JP2015121750A - Electron emission device, charging device with the electron emission device, image formation apparatus with the electron emission device, and method of controlling the electron emission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electron emission device capable of having its lifetime prolonged by stably controlling the charging amount and charging potential of an electron emission object such as a photoreceptor drum.SOLUTION: A control part 119 finds an estimated value MIe of a discharging current amount Ie corresponding to the amount (electron emission amount) of emitted electrons emitted from an electron emission element (111) based upon an in-element current amount Ip measured by an inflow ammeter 117 and a temperature T and a humidity H around the electron emission element 111 measured by an environment detection part 118, and controls a driving voltage Vd of a driving power source 115 so that the estimated value MIe reaches a target value AIe of the discharging current amount Ie.

Description

  The present invention relates to an electron-emitting device including an electron-emitting device that emits electrons by applying a voltage, a charging device including the electron-emitting device, an image forming apparatus including the charging device, and an electron-emitting device It relates to a control method.

  As is well known, in an electrophotographic image forming apparatus, the surface of a photoconductor is uniformly charged by a charging device, and the surface of the photoconductor is exposed to form an electrostatic latent image on the surface of the photoconductor. Develop the electrostatic latent image. Although some charging devices use corona discharge, there is a drawback that a large amount of discharge products such as ozone and NOx are generated. For this reason, in Patent Document 1, Patent Document 2, and Patent Document 3, an electron-emitting device is configured by using an electron-emitting device capable of suppressing the generation of discharge products, and this electron-emitting device is used in an image forming apparatus. It is applied as a charging device.

  Next, an example of a conventional electron emission device will be described with reference to FIG. FIG. 9 is a diagram schematically showing an example of a conventional electron emission device. As shown in FIG. 9, a conventional electron emission device 201 includes an electron emission element 211, power supply terminals 212a and 212b, a base 213, a drive power supply 214, an electric field generation power supply 215, an inflow ammeter 216, a recovery ammeter 217, And a control unit 218.

  Here, the electron-emitting device 211 of the electron-emitting device 201 is disposed at a predetermined interval from the photosensitive drum 221, and the photosensitive drum is driven by the electrons emitted from the electron-emitting device 211 while the photosensitive drum 221 is rotationally driven. The surface of 221 is uniformly charged. The photoconductor drum 221 is formed by laminating a photoconductor layer or the like on the outer periphery of a metal cylinder 221 a. The metal cylinder 221 a is grounded, and electric charges are accumulated on the surface of the photoconductor drum 221.

  The electron-emitting device 211 includes a metal substrate 211a fixed to the lower surface of the pedestal 213, an inorganic insulator layer 211b formed on the substrate 211a, and a surface electrode 211c formed on the inorganic insulator layer 211b. Is a three-layer structure.

  Further, each of the power supply terminals 212 a and 212 b is fixed to the side portion of the base 213, and is arranged so that the tip thereof is in contact with the surface electrode 211 c of the electron emission element 211. The driving power source 214 is connected to the substrate 211a of the electron-emitting device 211 and is connected to the surface electrode 211c of the electron-emitting device 211 via the power supply terminals 212a and 212b, and a direct current is connected between the substrate 211a and the surface electrode 211c. A drive voltage Vd such as a pulse waveform, a sine waveform, or a triangular waveform is applied. By applying the drive voltage Vd, electrons are accelerated in the inorganic insulator layer 211b, and the accelerated electrons (emission current amount Ie) are emitted into the atmosphere from the surface electrode 211c or the vicinity of the surface electrode 211c.

  Further, the electric field generating power source 215 is connected to the surface electrode 211c via the power supply terminals 212a and 212b, and applies a predetermined electric field generating voltage Ve between the surface electrode 211c and the grounding point. As a result, an electric field is generated between the surface electrode 211c and the cylinder 221a of the photosensitive drum 221, and electrons emitted from the surface electrode 211c or the vicinity of the surface electrode 211c by this electric field move to the surface of the photosensitive drum 221. To do. The distance between the surface electrode 211c and the surface of the photosensitive drum 221 is not particularly limited as long as the electrons emitted from the surface electrode 211c can reach the surface of the photosensitive drum 221.

  On the other hand, the inflow ammeter 216 is inserted between the driving power source 214 and the substrate 211 a of the electron emission element 211 and measures the in-element current amount Ip flowing into the electron emission element 211. The recovery ammeter 217 is connected to the surface electrode 211c of the electron-emitting device 211 via the power supply terminals 212a and 212b, and measures the recovery current amount Ic recovered without being emitted from the surface electrode 211c into the atmosphere. . Note that the arrow directions of the in-element current amount Ip and the recovered current amount Ic in FIG. 9 indicate the direction of current flow, and are opposite to the direction of electron flow.

  The control unit 218 controls the drive power supply 214 to adjust the drive voltage Vd applied to the surface electrode 211c of the electron-emitting device 211. The in-device current amount Ip measured by the inflow ammeter 216 and the recovery Based on the recovered current amount Ic measured by the ammeter 217, the drive voltage Vd is adjusted so that the emission current amount Ie becomes a preset target value.

  As described above, conventionally, the charge amount and the charge potential on the surface of the photosensitive drum 221 are controlled by monitoring the emission current amount Ie emitted from the electron-emitting device 211 and controlling the drive voltage Vd in real time.

