JP2007114502A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic image forming apparatus designed so as to prevent transfer failure on rugged paper and so on. <P>SOLUTION: In a transfer section which transfers magnetic toner to a recording material, the magnetic toner is transferred by being minutely vibrated by the vibration of a magnetic field in a transfer electric field. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having a transfer support device in an electrophotographic image forming apparatus (copier, facsimile, printer, etc.). More particularly, the present invention relates to a method and apparatus for preventing transfer failure of a magnetic toner image in electrophotographic processing.

  In recent years, there is an increasing need for “media-compatible” output of various recording materials in image forming apparatuses such as copying machines and printers. Conventional image forming apparatuses are not good at outputting recording materials with large irregularities, but demands for media are increasing, and various image forming apparatuses have been proposed to satisfy these demands.

  In an electrophotographic image forming apparatus, first, the charge holding surface of a photoconductor (photosensitive drum, photosensitive belt) as an image carrier is charged by a charging unit, and then an image pattern is exposed by an exposure unit. The body surface is selectively discharged according to the exposure, and an electrostatic latent image is formed. The electrostatic latent image is developed by the developing means by contacting with electrostatically attractable fine powder called toner, and the toner is held on the image area by the electrostatic charge on the surface of the photoreceptor. As the toner, a magnetic toner or a non-magnetic toner is used depending on the developing unit configuration.

  Thereafter, the toner image on the surface of the photosensitive member is transferred to a recording material (for example, a copy sheet, an OHP sheet, etc.) by a transfer unit, subsequently fixed to the recording material by a fixing unit, and permanently recorded on the recording material. An intermediate transfer method is also used in which the toner image on the surface of the photosensitive member is once transferred to an intermediate transfer member, and the toner image on the intermediate transfer member is transferred to a recording material.

  The transfer residual toner on the surface of the photoreceptor after the transfer process is cleaned by a cleaning unit such as a cleaning blade or a cleaning brush, and image formation is performed again by the latent image forming unit.

  Transfer of the toner image from the surface of the photosensitive member to the recording material or transfer of the toner image from the intermediate transfer member to the recording material is generally performed by the action of static electricity. The developed toner image is held on the surface of the photoreceptor by static electricity and mechanical force. The recording material is conveyed to the transfer site, directly contacts the photosensitive member or the intermediate transfer member, charges are applied to the back side of the recording material by the transfer means, and the toner image is sucked to the recording material. As the transfer means, an electrostatic transfer corona device, a transfer roller, a transfer belt, a transfer blade, or the like is used depending on the image forming apparatus.

  However, in the above-described conventional image forming apparatus, when the toner image is transferred onto the recording material by the transfer unit, there is a case where a problem of transfer failure that the toner image is missing may occur.

  This transfer failure mainly includes a transfer failure caused by an air gap when the recording material is uneven paper and a transfer failure caused by pressure on the toner when a transfer roller or the like is used as a transfer unit.

<Air gap-induced transfer failure>
The boundary between the photosensitive member surface or intermediate transfer member surface and the recording material surface is not always in an optimum state. When a recording material that has already been subjected to a fixing process by heating and pressing by a fixing means, or a non-flat recording material such as an uneven paper (for example, embossed paper) is used, the photosensitive member surface or intermediate transfer member surface and the recording material surface May not contact uniformly, and contact may be incomplete. That is, an air gap exists at a location where contact is incomplete. Since this air gap weakens the strength of the transfer electric field to the toner, the toner tends not to transfer beyond these air gaps, and this air gap causes a transfer defect that causes the toner image on the recording material to be lost. To do.

  In response to the problem of transfer defects due to air gaps, JP-A-4-234077 and Japanese Patent No. 3043467 provide vibration energy (ultrasonic vibration) by vibration energy generating means from the back of the photosensitive belt at the transfer portion, It has been proposed to assist the transfer of the toner image beyond the air gap by mechanically releasing the toner from the surface of the photoreceptor belt by this vibration.

  Japanese Patent Laid-Open No. 4-234077 and the like are configured to apply mechanical vibration energy from a back surface of a flexible member (photoreceptor belt) having a charge holding surface at a transfer portion. The merit of this configuration is that it can be applied to both magnetic toner and non-magnetic toner. However, the disadvantage of this configuration is that when applied to a photosensitive drum, the entire photosensitive drum vibrates, so that not only the transfer site, but also other image forming processing sites such as a charging site, an exposure site, a development site, The problem is that a mechanical vibration also affects the cleaning site.

  Problems caused by the vibration of the entire photosensitive drum are, for example, problems such as obstructing uniform charging on the surface of the photosensitive drum and wear of the charging roller when contact charging such as a charging roller is used. Since a sharp electrostatic latent image cannot be formed at the exposed portion, the characters are crushed and the resolution is lowered. At the development site, there are problems such as image deterioration due to scattering of the toner image on the photosensitive drum during development, toner scattering into the image forming apparatus main body, and contact developing roller wear when a contact developing roller is used. At the cleaning site, there are problems such as toner slipping out of the cleaning member and wear of the cleaning blade. Therefore, JP-A-4-234077 has a problem that it can be used only for a photosensitive belt.

