rollers 9K, 9Y, 9M, and 9C are disposed so as to be in pressure contact with the photosensitive drums 8K, 8Y, 8M, and 8C included in the image forming units 5K, 5Y, 5M, and 5C. The primary transfer rollers 9K, 9Y, 9M, and 9C are connected to a high-voltage power source, which will be described later, and a developer image formed on each photosensitive drum is applied to the primary transfer rollers 9K, 9Y, 9M, and 9C. The image is transferred to the intermediate transfer belt 4 by the applied voltage.

  The secondary transfer rollers 10 and 11 sandwich the conveyed paper 23 together with the developer image transferred onto the intermediate transfer belt 4, and the secondary transfer voltage having a polarity opposite to the potential of the charged developer is a roller. 11, the developer image on the intermediate transfer belt 4 is secondarily transferred onto the paper 23.

  The paper feed roller 12 is rotated together with the auxiliary paper feed roller 31 by the driving force transmitted via a transmission mechanism such as a gear (not shown) as the paper feed roller drive motor 113 is driven, and is attached to and detached from the lower portion of the printer 1. A sheet 23 set in a freely provided sheet cassette 30 is fed.

  The conveyance roller 13, the registration roller 14, and the conveyance rollers 15 and 16 are disposed on a medium conveyance path that conveys the paper 23 to the secondary transfer point. The sheet 23 is conveyed by being rotated by the driving force transmitted via a transmission mechanism such as a gear (not shown).

  The fixing roller 17 is formed, for example, by covering a hollow cylindrical metal core made of aluminum or the like with a heat-resistant elastic layer of silicone rubber, and covering a PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) tube thereon. Is formed by. In the cored bar, for example, a fixing device heater 115 such as a halogen lamp is provided. The backup roller 18 has a configuration in which, for example, a metal core made of aluminum or the like is covered with a heat-resistant elastic layer of silicone rubber, and PFA is covered thereon, so that a pressure contact portion is formed between the backup roller 18 and the fixing roller 17. It is arranged. The sheet 23 on which the developer image transferred at the secondary transfer point is transferred passes through a pressure contact portion formed by the fixing roller 17 and the backup roller 18 maintained at a predetermined temperature, thereby developing on the sheet 23. Heat and pressure are applied to the developer, the developer melts, and the developer image is fixed.

  The discharge transport rollers 19, 20, and 21 are rotated by a driving force transmitted via a transmission mechanism such as a gear (not shown) as the transport roller driving motor 121 is driven, and the fixing surface is a lower side. 23 is discharged to the face-down stacker 26 formed by using the outer casing of the printer 1.

  The registration roller 22 is a roller that performs an abutting process for removing the skew of the paper 23 after feeding based on a detection signal from the conveyance sensor 28. A gear (not shown) or the like is driven by the driving of the registration roller driving motor 119. It is rotated by the driving force transmitted through the transmission mechanism.

  The conveyance sensor 24 is a sensor that detects that the paper 23 has reached a first arrival position, which will be described later, and the conveyance sensor 25 is a sensor that detects that the paper 23 has reached a second arrival position, which will be described later. . The detection signal from the conveyance sensor 25 is also used as a control trigger signal for the secondary transfer voltage applied to the secondary transfer roller 11.

  The face-up stacker 27 stacks the sheets 23 with the fixing surface as an upper side.

  The paper feed sensor 29 is a sensor for detecting a paper feed state when a recording medium is fed from an MP tray (not shown).

  Next, the circuit configuration of the printer 1 according to the present embodiment will be described with reference to the block diagram of FIG.

