JP4416538B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile, or a printer that uses an electrophotographic method or an electrostatic recording method to form an image on a recording material to obtain a hard copy.

  2. Description of the Related Art Conventionally, in an image forming apparatus, particularly a color image forming apparatus that forms a color image with a plurality of color developers, space saving, low cost, image quality, and high speed have been problems.

  In such a color copying machine, for speeding up, the color of the image forming each image forming unit constituted by integrating image forming means such as a photosensitive drum as an image carrier, a developing device, a cleaner, a charger, etc. A high speed is realized by executing a color image forming process called a tandem method in which a plurality of units are mounted for each and arranged in parallel in the transport direction of a transfer medium on which an image is formed.

  Furthermore, in addition to speeding up, the second image carrier as a transfer device as an image forming device rich in media flexibility (supports a wide range of transfer materials such as postcards, cardboard and large size paper). A plurality of toner image forming portions are arranged on an intermediate transfer member as a transfer medium, and the toner images are sequentially transferred to the transfer material from the intermediate transfer member as a transfer medium to a transfer material (secondary transfer). Has been proposed. Further, the intermediate transfer member is applied in the form of a belt because it can save space and can be used in any apparatus.

  The image forming apparatus shown in FIG. 8 will be described as an example of a full-color image forming apparatus employing both the tandem method and the intermediate transfer method.

  In a system employing a tandem method and an intermediate transfer method, each image forming unit has a photosensitive drum, and a color toner image assigned to each image forming unit is formed. The toner images formed in the image forming unit are superimposed to form a color image.

  In the image forming apparatus shown in FIG. 8, first to fourth image forming units (process stations) from upstream to downstream in the moving direction along a belt-like intermediate transfer member (intermediate belt) 50 as a transfer belt. ) Stations 1Bk, 1C, 1M, and 1Y, which are 1, are arranged in order. At each of the stations 1Bk, 1C, 1M, and 1Y, four color toner images of black Bk, cyan C, magenta M, and yellow Y are obtained. It is formed.

Here, the configuration of these stations 1 will be described by taking as an example the black station 1Bk arranged at the most upstream position in the moving direction of the intermediate belt 50. The other stations 1Y, 1M, and 1C have the same configuration except for the color of the developer. Each member, for example, the photosensitive drum 2Bk is the photosensitive drum 2, and the photosensitive stations 2C, 2M, and 2Y of the color stations 1C, 1M, and 1Y, It corresponds to 2Y. Here, each process station 1Bk, 1C, 1M, members are al provided 1Y, for example, when such a photosensitive drum 2, each process station 1Bk, 1C, 1M, photosensitive in 1Y drum 2Bk, 2C, 2M, 2Y It is a general term.

  In the station 1Bk, an organic photoconductor (photosensitive drum) 2Bk having a diameter of 60 mm is disposed in the center as an image carrier. The drum 2Bk is rotated at a speed of 100 mm / s by a motor (not shown). By this rotation, the peripheral surface passes through each image forming means provided in the periphery, and in the process, an image forming process is performed on the surface to form a toner image.

  Here, the photosensitive drum 2 </ b> Bk is a negative charging type OPC drum configured by providing a charge generation layer of 0.1 μm and a charge transport layer of 20 μm on a conductive support (not shown) which is a shaft part thereof. An amorphous silicon drum may be used as the photosensitive drum 2Bk.

  A conventionally known corona discharge type charger 3 is provided around the photosensitive drum 2Bk as a charging unit which is one of the image forming units, and a charging step is performed. In the charger 3, a wire called gold corona wire having a diameter of 60 μm is stretched at the center of a stainless frame. By applying a negative current of about 600 μA to such a wire, a corona is generated, a part of the wire flows in the direction of the drum 2Bk, and the peripheral surface of the drum 2Bk is uniformly charged to about −800 V here.