  Further, the transfer to the recording material is performed by an electrostatic force approximated by the product of qE. Here, q is the charge of the toner particles, and E is the transfer electric field strength. The qE force in the direction in which the toner is transferred must be large enough to overcome the electrostatic force and mechanical adhesion force that hold the toner on the surface of the photoreceptor. The upper limit of the transfer electric field strength is determined by the Paschen discharge breakdown electric field and the charging performance. Normally, the charge polarity is negative, for example, the surface of the photoconductor and the toner have the same polarity, and the transfer voltage is positive, for example, the polarity opposite to that of the toner. The transfer current penetrates the recording material, charges the surface of the photoconductor with a positive polarity, and cannot be charged with a negative polarity by the charging means, and charging unevenness occurs on the photoconductor as a transfer memory. This transfer memory on the photoconductor causes problems such as developing toner in non-image areas and density unevenness in image areas. Therefore, the transfer electric field strength must be less than or equal to the transfer memory generation electric field. Therefore, in order to perform transfer in the air gap, it is difficult to increase the transfer electric field strength due to the generation of the transfer memory, and it is difficult to increase the transfer memory generation electric field because of the configuration of the image forming apparatus. In this case, it is necessary to perform toner transfer with a weaker transfer electric field.

<Transfer failure due to pressure on toner>
When the toner particle layer existing between the photoconductor and the recording material is subjected to pressure by the transfer belt, the transfer roller, or the like during the transfer process for transferring the toner image from the photoconductor to the recording material, FIG. As shown in FIG. 6, a transfer defect that causes an image defect such as a hole (hollow character, hollow character) at the center of the transferred line image or character image occurs.

  This is because the line image formed on the photoconductor is in contact with the transfer roller (transfer site), and when the photoconductor and the recording material come close to each other, pressure acts on the toner particle layer. At this time, since the toner particles can move in the lateral direction at the end of the line image, toner particles do not easily aggregate in this end region. On the other hand, since there are toner particles around the toner particles in the central portion of the line image, it is difficult to move them away. In this case, it is impossible to escape from the pressure action from the transfer roller, and aggregation of toner particles occurs. As the toner particles are deformed, the contact area between the toner particles, the photoreceptor and the recording material increases. That is, the adhesion force between the surrounding toner particles, the photoreceptor and the recording material is increased. This adhesion force is an intermolecular force such as van der Waals force. As a result, the adhesion between the photosensitive drum and the recording material is increased at the center of the line image. In reality, there is no problem with the upstream process such as development, and there is no optimal photoconductor or recording material. Therefore, the adhesion between the toner particles and the photoconductor is higher than the adhesion between the toner particles and the recording material. Wearing power is greater.

  As the toner particle layer begins to pass through the transfer nip, the pressure on the toner particle layer is released. At that time, in the case of small deformation in which the deformation amount of the toner particles is an elastic region, the deformation disappears as the pressure is released, and at the same time, the increased adhesion force returns to the size before the pressure is applied. However, since the toner particles in the center of the line image are so large that the toner particle deformation amount reaches the plastic deformation region, the deformation amount is preserved to some extent even when the pressure is released. This is called elastic hysteresis (elastic hysteresis phenomenon). As a result, the state where the adhesion force is increased is maintained. Moreover, the greatly increased adhesion between the toner particles and the photoconductor is that the adhesion between the toner particles (= cohesive force), the adhesion between the toner particles and the recording material, and the transfer of the toner particles from the photoconductor to the recording material. Greater than force (electrostatic force). As a result, the toner particles in the center of the line image become untransferable due to the increased adhesion with the photoconductor, and finally is observed in the toner image on the recording material due to the phenomenon of void as shown in FIG. 9B. The FIG. 9A shows a normal image in which no void has occurred.

  In response to the problem of transfer failure due to pressure on the toner, Japanese Patent Application Laid-Open No. 2001-117381 proposes to transfer a toner image from a photosensitive member to a recording material using acoustic radiation force due to standing waves of ultrasonic waves. is doing. Japanese Patent Application Laid-Open No. 2001-117381 is a configuration in which the interval between the photosensitive member and the recording material is set to an integral multiple of the half wavelength of the generated ultrasonic wave, and is different from the configuration in which the transfer process is performed by electrical action.

  Further, with respect to prevention of hollowing out, Japanese Patent Laid-Open No. 07-044030 has almost the same configuration as the above-mentioned Japanese Patent Laid-Open No. 4-234077, and the photosensitive member or the recording material is vibrated minutely at the transfer portion. It has been proposed to reduce the adhesion between the photoconductor and the toner and prevent voids. This Japanese Patent Application Laid-Open No. 07-044030 has a problem that it can be used only for a photosensitive belt or an intermediate transfer belt for the same reason as the above Japanese Patent Application Laid-Open No. 4-234077. There is also a problem that the toner is scattered to the non-image portion sometimes and the image definition is lowered.

As another conventional example, Patent Document 5 can be cited.
JP-A-4-234077 Japanese Patent No. 3043467 Japanese Patent Laid-Open No. 2001-117381 Japanese Patent Application Laid-Open No. 07-044030 Japanese Patent Laid-Open No. 06-059580

  In view of this, the present invention prevents the above-described transfer defect that a toner image is lost during transfer from a photosensitive member or an intermediate transfer member as an image carrier to a recording material, and a recording material or transfer roller having large irregularities. An object of the present invention is to provide an image forming apparatus capable of obtaining a clear transfer image even in the case of the above.

  The above object is achieved by a fixing device or an image forming apparatus according to the present invention described below.

