JP2007003823A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent occurrence of defects in image quality or occurrence of abnormal sound over a long term. <P>SOLUTION: A relative speed difference is given to a nip part between a photoreceptor drum 11 and primary intermediate transfer drums 21 and 22, whereby transfer efficiency is improved, and also the relative speed difference is varied in a predetermined cycle, whereby the occurrence cycle of stick slip is adjusted to a desired cycle and stripe image irregularity caused by the stick slip is made inconspicuous. The relative speed difference is made zero if necessary (especially, when an image is not transferred), thereby eliminating the occurrence of abnormal sound caused by the stick slip. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, and a facsimile using an electrophotographic system, and includes an image forming engine unit that transfers a toner image from an image carrier to a transfer target member. An image forming apparatus to be formed.

  2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus charges an image carrier made of a photosensitive drum or the like by a charging device, forms an electrostatic latent image based on image information on the charged image carrier, and the electrostatic latent image is formed. The image is developed with a developer supplied from a developing device to be visualized as a toner image, the toner image is transferred to an intermediate transfer body such as a drum type or a belt type, and the toner image transferred onto the intermediate transfer body is transferred to the toner image. By transferring and fixing to a recording medium such as paper, an image composed of a fixed toner image is formed on the recording medium.

  Such an intermediate transfer type image forming apparatus forms not only a single color image but also a full color image composed of four colors such as yellow (Y), magenta (M), black (K), and cyan (C). Widely used.

  However, in this intermediate transfer type image forming apparatus, since transfer is performed a plurality of times, image quality defects such as missing characters in characters, uneven density of halftone images, and ghosts may occur. Therefore, preventing these image defects is a big problem.

  For example, Patent Document 1 similarly has a configuration including a rotation control unit in order to improve transfer efficiency and image defects. However, the control method is a fixed value, and in particular, the printing speed is increased. As a result, it is actually difficult to achieve both transfer efficiency and high image quality.

  Japanese Patent Application Laid-Open No. 2004-228561 has a configuration in which the color registration deviation due to the difference in the dynamic friction coefficient caused by the difference in the printing rate is corrected by changing the relative speed difference of each color depending on the printing rate. It is a fixed value for each sheet.

  Furthermore, Patent Document 3 discloses a mode in which a relative speed difference is provided between the surface speed of the photoconductor drum and the surface speed of the intermediate transfer drum in order to prevent the character from being omitted, and a halftone image. In order to prevent density unevenness, there is disclosed an image forming apparatus having two drive modes of a mode in which the intermediate transfer drum is driven in a state of being driven by a photosensitive drum, and the two drive modes can be switched. Has been.

  However, this image forming apparatus requires a complicated mechanism for switching the drive mode, and thus there is a problem that the cost tends to increase. Further, in this image forming apparatus, the relative speed difference is always constant during the operation, and is insufficient to cope with image defects caused by the relative speed difference.

  Patent Document 4 discloses a resistance value of a primary intermediate transfer member to which a toner image is transferred from an image carrier for the purpose of improving transfer efficiency and preventing transfer ghosts and density fluctuations to obtain a high-quality image. An image forming apparatus is disclosed in which the resistance value of the secondary intermediate transfer body on which the toner image is transferred from the primary intermediate transfer body is higher.

In Patent Document 4, the surface speed of the primary intermediate transfer member is set higher than that of the image carrier, the surface speed of the secondary intermediate transfer member is set lower than the surface speed of the primary intermediate transfer member, and It is disclosed that the surface speed of the primary intermediate transfer member is set slower than that of the support, and the surface speed of the secondary intermediate transfer member is set higher than the surface speed of the primary intermediate transfer member. The result is that the surface speed of the primary intermediate transfer member is set to 1.5% slower than that of the image carrier, and the surface speed of the secondary intermediate transfer member is set to 1.5% faster than the surface speed of the primary intermediate transfer member. Further, it is described that the transfer residual toner becomes zero, and an appropriate image can be obtained by preventing an image from extending and causing an image omission or omission of a fine line image. However, even in this image forming apparatus, the relative speed difference is always constant during the operation, and it becomes difficult to actually achieve both transfer efficiency and high image quality as the printing speed increases.
JP 2005-037646 A Japanese Patent Laid-Open No. 10-039648 JP 2000-356828 A JP 2001-117317 A

  In general, in a transfer method in which a relative speed difference is provided between the photosensitive member and the intermediate transfer member in order to improve transfer efficiency, an irregular stick-slip phenomenon may occur in the nip portion, which is an indefinite frequency. The image quality is poor as banding.

