JP4975425B2 - Charging method, charging device and image forming apparatus - Google Patents

Description

  The present invention relates to a charging device and an image forming apparatus, and more particularly to a charging device and an image forming apparatus for charging an electrostatic latent image carrier when an image is formed in an electrophotographic copying machine, a printer, or the like. Is.

  In an image forming apparatus such as an electrophotographic copying machine or printer, the surface of a charged body is uniformly charged by various methods prior to forming an electrostatic latent image on the charged body such as a photoconductor.

  As a conventional charging method, for example, there is a charging method by corona discharge. In this method, the surface of the photoreceptor is charged by discharging from a very thin wire. However, in this method, a high voltage power source of about 4 to 10 kV is required to charge the surface of the photoreceptor. Furthermore, since a large amount of ozone is generated by the discharge from the wire, there is a problem that not only the human body is adversely affected but also the deterioration of the photoreceptor is accelerated. In order to solve such a problem, for example, Patent Document 1 and Patent Document 2 disclose corona charging devices improved so as to reduce the amount of ozone generated.

  As another charging method, a method of charging the surface of a photoreceptor by a contact charging method has been put into practical use in recent years. In this method, the surface of the photoconductor is charged by bringing a conductive member such as a conductive roller, brush, elastic blade, or carbon nanotube into contact with the surface of the photoconductor, thereby reducing the amount of ozone generated and the amount of power consumed. Can be made.

  Of the charging methods using the contact charging method, a roller charging method using a conductive roller as a conductive member is currently widely used from the viewpoint of charging stability. In the roller charging method, a conductive elastic roller is brought into pressure contact with a photosensitive member, and a voltage is applied to the roller to charge the photosensitive member. However, when the photosensitive member is charged by the roller charging method, if there is a minute defect (pinhole) on the surface of the photosensitive member, an abnormal amount of the defective member on the surface of the photosensitive member is removed from the conductive member of the roller. Current leakage occurs. As a result, the surface of the photoconductor is damaged, which adversely affects image formation.

  As a charging method that further improves the problems that occur in this roller charging method, a method is known in which a secondary charging roller is added between a roller-shaped charging member (primary charging roller) to which a voltage is applied and a photosensitive member. (For example, refer to Patent Document 3). Here, the secondary charging roller plays a role of transporting charges from the primary charging roller to the photoconductor, and is provided to solve the problem of current leakage caused by pinholes on the surface of the photoconductor. However, in this method, since the photosensitive member is charged by a minute discharge generated in a narrow gap between the secondary charging roller and the photosensitive member, generation of ozone and NOx during charging cannot be suppressed completely.

  Further, for example, Patent Document 4 discloses a charging method using a contact charging method in which carbon nanotubes are applied as a conductive member. However, when carbon nanotubes are used as the conductive member, the carbon nanotubes are damaged by the pressure when the carbon nanotubes are pressed against the photoreceptor, and the charging ability is reduced.

  As yet another charging method, Patent Document 5 and Patent Document 6 disclose a charging method using an electron-emitting device having a MIS (metal-insulator-semiconductor) structure. In this electron-emitting device, an accelerating electric field for electrons is formed by a potential difference between the upper thin film electrode and the lower thin film electrode provided with the porous semiconductor layer interposed therebetween. High energy electrons generated by the formation of the acceleration electric field are emitted from the surface of the electron-emitting device.

In the charging device including the electron-emitting device as described above, since negative ions are generated only using the electron attachment by the electrons emitted from the electron-emitting device, ozone or ozone is used as in the method using the discharge. NOx is not generated in principle. Non-patent document 1 discloses in detail the electron emission principle and formation method of the porous semiconductor layer made of a porous silicon thin film.
JP 9-114192 A (published May 2, 1997) JP 6-324556 A (published on November 25, 1994) JP 2001-296722 A (released on October 26, 2001) JP 2001-281964 A (published on October 10, 2001) JP 2001-331017 A (published on November 30, 2001) Japanese Patent Laying-Open No. 2001-357961 (released on December 26, 2001) “Light emission and new functions of quantum-size nanosilicon”, Nobuyoshi Koshida et al., Shingaku Technical Report, 1999-06: PP116-121 (1999)

  However, in the electron-emitting device using this porous semiconductor layer, charging (electron trapping) is caused particularly when electrons are emitted into the atmosphere. As a result, the electrons charged in the nano-sized semiconductor fine particles (nanosilicon crystals) constituting the porous semiconductor layer make the electric field inside the porous semiconductor non-uniform and suppress the acceleration of the electrons. As a result, there arises a problem that the amount of electron emission emitted from the electron-emitting device is reduced. In particular, such a problem is more conspicuous as a high voltage is applied to the electron-emitting device in order to increase the charging speed, and the charging becomes unstable and the life of the electron-emitting device is shortened.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a charging device capable of charging the surface of a photoreceptor at high speed and uniformly while maintaining the lifetime of an electron-emitting device, and image formation To provide an apparatus.