JP 2001-357916 A JP 2006-323366 A JP 2010-2867 A

  However, the electron emission efficiency η of the electron-emitting device 211 is usually very small as 0.01% or less. The electron emission efficiency η is the ratio of the emission current amount Ie emitted into the atmosphere in the device current amount Ip flowing through the electron emission device, and is expressed by the following equation (1). Further, the emission current amount Ie is expressed by the following equation (2).

η = Ie / Ip = (Ip−Ic) / Ip (1)
Ie = (Ip−Ic) (2)
Here, since η = 0.0001 (0.01%) or less, it can be considered that Ip≈Ic based on the above equation (1). For this reason, even if the in-device current amount Ip and the recovered current amount Ic are measured and the emission current amount Ie is obtained based on the above equation (2) as in the conventional case, the SN ratio is too small and accurate emission is performed. It was difficult to obtain the current amount Ie. As a result, there has been a problem that the amount of charge on the surface of the photosensitive drum 221 and the charged potential cannot be accurately controlled.

  Even within the service life limit of the electron-emitting device 201, if the surface electrode 211c of the electron-emitting device 211 deteriorates with the passage of time, the emission current amount Ie decreases and becomes smaller. There has been a problem that it becomes more difficult to control the charge amount and the charge potential on the surface of 221 and the charge amount and the charge potential cannot be maintained at predetermined values. In order to avoid this, it is conceivable that a driving voltage higher than necessary is applied to the surface electrode 211c from the beginning of use of the electron-emitting device 201. In this case, the deterioration of the surface electrode 211c is accelerated, and the electron-emitting device 211 is accelerated. There has been a problem that the life of the product becomes shorter.

  In view of the above problems, an object of the present invention is to provide an electron emission device capable of stably controlling the charge amount and charge potential of an electron emission object such as a photosensitive drum and extending the life of the device, and its electron emission It is an object of the present invention to provide a charging device including the apparatus, an image forming apparatus including the charging device, and a method for controlling the electron emission device.

  In order to solve the above problems, an electron-emitting device according to the present invention includes a first electrode, a second electrode, and an electron-emitting device having an intermediate layer provided between the first electrode and the second electrode; An electron emission apparatus comprising: a drive power source that applies a drive voltage between the first electrode and the second electrode to emit electrons from the electron emission element; and the inside of the element that flows through the electron emission element An in-element current detection unit that detects current, an environment detection unit that detects temperature or humidity of an environment in which the electron-emitting device is placed, an in-element current detected by the in-element current detection unit, and the environment detection unit And a control unit that controls the drive voltage of the drive power source based on the temperature or humidity detected by.

  In such an electron emission device of the present invention, the drive voltage of the drive power source is controlled based on the in-element current detected by the in-element current detector and the temperature or humidity detected by the environment detector. Here, it is easy to suppress the detection error of the in-element current by the in-element current detection unit and the detection error of the temperature or humidity by the environment detection unit. For this reason, the electron emission amount of the electron-emitting device can be controlled with high accuracy by controlling the drive voltage based on the current in the device and the temperature or humidity.

  Further, in the electron emission device of the present invention, the control unit is emitted from the electron emission device based on the element current detected by the element current detection unit and the temperature or humidity detected by the environment detection unit. An estimated value of the electron emission amount or emission current amount is obtained, and the drive voltage of the drive power source is controlled so that the estimated value becomes a preset target value of the electron emission amount or emission current amount.

  Since the estimated value of the electron emission amount or the emission current amount is obtained based on the in-element current with a small detection error and the temperature or humidity with the same detection error, the accuracy as an approximate value of the emission current amount is high. Therefore, by controlling the drive voltage of the drive power supply so that the estimated value becomes the target value of the emission current amount, the actual emission current amount can be controlled with high accuracy in real time.

  Furthermore, in the electron emission device of the present invention, the control unit continuously maintains the target value at a constant value within the service life limit of the electron emission device.

  As a result, a certain amount of discharge electrons are always emitted from the electron discharge element within the limit of the lifetime of the electron emission device, and deterioration of the surface electrode of the electron discharge element due to electron emission can be minimized. In addition, the lifetime of the electron-emitting device can be increased.

  Next, an electron-emitting device according to the present invention includes a first electrode, a second electrode, an electron-emitting device having an intermediate layer provided between the first electrode and the second electrode, the first electrode, An electric field is generated between a driving power source that applies a driving voltage to the second electrode to emit electrons from the electron-emitting device, and the second electrode and an electron emission target facing the second electrode. An electron emission device comprising: an electric field generation power source that generates an electric field that applies a voltage to move the electrons from the second electrode to the electron emission target; An electric field current detection unit that detects a current flowing to the two electrodes, and a control unit that controls the drive voltage of the drive power source based on the current detected by the electric field current detection unit.

  In such an electron emission device of the present invention, the drive voltage of the drive power supply is controlled based on the current flowing from the electric field generating power supply detected by the electric field current detection unit to the second electrode. Here, it is easy to suppress a current detection error by the electric field current detector. For this reason, the electron emission amount of the electron-emitting device can be controlled with high accuracy by controlling the driving voltage based on the detected current.

  Further, in the electron emission device of the present invention, the control unit sets the current detected by the electric field current detection unit as an estimated amount of electron emission amount or emission current amount emitted from the electron emission element, and The drive voltage of the drive power supply is controlled so that the estimated value becomes a preset target value of the electron emission amount or the emission current amount.

