Transfer device and image forming apparatus

Abstract

To reduce transfer failure compared with a case where application of a transfer voltage to a transfer member is started before a transfer barrel rotates and a leading end of an inclined surface of a sheet member moves to a transfer position.SOLUTION: A transfer device 30 comprises: a rotating transfer barrel 36 having a barrel body 252 that is provided on an outer peripheral surface 252A, with a recess 178 accommodating a holding member 76 holding a leading end PA of recording paper P for conveyance, and a jacket member 260 that is wound around the outer peripheral surface 252A, has both ends attached to both sides in a circumferential direction of the recess 78, and has an inclined surface 263A formed at an end on the downstream side of a conveyance direction of the recording paper P; and a secondary transfer roll 34 that is applied with a transfer voltage TV, and transfers toner images to the recording paper P held and conveyed by the holding member 76 at a secondary transfer position NT. The transfer device starts the application of the transfer voltage TV to the secondary transfer roll 34 after an inclined leading end 263C of the inclined surface 263A moves to the secondary transfer position NT.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a transfer device and an image forming apparatus. [Background technology]

[0002] Patent Document 1 discloses a technology related to a transfer device that transfers an image on an image carrier. This prior art includes a transfer material transport means that moves the transfer material endlessly along a circulating path, a gripper piece that is attached to the transport means and supported by a rotating shaft to rotate relative to a base member and grip the leading edge of the transfer material, and a switch member that is attached to the base member. The presence of the transfer material in the gripper is detected by cutting out a part of the gripper piece at the position of the switch member.

[0003] Patent Document 2 discloses a technique relating to a transfer device and an image forming apparatus. In this prior art, the transfer device includes a secondary transfer roll to which a voltage is applied from a power supply device to form a transfer electric field for transferring a developer image to a sheet member, a transfer cylinder having a recess for accommodating a gripping member for gripping the leading end of the sheet member and forming a transfer electric field between the secondary transfer roll and the transfer cylinder at a secondary transfer position, a short circuit for short-circuiting the voltage applied to the secondary transfer roll to a reference potential point, and a grounding unit for activating the short circuit when the recess enters the secondary transfer position due to the rotation of the transfer cylinder and for stopping the operation of the short circuit when the recess leaves the secondary transfer position. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 58-005769 [Patent Document 2] Patent Publication No. 2022-63753 Summary of the Invention [Problem to be solved by the invention]

[0005] A recording medium is conveyed with its leading edge held by a holding member housed in a recess of a transfer cylinder having a sheet member wound around the cylinder body and with an inclined surface formed at its end, and a developer image is transferred onto the recording medium by a transfer member to which a reference voltage is applied as a transfer voltage. At this time, if the recording medium is electrostatically attracted to the inclined surface by the transfer voltage, the rear side of the inclined surface on the recording medium will lift up, and there is a risk of transfer defects such as smears occurring.

[0006] An object of the present invention is to suppress transfer defects compared to a case in which application of transfer voltage to the transfer member is started before the transfer cylinder rotates and the leading edge of the inclined surface of the sheet member moves to the transfer position. [Means for solving the problem]

[0007] A first aspect is a transfer device comprising: a rotating transfer cylinder having a cylinder main body with a recess on its outer peripheral surface in which a holding member that holds and transports a leading end of a recording medium is housed; and a sheet member that is wrapped around the outer peripheral surface, has both ends attached to both circumferential sides of the recess, and has an inclined surface formed at the end downstream in the transport direction of the recording medium; and a transfer member to which a transfer voltage is applied and which transfers a developer image to the recording medium that is held by the holding member at a transfer position and transported, and in which application of the transfer voltage to the transfer member begins after the leading end of the inclined surface moves to the transfer position.

[0008] A second aspect is the transfer device according to the first aspect, wherein the transfer voltage applied to the transfer member reaches a reference voltage after the rear end of the inclined surface moves to the transfer position.

[0009] A third aspect is the transfer device according to the second aspect, wherein the transfer voltage applied to the transfer member reaches a reference voltage when the rear end of the inclined surface moves to the transfer position.

[0010] A fourth aspect is a transfer device according to the first aspect, in which the timing for starting application of the transfer voltage is adjusted in advance so that the transfer voltage applied to the transfer member reaches a reference voltage after the rear end of the inclined surface moves to the transfer position.

[0011] A fifth aspect is a transfer device according to the fourth aspect, in which the timing for starting application of the transfer voltage is adjusted in advance so that the transfer voltage applied to the transfer member reaches a reference voltage when the rear end of the inclined surface moves to the transfer position.

[0012] A sixth aspect is a transfer device as described in the first aspect, in which the timing for starting to apply the transfer voltage to the transfer member is set based on a detection signal detected when a detection mark provided on the transfer cylinder or a member rotating integrally with the transfer cylinder moves to a detection position.

[0013] A seventh aspect is the transfer device described in the first aspect, in which a reverse voltage of opposite polarity to the transfer voltage is applied to the transfer member before the tip of the inclined surface moves to the transfer position, and the transfer voltage is applied from the reverse voltage.

[0014] An eighth aspect is a transfer device described in the seventh aspect, in which the value of the reverse voltage is adjusted in advance so that the transfer voltage applied to the transfer member reaches a reference voltage after the rear end of the inclined surface moves to the transfer position.

[0015] A ninth aspect is a transfer device according to the eighth aspect, in which the value of the reverse voltage is pre-adjusted so that the transfer voltage applied to the transfer member reaches a reference voltage when the rear end of the inclined surface moves to the transfer position.

[0016] A tenth aspect is the transfer device described in the first aspect, in which a standby voltage having an absolute value smaller than a reference voltage of the transfer voltage is applied to the transfer member before the tip of the inclined surface moves to the transfer position, and the transfer voltage is applied from the standby voltage.

[0017] An eleventh aspect is a transfer device described in the tenth aspect, in which the value of the standby voltage is adjusted in advance so that the transfer voltage applied to the transfer member reaches a reference voltage after the rear end of the inclined surface moves to the transfer position.

[0018] A twelfth aspect is a transfer device described in the eleventh aspect, in which the value of the standby voltage is adjusted in advance so that the transfer voltage applied to the transfer member reaches a reference voltage when the rear end of the inclined surface moves to the transfer position.

[0019] A thirteenth aspect is a transfer device comprising: a rotating transfer cylinder having a cylinder main body having a recess on its outer peripheral surface in which a holding member that holds and transports a leading end of a recording medium is housed; and a sheet member that is wrapped around the outer peripheral surface and has both ends attached to both circumferential sides of the recess, with an inclined surface formed at the end upstream in the transport direction of the recording medium; and a transfer member to which a transfer voltage is applied and which transfers a developer image to the recording medium that is held by the holding member at a transfer position and transported, wherein the transfer voltage applied to the transfer member reaches a reference voltage after the leading end of the inclined surface moves to the transfer position.

[0020] A fourteenth aspect is the transfer device according to the thirteenth aspect, wherein the transfer voltage applied to the transfer member reaches a reference voltage after the rear end of the inclined surface moves to the transfer position.

[0021] A fifteenth aspect is the transfer device according to the fourteenth aspect, wherein the transfer voltage applied to the transfer member reaches a reference voltage when a rear end of the inclined surface moves to the transfer position.