  The printer 1 captures image data input via a connection unit 102 from a control unit 100 that performs overall control of the operation of the printer 1 and a higher-level image data transfer device connected to the printer 1, and printable data An image processing circuit 101 for conversion into a format; a display unit 103 for displaying an apparatus status of the printer 1; a display unit 103 for prompting an action to the user; a ROM (Read Only Memory) 105 for storing a control program for the printer 1; A RAM (Random Access Memory) 106 used in a working area of a CPU (Central Processing Unit) 208 that functions as 100, a non-volatile memory 107 that stores information to be stored even in a power-off state, and a transport sensor 24 , A sensor output from the transport sensor 25, transport sensor 28, paper feed sensor 29, or other sensor group (not shown). An I / O port 108 for reading a value and a video processing circuit for outputting the image data converted in the image processing circuit 101 to the exposure devices 7K, 7Y, 7M, and 7C and simultaneously counting how many ON dots are output. The counter / counter circuit 109, the DRAM (Dynamic Random Access Memory) 110 that temporarily stores the converted image data before being output from the video processing circuit / counter circuit 109, a paper feed roller drive motor 113, a registration roller A drive circuit for driving each of a drive motor 119, a conveyance roller drive motor 121, a secondary transfer roller drive motor 123, a fixing roller drive motor 125, an image forming unit drive motor 127, and an intermediate transfer belt drive motor 129. Feed roller drive circuit 112, registration roller drive Outputs control signals for controlling the path 118, the conveying roller driving circuit 120, the secondary transfer roller driving circuit 122, the fixing roller driving circuit 124, the image forming unit driving circuit 126, and the intermediate transfer belt driving circuit 128, and fixing. I / O port 111 for controlling the heater driving circuit 114 for driving the heater 115, TIMER 116 for performing timer processing, CH voltage 4 channels, DB voltage 4 channels, SB voltage 4 channels, TR required for image formation And a high-voltage power source 117 having five voltage channels.

  FIG. 4 is a block diagram illustrating the internal configuration of the control unit 100. The control unit 100 includes an image monitoring unit 205 that monitors a position where the developer image on the intermediate transfer belt 4 is present, and an image position determination unit that determines whether the developer image has reached a specified position. 206, based on the detection value output from the transport sensor 24, a paper arrival determination unit 207 that determines whether or not the paper 23 has reached the first arrival position, and a CPU 208 that controls the operation executed by the printer 1. Is provided.

  The operation of the printer 1 having such a configuration will be described with reference to FIGS. 5, 6, 7, 8, 9, and 10.

  When image data transmitted from a host image data transfer device (not shown) (for example, PC: Personal Computer) is received, the image processing circuit 101 converts it into a printable data format. When the image processing circuit 101 converts the image data into a printable data format, the control unit 100 starts a printing operation. As in the present embodiment, in the intermediate transfer type image forming apparatus, from the image forming means (in this embodiment, the image forming means 5K) located on the most upstream side in the developer image transport direction by the intermediate transfer belt. The distance to the secondary transfer point is generally longer than the medium conveyance distance from the paper cassette to the secondary transfer point. For this reason, the start of the image forming process by the image forming unit is started earlier in time than the start of conveyance of the recording medium.

  In FIG. 5, the printing operation is started by the control unit 100, and the sheet 23 fed from the sheet cassette 30 with respect to the developer image transferred onto the intermediate transfer belt 4 is in the image writing position adjustable range. This shows the situation.

  There is a possibility that the paper 23 fed from the paper cassette 30 may be delayed from the required arrival time for some reason before reaching the secondary transfer point. Specifically, when the paper feeding roller 12 starts feeding the paper 23, the registration roller 22 performs a butting process for removing the skew. This process is executed by rotating the registration roller 22 while the registration roller driving circuit 118 measures the timing based on the detection signal from the conveyance sensor 28. Therefore, depending on the rotational speed controlled by the registration roller driving circuit 118, a large slip may occur between the registration roller 22 and the paper 23.

  Even after passing through the registration roller 22, the paper 23 is passed between several transport rollers, and slip is accumulated in the medium transport path including the curved portion. This accumulation of slip is more likely to occur due to wear of the surface of the transport roller due to aging of the apparatus. Further, in an image forming apparatus that is expected to be developed in the future, it is expected that the accumulation of slip is likely to occur as the printing speed increases.

