JP2010204225A - Transfer device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer device and an image forming apparatus which conveys paper (transfer sheet) without rotating an unnecessary photoreceptor (image carrier) even in the transfer device which has no conveyer belt (conveying member), and which extends lifetime of the image carrier, suppresses temporal degradation of toner, and reduces transfer (fog) of the toner to a non-printing area of the transfer sheet. <P>SOLUTION: The transfer device is provided with the image carrier (108), a transfer member (101) and the convey member (109). The transfer device has the following two switchable modes: a first mode in which the image carrier abuts on the transfer member and which conveys the transfer sheet by rotationally driving at least one of the image carrier and the transfer member; and a second mode in which the conveying member abuts on the transfer member and which conveys the transfer sheet by rotationally driving at least one of the conveying member and the transfer member without rotationally driving the image carrier. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a transfer device used in an image forming apparatus such as a copying machine, a printer, and a facsimile using an electrophotographic system, and an image forming apparatus including the transfer device.

  Conventionally, in a tandem type color printer, during monochrome printing, the color photoconductor and the photoconductor cleaning member are prevented from being worn out, or the color toner is prevented from being deteriorated with time, and further, the color toner is prevented from being fogged on the paper. For this purpose, a configuration in which the color photoconductor and the conveying belt are separated has been proposed (for example, Patent Document 1 and Patent Document 2). In these, in a tandem type color printer, the conveyor belt is separated from the color image forming photosensitive member during monochrome printing, thereby preventing unnecessary consumption of the photosensitive member. However, the above configuration is based on the premise that there is a conveyance belt. If there is no conveyance belt, there is a problem that the sheet cannot be conveyed when separated during monochrome printing, or the conveyance is not stable.

  Two types of paper transport paths for color printing and paper transport for monochrome printing are available as a configuration that enables paper transport while the color photoconductor is stopped during monochrome printing without using a transport belt. A configuration for switching the paper transport path has also been proposed (for example, Patent Document 3). In this case, two types of paper conveyance paths are created, and the paper conveyance paths are switched between monochrome printing and color printing, so that the paper is conveyed without contacting the color image forming photoreceptor during monochrome printing. In such a configuration, there are always two paper conveyance paths in the printer, and an increase in the size of the apparatus and an increase in the number of parts are inevitable.

  In addition to the above-mentioned patent documents, a conveyor belt is used, and there is a configuration as shown in FIG. In this configuration, 100 is an image forming apparatus main body, 101a to 101d are transfer rollers, 102a to 102d are process cartridges, 103 is an exposure device, 104 is a paper feed tray, 105 is a paper feed roller, 106 is a fixing device, and 107 is a resist. Rollers, 108a to 108d are photosensitive members, 110a to 110d are chargers, and 111a to 111d are developing devices. In this case, the conveyance belt 201 is disposed so as to be sandwiched between the transfer rollers 101a to 101d and the photoconductors 108a to 108d, and the conveyance belt 201 conveys the sheet. However, the conveyance belt 201 is relatively expensive. There is. In addition, it is difficult to regulate the elongation of the conveyor belt 201 and the direction of the roller axis during travel, and a cleaning member for the conveyor belt 201 is necessary. There is also a problem.

  Therefore, in order to achieve cost reduction and downsizing that have been demanded in recent years, without using a conveyor belt, an unnecessary color photoconductor is stably stopped in monochrome printing or two-color printing. For the purpose of carrying, it is also conceivable to simply remove the carrying belt 201 from the above configuration. However, when the conveyor belt 201 is simply removed from the above-described configuration, a photosensitive member (any one or a plurality of the photosensitive members 108a to 108d) that does not need to form a toner image at the time of transfer to a sheet during monochrome printing is also included. The paper cannot be transported unless it is rotated.

