JP6634759B2 - Transfer device and image forming device - Google Patents

Description

  The present invention relates to a transfer device and an image forming device.

  Patent Document 1 discloses a transfer member that transfers a toner image on an intermediate transfer member onto a recording medium, an opposing member that is arranged to contact the transfer member with pressure via the intermediate transfer member, and a transfer member that transfers the toner image. A pressure is applied to the transfer member via the intermediate transfer member at a position upstream of the contact portion contacting the member with pressure in the moving direction of the intermediate transfer member and immediately after the toner image on the intermediate transfer member starts to contact the recording medium. And a preload member arranged to be in contact with the transfer device.

JP 2013-19934 A

  An object of the present invention is to provide a transfer device capable of changing a contact state between a belt and a medium.

The transfer device according to the first aspect has an endless shape, a belt that rotates while holding an image, a contact portion that contacts an inner periphery of the belt, and is conveyed with the belt sandwiched by the contact portion. A transfer unit that transfers an image held by the belt to a medium to be transferred, and a moving unit that is disposed on the inner peripheral side of the belt and moves to change the length of the belt wound around the transfer unit. ing.

The transfer device according to a second aspect is the transfer device according to the first aspect , wherein the moving unit includes: medium information of a medium transferred by the transfer unit; image information of an image held by the belt; Moving based on at least one of the information on the circling speed and the information set by the user, the wrapping length of the belt around the transfer unit is changed.

The transfer device according to a third aspect is the transfer device according to the first aspect or the second aspect , wherein the moving unit is configured to set the winding length longer than when the moving unit is disposed at the first position and the first position. When the medium to which the image is transferred has a smoothness of 9000 seconds or more and the image held by the belt includes a fine line pattern of a predetermined interval or less, the moving unit is moved to the second position to be elongated. An image is transferred to the transfer unit by arranging the transfer unit at the second position.

Transfer apparatus according to a fourth aspect, there is provided a transfer device from a first aspect according to any one aspect of the third embodiment, the moving part, than when it is placed in the first position and the first position When the medium on which the image is transferred has a smoothness of less than 9000 seconds and the medium has a predetermined basis weight or more, the moving unit is moved to the second position where the winding length is increased. At one position, the image is transferred to the transfer section.

Transfer apparatus according to a fifth aspect is a transfer apparatus according to any one aspect of the fourth embodiment from the first embodiment, so that the range in which the tension of the belt before and after the movement of the moving portion is defined An adjusting member for adjusting the tension is provided.

An image forming apparatus according to a sixth aspect includes a transfer device according to any one of the first to fifth aspects , a forming unit that forms an image held by the belt, and a transfer unit that is transferred to a medium by the transfer device. A fixing device for fixing an image to a medium.

An image forming apparatus according to a seventh aspect is the image forming apparatus according to the sixth aspect, further comprising: a setting device for setting a position where the moving unit is arranged by a user, wherein the moving unit is configured to perform the moving by the user. The wrapping length is changed according to the setting of the setting device.

An image forming apparatus according to an eighth aspect is the image forming apparatus according to the sixth aspect or the seventh aspect , wherein the forming unit is capable of forming an image composed of a plurality of colors and is held by the belt Measuring the shift between the single-color images constituting the multi-color images, adjusting means for adjusting the skew of the belt so as to reduce the size of the shift, and moving the moving unit to perform the adjustment Means for adjusting the skew of the belt.

The transfer device according to the first aspect can change the contact state between the belt and the medium.

The transfer device according to the second aspect is based on at least one of information of medium information of a medium transferred by a transfer unit, image information of an image held by the belt, information of a circling speed of the belt, and information set by a user. Thus, the contact state between the belt and the medium can be changed.

In the transfer device according to the third aspect, when the medium onto which the image is transferred has a smoothness of 9000 seconds or more and the image held by the belt includes a thin line pattern of a predetermined interval or less, the moving unit is moved to the first position. Compared with a transfer device that arranges and transfers an image to a transfer unit, toner particles forming a fine line pattern are less likely to scatter.

The transfer device according to the fourth aspect, when the medium to which the image is transferred has a smoothness of less than 9000 seconds and the medium has a basis weight or more, arranges the moving unit at the second position, and Microsmear is suppressed as compared with a transfer device that transfers an image.

The transfer device according to the fifth aspect has a smaller belt tension difference before and after the movement of the moving unit than a transfer device that does not adjust the belt tension before and after the movement of the moving unit.

The image forming apparatus according to the sixth aspect can form an image by changing the contact state between the belt and the medium.

In the image forming apparatus according to the seventh aspect , the moving unit can move to change the contact state between the belt and the medium according to the setting of the setting device by the user.

In the image forming apparatus according to the eighth aspect , the forming unit is capable of forming an image composed of a plurality of colors, and measures a shift between the respective monochromatic images constituting the images of the plurality of colors formed on the belt, An adjusting unit that adjusts the skew of the belt so as to reduce the magnitude of the deviation, and a position of the moving unit as compared with an image forming apparatus that moves the moving unit after the adjusting unit adjusts the skew of the belt. The registration deviation on the belt due to the change of the position is suppressed.

