JP2006091087A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain stable cleaning performance for a transfer conveying belt over a long period of time under a practical environmental condition under which an image forming apparatus is used. <P>SOLUTION: A cleaning blade 48 which counter-abuts on the transfer conveying belt 21 transferring a toner image carried by a photoreceptor drum 10 to paper P and conveying the paper P and scrapes an adhesive matter adhering to the surface of the transfer conveying belt 21 is set so that an abutting angle on the transfer conveying belt 21 becomes ≥21° and ≤26°, and also the abutting pressure on the transfer conveying belt 21 becomes ≥1.5g/mm and ≤4.0g/mm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a printer, and more particularly to an image forming apparatus including a transfer conveyance belt that transfers a toner image while electrostatically attracting and conveying a recording sheet.

  In an image forming apparatus such as a copying machine or a printer using an electrophotographic system, for example, a photosensitive member (photosensitive drum) formed in a drum shape is uniformly charged, and the photosensitive drum is controlled based on image information. An electrostatic latent image is formed on the photosensitive drum by exposure with the exposed light. Then, the electrostatic latent image is converted into a visible image (toner image) with toner, and the toner image is transferred from the photosensitive drum to the recording paper by the transfer device, and then heated and pressed by the fixing device to form the toner image. Fixed on recording paper.

In a transfer device used in such an image forming apparatus, in recent years, a transfer conveyance belt is disposed so as to contact a photosensitive drum, and a contact area (transfer nip portion) between the transfer conveyance belt and the photosensitive drum is disposed. A transfer system is used in which the recording paper is nipped and a transfer bias is applied to the transfer conveyance belt to transfer the toner image on the photosensitive drum onto the recording paper.
In the transfer apparatus using such a transfer conveyance belt, a high-voltage power supply is not required as compared with the conventional corona charging method, so that the apparatus can be downsized and the manufacturing cost can be reduced. In addition, there is an advantage that the generation of ozone is extremely small, and in addition, the transfer performance is stable against dirt caused by adhesion of paper dust or toner. Furthermore, it is possible to configure the unit around the transfer conveyance belt so that it can be brought into contact with and separated from the photosensitive drum, or to be pulled out from the front side of the image forming apparatus. Jam processing when jamming occurs is easy. In addition, the occupation area of the image forming apparatus can be reduced.

  However, in the transfer device using the transfer conveyance belt, since the transfer conveyance belt is configured to contact the photosensitive drum at the transfer nip portion, an interimage between the image area and the image area on the photosensitive drum is formed. When the region passes through the transfer nip portion, the transfer conveyance belt and the photosensitive drum are in direct contact with each other without using the recording paper. Therefore, the toner adhering to the inter-image area on the photosensitive drum is transferred onto the transfer / conveying belt, and the surface of the transfer / conveying belt is contaminated with the toner. The toner adhering to the surface of the transfer / conveying belt causes a problem that the back surface of the newly conveyed recording paper is soiled and the image quality is deteriorated. Further, when the transfer / conveying belt carries recording paper, paper dust may adhere to the surface of the transfer / conveying belt. For this reason, in such a transfer device, a belt cleaning device is provided for removing deposits such as toner and paper dust from the surface of the transfer conveyance belt.

Here, as a conventional technique related to a belt cleaning device for cleaning toner adhered to the surface of the transfer conveyance belt, a sponge roll that is rotatable and arranged in sliding contact with the surface of the transfer conveyance belt is provided on the upstream side of the cleaning blade. There is a technique related to a cleaning device having a configuration (see, for example, Patent Document 1).
Further, there is a technique related to a cleaning device having a configuration in which a member capable of electrostatically adsorbing toner adhering to the transfer conveyance belt surface is disposed in contact with the transfer conveyance belt on the downstream side of the cleaning blade (for example, Patent Document 2). reference).

JP-A-10-171270 (page 3-4) JP 2002-365925 (page 3-4)

  As described above, in the belt cleaning device that removes the toner and paper dust adhering to the surface of the transfer / conveyance belt, as in the technique described in Patent Document 1 and Patent Document 2 described above, the surface of the transfer / conveyance belt is brought into contact. The cleaning blade as a main component, and as a supplementary cleaning member, a sponge roll and a member capable of electrostatically adsorbing toner disposed so as to rub the surface of the transfer conveyance belt, and a cleaning brush, etc. The provided configuration is adopted.

However, the transfer conveyance belt is formed of an elastic body such as rubber, and the cleaning blade disposed in contact with the transfer conveyance belt surface is also formed of an elastic body such as rubber. Both frictional forces at the contact portion with the blade are large. In particular, in a high-temperature and high-humidity environment, moisture is adsorbed and the coefficient of friction between the two becomes large, so that the cleaning blade is likely to turn over (blade turning). When the blade is turned over, there is a serious problem that even if an auxiliary cleaning member such as a sponge roll functions, a normal cleaning process cannot be performed.
On the other hand, in the cleaning blade, since the elastic modulus of the rubber is reduced in a low temperature and low humidity environment, the force with which the cleaning blade presses the surface of the transfer conveyance belt is reduced. For this reason, it is difficult to form a proper contact state with the transfer / conveying belt, and it is easy to cause a so-called cleaning failure in which the toner and paper dust attached to the surface of the transfer / conveying belt cannot be sufficiently removed. There was also.

  Accordingly, the present invention has been made to solve the technical problems as described above, and an object of the present invention is to stabilize the transfer and conveyance belt under a practical environmental condition in which the image forming apparatus is used. This is to maintain the cleaning performance for a long time.

  For this purpose, the image forming apparatus of the present invention includes a toner image carrier that carries a toner image, a transfer conveyance belt that transfers the toner image carried by the toner image carrier to a transfer material, and conveys the transfer material. And a cleaning member that counter-contacts the transfer conveyance belt and scrapes off adhering matter adhering to the surface of the transfer conveyance belt. The cleaning member has a contact angle of 21 ° or more and 26 ° with the transfer conveyance belt. The contact pressure to the transfer / conveying belt is set to 1.5 g / mm or more and 4.0 g / mm or less.