  That is, in this case, the photoconductor 108 is driven to rotate regardless of whether or not toner image formation is necessary, so that the life of the photoconductor 108 is lost due to wear (photoconductor film scraping) or the like. Further, when the developing device 111 is driven in conjunction with the rotational driving of the photosensitive member 108, the toner in the developing device 111 is worn out and deteriorated due to idling, so that the quality of the developing device 111 is deteriorated. However, the photosensitive belt (any one or a plurality of 108a to 108d) that does not require the formation of a toner image when transferring to a sheet during single color printing is simply removed from the above configuration. When separating from the transfer roller 101, the conveyance force of the paper (particularly small size paper) is obtained only from the transfer roller 101, and problems such as paper non-feed and skew occur due to insufficient grip force.

  Accordingly, the present invention solves the problems of the conventional apparatus, and even in a transfer apparatus not equipped with a conveyor belt (conveying member), a sheet (transfer material) can be used without rotating an unnecessary photoconductor (image carrier). The present invention provides a transfer device and an image forming apparatus capable of transporting toner, extending the life of an image carrier, suppressing the deterioration of toner over time, and reducing the transfer (fogging) of toner to a non-printing portion of a transfer material. For the purpose.

  In order to solve the above problems, the invention according to claim 1 is an image carrier, a transfer member arranged in the vicinity of the image carrier, and a non-contact arrangement with the image carrier in the vicinity of the image carrier. A transfer device including a transfer member, wherein the image carrier and the transfer member are in contact with each other, and at least one of the image carrier and the transfer member is driven to rotate to transfer the transfer material The transfer member is transported by rotating at least one of the transport member and the transfer member without rotating the image carrier, and the transport member and the transfer member are in contact with each other in the first mode. The second mode is switchable.

  According to a second aspect of the present invention, in the first aspect, the image carrier is in a position spaced apart from the transfer material conveyance path on the side opposite to the transfer member in the second mode. According to a third aspect of the present invention, in the first or second aspect, the first mode and the second mode can be switched by moving the position of the image carrier and the position of the conveying member.

  According to a fourth aspect of the present invention, in the third aspect, the movement of the position of the image carrier and the position of the conveying member is simultaneously performed in conjunction with each other. According to a fifth aspect of the present invention, in the fourth aspect, the interlocking is performed by moving the positions of the image carrier and the transport member by swinging the support member that supports the image carrier and the transport member. And a cam mechanism.

  According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the transfer member has a rotational drive source, and the transport member is driven to rotate by the transfer member in the second mode. To do. According to a seventh aspect of the present invention, in any one of the first to fifth aspects, the rotational driving source of the image carrier in the first mode and the rotational driving source of the conveying member in the second mode are the same. Features.

  According to an eighth aspect of the present invention, there is provided an image forming apparatus comprising the transfer device according to any one of the first to seventh aspects. According to a ninth aspect of the present invention, in the tandem type image forming apparatus in which a plurality of transfer devices are installed in the transfer material conveyance direction, at least one of the plurality of transfer devices other than the transfer device at the most downstream in the transfer material conveyance direction is claimed. Item 8. The transfer device according to any one of Items 1 to 7. According to a tenth aspect of the present invention, in the ninth aspect, the plurality of transfer devices other than the transfer device downstream in the transfer material conveyance direction is a color transfer device, and the transfer device downstream in the transfer material conveyance direction is for monochrome. It is characterized by being a transfer device. According to an eleventh aspect of the present invention, in the ninth or tenth aspect, a transfer material conveyance guide is disposed between the plurality of transfer devices along the transfer material conveyance path. According to a twelfth aspect of the present invention, in the eleventh aspect, the transfer material conveyance guide is formed of a conductive material and is set to a predetermined potential.