  Laser light L is irradiated from the laser scanner unit 100Bk to the uniformly charged photosensitive drum 2Bk charging surface (latent image forming step). In the laser scanner unit 100Bk used as an exposure unit which is a latent image forming unit, a conventionally known polygon mirror rotates inside, and a laser L is pulse-driven in accordance with an image signal to emit light and reflected by the polygon mirror. The

  The spot of the laser L is irradiated with a spot diameter of 55 μm in the main scanning direction in the axial direction of the photosensitive drum 2Bk and 55 μm in the sub-scanning direction of the rotation direction of the drum 2Bk. Is formed.

  The surface of the photosensitive drum 2Bk charged to −800 V by the corona charger 3 is irradiated with the laser L based on the image signal, and the surface of the photosensitive drum 2Bk is irradiated with light. A latent image is formed. The intensity of the laser beam L changes depending on the darkness of the image, and the potential corresponding to the so-called white background of the image is −700V. The place corresponding to the dark part is about -200V. The portion corresponding to the halftone of the image is prepared by laser exposure so as to be appropriate in the meantime.

  The electrostatic latent image passes through the developing device 4Bk as developing means by the rotation of the photosensitive drum 2Bk, and in the process, the developing process is performed to become a toner image. The developing device 4Bk includes a sleeve 41, which is a developer carrier, which has a magnet inside and conveys the developer to the electrostatic latent image, and a screw 42 that agitates the developer.

  The developer used here is a two-component developer containing a toner and a carrier.

  The toner is based on a polyester resin, and pigments of each color are also dispersed. Further, in the color image forming apparatus as in this example, the softening point of the toner is set lower than that in the conventional black and white system, and in this example also, a sharp melt low temperature fixing toner is used.

  In addition, the toner used here is a 20% toner having high fluidity, that is, low cohesion. The fluidity of the toner can be measured as the degree of aggregation. It is judged that the greater the value of this degree of aggregation, the lower the fluidity of the sample. As a measuring device, Powder Tech (made by Hosokawa Micron Corporation) was used.

  The cohesion degree is measured by placing 200 mesh, 100 mesh, and 60 mesh sieves on a shaking table in the order of 200 mesh, 100 mesh, and 60 mesh sieves so that the 60 mesh sieve comes to the top. set. 5 g of accurately weighed sample is added to the set 60 mesh sieve so that the input voltage to the shaking table is 21.7 V, and the amplitude of the shaking table at that time is in the range of 60 to 90 μm. Adjust (rheostat memory about 2.5) and apply vibration for about 15 seconds. Thereafter, the weight of the sample remaining on each sieve is measured, and the degree of aggregation is obtained based on the following equation. The sample used was left for about 12 hours in an environment of 23 degrees 60% RH, and the measurement environment is 23 degrees 60% RH.

Aggregation degree (%) = (sample weight on 60 mesh sieve) / 5 g) × 100
+ (Sample weight on 100 mesh sieve) / 5 g) × 100 × (3/5)
+ (Sample weight on 200 mesh sieve) / 5 g) × 100 × (1/5)

  The carrier is obtained by dispersing magnetite in a resin, and the surface is resin-coated in order to impart chargeability.

  The developer containing such toner and carrier is filled in the developing device 4Bk. In the developing device 4Bk, the developer is agitated by the screw 42, and the developer having negatively charged toner is supplied to the surface of the sleeve 41 by the magnetic force of the internal magnet. When the photosensitive drum 2Bk and the developer are rubbed with each other, the photosensitive drum 2Bk is rubbed against the developer.

  An AC component and a DC component are applied to the sleeve 41 of the developing device 4Bk. The direct current component is approximately −550 V, and the alternating current component is applied with a rectangular high frequency of 2 KHz and 2 KVpp. With this developing bias, the toner flies in the direction of the drum 2Bk.

  The high potential portion on the surface of the drum 2Bk corresponds to a white background, and the toner does not fly. When the drum potential is low, the toner flies and the toner gets on the drum 2Bk.

In the development process, the surface of the photosensitive drum 2Bk is set to have about 0.5 mg / cm ² of toner per color with respect to the image signal having the highest density corresponding to the solid image.

  The toner image formed on the photosensitive drum 2Bk in this manner moves to the transfer portion tBk, which is the opposite portion between the intermediate belt 50 and the photosensitive drum 2Bk, and undergoes a primary transfer process, and the toner image is transferred to the intermediate belt 50. Transcribed.

