JP2011039378A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that color shift and image irregularities are caused when traveling of an intermediate transfer belt becomes unstable due to occurrence of sagging of the belt, because a toner image formed on a photoreceptor drum is transferred to a recording medium through the intermediate transfer belt in an image forming apparatus adopting an intermediate transfer system. <P>SOLUTION: The image forming apparatus includes: the intermediate transfer belt 21 which is arranged to be opposed to the photoreceptor drums 11a to 14a and to which the toner images on the photoreceptor drums are transferred; a driving roller 23 which drives and conveys the intermediate transfer belt 21; an idle roller 24 which applies prescribed tension to the intermediate transfer belt 21; a backup roller 30 which is disposed on a downstream side of the driving roller 23 and an upstream side of the idle roller 24; and a secondary transfer roller 25 which is disposed to be opposed to the backup roller 30 through the intermediate transfer belt 21 and transfers the toner image on the intermediate transfer belt 21 to recording paper 1. Circumferential speed of the secondary transfer roller 25 is set to be higher than the circumferential speed of the driving roller 23. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer that has a transfer belt that is stretched around a plurality of rollers and rotates, and forms an image on a sheet using an electrophotographic system.

  Conventionally, there has been an image forming apparatus that employs an intermediate transfer method in which a toner image on a photosensitive drum is transferred to an intermediate transfer belt and the toner image is transferred from the intermediate transfer belt to a recording medium (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 6-301297 (paragraphs 0017 to 0022, FIG. 1)

  However, since the toner image formed on the photosensitive drum is transferred to the recording medium via the intermediate transfer belt, the intermediate transfer belt is slack and the belt running of the intermediate transfer belt is unstable. Color misregistration and image distortion occurred.

An image forming apparatus according to the present invention includes:
An image carrier, a transfer belt disposed opposite to the image carrier, onto which a developer image on the image carrier is transferred, and a driving roller that stretches the transfer belt and conveys and drives the transfer belt A tension roller that stretches the transfer belt and applies tension to the transfer belt, and a tension roller that stretches the transfer belt, and is disposed downstream of the drive roller and upstream of the tension roller in the belt moving direction. An opposing member provided, and a transfer rotator that is disposed to face the opposing member via the transfer belt and transfers the developer image of the transfer belt to a medium,
The surface speed of the transfer rotator is greater than the peripheral speed of the drive roller.

  According to the present invention, the tension of the transfer belt stretched between the driving roller, the tension roller, and the opposing member can be maintained, so that the toner image transferred onto the recording paper can be expanded and contracted and transferred by each image forming unit. In addition, it is possible to prevent deterioration in print quality such as misalignment of toner images.

1 is a main part configuration diagram schematically showing a main part configuration of an image forming apparatus according to a first embodiment of the present invention; FIG. 3 is a configuration diagram illustrating an intermediate transfer belt unit together with each photosensitive drum, a secondary transfer roller, and a cleaning member of the image forming unit in the first embodiment. FIG. 2 is a control system block diagram showing a configuration of a main part of a part particularly related to the present invention in the control system of the image forming apparatus in the first embodiment. FIG. 6 is a schematic configuration diagram illustrating a main configuration of a first modification of the first embodiment in which a secondary transfer roller is urged by a backup roller via an intermediate transfer belt and a transfer belt that sucks and conveys a recording sheet. . FIG. 5 is a schematic configuration diagram showing a main configuration of a second modification of the first embodiment in which a fixed facing piece is used instead of a backup roller in the intermediate transfer belt unit of the image forming apparatus shown in FIG. 1. FIG. 5 is a configuration diagram illustrating an intermediate transfer belt unit employed in an image forming apparatus according to a second embodiment of the present invention, together with each photosensitive drum of the image forming unit. In Embodiment 2, it is principal part sectional drawing which looked at the load provision mechanism from the moving direction (arrow B direction) of transfer belt conveyance. FIG. 4 is a control system block diagram showing a main configuration of a part particularly related to the present invention in the control system of the image forming apparatus of Embodiment 2. FIG. 5 is a configuration diagram illustrating an intermediate transfer belt unit employed in an image forming apparatus according to a third embodiment of the present invention, together with each photosensitive drum of the image forming unit.

Embodiment 1 FIG.
FIG. 1 is a main part configuration diagram schematically showing a main part configuration of an image forming apparatus 100 according to the first embodiment of the present invention.

  As shown in the figure, the recording sheets 1 are stored in the sheet feeding unit 2 in a stacked state, and the sheet feeding roller 3 uses the recording sheet 1 stored in the sheet feeding unit 2 as the uppermost recording sheet 1. To the paper transport path sequentially. The conveyance roller pairs 4, 5, and 6 convey the recording sheet 1 sent out to the sheet conveyance path indicated by the alternate long and short dash line to the image transfer unit 32 described later along the conveyance path. On the other hand, the moving path of the intermediate transfer belt 21 includes an image forming unit 11 as an image carrier that forms a cyan (C) toner image, an image forming unit 12 that forms a magenta (M) toner image, and yellow (Y The image forming unit 13 for forming a toner image and the image forming unit 14 for forming a black (K) toner image are arranged in a line, and on each of the photosensitive drums 11a, 12a, 13a, and 14a, A toner image of a corresponding color is formed.

