JP5123700B2 - Image forming apparatus and duplex image forming apparatus using the same - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus, and uses an image defect even when a belt or roller-shaped transfer member is used as a transfer unit, particularly when an image is formed on rough paper or paper wrinkled by heat. The present invention relates to an image forming apparatus capable of forming a high-quality image without any defects.

  Conventionally, continuous paper printers were often used for computer output printing on forms, but recently they have been used for high-speed variable information printing, and for multi-purpose printing such as direct mail, invoices, manuals, and books. Has come to be used. Along with the expansion of the applications used, it is necessary to deal with a wide variety of webs (recording media) from thin paper to thick paper and web types from fine paper to rough paper.

  On the other hand, from the viewpoint of resource saving, tandem operation is performed using two continuous paper printers, the first side is printed on the first page, and then the second side is printed on the second side by reversing the web side. As a result, the need for duplex printing is increasing. When dealing with such versatility, the transfer performance of the transfer device is particularly important in order to obtain image quality free from image defects.

  However, in general, in the case of tandem printing, the web is damaged by heat in the first fixing, and unevenness due to heat shrinkage occurs, so in the second transfer portion, the adhesion between the web and the photosensitive drum surface is poor, There is a problem that an image defect is likely to occur due to a transfer defect in the recessed area of the web surface.

  FIG. 9 is a conceptual diagram of a tandem printing method capable of duplex printing on continuous paper. As shown in the figure, the first continuous paper printer P1 that forms an image 70a on the first surface of a continuous long web 7 and the second continuous paper that forms an image 70b on the second surface. The printer P2 is continuously provided.

  The continuous paper printers P1 and P2 perform printing by conveying perforated box paper or perforated roller paper at a high speed (0.5 to 2 m / sec). Unlike the cut sheet, the web 7 as a recording medium is continuous.

  The web 7 is printed with an image 70a by a first printer P1 having an image forming unit such as the developing unit 4a including the photoconductor 1a, and then the web 7 is reversed by the turn bar T, and further developed including the photoconductor 1b. The image 70b is printed on the back surface by a second printer P2 having an image forming unit such as the unit 4b.

  When images are printed on both sides of the web 7 in this way, for example, the second printer P2 prints the image on the back surface of the web portion stopped in the B portion area where the fixing portion for fixing the first image 70a to the web 7 is present. However, there is a problem that the following image defects are generated.

  FIG. 10 is a schematic view showing the web stop state of the fixing unit in which the portion B of FIG. 9 is enlarged. The fixing unit includes a pre-heater 13 that preheats by contacting the web 7 as shown in the figure, a heating roller 14 that includes heaters 14a to 14d, and a backup roller 15 that pressurizes the heating roller 14.

  The fixing unit continues to supply heat to the web 7 during continuous printing, and when printing is stopped, the heaters 14a to 14d are turned off, but due to natural cooling, heating due to residual heat occurs. Therefore, the web 7 on the preheater 13 is thermally contracted in the width direction of the web 7 or the conveying direction thereof, or the web 7 is uneven due to thermal damage. Therefore, when printing is restarted, an image defect is likely to occur when the web portion stopped on the preheater 13 of the first printer P1 passes through the image forming unit of the second printer P2.

  In order to solve such a problem, conventionally, as described in Patent Document 1, a method of providing a transfer assist blade and pressing a web against the surface of a photoreceptor is known. By providing the transfer assist blade, it becomes possible to reduce the unevenness of the web surface and the gap between the photosensitive drums, and good transfer can be obtained. However, in the case of duplex printing, when a toner image is printed on the second surface of the web, since the toner image has already been formed on the first surface, it contacts the transfer assist blade of the web conveyed to the transfer unit housing. The first surface on which the toner image is formed comes to the surface to be processed. For this reason, the surface of the toner image fixed by the transfer assist blade is rubbed, and a part of the toner adheres to the transfer assist blade and becomes dirty, resulting in deterioration of the image formed on the first surface.

  In general, during printing to form an image on the second side of the web, the transfer process is performed in order to improve adhesion because the web is deformed due to the heat history during the fixing process during printing of the first side. It is necessary to increase the pressing pressure of the blade. For this reason, the problem of further promoting blade contamination arises.

  On the other hand, as other transfer means, a transfer roller and a transfer belt system are generally known, and are employed in medium and low speed cut sheet printers. For example, Patent Document 2 describes a configuration in which a driven transfer roller is pressed by a turning lever. Compared with the non-contact corotron transfer system, the transfer roller is brought into contact with an appropriate pressing force, so that the gaps between the web surface unevenness and the photosensitive drum as described above can be reduced. In the transfer roller, an electric charge is supplied to the transfer roller to transfer the toner image developed on the photoreceptor onto the web surface by electrostatic force, and the transfer is performed. As means for supplying electric charge to the transfer roller, there are known a method of applying an electric current to the core metal of the transfer roller and a method of providing a dielectric layer on the surface of the transfer roller and supplying an electric charge necessary for transfer from the surface of the transfer roller. Yes.