[0022] A sixteenth aspect is an image forming apparatus including an image forming unit that forms a developer image, and a transfer device according to any one of the first to fifteenth aspects that transfers the developer image formed by the image forming unit onto a recording medium. Effect of the Invention

[0023] According to the transfer device of the first aspect, transfer defects can be suppressed compared to a case in which application of transfer voltage to the transfer member is started before the transfer cylinder rotates and the leading edge of the inclined surface of the sheet member moves to the transfer position.

[0024] According to the transfer device of the second aspect, transfer failures can be suppressed compared to a case in which the transfer voltage applied to the transfer member reaches the reference voltage before the rear end of the inclined surface of the sheet member moves to the transfer position.

[0025] According to the transfer device of the third aspect, transfer defects can be suppressed compared to a case in which the transfer voltage applied to the transfer member reaches the reference voltage after the rear end of the inclined surface of the sheet member passes the transfer position.

[0026] According to the transfer device of the fourth aspect, control is easier than when the time from the start of application of the transfer voltage until the reference voltage is reached is adjusted in advance.

[0027] According to the transfer device of the fifth aspect, control is easier than when the time from the start of application of the transfer voltage until the reference voltage is reached is adjusted in advance.

[0028] According to the sixth aspect of the transfer device, the accuracy of the timing at which application of the transfer voltage is started is improved compared to when application of the transfer voltage is started based on a detection signal that detects the recording medium being transported upstream of the transfer cylinder in the transport direction.

[0029] According to the transfer device of the seventh aspect, the timing at which the transfer voltage reaches the reference voltage can be delayed, compared to the case where the transfer voltage is applied from 0V.

[0030] According to the transfer device of the eighth aspect, control is easier than when the time from the start of application of the transfer voltage until the reference voltage is reached is adjusted in advance.

[0031] According to the transfer device of the ninth aspect, control is easier than when the time from the start of application of the transfer voltage until the reference voltage is reached is adjusted in advance.

[0032] According to the transfer device of the tenth aspect, the timing at which the transfer voltage reaches the reference voltage can be made earlier, compared to the case where the transfer voltage is applied from 0V.

[0033] According to the transfer device of the eleventh aspect, control is easier than when the time from the start of application of the transfer voltage until the reference voltage is reached is adjusted in advance.

[0034] According to the transfer device of the twelfth aspect, control is easier than when the time from the start of application of the transfer voltage until the reference voltage is reached is adjusted in advance.

[0035] According to the transfer device of the thirteenth aspect, transfer defects can be suppressed compared to a case in which the transfer voltage applied to the transfer member reaches the reference voltage before the leading edge of the inclined surface of the sheet member moves to the transfer position.

[0036] According to the transfer device of the fourteenth aspect, transfer failures can be suppressed compared to a case in which the transfer voltage applied to the transfer member reaches the reference voltage before the rear end of the inclined surface of the sheet member moves to the transfer position.

[0037] According to the transfer device of the fifteenth aspect, transfer defects can be suppressed compared to a case in which the transfer voltage applied to the transfer member reaches the reference voltage after the rear end of the inclined surface of the sheet member passes the transfer position.

[0038] According to the image forming apparatus of the sixteenth aspect, transfer defects can be suppressed compared to a case in which the image forming apparatus is equipped with a transfer device that starts applying transfer voltage to the transfer member before the transfer cylinder rotates and the tip of the inclined surface of the sheet member moves to the transfer position. [Brief description of the drawings]

[0039] [Figure 1] 1 is a schematic diagram showing an overall configuration of an image forming apparatus according to an embodiment of the present invention; [Diagram 2] 2 is a perspective view showing a chain gripper of a transfer device of the image forming apparatus of FIG. 1. [Diagram 3] 2 is a perspective view showing a fixing device of the image forming apparatus in FIG. 1. [Figure 4] A perspective view showing a transfer cylinder, a secondary transfer roll, an opposing roll, and the like provided in the transfer device of the image forming apparatus of FIG. 1. [Diagram 5] 2 is a wiring diagram of an application circuit of a transfer device of the image forming apparatus of FIG. 1. [Figure 6] 13A, 13B, and 13C are operational diagrams showing the conveying operation of a sheet member by a transfer device. [Figure 7] FIG. 2 is an end view of a transfer cylinder of the transfer device as viewed from the axial direction. [Figure 8] FIG. 4 is an explanatory diagram for explaining a secondary transfer position. [Figure 9] FIG. 1A is a schematic diagram showing when a secondary transfer roll enters and exits a recess in a transfer cylinder of a transfer device, and FIG. 1B is an enlarged view of part B in FIG. [Figure 10] FIG. 4 is a timing chart for switching the transfer voltage of the transfer device. [Figure 11] 11 is a table summarizing the results of an experiment conducted on the relationship between timing T2 and timing T3 and transfer defects. [Figure 12] FIG. 11 is an explanatory diagram for explaining the time it takes for the transfer voltage to reach a reference voltage after the application of the transfer voltage is started. [Figure 13] FIG. 11 is a timing chart for switching from the intermediate transfer voltage to the transfer voltage. [Figure 14] 11 is a timing chart for switching the transfer voltage before the leading end of the inclined surface. [Figure 15] FIG. 11 is a timing chart showing switching of transfer voltages in a comparative example. [Figure 16] FIG. 2 is a block diagram of a hardware configuration of a control device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] <Embodiment> An example of a transfer device and an image forming device according to an embodiment of the present invention will be described. Note that, in the drawing, arrow H indicates the up-down direction (vertical direction) of the device, arrow W indicates the width direction (horizontal direction) of the device, and arrow D indicates the depth direction (horizontal direction) of the device.

[0041] In addition, all drawings used in the following description are schematic, and the dimensions and ratios of each element may not necessarily match those of the actual ones. The dimensions and ratios of each element may not necessarily match between multiple drawings. In particular, since FIG. 1 is a schematic configuration diagram showing the overall image forming apparatus, it does not exactly match the details with other drawings that show the details. Substantially identical elements are given the same reference numerals, and their description may be omitted.

[0042] [Image forming equipment] The image forming apparatus 10 according to the present embodiment shown in Fig. 1 is an electrophotographic image forming apparatus that forms a toner image on a sheet-like recording paper P (see Figs. 2 and 3) as a recording medium. The image forming apparatus 10 includes a paper feed mechanism 48, an image forming section 12, a fixing device 100, and a paper discharge mechanism 56. Each mechanism will be described below.

[0043] (Paper feed mechanism) The paper feed mechanism 48 has a function of transporting the recording paper P stored in a storage unit (not shown) to a chain gripper 66 (described later). The paper feed mechanism 48 is composed of a circular conveyor belt 48B wound around a pair of rolls 48A. The conveyor belt 48B transports the recording paper P and passes the recording paper P to a gripping member 76 (see FIG. 2) (described later).

[0044] (Image forming section) The image forming unit 12 has a function of forming an image on recording paper P by an electrophotographic method. The image forming unit 12 includes a toner image forming unit 20 that forms a toner image, and a transfer device 30 that transfers the toner image formed in the toner image forming unit 20 onto the recording paper P. Note that the toner image is an example of a developer image, and the toner image forming unit is an example of a developer image forming unit.