  In order to prevent poor image quality as much as possible, it is desirable to make the relative speed difference as small as possible, but this is a trade-off relationship with transfer efficiency, and it is extremely difficult to fix the optimum conditions especially as printing speed increases. There is a problem.

  In addition, the stick-slip described above generates an abnormal noise depending on the degree, and often causes discomfort to the user.

  In view of the above-described facts, an object of the present invention is to obtain an image forming apparatus capable of preventing the occurrence of poor image quality or the generation of abnormal noise over a long period of time.

  The present invention provides an image bearing member on which an electrostatic latent image is formed while rotating in a predetermined direction and a toner image is formed by development, and a part of the image bearing member is in contact with the peripheral surface of the image bearing member. And an image forming engine for transferring a toner image from the image carrier to the member to be transferred at a nip portion that is the contact position. An image forming apparatus configured to form an image according to a predetermined print sequence, wherein at least the image forming engine unit controls the driving unit during execution of the print sequence to transfer the photosensitive member and the transferred object in the nip portion. A relative speed difference forming control means for forming a relative speed difference with the member; a relative speed difference period changing means for repeatedly changing the relative speed difference by the relative speed difference forming means at a predetermined period; It has.

  According to the present invention, the relative speed difference forming means forms a relative speed difference between the image carrier and the intermediate transfer member, thereby improving transfer efficiency and reducing the transfer residual toner to zero, thereby obtaining an appropriate image. Can do.

  However, on the other hand, stick-slip resulting from the formation of a relative speed difference causes problems such as generation of striped image unevenness and generation of abnormal noise. Therefore, the relative speed difference period changing means repeatedly changes the relative speed difference at a predetermined period to intentionally generate a stick slip for each period.

  In other words, since the relative speed difference vibrates with a certain amplitude, the stick slip occurrence limit is exceeded at any position of this vibration (for example, the position near the maximum peak), and the occurrence of the stick slip has periodicity. Can do.

  By appropriately setting this cycle, even if there is a striped image unevenness, for example, it can be difficult for human eyes to see.

  In the above invention, when the relative speed difference formation control unit forms a difference between the peripheral surface speed of the image carrier and the relative speed of the intermediate transfer member in the nip portion, the image forming engine unit may perform the image transfer. The relative speed difference is changed when the image is not transferred.

  At the time of non-image transfer, it is not necessary to consider the image quality. Therefore, the generation of noise due to stick-slip can be reduced by reducing the relative speed difference.

  On the other hand, during image transfer, the friction coefficient between the image carrier and the intermediate transfer member is reduced due to the presence of the toner image, and the energy at the time of occurrence of stick-slip is relatively small, so that the image quality is not affected. By reducing the relative speed difference to the extent, it is possible to enhance the effect of suppressing abnormal noise generation due to the periodic relative speed difference change.

  In the present invention, during execution of the print sequence, the relative speed difference formation control unit does not form a relative speed difference when the image is not transferred, but forms a relative speed difference only when the image is transferred.

  In the category of reducing the relative speed difference, the occurrence of stick-slip can be eliminated by ultimately eliminating the relative speed difference.

  Further, in the present invention, during execution of the print sequence, the relative speed difference period changing unit does not change the relative speed difference when the image is not transferred, and changes the relative speed difference only when the image is transferred. It is characterized by that.

  When image quality is mainly taken into consideration, it is not necessary to change the period when the image is not transferred. Therefore, this is not executed, and the period of the relative speed difference is changed only at the time of image transfer, thereby reducing the burden on the control system. be able to.

  Further, in the present invention, the relative speed difference by the relative speed difference forming control means depends on the environmental temperature and the environmental humidity, and the relative speed difference is maximized at least at a low temperature, a low humidity, or a high temperature and a high humidity. The relative speed difference is made small.

  Since the relative speed difference depends on the environmental temperature and humidity, if it is not fixed, it can be changed based on the environmental temperature and humidity that change depending on the installation location and operating state of the image forming apparatus. A high-quality image can be obtained, and the effect of suppressing the generation of abnormal noise is enhanced.

  The “other than the above” refers to a region having an intermediate point at a normal temperature and humidity (for example, 20 ° C., 50% RH) where the apparatus is installed. The relative speed difference should be minimized.

  Further, in the present invention, the member to be transferred transfers the toner image formed on the surface of the image carrier onto a recording sheet conveyed along a predetermined conveyance path separated from the peripheral surface of the image carrier. The nip portion is a primary transfer portion, and the transfer portion to the recording paper is a secondary transfer portion.