FIG. 2 is a schematic diagram (front view) of the image forming apparatus of the present embodiment. FIG. 3 is a schematic diagram (front view) of the periphery of a secondary transfer unit in the transfer device of the present embodiment, showing a state in which a winding roll is disposed at a first position. FIG. 4 is a schematic diagram (front view) of the periphery of a secondary transfer unit in the transfer device of the present embodiment, showing a state in which a winding roll is disposed at a second position. FIG. 5 is a schematic diagram (front view) of a periphery of a secondary transfer unit in the transfer device of the reference example. 5 is a flowchart for selecting a mode (normal mode and special mode) in an image forming operation by the image forming apparatus of the present embodiment. FIG. 5 is a schematic diagram (front view) of a periphery of a secondary transfer unit in the transfer device of the first comparative embodiment. 9 is a graph illustrating a relationship between a position of an intermediate transfer belt and a static load in a secondary transfer unit according to a first comparative example. FIG. 4 is a schematic diagram illustrating a mechanism in which toner particles are scattered in a nip of a secondary transfer portion. 6 is a graph showing a relationship between a position of the intermediate transfer belt at a secondary transfer portion and a static load in a state where the intermediate transfer belt is wound around the secondary transfer belt by a winding roll. 9 is a graph showing a relationship between a position of an intermediate transfer belt in a secondary transfer portion having a different winding length and a static load. 6 is a graph showing a relationship between a length of the intermediate transfer belt wound around the secondary transfer belt and a scattering amount of toner particles in a fine line pattern. FIG. 9 is a schematic view (front view) of the periphery of a secondary transfer unit in a transfer device according to a second comparative embodiment. 6 is a graph showing the relationship between the length of the intermediate transfer belt wrapped around the secondary transfer belt and microsmear.

≪Overview≫
Hereinafter, a mode for carrying out the present invention (hereinafter, referred to as the present embodiment) will be described. First, the overall configuration of the image forming apparatus 10 (see FIG. 1) of the present embodiment will be described. Next, the configuration of the transfer device 30 (see FIG. 1), which is a main part of the present embodiment, will be described. Next, an image forming operation by the image forming apparatus 10 of the present embodiment will be described. Next, the operation of the present embodiment will be described.

  In the following description, the directions indicated by arrows X and -X in the drawings are defined as the device width direction, and the directions indicated by arrows Y and -Y are defined as the device height direction. Further, a direction (arrow Z and arrow -Z direction) orthogonal to each of the apparatus width direction and the apparatus height direction is defined as the apparatus depth direction.

<< Overall configuration of image forming apparatus >>
As shown in FIG. 1, the image forming apparatus 10 includes an electrophotographic method including a toner image forming unit 20, a transfer device 30, a transport device 40, a fixing device 50, and a control unit 60. Device.

<Toner image forming section>
The toner image forming unit 20 has a function of performing charging, exposing, and developing processes to form a toner image G held by an intermediate transfer belt TB (hereinafter, referred to as a belt TB), which is included in the transfer device 30 and described later. Have. Here, the toner image forming unit 20 is an example of a forming unit. The toner image is an example of an image.

  The toner image forming section 20 forms a single color toner image G of a different color (Y (yellow), M (magenta), C (cyan), K (black)) on each photoconductor 22Y, 22M, 22C, 22K. Units 21Y, 21M, 21C and 21K are provided. Further, the toner image forming section 20 can form a toner image G composed of a plurality of colors according to image data. The single-color units 21Y, 21M, 21C, and 21K have the same configuration except for the color of the toner image G formed by each. Hereinafter, when it is not necessary to distinguish the single-color units 21Y, 21M, 21C, 21K and the components thereof, the description will be made with the alphabets (Y, M, C, K) of the single-color units 21Y, 21M, 21C, 21K omitted. Each single-color unit 21 is configured to include a photoconductor 22, a charging device 24, an exposure device 26, and a developing device 28. Note that, in FIG. 1, reference numerals of components of the single-color unit 21 other than the single-color unit 21K are omitted.

<Transfer device>
The transfer device 30 has a function of holding the toner image G of each color formed by each unit unit 21 and transferring the toner image G to the transported medium P. The configuration of the transfer device 30 will be described later.

<Transport device>
The transport device 40 has a function of transporting the medium P so that the medium P passes through a nip N2 described later and a nip N3 described later. The transfer device 40 includes a tray 42 and a plurality of transfer rolls 44. The tray 42 of the present embodiment is capable of individually storing a plurality of types of media P. The plurality of transport rolls 44 transport the medium P stored in the tray 42 along a transport path (dashed line in FIG. 1).

<Fixing device>
The fixing device 50 has a function of fixing the toner image G transferred (secondarily transferred) to the medium P by the transfer device 30 at the nip N3.

<Control unit>
The control unit 60 has a function of controlling each unit of the image forming apparatus 10 other than the control unit 60. For example, the control unit 60 controls each unit other than the control unit 60 (performs each unit to perform each operation) according to job data received from an external device (not shown). Here, the job data includes image data (image information) that causes each single-color unit 21 to form the toner image G, data on the type of the medium P onto which the toner image G is transferred, and other data necessary for the image forming operation. Have been. The function of the control unit 60 will be described later in the description of an image forming operation using the image forming apparatus 10.

  The above is the description of the overall configuration of the image forming apparatus 10 of the present embodiment.

≫Configuration of main part (transfer device) ≫
Next, the configuration of the transfer device 30 will be described in detail with reference to the drawings.

  As shown in FIG. 1, the transfer device 30 includes a belt TB, four transfer rolls 32, a drive roll 34, a secondary transfer unit 36, and a tension roll 38 (hereinafter, referred to as a roll 38). It is comprised including.

<Belt, four transfer rolls and drive roll>
The belt TB is endless. The four transfer rolls 32 form a nip N1 with each of the photoconductors 22 with the belt TB interposed therebetween. Then, a voltage (primary transfer voltage) is applied from a power supply (not shown) to each transfer roll 32 so that the toner image G of each color formed on each photoconductor 22 is primarily transferred to the belt TB. It has become. The drive roll 34 rotates the belt TB in the direction of the arrow R1 while rotating around its axis by a drive source (not shown). With the above-described configuration, the belt TB is driven by the driving rolls 34 and circulates in the direction of arrow R1 while holding the toner images G of the respective colors primarily transferred from the single-color units 21.