  The former method of applying a current to the core of the transfer roller is mainly used in cut paper printers in the middle and low speed range. Since the surface charge required for transfer must be increased as the printing speed increases, it is necessary to increase the nip width (contact area) between the transfer roller and the web. In order to increase the nip width, it is sufficient to increase the roller diameter, increase the thickness of the elastic body, decrease the hardness of the elastic body, etc. This causes the problem of a decrease in roller life due to expansion of roller deformation due to the decrease.

  The latter method of supplying the charge required for transfer from the surface of the transfer roller does not increase the nip width with respect to the printing speed, and the surface dielectric layer also serves as a protective layer, so the transfer roller diameter is increased and the roller life is reduced. Can be prevented. In this method, for example, Patent Document 3 describes that a charge is supplied from the surface to a transfer roller (or transfer belt). However, a charger for supplying electric charges and a static eliminator for removing electric charges on the surface of the transfer roller are required, resulting in an increase in cost.

  In addition, when the transfer roller is applied to a continuous paper printer, the following points need to be considered. In general, the transfer roller is used by being driven by a web. In the case of cut paper, since the web is cut for each sheet, printing is completed until the fixing process, and toner is placed on the web inside the apparatus. Since stopping in an unfixed state is not a normal operation, the transfer roller may be brought into contact with the photosensitive member or the intermediate transfer belt in advance.

  However, in the case of continuous paper, printing may stop in the middle of a job, and an unfixed image exists except for a non-printing area between pages. Usually, in order to ensure the next printing run-up distance, the web performs a web return operation as much as necessary, and at the start-up, the web is started up to a specified speed using the run-up distance. Therefore, in the case of continuous paper, from the point of image deterioration, the transfer roller must be separated from the web when the web is returned and when printing is stopped (including the period from the end of the actual printing process to the complete stop of the transport system, etc.). In other words, a contact / separation operation is required. The contact / separation operation must be performed between the non-printing area at the rear end of the stop portion and the non-printing area at the leading end of the first page.

  At this time, in the case of applying the current to the core of the transfer roller described above, the current flows from the inside at any time. Therefore, even if the rotation speed of the transfer roller itself is delayed with respect to the web conveyance speed, Is not affected. However, in the method of supplying the charge necessary for transfer from the transfer roller surface advantageous for high speed, the transfer roller does not rotate between the charge supply position of the transfer roller and the transfer point at the start of printing. During that time, transcription is not possible. Therefore, when the transfer roller is driven, there is a problem that transfer cannot be performed at the time of startup. Further, there is a problem in the followability of the transfer roller in the high speed region.

As described above, the continuous paper printer is required to support various types of webs in order to cope with various applications, and the width of the web to be used can be properly used depending on the application. For example, when a long photosensitive drum (21 to 22 inches) is used, the width of the web varies widely, such as 12 inches, 16 inches, and 22 inches. Forms are 12 to 16 inches, and manuals, books, etc. are printed with a 17-inch width that can be chamfered in two A4 sizes and a 22-inch 22-inch web that has three B5 sizes. Therefore, when printing a web having a narrow width, the non-sheet passing portion of the photoconductor is in direct contact with the transfer roller. Regarding this point, for example, Patent Document 3 describes that the surface speed of the transfer roller is changed by a switch. When the transfer roller is driven, there is no problem because the speed is the same, but when each is driven, there is a problem that the life of the roller and the photoreceptor is shortened due to mechanical friction of the surface. Further, as described above, in the case of a continuous paper printer, it is necessary to perform the contact / separation operation of the transfer roller in a short time. As the speed increases and the weight increases, the inertia increases, resulting in image quality deterioration such as character blur due to vibration.
JP 2007-47195 A JP-A-48-51640 JP 52-42125 A

  SUMMARY OF THE INVENTION An object of the present invention is to solve such problems of the prior art, and to provide an image forming apparatus capable of forming a high-quality image and a multiple image forming apparatus using the same.

In order to achieve the above object, the first means of the present invention is as follows:
An image carrier for carrying a toner image;
A transfer member for transferring a toner image on the image carrier onto a recording medium;
Conveying means for conveying the recording medium between the image carrier and the transfer member;
In an image forming apparatus comprising: a charger that charges the surface of the transfer member with a polarity opposite to the charge of the toner image;
Rotation driving means for rotating the transfer member in the same direction as the conveyance direction of the recording medium;
Contacting / separating means for bringing the transfer member into contact with the image carrier via the recording medium at the time of printing and separating at times other than printing;
Drive transmission blocking means for transmitting the rotational driving force from the rotational driving means to the transfer member at the time of starting printing, and cutting off the rotational driving force when the rotational speed of the transfer member is stabilized ;
The charger is at a position that does not interfere with the reciprocating movement of the transfer member, and is spaced a predetermined distance from the position of the transfer member when contacting the image carrier via the recording medium. It is characterized by being fixed in position .