  As a configuration of the image forming engine unit of the image forming apparatus, there is a structure in which a single intermediate transfer member is in contact with a single image carrier, and the intermediate transfer member and recording paper are in contact with each other. Is the simplest structure. In this case, as the intermediate transfer member, a belt-like intermediate transfer member (intermediate transfer belt) arranged so as to go around a predetermined path as well as a drum-like intermediate transfer roller may be used. .

  In the present invention, when forming a color image by transferring the toner images on the recording paper, the intermediate transfer members are arranged in series according to the number of toner images to be superimposed, It is characterized by arranging a plurality in parallel.

  When forming a color image (for example, including a one-point color), it is necessary to superimpose toner images for respective colors. Therefore, it is possible to form a color image by arranging a plurality of the intermediate transfer members in series and in parallel according to the number of toner images to be superimposed.

  Further, in the present invention, the intermediate transfer member is arranged in series with respect to the pair of primary intermediate transfer members and the pair of primary intermediate transfer members, and the pair of primary intermediate transfer members. A single secondary intermediate transfer body to which a toner image is transferred, and one of the primary intermediate transfer bodies is a Y color image carrier, an M color image carrier, a C color image carrier, and a K color. By transferring the two colors of the image carrier overlaid, transferring the other two colors over to the other primary intermediate transfer body, and transferring over the four colors over the secondary transfer body The method is characterized in that a full-color image is transferred to a recording sheet.

  In the case of a full-color image, it is necessary to superimpose four color toner images of YMCK and to increase the overlay accuracy.

  Therefore, first, two colors are superimposed on one primary intermediate transfer body, and in parallel to this, the other two colors are superimposed on the other primary transfer body, and the secondary contacts each primary transfer body. A full color image can be efficiently formed by superimposing four colors on the transfer body.

  When the relative speed difference is set in the nip portion where the toner image is transferred from the image carrier to the intermediate transfer body (primary intermediate transfer body) in the image forming engine section having various configurations as described above, By periodically changing the speed difference, the image quality can be improved and the occurrence of abnormal noise can be reduced.

  As described above, in the present invention, generation of abnormal noise can be prevented by eliminating the relative speed difference except during image transfer. Further, by eliminating the relative speed difference except during image transfer, unnecessary stick-slip energy can be prevented from being accumulated in the nip portion.

  In addition, by periodically changing the relative speed difference during image transfer, the nip is forced to slip and the stick-slip energy is released periodically, which can cause banding that can seriously affect the image. Can be avoided.

(This embodiment)
FIG. 1 is an internal schematic diagram of the color printer according to the present embodiment, and FIG. 2 is a configuration diagram of a main part of the color printer shown in FIG.

  First, the configuration of the entire printer will be described.

  This color printer is a so-called tandem printer in which image forming engines are arranged in parallel for each color of yellow (Y), magenta (M), black (K), and cyan (C). Can be printed, and a full-color image composed of the four color toner images can be printed.

  This color printer includes a photosensitive drum unit 2, an exposure unit 3 and a developing unit 4, which constitute an image forming engine, an image transfer drum unit 5, a paper feeding unit 6, a fixing unit 7 and the like inside a casing 1. 1 are arranged in a positional relationship as shown in FIG.

  Of these, the housing 1 is a three-dimensional structure that is assembled, for example, in a box shape using components such as a support frame, a support braid, and an exterior cover. However, in FIG. The illustration of the component parts that become the skeleton parts such as the support frame and the support plate is omitted. In FIG. 2, the rotation direction of each component that is rotationally driven is indicated by a solid arrow.

  Further, the printer has a structure in which the photosensitive drum unit 2 and the image transfer unit 5 can be coupled and separated from each other and can be attached to and detached from the image forming position of the housing 1. Further, the combined photosensitive drum unit 2 and image transfer unit 5 are stored and mounted in a predetermined mounting space formed inside the housing 1.

  As shown in FIG. 2, the photoconductor drum unit 2 includes four photoconductors in which toner images of the four colors (Y, M, K, and C) are formed on a support frame 10 assembled in a rectangular frame shape. Drums 11Y, 11M, 11K, and 11C, charging rolls 12 that charge the peripheral surfaces of the photosensitive drums 11 (Y, M, K, and C) to a predetermined background potential, and the peripheral surfaces of the photosensitive drums 11 A temporary toner holding brush roll 13 that temporarily holds the toner remaining on the toner is rotatably mounted and integrated.