  Here, the transfer / conveying belt may be configured such that the base material is formed of a rubber layer. Further, the transfer / conveying belt may be characterized by having a surface roughness (Rz) of 2.5 μm or less. Furthermore, the transfer / conveying belt may have a structure in which a surface layer made of urethane resin or urethane resin in which polytetrafluoroethylene is dispersed is formed. In addition, the transfer conveyance belt is configured to be stretched between at least one pair of rolls, and the cleaning member is in contact with the transfer conveyance belt in a region where the transfer conveyance belt is stretched between the rolls. it can. Further, the cleaning member may be made of urethane rubber.

  The image forming apparatus of the present invention includes a toner image carrier that carries a toner image, and a transfer conveyance belt that is stretched between at least one pair of rolls, and transfers the toner image carried by the toner image carrier. A transfer conveyance belt for transferring to the material and conveying the transfer material; and a cleaning blade for cleaning the deposit by contacting the transfer conveyance belt with an edge surface, and the transfer conveyance belt is stretched around a roll. In the region, the contact angle with the transfer conveyance belt is 21 ° or more and 26 ° or less, and the contact pressure to the transfer conveyance belt is 1.5 g / mm or more and 4.0 g / mm or less, It is characterized by being in contact with the transfer conveyance belt and a counter.

  Here, a cleaning brush for cleaning the adhering matter adhering to the surface of the transfer conveyance belt while rotating may be further provided on the upstream side of the cleaning blade in the conveyance direction of the transfer conveyance belt. The cleaning blade may be in contact with the transfer conveyance belt from below in the vertical direction. Further, the toner image carrier may be characterized in that the toner image to be carried is formed by toner prepared by a polymerization method. Furthermore, the transfer conveyance belt may be characterized in that the transfer material is conveyed at a conveyance speed of 350 mm / sec or more.

  As an effect of the present invention, the cleaning blade is prevented from being turned up under a high-temperature and high-humidity environment, and good cleaning can be performed over a long period of time. In addition, stable cleaning performance can be exhibited even in a low temperature and low humidity environment, and the occurrence of defective cleaning can be suppressed.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus to which the exemplary embodiment is applied. The image forming apparatus shown in FIG. 1 includes a charger 11 that charges the photosensitive drum 10 around the photosensitive drum 10 as an example of a toner image carrier that rotates in the direction of arrow A, and an electrostatic image on the photosensitive drum 10. Laser exposure device 12 for writing the latent image (exposure beam is indicated by Bm in the figure), developing device 13 for storing the toner and making the electrostatic latent image on the photosensitive drum 10 visible with the toner, transfer unit Before the electrostatic transfer at 15, a pre-transfer charger 14 that charges the toner image on the photosensitive drum 10, and the toner image formed on the photosensitive drum 10 is a recording paper (paper) P that is a recording paper in the transfer unit 15. A transfer unit 20 for transferring the toner image, an image density sensor 18 for adjusting an image density disposed in the vicinity of the photosensitive drum 10 on the downstream side of the transfer unit 15, and a charge amount of residual toner after electrostatic transfer is reduced. Chestnut Training electrifier 16 for electrophotography and a drum cleaner 17 which residual toner on the photosensitive drum 10 is removed is provided. Further, a fixing device 60 for fixing the unfixed toner image transferred onto the paper P and a control unit 30 for controlling the operation of each device (each unit) are provided.

  The transfer unit 20 is disposed inside the transfer conveyance belt 21 stretched between the drive roll 22 and the idle roll 23, and is in pressure contact with the photosensitive drum 10 via the transfer conveyance belt 21. And a transfer roll 24. Further, it has a function of transferring the toner image on the photosensitive drum 10 to the paper P conveyed to the transfer unit 15 and a function of conveying the paper P on which the toner image has been transferred in the transfer unit 15 to the fixing device 60. is doing.

  The image forming apparatus according to the present embodiment also includes a paper tray 50 that stores paper P, a pickup roll 51 that picks up and transports the paper P accumulated in the paper tray 50 at a predetermined timing, and a pickup as a paper transport system. A transport roll 52 that transports the paper P fed by the roll 51, a registration roll 54 that feeds the transported paper P to the transfer unit 15 at a predetermined timing, and a transport that guides the paper P transported by the transport roll 52 to the registration roll 54. A chute 53, an inlet chute 55 that guides the paper P fed from the registration roll 54 to the transfer unit 15, and a fixing inlet guide 56 that guides the paper P on which the toner image is transferred by the transfer unit 20 to the fixing device 60 are provided. ing.

  Next, a basic image forming process of the image forming apparatus according to the present embodiment will be described. In the image forming apparatus as shown in FIG. 1, image data output from an image reading device (IIT) not shown or a personal computer (PC) not shown is subjected to predetermined image processing by an image processing device not shown. . In the image processing apparatus, the input reflectance data is subjected to predetermined image processing such as various kinds of image editing such as shading correction, position shift correction, gamma correction, frame deletion editing, and movement editing. The image data that has undergone image processing is output to the laser exposure unit 12.

The laser exposure unit 12 irradiates the photosensitive drum 10 with an exposure beam Bm emitted from, for example, a semiconductor laser, according to the input image data. The surface of the photosensitive drum 10 is charged to a predetermined charging potential (for example, −750 V) by a charger 11 made of scorotron, and then the surface is scanned and exposed by the laser exposure device 12 to form an electrostatic latent image. The
The formed electrostatic latent image is reversely developed with negatively charged toner by the developing device 13. That is, for example, a direct current from a power source (not shown) is applied to a developer carrying member (developing sleeve) 13a carrying a developer prepared by a polymerization method and having a toner having a shape factor SF1 of 100 to 140 mixed with a carrier made of magnetic particles. A developing bias composed of a voltage or a developing bias in which a DC voltage is superimposed on an AC voltage is applied, and a developing electric field is formed between the photosensitive drum 10 and the developing bias. As a result, the toner on the developing sleeve 13a is transferred to the image portion (exposure portion) of the electrostatic latent image, and the electrostatic latent image is visualized.