  Since the estimated value of the electron emission amount or the emission current amount is obtained based on a current having a small detection error flowing from the electric field generating power source to the second electrode, the accuracy as an approximate value of the emission current amount is high. Therefore, by controlling the drive voltage of the drive power supply so that the estimated value becomes the target value of the emission current amount, the actual emission current amount can be controlled with high accuracy in real time.

  Furthermore, in the electron emission device of the present invention, the control unit continuously maintains the target value at a constant value within the service life limit of the electron emission device.

  As a result, a certain amount of discharge electrons are always emitted from the electron discharge element within the limit of the lifetime of the electron emission device, and deterioration of the surface electrode of the electron discharge element due to electron emission can be minimized. In addition, the lifetime of the electron-emitting device can be increased.

  Next, a charging device of the present invention includes the electron emission device of the present invention.

  The image forming apparatus of the present invention includes the charging device of the present invention.

  Such a charging device and an image forming apparatus also have the same effects as the electron emission device of the present invention.

  Next, a method for controlling an electron-emitting device according to the present invention emits electrons from an electron-emitting device having a first electrode, a second electrode, and an intermediate layer provided between the first electrode and the second electrode. In order to achieve this, there is provided a control method for an electron emission device that applies a drive voltage between the first electrode and the second electrode, wherein an in-element current flowing through the electron emission element is detected, and the electron emission element is The temperature or humidity of the placed environment is detected, and the drive voltage of the drive power supply is controlled based on the detected current in the element and the detected temperature or humidity.

  In addition, according to the method for controlling an electron-emitting device of the present invention, electrons are emitted from an electron-emitting device having a first electrode, a second electrode, and an intermediate layer provided between the first electrode and the second electrode. For this purpose, a driving voltage is applied between the first electrode and the second electrode to generate an electric field that moves the electrons from the second electrode to an electron emission target facing the second electrode. And a method of controlling an electron emission device for applying an electric field generation voltage between the second electrode and the electron emission target, wherein a current flowing from the electric field generation power source to the second electrode is detected, The drive voltage of the drive power supply is controlled based on the detected current.

  Also in such a control method of an electron discharge device, the same effects as the electron emission device of the present invention are obtained.

  In the present invention, the drive voltage of the drive power supply is controlled based on the in-element current detected by the in-element current detection unit and the temperature or humidity detected by the environment detection unit. Here, it is easy to suppress the detection error of the in-element current by the in-element current detection unit and the detection error of the temperature or humidity by the environment detection unit. For this reason, the electron emission amount of the electron-emitting device can be controlled with high accuracy by controlling the drive voltage based on the current in the device and the temperature or humidity.

  Further, the drive voltage of the drive power supply is controlled based on the current flowing from the electric field generating power supply detected by the electric field current detection unit to the second electrode. Here, it is easy to suppress a current detection error by the electric field current detector. For this reason, the electron emission amount of the electron-emitting device can be controlled with high accuracy by controlling the driving voltage based on the detected current.

It is sectional drawing which shows the internal structure of the image forming system to which embodiment of the electronic discharge apparatus of this invention is applied. FIG. 2 is a diagram schematically illustrating a charging unit and a photosensitive drum according to the first embodiment. FIG. 3A is a plan view showing the charging unit of FIG. 2 as viewed from the electron emission surface, and FIG. 3B is a cross-sectional view showing the charging unit of FIG. It is a figure which shows notionally the data table used with the charging unit of FIG. 3 is a graph showing the characteristics of the electron emission efficiency with respect to the drive voltage of the electron-emitting device obtained by Experimental Example 1 relating to the charging unit of FIG. 2. It is a figure which shows typically the charging unit and photoreceptor drum of 2nd Embodiment. 7 is a chart showing a relationship between a drum current amount and an electric field generated current amount obtained by Experimental Example 2 relating to the charging unit of FIG. 6. It is a figure which shows typically the charging unit and photoreceptor drum of 3rd Embodiment. It is a figure which shows the conventional charging unit and a photoreceptor drum typically.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view showing an internal configuration of an image forming system 1 to which an embodiment of an electronic discharge device of the present invention is applied. The image forming system 1 includes peripheral devices such as a scanner 3, an automatic document conveying device 4, a post-processing device 5, a paper feeding device 6, a relay conveying unit 8, and a double-sided conveying device 10 with an image forming apparatus 2 as a center. Combined, the system functions are expanded. Among these, the image forming apparatus 2 and the post-processing apparatus 5 are placed side by side on the paper supply apparatus 6. Further, the scanner 3 and the automatic document feeder 4 are provided on the system rack 7 so as to be disposed above the image forming apparatus 2 and the post-processing apparatus 5. Further, a moving roller 55 and a fixed portion 54 are provided on the lower surface of the paper supply device 6. The fixing unit 54 is rotated and raised, the fixing unit 54 is separated from the floor surface, the moving roller 55 is brought into contact with the floor surface, and the sheet supply device 6 is moved in this state, and the sheet supply device 6 and the image are moved. The forming apparatus 2 and the post-processing apparatus 5 are disposed inside the system rack 7, the fixing portion 54 is rotated and lowered, the fixing portion 54 is brought into contact with the floor surface, and the moving roller 55 is separated from the floor surface. The paper supply device 6 is fixed.

  The image forming apparatus 2 not only records and outputs an image read by the scanner 3 but also records and outputs an image received and input from an external device such as a personal computer through a network or the like.