  Each of the photoreceptor drums 11Y, 11M, 11K, and 11C is formed of a cylindrical drum body having the same outer diameter and having a photosensitive layer made of an organic photosensitive material or the like formed on the surface thereof. Each of these photosensitive drums 11 is attached via a bearing in a state in which the respective rotation shafts 14Y, 14M, 14K, and 14C are parallel to the support frame 10 at a predetermined interval. A driving device (not shown) including a gear and a motor for driving each photosensitive drum 11 is connected to the shaft.

  The charging roll 12 is formed by coating a conductive elastic body with a certain thickness around a metal roll main body, and the elastic body layer is upstream of the exposure position of the photosensitive drum 11 in the rotation direction. The rotating shafts 12a at both ends of the roll main body are rotatably attached to the support frame 10 via bearings so as to contact the surface portion on the side.

  Further, the charging roll 12 is applied with a DC voltage as a charging voltage on the roll body, and by generating a discharge in a minute gap between the elastic layer and the peripheral surface of the photosensitive drum 11, The peripheral surface of the photosensitive drum 11 is charged.

  The temporary toner holding brush rolls 13Y, 13M, 13K, and 13C are formed around a metal roll main body so that a plurality of brush hairs have a predetermined distribution density. Is attached to the support frame 10 so as to be rotatable. These temporary toner holding brush rolls 13Y, 13M, 13K, 13C temporarily hold the toner adhering to the peripheral surface of each photosensitive drum 11, and these temporary toner holding brush rolls 13Y, The toner temporarily held in 13M, 13K, and 13C is discharged onto each photosensitive drum 11 at a predetermined timing, and the discharged toner is recovered by the recovery roll 25 of the image transfer drum unit 5.

  In this photosensitive drum unit 2, the same coupling (not shown) is fixedly attached to each rotating shaft of each photosensitive drum 11. In addition, a transmission gear is fixedly attached to each rotation shaft of the toner temporary holding brush roll 24, and each of the transmission gears is connected to a transmission gear fixed to the rotation shaft of each photosensitive drum 11. They bite together. As a result, the temporary toner holding brush rolls 13Y, 13M, 13K, and 13C rotate with the photosensitive drum 11 at a fixed surface speed ratio.

  The image transfer drum unit 5 includes a support frame 20 assembled in a rectangular frame shape, two primary intermediate transfer drums 21, 22, one secondary intermediate transfer drum 23, and each of the intermediate transfer drums 21, 22, 23. The toner temporarily holding brush roll 24 that temporarily holds the toner remaining on the peripheral surfaces of the toner and the toner remaining on the peripheral surfaces of the intermediate transfer drums 21, 22, 23 directly or the toner A recovery roll 25 that recovers the toner held on the temporary holding brush roll 24 after being returned to the peripheral surface of each drum is rotatably mounted and integrated.

  Note that the temporary toner holding brush roll 24 and the recovery roll 25 in the present embodiment correspond to the residual toner removing section referred to in the present invention. In this embodiment, the three intermediate transfer drums of the primary intermediate transfer drums 21 and 22 and the secondary intermediate transfer drum 23 are all provided with a temporary toner holding brush roll 24 and a recovery roll 25. Installation of the temporary toner holding brush roll and the recovery roll on the transfer drum 23 is not an essential requirement, and may be installed as necessary.

  Each of the primary intermediate transfer drums 21 and 22 and the secondary intermediate transfer drum 23 has a low resistance of about 0.1 mm to 10 mm made of conductive silicone rubber or the like on a metal pipe of the same outer diameter made of iron, aluminum or the like. After covering an elastic layer (resistance value: 10 2 Ω to 10 3 Ω), a high release layer (resistance value: about 10 5 Ω to 10 13 Ω) made of fluoro rubber or the like is further formed on the surface of the low resistance elastic layer. The drum body formed is supported by a rotating shaft 27, 28, 29.

  Each of the intermediate transfer drums 21, 22, and 23 has its rotary shafts 27, 28, and 29 rotatably attached to predetermined portions of the support frame 20 via bearings.

  In the primary intermediate transfer drums 21 and 22, the peripheral surface of the primary intermediate transfer drum 21 simultaneously contacts the photosensitive drum 11Y and the photosensitive drum 11M to form a nip portion, while the peripheral surface of the primary intermediate transfer drum 22 is photosensitive. The rotating shafts 27 and 28 of the primary intermediate transfer drums 21 and 22 are attached so as to be positioned at predetermined positions of the support frame 20 so as to simultaneously contact the body drum 11K and the photosensitive drum 11C to form a nip portion. ing.

  The secondary intermediate transfer drum 23 has a rotation shaft 29 attached to a predetermined portion of the support frame 20 in such a positional relationship that its peripheral surface simultaneously contacts the primary intermediate transfer drums 21 and 22 to form a nip portion. ing.