[0045] (Toner image forming unit) A plurality of toner image forming units 20 are provided so as to form a toner image for each color. The image forming unit 12 of this embodiment is provided with toner image forming units 20 for a total of four colors: yellow (Y), magenta (M), cyan (C), and black (K). Note that (Y), (M), (C), and (K) after the reference numerals indicate components corresponding to each color. Also, when yellow (Y), magenta (M), cyan (C), and black (K) are not to be distinguished from each other, the (Y), (M), (C), and (K) after the reference numerals will be omitted in the description.

[0046] The toner image forming units 20Y, 20M, 22C, and 22K of each color are basically configured in the same way except for the toner used. Therefore, the description will be given without distinguishing between the colors. These toner image forming units 20Y, 20M, 20C, and 20K are lined up along the upper horizontal portion of the transfer belt 31 that constitutes the transfer device 30.

[0047] The toner image forming unit 20 includes a photoconductor drum 21 that rotates in the direction of the arrow A01 in the figure, and a charger 22 that charges the photoconductor drum 21. The toner image forming unit 20 further includes an exposure device 23 that exposes the photoconductor drum 21 charged by the charger 22 to form an electrostatic latent image, and a developing device 24 that develops the electrostatic latent image to form a toner image.

[0048] (Transfer device) The transfer device 30 has a function of primarily transferring the toner images on the photoconductor drums 21 of the toner image forming units 20 of each color in a superimposed manner onto an intermediate transfer body, and then secondarily transferring the superimposed toner images onto a recording paper P. The transfer device 30 includes a transfer belt 31 as an example of an intermediate transfer body, a plurality of rolls 32, a primary transfer roll 33, a secondary transfer roll 34, and a transfer cylinder 36. The transfer device 30 further includes an application roll 44 that applies a voltage to the secondary transfer roll 34, and a chain gripper 66 that transports the recording paper P.

[0049] The transfer belt 31 is endless and is wound around a plurality of rolls 32 and a secondary transfer roll 34 so as to assume an inverted triangular posture. The transfer belt 31 rotates in the direction of arrow B when at least one of the plurality of rolls 32 is driven to rotate.

[0050] The primary transfer roll 33 is disposed on the opposite side of the photoconductor drum 21 of each color across the transfer belt 31. The primary transfer roll 33 has a function of transferring the toner image formed on the photoconductor drum 21 to the transfer belt 31 at a primary transfer position T between the photoconductor drum 21 and the primary transfer roll 33.

[0051] The transfer cylinder 36 has a circular cross section and is disposed on the opposite side of the secondary transfer roll 34 across the transfer belt 31. The transfer cylinder 36 has a function of transferring the toner image transferred onto the transfer belt 31 onto the recording paper P at a secondary transfer position NT (see FIG. 8) between the transfer belt 31 and the transfer cylinder 36.

[0052] The chain gripper 66 includes a pair of chains 72, sprockets 71, 73, and 9, and a gripping unit 68 (see FIG. 2) having a gripping member 76 that grips the leading edge of the recording paper P. The gripping member 76 is an example of a holding member.

[0053] As shown in Fig. 2, the pair of chains 72 are disposed at a distance from each other in the device depth direction, and the chains 72 are formed in an endless shape. As shown in Fig. 4, the pair of chains 72 are disposed at one end side and the other end side of the axial direction of the transfer cylinder 36, and are wound around a pair of sprockets 73 whose axial direction is the device depth direction. As shown in Fig. 3, the pair of chains 72 are disposed at one end side and the other end side of the axial direction of the pressure roll 140 described later, and are wound around a pair of sprockets 71 whose axial direction is the device depth direction.

[0054] 1, a chain 72 is wound around sprockets 71 arranged on both ends of the pressure roll 140 and sprockets 73 arranged on both ends of the transfer cylinder 36. When a rotational force is transmitted to one of the sprockets 71, 73, the pair of chains 72 rotates in the direction of arrow C in the figure so as to move from the sprocket 73 side to the sprocket 71 side. In this embodiment, the rotational force is transmitted to the sprocket 73.

[0055] A plurality of gripping units 68 are provided and are arranged at predetermined intervals along the circumferential direction (circumferential direction) of the chain 72. As shown in Fig. 2, the gripping units 68 extend in the device depth direction, and both side portions of the gripping units 68 in the device depth direction are respectively attached to the pair of chains 72. Furthermore, the gripping units 68 include a metallic gripping member 76 that grips the leading edge of the recording paper P.

[0056] The chain gripper 66 transports the recording paper P along the rotational direction of the pair of chains 72. The secondary transfer roll 34, the application roll 44, the chain gripper 66, the transfer cylinder 36, and the like of the transfer device 30 will be described later.

[0057] (Fixing device) The fixing device 100 shown in FIG. 1 has a function of fixing, onto the recording paper P, a toner image transferred onto the recording paper P by the transfer device 30.

[0058] As shown in FIG. 3, the fixing device 100 includes a heating roll 130 that contacts the transported recording paper P and heats the recording paper P, a pressure roll 140 that pressurizes the recording paper P toward the heating roll 130, and a driven roll 150 that rotates following the heating roll 130 and heats the heating roll 130.

[0059] The fixing device 100 also includes a support member 156 that contacts the shaft portion 148 of the pressure roll 140 to support the pressure roll 140, and a biasing member 158 that biases the pressure roll 140 toward the heating roll 130 via the support member 156.

[0060] The driven roll 150 rotates in response to the rotation of the heating roll 130. Furthermore, the heating roll 130 and the pressure roll 140 sandwich and transport the recording paper P onto which the toner image has been transferred, whereby the toner image is heated and fixed onto the recording paper P.

[0061] (Paper ejection mechanism) The paper discharge mechanism 56 shown in Fig. 1 has a function of discharging the recording paper P on which the toner image has been fixed by the fixing device 100 to a discharge section (not shown). The paper discharge mechanism 56 also has a function of receiving the recording paper P that has been released from the gripping member 76 (see Fig. 2) and transporting the recording paper P. The paper discharge mechanism 56 is composed of a circular transport belt 56B wound around a pair of rolls 56A. The transport belt 56B transports the recording paper P and discharges the recording paper P to a discharge section (not shown).

[0062] (Control device) The control device 402 shown in Fig. 5 has a function of controlling the entire image forming apparatus 10 (see Fig. 1). As shown in Fig. 16, an example of a hardware configuration of the control device 402 includes a CPU (Central Processing Unit) 231 that executes various processes, a ROM (Read Only Memory) 232 that stores various programs, a RAM (Random Access Memory) 233 that is used as a temporary work area for the CPU 231, a non-volatile memory 234, and an I / O 235 that is an input / output interface. The CPU 231, the ROM 232, the RAM 233, the non-volatile memory 234, and the I / O 235 are each connected via a bus 236.

[0063] [Image formation operation overview] In the image forming apparatus 10 shown in FIG. 1, a toner image is formed on the recording paper P in the following manner.

[0064] First, the charger 22 for each color uniformly negatively charges the surface of the photoconductor drum 21 for each color to a predetermined potential. Next, based on image data input from the outside, the exposure device 23 irradiates the charged surface of the photoconductor drum 21 for each color with exposure light to form an electrostatic latent image.

[0065] As a result, an electrostatic latent image corresponding to the image data is formed on the surface of each photoconductor drum 21. The developing device 24 for each color develops the electrostatic latent image and visualizes it as a toner image. The primary transfer roll 33 of the transfer device 30 transfers the toner image formed on the surface of the photoconductor drum 21 for each color onto the transfer belt 31 at the primary transfer position T.