  The developer remaining on the surface of the photosensitive drum 2Bk after the primary transfer is removed by the cleaning unit 6Bk before the surface of the photosensitive drum 2Bk is charged again by the charger 3 to prepare for the next image formation.

  Similarly, the toner images of the respective colors are formed in the other process stations 1 and transferred onto the black toner image in accordance with the movement of the intermediate belt 50.

Here, the intermediate belt 50 of the intermediate transfer member, which is a transfer belt in the intermediate transfer system, will be described. The intermediate belt 50, which is an intermediate transfer body, is formed by seamlessly forming a 100 μm polyimide resin into a cylindrical shape by molding. The surface layer is coated with a fluororesin in order to improve the releasability with the toner. Inside the polyimide resin, 3 to 30 parts of carbon are added, and the resistance is adjusted to 10 ⁹ Ωcm. This is because when the resistance is lowered below 10 ⁹ Ωcm, the charge self-attenuating function works in the circulation operation of the intermediate belt 50, and the static eliminator is unnecessary.

  The intermediate belt 50 is configured by being wound around three rollers: a driving roller 52, an inner secondary transfer roller 81, and a tension roller 51. Here, a portion stretched between the driving roller 52 and the tension roller 51 becomes a transfer plane T, and each process station 1 is arranged, facing the photosensitive drum 2 included therein, and each transfer portion t is arranged. .

The drive roller 52 has a diameter of 30 mm and drives the rotation of the intermediate belt 50. At the primary transfer portions t (tBk, tC, tM, tY) where the toner images formed on the respective color stations 1Bk, 1C, 1M, 1Y by the movement of the intermediate belt 50 are arranged on the respective transfer surfaces T, An image is formed and transferred so as to overlap the intermediate belt 50.

At the primary transfer portion t in each process station 1, a transfer blade 5 (5Bk, 5C, 5M, 5Y), which is a primary transfer member, is installed behind the transfer surface T. The transfer blade 5 is made of hydrin rubber and has a resistance value of 10 ⁷ Ωcm.

  In the primary transfer portion t, the toner images formed in the first to fourth stations 1 are overlapped, and the four color toner images are overlapped on the surface of the intermediate belt 50.

  On the other hand, the recording material P is conveyed from the registration roller 12 toward the secondary transfer portion t2.

  The secondary transfer portion t2 is configured as a facing portion between an inner secondary transfer roller 81 that is also a winding roller of the intermediate belt 50 and an outer secondary transfer roller 82 that sandwiches and faces the intermediate belt 50. .

  A current of 20 μA is applied to the outer secondary transfer roller 82 from a high voltage power supply (not shown). The toner image on the intermediate belt 50 and the recording material P are timed and sent to the secondary transfer portion t2.

  In the secondary transfer process, the toner on the intermediate belt 50 is transferred to the paper by the high pressure of the secondary transfer rollers 81 and 82.

  Then, the recording material P is sent to the fixing device 9 and a fixing process is performed. The fixing device 9 includes a fixing roller 91 and a heating roller 92. The rollers 91 and 92 have a rubber elastic layer and a surface layer coated with a fluororesin as a release layer. It is heated to about 170 ° C. by a halogen heater (not shown) inside. The temperatures of the rollers 91 and 92 are controlled by a control circuit (not shown) so as to be constant by a thermistor (not shown).

  Such a fixing device 9 does not have an active oil application device as in the prior art. This is because the wax is included in the toner, and the wax inside the toner oozes out of the toner due to heating and pressurization, and has a releasability between the roller surface layer and the fluororesin.

  The recording material P thus heat-fixed is discharged out of the apparatus. On the other hand, after the transfer, the photosensitive drum 2 is cleaned and removed of the transfer residual toner by the respective cleaners 6 and is subsequently prepared for the formation of the next latent image.

  Toner and other foreign matters remaining on the transfer belt 50 are removed by a cleaning unit that contacts the surface of the transfer belt 50.