  As will be described later, the intermediate transfer belt unit 20 transfers the toner image formed by each of the image forming units 11 to 14 to the intermediate transfer belt 21 and conveys the toner image. Transfer to recording paper 1. The fixing unit 40 includes a fixing roller 43 provided with a heat source 42 inside, and a backup roller 41 urged against the fixing roller 43 by an urging means (not shown), and the recording paper 1 is between the fixing roller 43 and the backup roller 41. The toner image transferred onto the recording paper 1 is fixed by heat and pressure while passing through. The conveyance roller pair 7 conveys the recording paper 1 on which the toner is fixed to the outside of the apparatus.

  FIG. 2 is a configuration diagram showing the intermediate transfer belt unit 20 together with the photosensitive drums 11a, 12a, 13a, 14a, the secondary transfer roller 25, and the cleaning member 28 of the image forming units 11-14.

  As shown in FIG. 2, the intermediate transfer belt 21 is stretched by a drive roller 23, an idle roller 24, and a backup roller 30 so as to be able to circulate and rotate. The driving roller 23 is rotatably held by the belt frame 22 and obtains rotational force by a driving means (not shown) to circulate and rotate the intermediate transfer belt 21. A backup roller 30 as an opposing member is a belt frame as will be described later. 22 is rotatably held. An idle roller 24 as a tension roller is rotatably supported by a bearing 26 that is slidably held on the belt frame 22 in the directions of arrows A and B, and is laid between the belt frame 22 and the bearing 26. The bearing 26 is urged in the direction of arrow A by the urging member 27, so that an appropriate tension is applied to the entire intermediate transfer belt 21. The directions of arrows A and B are parallel to the moving direction of the intermediate transfer belt 21 that moves between the driving roller 23 and the idle roller 24.

  The image forming units 11 to 14 are arranged in a row facing the intermediate transfer belt 21 that moves between the drive roller 23 and the idle roller 24 of the intermediate transfer belt unit 20, and each of the photosensitive drums 11 a, 12 a, 13 a, and 14 a. The transfer rollers 15, 16, 17, and 18 are rotatably disposed via the intermediate transfer belt 21 at positions facing each other. Each of the transfer rollers 15, 16, 17, and 18 is rotatably held by a belt frame 22, and sandwiches the intermediate transfer belt 21 together with the opposing transfer rollers 15, 16, 17, and 18 by a biasing member (not shown). It is energized.

  The intermediate transfer belt 21 moves between the driving roller 23 and the idle roller 24 in the direction of arrow B, and is formed by the image forming units 11 to 14 with cyan (C), magenta (M), yellow (Y), and black. The toner images of the respective colors (K) are sequentially transferred by the transfer rollers 15-18.

  As shown in FIG. 1, the backup roller 30 is disposed along the paper conveyance path between the conveyance roller pair 6 that conveys the recording paper 1 and the fixing unit 40, and an image together with the secondary transfer roller 25 as a transfer rotator. The transfer unit 32 is configured. The secondary transfer roller 25 is rotatably arranged to face the backup roller 30 via the intermediate transfer belt 21 and is urged by the urging member 31 so as to sandwich the intermediate transfer belt 21 together with the backup roller 30. As a result, the secondary transfer roller 25 sandwiches the intermediate transfer belt 21 onto which the toner image has been transferred and the recording paper 1 sent from the conveyance roller pair 6 in synchronism with the conveyance of the toner image. The toner image 21 is transferred to the recording paper 1.

  A cleaning member 28 is disposed on the downstream side of the image transfer unit 32 in the moving direction of the intermediate transfer belt 21. The cleaning member 28 is disposed so as to face a counter roller 29 rotatably supported by the belt frame 22 via the intermediate transfer belt 21 and to come into contact with the surface of the intermediate transfer belt 21. Unnecessary toner and foreign matter adhering to the surface of 21 are collected.

  The urging member 27 is an important member that determines the tension of the intermediate transfer belt 21, but it is desirable to set the tension as low as possible in order to constantly generate tension on the intermediate transfer belt 21. If the tension is set higher than necessary, when the intermediate transfer belt unit 20 is stopped for a long time, the intermediate transfer belt 21 is curled or creeped, thereby causing a problem that the image is disturbed.

  FIG. 3 is a control system block diagram showing the configuration of the main part of the control system of the image forming apparatus 100 particularly related to the present invention.

  In the figure, an interface unit 101 is a part that takes a physical hierarchy interface with an external computer. The command / image processing unit 102 includes a print setting processing unit that transmits / receives data of the interface unit 101 and processes print information obtained from the interface unit 101. Further, the command / image processing unit 102 interprets commands and image data from the external computer side or develops them into a bitmap and outputs the image data to the LED control unit 103. The LED control unit 103 processes the image data expanded in the bitmap from the command / image processing unit 102 according to each interface of the LED head (not shown), and transmits the data to each LED head. Each LED head is provided in each of the image forming units 11 to 14 shown in FIG. 1, but detailed description thereof is omitted.

  The print control unit 104 receives information from various sensors such as a paper sensor (not shown) provided in the paper conveyance path and a temperature sensor (not shown) provided in the fixing unit 40 (FIG. 1), and information from the command / image processing unit 102. By receiving commands and the like, performing analysis, calculation, and condition determination based on these information and outputting operation instruction signals to each unit, the mechanism unit control and the applied voltage control are performed in an integrated manner.