[0066] Thus, the recording paper P sent out from a storage unit (not shown) is transported by the paper feed mechanism 48 and handed over to the chain gripper 66, and is transported by the chain gripper 66. The recording paper P transported by the chain gripper 66 is sent out to the secondary transfer position NT (see FIG. 8) where the transfer belt 31 and the transfer cylinder 36 come into contact. At the secondary transfer position NT, the recording paper P is transported while being sandwiched between the transfer belt 31 and the transfer cylinder 36, so that the toner image on the surface of the transfer belt 31 is transferred to the surface of the recording paper P.

[0067] The fixing device 100 fixes the toner image transferred onto the surface of the recording paper P to the recording paper P, and the recording paper P is sent to the paper discharge mechanism 56. The recording paper P sent to the paper discharge mechanism 56 is discharged to the discharge section 52 (not shown).

[0068] [Main components of the transfer device] Next, a description will be given of the main configuration of the transfer device 30. Specifically, the chain gripper 66, the secondary transfer roll 34, the application roll 44, the transfer cylinder 36, the application circuit 400, and the like provided in the transfer device 30 will be described.

[0069] (Chain Gripper) 3 includes, as described above, a pair of chains 72, sprockets 71 and 73, and a gripping unit 68 (see FIG. 2) having a gripping member 76 that grips the leading edge of the recording paper P. The chain gripper 66 is an example of a conveying member.

[0070] 2, the gripping unit 68 includes a plate portion 80 extending in the device depth direction, a pair of support plates 82 supporting the plate portion 80, and shaft members 84 extending in the device depth direction with ends each attached to the chain 72. The gripping unit 68 further includes a gripping member 76 that grips the leading edge of the recording paper P between the plate portion 80 and the shaft members 82.

[0071] 2, the plate portion 80 is made of stainless steel and is disposed between the pair of chains 72. Furthermore, the plate portion 80 is inclined with respect to the sheet conveying direction so that the upstream portion in the sheet conveying direction is closer to the recording paper P than the downstream portion when viewed from the device depth direction.

[0072] The support plates 82 are made of stainless steel, and are arranged at both ends of the plate portion 80 with the plate thickness direction being the device depth direction. The both ends of the plate portion 80 are attached to the pair of support plates 82, respectively, and the pair of support plates 82 support the plate portion 80. The support plates 82 are also formed with a circular through hole 82a.

[0073] The shaft members 84 are made of stainless steel, extend in the device depth direction, and are disposed downstream in the sheet conveying direction with respect to the plate portion 80. Furthermore, the shaft members 84 pass through through holes 82a formed in the support plate 82. Both ends of the shaft members 84 are attached to the pair of chains 72, respectively.

[0074] (Grip member) 2, a plurality of gripping members 76 as an example of a holding member are provided and attached to shaft member 84 at predetermined intervals along the device depth direction. Grip member 76 includes a main body portion 86 having a through hole 86a through which shaft member 84 passes, and a contact portion 88 that contacts recording paper P.

[0075] The main body 86 is made of aluminum, and the downstream portion of the main body 86 in the sheet conveying direction is arc-shaped when viewed from the device depth direction. Furthermore, a protruding portion 86b that protrudes toward the plate portion 80 is formed on the upstream portion of the main body 86 in the sheet conveying direction and on the outer side of the endless chain 72 (= the side opposite to the side surrounded by the endless chain 72 when viewed from the device depth direction). Moreover, the protruding portion 86b is rectangular when viewed from the protruding direction.

[0076] The contact portion 88 is a plate member made of stainless steel, and is attached to the surface of the protruding portion 86b facing outward of the endless chain 72. The contact portion 88 extends from the protruding portion 86b toward the plate portion 80, and is adapted to come into contact with the plate portion 80 from the outside of the endless chain 72.

[0077] The shaft member 84 is rotated by a cam mechanism (not shown), and the contact portion 88 is pressed against the plate portion 80 from the outside of the endless chain 72, contacting the plate portion 80, and then the contact portion 88 moves away from the plate portion 80. In this manner, the leading end of the recording paper P is gripped by the gripping member 76, and then the grip is released.

[0078] (Secondary transfer roll) 4, the secondary transfer roll 34 extends in the device depth direction, and the transfer belt 31 is wound around the secondary transfer roll 34. The secondary transfer roll 34 includes a shaft member 34a and a cylindrical roll portion 34b through which the shaft member 34a passes. The secondary transfer roll 34 is an example of a transfer member. The device depth direction is an example of an axial direction.

[0079] The shaft member 34a is a stainless steel shaft, and both ends of the shaft member 34a are supported by a frame (not shown) via bearings. The roll portion 34b is made of rubber and is attached to the shaft member 34a so as to rotate together with the shaft member 34a. The shaft member 34a may be made of any conductive material, preferably metal, and even more preferably stainless steel. The secondary transfer roll 34 rotates following the rotation of the transfer belt 31.

[0080] (Applying roll) 4, an application roll 44 as an example of an application member has a smaller diameter than the secondary transfer roll 34 and is disposed on the opposite side of the transfer belt 31 with the secondary transfer roll 34 in between. The application roll 44 extends in the device depth direction and is in contact with the outer circumferential surface of the secondary transfer roll 34.

[0081] The application roll 44 rotates in response to the rotation of the secondary transfer roll 34. Furthermore, the application roll 44 applies a voltage to the secondary transfer roll 34 by receiving power from a power supply device 410 (see FIG. 5) to the shaft portion of the application roll 44. As a result, a transfer electric field for transferring the toner image on the transfer belt 31 to the recording paper P is formed at a secondary transfer position NT (see FIG. 8) between the secondary transfer roll 34 and the transfer cylinder 36.

[0082] (Transfer cylinder) 4, the transfer cylinder 36 is disposed on the opposite side of the secondary transfer roll 34 across the transfer belt 31. The transfer cylinder 36 extends in the depth direction of the apparatus.

[0083] The transfer cylinder 36 has a roll portion 174 and a pair of shaft portions 176 that protrude in the apparatus depth direction from both ends of the roll portion 174. The above-mentioned sprockets 73 are attached to the pair of shaft portions 176, respectively.

[0084] 6A, a recess 178 in which the gripping member 76 is disposed is formed in the roll portion 174 of the transfer cylinder 36. This recess 178 extends in the apparatus depth direction from one end to the other end of the roll portion 174.

[0085] As shown in FIG. 6(A), when the gripping member 76 gripping the leading edge of the recording paper P reaches the rotating transfer cylinder 36, it is positioned in a recess 178 of the roll portion 174. Furthermore, as shown in FIG. 6(B), the recording paper P, whose leading edge is gripped by the gripping member 76 and transported, is transported while being wrapped around the rotating transfer cylinder 36, and is sandwiched between the roll portion 174 and the transfer belt 31 at the secondary transfer position NT (see FIG. 8). In this way, the transported recording paper P is transported while being wrapped around the transfer cylinder 36. In other words, the transfer cylinder 36 functions as a support means for supporting the recording paper P.

[0086] Then, the toner image on the transfer belt 31 is transferred to the recording paper P by the transfer electric field at the secondary transfer position NT.

[0087] Furthermore, as shown in FIG. 6C, the gripping member 76 arranged in the recess 178 of the roll portion 174 comes out of the recess 178 of the rotating transfer cylinder 36, and the chain gripper 66 transports the recording paper P downstream in the sheet transport direction.