  Here, in the image forming apparatus according to the present embodiment, a setup cycle is executed every predetermined cycle. That is, prior to the actual image forming operation, a predetermined patch area is developed under predetermined conditions. At that time, as will be described later, the transfer conveyance belt 21 of the transfer unit 20 is set to be separated from the photosensitive drum 10. In this state, the developed patch area passes through the transfer section 15 as it is, and the density of the toner image in the patch area is measured by the image density sensor 18 disposed on the downstream side of the transfer section 15. The toner density signal measured by the image density sensor 18 is sent to the control unit 30. Then, in accordance with an instruction from the control unit 30 based on the signal from the image density sensor 18, the charging potential of the photosensitive drum 10 by the charger 11 and / or the developing bias value applied to the developing device 13 is adjusted, and a predetermined image is obtained. The density is set to be maintained.

  Next, in the actual image forming operation, when the toner image formed on the photosensitive drum 10 is conveyed to the transfer unit 15 where the photosensitive drum 10 and the transfer unit 20 abut, The pickup roll 51 rotates in accordance with the timing at which the toner image is conveyed to the transfer unit 15, and a predetermined size of paper P is supplied from the paper tray 50. The paper P supplied by the pickup roll 51 is transported by the transport roll 52, and reaches the registration roll 54 through the transport chute 53. In the registration roll 54, the paper P is temporarily stopped, and the registration roll 54 rotates in accordance with the movement timing of the photosensitive drum 10 carrying the toner image. Thereby, the position of the paper P and the position of the toner image are aligned, and the paper P is sent out from the inlet chute 55 to the transfer unit 15.

In the transfer unit 15, the sheet P conveyed at the same timing is sandwiched between the photosensitive drum 10 and the transfer roll 24 via the transfer conveyance belt 21 of the transfer unit 20. At that time, a voltage (transfer bias) having a polarity opposite to the charging polarity of the toner (here, negative polarity) is applied to the transfer roll 24, so that the transfer roller 24 is transferred to the transfer conveyance belt 21 on the photosensitive drum 10. A charge having a polarity opposite to that of the toner is applied. As a result, the unfixed toner image carried on the photoconductor drum 10 is electrostatically transferred onto the paper P in the transfer unit 15 pressed by the photoconductor drum 10 and the transfer roll 24.
At this time, an optimum transfer bias is applied to the transfer roll 24 by a constant current method. Further, the optimum transfer current supplied from the transfer roll 24 at that time is 75 to 120 μA, although it varies depending on the process speed, environmental conditions such as temperature and humidity, the type of the paper P, and the like.

Thereafter, the sheet P on which the toner image has been electrostatically transferred is peeled off and conveyed from the photosensitive drum 10 while being electrostatically attracted to the transfer conveyance belt 21 of the transfer unit 20, and downstream of the transfer unit 20 in the sheet P conveyance direction. To the fixing device 60 provided on the side. When the sheet P is not peeled off from the photosensitive drum 10 and remains adsorbed on the photosensitive drum 10, it is disposed near the surface of the photosensitive drum 10 on the downstream side of the transfer unit 15. The paper P is separated from the photosensitive drum 10 by a separation claw (not shown) and is electrostatically attracted to the transfer conveyance belt 21.
At the rear end of the transfer conveyance belt 21 on the fixing device 60 side, the sheet P is peeled from the transfer conveyance belt 21 due to the curvature when the transfer conveyance belt 21 is wound around the drive roll 22 and the stiffness of the sheet P. Then, the paper P is guided to the fixing inlet guide 56 and conveyed to the fixing device 60.
The unfixed toner image on the paper P conveyed to the fixing device 60 is fixed on the paper P by being subjected to fixing processing by heat and pressure in the fixing device 60. Then, the paper P on which the fixed image is formed is conveyed to a paper discharge mounting portion provided in a discharge portion of the image forming apparatus, and a series of image forming operations is completed.

  The image forming apparatus according to the present embodiment is configured to form a single color toner image. However, the present invention is a color that forms a color toner image by superimposing, for example, yellow, magenta, cyan, and black toner images. It can also be applied to an image forming apparatus.

Next, the transfer unit 20 will be described in detail.
FIG. 2 is a cross-sectional view showing the configuration of the transfer unit 20. As shown in FIG. 2, the transfer unit 20 transfers the toner image on the photosensitive drum 10 onto the paper P, and also transfers the transfer transport unit 20A and the transfer transport unit 20A for transporting the paper P on which the toner image has been transferred. A retract mechanism 20B that contacts and separates from the body drum 10, a cleaning unit 20C as an example of a belt cleaning unit that removes adhering substances such as paper dust and toner attached to the transfer conveyance unit 20A, and a transfer unit for transferring the conveyed paper P 15 includes an inlet chute portion 20 </ b> D leading to 15.

  FIG. 3 is a perspective view showing the configuration of the transfer unit 20. As shown in FIG. 3, the transfer conveyance unit 20 </ b> A of the transfer unit 20 is stretched around the transfer conveyance belt 21 and the transfer conveyance belt 21 arranged in the axial direction of the photosensitive drum 10, and rotates in the arrow B direction. A drive roll 22 that is moved, an idle roll 23 that stretches the transfer conveyance belt 21 to apply a predetermined tension, and a transfer roll 24 that forms a transfer electric field with the photosensitive drum 10 to transfer a toner image onto the paper P. It is comprised by.

  The transfer / conveying belt 21 is composed of, for example, two layers including a rubber layer based on chloroprene and a surface layer obtained by coating a resin mainly composed of urethane with polytetrafluoroethylene (PTFE) particles dispersed therein. Is an endless belt. Further, the surface of the transfer / conveying belt 21 has a surface roughness Rz of 2.5 μm or less. The transfer / conveying belt 21 is driven at the same speed as the surface speed of the photosensitive drum 10 by a driving roll 22 configured to be driven by a coupling from a driving motor (not shown) on the image forming apparatus main body side. It rotates in the direction of arrow B.