<Secondary transfer unit>
The secondary transfer unit 36 has a function of secondary-transferring the toner images G of each color held by the belt TB to a medium P that is transported by the transport device 40 and passes through a nip N2 described later. As shown in FIGS. 1, 2, and 3, the secondary transfer unit 36 includes a belt unit 70, a facing roll 80, and a moving roll 90.

[Belt unit]
The belt unit 70 has a function of transferring (secondary transfer) the toner image G held by the belt TB to a medium P conveyed to a nip N2 described later with the belt TB sandwiched between the opposed rolls 80. Here, the belt unit 70 is an example of a transfer unit. 1, 2 and 3, the belt unit 70 includes a secondary transfer belt CB (hereinafter, referred to as a belt CB), a first roll 72, and a second roll 74. . Note that the belt unit 70 is disposed below the belt TB in the apparatus height direction.

  The belt CB is endless and has conductivity. The first roll 72 is arranged on the inner peripheral side of the belt CB and is driven by a drive source (not shown) to rotate around the axis (in the direction of arrow R2) in a state where the belt CB is wound. ing. The first roll 72 is connected to a housing (not shown) of the image forming apparatus 10 and is grounded. The second roll 74 is disposed on the inner peripheral side of the belt CB, and is configured to follow the belt CB while applying tension to the belt CB by pressing the belt CB from the inner peripheral side. With the configuration described above, when the first roll 72 rotates around the axis (about the axis O), the belt CB is wound around the first roll 72 and the second roll 74 in the direction of arrow R3. It has become. Note that the belt CB is in contact with the outer periphery of the belt TB at a portion wound around the first roll 72.

[Counter roll]
As described above, the opposing roll 80 has a function of transferring (secondary transfer) the toner image G held by the belt TB to the medium P conveyed to the nip N2 described later with the belt TB sandwiched between the belt unit 70 and the belt unit 70. . The opposing roll 80 is in contact with the inner periphery of the belt TB, as shown in FIGS. 1, 2, and 3. The opposing roll 80 rotates while following the belt TB. Here, the opposing roll 80 is an example of a contact portion. The opposing roll 80 forms a nip N2 between the belt CB and the belt TB. Here, the nip N2 refers to a portion where the belt TB whose inner periphery is in contact with the opposing roll 80 and the belt CB whose inner periphery is in contact with the first roll 72 are in contact. Specifically, in FIGS. 2 and 3, the nip N2 is surrounded by an angle θ1 about the axis O of the first roll 72 in a portion where the outer circumference of the belt TB and the outer circumference of the belt CB are in contact. Part. Note that the opposing roll 80 is disposed at a position offset with respect to the first roll 72.

  In addition, a voltage (secondary transfer voltage) is applied to the opposing roll 80 from a power supply (not shown) via a power supply roll (not shown) that comes into contact with the outer periphery thereof.

  With the above configuration, when a secondary transfer voltage is applied to the opposing roll 80, the belt CB and the belt TB form an electric field for secondary transfer of the toner image G to the medium P in the nip N2. . As a result, the belt unit 70 transfers the toner image G held by the belt TB to the medium P passing through the nip N2 together with the opposing roll 80.

[Move roll]
The moving roll 90 has a function of winding the belt unit 70 (or the belt CB) around a portion (pre-nip PN described later) of the belt TB other than the portion forming the nip N2 (see FIGS. 2 and 3). . The moving roll 90 has a function of moving to change the length of the belt TB wound around the belt unit 70 (or the belt CB). Here, the moving roll 90 is an example of a moving unit. The winding length refers to the circumferential length of the outer circumference of the belt TB that is in contact with the outer circumference of the belt CB when viewed from the apparatus depth direction (the axial direction of the first roll 72). As shown in FIGS. 1, 2, and 3, the moving roll 90 is located upstream of the nip N2 and downstream of the toner image forming unit 20 in the circumferential direction of the belt TB, and Is arranged on the inner peripheral side of the.

  The moving roll 90 can be moved to a plurality of positions (for example, two positions) in the apparatus height direction. Specifically, the moving roll 90 moves in the device height direction by rotating the cam 92 driven by the control unit 60, and moves to the first position (see the position of the moving roll 90 in FIGS. 1 and 2). ) And a second position below the first position in the apparatus height direction (see the position of the moving roll 90 in FIG. 3). In addition, as shown in FIGS. 2 and 3, the belt TB is wound around the moving roll 90 of the present embodiment even when the belt is disposed at one of the first position and the second position. Have been.

  Here, as described above, the moving roll 90 has a function of winding a pre-nip PN described later around the belt unit 70. Specifically, as shown in FIGS. 2 and 3, when the moving roll 90 is disposed at one of the first position and the second position, the belt TB is attached to the belt CB by the first roll. The belt CB is wound around an outer peripheral portion of the belt CB surrounded by an angle θ2 about the axis O of 72. In the following description, this portion is referred to as a pre-nip PN (see FIGS. 2 and 3). Here, the angle θ2 changes with the movement of the moving roll 90. That is, the angle θ2 and the winding length of the pre-nip PN are variables. Note that the transfer device 30C (secondary transfer unit 36C) of FIG. 4 of the reference example described later does not include the moving roll 90, so that the pre-nip PN is not formed.