[0088] 7, the roll portion 174 of the transfer cylinder 36 is configured to include a cylinder main body 252 made of a metal such as aluminum, and a jacket member 260 as an example of a sheet member that is wrapped around an outer circumferential surface 252A of the cylinder main body 252 and configures the outer circumferential portion. The cylinder main body 252 has the aforementioned recess 178 formed along the axial direction on part of the outer circumferential surface 252A.

[0089] The jacket member 260 is made of resin, and has a higher volume resistance than the metal trunk body 252. The jacket member 260 has a base layer 262 that is wrapped around the trunk body 252 without being adhesive, and a surface layer 264 that is wrapped around the outer circumferential surface of the base layer 262 in an adhesive state. Mounting blocks 256, 257 are provided at both circumferential ends within the recess 178. The base layer 262 of the jacket member 260 is detachably attached to the trunk body 252 by having its ends 262A, 262B fastened to the mounting blocks 256, 257 with bolts. In other words, the jacket member 260 is replaceable.

[0090] That is, as shown in Figures 7 and 9(A), one end 261 of jacket member 260 is attached to a mounting block 257 provided on one end side of recess 178, and the other end 263 is attached to a mounting block 256 provided on the other end side of recess 178.

[0091] 9(A) and 9(B), the other end 263 of the jacket member 260 is formed with an inclined surface 263A that becomes thinner toward the tip side. From another perspective, the other end 263 of the jacket member 260 located upstream of the recess 178 in the transport direction of the recording paper P when the jacket member 260 is located at the secondary transfer position NT is formed with an inclined surface 263A whose radial thickness becomes larger toward the upstream side in the transport direction. The rear end of the inclined surface 263A is an inclined rear end portion 263B, and the tip end is an inclined tip portion 263C.

[0092] As shown in Fig. 9(A), the peripheral surface portion of the roll portion 174 of the transfer cylinder 36 other than the recessed portion 178 is defined as a cylinder circumferential portion 179. Also, two secondary transfer rolls 34 are shown in Fig. 9(A), the reason for which will be described later.

[0093] (Applying circuit) 5, the application circuit 400 includes a power supply device 410, the application roll 44, and the secondary transfer roll 34. The application roll 44 has a shaft member 44a and a cylindrical roll portion 44b through which the shaft member 44a passes. As described above, by supplying power from the power supply device 410 to the shaft member 44a of the application roll 44, a voltage is applied to the secondary transfer roll 34, and a transfer electric field is formed at the secondary transfer position NT (see FIG. 7, etc.).

[0094] (Power supply device) 10, the power supply device 410 can switch the voltage applied to the application roll 44 (see FIG. 5, etc.) between a transfer voltage TV and a reverse voltage GV. Note that FIG. 10 is a timing chart showing the voltage switching timing described later.

[0095] The transfer voltage TV is a voltage for forming a transfer electric field at the secondary transfer position NT (see FIG. 1, etc.). The reverse voltage GV is a voltage having a polarity opposite to that of the transfer voltage TV and a smaller absolute value. The transfer voltage TV and the reverse voltage GV of the power supply device 410 are switched by an electrical signal from the control device 402 (see FIG. 5).

[0096] In this embodiment, the transfer voltage TV is switched to the reverse voltage GV based on a reference signal KS used for adjusting various timings throughout the image forming apparatus 10. That is, the voltage is switched after a time set for the reference signal has elapsed.

[0097] In this embodiment, the transfer voltage TV is switched to the reverse voltage GV based on a transfer signal TS, which will be described later. That is, the voltage is switched after a time period set for the transfer signal TS has elapsed.

[0098] (transcription signal) A transfer signal TS, which is an example of a detection signal, is transmitted at a timing T1 when a detection mark provided on the transfer cylinder 36 moves to a preset detection position as the transfer cylinder 36 rotates as shown in Fig. 9(A). Any detection method may be used to detect that the detection mark provided on the transfer cylinder 36 has moved to the detection position.

[0099] For example, when a detection mark such as a resin or metal protrusion provided on an axial end surface near wall surface 178A on one end side of recess 178 in roll portion 174 of transfer cylinder 36 passes a preset detection position, for example, the vicinity of secondary transfer position NT, a photosensor or the like electrically connected to control device 402 (see FIG. 5) detects it and transmits a transfer signal TS. Note that detection mark 269 may be provided on a member that rotates integrally with transfer cylinder 36, for example, shaft portion 176 or sprocket 73 of transfer cylinder 36.

[0100] [Timing for switching the voltage supplied to the application roll] 9(A) shows the secondary transfer rolls 34 on the left and right sides of the figure. The secondary transfer roll 34 on the left side is in a state where it enters the recessed portion 178 as the transfer cylinder 36 rotates, and the secondary transfer roll 34 on the right side is in a state where it leaves the recessed portion 178 as the transfer cylinder 36 rotates. Therefore, in reality, there is only one secondary transfer roll 34.

[0101] 8, when viewed from the depth direction of the device, an intersection point K01 is defined as a line connecting the rotation center of the secondary transfer roll 34 and the rotation center of the transfer cylinder 36 (lines S1, S2, and S3 described below) with the outer circumferential surface of the secondary transfer roll 34. In this embodiment, the line passing through this intersection point K01 is defined as the secondary transfer position NT.

[0102] 8 is the position when the trailing end PB (FIG. 2) of the conveyed recording paper P moves to the secondary transfer position NT. Note that the S1 line is the position before the recess 178 enters the secondary transfer position NT with the rotation of the transfer cylinder 36, and is the portion where the jacket member 60 (see FIG. 9(A), etc.) is provided.

[0103] 9A and 9B is the position where the inclined tip 263C of the inclined surface 263A of the jacket member 260 moves to the secondary transfer position NT as the transfer cylinder 36 rotates.

[0104] 9A and 9B is the position where the inclined rear end 263B of the inclined surface 263A of the jacket member 260 moves to the secondary transfer position NT as the transfer cylinder 36 rotates.

[0105] 10 is a timing chart for explaining the switching timing of the voltage supplied by the power supply device 410 (see FIG. 5). Timing T1 is the timing of switching from the transfer voltage TV to the reverse voltage GV. Timing T2 is the timing of switching from the reverse voltage GV to the transfer voltage TV. Timing T3 is the timing of reaching the transfer pressure TV.

[0106] As described above, the transfer voltage TV and the reverse voltage GV are switched at the timings T1 and T2 by an electric signal from the control device 402 (see FIG. 5). That is, the CPU 231 as an example of a processor of the control device 402 switches the voltage.

[0107] As shown in FIG. 12, even when the power supply device 410 supplies power to the secondary transfer roll 34, it takes a time Δt until the transfer voltage TV applied to the secondary transfer roll 34 is reached. In this embodiment, the rise is considered to be complete when the transfer voltage reaches within ±20% of the transfer voltage TV. In other words, the transfer voltage TV ±20% is the reference voltage. The reference voltage is a voltage necessary for transferring the toner image to the recording paper P. From another perspective, the reference voltage is a voltage at which no transfer defects occur.

[0108] (Timing T1) As shown in FIG. 10, the timing T1 at which the transfer voltage TV is switched to the reverse voltage GV is when the trailing end PB (FIG. 2) of the transported recording paper P moves to the secondary transfer position NT (line S1 in FIG. 9A).