  When the secondary intermediate transfer drum 23 is mounted on the housing 1, it comes into contact with the final transfer roll 50 installed on the housing 1 side to form a nip portion (FIG. 1). 2).

  In the primary intermediate transfer drums 21 and 22, the toner images on the respective photosensitive drums 11 are electrostatically primarily transferred onto both of the drums, so that the surface potentials of both drum bodies are set to a predetermined potential (for example, + 250V). A first transfer bias for maintaining the voltage at about +500 V is applied from a bias power source (not shown) via the rotary shafts 27 and 28.

  Further, the secondary intermediate transfer drum 23 is electrostatically secondary-transferred with the toner images on the primary intermediate transfer drums 21 and 22, respectively, so that the surface potential of the drum body is set to a predetermined potential (for example, + 600V). The second transfer bias for holding at about + 1200V is applied from the bias power source (not shown) via the rotary shaft 29.

  The collection roll 25 is a metal roll that rotates in contact with the intermediate transfer drums 21, 22, and 23, and is a bias voltage that can electrostatically attract unnecessary toner on the intermediate transfer drums 21, 22, and 23. , A cleaning blade 25b that contacts and scrapes the toner collected and attracted to the bias roll 25a and scrapes the toner scraped off by the cleaning blade 25b in a predetermined collection box ( It is comprised with the conveyance auger (not shown) which conveys and sends it to (not shown).

  The exposure unit 3 is for writing an electrostatic latent image on each photoconductive drum 11 of the photoconductive drum unit 2. A light source such as a semiconductor laser (not shown) or an image from the light source is provided inside the housing 1. Optical system components such as polygon mirrors, reflecting mirrors, various lenses and the like are arranged as appropriate for guiding the beam light Bm emitted based on the information onto the corresponding photosensitive drums 11 for scanning exposure. The exposure unit 3 scans and exposes the light beam Bm on each photosensitive drum 11 through the gap between the developing units 4, thereby forming an electrostatic latent image having a predetermined surface potential on each photosensitive drum 11. It has become.

  As shown in FIG. 1, the developing unit 4 is arranged in four locations disposed in the vicinity of the photosensitive drum unit 2 in the casing 1 so as to face each photosensitive drum 11 of the photosensitive drum unit 2. The developing device 41 is configured.

  Each of the developing devices 41 is a so-called magnetic brush developing type developing device, and a two-component developer containing toner and carrier is accommodated in the developing device 41. Each developing device 41 includes a developing roll 42 that rotates in close proximity to the photosensitive drum 11 at a predetermined minute interval, and the two-component developer forms a magnetic brush on the developing roll 42. As the developing roll 42 rotates, the photosensitive drum 11 is rubbed.

  A developing bias voltage obtained by superimposing a DC component on an AC component is applied to the developing roll 42, whereby toner is electrostatically attached only to the electrostatic latent image (image portion) of the photosensitive drum 11. A toner image is formed.

  Each developing device 41 requires toner from a toner cartridge 49 (Y, M, K, C) (see FIG. 1) containing the four color toners by a toner replenishing / conveying device (not shown). It will be replenished accordingly.

  The paper feed unit 6 includes a paper feed tray 60 that stores a plurality of recording papers P in a stacked manner, and a paper feeding device 61 that feeds the recording paper P from the paper feed tray 60 one by one. The recording paper P delivered from the paper supply unit 6 is conveyed and supplied at a predetermined timing to the nip portion between the second intermediate transfer roll 23 and the final transfer roll 50 of the image transfer drum unit 5 through a paper conveyance roll 66, a registration roll 68, and the like. Is done.

  1 is a paper conveyance path of the recording paper P. The sheet conveyance path is formed by appropriately arranging a sheet conveyance roll 66, a registration roll 68, a sheet conveyance guide (not shown), and the like.

  The fixing unit 7 is mainly composed of a heating roll 71 with a built-in heating lamp, a pressure roll 72 that presses against the heating roll 71, and a paper discharge roll 73.

  Next, rotation control between the photosensitive drum 11 and the primary intermediate transfer drums 21 and 22 of the color printer of the present embodiment will be described.

  FIG. 3 is a diagram illustrating each drum and a rotation control unit that controls the rotation of each drum in the color printer according to the present embodiment.