  The leading edge of the developer image A formed on the intermediate transfer belt 4 by the image forming units 5K, 5Y, 5M, and 5C shown in FIG. 5 has reached the position L11 on the upstream side in the developer transport direction from the secondary transfer point. Sometimes, the paper arrival determination unit 207 of the control unit 100 determines whether or not the conveyed paper 23 has reached the first arrival position. That is, the leading edge of the paper 23 started to be fed from the paper cassette 30 should be detected by the transport sensor 24 located at the first arrival position unless a large slip or load is generated during the transport. The paper arrival determination unit 207 determines whether or not the paper 23 being conveyed has reached the first arrival position by confirming the detection value from the conveyance sensor 24.

  Here, if the distance from the leading edge of the paper 23 to the secondary transfer point is L2, the leading edge of the developer image whose formation has been started earlier is positioned at the leading edge of the paper 23 that has started feeding late. Already overtaken at the time. When the distance from the secondary transfer point to the position of the leading end L11 of the developer image A on the upstream side in the developer transport direction is L1, the relationship between L1 and L2 is L1> L2. This is because the positional relationship earlier than the developer image is set in consideration of the delay of the paper 23 that is expected to occur during the medium conveyance, and the medium conveyance speed is reduced according to the margin of the subsequent positional relationship. This is to adjust the secondary transfer point. With this medium conveyance speed control, the sheet 23 conveyed to the conveyance sensor 24 has its medium conveyance speed decelerated when it reaches the deceleration position calculated by calculation, and the arrival timing of the developer image conveyed later. Adapted.

  FIG. 6 is a graph showing the relationship between the control time and the remaining distance to the secondary transfer point. The intermediate transfer belt 4 is driven at a constant speed from the start of image formation at the left end of the graph, and a developer image is formed on the intermediate transfer belt 4. The sheet 23 that is started to be transported after the start of image formation is transported at a transport speed that is faster than the transport speed of the developer image for the reasons described above.

  Therefore, the difference between the remaining distance of the developer image and the remaining distance of the paper 23 increases from the start of image formation to the first half. When the image position determination unit 206 detects that the developer image has been transported to a specified position (paper position check point), the paper arrival determination unit 203 confirms the transport status of the paper 23. Here, when the sheet 23 passes the conveyance sensor 24 (first arrival position), the CPU 208 calculates a subsequent medium conveyance control method based on the previously managed sheet position information.

  When the sheet 23 reaches the deceleration point calculated by the CPU 208, the control unit 100 controls the conveyance roller drive circuit 120 to switch the conveyance of the sheet 23 to the specified low speed conveyance. Thereafter, the control unit 100 conveys the sheet 23 at a low speed until the leading end of the sheet 23 is detected by the conveyance sensor 25 which is the second arrival position. When the leading edge of the paper 23 reaches the transport sensor 23, the control unit 100 switches the transport speed of the paper 23 to the normal printing speed and adjusts the developer image writing position.

  Note that if the transport sensor 25 reconfirms the leading edge position of the paper 23 and the writing start position is slightly different, the CPU 208 can perform recalculation and make fine adjustments. As an example of the fine adjustment method, it is possible to adjust the time until the sheet 23 returns to the normal printing speed after passing through the conveyance sensor 25, the speed gradient when the sheet 23 is returned, and the like. The above is the description of the conveyance control when the conveyed paper 23 is in the image writing position adjustable range.

  Next, a description will be given of a case where the conveyed paper 23 is not in the image writing position adjustable range, the paper delay amount is within a specified range, and it is not determined that the paper is jammed.

  When the leading edge of the developer image formed on the intermediate transfer belt 4 by the image forming units 5K, 5Y, 5M, and 5C shown in FIG. 7 reaches the position L11 on the upstream side in the developer transport direction from the secondary transfer point. In addition, as a result of the paper arrival determination unit 207 of the control unit 100 determining whether or not the paper 23 being conveyed has reached the conveyance sensor 24 (first arrival position), the leading edge of the paper 23 reaches the first arrival. When it is determined that the position has not been reached, at that time, the control unit 100 stops the image formation, the intermediate transfer belt drive, and the drive of the secondary transfer rollers 10 and 11. It should be noted that the position of the paper 23 that has been delayed in conveyance is considered to be unstable due to a delay factor whose cause is unknown, and therefore it is unclear exactly where the paper 23 has reached. This is related to the fact that the feed force at the transport roller changes depending on the type of paper 23 and the like, and the surface condition of the roller changes due to aging of the apparatus.