  In order to solve the above-described problem, the charging device according to the present invention includes a plurality of electron emission means along the rotation direction of the object to be charged, and the electron emission means disposed on the upstream side in the rotation direction of the object to be charged. After the charged body is charged to a state close to a desired charged state by electrons emitted from the first electron emitting means, the electron emitting means disposed on the downstream side in the rotation direction of the charged body The object to be charged is charged to a desired charged state by electrons emitted from a certain second electron emission means.

  In the charging device according to the present invention, the object to be charged is charged by the electrons emitted from the electron emitting means, so that ozone and NOx are not generated in principle. Furthermore, according to said structure, the several electron emission means is installed along the rotation direction of a to-be-charged body. First, the charged object is charged by the electrons emitted from the first electron emitting means upstream of the charged body in the rotation direction, and then charged by the second electron emitting means located downstream of the charged object in the rotation direction. Let

  As described above, even if the charged amount of the charged body by a certain electron emitting means is insufficient by radiating electrons from the plurality of electron emitting means in a stepwise manner to the charged body, the charged body continues. Since the shortage can be compensated for by other electron emitting means that emits electrons, more uniform and stable charging can be performed. That is, after charging to a state close to a desired charged state by the first electron emitting means, further charging to a desired charged state by the second electron emitting means reduces the variation in the charge amount of the object to be charged. And uniformly charged. In addition, since the object to be charged is charged using a plurality of electron emission means, the voltage application time per electron emission means is shortened and the load is reduced. As a result, the lifetime of the electron emission means can be kept long.

  The number of electron emission means may be two or more. The plurality of electron emission means may include at least the electron emission means functioning as the first and second electron emission means. That's fine.

  In the charging device according to the present invention, it is preferable that a voltage supplied to the first electron emission means is higher than a voltage supplied to the second electron emission means.

  According to the above configuration, when the voltage supplied to the first electron emission means and the voltage supplied to the second electron emission means can be controlled independently, the supply to the first electron emission means. Since the amount of electrons emitted from the first electron emission means increases by making the voltage to be higher than the voltage supplied to the second electron emission means, the charging speed of the charged object can be improved. it can. At this time, since the voltage supplied to the second electron emission means is lower than the voltage supplied to the first electron emission means, variation in the amount of electrons emitted from the second electron emission means is reduced. Thus, the object to be charged can be stably charged. As a result, it is possible to simultaneously improve the charging speed of the member to be charged and reduce the variation in the amount of charge, and to charge the member to be charged uniformly in a shorter time.

  In the charging device according to the present invention, the voltage between the first electron emission means and the object to be charged is determined according to the voltage supplied to each of the first electron emission means and the second electron emission means. The distance is preferably different from the distance between the second electron emitting means and the charged body.

  In the above configuration, for example, when the same voltage is supplied to each of the first electron emission means and the second electron emission means to emit the same amount of electrons, the second electron emission means and the charged object The distance from the body is made longer than the distance between the first electron emitting means and the charged body. As a result, the object to be charged can be charged stepwise, so that more uniform and stable charging can be performed. That is, after charging to a state close to a desired charged state by the first electron emitting means, further charging to a desired charged state by the second electron emitting means reduces the variation in the charge amount of the object to be charged. And uniformly charged.

  In addition, as described above, the first electron emitting means and the second electron emitting means and the second electron emitting means are arranged so that the distance from the first electron emitting means to the object to be charged is different from the distance from the second electron emitting means to the object to be charged. Since the electron emitting means is provided, for example, even when the charged body is eccentric, the charged body can be appropriately charged by a plurality of electron emitting means having different distances to the charged body. As a result, it is possible to reduce the influence of the eccentricity of the member to be charged and perform stable charging.

  In the charging device according to the present invention, the incident angle at which the electrons emitted from the first electron emission means are incident on the surface of the object to be charged is 90 degrees, and the electrons emitted from the second electron emission means are It is preferable that the first electron emission means and the second electron emission means are installed so that an incident angle incident on the surface of the object to be charged is not less than 0 degrees and not more than 90 degrees.

  In the above configuration, for example, when the same voltage is supplied to each of the first electron emission means and the second electron emission means to emit the same amount of electrons, the electrons emitted from the second emission means Is made smaller than the incident angle of the electrons emitted from the first electron emitting means. As a result, the object to be charged can be charged stepwise, so that more uniform and stable charging can be performed. That is, after charging to a state close to a desired charged state by the first electron emitting means, further charging to a desired charged state by the second electron emitting means reduces the variation in the charge amount of the object to be charged. And uniformly charged.

  Further, for example, even if the charged body is decentered and the charging of the charged body by the first electron emitting means becomes unstable, the electrons emitted from the second electron emitting means are decentered on the surface of the charged body. On the other hand, if the light is stably incident at an incident angle closer to 90 degrees, the member to be charged can be appropriately charged. As a result, it is possible to reduce the influence of the eccentricity of the member to be charged and perform stable charging.

  In the charging device according to the present invention, it is preferable that when one of the first electron emitting means and the second electron emitting means emits electrons, the other does not emit electrons.