  In addition, when the moving roll 90 is located at the first position, the wrap length of the pre-nip PN is 1.5 mm as an example (see FIG. 2). On the other hand, when the moving roll 90 is located at the second position, the wrap length of the pre-nip PN is 2.5 mm as an example (see FIG. 3). That is, the moving roll 90 is moved, and the winding length of the pre-nip PN is changed in accordance with being disposed at one of the first position and the second position, thereby winding the belt TB around the belt CB. The length is changed. Specifically, when the moving roll 90 is disposed at the second position than when it is disposed at the first position, the moving roll 90 has a longer winding length. The detailed functions of the moving roll 90 will be described in the description of the image forming operation of the image forming apparatus 10.

<Tension roll>
The roll 38 has a function of applying tension to the belt TB. The roll 38 moves together with the cam 39 driven by the controller 60 before and after the movement of the movable roll 90 (before and after movement from one of the first position and the second position to the other position). It has a function of adjusting the tension of the belt TB so that the tension of the TB falls within a predetermined range. Here, the mechanism including the roll 38 and the cam 39 is an example of an adjustment member.

  The roll 38 is disposed on the inner peripheral side of the belt TB, as shown in FIG. Then, the roll 38 is driven by the belt TB while being pressed by a spring (not shown) and in contact with the inner periphery of the belt TB. The cam 39 moves the combination of the roll 38 and the spring in the apparatus width direction.

  Further, the roll 38 (and the spring) can be moved to a plurality of positions (for example, two positions) in the apparatus width direction by rotating the cam 39 driven by the control unit 60, and the reference position (see FIG. (The position of one roll 38) and a position (change position) on the left side in the device width direction from the reference position when viewed from the front side. Specifically, the roll 38 is arranged at the reference position when the moving roll 90 is arranged at the first position, and is arranged at the change position when the moving roll 90 is arranged at the second position. Has become. That is, when the moving roll 90 moves from the first (second) position to the second (first) position, the roll 38 is changed from the reference (change) position by rotating a cam driven by the control unit 60. It moves to the (reference) position. Note that the distance that the roll 38 moves from the reference position to the change position is equivalent to the distance that the moving roll 90 moves from the first position to the second position.

  With the above configuration, the roll 38 moves so that the length of the orbit of the belt TB is equal before and after the movement of the moving roll 90. In other words, the mechanism including the roll 38 and the cam 39 is provided between the movable roll 90 and the movable roll 90 so that the tension of the belt TB is within a predetermined range (compared to the case where the roll 38 cannot always be moved from the reference position). The difference in tension between the belt TB before and after the movement of the belt 90 is small.)

<Supplement>
In the transfer device 30 (and the image forming device 10) of the present embodiment, the moving roll 90 and the roll 38 are moved as shown in FIG. 1 during a period during which an image forming operation described below is not performed, that is, during a standby period. Are disposed at the first position and the reference position, respectively. Then, in the case of a later-described special mode during the image forming operation, the moving roll 90 moves from the first position to the second position, and the roll 38 moves from the reference position to the change position (see FIG. 2 and FIG. 2). (See FIG. 3).

  The above is the description of the configuration of the transfer device 30.

<< Operation of Image Forming Apparatus >>
Next, the operation of the image forming apparatus 10 of the present embodiment will be described with reference to FIGS. 1, 2, 3, and 5. FIG. The control unit 60 of the present embodiment selects one of two different modes (normal mode and special mode) according to the job data sent to the control unit 60 from an external device (not shown). Then, the respective units of the image forming apparatus 10 other than the control unit 60 are controlled, and the respective units perform the image forming operation.

  Here, the normal mode includes a thin line pattern in which the medium P onto which the toner image G is transferred has a smoothness of 9000 seconds or more and the toner image G held by the belt TB is equal to or less than a predetermined interval (hereinafter, a special line pattern). This is a mode other than the condition.) In this case, the moving roll 90 is located at the first position as shown in FIGS. On the other hand, the special mode is a mode other than the normal mode, that is, a mode in which a special condition is satisfied. In this case, the moving roll 90 is located at the second position as shown in FIG. In addition, a thin line pattern having a width equal to or less than a predetermined interval is formed by a plurality of thin lines formed along a width direction of the medium P (a direction orthogonal to a direction in which the medium P is transported) at intervals of 2.5 mm or less as an example. It is a lined pattern. The smoothness is a value obtained according to JIS P 8119.

  When the data of the type of the medium P and the image data included in the job data do not satisfy the special condition, the control unit 60 controls each unit of the image forming apparatus 10 other than the control unit 60 in the normal mode, and controls A forming operation is performed (see FIG. 5). On the other hand, when the data of the type of the medium P and the image data included in the job data satisfy the special condition, the control unit 60 controls each unit of the image forming apparatus 10 other than the control unit 60 in the special mode. The respective parts perform an image forming operation (see FIG. 5). Here, the data of the type of the medium P is an example of medium information of the medium P.

<In case of normal mode>
The control unit 60 that has received the job data from the external device (not shown) operates the toner image forming unit 20, the transfer device 30, the transport device 40, and the fixing device 50.

  Along with the above operation, in the toner image forming section 20, each charging device 24 charges each photoconductor 22, then each exposure device 26 exposes each photoconductor 22 (forms a latent image), and then, The developing device 28 develops the latent image on each photoconductor 22 as a toner image G. As a result, each toner image G is formed on each photoconductor 22.

  Next, a voltage (primary transfer voltage) is applied to each transfer roll 32 from a power supply (not shown). The drive roll 34 driven by a drive source (not shown) causes the belt TB to circulate in the circling direction (the direction of the arrow R1). As a result, the toner image G of each color is primarily transferred to the belt TB.