  An electrophotographic process unit 11 is disposed substantially on the left side of the center of the image forming apparatus 2. In the electrophotographic process unit 11, a charging unit 21 that uniformly charges the surface of the photosensitive drum 15 around the photosensitive drum 15, and a light image is scanned on the surface of the uniformly charged photosensitive drum 15 to electrostatic latent image. An optical scanning unit 22 for writing an image, a developing unit 12 for developing the electrostatic latent image written by the optical scanning unit 22 with toner, a transfer unit 13 for transferring a toner image formed on the surface of the photosensitive drum 15 to a recording sheet, The developer remaining on the surface of the photosensitive drum 15 after the transfer is removed to remove a charge on the surface of the photosensitive drum 15 and the cleaning unit 14 that makes it possible to record a new toner image on the surface of the photosensitive drum 15. A static elimination lamp unit (not shown) is arranged.

  In addition, a paper supply unit 16 that houses and supplies recording paper is disposed in the lower part of the main body of the image forming apparatus 2. The paper supply unit 16 includes a paper storage tray 16a that stores recording paper and a separation supply unit 16b that separates and feeds the recording paper stored in the paper storage tray 16a one by one. The recording sheets separated and fed one by one by the separation supply unit 16b are conveyed to the nip area between the photosensitive drum 15 and the transfer unit 13, and the toner image formed on the surface of the photosensitive drum 15 is conveyed. Is transcribed.

  Further, the paper supply device 6 is optionally attached and has three paper supply units 56, 57, and 58. In the paper supply units 56, 57, and 58, the recording papers stored in the paper storage trays 56a, 57a, and 58a are separated one by one by the separation feeding units 56b, 57b, and 58b provided respectively. Then, the sheet is supplied to the image forming apparatus 2 through the sheet discharge opening 53 and the sheet receiving opening 27 formed in the lower part of the main body of the image forming apparatus 2. In the image forming apparatus 2, the recording sheet supplied through the sheet receiving port 27 is conveyed to the nip area between the photosensitive drum 15 and the transfer unit 13, and the recording sheet is formed on the surface of the photosensitive drum 15. Transfer the toner image.

  Here, when the image forming apparatus 2 is in operation, the recording paper is exposed to light by selectively operating either the paper supply unit 16 containing the recording paper of a desired size and each of the paper supply units 56, 57, and 58. The toner image can be transferred to the recording paper by being conveyed and supplied to the nip area between the body drum 15 and the transfer unit 13.

  A fixing device 23 is disposed above the electrophotographic process unit 11. The fixing device 23 receives the recording sheet on which the toner image is transferred, heat-fixes the toner image transferred onto the recording sheet, and discharges the recording sheet. This recording sheet is conveyed to the relay conveyance unit 8 on the upper side of the main body of the image forming apparatus 2 through the sheet discharge roller 28. Accordingly, the sheet conveyance path of the image forming apparatus 2 is configured in a substantially vertical shape from the bottom to the top.

  The relay conveyance unit 8 relays and conveys the recording paper conveyed from the paper discharge roller 28 of the image forming apparatus 2 to the post-processing apparatus 5 or discharges it to the discharge tray 9. Switching between the relay conveyance of the recording paper to the post-processing device 5 and the discharge of the recording paper to the discharge tray 9 is performed by a gate 46 arranged at a branch portion of the conveyance path of the recording paper.

  In the post-processing device 5, when the recording paper is conveyed from the image forming apparatus 2 through the relay conveyance unit 8, the recording paper is introduced through the carry-in roller 41 and post-processing is performed on the recording paper. Post-processing includes stapling, punching, sorting, and the like. The post-processing device 5 performs stapling, and discharges recording paper subjected to stapling to a lower discharge tray 45. The recording paper that has not been subjected to the stapling process is discharged to the upper discharge tray 44. Switching of recording paper discharge to each of the paper discharge trays 44 and 45 is performed by a switching gate 43.

  Further, the double-sided conveyance device 10 reverses the front and back of the recording paper when recording toner images on both sides of the recording paper. When recording toner images on both sides of the recording paper, the toner image is recorded on the surface of the recording paper, and when the recording paper is conveyed to the paper discharge roller 28, the recording paper is conveyed by the paper discharge roller 28. In the middle, the paper discharge roller 28 is temporarily stopped, the paper discharge roller 28 is reversely rotated, the recording paper is guided to the double-sided conveying device 10 by switching the gate 47, and the recording paper is passed through the double-sided conveying device 10 to the electrophotographic process. The recording paper is guided again to the unit 11, the front and back sides of the recording paper are reversed, the toner image is recorded on the back surface of the recording paper by the electrophotographic process unit 11, and the recording paper is conveyed to the relay conveyance unit 8 through the paper discharge roller 28. The

  On the other hand, the scanner 3 reads an image of a document that is conveyed on the document placement table 30 by the automatic document conveyance device 4 and an image of the document placed on the document placement table 30 by a user's manual operation. Operates in either manual reading mode or reading. In the scanner 3, the first scanning unit 31 and the second scanning unit 32 are moved with respect to each other at a predetermined speed, or are positioned at their respective specified positions, and the light source of the first scanning unit 31 is used on the document table 30. The original is exposed, the reflected light from the original is guided to the photoelectric conversion element 34 through the imaging lens 33 by the mirrors of the first scanning unit 31 and the second scanning unit 32, and the image of the original is read by the photoelectric conversion element 34. Then, image data indicating the image of the document is output.