The transfer roll 24 is formed of a tube of EPDM and NBR blend rubber with carbon dispersed on the surface and a roll of EPDM foam rubber with carbon dispersed on the inside, and the hardness is, for example, 20 to 50 ° (Asker C: 4. 9N load). Furthermore, the resistance is set to 5.0 to 7.0 logΩ. A transfer bias having a polarity (positive polarity) opposite to the toner charging polarity (negative polarity) is stably applied to the transfer roll 24 from a transfer power source (not shown). As a result, a charge having a polarity opposite to the toner charging polarity on the photosensitive drum 10 is applied from the transfer roll 24 to the transfer conveyance belt 21.
In addition, the transfer conveyance unit 20A is configured such that the idle roll 23 side is swung by the retract mechanism unit 20B with the drive roll 22 as the rocking center, and is configured to be able to contact and separate from the photosensitive drum 10.

  Next, the retract mechanism unit 20B is disposed below the transfer conveyance unit 20A. FIG. 4 is a perspective view illustrating a configuration in a state where the transfer conveyance unit 20 </ b> A is removed from the transfer unit 20. As shown in FIG. 4, the retract mechanism unit 20B is disposed at both ends in the width direction of the transfer conveyance unit 20A. The retraction mechanism unit 20B pushes up and down while supporting the idle roll 23 of the transfer conveyance unit 20A. A plate 31 is fixedly provided, and includes a link shaft 32 that swings the contact / separation plate 31, a swing arm 33 that is connected to the center of the link shaft 32, and a DC solenoid 34 that drives the swing arm 33 to swing. Yes. In the retract mechanism 20B, when a current is passed through the direct current solenoid 34, the direct current solenoid 34 moves the swing arm 33 in a downward direction. As a result, the link shaft 32 connected to the swing arm 33 rotates, and the contact / separation plates 31 fixed to both ends of the link shaft 32 swing upward.

  In the transfer unit 20, the transfer conveyance unit 20 </ b> A is set in a state of being separated from the photosensitive drum 10 at the time of measuring the toner image density in the patch area (setup cycle) or in the standby state of the image forming apparatus. FIG. 5 is a diagram illustrating a state where the transfer conveyance unit 20 </ b> A is separated from the photosensitive drum 10. As shown in FIG. 5, during the setup cycle of the image forming apparatus or during standby, the DC solenoid 34 of the retract mechanism unit 20B is not energized, and the swing arm 33 connected to the DC solenoid 34 is pushed up. Is set to the correct position. Therefore, the link shaft 32 connected to the swing arm 33 positions the contact / separation plates 31 fixed to both ends of the link shaft 32 downward. Since both ends of the idle roll 23 of the transfer conveyance unit 20A are supported by the contact / separation plate 31, the transfer conveyance unit 20A is set in a state of being separated from the photosensitive drum 10 by the contact / separation plate 31.

  On the other hand, during a normal image forming operation, the transfer conveyance unit 20A is set in a state of being in contact with the photosensitive drum 10. FIG. 6 is a diagram illustrating a state where the transfer conveyance unit 20 </ b> A is in contact with the photosensitive drum 10. During the image forming operation, the paper P that has been fed to the registration roll 54 and has been waiting is sent out by the registration roll 54 in accordance with the movement timing of the photosensitive drum 10 carrying the toner image. At that time, the sensor (not shown) detects that the leading end of the paper P is guided to the inlet chute 55 and has reached the vicinity of the contact portion between the photosensitive drum 10 and the transfer conveyance belt 21. When the control unit 30 inputs a signal from this sensor, the control unit 30 turns on the DC solenoid 34 of the retract mechanism unit 20B and starts energization. As a result, the DC solenoid 34 moves the swing arm 33 in a downward direction. When the swing arm 33 is pushed down, the link shaft 32 connected to the swing arm 33 rotates, and the contacting / separating plates 31 fixed to both ends of the link shaft 32 swing upward. Then, the idle roll 23 of the transfer conveyance unit 20 </ b> A whose both end portions are supported by the contact / separation plate 31 is set in a state of being in contact with the photosensitive drum 10. At that time, a nip portion is formed at a contact portion between the photosensitive drum 10 and the transfer conveyance belt 21.

  When the transfer conveyance unit 20 </ b> A comes into contact with the photosensitive drum 10, the paper P on the transfer conveyance belt 21 conveyed by the rotation drive of the drive roll 22 enters the nip portion between the photosensitive drum 10 and the transfer conveyance belt 21. A transfer bias having a polarity (positive polarity) opposite to the toner charging polarity (negative polarity) is applied to the transfer roll 24 from a transfer power source (not shown). As a result, a charge having a polarity opposite to the toner charging polarity on the photosensitive drum 10 is applied to the transfer / conveying belt 21. Then, the toner on the photosensitive drum 10 is transferred to the paper P. Thereafter, the paper P is transported in a state of being electrostatically attracted to the transfer transport belt 21 and sent to the fixing device 60.

The inlet chute 20D is disposed upstream of the transfer conveyance unit 20A in the transfer unit 20, and is integrally joined to the housing 70. The photosensitive drum inlet chute 55a integrally formed with the photosensitive drum unit that supports the photosensitive drum 10 and the resist roll inlet chute 55b integrally formed with the resist roll unit that supports the resist roll 54 (FIG. Inlet chute 55 is configured in combination with an upper inlet chute consisting of 1). In this case, the inlet chute 20D constitutes the lower inlet chute of the inlet chute 55. That is, the inlet chute 55 is composed of a separate upper inlet chute and lower inlet chute, and the lower inlet chute is integrally configured with the transfer unit 20 as an inlet chute portion 20D.
The inlet chute 55 supports one surface (lower surface) of the paper P conveyed from the resist roll 54 by the inlet chute 20D, and the other surface (upper surface) of the photosensitive drum inlet chute 55a and the resist roll. While being regulated by the inlet chute 55b, it is carried into the nip portion between the photosensitive drum 10 and the transfer conveyance belt 21 in the transfer portion 15 while maintaining an accurate posture without being inclined.