  The print controller 104 controls the paper feed motor 108 that drives the paper feed roller 3 (FIG. 1) to feed the recording paper 1 and controls the transport motor 109 that drives the transport roller pairs 4-7 to control the paper. The recording paper 1 is transported along the transport path.

  Further, the print control unit 104 is connected to a belt drive motor 110 that drives the drive roller 23 (FIG. 1) and a rotation unit (including the photosensitive drums 11a to 14a) of each of the image forming units 11 to 14 to generate a rotational force. The drum motors 111 to 114 for driving the driving gears (not shown) to be transmitted are individually controlled to manage the driving of the intermediate transfer belt 21, the transfer rollers 15 to 18, and the rotating portions of the image forming units 11 to 14. The print control unit 104 also controls a secondary transfer motor 115 that drives the secondary transfer roller 25, and controls the rotation of the secondary transfer roller 25 related to the conveyance of the intermediate transfer belt 21.

  In addition, the print control unit 104 controls the heater so that the surface temperature of the fixing roller 43 maintains a predetermined temperature according to a detection value of a temperature sensor (not shown) that detects the surface temperature of the fixing roller 43 of the fixing unit 40 (FIG. 1). The fixing motor 119 that instructs the unit 118 and rotates the fixing roller 43 is controlled.

  The high voltage control unit 120 receives a control value from the print control unit 104 and applies a predetermined high voltage to the high voltage application unit, the transfer rollers 15 to 18, and the secondary transfer roller 25 of each of the image forming units 11 to 14. To do.

  In the above configuration, a printing operation by the image forming apparatus 100 will be described with reference to FIGS.

  The command / image processing unit 102 processes data input from the external computer, and sends a print command as a command from the external computer side to the print control unit 104. Upon receiving this command (printing command), the print control unit 104 controls the paper feed motor 108 that rotationally drives the paper feed roller 3, and transports the uppermost recording paper 1 stored in the paper feed unit 2. Send to pair 4 on paper transport path. Thereafter, the conveyance motor 109 is controlled to drive the conveyance roller pairs 4, 5, 6 at the timing when the recording sheet 1 comes into contact with the conveyance roller pair 4 and the skew is corrected, and the recording sheet 1 is transferred to the image transfer unit 32. And carry.

  On the other hand, the image data processed by the command / image processing unit 102 is sent to the LED control unit 103, and the LED control unit 103 controls the light emission of an LED head (not shown) based on this image data, and displays each image shown in FIG. An electrostatic latent image based on the image data of each color is formed on the photosensitive drums 11a, 12a, 13a, and 14a of the forming units 11, 12, 13, and 14. The electrostatic latent image is developed with toner of each color by the developing means to become a toner image, and the toner image is applied with a predetermined high voltage by the high voltage controller 120 and the photosensitive drums 11a, 12a, 13a, 14a. Then, the images are sequentially transferred onto the intermediate transfer belt 21 that is nipped and conveyed by the transfer rollers 15 to 18 that are in pressure contact with each other. The intermediate transfer belt 21 conveys the transferred toner image to the image transfer unit 32.

  When the toner image transferred to the intermediate transfer belt 21 reaching the image transfer unit 32 is joined at the image transfer unit 32 to the recording paper 1 reaching the image transfer unit 32 via the conveying roller 6, the print control unit 104 The operation timing of each unit is controlled in synchronism so as to be joined to a predetermined printing position of the recording paper 1. In the image transfer unit 32, the toner image transferred to the intermediate transfer belt 21 by the secondary transfer roller 25 applied with a predetermined high voltage by the high-voltage control unit 120 and pressed against the backup roller 30 is secondary-recorded on the recording paper 1. The recording sheet 1 transferred and transferred with the toner image is sent to the fixing unit 40 at the subsequent stage.

  In the fixing unit 40, the recording sheet 1 on which the toner image is transferred is heated and pressed by the fixing roller 43 heated to a predetermined temperature and the backup roller 41 urged by the fixing roller 43, and the toner image is recorded on the recording sheet. 1 is fixed and sent to the discharge roller 7 at the subsequent stage. Thus, the recording paper 1 on which the print image is fixed is discharged out of the apparatus by the discharge roller 7.

  Next, the operation of conveying the intermediate transfer belt 21 of the intermediate transfer belt unit 20 will be further described with reference to FIGS.

  The print control unit 104 controls the rotation of the belt drive motor 108 so that the drive roller 23 rotates in the direction of arrow C. The rotational force of the driving roller 23 is transmitted to the intermediate transfer belt 21 by the frictional force between the front surface of the driving roller 23 and the back surface of the intermediate transfer belt 21, and the intermediate transfer belt 21 circulates and rotates in the direction of arrow E. At this time, the intermediate transfer belt 21 is stretched by the idle roller 24 biased by the biasing member 27 so that a necessary and sufficient tension Ft is generated. As a result, a winding force around the driving roller 23 is generated on the intermediate transfer belt 21, and a frictional force is generated between the front surface of the driving roller 23 and the back surface of the intermediate transfer belt 21, so that the intermediate transfer belt 21 is not slipped. The belt can be circulated and rotated at a belt conveyance speed Vbd (= drive roller 23 circumferential speed). Note that the friction coefficient μ between the front surface of the driving roller 23 and the back surface of the intermediate transfer belt 21 at this time is preferably μ> 1.