  Thereby, deterioration of an electron emission means can be reduced and the lifetime of an electron emission means can be kept longer.

  The charging device according to the present invention further includes detection means for detecting a charged state of the object to be charged, and the driving means for controlling the voltage supplied to the second electron emission means is the first detected by the detection means. It is preferable to adjust a voltage supplied to the second electron emission means based on a charged state of the charged body charged by one electron emission means.

  According to said structure, a detection means detects the charging state of the to-be-charged body charged with the electron discharge | released from the 1st electron emission means. The drive means for controlling the voltage supplied to the second electron emission means adjusts the voltage supplied to the second electron emission means based on the charged state of the non-charged body detected by the detection means. That is, it is possible to adjust the amount of electrons emitted from the second electron emission means according to the charged state of the object to be charged by the first electron emission means.

  As a result, for example, even when a shortage occurs in the charged state by the first electron emission means, the shortage can be compensated by the second electron emission means, so that more uniform and stable charging is performed. Is possible.

  The charging device according to the present invention further includes detection means for detecting a charged state of the object to be charged and position adjustment means for adjusting the position of the second electron emission means, and the position adjustment means includes the detection Based on the charged state of the charged object charged by the first electron emitting means detected by the means, the second electron emitting means and the charged object are changed so as to change the distance between the second electron emitting means and the charged object. It is preferable to adjust the position of the electron emission means.

  According to the above configuration, the position adjusting means changes the distance between the second electron emitting means and the charged object based on the charged state of the charged object by the first electron emitting means detected by the detecting means. In addition, the position of the second electron emission means is adjusted. Thereby, for example, even if the charge by the first electron emitting means is uneven due to the eccentricity of the charged object, the position of the second electron emitting means is adjusted, and the second electron emitting means, the charged object, By changing the distance, the charge can be supplemented so that the charged state of the charged body becomes uniform, so that more uniform and stable charging can be performed.

  The charging device according to the present invention further includes detection means for detecting a charged state of the object to be charged and position adjustment means for adjusting the position of the second electron emission means, and the position adjustment means includes the detection Based on the charged state of the charged body charged by the first electron emitting means detected by the means, the incident angle at which electrons emitted from the second electron emitting means enter the surface of the charged body is changed. It is preferable to adjust the position of the second electron emission means so that the

According to the above configuration, the position adjusting means causes the electrons emitted from the second electron emitting means to enter the surface of the object to be charged based on the charged state of the object to be charged by the first electron emitting means detected by the detecting means. The position of the second electron emission means is adjusted so that the incident angle of incidence changes. Thereby, for example, even if the charge by the first emitting means is uneven due to the eccentricity of the charged body, the position of the second electron emitting means is adjusted, and the electrons emitted from the second electron emitting means By changing the incident angle of incidence on the surface of the object to be charged which is eccentric, charging can be supplemented so that the charged state of the object to be charged becomes uniform, so that more uniform and stable charging can be performed.
In the charging device according to the present invention, the plurality of first electron emission means and the plurality of second electron emission means are each arranged in a straight line, and the first electron emission means and the first electron emission means The two electron emission means are preferably arranged in a staggered manner. As a result, the charging failure in the gap on the straight line where the first electron emitting means and the second electron emitting means are aligned is compensated for, and the charging uniformity of the charged object is improved.

  As described above, the charging device according to the present invention includes a plurality of electron emission means, and the charged object is charged stepwise using these electron emission means, so that the lifetime of the electron emission means is maintained. The surface of the member to be charged can be charged at high speed and uniformly.

[First Embodiment]
An embodiment of the charging device of the present invention will be described in detail with reference to FIGS. 1 to 4 as follows. Note that the charging device described in the following embodiment is merely a specific example of the charging device of the present invention, and the present invention is not limited to the following embodiment.

  First, a charging device 1 according to the present invention will be described below with reference to FIG. FIG. 1 is a schematic view schematically showing a charging device 1 of the present invention. As shown in FIG. 1, the charging device 1 includes two electron emission devices 2 and 3. The two electron emission devices 2 and 3 are installed so as to be aligned along the rotation direction of the photosensitive member (charged member) 4, and charge the photosensitive member 4 by emitting electrons to the photosensitive member 4. . These electron-emitting devices 2 and 3 and the photoconductor 4 are installed so as to face each other with a predetermined interval.

  The two electron emission devices 2 and 3 include drive power sources (drive means) 6 and 8 and electron emission elements (electron emission means) 7 and 9, respectively. The electron-emitting device (first electron-emitting device) 7 of the first electron-emitting device 2 located on the upstream side in the rotation direction of the photoconductor 4 is connected to the driving power source 6 and the first electron-emitting device 7 located on the downstream side in the rotation direction of the photoconductor 4. Voltages are independently applied to the electron-emitting devices (second electron-emitting devices) 9 of the second electron-emitting device 3 by the driving power supply 8. The photosensitive member 4 is formed on the surface of a drum-shaped conductive support 5 made of aluminum or the like with a thickness of about 25 μm, and the conductive support 5 is grounded.