  By the way, in the image forming apparatus having this configuration, the above-described image forming process is performed to form a multicolor image (full color image formation) in which four color toner images are superimposed, and a predetermined color among the four color developers. Here, monochromatic image formation using only one color is performed, and in particular, two types of image formation modes are performed, namely monochrome image formation in which an image is formed only with a black developer. In this case, since the predetermined color is only Bk, it is monochromatic image formation. However, as in Example 3 described later, there are cases where a predetermined plurality of colors are used without using all the colors. When only a predetermined color is used, a low-color image is formed.

  In the past, so-called copying, which was a copying machine with only black and white, is becoming popular. In the popularization process of such color copiers, both black and white copiers that make black and white copies and color copiers that make color copies are owned and used as appropriate. However, with the spread of technology in recent years, it has become possible to use monochrome copying, which is a monochromatic image formation, with a color copying machine without a sense of incongruity, and the formation of monochrome images with a color copying machine has become important.

  In the black and white image formation, the black process station 1Bk is operated, and the other process stations 1C, 1M, and 1Y are stopped. In this stop operation state, the photosensitive drums 2M, 2C, and 2Y are rotated to perform the charging process and the developing process, but the so-called white development is performed and a bias is applied to the developing sleeve 41. The color toners stored in the devices 4C, 4M, and 4Y hardly adhere to the photosensitive drum 1 and are not transferred to the intermediate belt 50. Such a stop operation state is performed in a state where the intermediate belt 50 is in contact with the photosensitive drums 2C, 2M, and 2Y. The reason why such a stop operation is performed is that even in the black and white image formation, the intermediate belt 50 charged to the positive side at the black station 1Bk in this example unless the respective charging and developing operations are performed in the color process stations 1C, 1M, and 1Y. This adversely affects the downstream photosensitive drums 2C, 2M, and 2Y.

  That is, due to the positively charged charge of the belt 50, if the downstream photosensitive drums 2C, 2M, and 2Y are not normally charged negatively, they are reversely charged to the positive side. The photosensitive drum 2 is very vulnerable to this reverse charging, and this becomes a memory. Further, when the developing device 4 is operated, usually, a small amount of toner and an external additive of the toner are caused to flow on the photosensitive drum 2 and reach the cleaner 6. Then, the cleaning means provided in the cleaner 6 acts as a lubricant between a cleaner blade (not shown) that scrapes off the toner on the photosensitive drum 2 and the photosensitive drum 2.

  As a result, the friction between the cleaner blade and the photosensitive drum 2 is prevented from increasing, and the blade is turned up and the life of the photosensitive drum 2 is reduced. The drum 2 has a short life. In addition, the frictional force between the intermediate transfer belt 50 and the photosensitive drum 2 is reduced by the toner and the external additive, so that the life of the photosensitive drum 2 can be extended.

  However, in this method, all the parts in the color station operate in spite of the black-and-white image formation, and a small amount of developer capable of lubricating the cleaning blade is also included in the photosensitive drum 1 and the intermediate belt 50. However, there is a disadvantage that the color image forming means is consumed and the durable life is shortened despite the formation of an image that is not output.

  As a solution to this problem, the driving roller 52 supporting the belt 50 on the transfer surface T of the intermediate belt 50 on the downstream side in the moving direction of the intermediate belt 50 is separated from the position of the transfer surface T, , The intermediate belt 50 is separated from the photosensitive drum 2 except for the black station 1Bk arranged in the upstream of the intermediate belt 50 moving direction provided on the side opposite to the driving roller 52. In this state, a method for physically preventing the color toner from adhering to the intermediate belt 50 has been performed. That is, the primary transfer blade 5 and the intermediate belt 50 have been detached from the primary transfer portion t.

  A configuration in which three color stations other than the black station are separated from the intermediate transfer belt is described in Patent Document 1, for example.

  In the present specification, the transfer member such as the primary transfer blade 5 and the transfer belt such as the intermediate belt 50 are separated from the transfer portion that is the primary transfer portion t, and the return operation is reversed. The operation is referred to as a landing operation.

  Here, in the image forming apparatus of FIG. 8, since the first to fourth process stations 1 are arranged in the horizontal direction, the transfer surface T of the intermediate belt 50 is a horizontal plane. The state is lowered to the state 52a, and the intermediate belt 50 is separated from the photosensitive drum 2 except for the black station 1Bk.