  Next, the relationship between the surface peripheral speeds Vd1, Vd2, Vd3, Vd4 of the photosensitive drums 11a, 12a, 13a, 14a and the belt conveyance speed Vbd will be described.

  As described above, the intermediate transfer belt 21 is conveyed at a predetermined belt conveyance speed Vbd (for example, 150 mm / sec) under the control of the print control unit 104, and the print control unit 104 includes the photosensitive drums 11a, 12a, The drum motors 111, 112, 113, and 114 are controlled to rotate so that 13a and 14a rotate in the direction of arrow D at the surface peripheral speeds Vd1, Vd2, Vd3, and Vd4, respectively. At this time, the photosensitive drum 14a positioned upstream of the driving roller 23 in the moving direction of the intermediate transfer belt 21 is set so that the surface peripheral speed Vd4 is slower than the belt conveyance speed Vbd.

  This setting is performed in order to generate the frictional force Fd4 between the photosensitive drum 14a and the intermediate transfer belt 21 in order not to reduce the tension of the intermediate transfer belt 21 between the driving roller 23 and the photosensitive drum 14a. If the tension between the driving roller 23 and the photosensitive drum 14a decreases, the winding force around the driving roller 23 decreases, and the conveyance of the intermediate transfer belt 21 becomes unstable. Further, since the conveyance of the intermediate transfer belt becomes unstable when the tension is reduced between the photosensitive drums, the intermediate between the photosensitive drums 13a, 12a, and 11a and the intermediate drum is prevented so that the tension is not reduced between the photosensitive drums. The surface peripheral speed Vd of the upstream photosensitive drum is set to be gradually reduced so that frictional forces Fd3, Fd2, and Fd1 are generated between the transfer belts 21, respectively.

That is, the belt conveyance speed Vbd and the surface peripheral speeds Vd1 to Vd4 of the photosensitive drums 11a to 14a are set so as to satisfy the following relationship.
Vbd (150 mm / sec)> Vd4 (149.5 mm / sec)> Vd3 (149 mm / sec)> Vd2 (148.5 mm / sec)> Vd1 (148 mm / sec)
In addition, the numerical value in the parenthesis of the above formula shows an example.

  Next, the relationship between the belt conveyance speed Vbd and the surface peripheral speed Vtr of the secondary transfer roller 25 will be described. The rotational speed Vtr of the secondary transfer roller 25 located downstream of the drive roller 23 in the moving direction of the intermediate transfer belt 21 does not reduce the tension of the intermediate transfer belt 21 between the drive roller 23 and the secondary transfer roller 25. Since the frictional force Fr is generated between the intermediate transfer belt 21 and the secondary transfer roller 25, the surface peripheral speed Vtr of the secondary transfer roller 25 is set to be higher than the belt conveyance speed Vbd (Vtr> Vbd). As described above, by setting the speed of each rotating body, the tension Ft of the intermediate transfer belt 21 wound around the driving roller 23 is prevented from decreasing.

  At this time, the frictional force Fr generated between the intermediate transfer belt 21 and the secondary transfer roller 25 is intermediate between the intermediate transfer belt 21 and the secondary transfer roller 25 when the recording paper 1 is interposed between the intermediate transfer belt 21 and the secondary transfer roller 25. The friction coefficient α (> 0) between the transfer belts 21 and the friction coefficient β (> 0) between the recording paper 1 and the secondary transfer roller 25 vary depending on the magnitude of the friction coefficients α and β. Even if Vtr> Vbd, the frictional force Fr is generated in the direction in which tension is generated between the intermediate transfer belt 21 between the drive roller 23 and the secondary transfer roller 25.

  Here, a modification of the present embodiment will be described.

  FIG. 4 is a schematic diagram illustrating a main configuration of the first modification in which the secondary transfer roller 25 is urged by the backup roller 30 via the transfer belt 37 that sucks and conveys the intermediate transfer belt 21 and the recording paper 1. It is a block diagram. In the figure, the same reference numerals are given to portions common to the image forming apparatus 100 shown in FIG.

  The transfer belt 37 is stretched by the driving roller 34 and the driven roller 35 and circulates and rotates in the direction of the arrow shown in the figure, and the image is displayed while adsorbing the recording paper 1 (FIG. 1) received from the paper supply unit (not shown). It is conveyed to the transfer unit 32. In the image transfer unit 32, the secondary transfer roller 25 sandwiches the intermediate transfer belt 21 onto which the toner image has been transferred and the recording paper 1 conveyed by the transfer belt 37 in synchronization with the conveyance of the toner image. The toner image on the transfer belt 21 is transferred to the recording paper 1. As described above, Modification 1 shows an example in which the recording paper 1 is conveyed to the image transfer unit 32 by the transfer belt 37.

  FIG. 5 shows a configuration of a main part of a second modification in which a fixed opposing piece 39 is used instead of the backup roller 30 in the intermediate transfer belt unit 20 (38 in this example) of the image forming apparatus 100 shown in FIG. It is a schematic block diagram. In the figure, the same reference numerals are given to portions common to the image forming apparatus 100 shown in FIG.