The second means of the present invention is:
An image carrier for carrying a toner image;
A transfer member for transferring a toner image on the image carrier onto a recording medium;
Conveying means for conveying the recording medium between the image carrier and the transfer member;
In an image forming apparatus comprising: a charger that charges the surface of the transfer member with a polarity opposite to the charge of the toner image;
Rotation driving means for rotating the transfer member in the same direction as the conveyance direction of the recording medium;
Contacting / separating means for bringing the transfer member into contact with the image carrier via the recording medium at the time of printing and separating at times other than printing;
Drive transmission blocking means for transmitting the rotational driving force from the rotational driving means to the transfer member at the time of starting printing, and cutting off the rotational driving force when the rotational speed of the transfer member is stabilized;
A guide portion that guides the conveyance of the recording medium is provided on the side of the opening facing the image carrier of the transfer device housing that houses the transfer member, and the image of the recording medium guided by the guide portion. The transfer member is disposed in the transfer device housing on the opposite side of the carrier,
When transferring the toner image on the image carrier onto the recording medium, the transfer device housing is moved to the image carrier side together with the transfer member, and the recording medium is moved to the image carrier side by the transfer member. Press to
When the toner image is not transferred onto the recording medium, the transfer housing is moved backward together with the transfer member from the image carrier, and the recording medium is separated from the image carrier.
The charging device is housed in the transfer device housing, and the charging device is in a position where it does not interfere with the reciprocating movement of the transfer member and is in contact with the image carrier via the recording medium. It is fixed at a position spaced apart from the position of the transfer member,
The transfer device housing is provided with a side wall portion through which the charger passes, and the side wall portion is formed with a notch for allowing the transfer device housing to reciprocate. Is.

The third means of the present invention is:
An image carrier for carrying a toner image;
A transfer member for transferring a toner image on the image carrier onto a continuous long recording medium;
Conveying means for conveying the recording medium between the image carrier and the transfer member;
A charger for charging the surface of the transfer member with a polarity opposite to the charge of the toner image;
A fixing unit that heat-fixes the toner image transferred onto the recording medium, and a first image forming apparatus and a second image forming apparatus,
In a multiple image forming apparatus that forms a first image and a second image on one continuous recording medium by the first image forming apparatus and the second image forming apparatus,
At least the second image forming apparatus is the image forming apparatus of the first or second means .

  The present invention has the above-described configuration, and can provide an image forming apparatus capable of forming a high-quality image and a multiple image forming apparatus using the image forming apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 8 is a schematic configuration diagram of the entire image forming apparatus according to the embodiment.

(1) Configuration of Entire Image Forming Apparatus As shown in FIG. 8, a charger 2, an exposure device 3, a developing device 4, a transfer unit 5, a cleaning brush 6, and the like are arranged along the rotation direction of the photoreceptor 1. . After the charger 2 uniformly charges the surface of the photosensitive member 1, the exposure device 3 irradiates the surface of the photosensitive member 1 with laser light according to image data. As a result, an electrostatic latent image is formed on the surface of the photoconductor 1 and developed by the developing device 4, and a toner image is formed on the surface of the photoconductor 1.

  As the photoconductor 1, a positively charged photoconductor such as a selenium photoconductor, an organic photoconductor (OPC), or amorphous silicon (a-Si) was used. The developing method of the photoreceptor 1 is a reversal developing method, and the charging polarity of the toner is a positive polarity.

  The web 7 made of continuous paper is conveyed to the transfer unit 5 by the web conveyance devices 8 to 12, and the toner image is transferred onto the web 7 by the transfer unit 5. The toner image on the web 7 is heated to the vicinity of the transition temperature of the toner resin when passing through the pre-heater 13, and then the toner image is fused and fixed to the web 7 by a fixing device 16 including a heating roller 14 and a backup roller 15 incorporating a heater. Is done. In the case of duplex printing, two image forming apparatuses are used as shown in FIG. The present invention is characterized by the configuration of the transfer unit 5 in the image forming apparatus. Next, the configuration of the transfer unit 5 will be described.

(2) Configuration of Transfer Unit 2 FIG. 1 is a schematic configuration diagram in the vicinity of the transfer unit, and FIG. 2 is a schematic side view of the transfer roller driving unit (viewed from the direction C in FIG. 1).

  As shown in FIG. 1, tractor-type web conveyance devices 11 and 12 are installed on the upstream and downstream sides of the transfer unit 5 in the web conveyance direction, and the web conveyance devices 11 and 12 rotating in the feed holes of the web 7 are installed. The pins are sequentially fitted to convey the web 7 in a predetermined direction.

  The transfer unit 5 is a transfer unit housing 18 provided with a lower guide 17a and an upper guide 17b for guiding the web 7 at the opening end, a transfer roller 19 accommodated therein, and a corona charger for supplying charges to the surface of the transfer roller 19. 20, a static eliminator 21 that neutralizes the surface of the transfer roller 19 after transfer, and a brush-like cleaning member 22 that removes toner, paper dust, and the like attached to the surface of the transfer roller 19.