  (1) An image carrier on which a latent image is formed on the surface, a charging means for uniformly charging the image carrier, an exposure means for forming an electrostatic latent image on the image carrier, and formed on the image carrier A developing means for forming a magnetic toner image on the image carrier by developing the formed electrostatic latent image with magnetic toner, and a magnetic toner image formed on the image carrier by applying a transfer voltage. In the image forming apparatus, the magnetic toner image is further transferred to a recording material after being transferred to an intermediate transfer member, and further transferred to a recording material, and a fixing means for fixing the magnetic toner image on the recording material. Has magnetic field vibration generating means at the transfer site for transferring the toner to the recording material, and magnetically vibrates the magnetic toner on the image bearing member or intermediate transfer member by the magnetic field vibration in the transfer electric field, and magnetically adheres to the recording material by the transfer electric field. To transfer the toner The image forming apparatus according to symptoms.

  (2) The image forming apparatus according to (1), wherein the magnetic field vibration generating means arranged at the transfer site generates the magnetic field vibration by applying an alternating current to the electromagnet.

  (3) The image forming apparatus according to (2), wherein a rectangular wave alternating current is applied to the electromagnet.

  (4) The image forming apparatus according to (1), wherein the magnetic field vibration generating unit disposed at the transfer site generates the magnetic field vibration by vibrating the magnetic field generating unit with the vibration generating unit.

  (5) The image forming apparatus according to (4), wherein the vibration generating unit is an ultrasonic resonance apparatus.

  (6) The image forming apparatus according to any one of (1) to (5), wherein the magnetic field vibration generating means is disposed inside the image carrier or the intermediate transfer member.

  Japanese Patent Application Laid-Open No. 06-059580 discloses a transfer unit including a magnetic field generation unit, and a magnetic body provided on the back surface of the photoconductor so as to face the transfer unit. Providing high-quality images with no fogging on the non-image area on the recording material and no fouling on the recording material by installing it longer than the distance from the body to the surface of the photoconductor is doing. In Japanese Patent Laid-Open No. 06-059580, untransferred toner adhering to a non-image portion is held on the photosensitive member side by a magnetic force at the time of transfer, so that an image without fogging can be output. It does not mention transfer defects and does not use magnetic field vibration. During non-transfer, the electrostatic force in the direction of the transfer unit is cut off, so that even if toner adheres to the surface of the transfer unit, the toner on the transfer unit is transferred to the photoreceptor side by the magnetic attraction force, and the transfer unit is cleaned. Since it is configured to achieve, no mention is made of toner transfer failure in the image area, and magnetic field vibration is not used. Further, when the transfer unit is not sufficiently cleaned, the transfer unit includes a magnetic field generating unit having a plurality of magnetic poles so that the toner on the transfer unit is moved by the magnetic force to improve the cleaning performance of the transfer unit. is there. This also does not refer to toner transfer failure in the image area, and magnetic field vibration is generated at the transfer site, but the toner is vibrated because it does not consider the toner transfer from the photoconductor to the recording material. However, since the magnetic field is oscillated so as to move the toner, it is presumed that the toner image scatters to the non-image portion and the occurrence of image density unevenness due to transfer unevenness becomes a problem at the time of transfer.

  According to the first aspect of the present invention, the magnetic toner on the image carrier or the intermediate transfer member is vibrated minutely by the magnetic field vibration generating means, whereby the adhesion force (static electricity) between the magnetic toner and the image carrier or the intermediate transfer member. Force and mechanical adhesion force), transfer defects due to air gaps and pressures can be prevented, toner consumption can be reduced by improving transfer efficiency, and transfer action by a low transfer electric field can be realized.

  According to the second aspect of the present invention, the magnetic toner can be minutely vibrated by the magnetic field vibration by the configuration in which the alternating current is applied to the electromagnet as the magnetic field vibration generating means according to the first aspect.

  According to the third aspect of the present invention, as the magnetic field vibration generating means according to the second aspect, the magnetic toner can be finely vibrated more effectively by applying a rectangular wave alternating current to the electromagnet.

  According to the fourth aspect of the present invention, the magnetic toner can be minutely vibrated by the magnetic field vibration by the configuration in which the magnetic field generation unit is vibrated by the vibration generation unit.

  According to the fifth aspect of the present invention, the magnetic toner can be minutely vibrated by the configuration using the ultrasonic resonance device as the vibration generating means according to the fourth aspect.

  According to the sixth aspect of the present invention, the magnetic field vibration generating means is arranged inside the image carrier or the intermediate transfer member, so that the toner adheres to the magnetic field vibration generating means and the adhered toner is re-applied to the recording material. Since there is no transfer, there is no risk of soiling the recording material.

  As described above, according to the present invention, it is possible to prevent air gap-induced transfer failure due to uneven paper and pressure-related transfer failure due to a transfer roller, etc., and further, toner consumption can be reduced by lowering transfer efficiency, and transfer electric field can be reduced. An image forming apparatus capable of preventing electrical history (such as a transfer memory) from being applied to the image carrier can be provided.

  Embodiments of the present invention will be described with reference to FIGS. In addition, in these drawings, the same member is attached | subjected the same code | symbol and the overlapping description is abbreviate | omitted.

  A first embodiment according to the present invention will be described with reference to FIGS. 1 to 3 and FIGS.

  6 to 8 are examples of an image forming apparatus for explaining the first embodiment of the present invention.

  First, an image forming method will be described.

  FIG. 6 is a schematic cross-sectional view showing a schematic configuration of an image forming apparatus using a corona transfer device as transfer means.