  Here, the secondary transfer roller 25 is urged to the opposing piece 39 via the intermediate transfer belt 21, and in synchronization with the transfer of the toner image and the intermediate transfer belt 21 to which the toner image is transferred, The recording paper 1 sent from the conveying roller pair 6 (FIG. 1) is sandwiched at the same time, and the toner image on the intermediate transfer belt 21 is transferred to the recording paper 1. At this time, in the second modification, the intermediate transfer belt 21 slides on the surface of the opposed piece 39.

As described above, according to the image forming apparatus of the present embodiment, the relationship between the belt conveyance speed Vbd of the intermediate transfer belt 21 and the surface peripheral speeds Vd1 to Vd4 of the photosensitive drums 11a to 14a is expressed as Vbd>Vd4>Vd3>.Vd2> Vd1
And the relationship between the belt conveyance speed Vbd of the intermediate transfer belt 21 and the surface peripheral speed Vtr of the secondary transfer roller 25 is Vtr> Vbd
By setting so that the tension becomes Ft, the decrease in the tension Ft of the intermediate transfer belt 21 wound around the drive roller 23 can be prevented, so that the circulating rotation movement of the intermediate transfer belt 21 can be performed in a stable state. As a result, it is possible to prevent deterioration in print quality such as expansion and contraction of the toner image transferred onto the recording paper and misalignment of the toner images transferred by the image forming units 11, 12, 13, and 14. .

Embodiment 2. FIG.
FIG. 6 is a configuration diagram showing the intermediate transfer belt unit 60 employed in the image forming apparatus according to the second embodiment of the present invention together with the photosensitive drums 11a, 12a, 13a, and 14a of the image forming units 11 to 14. FIG. 7 is a cross-sectional view of the main part when the load applying mechanism 50 is viewed from the moving direction (arrow B direction) of the transfer belt conveyance 21.

  An image forming apparatus employing the intermediate transfer belt unit 60 is mainly different from the image forming apparatus according to the first embodiment shown in FIGS. 1 and 2 in that the image forming apparatus includes the photosensitive drums 11a, 12a, and 13a. As shown in FIG. 2, the forming units 11 to 13 have operating positions where the photosensitive drums 11a, 12a, 13a are in contact with the intermediate transfer belt 21, and as shown in FIG. 6, the photosensitive drums 11a, 12a, 13a They are configured so as to be movable to a standby position separated from the intermediate transfer belt 21 and provided with a load applying mechanism 50 upstream of the transfer roller 15 in the moving direction of the intermediate transfer belt 21.

  Therefore, in the image forming apparatus of the present embodiment that employs the intermediate transfer belt unit 60, the same reference numerals are given to the parts that are common to the image forming apparatus 100 (FIG. 1) of the first embodiment described above, or The description will be omitted while omitting the drawings, and different points will be mainly described. The main configuration of the image forming apparatus according to the present embodiment is the same as the main configuration of the image forming apparatus 100 according to the first embodiment shown in FIG. 1 except for the differences described above. Refer to

  As shown in FIGS. 6 and 7, a load roller 52 for applying a load by contacting the back side of the intermediate transfer belt 21 is rotatably held on the belt frame 22 by rotary bearings 61 and 62 (FIG. 7). The opposing roller 51 that sandwiches the load roller 52 and the intermediate transfer belt 21 is rotatably held by rotating bearings 63 and 64 (FIG. 7) that are slidably held with respect to the belt frame 22. The intermediate transfer belt 21 is urged toward the load roller 52 by urging 64 by the urging member 53. At this time, the friction coefficient μ between the surface of the load roller 52 and the back surface of the intermediate transfer belt 21 is set to μ> 1, for example, so that a large frictional force is generated between them.

  The movable portion 54a of the torque limiter 54 is coaxially fixed to the rotating shaft 52a of the load roller 52, the fixed portion 54b of the torque limiter 54 is fixed to the armature portion 55b of the electromagnetic clutch 55, and the main body 55a of the electromagnetic clutch 55 is It is fixed to the belt frame 22. Accordingly, when the main body 55a of the electromagnetic clutch 55 and the armature portion 55b are connected and fixed by ON control by an electromagnetic clutch control unit 121 (FIG. 8) described later, the torque limiter 54 operates and applies a predetermined load torque to the load roller 52. On the other hand, when the coupling and fixing of the main body 55a of the electromagnetic clutch 55 and the armature portion 55b are released by the OFF control by the electromagnetic clutch control portion 121, the torque limiter 54 itself and the armature portion 55b of the electromagnetic clutch 55 rotate together with the load roller 52. The application of the load torque to the load roller 52 by the torque limiter 54 is released.

  FIG. 8 is a control system block diagram showing the configuration of the main part of the control system of the image forming apparatus according to the present embodiment, which is particularly related to the present invention. Here, an image forming unit position control unit 120 and an electromagnetic clutch control unit 121 are added to the control system of FIG. 3 described in the first embodiment, and the other configurations are the same. Therefore, the description of the same part is omitted here, and different points are mainly described below.