  The control unit 100 waits for the sheet 23 to pass through the transport roller 14 to be transported in a relatively stable transport state and to pass through the transport sensor 24, and then resumes driving of the intermediate transfer belt 4. . As shown in FIG. 5, when the distance from the leading edge of the sheet 23 to the secondary transfer point is L2, and the distance from the secondary transfer point to the position of L11 on the upstream side in the developer transport direction is L1, L1 and L2 Is already L1> L2, and the control unit 100 can transport the sheet 23 at a low speed. However, at this time, the formation of the developer image has already been stopped, and the developer image that is secondarily transferred onto the paper 23 is transferred as an image with the latter half portion cut off depending on the image size. The

  FIG. 8 is a graph showing the relationship between the control time and the remaining distance to the secondary transfer point. The intermediate transfer belt 4 is driven at a constant speed from the start of image formation at the left end of the graph, and a developer image is formed on the intermediate transfer belt 4. The paper 23 that is started to be transported after the start of image formation is transported at a transport speed that is slower than the transport speed of the developer image for the reasons described above. appear.

  In such a case, when the developer image reaches the paper position check point due to occurrence of slipping or the like, the paper 23 has not yet passed the transport sensor 24 (first arrival position), and the printing operation is continued as it is. As a result, the developer image reaches the secondary transfer point earlier than the sheet 23, and the developer image directly adheres to the secondary transfer rollers 10, 11 and the like, and stains occur. Under such circumstances, it takes time for cleaning and time and effort to eliminate the backside contamination of the paper, which causes a negative factor for the user. In the present embodiment, in order to prevent the occurrence of such a situation, the control described below is performed to prevent the secondary transfer rollers 10, 11 and the like from being soiled by the developer.

  First, the paper arrival determination unit 207 of the control unit 100 checks whether or not the paper 23 has reached the transport sensor 24 when the formed developer image has reached the paper position check point. If the paper arrival determination unit 207 determines that the paper 23 has not reached the conveyance sensor 24, the control unit 100 stops image formation, intermediate transfer belt driving, and driving of the secondary transfer rollers 10 and 11. Let Then, the control unit 100 waits until the paper 23 reaches the conveyance sensor 24 in a state where the image formation, the intermediate transfer belt drive, and the drive of the secondary transfer rollers 10 and 11 are stopped.

  At this time, if the paper 23 does not reach the transport sensor 24 within the specified time, the control unit 100 determines that the paper is normally jammed and notifies the user via the display unit 103. When the user confirms that the paper 23 has been removed, the control unit 100 drives the intermediate transfer belt 4 and the secondary transfer rollers 10 and 11 to perform a cleaning operation.

  On the other hand, when the paper 23 reaches the conveyance sensor 24 within the specified time, the control unit 100 cannot obtain the developer image as a printed matter because the image formation is once stopped. By transferring the untransferred developer onto the paper 23 conveyed with a delay, it is possible to prevent the secondary transfer rollers 10, 11 and the like from being soiled by the developer.

  That is, when the sheet 23 reaches the conveyance sensor 24 within a specified time, the control unit 100 drives the intermediate transfer belt 4 and the secondary transfer rollers 10 and 11 again at the original normal printing speed, and simultaneously the sheet. 23 is switched to a low speed. The conveyance of the sheet 23 at this low speed starts when the sheet 23 passes through the conveyance sensor 24 and reaches a position where the remaining distance of the developer image up to the secondary transfer point and the remaining distance of the sheet 23 are the same. Executed.

  The low-speed conveyance control time is calculated in advance, and is controlled to be adjusted at a timing when the developer image is accommodated inside the paper 23 including the acceleration time. Based on the speed control calculated in this way, when the developer image and the paper 23 conveyed at a constant speed reach the secondary transfer point, the developer image is secondarily transferred onto the paper 23. Then, the sheet 23 on which the developer image has been transferred passes through the press contact portion formed by the fixing roller 17 and the backup roller 18 to be fixed and discharged outside the apparatus.