  As shown in FIG. 6, a photosensitive drum 101 as an image carrier is a photoconductive layer whose surface is mainly composed of an organic or inorganic photosensitive member, and is provided with a drive mechanism (not shown) provided in the main body of the image forming apparatus. ) To rotate in the clockwise direction of arrow A. The photosensitive drum 101 is uniformly and uniformly charged at a predetermined potential by a corona charging device 102 as a charging unit, and then the image is formed on the outer peripheral surface thereof by exposure light from an exposure device 103 as an exposure unit according to image information. An electrostatic latent image corresponding to the information is formed. This electrostatic latent image is visualized as a magnetic toner image by the developing sleeve 104a carrying the charged magnetic developer (magnetic toner) R of the developing device 104 as the current developing means.

  Here, the recording material P is in contact with the photosensitive drum 101 at a predetermined timing so that the leading end of the recording material P and the image portion leading end visualized by the magnetic toner R on the outer peripheral surface of the photosensitive drum 101 are synchronized. The magnetic toner R image on the photosensitive drum 101 is transferred onto the recording material P by being introduced into a transfer portion T between the corona transfer device 105 and the photosensitive drum 101 as transfer means.

  After the transfer process, the transfer residual toner on the photosensitive drum 101 is removed from the photosensitive drum 101 and collected by the cleaning device 107 by a cleaning blade 107a of a cleaning device 107 as a cleaning unit. After the cleaning process, the photosensitive drum 101 repeats the image forming process (charging → exposure → development → transfer → cleaning) to form an unfixed toner image on the recording material P.

  On the other hand, the recording material P carrying the unfixed toner image is introduced into a fixing device 106 as a fixing unit, and is pressed and heated to permanently fix the toner image on the recording material P.

  This embodiment will be described.

  FIG. 1 is a schematic cross-sectional view showing a schematic configuration of the magnetic field vibration generating means 1 in the image carrier 101.

  FIG. 2 is a schematic perspective view showing a schematic configuration in the longitudinal direction of the magnetic field vibration generating means 1 in the image carrier 101.

  In the present embodiment, the magnetic toner R on the photosensitive drum 101 is minutely vibrated at the transfer site T by the magnetic field vibration generating means 1, and this vibration reduces the adhesive force between the magnetic toner R and the photosensitive drum 101, thereby transferring the transfer process. This prevents the above-mentioned transfer failure.

An electromagnet 1 as magnetic field vibration generating means is a general electromagnet in which a coil 1b as a conductive member for applying a current is arranged on the outer periphery of a core 1a that is a magnetic body such as an iron core. As shown in FIGS. 1 and 2, the electromagnet 1 is installed in the longitudinal direction of the transfer portion T so that the magnetic pole portion 1 c is disposed in the non-contact vicinity of the transfer portion T of the rotating photosensitive drum 101. In addition, the magnetic pole portion 1 c, which is a portion of the core 1 a of the electromagnet 1 that faces the photosensitive drum 101, has an R shape so that it can approach the photosensitive drum 101 without contact.
The electromagnet 1 is configured such that an alternating current is applied to the coil 1b and the magnetic pole portion 1c is switched between the N pole and the S pole. The magnetic toner R on the photosensitive drum 101 at the transfer site T is polarized and magnetized by the magnetic field of the magnetic pole portion 1c, and the remanent magnetization due to the magnetization hysteresis (magnetization history phenomenon) of the magnetic toner R causes the N pole and S pole of the magnetic pole 1c. In response to the switching, the magnetic toner R on the photosensitive drum 101 vibrates slightly.

  Therefore, the adhesion force (electrostatic force and mechanical adhesion force) between the magnetic toner R and the photosensitive drum 101 is reduced by the minute vibration of the magnetic toner R on the photosensitive drum 101 at the transfer portion T, and the photosensitive drum 101 and the recording material are reduced. Even if there is an air gap because P is not in close contact, the magnetic toner R can be transferred to the recording material P by electrostatic force in the transfer process, and transfer defects can be prevented even on uneven paper. That is, the magnetic toner R can be transferred onto the recording material P with a weaker transfer electric field strength than is normally used. Further, since the occurrence of air breakdown (generation of transfer memory) is reduced, it is better that the transfer electric field strength is weak. Even in a region where the contact between the recording material P and the photosensitive drum 101 is optimal, high transfer efficiency can be expected, and there is an advantage that the toner use efficiency is improved (toner consumption is reduced).

  Here, due to the magnetic field generated by the magnetic field vibration generating means 1, the magnetic adhesive force is added to the magnetic toner R and the photosensitive drum 101 in addition to the electrostatic force and the mechanical adhesive force. However, since the magnetic field vibration generating means 1 not only attracts the magnetic toner but also switches the polarity of the magnetic pole portion 1c to repeat the attracting and repelling to the magnetic toner, the magnetic adhesion force between the magnetic toner R and the photosensitive drum 101 is increased. Is an extremely weak force that can be ignored as compared with the electrostatic force and the mechanical adhesive force, which are the adhesive force between the magnetic toner R and the photosensitive drum 101.

  The alternating current may be a general sine wave having the waveform shown in FIG. 3A. However, when the rectangular current shown in FIG. 3B is used, the rise (speed) of magnetic pole switching of the magnetic pole portion 1c is fast. Therefore, the magnetic force received from the magnetic pole portion 1c by the residual magnetization of the magnetic toner R is increased, and the minute vibration of the magnetic toner R can be effectively increased. That is, since the magnetic force of the electromagnet 1 can be reduced (the alternating current value can be reduced), there is an advantage that the magnetic toner R can be vibrated more efficiently.