  Further, the transport device 40 sends the medium P to the nip N2 at the timing when the toner images G of each color held on the circling belt TB arrive at the nip N2 together with the belt TB. Further, a voltage (secondary transfer voltage) is applied from a power supply (not shown) to a power supply roll (not shown) that comes into contact with the outer periphery of the opposing roll 80. As a result, the toner image G of each color is secondarily transferred to the medium P passing through the nip N2.

  Next, the transport device 40 sends the medium P on which the toner images G of the respective colors are secondarily transferred to the nip N3. As a result, the toner images G of each color are fixed on the medium P passing through the nip N3 by the fixing device 50. Then, the medium P on which the toner images G of the respective colors are fixed (the medium P on which the image is formed) is discharged out of the image forming apparatus 10 by the transport device 40, and the image forming operation in the normal mode by the image forming apparatus 10 is performed. Ends.

  The above is the description of the image forming operation in the normal mode.

<Special mode>
Next, an image forming operation in the special mode will be described. In the following description, portions different from those in the normal mode will be described.

  When the control unit 60 that has received the job data from the external device (not shown) operates the transfer device 30, the control unit 60 rotates the cam (not shown) to move the moving roll 90 from the first position to the second position. Move to Further, the control unit 60 rotates a cam (not shown) to move the roll 38 from the reference position to the change position.

  Next, the control unit 60 operates the toner image forming unit 20, the transfer device 30, the transport device 40, and the fixing device 50 to form an image on the medium P as in the case of the normal mode. Then, after the medium P on which the toner images G of the respective colors are fixed is discharged out of the image forming apparatus 10, the control unit 60 moves the moving roll 90 from the second position to the first position and the roll 38 from the changed position. The image forming apparatus 10 is moved to the reference position, and the image forming operation in the special mode by the image forming apparatus 10 ends.

  The above is the description of the image forming operation in the special mode. The above is the description of the image forming operation by the image forming apparatus 10 of the present embodiment.

≪action≫
Next, the operation (first to fourth operations) of the present embodiment will be described.

<First operation>
The first operation is an operation in which the transfer device 30 of the present embodiment includes the moving roll 90. The first operation will be described with reference to the drawings in comparison with a first comparative example assumed below. In the description of the first comparative embodiment, when using the same components and the like as those used in the present embodiment, the reference numerals of the components and the like are used as they are even if they are not shown.

  As shown in FIG. 6, the transfer device 30A according to the first comparative example does not include the moving roll 90, but includes the driven roll 90A fixed at the first position. Therefore, in the case of the first comparative example, the same pre-nip PN as that in the present embodiment in which the moving roll 90 is arranged at the first position is always formed. The transfer device 30A (image forming device 10A) of the first comparative embodiment has the same configuration as the transfer device 30 (image forming device 10) of the present embodiment except for the above points.

  In the case of the first comparative example, the winding length of the pre-nip PN cannot be changed. That is, in the case of the first comparative example, the length of the belt TB wound around the belt CB cannot be changed. In addition, the winding length of the pre-nip PN in the case of the first comparative embodiment is equal to the winding length of the pre-nip PN when the moving roll 90 is disposed at the first position in the present embodiment.

  On the other hand, as shown in FIGS. 1, 2 and 3, the transfer device 30 of the present embodiment moves and moves the transfer roll 90 disposed at one of the first position and the second position. It has. Specifically, in the transfer device 30 of the present embodiment, as an example, the moving roll 90 moves the first position and the second position depending on whether the data of the type of the medium P and the image data included in the job data satisfy the special condition. It is arranged at one of two positions. Therefore, the transfer device 30 of the present embodiment can change the length of the belt TB wound around the belt unit 70 (belt CB).

  Therefore, the transfer device 30 of the present embodiment can change the contact state between the belt TB and the medium P. Further, according to the transfer device 30 of the present embodiment, the contact state between the belt TB and the medium P can be changed based on the data of the type of the medium P to which the toner image G is transferred and the image data. Accordingly, the image forming apparatus 10 of the present embodiment can form an image by changing the contact state between the belt TB and the medium P. The contact state between the belt TB and the medium P is defined as the pressure applied to the medium P from the belt TB when the medium P passes through the belt unit 70 (belt CB) where the belt TB is wound, and the deformation of the medium P. Condition, the posture of the medium P, and other states.

<Second operation>
The second operation is that, in the transfer device 30 of the present embodiment, when the moving roll 90 can be moved to the first position and the second position, and when a special condition is satisfied, the moving roll 90 is moved to the second position. And transferring the toner image G to the medium P. The second operation will be described by comparing the present embodiment with the above-described first comparative embodiment.

  As described above (as shown in FIG. 6), the transfer device 30A of the first comparative embodiment cannot change the length of the belt TB wound around the belt CB.

  Here, according to the test and research of the inventor of the present application, the following problems occur when the transfer operation (image forming operation) is performed using the transfer device 30A (image forming device 10A) of the first comparative embodiment. Was found. That is, when the toner image G including the fine line pattern having a predetermined interval or less is transferred to the medium P having a smoothness of 9000 seconds or more using the transfer device 30A of the first comparative embodiment, the toner image G transferred to the medium P is transferred. (In this case, toner particles are scattered in the fine line pattern toner image). Further, the scattering amount of the toner particles tends to increase as the process speed (transport speed of the medium P) is higher, the interval between the fine line patterns is shorter, and the smoothness of the medium P is higher (that is, the smoothness is higher). .