  In the automatic document feeder 4, in the automatic reading mode, the document is pulled out from the document set tray 40 and conveyed onto the document table 30, and further, the document is conveyed from the document table 30 to the document discharge tray 42. Discharge. Further, since it is necessary to place the document on the document placing table 30 in the manual reading mode, the automatic document feeder 4 is supported so as to be reciprocally rotatable with the rear side of the device 4 as a fulcrum. The front side can be opened.

  In the space above and below the optical scanning unit 22, an apparatus control unit 24, an image control unit 25, a power supply unit 26 that supplies power to these units, and the like are arranged. The apparatus control unit 24 includes a process control unit (PCU) substrate that controls the electrophotographic process unit 11 and an interface substrate that receives and inputs image data from an external device such as a personal computer. In addition, the image control unit 25 performs predetermined image processing on the image data output from the scanner 3 or the image data received and input to the interface board, and controls the optical scanning unit 22 to correspond to the image data. An image control unit (ICU) substrate for forming an electrostatic latent image on the surface of the photosensitive drum 15 is provided.

By the way, the charging unit 21 in the electrophotographic process unit 11 of the image forming apparatus 2 is an application of the embodiment of the electrodischarge apparatus of the present invention. In the electron discharge device of this embodiment, since an electron-emitting device that emits electrons by applying a voltage is used, the generation of discharge products such as ozone and NOx can be suppressed, and the surface of the photosensitive drum 15 It is possible to stably control the charging potential of the electronic discharge device and to extend the life of the electronic discharge device.
<First Embodiment>
Next, the charging unit 21, which is the first embodiment of the electronic discharge device of the present invention, will be described in detail with reference to FIGS. 2, 3A, and 3B.

  FIG. 2 is a diagram schematically illustrating the charging unit 21 and the photosensitive drum 15 according to the first embodiment. FIG. 3A is a plan view showing the charging unit 21 as viewed from the electron emission surface, and FIG. 3B is a cross-sectional view showing the charging unit 21.

  2 and 3A and 3B, the charging unit 21 includes an electron-emitting device 111, power supply terminals 112 and 113, a pedestal 114, a driving power source 115, an electric field generating power source 116, an inflow ammeter 117, and an environment. A detection unit 118 and a control unit 119 are provided.

  Here, the electron emission element 111 of the charging unit 21 is arranged at a predetermined interval from the surface of the photosensitive drum 15, and the photosensitive drum is driven by the electrons emitted from the electron emission element 111 while the photosensitive drum 15 is rotationally driven. 15 surfaces are uniformly charged. The photoconductor drum 15 is formed by laminating a photoconductor layer or the like on the outer periphery of a metal cylinder 15a. The metal cylinder 15a is grounded, and electric charges are accumulated on the surface of the photoconductor drum 15.

  The electron-emitting device 111 includes a metal substrate 121 fixedly supported on the lower surface of the pedestal 114, an inorganic insulator layer 122 formed on the substrate 121, and a surface electrode formed on the inorganic insulator layer 122. 3 layer structure.

  The substrate 121 is a rectangular thin plate made of a conductive material, and an inorganic insulator layer 122 is formed on the substrate 121, and a surface electrode 123 is formed on the inorganic insulator layer 122. An inorganic insulator layer 122 is sandwiched between the surface electrode 123. The surface electrode 123 includes two bus line portions 123a and 123b extending in the longitudinal direction of the electron-emitting device 111 and a plurality of comb electrode portions 123c that connect the bus line portions 123a and 123b. Each comb-tooth electrode portion 123c extends obliquely with respect to the longitudinal direction of the electron-emitting device 111, and is arranged parallel to each other with a space between each other, and the inorganic insulator layer 122 is interposed between the comb-tooth electrode portions 123c. Is exposed.

  For example, the substrate 121 is formed by forming an aluminum plate having a thickness of 0.4 mm. The inorganic insulator layer 122 is made of a material containing a main resin and conductive fine particles dispersed in the resin, and the surface of the substrate 121 is formed by a spin coat method, a doctor blade method, a spray method, a dipping method, or the like. To a thickness of about 1 μm. Therefore, the inorganic insulator layer 122 has characteristics as an insulator or a semiconductor. As the resin, an insulating resin material such as a silicone resin can be used. As the conductive fine particles, fine particles such as conductors and semiconductors can be used. Specific examples of the conductive fine particles include metal fine particles made of gold, silver, platinum, palladium, and the like. In addition, as the inorganic insulator layer 122, another kind of insulator layer, semiconductor layer, or a combination of a plurality of materials may be applied. In short, electrons are transferred between the substrate 121 and the surface electrode 123. Any kind of thing may be used as long as it can be accelerated.

  The material of the surface electrode 123 is not particularly limited as long as a voltage can be applied to the inorganic insulator layer 122. However, it is desirable that the surface electrode 123 be capable of emitting electrons that have been accelerated and become high energy in the inorganic insulator layer 122 without loss of energy as much as possible. From this viewpoint, it is preferable to form the surface electrode 123 with a material having a low work function and capable of forming a thin film. Examples of such a material include gold, silver, carbon, titanium, nickel, and aluminum. In the first embodiment, the surface electrode 123 is formed by forming a gold thin film having a thickness of 50 nm by sputtering. Further, as the surface electrode 123, another type of conductor or the like, a combination of a plurality of materials, or the like, further covering the entire surface of the inorganic insulator layer 122 may be applied. In short, electrons are emitted. As long as it is possible, it may be of any kind and shape.