  Further, the frequency of the alternating current is preferably set so as not to be too low to give a plurality of magnetic field vibrations at the transfer site T and not to be too high in order to efficiently use the residual magnetization of the magnetic toner R. The alternating current frequency is preferably in the range of 100 Hz to 10 KHz, although it depends on the image forming speed, the recording material conveyance speed, and the width of the transfer portion T.

  In addition, the minute vibration of the magnetic toner R is transferred onto the recording material P while being finely oscillated, so that the peak portion (maximum strength portion) of the transfer electric field intensity at the transfer portion T or the recording material P including the peak portion is obtained. If performed on the upstream side of the conveyance, transfer defects in the air gap can be prevented with a weaker transfer electric field.

  FIG. 7 is a schematic cross-sectional view showing a schematic configuration of an image forming apparatus using a transfer roller as transfer means.

  6 uses a corona discharge device that is not in contact with the photosensitive drum 101 and the recording material P as charging means and transfer means. FIG. 7 is a charging means that is in contact with the photosensitive drum 101 and recording material P. And a transfer roller 105a as a transfer means. Since the charging roller 102a and the transfer roller 105a are contact systems, the charging process and the transfer process can be performed with a very small applied voltage as compared with the corona discharge device, so that the generation of ozone is very small. Therefore, the ozone odor of the image forming apparatus is very small, so that it is not a concern for a desktop arrangement close to a narrow place or a user. In addition, since a filter such as an ozone filter that does not discharge ozone to the outside of the main body is not required in the image forming apparatus main body, there is an advantage that the cost of the image forming apparatus main body can be reduced.

  However, according to the transfer process using the contact transfer type transfer roller, there is a problem of missing characters as described above.

  To solve this character missing problem, the magnetic field vibration generating means 1 is arranged in the photosensitive drum 101 of the present embodiment as shown in FIGS. 1 and 2, and the magnetic force due to the pressure action of the transfer roller 105a is used. As the adhesion force between the toner R and the photosensitive member 101 increases, the minute vibration of the magnetic toner R can reduce the adhesion force, so that it is possible to prevent text from being lost. This is because the micro-vibration reduces the cohesive force between the toners of the magnetic toner R due to pressure action and the adhesion force, and the magnetic toner R can be transferred to the recording material by electrostatic force in the transfer process. Also, transfer failure can be prevented.

  The contact transfer method using the transfer roller 105a shown in FIG. 7 uses the corona discharge device 105 shown in FIG. 6 due to the pressure action of the recording material P on the photosensitive drum 101a by the transfer roller 105a when transferring uneven paper. Compared with the non-contact transfer method, the air gap amount is small. Therefore, the transfer failure due to the air gap has the advantage of being reduced, but the transfer failure due to the air gap does not become zero. Therefore, by using this embodiment, even in the contact transfer system, the effect of preventing transfer defects due to the air gap can be obtained as in the case described with reference to FIG.

  In the image forming apparatus using the contact transfer method, it is possible to prevent a transfer defect due to pressure to the toner and a transfer defect due to an air gap.

  FIG. 8 is a schematic cross-sectional view showing a schematic configuration of an image forming apparatus using an intermediate transfer member.

  6 and 7 show a configuration in which the magnetic toner R is directly transferred from the photosensitive drum 101 to the recording material P. FIG. On the other hand, FIG. 8 shows that the magnetic toner R image on the photosensitive drum 101 is primarily transferred to the intermediate transfer belt 201 as an intermediate transfer member by the primary transfer roller 205a at the primary transfer portion T1, and further secondary. The magnetic toner R image on the intermediate transfer belt 201 is secondarily transferred onto the recording material P by the secondary transfer roller 205b at the transfer site T2.

  In the image forming apparatus using the intermediate transfer member 201 in FIG. 8, when a small size paper is passed as the recording material P in the transfer process of the image forming apparatus in FIGS. A large amount of transfer current flows, creating a transfer memory in the photosensitive layer, and the charging drum cannot uniformly charge the photosensitive drum 101, and in the next large size paper, toner adheres to image density unevenness and non-image areas. This has the advantage that no problems such as occurrence occur. Further, by providing an elastic layer on the surface layer of the intermediate transfer body 201, the pressure concentration at the transfer sites T1 and T2 at the time of primary transfer and secondary transfer in the contact transfer method can be alleviated. This has the advantage of reducing omissions. Further, at the time of secondary transfer, the elastic layer of the intermediate transfer member 201 is elastically deformed so as to follow the concave portion of the concavo-convex paper, so that the air gap is reduced and transfer defects due to the air gap can be reduced. .

  However, even in the image forming apparatus having the configuration shown in FIG. 8, if the surface roughness of the surface layer of the photosensitive drum 101 increases due to durability, the hollowing out of characters deteriorates. The transfer failure was incomplete, such as the occurrence of transfer failure.

  Therefore, even in the image forming apparatus using the intermediate transfer member 201 having the configuration shown in FIG. 8, the configuration in which the magnetic field vibration generating means 1 of the present embodiment is disposed at the secondary transfer site T2 in the intermediate transfer member 201 is 2 Since the adhesive force between the intermediate transfer member 201 and the magnetic toner R at the time of the next transfer can be reduced, the character transfer or uneven paper transfer at the time of the second transfer can be performed regardless of the presence or absence of the elastic layer on the surface of the intermediate transfer member 201. Defects can be prevented.