  In the above control, the paper 23 used for printing is used for discarding the developer constituting the developer image. However, according to this control, the cleaning time and the back stain of the paper are eliminated. This saves you time and effort. The above is the description of the conveyance control when the conveyed paper 23 is outside the image writing position adjustable range.

  Next, the secondary transfer timing error control described above will be described with reference to the flowchart of FIG.

  First, in step S1, when the secondary transfer timing error process for the main conveyance control is started, the image forming unit starts image formation (step S2). At the same time, the control unit 100 activates the TIMER 116 and starts counting for a certain time.

  When the predetermined time has elapsed (Y in step S3), the control unit 100 starts conveying the paper 23 (step S4).

  Next, the image position determination unit 206 uses the image position monitoring unit 205 to check how far the developer image on the intermediate transfer belt 4 has reached. If the image position determination unit 206 determines that the developer image has reached a specified position (paper check point) for confirming the paper position (Y in step S5), the paper arrival determination unit 207 It is determined whether or not 23 has passed the conveyance sensor 24.

  If the paper arrival determining unit 207 determines that the paper 23 has passed the transport sensor 24 (Y in step S6), the control unit 100 executes the secondary transfer process as usual (step S7). On the other hand, when the paper arrival determining unit 207 determines that the paper 23 has not passed the transport sensor 24 (N in step S <b> 6), the control unit 100 performs image formation, intermediate transfer belt driving, and the secondary transfer roller 10. , 11 is stopped (step S8).

  When the paper arrival determining unit 207 determines that the paper 23 has passed the transport sensor 24 (Y in step S10), the control unit 100 switches the transport speed of the paper 23 to the low speed transport speed. At the same time, the control unit 100 resumes driving of the intermediate transfer belt 4 and the secondary transfer rollers 10 and 11 at the normal printing speed (step S12). On the other hand, when the paper arrival determining unit 207 determines that the paper 23 does not pass through the conveyance sensor 24 (Y in step S10) and a certain time has passed (Y in step S9), the control unit 100 causes the normal paper jam, It is determined that a so-called JAM has occurred, and a paper feed JAM process such as removal of the paper 23 by the user is executed (step S11).

  After the low-speed conveyance control of the paper 23 is performed for the specified time (step S13), the control unit 100 switches the conveyance speed of the paper 23 to the normal printing speed (step S14). When the image position determination unit 206 determines that the developer image and the paper 23 have reached the secondary transfer point (step SY), the control unit 100 causes the secondary transfer process to be executed (step S16).

  In step S17, the paper 23 on which the developer image has been transferred is fixed by applying heat and pressure by the fixing roller 17 and the backup roller 18, and then discharged outside the apparatus (step S18). This completes the secondary transfer timing error process.

  FIG. 10 is a time chart showing the contents described in the flowchart of FIG.

  First, when the image forming unit driving motor 127, the intermediate transfer belt driving motor 129, and the secondary transfer roller driving motor 123 start driving, the image forming synchronization signal is turned ON to start image formation (note that image forming synchronization is performed). The signal is representatively black (K) only). After that, the paper conveyance system drive motor starts driving, and the paper 23 follows the preceding developer image.

  When the developer image reaches the paper check point and the paper 23 does not reach the transport sensor 24, the image forming unit drive motor 127, the intermediate transfer belt drive motor 129, and the secondary transfer roller drive motor 123 are The image forming is stopped and image formation is stopped.

  The conveyance operation is continued for the sheet 23 conveyed with a delay, and the sheet 23 eventually reaches the conveyance sensor 24. The conveyance speed of the paper 23 that has reached the conveyance sensor 24 is changed to a low speed, and the image forming unit drive motor 127, the intermediate transfer belt drive motor 129, and the secondary transfer roller drive motor 123 resume driving at a normal printing speed. To do. When the sheet 23 conveyed at a low speed reaches the conveyance sensor 25, the conveyance speed is changed to a normal printing speed, and the developer image is transferred to the sheet 23 at the secondary transfer point. That is, this synchronizes the position of the developer image A and the position of the sheet 23 as a medium.