  A detailed configuration of the first electron emission device 2 will be described below with reference to FIG. FIG. 2 is a schematic view schematically showing the configuration of the first electron emission device 2. The first electron emission device 2 includes a drive power supply 6 and an electron emission element 7. The electron-emitting device 7 includes a base electrode 20 made of a conductive substrate, an n-type silicon layer 21 formed on the base electrode 20, a non-doped thin polysilicon layer 22 formed on the n-type silicon layer 21, polysilicon The layer 22 includes a porous polysilicon layer 23 in which a part of the layer 22 is made porous, and an acceleration electrode 24 made of a metal film formed on the porous polysilicon layer 23.

  The drive power supply 6 is electrically connected to the base electrode 20 and the acceleration electrode 24 of the electron emitter 7. The drive power supply 6 can supply a voltage such as a direct current, a pulse waveform, a sine waveform, and a triangular waveform to the electron-emitting device 7. The second electron-emitting device 3 includes a drive power supply 8 and an electron-emitting device 9 as in the case of the first electron-emitting device 2, and the electron-emitting device 9 includes the first electron-emitting device shown in FIG. The configuration is the same as the electron-emitting device 7 of the apparatus. The drive power supply 8 functions in the same manner as the drive power supply 6 of the first electron-emitting device, but controls the supply of voltage to the electron-emitting device 9 independently of the drive power supply 6.

  In the electron emission device 2 shown in FIG. 2, a negative voltage with respect to the ground and a positive voltage with respect to the base electrode 20 is applied to the acceleration electrode 24 by the drive power supply 6. Electrons supplied from the drive power supply 6 to the base electrode 20 are accelerated toward the acceleration electrode 24 by an electric field generated by applying a voltage inside the electron-emitting device 7. The accelerated electrons penetrate through the acceleration electrode 24 and are emitted from the electron emission device 2 to the outside. At this time, if the conductive support 5 is grounded as shown in FIG. 1, the electrons emitted from the electron emission surface 25 of the acceleration electrode 24 are attracted to the grounded conductive support 5 and the photosensitive member. 4 is charged on the surface.

  Here, as shown in FIG. 1, in the present invention, the second electron emission device 3 is installed on the downstream side in the rotation direction of the photoconductor 4 from the position where the first electron emission device 2 is installed. . The drive power supply 8 of the second electron emission device 3 is provided independently of the drive power supply 6 of the first electron emission device 2 and is independent of the electron emission elements that are electrically connected to each other. Can be controlled. That is, control is performed so that the potential of each acceleration electrode 24 and the voltage applied between the acceleration electrode 24 and the base electrode 20 are different between the first electron emission device 2 and the second electron emission device 3. can do.

  In the present embodiment, the two electron emission devices are installed so as to be aligned along the rotation direction of the photosensitive member 4, but three or more electron emission devices may be installed in the same manner. Further, as shown in FIG. 3, a plurality of electron emission devices may be installed in the width direction of the photoreceptor 4. FIG. 3 is a schematic view schematically showing another embodiment of the charging device of the present invention. In the present embodiment, the charging device 30 includes a plurality of first electron-emitting devices 31 and a plurality of second electron-emitting devices 32. The plurality of first electron-emitting devices 31 are installed linearly in the width direction of the photoconductor 4. The plurality of second electron emission devices 32 are linearly arranged in the width direction of the photoconductor 4 on the downstream side in the rotation direction of the photoconductor 4 with respect to the first electron emission devices 31 aligned in a straight line. .

  At this time, if the plurality of first electron-emitting devices 31 and the plurality of second electron-emitting devices 32 are arranged in a staggered manner on the straight lines that align with each other, charging failure in the gaps on the straight lines that align with each other can be prevented. This compensates for the effect that the uniformity of charging of the photoreceptor 4 is improved.

  In the configuration as described above, by making the potential of the first electron-emitting device 2 higher than the potential of the second electron-emitting device 3, the photosensitive member 4 can be moved at high speed for the reason described below with reference to FIG. The effect of charging uniformly occurs.

  FIG. 4 is a graph showing the change over time of the charged state of the surface of the body to be charged 4 when the voltage applied to the charging device is changed. Here, 1. When using one electron-emitting device and applying a voltage between the base electrode and the accelerating electrode such that the potential of the accelerating electrode of the electron-emitting device is −650 V and the electron emission amount is −240 μA (charging state 1) 2). 2. Using one electron-emitting device and applying a voltage between the base electrode and the accelerating electrode such that the potential of the accelerating electrode is −650 V and the electron emission amount is −1400 μA (charged state 2); Using two electron-emitting devices, a voltage was applied between the base electrode and the accelerating electrode so that the potential of the accelerating electrode of the first electron-emitting device was −2000 V and the amount of electron emission was −240 μA (charged state). 3) After that, when the potential of the acceleration electrode of the second electron-emitting device is −650 V and a voltage such that the electron emission amount is −240 μA is applied between the base electrode and the acceleration electrode (charging state 4), that is, In the case of charging the photoreceptor in two stages, each photoreceptor was charged to -650V.