  As shown in FIG. 1, the web 7 reaches the web conveyance device 12 from the web conveyance device 11 through the lower guide 17a and the upper guide 17b.

  The transfer roller 19 has a surface layer covered with a fluorine-based non-conductive tube, an intermediate layer provided with a conductive elastic layer, and a lower layer provided with a non-conductive elastic layer and a metal core with a metal core. It is manufactured in a three-layer configuration. In this embodiment, the surface layer of the transfer roller 19 is formed using a tube such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and the thickness is about 30 to 100 μm. As another configuration, a two-layer configuration in which the same non-conductive tube is covered on the surface layer and a conductive elastic layer is provided on the inner layer may be used.

  As shown in FIG. 2, the transfer roller shaft 23 protruding from both ends of the transfer roller 19 is rotatably supported by the tip end of the arm 25 via a bearing 24, and the intermediate portion of the arm 25 is armed via a bearing 26. The support shaft 27 is rotatably supported. Accordingly, the transfer roller 19 is supported so as to be swingable about the arm support shaft 27, and the contact / separation operation with the photoreceptor 1 is performed as described later.

  Both end portions of the arm support shaft 27 are rotatably supported by side plates 28 arranged opposite to each other, and the side plate 28 further supports a drive shaft 29 and a tractor shaft 30 that rotatably support the web conveying device 11. Has been.

  A pulley 31 is attached to one end of the drive shaft 29, the pulley 31 is connected to a driving pulley 33 via a timing belt 32, and the driving pulley 33 is connected to an output shaft of the web conveyance motor 34. . An intermediate pulley 35 is attached to the drive shaft 29, and the intermediate pulley 35 is connected to an intermediate pulley 37 fixed to one end of the arm support shaft 27 via a timing belt 36. Further, an intermediate pulley 38 is attached to the arm support shaft 27, and the intermediate pulley 38 is connected to a pulley 40 fixed to one end of the transfer roller shaft 23 via a timing belt 39.

  Accordingly, the rotational driving force of the web conveyance motor 34 is transmitted to the web conveyance device 11 via the driving pulley 33 -the timing belt 32 -the pulley 31 -the drive shaft 29. Further, this rotational driving force is transmitted to the arm support shaft 27 via the drive shaft 29 -intermediate pulley 35 -timing belt 36 -intermediate pulley 37. Furthermore, this rotational driving force is transmitted to the transfer roller 19 via the intermediate pulley 38 -the timing belt 39 -the pulley 40 -the transfer roller shaft 23.

  Accordingly, when the web conveyance motor 34 rotates, the transfer roller 19 rotates in synchronization with the web conveyance device 11. In this embodiment, the web conveyance motor 34 is used to rotate the transfer roller 19, but another drive source may be used.

  As shown in FIG. 1, one end of a spring 41 is connected to the proximal end side of the arm 25, and the other end of the spring 41 is connected to a fixed portion 42. An eccentric cam 43 is attached between the arm support shaft 27 and the spring 41 at a position close to the arm 25, and the eccentric cam 43 is rotated at a predetermined timing by a motor (not shown). The spring 41 is used to give an appropriate pressing force to the transfer roller 19 to obtain a predetermined nip width with the photoreceptor 1. The eccentric cam 43 is used for the contact operation of the transfer roller 19 with respect to the photosensitive member 1 in cooperation with the spring 41. Next, the swing mechanism of the transfer device housing 18 will be described.

(3) Oscillating mechanism of the transfer device housing 18 As shown in FIG. 3, the transfer device housing 18 is supported so as to be able to swing around an axial core portion 44 provided on the upper portion. One end of a link 45 is connected to the rear wall of the transfer unit housing 18 opposite to the photoreceptor 1, and the other end of the link 45 is eccentrically attached to the output shaft of the housing drive motor 46. Accordingly, the transfer device housing 18 can swing around the swing shaft core portion 44 by the rotation of the housing drive motor 46.

  As described above, in the continuous paper printer, the web 7 and the transfer roller 19 need to be brought into and out of contact with the photosensitive member 1 in a short time. The heavier the total weight, the greater the inertia, which causes image quality degradation such as character blur due to vibration.

  In order to solve this problem, in this embodiment, the corona charger 20, the static eliminator 21 and the cleaning member 22 are not brought into contact with or separated from each other, and only the transfer unit housing 18 supporting the web 7 and the transfer roller 19 are brought into contact with or separated from each other. It is configured to let you. As shown in FIG. 1, since the corona charger 20, the static eliminator 21, and the cleaning member 22 are accommodated in the transfer device housing 18, the transfer device housing 18 has a corona charger 20 as shown in FIG. In addition, notch portions or opening-like notch portions 48a and 48b are formed in the portion of the side wall portion 47 facing the static eliminator 21 and the cleaning member 22, respectively, so that the contact / separation operation of the transfer device housing 18 is allowed. Yes.