Next, the cleaning unit 20C will be described.
As shown in FIG. 2, the cleaning unit 20 </ b> C is configured to remove the adhering matter adhered to the cleaning brush 41 and the cleaning brush 41 by wiping off adhering matters such as paper dust and toner adhering to the surface of the transfer conveying belt 21 of the transfer conveying unit 20 </ b> A. A flicker bar 42 disposed so as to bite into the cleaning brush 41 in order to knock it down, and disposed on the downstream side of the cleaning brush 41 in the transport direction of the transfer transport belt 21, and deposits on the surface of the transfer transport belt 21. A cleaning blade 43 as an example of a cleaning member to be scraped off, a cleaning brush 41 and a cleaning box 44 that receives the paper dust and toner removed from the surface of the transfer conveyance belt 21 by the cleaning blade 43, a paper dust and toner in the cleaning box 44, etc. To a recovery bottle (not shown) Recovery coil 45 to feed, is constituted by a blade holder 46 as a supporting member for supporting the cleaning blade 43.

The cleaning brush 41 is a brush roll formed on a surface of carbon-dispersed polyester fiber (volume resistivity: 4.0 to 6.0 log Ωcm) having a thickness of, for example, 10 denier and a fiber density of 30 K / inch ^2. The conveyor belt 21 is configured to rotate in the forward direction and the transport direction. Further, the brush fibers of the cleaning brush 41 are formed so as to be inclined in the forward direction with respect to the conveyance direction of the transfer conveyance belt 21.
On the other hand, the cleaning blade 43 is a plate-like member made of urethane rubber having a thickness of 2 mm, for example, and is disposed in counter contact with the transfer conveyance belt 21. In addition, one end of the cleaning blade 43 in the width direction is bonded to the blade holder 46, and the free length in the width direction toward the transfer conveyance belt 21 is set to 10 mm.

The cleaning brush 41 wipes off adhering material such as paper dust and toner adhering to the surface of the transfer conveyance belt 21 while rotating in the forward direction with respect to the transfer conveyance belt 21 during image formation. Are collected from the surface of the transfer / conveyance belt 21 to the cleaning box 44, and have a function of reducing the adhesion force of the adhered matter to the surface of the transfer / conveyance belt 21.
Further, the cleaning blade 43 disposed on the downstream side of the cleaning brush 41 scrapes off deposits that could not be wiped off by the cleaning brush 41 and collects them in the cleaning box 44.

  Further, the collection coil 45 conveys paper dust, toner, and the like in the cleaning box 44 to a collection bottle (not shown) outside the transfer unit 20 while rotating in the direction of arrow C in FIG. The collection coil 45 is in the direction of arrow C, that is, in the direction away from the fixing device 60 side of paper dust and toner collected on the bottom surface of the cleaning box 44 (upstream side in the direction of conveying the paper P of the transfer conveyance belt 21). By rotating so as to be moved, paper dust, toner, and the like are conveyed along the side wall 44a in the cleaning box 44 on the side opposite to the fixing device 60 side. Therefore, the collected toner is difficult to receive heat from the fixing device 60, and the fusion between the toners can be suppressed. Therefore, the collected paper powder, toner, and the like can be smoothly conveyed to the collection bottle. .

Here, the setting conditions for the transfer conveyance belt 21 of the cleaning blade 43 will be described.
FIG. 7 is a cross-sectional configuration diagram illustrating a state in which the cleaning blade 43 is in contact with the transfer conveyance belt 21. As shown in FIG. 7, the cleaning blade 43 is an area where the transfer conveyance belt 21 is wrapping the drive roll 22, that is, an area where the drive roll 22 supports the transfer conveyance belt 21 behind. It arrange | positions so that the front-end | tip edge part may contact | abut. At that time, the cleaning blade 43 is disposed so as to come into counter contact with the transfer conveyance belt 21. As described above, the cleaning blade 43 can be stably brought into counter contact with the transfer conveyance belt 21 by being configured to contact the transfer conveyance belt 21 in the region where the driving roll 22 is wrapped.
The cleaning blade 43 has a contact angle with the transfer conveyance belt 21 set to 21 ° or more and 26 ° or less, and a contact pressure against the transfer conveyance belt 21 is 1.5 g / mm or more. It is characterized by being set to 4.0 g / mm or less. Here, the contact angle with the transfer conveyance belt 21 is an angle (θ in FIG. 7) between the tangent line of the transfer conveyance belt 21 and the cleaning blade 43 at a position where the cleaning blade 43 contacts the transfer conveyance belt 21. Say. The contact pressure against the transfer / conveying belt 21 refers to a pressure per unit length at which the cleaning blade 43 presses the transfer / conveying belt 21 in the normal direction.

By the way, as described above, in the transfer unit 20 of the present embodiment, the transfer conveyance belt 21 is formed with a rubber layer as a base, and a surface layer mainly composed of urethane resin is formed on the outer surface thereof. On the other hand, the cleaning blade 43 is also made of rubber such as urethane rubber. Further, in the transfer / conveying belt 21, since the surface layer of the transfer / conveying belt 21 is formed of urethane resin or the like, it is difficult to finish the surface smoothly like a mirror surface, and some surface roughness is generated. . Due to such a configuration, a large frictional force acts on the contact portion between the transfer conveyance belt 21 and the cleaning blade 43.
That is, in the drum cleaner 17 for cleaning the general photosensitive drum 10, the surface of the photosensitive drum 10 is formed of a hard resin such as polycarbonate, and the surface smoothness is extremely high. The frictional force when contacted is relatively small. On the other hand, in the cleaning unit 20C of the present embodiment, the elastic members such as rubber are in contact with each other, and the surface of the transfer conveyance belt 21 is not smooth. The power is great. For this reason, the cleaning blade 43 tends to bend and bend when it is dragged in the moving direction of the transfer conveyance belt 21, and if the contact pressure is set low to avoid the blade turning, a so-called poor cleaning that cannot be sufficiently cleaned is caused. It tends to occur. In particular, in a toner having a small particle diameter and a high adhesion to the transfer / conveying belt 21 such as a toner produced by a polymerization method, cleaning failure tends to occur. Further, when the process speed increases as the speed of the image forming apparatus increases, the frictional force between the transfer conveyance belt 21 and the cleaning blade 43 becomes even greater.