  In this case, the primary transfer blades 5C, 5M, and 5Y provided on the lower surface of the transfer surface T are also detached from the lower surface simultaneously with the operation of lowering the downstream side of the transfer surface T in the belt movement direction. In FIG. 8, the state becomes 5Ca, 5Ma, 5Ya.

  However, if the removal operation for removing the intermediate belt 50 together with the drive roller 52 is frequently performed in this way, a physical change of the belt 50 and a displacement of the winding rollers 51 and 52 occur, and the color shift is caused. Control becomes difficult.

  However, as an absolute condition, the intermediate belt 50 needs to run with high accuracy so that the four color toner images are superimposed on the same position on the belt surface. That is, for example, by superimposing two color toners such as red letters and blue letters on the belt 50 with high accuracy, a pure secondary color without color misregistration is formed. For this purpose, the intermediate belt 50 must run accurately without meandering.

  Even if the roller used as the drive roller is not the position shown in FIG. 8 but the roller 51 arranged on the transfer surface T in the most upstream direction in the belt 50 movement direction, one roller in the drive system of the intermediate belt 50 is frequently used. If the attachment / detachment operation is performed, the running stability of the intermediate belt 50 is hindered.

  As another method, the intermediate belt 50 is not removed, and only the primary transfer blades 5C, 5M, and 5Y are removed so that the life of the members related to image formation relating to colors that are not used in monochrome image formation is not worn. Thus, there is a method in which the rotation of the photosensitive drum 2 is stopped by keeping the intermediate belt 50 from contacting the photosensitive drum 2 as much as possible without removing the intermediate belt 50.

  However, this method does not guarantee that the intermediate belt 50 is completely removed from the photosensitive drum 2, and sometimes the intermediate belt 50 is used even though the photosensitive drums 2 </ b> C, 2 </ b> M, and 2 </ b> Y have stopped rotating. However, at the positions of the primary transfer blades 5C, 5M, and 5Y for the respective colors, the photosensitive drum 2 that has stopped is brought into contact with the primary drum and the photosensitive drum 2 is slightly damaged.

In any of the above-described methods, that is, in the method of removing the intermediate belt 50 from the photosensitive drums of unused colors, the problem of color misregistration occurs, and even in the method of removing the transfer blade 5, the intermediate belt. Since there is no guarantee that 50 is separated from the photosensitive drum 2, there arises a problem that some damage occurs on the photosensitive drum 2.
JP 2001-249519 A

  An object of the present invention is to provide a full-color image formation in which a plurality of image forming portions provided for each color are provided along a transfer belt, and a toner image formed in each image forming portion is superimposed to form an image. An image of a color that is not used when forming a low-color image in an image forming apparatus capable of performing both image formation and low-color image formation in which only a toner image formed by a predetermined image forming unit is formed. In the image carrier provided in the forming unit, an image forming apparatus that realizes a long life by reducing damage caused by abrasion with the transfer belt, and does not cause color misregistration due to misalignment or deformation of members. Is to provide.

The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention provides a toner image of different colors comprising a movable transfer belt, an image carrier and a transfer blade for transferring a toner image on the image carrier toward the transfer belt. A plurality of image forming units that can be formed, the transfer belt abuts against an image carrier used for image formation, and the transfer blade and the image carrier that is not used for image formation In the image forming apparatus in which the transfer belt can be separated in a state where the transfer belt is in contact with the transfer belt,
In the moving direction of the transfer belt, a plurality of upstream and downstream sides with respect to the transfer blade are provided in contact with the outer surface of the transfer belt, and separate the transfer belt from the image carrier. The separation member, the plurality of separation members, and the transfer blade are connected to each other, and the plurality of separation members, the transfer blade, and the belt surface between the plurality of separation members are integrated into the transfer blade and the belt surface. Provided is an image forming apparatus characterized in that a connecting means for moving the transfer belt away from the image carrier by moving in a contact state is provided in each image forming section. .