  The image forming unit 120 receives a command from the print control unit 104 and controls a drive mechanism (not shown) to change the image forming units 11 to 13 including the photosensitive drums 11a, 12a, and 13a as shown in FIG. The photosensitive drums 11a, 12a, and 13a are moved to the operating position where the photosensitive drums 11a, 12a, and 13a are in contact with the intermediate transfer belt 21 and the standby positions where the photosensitive drums 11a, 12a, and 13a are separated from the intermediate transfer belt 21 as shown in FIG. To do. In response to the command from the print control unit 104, the electromagnetic clutch control unit 121 switches the electromagnetic clutch 55 between the ON control and the OFF control described above.

  The image forming apparatus of the present embodiment is configured so that a color mode and a single color (here, black (K) is assumed) mode can be set. When the monochrome mode is set, the print control unit 104 instructs the image forming unit position control unit 120 and the electromagnetic clutch control unit 121 to perform the monochrome mode control corresponding to this setting. When the image forming unit position control unit 120 receives this single color mode control instruction, the image forming units 11 to 13 including the photoconductive drums 11a, 12a, and 13a are replaced with the photoconductive drums 11a as shown in FIG. , 12a, 13a are moved to a standby position separated from the intermediate transfer belt 21.

  Further, when receiving the monochrome mode control instruction, the electromagnetic clutch control unit 121 controls the electromagnetic clutch 55 to be ON, and connects the main body 55a and the armature portion 55b of the electromagnetic clutch 55 shown in FIG. 7 to operate the torque limiter 54. A predetermined load torque is applied to the load roller 52.

  On the other hand, when the color mode is set, the print control unit 104 instructs the image forming unit position control unit 120 and the electromagnetic clutch control unit 121 to perform color mode control corresponding to this setting. When the image forming unit position controller 120 receives this color mode control instruction, the image forming units 11 to 13 including the photosensitive drums 11a, 12a, and 13a are replaced with the photosensitive drums 11a and 11a, as shown in FIG. 12a and 13a move to an operating position in contact with the intermediate transfer belt 21.

  Further, upon receiving this color mode control instruction, the electromagnetic clutch control unit 121 controls the electromagnetic clutch 55 to be OFF, releases the coupling and fixing of the main body 55a of the electromagnetic clutch 55 and the armature unit 55b, and supplies the load roller 52 by the torque limiter 54. Release the load torque. Therefore, in this color mode, the image forming apparatus of the present embodiment is substantially the same as the image forming apparatus 100 of the first embodiment.

  In the single color mode described above, the print control unit 104 operates only the image forming unit 14 that forms a black (K) toner image, and transfers the black toner image formed on the photosensitive drum 14 a to the intermediate transfer belt 21. . During this time, the image forming units 11, 12, and 13 are stopped at positions where the photosensitive drums 11 a, 12 a, and 13 a are separated from the intermediate transfer belt 21. Consumption can be prevented.

  In the above configuration, the operation of transporting the intermediate transfer belt 21 of the intermediate transfer belt unit 60 in the single color mode will be further described with reference to FIGS.

  When the photosensitive drums 11a, 12a, and 13a provided in the image forming units 11, 12, and 13 are separated from the intermediate transfer belt 21, the photosensitive drums 11a, 12a, and 13a described in the explanation of FIG. Since the frictional forces Fd1, Fd2, and Fd3 generated between the belts 21 are not generated, the tension F of the intermediate transfer belt 21 between the photosensitive drum 14a and the idle roller 24 is reduced, and the circulating rotation movement of the intermediate transfer belt 21 is unstable. become.

  In order to prevent this, in the case where printing is performed in the single color mode in the present embodiment, a load force Ftl is applied to the intermediate transfer belt 21 by the load roller 51 to which a predetermined load torque is added as described above, and photosensitive. The tension F of the intermediate transfer belt 21 is prevented from decreasing between the drum 14a and the idle roller 24, and the intermediate transfer belt 21 can be stably circulated and rotated.

  If the load application mechanism 50 is not provided, it is necessary to increase the tension Ft applied by the idle roller 24 to compensate for the decrease in tension of the intermediate transfer belt 21 in the single color mode. By providing the mechanism 50, such a response becomes unnecessary.

  As described above, according to the image forming apparatus of the present embodiment, in addition to the effects described in the first embodiment, the tension of the intermediate transfer belt 21 can be obtained even in printing in the monochrome mode that does not use the image forming units 11, 12, and 13. It is possible to prevent the lowering, and it is possible to perform a stable circular rotational movement without causing a sag in the intermediate transfer belt 21. As a result, it is possible to prevent deterioration in print quality such as image distortion caused by expansion / contraction of the toner image transferred onto the recording paper and speed change of the intermediate transfer belt 21.

  Further, when the intermediate transfer belt 21 is stopped, the tension due to the frictional forces generated when the intermediate transfer belt 21 is driven to move does not occur, and only the tension Ft applied by the idle roller 24 is generated. However, according to the image forming apparatus of the present embodiment, it is not necessary to set the tension Ft generated by the idle roller 24 for the monochrome mode as described above, and therefore the belt unit 60 can be left for a long time. Even when this is done, curling and creep of the intermediate transfer belt 21 can be minimized.

  In this embodiment, it is assumed that black printing is performed in the single color mode. However, the present invention is not limited to this, and any of other colors, cyan (C), magenta (M), and yellow (Y) is used. It is also possible to perform single color printing of these colors.