  As shown in FIG. 3, the color printer of the present embodiment is configured such that the photosensitive drums 11 </ b> Y, 11 </ b> M, 11 </ b> C, on which an electrostatic latent image is formed while rotating in the direction of the arrow in FIG. 11K and the toner on each photoconductive drum 11 is rotated in the direction of moving in the same direction as the direction of movement of the surface of each photoconductive drum 11 at the nip between each photoconductive drum 11 and contacting each photoconductive drum 11. Primary intermediate transfer drums 21 and 22 that receive image transfer, and secondary intermediate transfer drum 23 that receives transfer of the toner image on the primary intermediate transfer drum, and records the toner image on the secondary intermediate transfer drum 23 By transferring and fixing on the medium P, an image composed of a fixed toner image is formed on the recording medium P.

  The color printer includes a residual toner removing unit 26 composed of a temporary toner holding brush roll 24 and a collecting roll 25 for removing residual toner on the intermediate transfer drums 21, 22, and 23. The relative speed difference between the surface speed and the surface speed of the primary intermediate transfer drums 21 and 22 is 0% during non-transfer, and the relative speed difference periodically varies with respect to the specified relative speed difference during image transfer. It is controlled by the rotation control unit 80.

  FIG. 4 is a functional block diagram mainly showing setting of the relative speed difference between the photosensitive drum 11 and the primary intermediate transfer drums 21 and 22 in the rotation control unit 80.

  The rotation control unit 80 is provided with an engine unit activation instructing unit 100 to receive print sequence information. Based on this print sequence information, the engine unit activation instruction unit 100 sends a drive instruction signal to the drive control unit 102. As a result, the drive control unit 102 controls the drive of each drive means (motor or the like).

  The engine activation instruction unit 100 is connected to a transfer / non-transfer determination unit 104. The transfer / non-transfer determination unit 104 determines whether the current image transfer time or image non-transfer based on the print sequence information. The time is to be judged.

  The result determined by the transfer / non-transfer determination unit 104 is sent to the relative speed difference setting unit 106.

  An environmental coefficient setting unit 108 is connected to the relative speed difference setting unit 106. The environmental coefficient setting unit 108 receives data on the environmental temperature and environmental humidity of the apparatus. Based on the current environmental temperature and environmental humidity, the standard (for example, 20 ° C./50% RH) is used. A correction coefficient (environment coefficient) is set.

  The set correction coefficient (environment coefficient) is sent to the relative speed difference setting unit 106, and the relative speed difference setting unit 106 corrects a predetermined relative speed difference.

  The relative speed difference with respect to the environmental temperature and the environmental humidity has a relationship as shown in Table 1 below.

  In the case of corresponding to the above patterns 1 to 4, the relative speed difference setting unit 106 performs correction on the reference relative speed difference based on a predetermined correction coefficient.

  The relative speed difference setting unit 106 is connected to the relative speed difference instructing unit 110 and the period superimposing unit 112.

  Based on the input of the relative speed difference set by the relative speed difference setting unit 106, the relative speed difference instruction unit 110 instructs the drive control unit 102 of the relative speed difference between the corresponding drive systems.

  In addition, a vibration source 114 is connected to the period superimposing unit 112, and one of the relative speed differences is set based on the vibration source (for example, between the photosensitive drum 11 and the primary intermediate transfer drum 21). When a relative speed difference is set between them, the vibration pattern is read from the vibration source and sent to the relative speed difference instructing unit 110 so as to superimpose a predetermined period of vibration (for the primary intermediate transfer drum 21).

  As a result, the drive control unit 102 can apply periodic vibration to the instructed speed to the drive source.

  The operation of this embodiment will be described below.

  First, a color image printing operation by this printer will be described.

  Printing of a full color image by this color printer is generally performed as follows.

  First, after each photosensitive drum 11 of the photosensitive drum unit 2 is uniformly charged by each charging roll 12, each color of Y, M, K, C from the exposure unit 3 is applied to the surface of each charged photosensitive drum 11. Each of the laser beam lights Bm corresponding to 1 is irradiated, and an electrostatic latent image of each color corresponding to input information to the printer is formed. Next, the electrostatic latent images on the photosensitive drums 11 are developed by the developing devices 14 of the developing unit 4 and visualized as toner images of Y, M, K, and C colors.

  Subsequently, the toner images of the respective colors formed on the respective photosensitive drums 11 are primarily transferred electrostatically onto the primary intermediate transfer drums 21 and 22. That is, the yellow and magenta toner images formed on the photosensitive drums 11Y and 11M are magenta and yellow in this order on the primary intermediate transfer drum 21, and the black and cyan toner images formed on the photosensitive drums 11K and 11C are Cyan and black are sequentially transferred so as to be superimposed on the primary intermediate transfer drum 22 in this order. As a result, a multiple toner image composed of a magenta toner image and a yellow toner image is formed on the primary intermediate transfer drum 21.