According to an embodiment of the present invention, protrusions protruding from both ends of the transfer belt below the transfer blade are provided, and the protrusions and the plurality of spacing members are connected by a connecting bar and It is preferable that the protruding portion and the transfer blade are connected by a separate connecting bar .

According to the present invention , in an image carrier provided in an image forming portion of a color that is not used at the time of forming a small- color image, damage caused by abrasion with a transfer belt is reduced, and a long life is achieved. An image forming apparatus that does not cause color misregistration due to displacement or deformation of the transfer blade can be realized.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Reference example 1
The image forming apparatus of this reference example is shown in FIGS. The image forming apparatus used in this example is an image forming apparatus having four process stations 1 of black, cyan, magenta, and yellow as in the conventional example, and using both the tandem method and the intermediate transfer method. Multicolor image formation (full color image formation) in which toner images that are regularly formed are superimposed on each other and small color image formation (monochrome image formation) to form a single color toner image are performed. FIG. 2 shows a state at the time of full-color image formation, but the entire configuration in full-color image formation is the same as the conventional example described with reference to FIG.

  A state at the time of monochrome image formation, which is a characteristic part of the present invention, will be described.

In this reference example , the primary transfer blades 5C, 5M, and 5Y, which are transfer members of the color stations 1C, 1M, and 1Y, are transferred without removing the driving roller 52 of the intermediate belt 50 that is a transfer belt during black and white image formation. The method of separating (removing) from the part (primary transfer part) t has been improved. FIG. 1 shows a state when a monochrome image is formed in this reference example .

In this reference example , in the separation operation for removing the primary transfer blades 5C, 5M, and 5Y at the time of black and white image formation, the intermediate belt surface is provided by the guide rollers G and the bars B that are separation members attached to the primary transfer blade 5. Lower T. This will be described in detail below with reference to FIG.

  FIGS. 3A and 3B show the state of the primary transfer portion t in any of the color stations 1C, 1M, and 1Y. As described in the conventional example, the primary transfer blade 5 is disposed on the photosensitive drum 2 via the intermediate belt 50 constituting the transfer surface T.

Here, in this reference example , the primary transfer blade 5 is connected to the bar B and the roller G, and the bar B and the roller G are configured to move integrally with the primary transfer blade 5. FIG. 3A shows a state during full-color image formation.

  Then, when the primary transfer blade 5 is released downward, as shown in FIG. 3B, the bar B and the roller G are similarly released downward as an integrated object. The primary transfer blade 5 is removed by a conventionally known mechanism using a spring and an eccentric cam (not shown).

In this reference example , since the stations 1 are arranged horizontally, the transfer blade 5 moves downward when detached from the transfer part t. However, if the stations are arranged in other directions, the removal direction is different. It becomes.

  FIG. 4 is a schematic view of such a system as viewed from above.

  Here, the transfer surface T of the intermediate belt 50 rotates in the direction of the arrow in the vicinity of the lower portion of the photosensitive drum 2. The longitudinal direction of the blade 5 is a direction that intersects the traveling direction of the intermediate belt 50, but the bar B projects from both ends of the longitudinal direction of the blade 5, projects to the outside of the belt 50, and rises upward on both sides of the belt 50. It has a bent shape. The bent end Ba extends to above the intermediate belt 50, and a roller G is attached to the end Ba so as to enter the upper center side of the intermediate belt 50. That is, the rollers G attached to the transfer blade 5 are located above the intermediate belt 50 from both sides in the traveling direction of the intermediate belt 50.

  With this configuration, when the transfer blade 5 is released downward during black-and-white image formation, the intermediate belt 50 is caught by the roller G provided on the bar B that is integrated with the blade 5 and is released downward, and is lowered downward. Is completely removed from the photosensitive drum 2. That is, the intermediate belt 50 is configured to be interlocked with the separating operation of the transfer blade 5 by the guide roller G and the bar B which are the separating members.

  Here, with respect to each of the stations 1C, M, and Y other than the black station 1Bk, the separation operation of the intermediate belt 50 described above is performed at the time of monochrome image formation.