Embodiment 3 FIG.
FIG. 9 is a configuration diagram showing the intermediate transfer belt unit 70 employed in the image forming apparatus according to the third embodiment of the present invention, together with the photosensitive drums 11a, 12a, 13a, and 14a of the image forming units 11-14. It is.

  The image forming apparatus employing the intermediate transfer belt unit 70 is mainly different from the image forming apparatus according to the second embodiment employing the intermediate transfer belt unit 60 shown in FIG. 50, the intermediate transfer belt 21 is urged toward the load roller 52 by the opposing roller 51. In the present embodiment, as shown in FIG. The transfer belt 21 is urged to the opposing roller 72, and the opposing roller 72 is not provided with the torque limiter 54 and the electromagnetic clutch 55 as shown in FIG. 7, and is in a free state. is there. Therefore, in the image forming apparatus of the present embodiment that employs the intermediate transfer belt unit 70, the same reference numerals are given to the parts that are common to the image forming apparatus of the first embodiment or the second embodiment, or The description will be omitted while omitting the drawings, and different points will be mainly described.

  As shown in FIG. 9, the cleaning member 28 is disposed at a position facing the opposing roller 72 via the intermediate transfer belt 21, and a cleaning blade 28 a formed of an elastic body causes the intermediate transfer belt 21 to be opposed to the opposing roller 72. It is in contact with the surface of the intermediate transfer belt 21 so as to be biased. As a result, unnecessary toner and foreign matter adhering to the surface of the intermediate transfer belt 21 are scraped and collected, and a predetermined frictional force Fd is generated between the tip of the cleaning blade 28a and the surface of the intermediate transfer belt 21. Set to

  In the above configuration, the operation of conveying the intermediate transfer belt 21 of the intermediate transfer belt unit 70 in the single color mode will be further described with reference to FIGS. 7, 8, and 9. FIG. However, here, in the block diagram of the control system of FIG. 8, it is assumed that the electromagnetic clutch control unit 121 is removed and a command related thereto is deleted.

  In the image forming apparatus of the present embodiment, each control operation performed by the control system shown in FIG. 8 when the color mode or the single color (here, black (K)) mode is set is the control operation by the electromagnetic clutch control unit 121. Except for the point that is deleted, the control operation is exactly the same as that described in the second embodiment, and thus detailed description thereof will be omitted.

  Therefore, in the single color mode, as shown in FIG. 9, the photosensitive drums 11 a, 12 a, and 13 a are moved to standby positions that are separated from the intermediate transfer belt 21. The cleaning member 28 removes the toner remaining on the intermediate transfer belt 21 by clogging the cleaning blade 28a of the cleaning member 28 and the intermediate transfer belt 21 while rubbing them. Since the cleaning member 28 generates friction with the intermediate transfer belt 21 as described above, the cleaning member 28 becomes an element that generates tension by the circular transfer movement of the intermediate transfer belt 21.

  Accordingly, as shown in FIG. 9, a driving force is generated on the intermediate transfer belt 21 on the downstream side in the moving direction of the intermediate transfer belt 21 relative to the idle roller 24 that stretches the intermediate transfer belt 21 and generates tension. The tension Fb is added to the tension Ft applied by the idle roller 24 between the drive roller 23 and the cleaning member 28 by being arranged on the upstream side of the drive roller 23.

  When the photosensitive drums 11a, 12a, and 13a provided in the image forming units 11, 12, and 13 are separated from the intermediate transfer belt 21, the photosensitive drums 11a, 12a, and 13a described in the explanation of FIG. Since the frictional forces Fd1, Fd2, and Fd3 generated between the belts 21 are not generated, the tension F of the intermediate transfer belt 21 between the photosensitive drum 14a and the idle roller 24 is reduced, and the circulating rotation movement of the intermediate transfer belt 21 is unstable. become.

  In order to prevent this, when printing in the single color mode in the present embodiment, the tension of the intermediate transfer belt 21 between the photosensitive drum 14a and the idle roller 24 is applied by applying the tension Fb to the intermediate transfer belt 21 by the cleaning blade 28a. F is increased, and the intermediate transfer belt 21 can be stably circulated and rotated.

  When the tension Fb is not applied by the cleaning member 28, it is necessary to increase the tension Ft applied by the idle roller 24 to compensate for the decrease in the tension of the intermediate transfer belt 21 in the single color mode. By providing 28 at the above position, such a response becomes unnecessary.

  As described above, according to the image forming apparatus of the present embodiment, in addition to the effects described in the first embodiment, the tension of the intermediate transfer belt 21 can be obtained even in printing in the monochrome mode that does not use the image forming units 11, 12, and 13. It is possible to prevent the lowering, and it is possible to perform a stable circular rotational movement without causing a sag in the intermediate transfer belt 21. As a result, it is possible to prevent deterioration in print quality such as image distortion caused by expansion / contraction of the toner image transferred onto the recording paper and speed change of the intermediate transfer belt 21.

  Further, when the intermediate transfer belt 21 is stopped, the tension due to the frictional forces generated when the intermediate transfer belt 21 is driven to move does not occur, and only the tension Ft applied by the idle roller 24 is generated. However, according to the image forming apparatus of the present embodiment, since it is not necessary to set the tension Ft generated by the idle roller 24 for the monochrome mode as described above, the belt unit 70 is left for a long time. Even when this is done, curling and creep of the intermediate transfer belt 21 can be minimized.