  According to the first aspect of the present invention, the image carrier and the transfer member are brought into contact with each other, and at least one of the image carrier and the transfer member is driven to rotate. The first mode for conveying the material, the conveying member and the transfer member abut, the image carrier is not driven to rotate, and the transfer material is conveyed by rotating at least one of the conveying member and the transfer member. Since it can be switched between the two modes, the transfer material is brought into contact only with the image carrier of the necessary color at the time of monochrome printing or any number of color superpositions (two-color printing or three-color printing) By not rotating the other image carrier, it is possible to extend the life of the image carrier, suppress the deterioration of the toner with time, and reduce the transfer (fogging) of the toner to the non-printing portion of the transfer material.

  According to invention of Claim 2, the enlargement of an apparatus can be prevented by minimizing the movement amount of a member. By separating the image carrier that is not driven from the transfer material conveyance path, it is possible to prevent sliding between the image carrier and the transfer material.

  According to the third aspect of the present invention, the transfer material conveyance path in both modes can be made substantially common by fixing the position of the transfer roller substantially in the first and second modes. This eliminates the need to add a transport path switching mechanism and a second transport path, and can prevent the apparatus from becoming large.

  According to the fourth and fifth aspects of the invention, the switching mechanism and the switching control can be simplified by interlocking the position movement.

  According to the sixth and seventh aspects of the present invention, the transfer material can be transported without having the rotational drive source on the transport member, and therefore the size of the apparatus can be prevented from being increased. In the invention according to claim 7, since the rotation driving source of the image carrier, the transfer member, and the conveying member can be only the image carrier, the effect obtained from the invention according to claim 6 is obtained. Is big.

  According to the eighth and ninth aspects of the present invention, it is possible to provide an image forming apparatus including the transfer device as described above. According to the tenth aspect of the present invention, by arranging the monochrome transfer device at the most downstream side, it is possible to form an image without image loss due to passage between the conveying member and the transfer member during monochrome printing.

  According to the eleventh aspect of the present invention, the transfer material transported between the plurality of transfer devices can be smoothly transported by the transport guide. According to the twelfth aspect of the present invention, it is possible to prevent an adverse effect that charges are accumulated in the transfer material conveyance guide.

1 is a schematic front view of an image forming apparatus showing an embodiment of the present invention. 6 is a diagram illustrating switching of the position movement of a photoconductor and a conveyance roller in a first mode and a second mode. 6 is a diagram illustrating switching of the position movement of the photoconductor and the transport roller in the first mode and the second mode, respectively, when the transfer roller moves and when the photoconductor and the transport roller move. It is drawing which shows the position moving mechanism of a conveyance roller. 4 is a drawing showing an interlocking mechanism for position movement of a photoconductor and a conveyance roller. 4 is a diagram for explaining a rotational drive system of a photosensitive member and a conveyance roller in a first mode and a second mode. 6 is a diagram illustrating the positional movement of a photoconductor and a conveyance roller during color image formation and monochrome image formation. 2 is a view showing a conventional image forming apparatus corresponding to FIG.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic sectional view of the image forming apparatus. This image forming apparatus is a general tandem type color image forming apparatus, and its basic configuration has many parts in common with the configuration of the conventional apparatus shown in FIG. That is, the outline of the configuration of the image forming apparatus is as follows. The image forming apparatus main body 100 is provided, and the process cartridges 102a to 102d of three colors (for example, yellow, magenta, cyan) and black are included in the image forming apparatus main body. It is attached detachably. In the image forming apparatus main body 100, an exposure device 103, transfer rollers 101a to 101d (hereinafter, simply referred to as “transfer roller 101” unless otherwise specified), a paper feed tray 104, a fixing device 106, and the like are arranged. It is installed. The transfer roller 101 constitutes a transfer device with the photoconductor 108 and the transport roller 109. In this embodiment, a plurality (four) of transfer devices are arranged.