  Therefore, in the cleaning unit 20C of the present embodiment, by setting the cleaning blade 43 under the optimum conditions corresponding to the state where a high frictional force acts, both the occurrence of blade turning and poor cleaning are simultaneously suppressed, High cleaning performance can be maintained. In particular, even when the adhering force of the adhering material to the transfer / conveying belt 21 is strong as in the case where a polymer toner having a small particle diameter is used as the toner, the scraping effect of the cleaning blade 43 is enhanced and the adhering material is put into practical use. In addition, it can be sufficiently removed. In addition, it is possible to exhibit stable cleaning performance in response to an increase in the speed of the image forming apparatus.

  First, the contact angle of the cleaning blade 43 with the transfer conveyance belt 21 will be described. Here, in order to find the optimum contact angle, the blade contact angle of the cleaning blade 43 with respect to the transfer conveyance belt 21 was changed to evaluate whether or not cleaning failure occurred and whether or not blade turning occurred. Various conditions in this case are as follows. That is, the surface layer of the transfer conveyance belt 21 is a urethane resin in which PTFE is dispersed, and the surface roughness is Rz (10-point average roughness) = 2.5 μm. The cleaning blade 48 was made of urethane rubber. The tested environment was performed under high temperature and high humidity 28 ° C./85% RH (Relative Humidity) and low temperature and low humidity 10 ° C./15% RH. The transfer current supplied from the transfer roll 24 to the transfer conveyance belt 21 at that time was fixed at 85 μA in a 28 ° C./85% RH environment and fixed at 90 μA in a 10 ° C./15% RH environment. Further, the process speed of the image forming apparatus was set to 400 mm / sec, and a polymerized toner having a shape factor SF1 = 127 to 132 was used as the toner. Then, at each blade contact angle, the test was performed by setting the blade contact pressure in the range of 1.5 to 4.0 g / mm, each with 6 conditions at intervals of 0.5 g / mm.

  The result is shown in FIG. As shown in FIG. 8, in a low temperature and low humidity 10 ° C./15% RH environment, a cleaning failure occurred at a blade contact angle of 20 ° or less. This is because the elastic modulus of the cleaning blade 43 decreases in a low-temperature, low-humidity 10 ° C./15% RH environment, and when the blade contact angle is 20 ° or less, the cleaning blade 43 is sufficiently scraped off. This is probably because the edge does not contact the transfer / conveying belt 21 sufficiently strongly. On the other hand, when the blade contact angle was 21 ° or more, cleaning could be performed satisfactorily. Therefore, in a low temperature and low humidity 10 ° C./15% RH environment, the blade contact angle is preferably set to 21 ° or more.

Further, under the environment of high temperature and high humidity of 28 ° C./85% RH, the cleaning failure of the discharge product occurred at the blade contact angle of 19 ° or less. Here, the discharge product is a substance generated by discharge by the charger 11 that charges the photosensitive drum 10, and is finer than the toner, and is transferred from the photosensitive drum 11 to the transfer conveyance belt 21 and attached. Is. When the blade contact angle is 19 ° or less, such a discharge product tends to slip through, which is not preferable. Further, blade turning occurred at a blade contact angle of 27 ° or more. This is because the cleaning blade 43 and the transfer / conveying belt are at a blade contact angle of 27 ° or more in a state where the friction coefficient between the cleaning blade 43 and the transfer / conveying belt 21 is high in a high temperature and high humidity 28 ° C./85% RH environment. This is considered to be due to the fact that the frictional force with 21 produced a limit. On the other hand, when the blade contact angle was 20 ° or more and 26 ° or less, cleaning could be performed satisfactorily. Therefore, in a high temperature and high humidity 28 ° C./85% RH environment, the blade contact angle is preferably set to 20 ° or more and 26 ° or less.
From these results, the blade contact angle is optimally set to 21 ° or more and 26 ° or less.

  Next, the contact pressure of the cleaning blade 43 against the transfer conveyance belt 21 will be described. Here, in order to find the optimum contact pressure, the blade contact pressure of the cleaning blade 43 with respect to the transfer conveyance belt 21 was changed to evaluate the occurrence of cleaning failure and the occurrence of blade turning. The conditions in this case are the same as in the case of the blade contact angle. However, the blade contact angle is within the optimum range of the blade contact angle described above under the environment of high temperature and high humidity of 28 ° C./85% RH. The angle was set to 26 °, which is most disadvantageous for turning the blade, and in an environment of low temperature and low humidity of 10 ° C./15% RH, it was set to 21 °, which was the most disadvantageous for cleaning failure in the optimum range of blade contact angle. The blade contact pressure was adjusted by the amount of biting into the transfer / conveying belt 21.

  The result is shown in FIG. As shown in FIG. 9, in a low temperature and low humidity 10 ° C./15% RH environment, a cleaning failure occurred at a blade contact pressure of 1.0 g / mm or less. This is because the elastic modulus of the cleaning blade 43 decreases in a low-temperature, low-humidity 10 ° C./15% RH environment, and when the blade contact pressure is 1.0 g / mm or less, the toner adhering to the transfer conveyance belt 21 is scraped off. This is considered to be because the edge of the blade 43 does not contact the transfer / conveying belt 21 sufficiently strongly. On the other hand, when the blade contact pressure was 1.5 g / mm or more, cleaning could be performed satisfactorily. Therefore, it is preferable to set the blade contact pressure to 1.5 g / mm or more in a low temperature and low humidity 10 ° C./15% RH environment.

Further, in a high temperature and high humidity 28 ° C./85% RH environment, discharge product cleaning failure occurred when the blade contact pressure was 1.0 g / mm or less. Thus, when the blade contact pressure is 1.0 g / mm or less, the discharge product easily slips through, which is not preferable. Further, when the blade contact pressure was 4.5 g / mm or more, blade turning occurred. This is because when the blade contact pressure is 4.5 g / mm or more and the friction coefficient of the cleaning blade 43 and the transfer conveyance belt 21 is high in a high temperature and high humidity 28 ° C./85% RH environment, It is considered that the frictional force with the transfer / conveying belt 21 has a limit. On the other hand, when the blade contact pressure was 1.5 g / mm or more and 4.0 g / mm or less, cleaning could be performed satisfactorily. Therefore, in a high temperature and high humidity 28 ° C./85% RH environment, the blade contact pressure is preferably set to 1.5 g / mm or more and 4.0 g / mm or less.
From these results, the blade contact pressure is optimally set to 1.5 g / mm or more and 4.0 g / mm or less.