  Subsequently, the toner images respectively formed on the primary intermediate transfer drums 21 and 22 are electrostatically secondarily transferred onto the secondary intermediate transfer drum 23. As a result, the toner image (M and Y from the lower layer side) on the primary intermediate transfer drum 21 and the toner image on the primary intermediate transfer drum 22 are transferred onto the secondary intermediate transfer drum 23 in this order, respectively. To Y, M, and C, a multiple toner image and a K single color toner image are formed. Next, the toner image is conveyed toward the final transfer portion where a nip portion is formed between the secondary intermediate transfer drum 23 and the final transfer roll 50 as the secondary intermediate transfer drum 23 rotates.

  Along with the formation of the toner image, the recording paper P is supplied from the paper feeding unit 6 at a predetermined timing toward the final transfer portion. That is, only one sheet of recording paper P stored in the paper feed tray 60 is sent out to the paper transport path by the paper delivery device 61 and temporarily stopped by the registration roll 68, and then is finally sent by the registration roll 68 at a predetermined timing. It is sent to the transfer section. As a result, the four color (Y, M, K, C) toner images on the secondary intermediate transfer drum 23 are transferred to the final transfer portion where the nip portion is formed by the secondary intermediate transfer drum 23 and the final transfer roll 50. It is electrostatically transferred together with the recording paper P in a pressurized state.

  Next, the recording paper P onto which the multiple toner image has been transferred is sent to the fixing unit 7, and is heated and pressed by passing through a fixing nib portion between the heating roll 71 and the pressure roll 72 of the fixing unit 7 to be fixed. After the toner image is formed, it is discharged outside the apparatus. By executing a series of image forming processes as described above, a full color image is formed on one recording sheet P.

  Here, in the present embodiment, the rotation control is performed mainly by the rotation control between the photosensitive drum 11 and the primary intermediate transfer drums 21 and 22.

  FIG. 5 is an example of a rotation control flow of each drum in the image forming apparatus of the present embodiment.

  As shown in FIG. 5, the relative speed difference between the photosensitive member and the intermediate transfer member is zero when the image is not transferred, such as when the power is turned on, during the cleaning sequence, or when the toner is replenished (supplemented). The relative speed difference is raised to a specified value after a specified time after entering, that is, immediately before the start of primary transfer, and at the same time, the relative speed difference is periodically changed.

  As described above, in the present embodiment, the transfer efficiency is improved by providing a relative speed difference at the nip portion between the photosensitive drum 11 and the primary intermediate transfer drums 21 and 22, and the relative efficiency is increased. By varying the speed difference at a predetermined period, the stick-slip occurrence period can be adjusted to a desired period, and striped image unevenness due to the stick-slip can be made inconspicuous. Further, if necessary (especially when the image is not transferred), the relative speed difference is set to 0, so that the generation of noise due to stick-slip can be eliminated.

  Next, an embodiment of the image forming apparatus of the present invention will be described.

  FIGS. 6A to 6D show the surface speeds of the photosensitive drums 11Y, 11M, 11K, and 11C and their respective values by the rotation control unit 80 shown in FIG. 3 in the color printer shown in FIGS. The specified speed ratio with the surface speed of the primary intermediate transfer drums 21 and 22 that receive the transfer of the toner image on the photosensitive drum is 1.5%, the frequency is 50 Hz and the fluctuation amount is 0 to 10% for periodic speed fluctuations. This is an example shown in the analysis diagram of the speed fluctuation FET.

  6A shows a vibration cycle of 0 Hz and a fluctuation amount of 0%. FIG. 6B shows a vibration cycle of 50 Hz and a fluctuation amount of 1%. FIG. 6C shows a vibration cycle of 50 Hz and a fluctuation amount of 5%. FIG. 6A shows the result when the vibration period is 0 Hz and the fluctuation amount is 10%.

  As can be seen in FIG. 6, irregular banding due to stick-slip, which occurred in a wide range at an irregular frequency (see FIG. 6A), is forced to slip at a frequency of 50 Hz. (See FIG. 6D). Although this state is sufficient, raising the frequency to a higher frequency makes it difficult to visually perceive image defects as high-frequency banding that is difficult for the human eye to perceive.

  In the above description, the relative speed difference is not given when the image is not transferred, but the relative speed difference is given only when the image is transferred, and the periodic variation is performed. However, variations shown in Table 2 below are considered. obtain.