  The process cartridges 102 a to 102 d are set at predetermined positions on the image forming apparatus main body 100. Reference numerals 108a to 108d denote cylindrical photosensitive drums which are image carriers for carrying toner images (hereinafter, simply referred to as “photoconductor 108” unless otherwise required), and rotate at a linear speed of 50 to 200 mm / s. is doing. A roller-shaped charger 110 serving as charging means is pressed against the surface of the photoconductor 108 and is driven to rotate by the rotation of the photoconductor 1008, and a DC or a bias in which AC is superimposed on DC is applied by a high voltage power source (not shown). As a result, the photoconductor 108 is uniformly charged to a substantially uniform surface potential.

  Following charging, image information is exposed on the surface of the photoconductor 108 by an exposure device 103 which is a latent image forming unit, and an electrostatic latent image is formed. This exposure process is performed by a laser beam scanner or LED using a laser diode. Reference numeral 111 denotes a one-component contact developing device as developing means, which visualizes the electrostatic latent image of the photoreceptor 1008 as a toner image by a predetermined developing bias supplied from a high voltage power source (not shown). The developing device 111 initially stores one-component toner.

  Four process cartridges 102a to 102d are arranged in parallel. When a full-color image is formed, visible images are formed in the order of yellow, magenta, cyan, and black, and the visible images of the respective colors are arranged to face the photoconductor 108. A transfer electric field is formed by applying a predetermined transfer bias supplied from a single high-voltage power source (not shown) to the transfer roller 101 to be transferred, and the toner image on the photoconductor 108 is sequentially transferred to a sheet as a transfer material. Thus, a full color image is formed. Further, the untransferred toner remaining on the photoconductor 108 after the transfer is collected and discarded by a cleaning unit (not shown). In addition, there is a cleaner-less system in which the transfer unit toner is collected by the developing unit without providing the cleaning unit on the photosensitive member 108, and various known cleaning units can be employed.

As the transfer roller 101, a conductive sponge roller or a conductive solid roller can be used. In the case of a conductive sponge roller, a resistance value of 10 ⁻⁴ to 10 ⁻¹³ Ω is formed on a metal core such as SUS by a conductive material. It is comprised by coat | covering the adjusted elastic body. As the material, an ion conductive roller (urethane + carbon dispersion, NBR, hydrin rubber), an electronic conductive type roller (EPDM) or the like is used, and generally has an Asker C hardness of 35 ° to 60 °.

  A sheet as a transfer material is held on the paper feed tray 104 and is conveyed to the registration roller pair 107 by the paper feed roller 105, and is synchronized with the timing at which the front end of the toner image on the photoconductor 108 reaches the transfer portion. Paper is fed and enters the transfer section. The toner image on the paper is transported along the transport guide 130 of the photoreceptor 108 between the transfer devices, and is fixed on the paper by heat and pressure by the fixing device 106 and then discharged. Here, the conveyance guide 130 is formed of a conductive material such as a SUS plate, and is controlled to a predetermined potential such as being grounded via a predetermined electric resistance. This is because charges are prevented from accumulating in the conveyance guide 130 due to friction between the conveyance guide 130 and the paper, or the toner image transferred from the photoconductor 108 is mainly held on the paper by electrostatic force. Further, this is to prevent the electrostatic force from being adversely affected when the sheet on which the toner image is transferred passes over the conveyance guide 130.

  In each transfer device, conveyance rollers 109 a to 109 d (hereinafter, simply referred to as “conveyance roller 109” unless otherwise required) are disposed in the vicinity of the photosensitive member 108 and the transfer roller 101. 108, the first mode in which at least one of the transfer roller 101 and the photosensitive member 108 is rotationally driven, and the transfer roller 101 is in contact with the transport roller 109, and at least one of the transfer roller 101 and the transport roller 109 is It is possible to switch between two modes of the second mode that is rotationally driven. With this mode switching configuration, transfer is performed by the contact nip of the roller pair without rotating a photoreceptor (any one or a plurality of 108a to 108d) that does not need to form a toner image when transferring to a transfer material. The material can be conveyed stably.