  The pedestal 114 is made of an insulating material and is rectangular when viewed from the top like the substrate 121 and has a rectangular parallelepiped shape. The length of the pedestal 114 corresponds to the entire length of the electron-emitting device 111. The pedestal 114 is for fixing and supporting the electron-emitting device 111 and the power supply terminals 112 and 113, and a plurality of power supply terminals 112 and 113 are screwed to both sides of the rectangular parallelepiped shape. Screw holes (not shown) are formed. In the first embodiment, polyacetal (POM), which is an insulating resin, is used as the material for the pedestal 114.

  Each power supply terminal 112, 113 is made of a thin metal plate, and has side plate portions 112a, 113a and a plurality of contact portions 112b, 113b bent at the lower ends of the side plate portions 112a, 113a. It is L-shaped. In the first embodiment, the power supply terminals 112 and 113 are formed from a stainless steel plate having a thickness of 0.15 mm.

  The side plate portions 112a and 113a of the power supply terminals 112 and 113 have a length slightly shorter than that of the electron-emitting device 111, and the side plate portions 112a and 113a are in contact with both side surfaces of the pedestal 114 so that a plurality of side plate portions 112a and 113a Screws are screwed into the screw holes on both side surfaces of the pedestal 114 through the holes of the side plate portions 112a and 113a to fix the power supply terminals 112 and 113, respectively. Further, the contact portions 112 b and 113 b of the power supply terminals 112 and 113 are connected to the bus line portions 123 a of the surface electrode 123 by fixing the side plate portions 112 a and 113 a of the power supply terminals 112 and 113 to both side surfaces of the base 114. , 123b is pressed and brought into contact. As a result, the power supply terminals 112 and 113 and the bus line portions 123a and 123b of the surface electrode 123 are electrically connected. At the same time, the electron-emitting device 111 is fixedly supported by being pressed against the pedestal 114 from both sides in the width direction of the electron-emitting device 111 by the spring force of the power supply terminals 112 and 113.

  Next, the drive power supply 115, the electric field generation power supply 116, the inflow ammeter 117, the environment detection unit 118, and the control unit 119 for driving and controlling the electron-emitting device 111 will be described.

  As shown in FIG. 2, the drive power supply 115 is connected to the substrate 121 of the electron-emitting device 111 and is connected to the surface electrode 123 of the electron-emitting device 111 via the power supply terminals 112 and 113. A driving voltage Vd such as a direct current, a pulse waveform, a sine waveform, or a triangular waveform is applied between the first and second electrodes. In the first embodiment, a driving voltage Vd of a DC voltage is applied.

  In the electron emitter 111, when a driving voltage Vd is applied between the substrate 121 and the surface electrode 123, electrons are accelerated in the inorganic insulator layer 122, and the accelerated electrons are applied to the surface electrode 123 or the surface electrode 123. It is emitted into the atmosphere as emitted electrons from the vicinity.

  The electric field generating power source 116 is connected to the surface electrode 123 via the power supply terminals 112 and 113, and applies a predetermined electric field generating voltage Ve between the surface electrode 123 and the grounding point. The electric field generating voltage Ve generates an electric field that attracts electrons emitted from the surface electrode 123 to the surface of the photosensitive drum 15. The separation distance between the surface of the photosensitive drum 15 and the surface electrode 123 is not particularly limited as long as the electrons emitted from the surface electrode 123 can reach the surface of the photosensitive drum 15. In the first embodiment, the separation distance is set to 1 mm.

  Further, the inflow ammeter 117 is inserted between the drive power supply 115 and the substrate 121, measures the in-element current amount Ip flowing into the electron-emitting device 111, and uses the measured in-element current amount Ip as the control unit 119. Notify 2 indicates the direction of the current flow, and is opposite to the direction of the electron flow.

  The environment detection unit 118 is fixed to the upper surface of the pedestal 114, measures the temperature T and humidity H around the electron-emitting device 111, and notifies the control unit 119 of the measured temperature T and humidity H.

  Then, the control unit 119 emits the electron emission element 111 based on the in-element current amount Ip measured by the inflow ammeter 117 and the temperature T and humidity H around the electron emission element 111 measured by the environment detection unit 118. An estimated value MIe of the emission current amount Ie corresponding to the amount of emitted electrons (electron emission amount) is obtained, and the drive voltage of the drive power supply 115 is set so that the estimated value MIe becomes a preset target value AIe of the emission current amount Ie. Vd is controlled.

  Here, a specific procedure for obtaining the estimated value MIe will be described in detail in the following experimental example 1, but is generally as follows. First, as a premise, since the electron emission efficiency η of the electron emission element 111 changes corresponding to the temperature T and humidity H around the electron emission element 111, the electron emission efficiency η corresponding to the temperature T and humidity H is measured in advance. Thus, a data table Dt as shown in FIG. 4 is created and stored in a memory (not shown) built in the control unit 119. The data table Dt stores values of electron emission efficiency η corresponding to the low temperature and low humidity environment LL, the normal temperature and normal humidity environment NN, and the high temperature and high humidity environment HH. Then, the control unit 119 determines whether the temperature T and the humidity H around the electron-emitting device 111 measured by the environment detection unit 118 correspond to each of the environments LL, NN, and HH, or is closest to the data. Referring to the table Dt, the electron emission efficiency η corresponding to the determined environment is retrieved and obtained, and the amount of emission current is calculated based on the retrieved electron emission efficiency η and the in-element current amount Ip measured by the inflow ammeter 117. An estimated value MIe of Ie (electron emission amount) is calculated and obtained. The estimated value MIe of the emission current amount Ie can be obtained from the following equation (3) because the emission current amount Ie is in the relationship shown in the above equation (1).