  In FIG. 8, the magnetic field vibration generating means 1 is arranged at the secondary transfer site T2 in the intermediate transfer body 201, and the magnetic field vibration generating means 1 is also arranged at the primary transfer site T1 in the photosensitive drum 101. Transfer defects in the primary transfer process can also be prevented. Furthermore, since high primary transfer efficiency and secondary transfer efficiency can be realized, there are advantages such as improvement in toner use efficiency (reduction of toner consumption) and reduction in transfer voltage.

  As described above, in this embodiment, the magnetic field vibration generating means is disposed at the transfer site, and the magnetic toner on the image carrier or intermediate transfer member is minutely vibrated, whereby the image carrier or intermediate transfer member and the magnetic toner. Can be reduced, transfer failure can be prevented, and transfer with high toner transfer efficiency or low transfer voltage can be realized.

  In addition, the conventional transfer defect countermeasure that vibrates the toner by mechanical vibration in the transfer portion was applicable only to the belt system (photosensitive belt, intermediate transfer belt, etc.), but this embodiment is not mechanical vibration, Since magnetic toner is vibrated by magnetic vibration, it can be applied not only to the belt system but also to the drum system (photosensitive drum or intermediate transfer drum). With the advantage of being.

  However, the conventional transfer defect countermeasure that vibrates the toner by mechanical vibration at the transfer portion was applicable to magnetic toner and non-magnetic toner. However, since this embodiment uses magnetic vibration, only the magnetic toner is used. It has the disadvantage of being applicable.

  In this embodiment, the magnetic field vibration generating means is arranged inside the image carrier or the intermediate transfer body. However, the magnetic field vibration generating means may be arranged on the transfer means side (the back side of the recording material P). The effect is equivalent. However, the configuration in which the magnetic field vibration generating means is arranged on the transfer means side is such that the magnetic toner (fogging toner) or the recording material adhered to the non-image portion in the space between the recording materials P or in the non-sheet passing portion at the time of small size passing. When P jam occurs, magnetic toner adheres to the magnetic field vibration generating means, and the attached toner contaminates the recording material P. Therefore, it is necessary to separately arrange a toner cleaning member (not shown) in the magnetic field vibration generating means. There's a problem. Therefore, it is more preferable that the magnetic field vibration generating means is disposed inside the image carrier or the intermediate transfer member.

  A second embodiment according to the present invention will be described with reference to FIGS. 4, 5, and 6 to 8.

  In the first embodiment, the magnetic toner is minutely vibrated by generating the magnetic field vibration by the magnetic field vibration generating means by applying the alternating current of the electromagnet. However, in this embodiment, the magnetic field generating means is used as the magnetic field vibration generating means. The magnetic toner is minutely vibrated by generating a magnetic field vibration by vibrating the toner by a mechanical vibration generating means.

  FIG. 4 is a schematic cross-sectional view showing a schematic configuration of the magnetic field generation means 2 and the vibration generation means 3 as magnetic field vibration generation means in the image carrier 101.

  FIG. 5 is a schematic perspective view showing a schematic configuration in the longitudinal direction of the magnetic field generating means 2 and the vibration generating means 3 as magnetic field vibration generating means in the image carrier 101.

  FIG. 6 is a schematic cross-sectional view showing a schematic configuration of an image forming apparatus using a corona transfer device as transfer means.

  In this embodiment, the magnetic toner R on the photosensitive drum 101 at the transfer portion T is generated by vibrating the magnetic field generating means 2 by the vibration generating means 3 at the transfer portion T of the image forming apparatus of FIG. Is vibrated, and this vibration reduces the adhesive force between the magnetic toner R and the photosensitive drum 101 and prevents the above-mentioned transfer failure in the transfer process. Therefore, the magnetic field generation means 2 and the vibration generation means 3 are combined to replace the magnetic field vibration generation means 1 of the first embodiment.

  The magnet 2 as the magnetic field generating means is a general magnet that is a magnetic body that is a permanent magnet by magnetizing a metal body obtained by sintering ferrite or the like, or a resin body (plastic magnet) in which a magnetic body is dispersed in a resin. . As shown in FIGS. 4 and 5, the magnet 2 is installed in the longitudinal direction of the transfer portion T so that the magnetic pole portion 2 c is disposed in the non-contact vicinity of the transfer portion T of the rotating photosensitive drum 101. In addition, the magnetic pole portion 2 c, which is a portion of the magnet 2 that faces the photosensitive drum 101, has an R shape so that it can approach the photosensitive drum 101 without contact.

  The ultrasonic resonator 3 as the vibration generating means is a relatively high frequency acoustic resonator driven by an AC power source (not shown) that operates at a frequency of 20 KHz to 200 KHz.

  The ultrasonic resonator 3 is connected to the magnet 2, and the vibration of the ultrasonic resonator 3 is transmitted to the magnet 2 so that the magnet 2 vibrates.

  The magnetic toner R on the photosensitive drum 101 at the transfer site T is polarized and magnetized by the magnetic field of the magnetic pole part 2c of the magnet 2, and the magnetic toner R is captured by the magnetic field. Then, the magnetic field on the photosensitive drum 101 vibrates minutely due to the vibration of the magnetic field by the vibration of the ultrasonic resonator 3.