  By switching between the first and second modes as described above, the photoconductor 108 and the transport roller 109 are in different positions. That is, as shown in FIG. 2 as an example of the mode switching configuration, in the first mode, the photoconductor 108 and the transfer roller 101 are brought into contact with each other, and the conveyance roller 109 is retracted to a position off the transfer material conveyance path. The In the second mode, the photoconductor 108 'is retracted to a position out of the transfer material conveyance path, and the transfer roller 101 and the conveyance roller 109' are brought into contact with each other. As described above, the first mode is a mode whose main purpose is to convey the transfer material while transferring the toner carried on the photosensitive member 108 to the transfer material, and the second mode is a mode in which the toner is transferred. This mode is mainly intended to convey the transfer material without transferring it to the transfer material.

  In the switching between the first and second modes, the operation of each roller is as follows: the transfer roller 101 shown in FIG. 3A moves, and the photoconductor 108 and the conveyance roller 109 shown in FIG. 3B move. There are two types of cases, but the transfer material conveyance path can be made common in both modes when the photosensitive member 108 and the conveyance roller 109 move compared to when the transfer roller 101 moves. It is more preferable in terms of downsizing the entire apparatus. In the second mode, there is no problem as long as the position of the photoconductor 108 ′ is out of the transfer material conveyance path, but each roller (the photoconductor 108, the transfer roller 101, and the conveyance) is used to reduce the size of the entire apparatus. Since it is preferable that the moving amount of the roller 109) is the minimum, it is preferable that the photosensitive member 108 (108 ′) is positioned on the opposite side of the transfer roller 101 (101 ′) by inserting the transfer material conveyance path in both modes. .

  As a moving mechanism for each roller, for example, a position moving mechanism for the transport roller 109 is shown in FIG. The transport roller 109 is rotatably supported at one end thereof by an arm 152 that is a support member. The arm 152 is supported on the apparatus main body 100 by a shaft 153 and the other end is supported by a rotatable eccentric cam 154 and a pressure spring 155. That is, the arm 152 is configured such that the lower surface of the other end is pressed upward by the pressure spring 155 and the upper surface can be pushed down against the biasing force of the pressure spring 155 by the eccentric cam 154. The position of the arm 152 is restricted. Therefore, when the eccentric cam 154 is rotated in one direction indicated by an arrow in the drawing by a rotation drive source (not shown), the other end of the arm 152 is pushed down against the urging force of the pressure spring 155, thereby Is swung around the shaft 153, and the transport roller 109 moves from the solid line position (first mode) to the dotted line position (second mode) indicated by 109 '. Although not shown, the position moving mechanism of the photoconductor 108 can be the same as the position moving mechanism of the transport roller 109 described above.

  Although FIG. 4 shows a mechanism for moving the transport roller 109 alone, FIG. 5 shows a mechanism for simultaneously moving the photoconductor 108 and the transport roller 109 in conjunction with each other. The transport roller 109 is rotatably supported at one end thereof by a lower arm 162a in the drawing, and the photosensitive member 108 is rotatably supported at one end thereof by an upper arm 162b in the drawing. The lower arm 162 a and the upper arm 162 b are respectively supported by the apparatus main body 100 by shafts 163 a and 163 b, and the other end portions are in contact with the substantially U-shaped member 166. The substantially U-shaped member 166 includes a base portion 167 and two long and short projecting portions 168 and 169 projecting in parallel in the same direction from both ends of the base portion. A rotatable eccentric cam 164 contacts the upper surface of the overhanging portion 168 of the U-shaped member 166 with which the other end of the upper arm 162b contacts, and the other end of the lower arm 162a contacts. A pressure spring 165 is attached to the lower surface of the overhang portion 169 of the U-shaped member 166. That is, the U-shaped member 166 has the lower surface of the overhanging portion 169 with which the other end portion of the lower arm 162a abuts pressed upward by the pressure spring 165, and the other end portion of the upper arm 162b abuts. The upper surface of the overhanging portion 168 can be pushed down against the urging force of the pressure spring 165 by the eccentric cam 164, whereby the positions of the arms 162a and 162b are regulated. Therefore, when the eccentric cam 164 is rotated in one direction indicated by an arrow in the figure, the U-shaped member 166 is pushed down against the urging force of the pressurizing spring 165, whereby each arm 162a, 162b is moved to the shaft 163a and The conveyance roller 109 and the photosensitive member 108 are simultaneously moved in conjunction with the dotted line positions (second mode) indicated by 109 ′ and 108 ′ from the solid line position (first mode). In this way, by using a common moving mechanism for the photoconductor 108 and the transport roller 109, the switching mechanism and switching control for both modes can be simplified, and the entire apparatus can be miniaturized.