  Thus, the corona charger 20, the static eliminator 21 and the cleaning member 22 are separated from the transfer device housing 18 and fixed without being moved into and out of the transfer device housing 18, and the cutout portions 48a and 48b are formed in the transfer device housing 18 to reduce the weight. Therefore, the inertia is small, and the web 7 and the transfer roller 19 can be brought into and out of contact with each other at high speed without causing image quality deterioration. 3, the illustration of the transfer roller 19, the corona charger 20, the static eliminator 21, and the cleaning member 22 is omitted. Next, the operation of the transfer unit 5 will be described.

(4) Operation of Transfer Unit 5 FIGS. 3 and 4 are diagrams showing states of the transfer unit 5 when waiting for printing [FIG. (A)] and during printing [FIG. (B)], and FIG. It is a timing chart which shows.

  At the time of printing standby, the housing drive motor 46 rotates and the transfer unit housing 18 stops at the position shown in FIG. 3A, and the transfer unit housing 18 and the web 7 are separated from the photoreceptor 1.

  Further, as shown in FIG. 4A, the eccentric cam 43 rotates and the long diameter portion pushes up the base end side of the arm 25 against the tensile force of the spring 41, whereby the arm 25 is arm-supported. It swings around the shaft 27. Since the transfer roller 19 is attached to the tip of the arm 25, the transfer roller 19 moves in the Ya direction by the swinging of the arm 25, and is in a non-contact state away from the photoreceptor 1. The rotation of the eccentric cam 43 is stopped in this non-contact state, and the print standby state shown in the figure is maintained. The retraction of the transfer unit housing 18 by the housing drive motor 46 and the retraction of the transfer roller 19 by the eccentric cam 43 are performed almost simultaneously.

  The web conveyance motor 34 rotates based on a web conveyance start signal from a control unit (not shown), and the web conveyance device 11 is driven accordingly, and conveyance of the web 7 is started. As shown in FIG. 5, the conveyance speed of the web 7 rises to a predetermined speed before the leading end of the printed page of the web 7 reaches the transfer point, and the preparation for the transfer operation is completed. The transfer roller 19 starts rotating simultaneously with the web conveyance device 11.

As shown in FIG. 5, the corona charger 20 is turned on after a predetermined delay time t ₁ from the start of the conveying operation of the web 7, and then the transfer housing 7 and the transfer roller 9 after a predetermined delay time t _2. Starts swinging motion. That is, as shown in FIG. 3B, the housing drive motor 46 starts to rotate, the rotational driving force is transmitted to the link 45, pushes the transfer device housing 18 toward the photoreceptor 1, and the web 7 is connected to the photoreceptor 1. The rotation of the housing drive motor 46 stops upon contact. The predetermined delay times t ₁ and t ₂ are not necessarily required to be set, but are set in the present invention to simplify the control.

  Specifically, when the diameter of the transfer roller 19 is 40 mm, and the distance between the corona charger 20 and the transfer point is 40 mm, the time when the remaining 85.6 mm does not enter the corona charger 20 and the running distance of the paper From the relationship, when the paper running distance is shorter than 85.6 mm, it is not necessary to provide a delay time, and when it is longer than 85.6 mm, it is necessary to provide a delay time corresponding to the difference.

  At the same time, as shown in FIG. 4B, the eccentric cam 43 starts rotating from the state of FIG. 4A, that is, the arm 25 is in contact with the peripheral surface of the rotating eccentric cam 43. It rotates in the Yb direction around the support shaft 27. Along with this rotation, the transfer roller 19 swings toward the photosensitive member 1, and an appropriate pressing force is applied to the transfer roller 19 by the tensile force X of the spring 41, whereby a predetermined nip is formed between the transfer roller 19 and the photosensitive member 1. The width is secured.

  In this state where the transfer roller 19 is pressed and an appropriate nip width is ensured between the transfer roller 19 and the photosensitive member 1, a short diameter portion (bottom dead center) of the eccentric cam 43 as shown in FIG. Is opposed to the arm 25, but a slight gap (0.3-2 mm) is formed between them, and the eccentric cam 43 is not in contact with the arm 25. That is, the pressing force of the transfer roller 19 against the photosensitive member 1 is appropriately applied only by the spring 41 without being influenced by the eccentric cam 43. In the present invention, this pressing force is 20 to 80N.

  As shown in FIG. 5, the swinging motion of the transfer roller 19 and the transfer device housing 18 is completed before the leading end of the printed page of the web 7 reaches the transfer point. Since the rotation of the transfer roller 19 is started almost simultaneously with the start of conveyance of the web 7, the transfer roller 19 comes into contact with the web 7 while rotating. The on-operation of the corona charger 20 for supplying the charge to the transfer roller 19 is already performed at the timing when the charge is already on the surface of the transfer roller 19 when the transfer is started. It should be noted that when printing is stopped, the procedure is the reverse of the startup operation, and the next printing operation is prepared.