  FIG. 11 is an image diagram showing a printing result when the secondary transfer timing error control according to the present embodiment is applied and a printing result when the secondary transfer timing error control is not applied. FIG. 11A shows a normal printing result, FIG. 11B shows a printing result when the secondary transfer timing error control is applied, and FIG. 11C shows a secondary transfer timing error control. It shows the print result when not.

  As shown in FIG. 11B, when the secondary transfer timing error control according to this embodiment is applied, a print image cannot be obtained, but at least a developer adheres to the secondary transfer roller or the like. Can be prevented from being soiled. As shown in the figure, the tip of the developer image is within the paper.

  As shown in FIG. 11C, when the secondary transfer timing error control is not applied, the secondary transfer is performed in a state in which the paper whose conveyance is delayed is ignored, and therefore precedes the paper. The developer image is shifted to the position. Due to such a shift of the developer image, the developer overflowing from the sheet area contaminates the secondary transfer roller.

  In general, when the apparatus is miniaturized as much as possible and the control is simplified, the secondary transfer unit often has a structure in which no separation mechanism is provided. In such a structure, when the developer is present on the intermediate transfer belt, the secondary transfer roller is soiled by the developer. In an apparatus that does not have a separation mechanism, a mechanism for cleaning the secondary transfer roller is separately provided, but generally, a system using a cleaning blade, a cleaning roller, or the like is mostly used. For this reason, once it is attempted to clean the secondary transfer roller soiled by the developer, it generally takes a very long time.

  According to the secondary transfer timing error control according to the present embodiment, it is not possible to obtain a print image, but it is possible to prevent the secondary transfer roller and the like from being soiled due to at least the developer adhering thereto.

  Note that the secondary transfer timing error control according to the present embodiment is a control that does not give the user a particular sense of incongruity in appearance because the paper discharge time is slightly later than usual. Therefore, when the secondary transfer timing error control functions, the user may be notified via the display unit 103 or the like. In this case, for example, by displaying a message such as “secondary transfer timing error occurred: defective printed matter has been discharged” on the display unit 103, the user is notified that the secondary transfer timing error control functioned. Can do.

  As described above, according to the first embodiment, even when a medium jam or the like occurs and the time for the recording medium to reach the secondary transfer point is delayed, it takes time to clear the medium jam. In addition, the cleaning time of the secondary transfer unit can be shortened.

[Second Embodiment]
The configuration and operation of the printer in the second embodiment are substantially the same as those of the printer 1 according to the first embodiment. Accordingly, the same portions are denoted by the same reference numerals and description thereof is omitted.

  In the second embodiment, a description will be given of a control in which the sheet discharge destination after fixing is different between the case where the secondary transfer timing error control described in the first embodiment functions and the case where the secondary transfer timing error control does not function.

  FIG. 12 is a flowchart for explaining secondary transfer timing error control according to the second embodiment. In the process according to this flowchart, a discharge destination tray change process (step S20) is newly added between the fixing process in step S17 and the discharge process in step S18 in the flowchart described in FIG. 9 of the first embodiment. Other processes can be performed in the same manner as the process described in FIG.

  In step S17, heat and pressure are applied to the sheet 23 on which the developer image has been transferred by the fixing roller 17 and the backup roller 18, and are fixed. Next, the control unit 100 changes the discharge tray used during normal printing from the discharge tray used for normal printing to another discharge tray as a tray from which the fixed sheet 23 is discharged (step S20).

  Then, the sheet 23 is discharged to the discharge tray changed by the control unit 100, and the secondary transfer timing error process ends.

  As described above, according to the second embodiment, in addition to the effects of the first embodiment, since the sheet is discharged to a discharge tray different from that during normal printing, the secondary transfer timing error control has functioned. Can be notified to the user, and an abnormal print result and a normal print result can be sorted, so that an abnormal print result can be prevented from being used by mistake. .