  Thus, the cleaning blade 48 has a blade contact angle of 21 ° or more and 26 ° or less, a blade contact pressure of 1.5 g / mm or more, and 4.0 g / mm. By setting as follows, it is possible to simultaneously suppress both the occurrence of blade turning in a high temperature and high humidity environment and the poor cleaning in a low temperature and low humidity environment. At that time, sufficient cleaning performance can be maintained even if polymerized toner having high adhesion to the transfer / conveying belt 21 is used, and sufficient cleaning performance is exhibited even in a setting where the process speed is set to 400 mm / sec. can do. In the setting of the cleaning blade 48, it has been confirmed that sufficient cleaning performance is exhibited even in a model having a process speed of 350 mm / sec or more.

In addition to this setting, in the present embodiment, the cleaning blade 48 is configured to contact the transfer conveyance belt 21 from below in the vertical direction. Therefore, at the contact portion between the cleaning blade 48 and the transfer / conveying belt 21, the scraped toner falls, so that the toner does not easily stay and the push-through pressure due to toner accumulation does not increase. Thereby, it is possible to further obtain an effect of suppressing the occurrence of defective cleaning.
Further, a cleaning brush 41 is disposed on the upstream side of the cleaning blade 48. The cleaning brush 41 also has a function of reducing the adhesion force to the transfer / conveyance belt 21 by the disturbing action of the cleaning brush 41 with respect to an adhesion matter having a strong adhesion force to the transfer / conveyance belt 21 such as polymerized toner. Yes. Therefore, the cleaning performance with the cleaning blade 48 is further enhanced by the cleaning brush 41.

  Then, the surface material (OC agent: Over Coating) which forms the surface layer of the transfer conveyance belt 21 was examined. As a surface layer formed on the surface of the rubber layer made of chloroprene serving as a base of the transfer conveyance belt 21, using a urethane resin, a resin in which PTFE particles are dispersed in a urethane-based resin, a fluororesin, and a melanin resin, The presence or absence of defective cleaning and the presence or absence of blade turning were evaluated. The conditions in this case are the same as in the case of the blade contact angle. However, in the environment of high temperature and high humidity of 28 ° C./85% RH, the blade contact angle and the blade contact pressure are respectively the blade contact angle described above. In the optimum range of blade contact pressure, the blade contact angle and blade contact are set to 26 ° and 4.0 g / mm, which are the most disadvantageous for turning the blade, and in a low temperature and low humidity 10 ° C / 15% RH environment. The pressure was set to 21 °, 1.5 g / mm, which is the most disadvantageous for the poor cleaning within the optimum pressure range.

The result is shown in FIG. As shown in FIG. 10, both the urethane resin and the resin mainly containing urethane dispersed PTFE particles showed good results in cleaning performance. On the other hand, when fluororesin was used, even if the blade contact angle and the blade contact pressure were set within the optimum ranges described above, a cleaning failure occurred in a low temperature and low humidity 10 ° C./15% RH environment. . In addition, even when melanin resin is used, even if the blade contact angle and the blade contact pressure are set within the optimum ranges described above, cleaning failure occurs in a low-temperature, low-humidity 10 ° C / 15% RH environment. Even under high-temperature and high-humidity 28 ° C./85% RH environment, discharge products were poorly cleaned.
From these results, the surface material for forming the surface layer of the transfer conveyance belt 21 is optimally obtained by dispersing PTFE particles in a urethane resin and a resin mainly composed of urethane. In consideration of the transfer performance, the one in which PTFE particles are dispersed in a resin mainly composed of urethane is the most excellent.

  In addition, the surface roughness of the transfer conveyance belt 21 was examined. Here, in order to find an acceptable surface roughness of the transfer / conveyance belt 21, the use of the transfer / conveyance belt 21 having a different surface roughness (Rz) was used to evaluate the occurrence of defective cleaning and the occurrence of blade turning. . The conditions in this case are the same as in the case of the blade contact angle. However, in the environment of high temperature and high humidity of 28 ° C./85% RH, the blade contact angle and the blade contact pressure are respectively the blade contact angle described above. In the optimum range of blade contact pressure, the blade contact angle and blade contact are set to 26 ° and 4.0 g / mm, which are the most disadvantageous for turning the blade, and in a low temperature and low humidity 10 ° C / 15% RH environment. The pressure was set to 21 °, 1.5 g / mm, which is the most disadvantageous for the poor cleaning within the optimum pressure range.

FIG. 11 shows the result. As shown in FIG. 11, when the surface roughness Rz was 2.5 μm or less, the cleaning performance was good. It should be noted that when the surface roughness Rz is 0.5 μm or less, the friction coefficient increases in an environment of high temperature and high humidity 28 ° C./85% RH, and the driving torque of the transfer conveyance belt 21 is the surface roughness Rz = 2.5 μm. Although it was higher by 50%, the cleaning performance showed good results. On the other hand, when the surface roughness Rz is 3.0 μm, cleaning is performed in a low-temperature, low-humidity 10 ° C./15% RH environment even if the blade contact angle and blade contact pressure are set within the optimum ranges described above. A defect occurred. In addition, when the surface roughness Rz was 3.5 μm, in addition, the discharge product was poorly cleaned in a high temperature and high humidity 28 ° C./85% RH environment.
From these results, it is optimal to set the surface roughness (Rz) of the transfer conveyance belt 21 to 2.5 μm or less.

Here, the cleaning blade 43 was set to the optimum conditions described above, and a running test using an image forming apparatus was performed in a high temperature and high humidity 28 ° C./85% RH environment and a low temperature and low humidity 10 ° C./15% RH environment. As a result, even if the number of prints reaches 600 kpv (kilo print volume), blade turning in a high temperature / high humidity 28 ° C./85% RH environment and cleaning failure in a low temperature / low humidity 10 ° C./15% RH environment do not occur. It was.
On the other hand, regarding the cleaning blade 43, the blade contact angle was 21 ° or more and 26 ° or less, and the blade contact pressure was out of the range of 1.5 g / mm or more and 4.0 g / mm or less. In the case of setting, blade turning, cleaning failure, etc. occurred within the print count of 200 kpv.