  In FIG. 4, the distances L1 and L2 of the corona charger 20 and the static eliminator 21 in the printed state from the respective transfer rollers 19 are arranged in an optimal positional relationship for transfer performance. In the present invention, L1 = 8 mm and L2 = 10 mm are set through experiments and the like. Since the transfer roller 19 needs to contact and separate the web 7 in a short time, it is necessary to suppress the weight as much as possible. Since the movement of the unit including the corona charger 20 and the static eliminator 21 attached around the transfer roller 19 is heavy, the image quality deteriorates due to the influence of the transfer roller unit vibration at the time of activation.

  Therefore, in the present embodiment, the positions of the corona charger 20, the static eliminator 21 and the cleaning member 22 are arranged so as not to obstruct the reciprocating movement of the transfer roller 19, and the optimum distance L1 (transfer roller 19 and corona charging) in the printing state. Distance L2 (distance between transfer roller 19 and static eliminator 21), and corona charger 20, static eliminator 21 and cleaning member 22 are fixed at the position. As described above, the transfer roller unit 18 is provided with the notches 48a and 48b, and the corona charger 20, the static eliminator 21, and the cleaning member 22 are separated from the transfer device housing 18 and fixed, thereby transferring the transfer roller unit. The weight of can be suppressed as much as possible. For this reason, it is possible to suppress image deterioration at the time of emergency stop or startup. The notch portions 48a and 48b of each of the transfer device housings 18 are cut so that the side wall portion 47 of the transfer device housing 18 does not come into contact with the corona charger 20, the static eliminator 21, and the cleaning member 22 even when the transfer device housing 18 reciprocates. It is missing. In the present invention, the weight of the unit including the corona charger 20 and the static eliminator 21 attached around the transfer roller 19 is about 5.5 kg, and the corona charger 20 and the static eliminator 21 that do not move are included. The weight is about 2.5 kg.

(5) Other Embodiments of Transfer Roller Driving Section FIG. 6 is a schematic side view of a transfer roller driving section according to another embodiment of the present invention. 2 is different from the embodiment shown in FIG. 2 in that a drive shut-off means 49 such as an electromagnetic clutch is interposed in a portion of the transfer roller shaft 23 between the pulley 40 and the transfer roller 19.

  When the speeds of the web 7 and the transfer roller 19 are stabilized from the start of printing, the drive blocking means 49 blocks transmission of the rotational driving force from the pulley 40 (driving force transmission system) to rotate the transfer roller 19. It is the structure which switches from a drive to a driven with respect to the conveyance speed of the web 7. FIG. When printing is stopped, the transfer roller 19 moves backward and the transfer roller 19 continues to rotate with inertial force, but there is no particular problem. Further, the drive shut-off means 49 may be connected and stopped when printing is stopped.

  As described above, when the speeds of the web 7 and the transfer roller 19 are stabilized, the transmission of the rotational driving force from the driving force transmission system is blocked by the drive blocking means 49, and the transfer roller 19 is moved along with the conveyance of the web 7. By following the rotation, the speed difference between the transfer roller 19 and the web 7 can be eliminated, and the life of the transfer roller 19 can be extended.

  In the above-described embodiment, the transfer roller is used as the transfer member. However, the present invention is not limited to this. For example, the present invention can be applied to the case where another transfer member such as a transfer belt is used.

(6) Other Embodiments of Transfer Roller 19 FIG. 7 is a schematic side view showing another embodiment of the transfer roller 19. Although the transfer roller 19 that is normally used is not shown, the transfer roller shaft and the transfer roller body are integrated.

  In this example, on one side of the transfer roller shaft 23, a first friction pulley 62 having an elongated tube body 51 to be fitted and a flange portion 50 integrally provided on the axially outer side of the tube body 51 is a flange portion. The first stopper 52, which is fitted with the inside 50 and fixed to the outside, is prevented from moving outward in the axial direction. From the other side of the transfer roller shaft 23, an elongated tube body 54 having an axial length slightly shorter than the transfer roller main body 53 and fitted to the transfer roller shaft 23, and an axially outer side of the tube body 54 are provided integrally. A second friction pulley 56 having a flange portion 55 is fitted.

  A transfer roller main body 53 is interposed between the outer periphery of the tubular body 54 and between the flange portion 50 and the flange portion 55, and the transfer roller main body 53 is sandwiched between the flange portion 50 and the flange portion 55. The outer surface of the transfer roller body 53 is covered with a dielectric layer 57 such as PFA.

  A second stopper 58 is fixed to the outer side of the transfer roller shaft 23 in the axial direction of the second friction pulley 56, and a coil spring 59 is interposed between the second friction pulley 56 and the second stopper 58.