[Third embodiment]
The configuration and operation of the printer in the third embodiment are substantially the same as those of the printer according to the first and second embodiments. Accordingly, the same portions are denoted by the same reference numerals and description thereof is omitted.

  In the third embodiment, a mode in which the developer image transport speed and the paper transport speed in the secondary transfer are different will be described. Specifically, in the third embodiment, the conveyance speed of the paper at the time of secondary transfer is the normal printing speed, but the conveyance speed of the developer image, that is, the driving speed of the intermediate transfer belt is set to be higher than the normal printing speed. It controls to a high driving speed.

  FIG. 13 is a graph showing the relationship between the control time and the remaining distance to the secondary transfer point according to this embodiment. Here, since the operation up to the secondary transfer point is the same as that of the first embodiment or the second embodiment, the description thereof is omitted.

  When the developer image on the intermediate transfer belt 4 and the leading edge of the paper 23 reach the secondary transfer point, the controller 100 controls the intermediate transfer belt drive motor 129 to transfer the intermediate transfer belt. The driving speed of 4 is set to a driving speed faster than the normal printing speed.

  At the secondary transfer point, the developer image on the intermediate transfer belt 4 to which the speed difference is given becomes rubbed more strongly against the paper 23, and the developer can be scraped off more effectively. At this time, in addition to the developer constituting the developer image formed on the intermediate transfer belt 4, the fog developer is also scraped off together.

  The speed difference between the set driving speed of the intermediate transfer belt 4 and the conveyance speed of the paper 23 can be changed as appropriate depending on how much cleaning is performed.

  Then, the control unit 100 stops the secondary transfer roller drive motor 123, the paper transport system drive motor, and the intermediate transfer belt drive motor 129 at the timing when the rear end of the paper 23 passes the secondary fixing point.

  FIG. 14 is a flowchart for explaining secondary transfer timing error control according to the third embodiment. In the process according to this flowchart, the intermediate transfer belt driving speed increasing process (step S21) is performed between the secondary transfer process in step S16 and the fixing process in step S17 in the flowchart described in FIG. 9 of the first embodiment. This is a new addition, and other processes can be performed in the same manner as the process described with reference to FIG.

  In step S21, the control unit 100 controls the intermediate transfer belt drive motor 129 to set the drive speed of the intermediate transfer belt 4 to a drive speed higher than the normal printing speed.

  FIG. 15 is a time chart showing the contents described in the flowchart of FIG.

  First, when the image forming unit driving motor 127, the intermediate transfer belt driving motor 129, and the secondary transfer roller driving motor 123 start driving, the image forming synchronization signal is turned ON to start image formation (note that image forming synchronization is performed). The signal is representatively black (K) only). After that, the paper conveyance system drive motor starts driving, and the paper 23 follows the preceding developer image.

  When the developer image reaches the paper check point and the paper 23 does not reach the transport sensor 24, the image forming unit drive motor 127, the intermediate transfer belt drive motor 129, and the secondary transfer roller drive motor 123 are The image forming is stopped and image formation is stopped.

  The conveyance operation is continued for the sheet 23 conveyed with a delay, and the sheet 23 eventually reaches the conveyance sensor 24. The conveyance speed of the paper 23 that has reached the conveyance sensor 24 is changed to a low speed. The image forming unit driving motor 127 and the intermediate transfer belt driving motor 129 resume driving at the fog cleaning driving speed, and the secondary transfer roller driving motor 123 resumes driving at the normal printing speed. When the sheet 23 conveyed at a low speed reaches the conveyance sensor 25, the conveyance speed is changed to a normal printing speed, and the developer image is transferred to the sheet 23 at the secondary transfer point.

  As described above, according to the third embodiment, in addition to the effects of the first embodiment, the driving speed of the intermediate transfer belt is controlled to be higher than the normal printing speed. Not only the developer present but also the fog developer can be cleaned together.

  In the description of the embodiment of the present invention, a color electrophotographic printer has been described as an example. However, the application of the present invention is not limited to this, and any image forming apparatus having a similar structure can be used. It can also be applied to an MFP or the like.