  Next, a mechanism that causes the above problem will be described with reference to FIGS. 7 and 8. FIG. 7 shows the nip N2 of the belt TB (belt CB) and the pressure before and after the nip N2 in the case of the first comparative example. As shown in FIG. 7, it can be seen that the pressure rapidly increases from the nip N2 (see the portion surrounded by the broken line). FIG. 8 is a schematic diagram showing the forces (the cohesion force F1 and the fluid force F2 between toner particles) acting on the nip N2 and the toner image G on the upstream side thereof in the case of the first comparative embodiment. In the case of the first comparative example, a space ES is formed at a timing near the entrance of the nip N2 between the fine line G1 on the upstream side of the toner image G forming the fine line pattern and the fine line G2 adjacent to the fine line G1. . Then, the volume of the space ES rapidly decreases with the rotation of the belt TB. Then, the air in the space ES is rapidly compressed, and a force (fluid force F2) is applied to the thin line G2 in a direction opposite to the direction in which the belt TB rotates. That is, the fluid force F2 refers to a force generated when air in the space ES is compressed. On the other hand, the toner particles constituting the thin line G2 are aggregated by applying an electrostatic force or the like to each other. That is, the toner particles adhere to each other with a cohesive force F1. However, when the fluid force F2 becomes larger than the cohesive force F1, it is estimated that the toner particles are scattered. The faster the process speed, the larger the fluid force F2, the shorter the interval between the fine line patterns, the easier the space ES is formed, and the higher the smoothness of the medium P (that is, the higher the smoothness), the more the air in the space ES is compressed. The above guess is considered to be valid because it can be said that it is easy to escape (it is difficult to escape).

  On the other hand, in the case of the present embodiment, the moving roll 90 can be moved to the first position and the second position, and when a special condition is satisfied, as shown in FIG. At the second position to transfer the toner image G onto the medium P. In the case of the present embodiment, unlike the case of the first comparative example, the winding length of the pre-nip PN is formed long.

  Here, FIG. 9 shows the nip N2 of the belt TB (belt CB) and the pressure before and after the nip N2 when the pre-nip PN is formed. Comparing the graph of FIG. 9 with the graph of FIG. 7, in the case of FIG. 9, the pre-nip PN is shifted from the entrance of the portion where the belt TB is wound around the belt CB (that is, the entrance of the pre-nip PN). It can be seen that the rate of increase in pressure is low over the outlets (see the portions surrounded by broken lines in FIGS. 7 and 9). This is considered to be due to the formation of the pre-nip PN in the case of FIG.

  Further, the inventor of the present application determines the arrangement of the moving roll 90 as a parameter (the winding length of the pre-nip PN is 1.5 mm, 2.0 mm, and 2.5 mm) for the medium P having a smoothness of 9000 seconds or more. A test was performed to transfer a toner image G including a fine line pattern having a distance equal to or less than the set interval. FIG. 10 shows the nip N2 of the belt TB (belt CB) and the pressures before and after the nip N2 at the pre-nip PN of each winding length. FIG. 11 shows the results of a test of the amount of toner particles scattered in the case of the pre-nip PN of each winding length in FIG. 10 and in the case of the first comparative example in which the pre-nip PN is not formed. Here, the scattering amount of the toner particles was determined by preparing a sample in which a toner image G including a thin line pattern having a spacing equal to or less than a predetermined interval was transferred to a medium P having a smoothness of 9000 seconds or more under the conditions of the pre-nip PN of each winding length. The amount of scattered toner particles was counted (using a microscope). According to FIG. 11, it was found that the longer the winding length of the pre-nip PN, the smaller the scattering amount of the toner particles. As a result, the longer the pre-nip PN, the lower the position of the moving roll 90 in the apparatus direction, so that the rate of change in the volume of the space ES decreases. That is, it is assumed that the longer the pre-nip PN, the smaller the fluid force F2 becomes, the more difficult it is for the fluid force F2 to become larger than the cohesive force F1, and the more difficult it is for toner particles to be scattered (the opposite interpretation of the mechanism assumed above).

  Therefore, the transfer device 30 of the present embodiment sets the winding length of the pre-nip PN to the first position when transferring the toner image G including the fine line pattern having a predetermined interval or less to the medium P having a smoothness of 9000 seconds or more. The toner particles forming the fine line pattern are less likely to be scattered than a transfer device that cannot be changed to a length longer than the winding length of the pre-nip PN when the moving roll 90 is disposed at the position.

  In other words, the transfer device 30 of the present embodiment transfers the toner image G including the fine line pattern having a predetermined interval or less to the medium P having a smoothness of 9000 seconds or more, at the first position and the second position. Compared to a transfer device that includes a movable roll 90 that is movable, and the movable roll 90 is disposed at the first position, the toner particles that form the fine line pattern are less likely to scatter than a transfer device that transfers the toner image G to the medium P. It can be said that.

<Third operation>
The third operation is that, in the transfer device 30 of the present embodiment, when the moving roll 90 can be moved to the first position and the second position and the special condition is not satisfied, the moving roll 90 is moved to the first position. This is an operation of transferring the toner image G to the medium P while disposing the toner image G on the medium P (with the first position). The third operation will be described by comparing the present embodiment with a second comparative embodiment assumed below. In the description of the second comparative embodiment, when the same components and the like as those used in the present embodiment are used, the symbols of the components and the like are used as they are even if they are not shown.

  As shown in FIG. 12, the transfer device 30B of the second comparative example does not include the moving roll 90, but includes a driven roll 90A fixed at the second position. Therefore, in the case of the second comparative example, the same pre-nip PN as that in the present embodiment in which the moving roll 90 is disposed at the second position is always formed. The transfer device 30B (image forming device 10B) of the second comparative example has the same configuration as the transfer device 30 (image forming device 10) of the present embodiment except for the above points.