  Both ends of the transfer roller shaft 25 are supported by bearings 24, a pulley 40 is provided at one end of the transfer roller shaft 25, and the driving force from the drive motor 60 is transferred via the pulley 61 and the timing belt 39 to the transfer roller shaft. 23, the first friction pulley 62, and the second friction pulley 56 are rotated.

  At this time, a load is applied to the first friction pulley 62 and the second friction pulley 56 in the axial direction by the coil spring 59, and when the first friction pulley 62 and the second friction pulley 56 rotate, the transfer roller body 53 is R in the figure. It is rotated by frictional force at the part.

Configuration Here, an elastic force Ps of the coil spring 59, the friction coefficient mu ₁ of the flange portion 50, 55 and between the transfer roller body 53 low, as the friction coefficient mu ₂ between the web 7 and the transfer roller 19 is higher doing. Specifically, Ps = 1 kgf, μ ₁ = 0.22, and μ ₂ = 0.65. The load between the photosensitive member and the transfer roller 19 is set to 3 kgf.

  When the web 7 and the photoreceptor 1 are in contact with the surface of the transfer roller 19 during printing, the surface speed Vr of the transfer roller 19 is set to a load relationship that follows the speed Vp of the web 7 and the photoreceptor 1. By adopting this configuration, the transfer roller 19 can follow the speed of the web 7 and the photosensitive member 1 (Vr = Vp) at the time of printing while having the rotational force of the single transfer roller 19, and the transfer roller 19 and the photosensitive roller 1. The life reduction of the body 1 can be prevented.

  In the above embodiment, the transfer roller swinging operation (reciprocating movement) and the transferer housing swinging operation (reciprocating movement) are performed by different drive systems. It is also possible to perform a swinging operation (reciprocating movement).

  In the embodiment, images are formed on the front and back surfaces of a continuous recording medium using two image forming apparatuses, respectively, but an image is formed on one side of a continuous recording medium using two image forming apparatuses. It is also possible to form.

  According to the said embodiment, there can exist the following effects specifically.

(1) Even when rough paper having large irregularities on the surface is used, good transfer without image defects becomes possible.

(2) When performing double-sided printing with a tandem printing device, even if the web is thermally deformed by the first printer, it is possible to prevent omission of image transfer during transfer by the second printer, Image defects can be reduced.

(3) Since the driving means for rotating the transfer roller is provided, it is possible to ensure transferability at the start of printing in the transfer system that supplies charges necessary for transfer from the surface of the transfer roller. For this reason, it is possible to suppress transfer failure due to deterioration in followability of the transfer roller.

(4) When the printing is started, the driving means for rotating the transfer roller is a driving system interlocked with the web conveying means, so that the difference between the web conveying speed and the transfer roller rotating speed can be suppressed to the minimum source. The life of the photoconductor can be extended.

(5) The transfer roller has a double structure consisting of an outer peripheral roller that follows the web conveyance speed and an inner peripheral roller that transmits the drive for rotating the transfer roller, so the life of the transfer roller and the photoconductor can be extended. It becomes. Further, the replacement unit at the time of the transfer roller life can be only the outer peripheral roller, and the page cost can be reduced.

(6) In the transfer system for supplying the charge necessary for transfer from the transfer roller surface, the transfer roller unit is fixed because the optimum position of the necessary members such as a charger attached around the transfer roller is fixed to the transfer roller position at the time of printing. The weight of the image forming apparatus can be reduced, the vibration of the transfer roller during contact / separation operation can be suppressed, and deterioration in image quality such as character blur at the time of activation can be reduced.

1 is a schematic configuration diagram of a transfer unit of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic side view of the transfer unit in the vicinity of a transfer roller driving unit (viewed from a direction C in FIG. 1). It is a schematic block diagram for demonstrating the rocking | fluctuation mechanism of the transfer device housing in the transfer part. It is a schematic block diagram for demonstrating the rocking | fluctuation mechanism of the transfer roller in the transfer part. It is a timing chart for demonstrating each operation | movement of the transcription | transfer part. It is a schematic side view which shows other embodiment of a transfer part. It is a schematic side view which shows other embodiment of a transfer roller. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. It is explanatory drawing of tandem printing. It is explanatory drawing which shows the state of the web stopped on the fixing device at the time of printing stop (enlarged view of the B section of FIG. 9).