  Conventionally, when only the transfer blade 5 has been removed, the photosensitive drum 2 when the apparatus is completely operated in full color without completely preventing the photosensitive drum 2 from being damaged. In the method in which only the primary transfer blade 5 is removed when black and white image formation is performed on 90 out of 100 images, the color stations 1C, 1M, 1Y The life of the drum 2 etc. is 15,000 sheets even though no toner image is formed, and the life is not so long compared to the case where full-color image formation is continued due to drum scratches or the like. It was.

Therefore, as in the present reference example , in the configuration in which the roller G and the bar B are provided on the primary transfer blade 5 and the intermediate belt 50 is detached in conjunction with the primary transfer blade 5, the image formation of 100 sheets is similarly performed. When 90 black and white images were formed, it was possible to extend the life of the color stations 1C, 1M, and 1Y up to 100,000 sheets or more.

  Incidentally, the photosensitive drum 2 of the black and white image forming apparatus at this time is 10,000 sheets, which is naturally the same as the life of full color image formation.

  In addition, the life of the color photosensitive drums 2C, 2M, and 2Y can be improved, and the mechanical life due to scratches and the like can be increased, resulting in a life of 100,000 sheets. Therefore, the photosensitive drum 2 is not in a non-exchange state.

Example 1
In this embodiment, for removing the operating mechanism of the intermediate belt 50 in reference example as shown in FIG. 5 (a), (b) , the roller G across the photosensitive drum 2, the intermediate belt 50 moves Two in total, one each upstream and downstream in the direction.

  With reference to FIG. 5, the mechanism for removing the intermediate body of this example will be described. FIG. 5A shows the wearing state of the intermediate belt 50, and FIG. 5B shows the detached state of the intermediate belt 50.

  In this embodiment, as can be understood with reference to FIG. 6 which is a view seen from above, the bar B2 protruding from both ends in the longitudinal direction of the blade 5 is formed at the end Bc2 protruding from both sides of the intermediate belt 50. The intermediate belt 50 is bent upward, but the bent portion extends in two directions from the protruding portion end Bc2. The tips of the bent portions Ba and Bb extend to the upper side of the intermediate belt 50 on the upstream side and the downstream side in the moving direction of the intermediate belt 50 of the blade 5, respectively. Then, in the portions Ba and Bb bent upward, the rollers Ga (upstream in the moving direction of the intermediate belt 50) and the rollers Gb (downstream in the moving direction of the intermediate belt 50) are directed toward the center of the intermediate belt 50. It is attached.

  When the blade 5 is removed from the intermediate belt 50, the intermediate belt 50 is caught by the rollers Ga and Gb, pulled down by the bar B, and released from the primary transfer portion t. That is, also here, the intermediate belt 50 is detached from the primary transfer portion t in conjunction with the blade 5.

  Here, since the two rollers G are disposed across the primary transfer blade 5, the intermediate belt 50 is lowered flat with respect to the photosensitive drum 2, so that the intermediate belt 50 is stably separated from the photosensitive drum 2. I can do it.

As described above, there is no phenomenon that the photosensitive drum 2 is damaged when the black and white image is formed, and the effect that the life of the drum and the like is extended as in the reference example is obtained.

Example 2
In the low-color image formation, the above-described reference example relates to the monochrome image formation operation, but in this embodiment, the two-color image formation operation will be described.

  FIG. 7 shows an example of red (only magenta and yellow are operated).

  During red image formation, the transfer blades 5Bk and 5C of the black station 1Bk and cyan station 1C are removed from the primary copy portion t.

Since other configurations are the same as those in the first embodiment, detailed description thereof is omitted. As shown in FIG. 7, the black and cyan transfer blades 5Bk and 5C are removed, and the transfer blades 5M and 5Y in the magenta and yellow stations 1M and 1Y are attached. 50 is not in contact with the black and cyan photosensitive drums 2Bk and 2C but is in contact with only the magenta and yellow photosensitive drums 2M and 2Y.

As the mechanism for attaching and detaching the intermediate belt 50 at the black and cyan primary transfer portions tBk and tC in this embodiment, the mechanism described in the first embodiment, in which rollers G are provided upstream and downstream of the blade 5 is employed.