  In this embodiment, in the second mode, the conveyance roller 109 is driven and rotated by the transfer roller 101. This will be described. That is, a rotational drive source of the transfer roller 101 that is independent of the rotational drive of the photoconductor 108 is installed. In the first mode, the photoconductor 108 and the transfer roller 101 are independently rotated. As a result, when the toner carried on the photoconductor 108 is transferred to a transfer material, a shearing force is generated in the toner transfer nip due to the difference in linear velocity between the photoconductor 108 and the transfer roller 101. There is an advantage that improvement is expected. In the second mode, the rotation of the photoconductor 108 'is stopped and the transfer roller 101 is driven to rotate. As a result, the transfer roller 109 ′ in the second mode is driven and rotated by the transfer roller 101 to be brought into contact (no rotation drive source dedicated to the transfer roller 109 is provided), so that the transfer material can be stably transferred. As described above, the transferability and transfer material transportability can be ensured only by providing two types of rotation drive sources for the three types of rollers, so that the overall size can be reduced without increasing the number of rotation drive sources. it can.

  In this embodiment, the rotational drive source of the photoconductor 108 in the first mode is the same as the rotational drive source of the transport roller 109 in the second mode. This will be described with reference to FIG. That is, the photosensitive member 108 (108 ') and the transport roller 109 (109') are configured to obtain a rotational driving force from the driving gear 170. In the first mode, a drive gear 171 for rotating the photosensitive member 108 meshes with the drive gear 170. As a result, a driving force from a rotational driving source (not shown) is transmitted to the photoconductor 108. In the second mode, the photoconductor 108 moves to the position of the photoconductor 108 ', and the transport roller 109 moves to the position of the transport roller 109'. At this time, a drive gear 172 for rotating the transport roller 109 ′ meshes with the drive gear 170. As a result, a driving force from a rotation driving source (not shown) is transmitted to the conveying roller 109 '. That is, the photosensitive member 108 can be driven to rotate by the same rotation driving source in the first mode, and the conveyance roller 109 'can be driven in the second mode. The transfer roller 101 and the drive gear 170 are arranged close to each other, but their operations are not linked. The transfer roller 101 is driven by the photosensitive member 108 in the first mode and by the transport roller 109 ′ in the second mode. It is driven and rotated. As described above, transfer can be performed only by providing one system of rotational drive sources for the three types of rollers, and transfer material transportability can be ensured, so that the entire apparatus can be further reduced in size.

  FIG. 7 shows a case where color printing is performed in a tandem type image forming apparatus configured by installing a plurality of transfer devices each including a photoconductor 108, a transfer roller 101, and a transport roller 109 in the transfer material transport direction. And formation of a transfer material conveyance path when performing monochrome printing. Transfer devices for image formation of three colors (cyan, magenta, yellow) from the upstream in the transfer material conveyance direction are arranged, and transfer devices for black image formation are arranged at the most downstream side. As shown in the figure, the three-color transfer device is configured to include the transport roller 109 and the moving mechanism, and the black transfer device is configured not to include the transport roller 109 and the moving mechanism. When a color image is formed, the three-color transfer device is set as the first mode, and when a monochrome image is formed, the three-color transfer device is set as the second mode. As a result, the photosensitive member 108 of the transfer device that does not perform image formation can be selectively rotated and stopped, and the corresponding developing device 111 can also be stopped. Therefore, the photosensitive member 108 and the developing device can be stopped. It is possible to extend the life of the toner 111, to suppress the deterioration of image quality by suppressing the deterioration of the toner over time, and to prevent the toner transfer (fogging) to the non-printing portion of the transfer material. In FIG. 7, all the roller moving mechanisms of the three-color transfer device are shared to reduce the size of the entire device. It is also possible to support color image formation.