  Further, as compared with the second embodiment, the load applying mechanism is configured by the cleaning blade 28 and the opposing roller 72 (without the torque limiter 54 and the electromagnetic clutch 55), so that the number of components can be reduced. Cost reduction.

  In each of the above-described embodiments, the case where the image forming apparatus is an electrophotographic printer has been described. However, the present invention is not limited to this, and a multifunction machine that forms an image on a recording material using an electrophotographic system, The present invention can also be applied to a facsimile machine, a copying machine, and the like.

  DESCRIPTION OF SYMBOLS 1 Recording paper, 2 Paper feed part, 3 Paper feed roller, 4 Carrying roller pair, 5 Carrying roller pair, 6 Carrying roller pair, 7 Carrying roller pair, 11 Image forming unit, 11a Photosensitive drum, 12 Image forming unit, 12a Photoconductor drum, 13 image forming unit, 13a photoconductor drum, 14 image forming unit, 14a photoconductor drum, 15 transfer roller, 16 transfer roller, 17 transfer roller, 18 transfer roller, 20 intermediate transfer belt unit, 21 intermediate transfer belt , 22 belt frame, 23 driving roller, 24 idle roller, 24a rotating shaft, 25 secondary transfer roller, 26 bearing, 27 biasing member, 28 cleaning member, 28a cleaning blade, 29 facing roller, 30 backup low , 31 urging member, 32 image transfer section, 34 drive roller, 35 driven roller, 37 transfer belt, 38 intermediate transfer belt unit, 39 facing piece, 40 fixing unit, 41 backup roller, 42 heat source, 43 fixing roller, 50 load Giving mechanism, 51 Opposing roller, 52 Load roller, 52a Rotating shaft, 53 Biasing member, 54 Torque limiter, 55 Electromagnetic clutch, 55a Main body, 55b Armature unit, 60 Intermediate transfer belt unit, 61, 62 Rotating bearing, 63, 64 Rotating bearing, 70 Intermediate transfer belt unit, 71 Load applying mechanism, 72 Opposing roller, 100 Image forming apparatus, 101 Interface unit, 102 Command / image processing unit, 103 LED control unit, 104 Print control unit, 108 paper feed motor, 109 transport motor, 110 belt drive motor, 111 drum motor, 112 drum motor, 113 drum motor, 114 drum motor, 115 secondary transfer motor, 118 heater controller, 119 fixing motor, 120 image forming unit position 121, an electromagnetic clutch control unit.

Claims (13)

An image carrier;
A transfer belt disposed opposite to the image carrier and onto which a developer image on the image carrier is transferred;
A driving roller that stretches the transfer belt and drives the transfer belt to be conveyed;
A tension roller that stretches the transfer belt and applies tension to the transfer belt;
Stretching the transfer belt, and in the belt moving direction, an opposing member disposed downstream of the drive roller and upstream of the tension roller;
A transfer rotator that is disposed to face the opposing member via the transfer belt and transfers the developer image of the transfer belt to a medium;
The image forming apparatus according to claim 1, wherein a surface speed of the transfer rotating body is greater than a peripheral speed of the driving roller.   A plurality of the image carriers are arranged in contact with the transfer belt on the upstream side of the drive roller and on the downstream side of the tension roller in the belt moving direction, and the peripheral speed of the image carrier located at the most downstream is the drive 2. The image forming apparatus according to claim 1, wherein the circumferential speed of each image carrier is set to be smaller as it is positioned upstream of the circumferential speed of the roller.   A plurality of the image carriers are arranged opposite to the transfer belt on the upstream side of the drive roller and the downstream side of the tension roller in the belt moving direction, and only a predetermined image carrier is in contact with the transfer belt. 2. The image forming apparatus according to claim 1, wherein the remaining image carrier is movable between an operating position in contact with the transfer belt and a standby position away from the transfer belt.   A load applying unit that is disposed between the tension roller and the image carrier that is positioned on the most upstream side in the belt movement direction of the plurality of image carriers, and that applies a predetermined load force to the transfer belt during belt conveyance; The image forming apparatus according to claim 3, further comprising an image forming apparatus.   5. The image forming apparatus according to claim 4, wherein the load applying unit applies the predetermined load force when the remaining image carrier is located at the standby position.   The image forming apparatus according to claim 4, wherein the load applying unit includes a first roller and a second roller that urges the transfer belt to the first roller.   The image according to claim 6, wherein the load applying unit includes a torque limiter that restricts the rotational torque of the first roller, and an electromagnetic clutch that validates or invalidates the rotational torque restriction by the torque limiter. Forming equipment.   The image forming apparatus according to claim 4, wherein the load applying unit includes a cleaning blade that is disposed in contact with an outer peripheral surface of the transfer belt and removes toner remaining on the transfer belt.   The image forming apparatus according to claim 1, wherein the tension roller biases the inside of the transfer belt by a biasing unit.   The image forming apparatus according to claim 1, wherein the facing member is a facing roller that is rotatably held.   The image forming apparatus according to claim 1, wherein the facing member is a facing piece fixed inside the transfer belt.   The image forming apparatus according to claim 1, wherein the transfer rotator is a roller-like member that is rotationally driven.   12. The image forming apparatus according to claim 1, wherein the transfer rotator is an endless belt member that is circulated and rotated.

Images