  In the case of the second comparative example, the winding length of the pre-nip PN cannot be changed. That is, in the case of the second comparative example, the length of the belt TB wound around the belt CB cannot be changed. Note that, in the present embodiment, the winding length of the pre-nip PN in the second comparative embodiment is equal to the winding length of the pre-nip PN when the moving roll 90 is disposed at the second position.

Here, in the case of the second comparative example, since the pre-nip PN having the same winding length as that in the case where the moving roll 90 is disposed at the second position is formed, the configuration having the above-described second action is provided. Is done. However, in the case of the second comparative example, a halftone having a formation rate of 50% (30% or more and less than 80% of the toner image G in the entire formation area of the toner image G of the medium P) is formed on a medium P having a basis weight of 350 g / m ² . When the toner image G is transferred at a formation rate, a transfer failure due to a shift (microsmear described below) of the toner image G occurs.

  On the other hand, in the transfer device 30 of the present embodiment, when the moving roll 90 is movable to the first position and the second position and does not satisfy a special condition, as shown in FIG. The transfer roller 90 is disposed at the first position, and the toner image G is transferred to the medium P. Then, in the case of the present embodiment, unlike the case of the second comparative embodiment, the winding length of the pre-nip PN is short (1.5 mm in the present embodiment, compared to 2.5 mm in the second comparative embodiment). ).

Further, FIG. 13 shows that the smoothness is less than 9000 seconds and the basis weight is 350 g with the arrangement of the moving roll 90 as a parameter (the winding length of the pre-nip PN is 1.5 mm, 2.0 mm, and 2.5 mm). 5 shows the results of a sensory evaluation of microsmear in a test in which a halftone toner image G having a formation rate of 50% is transferred to a medium P having a specific basis weight of / m ² (an example of a prescribed basis weight). The inventor of the present application has found that the longer the winding length of the belt TB around the belt CB, the more easily micro-smear is generated.

Here, the microsmear means that the toner image G is shifted and transferred from the medium P due to the medium P slipping at the nip N2 due to the speed difference between the medium P being conveyed and the belt TB (the mechanism of microsmear). ) Transfer failure. In particular, microsmear is more likely to occur as the basis weight of the medium P increases. Further, when a halftone toner image G is transferred, the microsmear is conspicuous (it tends to be remarkable). According to FIG. 13, the result of the sensory evaluation is better in the case of the present embodiment than in the second comparative example. Further, from the evaluation results of FIG. 13 and the above mechanism, it is inferred that the more the basis weight of the medium P is larger than 350 g / m ^{2, the} more the result of the sensory evaluation of the winding length of the pre-nip PN and the microsmear becomes remarkable. You.

Therefore, the transfer device 30 according to the present embodiment uses the pre-nip when transferring the toner image G onto the medium P having a smoothness of less than 9000 seconds and a basis weight of 350 g / m ² (an example of a prescribed basis weight). Micro-smear is suppressed as compared with a transfer device in which the wrap length of PN cannot be changed to be shorter than the wrap length of the pre-nip PN when the moving roll 90 is disposed at the second position.

In other words, in the transfer device 30 of the present embodiment, the moving roll 90 can be moved to the first position and the second position, the medium P has a smoothness of less than 9000 seconds, and the medium P has a basis weight of 350 g / m ^2. In the case described above, micro-smear is suppressed as compared with a transfer device that transfers the toner image G to the medium P by disposing the moving roll 90 at the second position.

<Fourth action>
The fourth operation is that the transfer device 30 of the present embodiment includes the rolls 38 arranged at the reference position and the change position. The fourth operation will be described by comparing the present embodiment with a third comparative embodiment assumed below. In the description of the third comparative embodiment, when the same components and the like as those used in the present embodiment are used, the symbols of the components and the like are used as they are even if they are not shown.

  In the transfer device (not shown) of the third comparative example, the roll 38 is always disposed at the reference position. That is, in the transfer device of the third comparative embodiment, the roll 38 cannot move. The transfer device (image forming device (not shown)) of the third comparative embodiment has the same configuration as the transfer device 30 (image forming device 10) of the present embodiment except for the above points.

  In the case of the third comparative example, as described above, the roll 38 cannot move. Therefore, in the case of the third comparative example, a difference occurs in the tension of the belt TB between the case where the moving roll 90 is arranged at the first position and the case where the moving roll 90 is arranged at the second position. Therefore, in the case of the third comparative example, there is a possibility that a transfer failure may occur due to a difference in tension of the belt TB.

  On the other hand, in the case of the present embodiment, the tension of the belt TB is adjusted so that the tension of the belt TB falls within a predetermined range before and after the movement of the moving roll 90 by the roll 38. Specifically, in the case of the present embodiment, the roll 38 moves before and after the movement of the moving roll 90 so that the lengths of the orbits of the belt TB are equal.

  Therefore, in the transfer device 30 of the present embodiment, the difference in the tension of the belt TB before and after the movement of the moving roll 90 is smaller than that in the transfer device that does not adjust the tension of the belt TB before and after the movement of the moving roll 90.

  The above is the description of the operation of the present embodiment.

  As described above, the present invention has been described in detail with respect to the specific embodiments. However, the technical scope of the present invention includes embodiments other than the above-described embodiments. For example, the technical scope of the present invention includes the following embodiments.

  In the present embodiment, the control unit 60 has been described as a component of the image forming apparatus 10 and not a component of the transfer device 30. However, the element related to the control of the transfer operation in the control unit 60 may be made independent, and the element may be used as a component of the transfer device 30.