MIe = η × Ip (3)
Thus, the estimated value MIe of the emission current amount Ie (electron emission amount) of the electron emission element 111 can be obtained based on the in-element current amount Ip of the electron emission element 111 and the temperature T and humidity H around the electron emission element 111. . Since the estimated value MIe of the emission current amount Ie is obtained based on the in-element current amount Ip, the temperature T, and the humidity H with a small measurement error, the accuracy as an approximate value of the emission current amount Ie is high. Therefore, by controlling the drive voltage Vd of the drive power supply 115 so that the estimated value MIe becomes the target value AIe of the emission current amount Ie, the actual emission current amount Ie can be controlled in real time with high accuracy. It becomes possible to appropriately control the charge amount and the charge potential on the surface of the body drum 15.

On the other hand, in the conventional electron emission device 201 of FIG. 9, the difference between the in-element current amount Ip measured by the inflow ammeter 216 and the recovered current amount Ic measured by the recovered ammeter 217 is taken as the emission current amount Ie. However, since Ip≈Ic, an accurate emission current amount Ie cannot be obtained, and the charge amount and charge potential on the surface of the photosensitive drum 221 cannot be accurately controlled.
<Experimental Example 1 According to First Embodiment>
Next, in Experimental Example 1, the element current amount Ip measured by the inflow ammeter 117, the temperature T and humidity H around the electron emitter 111 measured by the environment detector 118, and the emission of the electron emitter 111 The relationship between the current amount Ie and the estimated value MIe is clarified.

  First, the present inventors have examined the relationship between the drive voltage Vd and the electron emission efficiency η based on an aging test under three environments of a low temperature and low humidity environment LL, a normal temperature and normal humidity environment NN, and a high temperature and high humidity environment HH. It was. Specifically, the three environmental conditions are as follows.

Low temperature and low humidity environment LL: 5 ° C, 15%
Normal temperature and humidity environment NN: 25 ° C, 50%
High temperature and high humidity environment HH: 30 ° C, 80%
The target lifetime limit of the electron-emitting device 111 in the first embodiment is that the surface of the photosensitive drum 15 is charged until the electrophotographic process unit 11 processes at least 60,000 (60K) recording sheets. The quantity and the charging potential can be set repeatedly and accurately.

  Therefore, in any of the low temperature and low humidity environment LL, the normal temperature and normal humidity environment NN, and the high temperature and high humidity environment HH, the electron emission efficiency η with respect to the driving voltage Vd when the number of recording sheets processed by the electrophotographic process unit 11 is zero. Characteristics, the characteristics of the electron emission efficiency η with respect to the driving voltage Vd when the number of processed recording sheets is 30K, and the characteristics of the electron emission efficiency η with respect to the driving voltage Vd when the number of processed recording sheets is 60K. .

  Further, the electron emission efficiency η can be obtained based on the above formula (1) by measuring the in-element current amount Ip and the recovered current amount Ic (shown in FIG. 9) with high accuracy. Alternatively, an experimental system in which only the charging unit 21 is provided around the photosensitive drum 15 and the other developing units 12 and the transfer unit 13 are excluded, and the surface of the photosensitive drum 15 is covered with the electron emitting element 111. A drum current amount Ipc (shown in FIG. 6) and an element current amount Ip flowing through the photosensitive drum 15 at this time are charged with a predetermined charge amount and charging potential, and the drum current amount Ipc is measured with high accuracy. Is treated as an estimated value of the emission current amount Ie, the electron emission efficiency η can be obtained based on the above equation (1).

  The result is shown in the graph of FIG. In the graph of FIG. 5, the horizontal axis represents the drive voltage Vd, and the vertical axis represents the electron emission efficiency η. Further, the group GL includes a group of measurement values obtained when the electron emission efficiency η with respect to the drive voltage Vd is measured twice for each of the 0, 30K, and 60K recording sheets processed in the low temperature and low humidity environment LL. Similarly, the group GN includes a group of measurement values obtained when the electron emission efficiency η with respect to the drive voltage Vd is measured twice for each of the 0, 30K, and 60K recording sheets processed in the room temperature and humidity environment NN. The group GH consists of a group of measurement values obtained when the electron emission efficiency η with respect to the drive voltage Vd is measured twice for each of the 0, 30K, and 60K recording sheets processed in the high-temperature and high-humidity environment HH.

  As apparent from the graph of FIG. 5, in any of the low temperature and low humidity environment LL, the normal temperature and normal humidity environment NN, and the high temperature and high humidity environment HH, the drive voltage Vd and the electron emission efficiency η are substantially proportional to each other. The effect of the number of processed sheets is hardly seen. In each of the environments LL, NN, and HH, the fluctuation range of the electron emission efficiency η with respect to the drive voltage Vd is specified. Furthermore, there is a clear difference in the value of the electron emission efficiency η with respect to the drive voltage Vd between the environments LL, NN, and HH. For this reason, if an average electron emission efficiency η is set for each environment LL, NN, and HH, the average electron emission efficiency η and the in-element current amount Ip are used to calculate the emission current amount Ie. The estimated value MIe can be obtained. The estimated value MIe of the emission current amount Ie is obtained by the above equation (3).