Explanation of symbols

  1: Photoconductor, 2: Charger, 3: Exposure device, 4: Developer, 4a, 4b: Developing unit, 5: Transfer unit, 6: Cleaning brush, 7: Web, 8-12: Web conveying device, 13 : Preheater, 14: Heating roller, 14a to 14d: Heater, 15: Backup roller, 16: Fixing machine, 17: Guide, 18: Transfer device housing, 19: Transfer roller, 20: Corona charger, 21: Charger 22: Cleaning member, 23: Transfer roller shaft, 24: Bearing, 25: Arm, 26: Bearing, 27: Arm support shaft, 28: Side plate, 29: Drive shaft, 30: Tractor shaft, 31: Pulley, 32: Timing Belt: 33: Drive pulley, 34: Web conveying motor, 35: Intermediate pulley, 36: Timing belt, 37: Intermediate pulley, 38: Intermediate pulley 39: Timing belt, 40: Pulley, 41: Spring, 42: Fixed part, 43: Eccentric cam, 44: Shaft part, 45: Link, 46: Housing drive motor, 47: Side wall part, 48a, 48b: Notch Part, 49: drive cutoff means, 50, 55: collar part, 62: first friction pulley, 52: first stopper, 53: transfer roller body, 51, 54: tubular body, 56: second friction pulley, 57: Dielectric layer, 58: second stopper, 59: coil spring, 60: drive motor, 61: pulley, 70a: first image, 70b: second image, P1: first printer, P2: second printer , L1: distance between the transfer roller and the corona charger, L2: distance between the transfer roller and the static eliminator.

Claims (5)

An image carrier for carrying a toner image;
A transfer member for transferring a toner image on the image carrier onto a recording medium;
Conveying means for conveying the recording medium between the image carrier and the transfer member;
In an image forming apparatus comprising: a charger that charges the surface of the transfer member with a polarity opposite to the charge of the toner image;
Rotation driving means for rotating the transfer member in the same direction as the conveyance direction of the recording medium;
Contacting / separating means for bringing the transfer member into contact with the image carrier via the recording medium at the time of printing and separating at times other than printing;
Drive transmission blocking means for transmitting the rotational driving force from the rotational driving means to the transfer member at the time of starting printing, and cutting off the rotational driving force when the rotational speed of the transfer member is stabilized ;
The charger is at a position that does not interfere with the reciprocating movement of the transfer member, and is spaced a predetermined distance from the position of the transfer member when contacting the image carrier via the recording medium. An image forming apparatus having a fixed position . 2. The image forming apparatus according to claim 1 , wherein a static eliminator for performing static elimination after transfer of the transfer member is at a position that does not interfere with reciprocating movement of the transfer member and through the recording medium. An image forming apparatus, wherein the image forming apparatus is fixed to a position at a predetermined interval with respect to a position of the transfer member when abutting on the image forming apparatus. An image carrier for carrying a toner image;
A transfer member for transferring a toner image on the image carrier onto a recording medium;
Conveying means for conveying the recording medium between the image carrier and the transfer member;
In an image forming apparatus comprising: a charger that charges the surface of the transfer member with a polarity opposite to the charge of the toner image;
Rotation driving means for rotating the transfer member in the same direction as the conveyance direction of the recording medium;
Contacting / separating means for bringing the transfer member into contact with the image carrier via the recording medium at the time of printing and separating at times other than printing;
Drive transmission blocking means for transmitting the rotational driving force from the rotational driving means to the transfer member at the time of starting printing, and cutting off the rotational driving force when the rotational speed of the transfer member is stabilized;
A guide portion that guides the conveyance of the recording medium is provided on the side of the opening facing the image carrier of the transfer device housing that houses the transfer member, and the image of the recording medium guided by the guide portion. The transfer member is disposed in the transfer device housing on the opposite side of the carrier,
When transferring the toner image on the image carrier onto the recording medium, the transfer device housing is moved to the image carrier side together with the transfer member, and the recording medium is moved to the image carrier side by the transfer member. Press to
When the toner image is not transferred onto the recording medium, the transfer housing is moved backward together with the transfer member from the image carrier, and the recording medium is separated from the image carrier.
The charging device is housed in the transfer device housing, and the charging device is in a position where it does not interfere with the reciprocating movement of the transfer member and is in contact with the image carrier via the recording medium. It is fixed at a position spaced apart from the position of the transfer member,
The transfer device housing is provided with a side wall portion through which the charger passes, and the side wall portion is formed with a notch for allowing the transfer device housing to reciprocate. Image forming apparatus. 4. The image forming apparatus according to claim 3 , further comprising: a static eliminator that performs static elimination after transfer of the transfer member is housed in the transfer unit housing, and the static eliminator is located at a position that does not interfere with the reciprocating movement of the transfer member. And fixed at a predetermined interval with respect to the position of the transfer member when contacting the image carrier through the recording medium,
The transfer device housing has a side wall portion through which the static eliminator passes, and the side wall portion has a notch for allowing the transfer device housing to reciprocate. Forming equipment. An image carrier for carrying a toner image;
A transfer member for transferring a toner image on the image carrier onto a continuous long recording medium;
Conveying means for conveying the recording medium between the image carrier and the transfer member;
A charger for charging the surface of the transfer member with a polarity opposite to the charge of the toner image;
A fixing unit that heat-fixes the toner image transferred onto the recording medium, and a first image forming apparatus and a second image forming apparatus,
In a multiple image forming apparatus that forms a first image and a second image on one continuous recording medium by the first image forming apparatus and the second image forming apparatus,
5. The multiple image forming apparatus according to claim 1, wherein at least the second image forming apparatus is the image forming apparatus according to claim 1.

Images