  In the present embodiment, the moving roll 90 has been described as being arranged at the first position and the second position. Further, it has been described that the moving roll 90 is in contact with the belt TB at any position. However, when the moving roll 90 is arranged at the second position, the moving roll 90 is arranged at the first position if the winding length by the pre-nip PN can be increased as compared with the case where the moving roll 90 is arranged at the first position. The moving roll 90 may be configured to be separated from the belt TB. That is, when the moving roll 90 is disposed at the first position, the state in which the belt TB is wound around the belt CB may be the state in FIG. 4 (the state in which the pre-nip PN is not formed).

  In the present embodiment, the secondary transfer unit 36 has been described as including the belt unit 70 and the opposing roll 80. However, if the nip N2 can be formed in contact with the belt TB, a roll-shaped member may be used instead of the belt unit 70.

  In the present embodiment, it has been described that the control unit 60 selects one of the normal mode and the special mode according to the job data and causes the image forming apparatus 10 other than the control unit 60 to perform the image forming operation. However, the image forming apparatus 10 may be provided with a user interface (an example of a setting apparatus) so that the user selects the normal mode or the special mode, and causes the image forming apparatus 10 to perform the image forming operation. That is, the length of the belt TB wound around the belt CB may be changed based on information set by the user.

  The transfer device 30 of the present embodiment is provided with a so-called active steering roll (not shown) and a detection device (not shown) that can detect registration deviation of the toner image G on the belt TB (deviation between the toner images G of each color). Then, a toner image G of each color may be formed on the belt TB, a registration device may detect a registration deviation of the toner image G of each color, and the skew may be adjusted by an active type steering roll. In this case, the control unit 60 that has received the job data adjusts the registration error after moving the moving roll 90 to the first position or the second position where the moving roll 90 is to be arranged according to the job data. . Here, the combination of the active type steering roll and the detection device is an example of an adjusting unit. According to the above modification, after adjusting the registration error by the adjusting unit, the moving roll 90 is moved to the first position or the second position where the moving roll 90 is to be arranged according to the job data. Thus, registration deviation on the belt TB due to a change in the position of the moving roll 90 is suppressed.

  In the image forming apparatus 10 of the present embodiment, the process speed may be changeable. In this modification, when a toner image G including a thin line pattern having a predetermined interval or less is transferred onto a medium P having a smoothness of 9000 seconds or more, if the process speed is set to be low, the moving roll 90 is disposed at the first position. May be. That is, the length of the belt TB wound around the belt CB may be changed based on the information on the rotation speed of the belt TB. This is based on the fact that scattering of toner particles hardly occurs due to a reduction in process speed.

  In the present embodiment, a mode other than a case where the medium P to which the toner image G is transferred has a smoothness of 9000 seconds or more and the toner image G held by the belt TB includes a thin line pattern having a predetermined interval or less is set as a normal mode. The case where the medium P to which the toner image G is transferred has a smoothness of 9000 seconds or more and the toner image G held by the belt TB includes a thin line pattern of a predetermined interval or less has been described as the special mode. However, when the medium P to which the toner image G is transferred is less than 9000 seconds in smoothness, or when the medium P has a basis weight other than a predetermined basis weight, the normal mode is set, and the medium to which the toner image G is transferred The case where the smoothness is less than 9000 seconds or the medium P has a basis weight equal to or more than a predetermined basis weight may be set as the special mode.

10 Image Forming Apparatus 20 Toner Image Forming Section 30 Transfer Apparatus 38, 39 Mechanism Including Tension Roll and Cam (Example of Adjusting Member)
50 fixing device 70 belt unit (an example of a transfer unit)
80 Counter roll (example of contact part)
90 Moving Roll (Example of Moving Unit)
TB Intermediate transfer belt (example of belt)
P medium G Toner image (example of image)

Claims (5)

An endless belt that rotates while holding the image,
A contact portion that contacts the inner periphery of the belt;
A transfer unit for transferring an image held by the belt to a medium to be conveyed, with the belt sandwiched by the contact unit;
A moving unit that is arranged on the inner peripheral side of the belt, moves, and changes a winding length of the belt around the transfer unit ;
The moving section is movable to a first position where the winding length is 1.5 mm or less, and a second position where the winding length is 2.0 to 2.5 mm.
When the medium to which the image is transferred has a smoothness of 9000 seconds or more and the interval between the images held by the belt includes a fine line pattern of 2.5 mm or less, the moving unit is arranged at the second position and the transfer unit When the medium on which the image is transferred has a smoothness of less than 9000 seconds and the medium has a basis weight or more, the moving unit is disposed at the first position and the image is transferred to the transfer unit. Transfer the image,
Transfer device. An adjusting member that adjusts the tension so that the tension of the belt is within a predetermined range before and after the movement of the moving unit;
The transfer device according to claim 1 , further comprising: A transfer device according to claim 1 or 2 ,
A forming unit that forms an image held by the belt,
A fixing device for fixing the image transferred to the medium by the transfer device to the medium,
An image forming apparatus comprising: A setting device for a user to set a position where the moving unit is arranged,
The moving unit moves according to a setting of the setting device by a user, and changes the winding length.
The image forming apparatus according to claim 3 . The forming unit is capable of forming an image composed of a plurality of colors,
Measuring the shift between each single-color image constituting the image of a plurality of colors held on the belt, comprising an adjusting means for adjusting the skew of the belt to reduce the size of the shift,
After moving the moving unit , the adjusting unit adjusts the skew of the belt,
The image forming apparatus according to claim 3 .