  Therefore, the adhesion force (electrostatic force and mechanical adhesion force) between the magnetic toner R and the photosensitive drum 101 is reduced by the minute vibration of the magnetic toner R on the photosensitive drum 101 at the transfer portion T, and the photosensitive drum 101 and the recording material are reduced. Even if there is an air gap because P is not in close contact, the magnetic toner R can be transferred to the recording material P by electrostatic force in the transfer process, and transfer defects can be prevented even on uneven paper. That is, the magnetic toner R can be transferred onto the recording material P with a weaker transfer electric field strength than is normally used. Also, since the occurrence of air breakdown (generation of transfer memory) is reduced, the transfer field strength should be weak. Even in a region where the contact between the recording material P and the photosensitive drum 101 is optimal, high transfer efficiency can be expected, and there is an advantage that the toner use efficiency is improved (toner consumption is reduced).

  Here, due to the magnetic field generated by the magnet 2, the magnetic adhesive force is added to the magnetic toner R and the photosensitive drum 101 in addition to the electrostatic force and the mechanical adhesive force. However, the magnetic force generated by the magnet 2 may be a weak force that does not move the magnetic toner but captures the magnetic toner R and vibrates it minutely. Therefore, it is a very weak force that can be ignored compared to the electrostatic force that is the adhesive force between the magnetic toner R and the photosensitive drum 101 and the mechanical adhesive force.

  In addition, the minute vibration of the magnetic toner R is transferred onto the recording material P while being finely oscillated, so that the peak portion (maximum strength portion) of the transfer electric field intensity at the transfer portion T or the recording material P including the peak portion is obtained. If performed on the upstream side of the conveyance, transfer defects in the air gap can be prevented with a weaker transfer electric field.

  FIG. 7 is a schematic cross-sectional view showing a schematic configuration of an image forming apparatus using a transfer roller as transfer means.

  As in the first embodiment, the problem of missing characters in the case of using the transfer roller 105a in FIG. 7 is also used as magnetic field vibration generating means in the photosensitive drum 101 of the present embodiment as shown in FIGS. By using the configuration in which the magnetic field generating means 2 and the vibration generating means 3 are arranged, the minute vibration of the magnetic toner R is caused by the increase in the adhesion force between the magnetic toner R and the photosensitive member 101 due to the pressure action of the transfer roller 105a. Since the adhesive force can be reduced, it is possible to prevent the character from being lost. This is because the micro-vibration reduces the cohesive force between the toners of the magnetic toner R due to pressure action and the adhesion force, and the magnetic toner R can be transferred to the recording material by electrostatic force in the transfer process. Also, transfer failure can be prevented.

  The contact transfer method using the transfer roller 105a shown in FIG. 7 uses the corona discharge device 105 shown in FIG. 6 due to the pressure action of the recording material P on the photosensitive drum 101a by the transfer roller 105a when transferring uneven paper. Compared with the non-contact transfer method, the air gap amount is small. Therefore, the transfer failure due to the air gap has the advantage of being reduced, but the transfer failure due to the air gap does not become zero. Therefore, by using this embodiment, even in the contact transfer system, the effect of preventing transfer defects due to the air gap can be obtained in the same manner as described with reference to FIG.

  In the image forming apparatus using the contact transfer method, it is possible to prevent a transfer defect due to pressure to the toner and a transfer defect due to an air gap.

  FIG. 8 is a schematic cross-sectional view showing a schematic configuration of an image forming apparatus using an intermediate transfer member.

  Similarly to the first embodiment, even when the intermediate transfer member shown in FIG. 8 is used, the magnetic field generating means 2 and the vibration generating means 3 are arranged as the magnetic field vibration generating means at the secondary transfer site T2 in the intermediate transfer member 201. By using the configuration, it is possible to reduce the adhesion between the intermediate transfer member 201 and the magnetic toner R at the time of the secondary transfer, and therefore, it is possible to prevent the lack of characters in the secondary transfer and the transfer failure of the uneven paper. it can.

  In FIG. 8, the magnetic field generating means 2 and the vibration generating means 3 are arranged at the secondary transfer site T2 in the intermediate transfer body 201, and the magnetic field generating means 2 and the vibration generating device 3 are arranged in the primary transfer site in the photosensitive drum 101. By disposing also at T1, transfer defects in the primary transfer process can also be prevented. Furthermore, since high primary transfer efficiency and secondary transfer efficiency can be realized, there are advantages such as improvement in toner use efficiency (reduction of toner consumption) and reduction in transfer voltage.

  Here, as shown in FIG. 5, the vibration generating means 3 vibrates the magnetic field generating means 2 in the direction of the arrow X which is the same direction as the recording material P conveying direction of the transfer site T, or the direction perpendicular to the recording material conveying direction. The effect is the same in either the arrow Y direction (longitudinal direction of the transcription site T). Therefore, as long as it is an in-plane direction including the arrow X direction and the arrow Y direction (for example, a 45 degree direction between the arrow X direction and the arrow Y direction), the effect is the same regardless of which direction is vibrated. However, in the case of the image forming apparatus using the transfer roller 105a as the transfer unit in FIG. 7, the transfer portion T, which is the transfer nip portion between the photosensitive drum 101 and the transfer roller 105a, has a narrow width. Since the possibility of vibrating the magnetic toner R outside the portion T is reduced, it is more preferable.

  However, when the direction of vibration of the magnetic field generating means 2 by the vibration generating means 3 is the arrow Z direction (the thickness direction of the recording material P) which is the vertical direction with respect to the recording material P conveyance direction, the magnetic field vibration with respect to the magnetic toner R Since the magnetic toner R does not vibrate slightly because the magnetic force R is only changed by the generating means 2, it is preferable to set the vibration direction other than the arrow Z direction.