[0109] (Timing T2) As shown in FIG. 10, the timing T2 at which the voltage supplied by the power supply device 410 to the secondary transfer roll 34 is switched from the reverse voltage GV to the transfer voltage TV occurs after the inclined tip 263C of the inclined surface 263A of the jacket member 260 moves to the secondary transfer position NT as the transfer cylinder 36 rotates (line S2 in FIG. 9(A) and FIG. 9(B)).

[0110] (Timing T3) 10 and 12, the timing T3 at which the transfer voltage TV completes rising and reaches the transfer voltage TV is when the inclined rear end 263B of the inclined surface 263A of the jacket member 260 moves to the secondary transfer position NT (line S3 in FIGS. 9A and 9B). As described above, it is sufficient that the reference voltage, that is, the transfer voltage TV±20%, is reached at line S3.

[0111] Any method may be used for pre-adjusting the voltage to reach the transfer voltage TV at the S3 line, but in this embodiment, the voltage is set to reach the transfer voltage TV at the position of the S3 line by pre-adjusting the timing T2. In other words, the time from timing T1 to timing T2 is pre-adjusted to reach the transfer voltage TV at the position of the S3 line.

[0112] [Effect] Next, the operation of this embodiment will be described.

[0113] First, we will explain a comparative example in which the transfer voltage TV is reached as shown in Figure 15 before the S2 line where the inclined tip 263C of the inclined surface 263A of the jacket member 260 moves to the secondary transfer position NT as the transfer cylinder 36 shown in Figures 9(A) and 9(B) rotates.

[0114] In the comparative example, the transfer voltage TV is reached before the line S2, so that the inclined surface 263A is charged as shown in FIG. 15, and as a result, the leading edge PA of the recording paper P is electrostatically attracted to the inclined surface 263A.

[0115] When the leading edge PA of the recording paper P is electrostatically attracted to the inclined surface 263A, the recording paper P may have a so-called stiffness, causing the rear side of the inclined rear end 263B of the inclined surface 263A to rise up from the jacket member 60 and come into contact with the transfer belt 31 upstream in the transport direction from the secondary transfer position NT. Then, a smear in which the developer image is shifted occurs at the contact portion of the recording paper P with the transfer belt 31 upstream in the transport direction from the secondary transfer position NT, i.e., a transfer failure occurs.

[0116] Therefore, in this embodiment, by setting the timing T2 at which the reverse voltage GV is switched to the transfer voltage TV after the inclined leading end 263C of the inclined surface 263A moves to the secondary transfer position NT, the charge amount of the inclined surface 263A is reduced, and the electrostatic adsorption force of the leading end PA of the recording paper P to the inclined surface 263A is reduced. This makes it difficult for the leading end PA of the recording paper P to be electrostatically adsorbed to the inclined surface 263A, and the rear side of the inclined rear end 263B of the inclined surface 263A in the recording paper P is prevented from floating up from the jacket member 60 due to the so-called stiffness of the recording paper P. In other words, contact of the recording paper P with the transfer belt 31 is prevented or suppressed, and smearing, that is, transfer failure, is prevented or suppressed.

[0117] In this way, transfer defects are prevented or suppressed compared to a comparative example in which the timing T2 for switching from the reverse voltage GV to the transfer voltage TV is performed before the inclined tip 263C of the inclined surface 263A moves to the secondary transfer position NT. Explaining from a different perspective, transfer defects are prevented or suppressed compared to a case in which the inclined tip 263C of the inclined surface 263A of the jacket member 260 reaches the transfer voltage TV before the line S2 at which the inclined tip 263C moves to the secondary transfer position NT.

[0118] Here, at the secondary transfer position NT, transfer onto the recording paper P is normally performed after the transfer voltage TV rises to the reference voltage. Therefore, if the timing T2 at which the reverse voltage GV is switched to the transfer voltage TV is set to after the secondary transfer position NT passes the line S3 of the inclined rear end 263B of the inclined surface 263A, transfer defects due to smears can be more reliably prevented or suppressed.

[0119] However, transfer failure occurs because the transfer voltage TV after the inclined rear end 263B does not reach the reference voltage, or the image guarantee range at the leading edge of the recording paper P becomes narrow.

[0120] Even before the transfer voltage TV reaches the reference voltage, the toner image is transferred to the recording paper P, but the density drops. In particular, in the case of a high-density, multi-color toner image, the density drop is more noticeable. Note that a "high-density, multi-color" toner image is one in which the total CIN of two or more colors is 150% or more.

[0121] Therefore, in this embodiment, the timing T2 at which the reverse voltage GV is switched to the transfer voltage TV is set before the secondary transfer position NT passes the line S3 of the inclined trailing edge 263B.

[0122] In this embodiment, the timing T3 at which the transfer voltage TV reaches the reference voltage is set to when the inclined rear end 263B of the inclined surface 263A moves to the secondary transfer position NT. This prevents transfer failures caused by the transfer voltage TV not reaching the reference voltage after the inclined rear end 263B. Alternatively, the image guarantee range of the leading edge of the recording paper P is increased.

[0123] In this embodiment, the timing T2 at which the reverse voltage GV is switched to the transfer voltage TV is adjusted in advance, and the timing T3 at which the transfer voltage TV reaches the reference voltage is set when the secondary transfer position NT moves to the inclined rear end 263B of the inclined surface 263A. Therefore, control is easier than when the time Δt from the timing T2 to the timing T3 is adjusted in advance.

[0124] Furthermore, in this embodiment, timing T2 is set based on a reference signal that is sent at timing T1 when the secondary transfer position NT moves to one end side of the recessed portion 178. In other words, timing T2 is adjusted in advance based on the time from timing T1. Therefore, the accuracy of timing T2 is higher than that of a detection signal that detects recording paper P transported on the upstream side of the transfer cylinder 36 in the transport direction, for example, when detecting the leading edge PA of recording paper P formed by the transport belt 48B.

[0125] In addition, since the reverse voltage GV is raised to the transfer voltage TV, the time Δt is longer than when the transfer voltage TV is raised from 0 V, and the timing T2 at which the transfer voltage TV reaches the reference voltage can be delayed. This prevents the reference voltage from being reached before the inclined rear end 263B of the inclined surface 263A, causing smears.

[0126] [Experimental Results] Next, the results of an experiment conducted on the relationship between timing T2 and timing T3 and transfer failure will be described.

[0127] 11 is a table summarizing the results of experiments on the relationship between timing T2, timing T3, and transfer failure. Note that Experiment 1 is under the conditions of this embodiment, and Experiment 5 is under the conditions of the comparative example of FIG. 15 described above.

[0128] As can be seen from the table in FIG. 11, in experiment 1, neither smear nor density drop occurred. In experiments 2 and 3, no smear occurred, but density drop was observed. In experiment 4, no transfer failure occurred and the effect of suppressing smear was confirmed. In experiment 5, no transfer failure occurred, but smear occurred.

[0129] The conditions of Experiments 2 and 3 can also be adopted if the degree of density reduction is within an acceptable range. Even if the density reduction is not within an acceptable range, it can be adopted by narrowing the image guarantee range at the leading edge of the recording paper P. Moreover, the conditions of Experiment 4 can also be adopted if the degree of smear is within an acceptable range. In other words, the conditions of Experiments 1 to 4 except for Experiment 5 can be adopted.

[0130] <Other> The present invention is not limited to the above embodiment.