  As shown by the charge state 1 and charge state 2 curves shown in FIG. 4, when the charging device includes one electron emission device, the larger the electron emission amount, that is, between the base electrode and the acceleration electrode. The larger the voltage applied to the battery, the more quickly it can be charged. However, if a large amount of electrons are suddenly emitted as shown by the charge state 2 curve, the charged state of the photoreceptor may vary. Further, charging is likely to occur, causing deterioration of the electron-emitting device. As a result, the lifetime of the electron-emitting device is shortened.

  Further, since the potential of the acceleration electrode needs to be equal to a desired charging potential, the potential of the acceleration electrode cannot be changed in order to increase the charging speed. For this reason, when the voltage between the base electrode and the accelerating electrode is lowered to reduce the discharge current as shown by the curve of the charging state 1, it takes a long time to charge the photosensitive member to a desired charging potential.

  In contrast, when charging is performed in two stages of the third and fourth charging states using two electron emitting devices, the potential of the acceleration electrode of the second electron emitting device is equal to the desired charging potential. Then, the potential of the acceleration electrode of the first electron-emitting device can be freely changed. Therefore, by changing the potential of the acceleration electrode of the first electron emission device, it is possible to increase the charging speed while keeping the amount of electron emission small.

  Therefore, the first electron emission device is used to charge the photoconductor in a short time until it reaches a potential not exceeding the desired potential and close to the desired potential, and then the voltage of the acceleration electrode is set to the desired potential. By charging to the desired charging potential with the second electron-emitting device, the photoconductor can be stably charged in a short time while maintaining the lifetime of the electron-emitting device.

  Still another embodiment of the charging device of the present invention will be described below with reference to FIGS. FIG. 5 is a schematic view schematically showing the charging device 50 of the present invention. FIG. 6 is a schematic view schematically showing the charging device 60. As shown in FIG. 5, the electron emission device 51 included in the charging device 50 includes a first electron emission element 53 and a second electron emission element 54. The voltage applied to the two electron-emitting devices 53 and 54 of the electron-emitting device 51 is controlled by one drive power source 52. That is, the voltage applied to the two electron-emitting devices 53 and 54 is the same.

  On the other hand, the distance between the second electron-emitting device 54 and the photoconductor 4 is longer than the distance between the first electron-emitting device 53 and the photoconductor 4. Thereby, for example, when the photosensitive member 4 is decentered, the second electron-emitting device 54 on the downstream side has a smaller rate of change in the distance from the photosensitive member 4 due to the decentering than the first electron-emitting device 53. Therefore, it is not easily affected by eccentricity. For this reason, even if the distance between the photoconductor 4 and the first electron-emitting device 53 varies by 10% per rotation of the photoconductor 4, the distance between the second electron-emitting device 54 and the photoconductor 4 is reduced. If the distance between the electron emission device 10 and the photoconductor 4 is double, the fluctuation per rotation of the photoconductor 4 can be suppressed to 5%. That is, even when the charging of the photoconductor 4 by the first electron-emitting device 53 is non-uniform, the charging can be supplemented so as to be uniform by the second electron-emitting device 54. The influence of the eccentricity on the charged state can be reduced, and uniform charging can be realized.

  Further, since the potential finally reached by the photosensitive member 4 is mainly affected by the charge amount by the second electron-emitting device 54, even if the charge amount by the first electron-emitting device 53 is insufficient, The shortage of the charge amount can be compensated by the second electron-emitting device 54 that is less affected by the eccentricity.

  More specifically, for example, the final charge amount of the photoconductor 4 is 100, the charge amount by the first electron-emitting device 53 is 80, and the charge amount by the second electron-emitting device 54 is 20. When the distance between the first electron-emitting device and the photoconductor 4 is increased due to the eccentricity of the photoconductor 4 and only a desired charge amount of about 80% is obtained, charging by the first electron-emitting device 53 is performed. The amount will be 64. Here, if the second electron-emitting device 54 is similarly affected by the eccentricity, the charge amount by the second electron-emitting device 54 is 16. As a result, the charge amount of the photosensitive member 4 becomes 80, and only 80% of the desired amount can be charged.

  However, since the second electron-emitting device 54 located on the downstream side is less affected by the eccentricity than the first electron-emitting device 53, the second electron-emitting device 54 is not affected by the eccentricity at all. Since the desired charge amount is obtained, the charge amount of the photoreceptor 4 is 84. Furthermore, the charging characteristics of the electron-emitting device are not linear. That is, when the potential of the photosensitive member 4 is low, such as immediately after the start of charging, the charging speed is fast, so that the charging can be performed efficiently. The closer to the desired potential, the slower the charging speed.