  As described above, in this embodiment, the magnetic field generating means and the vibration generating means for vibrating the magnetic field generating means are arranged as the magnetic field vibration generating means at the transfer portion, and the magnetic toner on the image carrier or the intermediate transfer member. By slightly vibrating the toner, it is possible to reduce the adhesive force between the image carrier or the intermediate transfer member and the magnetic toner, prevent transfer failure, and realize transfer with high toner transfer efficiency or low transfer voltage.

  In addition, the conventional transfer defect countermeasure that vibrates the toner by mechanical vibration in the transfer portion can be applied only to the belt system (photosensitive belt, intermediate transfer belt, etc.), but this embodiment is not mechanical vibration, Since magnetic toner is vibrated by magnetic vibration, it can be applied not only to the belt system but also to the drum system (photosensitive drum, intermediate transfer drum). With the advantage of being.

  However, the conventional transfer defect countermeasure that vibrates the toner by mechanical vibration at the transfer site can be applied to the magnetic toner and the non-magnetic toner. However, since this embodiment uses magnetic vibration, only the magnetic toner is used. It has the disadvantage of being applicable.

  In this embodiment, the magnetic field vibration generating means (= magnetic field generating means + vibration generating means) is arranged inside the image carrier or the intermediate transfer body. The effect is the same even in the configuration arranged on the back side of the material P). However, the configuration in which the magnetic field vibration generating means is arranged on the transfer means side is such that the magnetic toner (fogging toner) or the recording material adhered to the non-image portion in the space between the recording materials P or in the non-sheet passing portion at the time of small size passing. When P jam occurs, the magnetic toner adheres to the magnetic field vibration generating means, and the adhering toner contaminates the recording material P. Therefore, it is necessary to separately arrange a toner cleaning member (not shown) in the magnetic field vibration generating means. There's a problem. Accordingly, also in this embodiment, it is more preferable that the magnetic field vibration generating means is disposed inside the image carrier.

  Although the embodiments of the present invention have been described above, the numerical values in the first and second embodiments of the present invention are examples for simplifying the description of the embodiments, and the numerical values are the image forming apparatus. It can be arbitrarily determined according to the configuration and settings of

  The present invention is not limited to the image forming apparatus described in the embodiments, and can be applied to other image forming apparatuses using magnetic toner, such as any combination of the embodiments.

It is typical sectional drawing which shows an example of the magnetic field vibration generation means which concerns on Example 1 of this invention. It is a typical perspective view which shows an example of the magnetic field vibration generation means which concerns on Example 1 of this invention. It is a schematic diagram which shows the alternating current waveform applied to the magnetic field vibration generation means which concerns on Example 1 of this invention. It is typical sectional drawing which shows another example of the magnetic field vibration generation means which concerns on Example 2 of this invention. It is a typical perspective view which shows another example of the magnetic field vibration generation means which concerns on Example 2 of this invention. It is typical sectional drawing which shows an example of the image forming apparatus using the corona discharge transfer apparatus which concerns on Example 1 and Example 2 of this invention. FIG. 3 is a schematic cross-sectional view illustrating an example of an image forming apparatus using a transfer roller according to Embodiment 1 and Embodiment 2 of the present invention. FIG. 3 is a schematic cross-sectional view illustrating an example of an image forming apparatus using an intermediate transfer member according to Example 1 and Example 2 of the present invention. It is a schematic diagram which shows an example of a character missing image.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic field vibration generating means 2 Magnetic field generating means 3 Vibration generating means 101 Image carrier (photosensitive drum)
105 Corona discharge transfer apparatus 105a Transfer roller 201 Intermediate transfer member 205a Primary transfer roller 205b Secondary transfer roller P Recording material R Toner T Transfer site T1 Primary transfer site T2 Secondary transfer site

Claims (6)

An image carrier on which a latent image is formed, a charging unit that uniformly charges the image carrier, an exposure unit that forms an electrostatic latent image on the image carrier, and a static image formed on the image carrier. Developing means for forming the magnetic toner image on the image carrier by developing the electrostatic latent image with magnetic toner, and transferring the magnetic toner image formed on the image carrier to the recording material by applying a transfer voltage; Alternatively, in an image forming apparatus having a transfer unit that once transfers the image onto an intermediate transfer member, and further transfers to a recording material, and a fixing unit that fixes the magnetic toner image on the recording material.
The transfer portion for transferring the magnetic toner image to the recording material has magnetic field vibration generating means. The magnetic toner on the image carrier or the intermediate transfer member is minutely vibrated by the magnetic field vibration in the transfer electric field and recorded by the transfer electric field. An image forming apparatus, wherein a magnetic toner is transferred onto a material.   The image forming apparatus according to claim 1, wherein the magnetic field vibration generating means disposed at the transfer site generates the magnetic field vibration by applying an alternating current to the electromagnet.   The image forming apparatus according to claim 2, wherein an alternating current of a rectangular wave is applied to the electromagnet.   2. The image forming apparatus according to claim 1, wherein the magnetic field vibration generating means arranged at the transfer site generates the magnetic field vibration by vibrating the magnetic field generating means with the vibration generating means.   The image forming apparatus according to claim 4, wherein the vibration generating unit is an ultrasonic resonance apparatus.   6. The image forming apparatus according to claim 1, wherein the magnetic field vibration generating means is disposed inside the image carrier or the intermediate transfer member.

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