1 is an internal schematic diagram of a color printer according to an embodiment of the present invention. It is a block diagram of the principal part of the color printer shown in FIG. It is a figure which shows the rotation control part which controls rotation of each drum and each drum in the color printer of this Embodiment. It is a functional block diagram of a rotation control part. It is an example of the control sequence of a rotation control part It is a result of the Example of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case 2 Photosensitive drum unit 3 Exposure unit 4 Developing unit 5 Image transfer drum unit 6 Paper feeding unit 7 Fixing unit 10 Support frame 11Y, 11M, 11K, 11C Photosensitive drum (image carrier)
12 Charging roll 12a Rotating shaft 13Y, 13M, 13K, 13C Toner temporary holding brush roll 14Y, 14M, 14K, 14C Rotating shaft 20 Support frame 21, 22 Primary intermediate transfer drum (intermediate transfer member)
23 Secondary intermediate transfer drum (intermediate transfer member)
24 Toner temporary holding brush roll 25 Collection roll 25a Bias roll 25b Cleaning blade 26 Residual toner removing unit 27, 28, 29 Rotating shaft 41Y, 41M, 41K, 41C Developing device 42 Developing roll 49Y, 49M, 49K, 49C Toner cartridge 50 Final transfer roll 60 Paper feed tray 61 Paper delivery device 66 Paper transport roll 68 Registration roll 71 Heating roll 72 Pressure roll 73 Paper discharge roll 80 Rotation control unit 100 Engine unit start instruction unit 102 Drive control unit 104 Transfer / non-transfer determination unit 106 Relative speed difference setting unit (relative speed difference forming control means)
108 environmental coefficient setting unit 110 relative speed difference indicating unit 112 period superimposing unit (relative speed difference period changing means)
114 Vibration source (relative speed difference period changing means)

Claims (8)

An image carrier on which an electrostatic latent image is formed while rotating in a predetermined direction and a toner image is formed by development, and part of the image carrier is brought into contact with the peripheral surface of the image carrier, and the image carrier is driven by a driving force of a driving unit. A transfer member that moves in the same direction as the movement direction of the body circumferential surface, and an image forming engine unit that transfers a toner image from the image carrier to the transfer member at the nip portion that is the contact position, An image forming apparatus for forming an image according to a predetermined print sequence,
A relative speed difference forming control means for controlling the driving means to form a relative speed difference between the photosensitive member and the transfer member in the nip portion at least during execution of a print sequence in the image forming engine section;
A relative speed difference period changing means for repeatedly changing the relative speed difference by the relative speed difference forming means at a predetermined period;
An image forming apparatus.   When the relative speed difference formation control unit forms a difference between the peripheral surface speed of the image carrier and the relative speed of the intermediate transfer member in the nip portion, the image forming engine unit performs image transfer and image non-transfer. 2. The image forming apparatus according to claim 1, wherein the relative speed difference is changed over time.   3. The relative speed difference formation control unit does not form a relative speed difference when the image is not transferred and forms a relative speed difference only when the image is transferred during execution of the print sequence. The image forming apparatus described.   The relative speed difference period changing unit does not execute a relative speed difference period change when an image is not transferred and executes a relative speed difference period change only when an image is transferred during execution of the print sequence. The image forming apparatus according to any one of claims 1 to 3.   The relative speed difference by the relative speed difference forming control means depends on the environmental temperature and the environmental humidity, and at least the relative speed difference is increased at low temperature, low humidity, or high temperature and high humidity, and other relative speed differences are decreased. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The transfer member is an intermediate transfer member for transferring the toner image formed on the surface of the image carrier to a recording sheet conveyed along a predetermined conveyance path separated from the peripheral surface of the image carrier. 6. The image forming apparatus according to claim 1, wherein the nip portion is a primary transfer portion, and the transfer portion to the recording paper is a secondary transfer portion.   When a color image is formed by transferring the toner images on the recording paper, a plurality of intermediate transfer bodies are arranged in series and in parallel according to the number of toner images to be superimposed. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The intermediate transfer member is
A pair of primary intermediate transfer members arranged in parallel with each other;
A single secondary intermediate transfer body that is arranged in series with the pair of primary intermediate transfer bodies and from which the toner images are transferred from the pair of primary intermediate transfer bodies, respectively.
Transfers two colors of the Y color image carrier, M color image carrier, C color image carrier, and K color image carrier onto one primary intermediate transfer member, and the other primary intermediate transfer member. 8. The image according to claim 7, wherein a full color image is transferred onto a recording sheet by transferring the other two colors onto the transfer body and transferring the four colors onto the secondary transfer body. Forming equipment.

Images