  Therefore, the charging of the photosensitive member 4 having a charging amount of 64 can be performed more efficiently at the same time than the charging of the photosensitive member 4 having a charging amount of 80. For example, when the photosensitive body 4 is charged until the charge amount reaches 80 by the first electron-emitting device 53, the second electron-emitting device 54 can charge only 20 more charge amounts. When the photosensitive member 4 is charged until the charge amount reaches 64 by the electron emission element 53, the charge amount 30 can be further charged by the second electron emission element 54. As a result, even if the charge amount by the first electron-emitting device 53 is insufficient, the shortage of charge amount can be compensated by the second electron-emitting device 54.

  Further, the electron emission device 61 included in the charging device 60 shown in FIG. 6 includes a first electron emission element 63 and a second electron emission element 64, similarly to the electron emission device 51 shown in FIG. The elements 63 and 64 are controlled by one drive power supply 62. While the voltages applied to these electron-emitting devices 63 and 64 controlled by the same drive power source 62 are the same, the incident angle of electrons emitted from the first electron-emitting device 63 with respect to the photoreceptor 4 is perpendicular. The second electron-emitting device 63 is disposed so that the incident angle of the electrons emitted from the second electron-emitting device 64 to the photoconductor 4 is not a right angle. 64 is installed.

  Thereby, for example, when the photoreceptor 4 is decentered, electrons emitted from the electron emission surface 25 of the first electron-emitting device 63 do not enter the photoreceptor 4 at a right angle and are emitted from the electron emission surface 25. Even if the charged state of the photoconductor 4 is uneven because the electrons on the upstream side in the rotation direction of the photoconductor 4 reach the photoconductor 4 earlier than the electrons on the downstream side, the second electron-emitting device If the incident angle of the electrons emitted from 64 to the decentered photoconductor 4 is close to a right angle, the influence of decentering of the photoconductor 4 on the charged state can be reduced. Therefore, as in the case of the charging device 50 shown in FIG. 5, even if the charging of the photosensitive member 4 by the first electron-emitting device 63 is nonuniform, the second electron-emitting device 64 makes it uniform. Therefore, the charged state of the photosensitive member 4 is not affected by the eccentricity of the photosensitive member 4, and an effect that uniform charging can be realized is produced.

[Second Embodiment]
Another embodiment of the charging device of the present invention will be described in detail with reference to FIGS. 7 to 11 as follows.

  First, the charging device according to the present embodiment will be described below with reference to FIG. FIG. 7 is a schematic view schematically showing the charging device 70 of the present invention. As shown in FIG. 7, the charging device 70 includes a first electron emission device 71 and a second electron emission device 72, and the surface of the photoconductor 4 is made to emit electrons to the photoconductor 4. Charge. The first and second electron emission devices 71 and 72 are configured by drive power sources 73 and 75 and electron emission elements 74 and 76, respectively, as in the first embodiment. In the present embodiment, the second electron emission device 72 is further provided with a charge sensor (detection means) 77 for detecting the charged state of the photoreceptor 4. The detection device 77 is installed between the first electron emission device 71 and the second electron emission device 72.

  In this charging device 60, for example, the photosensitive body 4 is charged in a short time to a state close to a desired charging potential by the first electron emitting device 71, and the charging state at the stage where the charging by the first electron emitting device 71 is completed Detection is performed using a charging sensor 77. At this time, for example, even if the potential of the photoconductor 4 does not exceed the desired charging potential, if the charging potential is lower than expected, it takes a long time for the second electron-emitting device 72 to charge to the desired charging potential. As a result, there is a possibility that sufficient charging is not performed up to a desired potential, resulting in poor charging.

  Therefore, when the charging potential of the photoconductor 4 detected by the charging sensor 77 is lower than a predetermined value, the drive power source 75 of the second electron emission device 72 is based on information from the charging sensor 77 and the electron emission element 76. The potential of the acceleration electrode 24 is not changed, and the potential of the base electrode 20 is changed. As a result, the voltage applied between the acceleration electrode 24 and the base electrode 20 can be increased, and the amount of electrons emitted from the electron-emitting device 76 can be increased. As a result, poor charging of the photoconductor 4 is prevented, and dynamically stable charging can be performed.

  Further, in the present embodiment, the electron emission device may be configured as shown in FIGS. The electron-emitting device 81 of the charging device 80 shown in FIG. 8 includes a first electron-emitting device 83 and a second electron-emitting device 84, similar to the electron-emitting device 51 shown in FIG. 84 is controlled by one drive power supply 82. The distance between the second electron-emitting device 84 and the photoconductor 4 is longer than the distance between the first electron-emitting device 83 and the photoconductor 4. The electron-emitting device 81 includes a charging sensor 85 between the first electron-emitting device 83 and the second electron-emitting device 84, and further adjusts the position of the second electron-emitting device 84 based on information from the charging sensor 85. A position adjusting device (position adjusting means) (not shown) is provided. The position adjusting device adjusts the position of the second electron-emitting device 84 based on the charge amount of the photoconductor 4 detected by the charging sensor 85, so that the distance between the second electron-emitting device 84 and the photoconductor 4. Adjust.