[0131] For example, in the above embodiment, the voltage is increased from the reverse voltage GV to the transfer voltage TV, but the present invention is not limited to this.

[0132] 13, the intermediate voltage CV may be applied from the reverse voltage GV, and the transfer voltage TV may be applied from the intermediate voltage CV. The intermediate voltage CV has the same polarity as the transfer voltage TV and is a voltage between the transfer voltage TV and the reverse voltage GV.

[0133] In addition, since the intermediate voltage CV is raised to the transfer voltage TV in this manner, the time Δt (see FIG. 12) is shorter than when the transfer voltage TV is raised from 0V, and the timing T2 at which the transfer voltage TV reaches the reference voltage can be advanced. This prevents the reference voltage from being reached behind the inclined rear end 263B of the inclined surface 263A, causing a transfer failure. In addition, since the time Δt is shorter, the variation in the timing T2 due to the variation in the time Δt is reduced, that is, the accuracy of the timing T2 is improved.

[0134] Also, for example, in the above embodiment, the timing T1 is set by the transfer signal TS, which is a detection signal obtained when a photosensor detects a marker provided on the transfer cylinder 36, but the present invention is not limited to this. For example, the timing T1 may be set based on a reference signal KS used for adjusting various timings of the entire image forming apparatus 10.

[0135] Also, for example, in the above embodiment, the timing T3 is set by adjusting the timing T2 in advance, but this is not limited to this. The timing T3 may be set by adjusting the time Δt (see FIG. 12) in advance. For example, the voltage value of the reverse voltage GV or the intermediate voltage CV may be adjusted in advance to change the time Δt and set the timing T3.

[0136] Also, for example, in the above embodiment, the timing T2 is after the inclined tip portion 263C of the inclined surface 263A of the jacket member 260 moves to the secondary transfer position NT, but this is not limited to this. The timing T2 may be when the inclined tip portion 263C moves to the secondary transfer position NT.

[0137] Furthermore, as shown in FIG. 14, timing T2 may be before the inclined leading end 263C of the inclined surface 263A of the jacket member 260 moves to the secondary transfer position NT, i.e., before S2, while timing T3 may be after the inclined trailing end 263B of the inclined surface 263A moves to the secondary transfer position NT, i.e., after S2.

[0138] Furthermore, the trunk main body 252 may be formed in a substantially columnar shape rather than a substantially cylindrical shape. In short, the trunk main body 252 may have a substantially circular cross section. Note that the term "substantially circular shape" refers to a perfect circle or a circular shape close to a perfect circle. The term "substantially circular shape" also includes a perfect circle. In this embodiment, the shape is a member having a circular cross section in which a recess or the like is formed.

[0139] Also, for example, in the above embodiment, the image forming apparatus is configured so that the toner image on the transfer belt 31 is transferred to the recording paper P, but the present invention is not limited to this. For example, the image forming apparatus may be configured so that the toner image on the transfer roll is transferred to the recording paper P.

[0140] In the above embodiment, the toner image formed by the dry electrophotographic method is used as an example of the developer image, but the developer image is not limited to this. For example, the developer image may be a toner image formed by the wet electrophotographic method.

[0141] Also, for example, it may be a recording medium other than the recording paper P. The recording medium may be a sheet material such as an OHP sheet onto which a developer image such as a toner image can be transferred and fixed.

[0142] The configuration of the image forming apparatus is not limited to that of the above embodiment, and may be variously configured. Furthermore, the present invention may be embodied in various forms without departing from the spirit and scope of the present invention.

[0143] <Additional Notes> (((1))) a rotating transfer cylinder having a cylinder body having a recess on its outer circumferential surface in which a holding member that holds and conveys a recording medium is housed, and a sheet member that is wrapped around the outer circumferential surface and has both ends attached to both sides of the recess in the circumferential direction, and has an inclined surface formed at an end downstream in the conveying direction of the recording medium; a transfer member to which a transfer voltage is applied and which transfers a developer image onto the recording medium which is held by the holding member at a transfer position and conveyed; Equipped with the application of the transfer voltage to the transfer member is started after the tip of the inclined surface moves to the transfer position; Transcription device.

[0144] (((2))) the transfer voltage applied to the transfer member reaches a reference voltage after the rear end of the inclined surface moves to the transfer position; The transfer device according to (((1))).

[0145] (((3))) when the rear end of the inclined surface moves to the transfer position, the transfer voltage applied to the transfer member reaches a reference voltage; The transfer device according to (((2))).

[0146] (((4))) a timing for starting application of the transfer voltage is adjusted in advance so that the transfer voltage applied to the transfer member reaches a reference voltage after the rear end of the inclined surface moves to the transfer position; The transfer device according to any one of ((1))) to (((4))).

[0147] (((5))) a timing for starting application of the transfer voltage is adjusted in advance so that the transfer voltage applied to the transfer member reaches a reference voltage when the rear end of the inclined surface moves to the transfer position; The transfer device according to (((4))).

[0148] (((6))) a timing for starting application of the transfer voltage to the transfer member is set based on a detection signal detected when a detection mark provided on the transfer cylinder or a member rotating integrally with the transfer cylinder moves to a detection position; The transfer device according to any one of (((1))) to (((5))).

[0149] (((7))) Before the tip of the inclined surface moves to the transfer position, a reverse voltage having a polarity opposite to that of the transfer voltage is applied to the transfer member, applying the reverse voltage to the transfer voltage; The transfer device according to any one of (((1))) to (((6))).

[0150] (((8))) a value of the reverse voltage is adjusted in advance so that the transfer voltage applied to the transfer member reaches a reference voltage after the rear end of the inclined surface moves to the transfer position; The transfer device according to (((7))).

[0151] (((9))) a value of the reverse voltage is adjusted in advance so that the transfer voltage applied to the transfer member reaches a reference voltage when the rear end of the inclined surface moves to the transfer position; The transfer device according to (((8))).

[0152] (((10))) before the tip of the inclined surface moves to the transfer position, a standby voltage having an absolute value smaller than the reference voltage of the transfer voltage is applied to the transfer member, applying the standby voltage to the transfer voltage; The transfer device according to any one of (((1))) to (((6))).

[0153] (((11))) a value of the standby voltage is adjusted in advance so that the transfer voltage applied to the transfer member reaches a reference voltage after the rear end of the inclined surface moves to the transfer position; The transfer device according to (((10))).

[0154] (((12))) a value of the standby voltage is adjusted in advance so that the transfer voltage applied to the transfer member reaches a reference voltage when the rear end of the inclined surface moves to the transfer position; The transfer device according to (((11))).

[0155] (((13))) a rotating transfer cylinder having a cylinder body having a recess on its outer circumferential surface in which a holding member that holds and conveys a recording medium is housed, and a sheet member that is wrapped around the outer circumferential surface, both ends of which are attached to both sides of the recess in the circumferential direction, and has an inclined surface formed at an end upstream in the conveying direction of the recording medium; a transfer member to which a transfer voltage is applied and which transfers a developer image onto the recording medium which is held by the holding member at a transfer position and conveyed; Equipped with the transfer voltage applied to the transfer member reaches a reference voltage after the tip of the inclined surface moves to the transfer position; Transcription device.

[0156] (((14))) the transfer voltage applied to the transfer member reaches a reference voltage after the rear end of the inclined surface moves to the transfer position; The transfer device according to (((13))).