Thus, it is effective not only for the formation of one color image as in the case of black and white image formation but also for the image formation operation of two or more colors. In the case of this example, the effect similar to that of the first embodiment is achieved. When the life of the photosensitive drum 2 is 10,000 sheets, in the two-color image formation, 10,000 sheets are used for magenta and yellow to be used, and 100,000 or more are used for the black and cyan photosensitive drums 2 that are not used. It has a very long life.

In the second embodiment, an example of a certain secondary color is shown. However, even when the color is obtained by mixing three colors such as blue or the like, basically, a transfer blade is worn and used only for the color to be used. The present invention is equally applicable in removing uncolored colors.

The dimensions of the components of the image forming apparatus described Oite in Example 1, 2, or more, materials, shapes, and and relative positions, unless otherwise specifically noted, the scope of the invention only those It is not intended to be limited to. In other words, other types of toner, intermediate belt material, and the like may be used.

  For example, the primary transfer member is a blade, but a conventionally known roller system is similarly provided with a bar and a roller, and a mechanism for pulling down the intermediate belt in the same manner when the intermediate transfer belt is interlocked with the primary transfer member. The effect can be obtained in the same way.

Further, as examples of a plurality of rollers, two examples are shown in Example 1 , but the effect is the same with three or more, and if the intermediate transfer member can be more stably separated from the image carrier, Similar effects can be obtained in other configurations. Further, the separation member is not limited to the above-described bar or roller, and any member may be used as long as it is in contact with the transfer belt and separated from the transfer portion.

  Further, the type of toner and the number of colors of the image to be formed are not limited to this. The present invention is preferably carried out by an intermediate transfer system, in which a recording material, which is a transfer medium, is carried on a transfer belt, which is a transfer material carrier, and is transported to a primary transfer unit and recorded directly from a photosensitive drum. The present invention can also be implemented in a direct transfer system in which an image is superimposed on a material.

FIG. 2 is a schematic configuration diagram illustrating a low-color image formation time by an example of an image forming apparatus according to the present invention. FIG. 2 is a schematic configuration diagram illustrating a multicolor image forming time by an example of an image forming apparatus according to the present invention. It is explanatory drawing which shows an example of the separation operation | movement of the transfer member and transfer belt from the transfer part which concerns on this invention. It is a top view which shows an example of the transfer part which concerns on this invention. It is explanatory drawing which shows the other example of the separation operation | movement of the transfer member and transfer belt from the transfer part which concerns on this invention. It is an upper view which shows the other example of the transfer part which concerns on this invention. It is a schematic block diagram which shows the time of low color image formation by the other example of the image forming apparatus which concerns on this invention. It is a schematic block diagram which shows an example of the conventional image forming apparatus.

Explanation of symbols

1 Process station 2 Photosensitive drum (image carrier)
5 Primary transfer blade (transfer member)
50 Intermediate belt (transfer belt, intermediate transfer body, transfer medium)
t Transfer section B Bar (separating member)
G roller (spacer)

Claims (2)

A plurality of image formations capable of forming toner images of different colors comprising a movable transfer belt, and an image carrier and a transfer blade for transferring a toner image on the image carrier toward the transfer belt The transfer belt is in contact with an image carrier that is used for image formation, and the transfer blade and the transfer belt are in contact with an image carrier that is not used for image formation. In the image forming apparatus in which the transfer belt can be separated in a state,
In the moving direction of the transfer belt, a plurality of upstream and downstream sides with respect to the transfer blade are provided in contact with the outer surface of the transfer belt, and separate the transfer belt from the image carrier. The separation member, the plurality of separation members, and the transfer blade are connected to each other, and the plurality of separation members, the transfer blade, and the belt surface between the plurality of separation members are integrated into the transfer blade and the belt surface. An image forming apparatus comprising: a connecting unit configured to move the transfer belt in a contacted state to separate the transfer belt from the image carrier. Protrusions that protrude from both ends of the transfer belt below the transfer blade are provided, and the protrusions and the plurality of spacing members are connected by a connecting bar, and the protrusion and the transfer blade are separated from each other. The image forming apparatus according to claim 1, wherein the image forming apparatus is connected by a connecting bar.

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