  Thereby, even if the photosensitive member 4 is decentered and the photosensitive member 4 is not charged as desired by the first electron-emitting device 83, the charging sensor 85 detects the charged state by the first electron-emitting device 83. Accordingly, the position of the second electron-emitting device 84 can be adjusted so that the subsequent charging by the second electron-emitting device 84 is performed as desired. As a result, the amount of charge of the photoconductor 4 by the second electron-emitting device 84 can be adjusted, so that charging failure due to the eccentricity of the photoconductor 4 is prevented, and stable and stable charging can be performed.

  Further, similarly to the electron emission device 60 shown in FIG. 6, the electron emission device 91 included in the charging device 90 shown in FIG. 9 includes a first electron emission device 93 and a second electron emission device 94, and these electron emission devices. The elements 93 and 94 are controlled by one drive circuit 92. The first electron-emitting device 93 is installed so that the incident angle of the electrons emitted from the first electron-emitting device 93 with respect to the photoconductor 4 is at a right angle. The second electron-emitting device 94 is installed so that the incident angle of the emitted electrons with respect to the photoreceptor 4 is not perpendicular.

  The electron-emitting device 91 includes a charging sensor 95 between the first electron-emitting device 93 and the second electron-emitting device 94, and further determines the position of the second electron-emitting device 94 based on information from the charging sensor 95. A position adjusting device (not shown) for adjustment is provided. The position adjusting device adjusts the position of the second electron-emitting device 94 based on the charge amount of the photoconductor 4 detected by the charging sensor 95, so that the electron emitted from the second electron-emitting device 94 is applied to the photoconductor. Adjust the incident angle.

  Thereby, even if the photosensitive member 4 is decentered and the photosensitive member 4 is not charged as desired by the first electron-emitting device 93, the charging sensor 95 detects the charged state by the first electron-emitting device 93. Accordingly, the position of the second electron-emitting device 94 can be adjusted so that the subsequent charging by the second electron-emitting device 94 is performed as desired. As a result, the amount of charge of the photoconductor 4 by the second electron-emitting device 94 can be adjusted, so that charging failure due to the eccentricity of the photoconductor 4 can be prevented, and dynamic and stable charging can be performed. .

  As shown in FIG. 10, the charging device 101 includes a first electron emission device 102 including a driving power source 106 and an electron emission element 107, a second electron including a driving power source 108 and an electron emission element 109. There may be provided a third electron emission device 104 constituted by the emission device 103, the drive power supply 110 and the electron emission element 111, and a fourth electron emission device 105 constituted by the drive power supply 112 and the electron emission element 113. . In this way, a plurality of electron-emitting devices are aligned along the rotation direction of the photoconductor 4, and the photoconductor 4 is charged stepwise using each electron-emitting device, thereby maintaining the lifetime of the electron-emitting device. The photosensitive member 4 can be charged stably in a shorter time.

  Further, when the photosensitive member 4 is charged, electrons do not have to be emitted from all the electron emission devices shown in FIG. The drive power supply may be operated so that electrons are emitted from at least one electron emission device, and the drive power supply of the other electron emission devices may be stopped. Thereby, charging can be suppressed, and deterioration of electron emission efficiency and charging uniformity can be prevented.

  As shown in FIG. 11, the charging device 114 includes a driving power source 117 and two electron-emitting devices 118 and 119, a first electron-emitting device 115, and a driving power source 120 and two electron-emitting devices 121 and 119. A second electron emission device 116 constituted by 122 may be provided. In this configuration, if electrons are emitted by alternately using each electron-emitting device, charging of the electron-emitting device can be suppressed, and the life of the device can be extended. Furthermore, since it is possible to prevent a decrease in the amount of electrons emitted from the electron-emitting device, it is possible to perform charging stably and uniformly. Further, the same effect can be obtained even when electrons are emitted by alternately using two electron-emitting devices included in each electron-emitting device.

  In addition, this invention is not limited to each embodiment mentioned above, A various change is possible in the range shown to the claim. In other words, embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the technical scope of the present invention.

(Other configurations)
The present invention can also be expressed as follows.

(First configuration)
An apparatus for charging an object to be charged by an electron emitting device including an electron emitting element, wherein a plurality of the electron emitting devices are installed along a rotation direction of the object to be charged.

(Second configuration)
The charging device according to the first configuration, wherein the plurality of electron-emitting devices are applied with voltages having different potentials.

(Third configuration)
The charging device according to any one of the first and second configurations, wherein the plurality of electron-emitting devices are installed at different distances.

(Fourth configuration)
The charging device according to any one of the first to third configurations, wherein the plurality of electron-emitting devices are installed so as to emit electrons at an incident angle that is not perpendicular to an object to be charged. .

(Fifth configuration)
In the charging device, the plurality of electron emission devices are characterized in that the potential of the electron emission device installed on the upstream side in the rotation direction of the object to be charged is higher than the potential of the electron emission device installed on the downstream side. The charging device according to any one of the first to fourth configurations.

(Sixth configuration)
The charging device includes a mechanism for monitoring a charge amount of a member to be charged, and a voltage applied to a downstream electron-emitting device can be adjusted according to the charge amount of the member to be charged. The charging device according to the configuration.