[0157] (((15))) when the rear end of the inclined surface moves to the transfer position, the transfer voltage applied to the transfer member reaches a reference voltage; The transfer device according to (((14))).

[0158] (((16))) an image forming unit for forming a developer image; a transfer device according to any one of ((1))) to (((15))) that transfers the developer image formed by the image forming unit onto a recording medium; An image forming apparatus comprising:

[0159] (((1))) This can suppress transfer defects compared to a case in which application of transfer voltage to the transfer member is started before the transfer cylinder rotates and the leading edge of the inclined surface of the sheet member moves to the transfer position.

[0160] (((2))) In comparison with the case where the transfer voltage applied to the transfer member reaches the reference voltage before the trailing edge of the inclined surface of the sheet member moves to the transfer position, transfer defects can be suppressed.

[0161] (((3))) In comparison with the case where the transfer voltage applied to the transfer member reaches the reference voltage after the trailing edge of the inclined surface of the sheet member has passed the transfer position, transfer defects can be suppressed.

[0162] (((4))) This is easier to control than when the time from the start of application of the transfer voltage until the reference voltage is reached is adjusted in advance.

[0163] (((5))) This is easier to control than when the time from the start of application of the transfer voltage until the reference voltage is reached is adjusted in advance.

[0164] (((6))) The accuracy of the timing for starting application of the transfer voltage is improved compared to when application of the transfer voltage is started based on a detection signal that detects the recording medium being transported on the upstream side of the transfer cylinder in the transport direction.

[0165] (((7))) Compared to the case where the transfer voltage is applied from 0 V, the timing at which the transfer voltage reaches the reference voltage can be delayed. (((8))) This is easier to control than when the time from the start of application of the transfer voltage until the reference voltage is reached is adjusted in advance.

[0166] (((9))) This is easier to control than when the time from the start of application of the transfer voltage until the reference voltage is reached is adjusted in advance.

[0167] (((10))) Compared to the case where the transfer voltage is applied from 0 V, the timing at which the transfer voltage reaches the reference voltage can be made earlier.

[0168] (((11))) This is easier to control than when the time from the start of application of the transfer voltage until the reference voltage is reached is adjusted in advance.

[0169] (((12))) This is easier to control than when the time from the start of application of the transfer voltage until the reference voltage is reached is adjusted in advance.

[0170] (((13))) In comparison with the case where the transfer voltage applied to the transfer member reaches the reference voltage before the leading edge of the inclined surface of the sheet member moves to the transfer position, transfer defects can be suppressed.

[0171] (((14))) In comparison with the case where the transfer voltage applied to the transfer member reaches the reference voltage before the trailing edge of the inclined surface of the sheet member moves to the transfer position, transfer defects can be suppressed.

[0172] (((15))) In comparison with the case where the transfer voltage applied to the transfer member reaches the reference voltage after the trailing edge of the inclined surface of the sheet member has passed the transfer position, transfer defects can be suppressed.

[0173] (((16))) This can suppress transfer defects compared to a case where a transfer device is provided that starts applying transfer voltage to the transfer member before the transfer cylinder rotates and the leading edge of the inclined surface of the sheet member moves to the transfer position. [Explanation of symbols]

[0174] 30 Transcription device 34 Secondary transfer roll (an example of a transfer member) 36 Transfer cylinder 76 Gripping member (an example of a holding member) 178 Recess 252A Outer surface 252 Body 260 Jacket member (an example of a sheet member) 263A Slope TV Transfer Voltage NT Secondary transcription position (an example of transcription position) P Recording paper (an example of a recording medium) PA tip

Claims

1. a rotating transfer cylinder having a cylinder body having a recess on its outer circumferential surface in which a holding member that holds and conveys a recording medium is housed, and a sheet member that is wrapped around the outer circumferential surface and has both ends attached to both sides of the recess in the circumferential direction, and has an inclined surface formed at an end downstream in the conveying direction of the recording medium; a transfer member to which a transfer voltage is applied and which transfers a developer image onto the recording medium which is held by the holding member at a transfer position and conveyed; Equipped with the application of the transfer voltage to the transfer member is started after the tip of the inclined surface moves to the transfer position; Transcription device.

2. the transfer voltage applied to the transfer member reaches a reference voltage after the rear end of the inclined surface moves to the transfer position; The transfer device according to claim 1 .

3. when the rear end of the inclined surface moves to the transfer position, the transfer voltage applied to the transfer member reaches a reference voltage; The transfer device according to claim 2 .

4. a timing for starting application of the transfer voltage is adjusted in advance so that the transfer voltage applied to the transfer member reaches a reference voltage after the rear end of the inclined surface moves to the transfer position; The transfer device according to claim 1 .

5. a timing for starting application of the transfer voltage is adjusted in advance so that the transfer voltage applied to the transfer member reaches a reference voltage when the rear end of the inclined surface moves to the transfer position; The transfer device according to claim 4 .

6. a timing for starting application of the transfer voltage to the transfer member is set based on a detection signal detected when a detection mark provided on the transfer cylinder or a member rotating integrally with the transfer cylinder moves to a detection position; The transfer device according to claim 1 .

7. Before the tip of the inclined surface moves to the transfer position, a reverse voltage having a polarity opposite to that of the transfer voltage is applied to the transfer member, applying the reverse voltage to the transfer voltage; The transfer device according to claim 1 .

8. a value of the reverse voltage is adjusted in advance so that the transfer voltage applied to the transfer member reaches a reference voltage after the rear end of the inclined surface moves to the transfer position; The transfer device according to claim 7 .

9. a value of the reverse voltage is adjusted in advance so that the transfer voltage applied to the transfer member reaches a reference voltage when the rear end of the inclined surface moves to the transfer position; The transfer device according to claim 8 .

10. before the tip of the inclined surface moves to the transfer position, a standby voltage having an absolute value smaller than the reference voltage of the transfer voltage is applied to the transfer member; applying the standby voltage to the transfer voltage; The transfer device according to claim 1 .

11. a value of the standby voltage is adjusted in advance so that the transfer voltage applied to the transfer member reaches a reference voltage after the rear end of the inclined surface moves to the transfer position; The transfer device according to claim 10.

12. a value of the standby voltage is adjusted in advance so that the transfer voltage applied to the transfer member reaches a reference voltage when the rear end of the inclined surface moves to the transfer position; The transfer device according to claim 11.

13. a rotating transfer cylinder having a cylinder body having a recess on its outer circumferential surface in which a holding member that holds and conveys a recording medium is housed, and a sheet member that is wrapped around the outer circumferential surface, both ends of which are attached to both sides of the recess in the circumferential direction, and has an inclined surface formed at an end upstream in the conveying direction of the recording medium; a transfer member to which a transfer voltage is applied and which transfers a developer image onto the recording medium which is held by the holding member at a transfer position and transported; Equipped with the transfer voltage applied to the transfer member reaches a reference voltage after the tip of the inclined surface moves to the transfer position; Transcription device.

14. the transfer voltage applied to the transfer member reaches a reference voltage after the rear end of the inclined surface moves to the transfer position; The transfer device according to claim 13.

15. when the rear end of the inclined surface moves to the transfer position, the transfer voltage applied to the transfer member reaches a reference voltage; The transfer device according to claim 14.

16. an image forming unit for forming a developer image; a transfer device according to any one of claims 1 to 15, which transfers the developer image formed by the image forming unit onto a recording medium; An image forming apparatus comprising:

Images