  The above-described embodiment is merely a preferred example, and the present invention includes different appropriate embodiments within the scope described in the claims. Further, the members such as the photoconductor 108, the transfer roller 101, and the transport roller 109 described in the embodiment can be replaced with other arbitrary members.

100 Image forming apparatus main body 101a to 101d Transfer roller (transfer member)
102a to 102d Process cartridge 103 Exposure device 104 Paper feed tray 105 Paper feed roller 106 Fixing device 107 Registration rollers 108a to 108d Photosensitive drum (image carrier)
109a to 109d Conveying roller (conveying member)
110 Charging device 111 Developing device 130 Transfer material conveyance guides 152, 162a, 162b Arm (support member)
153, 163a, 163b Shafts 154, 164 Eccentric cams 155, 165 Pressure spring 166 Substantially U-shaped members 170, 171, 172 Drive gear

Japanese Patent Laid-Open No. 11-95619 JP 2001-27852 A JP 2004-70152 A

Claims (12)

A transfer apparatus comprising an image carrier, a transfer member disposed in the vicinity of the image carrier, and a transport member disposed in non-contact with the image carrier in the vicinity of the image carrier,
A first mode in which the image carrier and the transfer member are in contact with each other, and a transfer material is conveyed by rotationally driving at least one of the image carrier and the transfer member;
A second mode in which the transfer member is in contact with the transfer member, the image carrier is not driven to rotate, and at least one of the transfer member and the transfer member is driven to rotate; A transfer device characterized by being switchable.   The transfer apparatus according to claim 1, wherein the image carrier is in a position spaced apart from the transfer material conveyance path on the side opposite to the transfer member in the second mode.   The transfer apparatus according to claim 1, wherein the first mode and the second mode are switched by moving a position of the image carrier and a position of the conveying member.   4. The transfer apparatus according to claim 3, wherein the movement of the position of the image carrier and the position of the conveying member is simultaneously performed in conjunction with each other.   5. The interlocking is performed by a support member that supports the image carrier and the conveyance member, and a cam mechanism that moves the positions of the image carrier and the conveyance member by swinging the support member. The transfer apparatus according to 1.   6. The transfer apparatus according to claim 1, wherein the transfer member has a rotation drive source, and the transport member is driven to rotate by the transfer member in the second mode.   6. The transfer apparatus according to claim 1, wherein the rotation driving source of the image carrier in the first mode and the rotation driving source of the conveying member in the second mode are the same.   An image forming apparatus comprising the transfer device according to claim 1.   The tandem type image forming apparatus in which a plurality of transfer devices are installed in the transfer material conveyance direction, and at least one of the plurality of transfer devices other than the transfer device at the most downstream in the transfer material conveyance direction is defined in any one of claims 1 to 7. An image forming apparatus.   The plurality of transfer devices other than the transfer device at the most downstream side in the transfer material conveyance direction are color transfer devices, and the transfer device at the most downstream side in the transfer material conveyance direction is a monochrome transfer device. The image forming apparatus described.   The image forming apparatus according to claim 9, wherein a transfer material conveyance guide is installed between the plurality of transfer devices along a transfer material conveyance path.   The image forming apparatus according to claim 11, wherein the transfer material conveyance guide is made of a conductive material and has a predetermined potential.