(Seventh configuration)
The charging device includes a mechanism for monitoring a charge amount of a member to be charged, and the distance between the electron emission device on the downstream side and the member to be charged can be adjusted according to the charge amount of the member to be charged. The charging device according to any one of -6.

(Eighth configuration)
The charging device includes a mechanism for monitoring a charge amount of a member to be charged, and an electron emission angle of the downstream electron emission device with respect to the member to be charged can be adjusted according to the charge amount of the member to be charged. The charging device according to 1 to 7.

(Ninth configuration)
The charging device according to any one of the first to eighth configurations, wherein at least one of the plurality of electron-emitting devices has a time zone during which electrons are not emitted.

  The charging device according to the present invention does not generate ozone or NOx in principle, and can uniformly charge a charged object in a short time. Therefore, in particular, an electrophotographic copying machine, printer, facsimile, etc. It can be applied to an image forming apparatus.

It is the schematic which showed typically the charging device in one Embodiment of this invention. It is a schematic diagram which shows the structure of the electron emission apparatus in the charging device of this invention. It is the upper part schematic diagram showing typically the charging device in other embodiments of the present invention. It is a figure which shows the time change of the charging state of the to-be-charged body 4 surface when the voltage applied to an electron emission apparatus is changed. It is the schematic which showed typically the charging device in other embodiment of this invention. It is the schematic which showed typically the charging device in other embodiment of this invention. It is the schematic which showed typically the charging device in other embodiment of this invention. It is the schematic which showed typically the charging device in other embodiment of this invention. It is the schematic which showed typically the charging device in other embodiment of this invention. It is the schematic which showed typically the charging device in other embodiment of this invention. It is the schematic which showed typically the charging device in other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Charging apparatus 2 1st electron emission apparatus 3 2nd electron emission apparatus 4 Photoconductor (charged body)
5 conductive support 6 drive power supply (drive means)
7 Electron emitting device (first electron emitting means)
8 Driving power source 9 Electron emitting device (second electron emitting means)
77 Charging sensor (detection means)

Claims (10)

A plurality of electron emission means are provided along the rotation direction of the member to be charged,
After charging the charged object to a state close to a desired charged state by electrons emitted from the first electron emitting means that is the electron emitting means arranged on the upstream side in the rotation direction of the charged object, it is charging the member to be charged to a charging state desired by electrons emitted from the second electron emission unit, which is the electron-emitting means disposed downstream in the rotation direction of the member to be charged,
The plurality of first electron emission means and the plurality of second electron emission means are each arranged linearly in the width direction of the charged body, and the first electron emission means and the second electron emission means a charging device and the electron-emitting means is characterized that you have been staggered.   2. The charging device according to claim 1, wherein a voltage supplied to the first electron emission unit is higher than a voltage supplied to the second electron emission unit. According to the voltage supplied to each of the first electron emission means and the second electron emission means,
The first electron emitting means and the first electron emitting means and the charged object so that the distance between the first electron emitting means and the charged object is different from the distance between the second electron emitting means and the charged object. The charging device according to claim 1, wherein the second electron emission unit is installed. According to the voltage supplied to each of the first electron emission means and the second electron emission means,
The incident angle at which the electrons emitted from the first electron emitting means are incident on the surface of the member to be charged is 90 degrees, and the electrons emitted from the second electron emitting means are incident on the surface of the member to be charged. 2. The charging device according to claim 1, wherein the first electron-emitting device and the second electron-emitting device are installed so that an incident angle is not less than 0 degrees and not more than 90 degrees.   2. The charging device according to claim 1, wherein when one of the first electron emitting unit and the second electron emitting unit emits an electron, the other does not emit an electron. It further comprises detection means for detecting the charged state of the object to be charged,
The driving means for controlling the voltage supplied to the second electron emission means is configured to control the second electron emission based on the charged state of the charged body charged by the first electron emission means detected by the detection means. The charging device according to claim 1, wherein a voltage supplied to the electron emitting means is adjusted. Detecting means for detecting a charged state of the object to be charged;
A position adjusting means for adjusting the position of the second electron emitting means,
According to the voltage supplied to each of the first electron emission means and the second electron emission means,
The position adjusting unit is configured to determine a distance between the second electron emitting unit and the charged body based on a charged state of the charged body charged by the first electron emitting unit detected by the detecting unit. 2. The charging device according to claim 1, wherein the position of the second electron emission unit is adjusted so as to change the voltage. Detecting means for detecting a charged state of the object to be charged;
A position adjusting means for adjusting the position of the second electron emitting means,
According to the voltage supplied to each of the first electron emission means and the second electron emission means,
The position adjusting unit is configured to cause the electrons emitted from the second electron emitting unit to emit electrons based on the charged state of the charged member charged by the first electron emitting unit detected by the detecting unit. The charging device according to claim 1, wherein the position of the second electron emission unit is adjusted so as to change an incident angle incident on the surface. An image forming apparatus comprising the charging device according to claim 1. A charging method comprising charging a member to be charged using the charging device according to claim 1.

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