Reference Signs List 1 printer 2 driven roller 3 intermediate transfer belt drive roller 4 intermediate transfer belt 5 image forming means 6 toner cartridge 7 exposure device 8 photosensitive drum 9 primary transfer roller 10 secondary transfer roller 11 secondary transfer roller 12 paper feed roller 13 Roller 14 Registration roller 15 Conveying roller 16 Conveying roller 17 Fixing roller 18 Backup roller 19 Discharging conveying roller 20 Discharging conveying roller 21 Discharging conveying roller 22 Registration roller 23 Paper 24 Conveying sensor 25 Conveying sensor 26 Face down stacker 27 Face up stacker 28 Conveyance sensor 29 Paper feed sensor 30 Paper cassette 31 Auxiliary supply roller 200 Cleaning member 201 Charging roller 202 Development roller 203 Supply roller 204 Toner sensor

Claims (8)

An image forming means for forming a developer image using a developer;
A transfer unit that transfers the developer image formed by the image forming unit to a medium;
A transfer-receiving member that conveys the developer image to the transfer unit;
A medium transport unit that transports the medium stored in the medium storage unit to the transfer unit;
A medium detection unit that detects whether or not the medium conveyed by the medium conveyance unit has reached a predetermined arrival position;
When the medium detection unit does not detect the arrival of the medium at the predetermined arrival position, the drive of the transfer member and the formation of the developer image by the image forming unit are temporarily stopped and the predetermined time after the stop When the medium detection unit detects the arrival of the medium at the predetermined arrival position in time, the position of the developer image by the transferred member and the position of the medium by the medium conveyance unit are synchronized, An image forming apparatus comprising: a control unit that transfers the developer image onto the medium in the transfer unit. The controller is
When the medium detection unit does not detect the arrival of the medium at the predetermined arrival position, the drive of the transfer member and the formation of the developer image by the image forming unit are temporarily stopped and the predetermined time after the stop When the medium detection unit detects the arrival of the medium at the predetermined arrival position within the time, the conveyance speed of the developer image by the transfer member and the conveyance speed of the medium by the medium conveyance unit are synchronized. The image forming apparatus according to claim 1, wherein the developer image is transferred to the medium in the transfer unit. The controller is
The medium according to claim 1, wherein when the medium detection unit does not detect the arrival of the medium at the predetermined arrival position within a predetermined time after the stop, it is determined that the medium is jammed. The image forming apparatus described. The predetermined arrival position is
4. The apparatus is set based on a relationship between a transport distance of the developer image from the image forming unit to the transfer section and a transport distance of the medium from the medium storage section to the transfer section. 5. The image forming apparatus according to claim 1. The image forming apparatus according to claim 1, further comprising: a fixing unit that fixes the developer image transferred in the transfer unit to the medium. A plurality of medium discharge sections for discharging the medium onto which the developer image has been transferred to the outside of the apparatus;
The controller is
The conveyance speed of the developer image by the member to be transferred and the conveyance speed of the medium by the medium conveyance unit are synchronized, and the medium on which the developer image is transferred in the transfer unit is different from the normal part. The image forming apparatus according to claim 1, wherein the image forming apparatus discharges the image to a medium discharge unit. It has a display unit that displays the device status,
The controller is
When the medium detection unit does not detect the arrival of the medium at the predetermined arrival position, the drive of the transfer member and the formation of the developer image by the image forming unit are temporarily stopped and the predetermined time after the stop When the medium detection unit detects the arrival of the medium at the predetermined arrival position within the time, the conveyance speed of the developer image by the transfer member and the conveyance speed of the medium by the medium conveyance unit are synchronized. The image forming apparatus according to claim 1, wherein the display unit displays that the developer image has been transferred to the medium in the transfer unit. The controller is
When the medium detection unit does not detect the arrival of the medium at the predetermined arrival position, the drive of the transfer member and the formation of the developer image by the image forming unit are temporarily stopped and the predetermined time after the stop When the medium detection unit detects that the medium has reached the predetermined arrival position within a time, the developer image transport speed by the transfer member is faster than the medium transport speed by the medium transport section The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled to a conveyance speed.