As described above, in the image forming apparatus according to the present embodiment, the cleaning blade 43 transfers and conveys the cleaning blade 43 that is in contact with the transfer and conveyance belt 21 and cleans the toner and the like attached to the surface of the transfer and conveyance belt 21. The contact angle with the belt 21 is set to 21 ° or more and 26 ° or less, and the contact pressure of the cleaning blade 43 to the transfer conveyance belt 21 is set to 1.5 g / mm or more and 4.0 g / mm or less. It is set. By setting in this way, the transfer conveyance belt 21 whose base is formed of a rubber layer and the cleaning blade 43 formed of rubber receive a high frictional force at the abutting portion, thereby corresponding to a high frictional force. The cleaning blade 43 can be set under optimum conditions. Therefore, it is possible to maintain high cleaning performance by suppressing the occurrence of blade turning in a high temperature and high humidity environment and the occurrence of defective cleaning in a low temperature and low humidity environment. At this time, high cleaning performance can be maintained even when polymerized toner having high adhesion to the transfer / conveying belt 21 is used, and sufficient cleaning performance is exhibited even in a setting of driving at a high process speed of 400 mm / sec. It becomes possible.
In addition, in that case, as a surface material for forming the surface layer of the transfer conveyance belt 21, it is more preferable to use a urethane resin and a resin in which PTFE particles are dispersed in a resin mainly composed of urethane. The surface roughness (Rz) of the transfer / conveying belt 21 is preferably set to 2.5 μm or less.

  Examples of utilization of the present invention include application to copying machines, printers, facsimiles, and multifunctional machines using electrophotography.

1 is a schematic configuration diagram of an image forming apparatus of the present invention. It is sectional drawing which shows the structure of a transfer unit. It is a perspective view which shows the structure of a transfer unit. FIG. 3 is a perspective view illustrating a configuration of a transfer unit in a state where a transfer conveyance unit is removed. FIG. 6 is a diagram illustrating a state where a transfer conveyance unit is separated from a photosensitive drum. FIG. 6 is a diagram illustrating a state where a transfer conveyance unit is in contact with a photosensitive drum. FIG. 6 is a cross-sectional configuration diagram illustrating a state in which a cleaning blade is in contact with a transfer conveyance belt. It is the figure which showed the result of having evaluated the presence or absence of generation | occurrence | production of defective cleaning and blade turning by changing the blade contact angle. It is the figure which showed the result of having evaluated the presence or absence of generation | occurrence | production of defective cleaning and blade turning by changing the blade contact pressure. FIG. 5 is a diagram showing the relationship between the surface material of a transfer / conveyance belt and the occurrence of cleaning failure and blade turning. FIG. 6 is a diagram showing the relationship between the surface roughness of the transfer / conveyance belt, the cleaning failure, and the occurrence of blade turning.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Photosensitive drum, 11 ... Charger, 12 ... Laser exposure device, 13 ... Developing device, 15 ... Transfer part, 17 ... Drum cleaner, 20 ... Transfer unit, 20A ... Transfer conveyance part, 20B ... Retract mechanism part, 20C DESCRIPTION OF SYMBOLS ... Cleaning part, 20D ... Inlet chute part, 21 ... Transfer conveyance belt, 22 ... Drive roll, 23 ... Idle roll, 30 ... Control part, 31 ... Contact / separation plate, 32 ... Link shaft, 33 ... Swing arm, 34 ... DC solenoid, 41 ... cleaning brush, 42 ... flicker bar, 43 ... cleaning blade, 44 ... cleaning box, 45 ... collection coil, 46 ... blade holder, 48 ... side seal, 49 ... seal holder, 54 ... resist roll, 55 ... Inlet chute, 60 ... Fixer

Claims (11)

A toner image carrier for carrying a toner image;
A transfer conveyance belt that transfers the toner image carried by the toner image carrier to a transfer material and conveys the transfer material;
A cleaning member that counter-contacts the transfer conveyance belt and scrapes off adhering matter adhering to the surface of the transfer conveyance belt;
The cleaning member has a contact angle with the transfer conveyance belt of 21 ° or more and 26 ° or less, and a contact pressure with respect to the transfer conveyance belt of 1.5 g / mm or more and 4.0 g. An image forming apparatus characterized in that it is set to / mm or less.   2. The image forming apparatus according to claim 1, wherein the transfer / conveying belt has a base material formed of a rubber layer.   The image forming apparatus according to claim 1, wherein the transfer conveyance belt has a surface roughness (Rz) of 2.5 μm or less.   2. The image forming apparatus according to claim 1, wherein the transfer / conveying belt is formed with a surface layer made of urethane resin or urethane resin in which polytetrafluoroethylene is dispersed.   The transfer conveyance belt is configured to be stretched around at least a pair of rolls, and the cleaning member contacts the transfer conveyance belt in a region where the transfer conveyance belt is stretched around the roll. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the cleaning member is made of urethane rubber. A toner image carrier for carrying a toner image;
A transfer conveyance belt stretched around at least a pair of rolls, transferring a toner image carried by the toner image carrier to a transfer material, and conveying the transfer material; and
A cleaning blade that cleans the deposit by contacting the transfer conveyor belt with an edge surface;
The cleaning blade has a contact angle of 21 ° or more and 26 ° or less with the transfer / conveying belt in a region where the transfer / conveying belt is stretched around the roll. An image forming apparatus, wherein the contact pressure is 1.5 g / mm or more and 4.0 g / mm or less, and is in counter contact with the transfer conveyance belt.   The image forming apparatus according to claim 7, further comprising a cleaning brush for cleaning the rotating blades while adhering to the surface of the transfer conveyance belt while rotating on the upstream side of the cleaning blade in the conveyance direction of the transfer conveyance belt. apparatus.   The image forming apparatus according to claim 7, wherein the cleaning blade contacts the transfer conveyance belt from below in a vertical direction.   8. The image forming apparatus according to claim 7, wherein the toner image carrier is formed by toner produced by a polymerization method.   The image forming apparatus according to claim 7, wherein the transfer conveyance belt conveys the transfer material at a conveyance speed of 350 mm / sec or more.

Images