  Since the estimated value MIe of the emission current amount Ie is obtained based on the in-element current amount Ip, the temperature T, and the humidity H with a small measurement error, the accuracy as an approximate value of the emission current amount Ie is high. By controlling the drive voltage Vd of the drive power supply 115 so that MIe becomes the target value AIe of the emission current amount Ie, the actual emission current amount Ie can be controlled with high accuracy in real time.

  Further, it is necessary to always obtain the necessary emission current amount Ie until the target lifetime of the electron-emitting device 111 is processed, that is, until at least 60,000 (60K) recording sheets are processed by the electrophotographic process unit 11. Since the minimum drive voltage Vd can be applied to the surface electrode 123 of the electron-emitting device 111, deterioration of the surface electrode 123 can be suppressed, and at the same time, the life of the electron-emitting device 111 can be increased. The surface of the photosensitive drum 15 can be stably charged during the target life limit of the electron-emitting device 111.

In the first embodiment and Experimental Example 1, the temperature and humidity environment around the electron emitter 111 is determined and the electron emission efficiency η corresponding to this temperature and humidity environment is obtained. Alternatively, either one of humidity and humidity may be measured, and the electron emission efficiency η corresponding to the measured temperature or humidity environment may be obtained.
Second Embodiment
Next, a charging unit 21A, which is a second embodiment of the electronic discharge device of the present invention, will be described in detail with reference to FIG. The charging unit 21A of the second embodiment is provided in the vicinity of the surface of the photosensitive drum 15 in the electrophotographic process unit 11 shown in FIG. 1 instead of the charging unit 21 of the first embodiment, and the surface of the photosensitive drum 15 is uniform. To be charged.

  FIG. 6 is a diagram schematically illustrating the charging unit 21 </ b> A and the photosensitive drum 15 according to the second embodiment. In FIG. 6, the same reference numerals are given to the portions that perform the same actions as in FIGS. 2, 3 (a), and (b).

  First, in the charging unit 21A of the second embodiment, similarly to the charging unit 21 of the first embodiment shown in FIG. 2 and FIGS. 3A and 3B, the electron discharge element 111, the power supply terminals 112, 113, A pedestal 114, a drive power supply 115, an electric field generating power supply 116, an environment detection unit 118, and a control unit 119 are provided. An inflow ammeter 117 in the charging unit 21 shown in FIGS. 2 and 3A and 3B is provided. Is different from the charging unit 21 of the first embodiment in that an electric field ammeter 131 is added.

  In the charging unit 21A having such a configuration, the electron discharge element 111 includes a substrate 121 fixedly supported on the lower surface of the base 114, an inorganic insulator layer 122 formed on the substrate 121, and the inorganic insulator layer 122. It has a three-layer structure composed of the surface electrode 123 formed on the top. The surface electrode 123 includes two bus line portions 123a and 123b and a plurality of comb electrode portions 123c that connect the bus line portions 123a and 123b. Further, the power supply terminals 112 and 113 are fixed to both side surfaces of the pedestal 114, come into contact with the bus line portions 123 a and 123 b of the surface electrode 123, and the electron discharge element 111 is pressed against the pedestal 114 and fixedly supported.

  The drive power supply 115 applies a drive voltage Vd such as a direct current, a pulse waveform, a sine waveform, or a triangular waveform between the substrate 121 and the surface electrode 123 in the electron-emitting device 111. In the second embodiment, a DC voltage drive voltage Vd is applied. Thereby, electrons are accelerated by the inorganic insulator layer 122 in the electron-emitting device 111, and the accelerated electrons are emitted from the surface electrode 123 or the vicinity of the surface electrode 123 into the atmosphere as emitted electrons.

  Further, the electric field generating power supply 116 applies a predetermined electric field generating voltage Ve between the surface electrode 123 and the ground point. As a result, an electric field that attracts electrons emitted from the surface electrode 123 to the surface of the photosensitive drum 15 is generated. The separation distance between the surface of the photosensitive drum 15 and the surface electrode 123 is not particularly limited as long as the electrons emitted from the surface electrode 123 can reach the surface of the photosensitive drum 15.

  The electric field ammeter 131 is inserted between the electric field generating power source 116 and the grounding point, detects the electric field generating current amount Iea flowing from the grounded part to the electric field generating power source 116, and this electric field generating current amount Iea. Is notified to the control unit 119.

  Furthermore, the environment detection unit 118 is fixed to the upper surface of the pedestal 114, measures the temperature T and humidity H around the electron-emitting device 111, and notifies the control unit 119 of the measured temperature T and humidity H.

  Then, the control unit 119 sets the electric field generation current amount Iea measured by the electric field ammeter 131 as an estimated value of the emission current amount Ie corresponding to the amount of emitted electrons (electron emission amount) emitted from the electron-emitting device 111. Then, the drive voltage Vd of the drive power supply 115 is controlled so that the estimated value (electric field generation current amount Iea) becomes the target value AIe.

Here, the electric field generation current amount Iea will be described in detail in the following experimental example 2, but substantially matches the drum current amount Ipc flowing between the photosensitive drum 15 and the grounding point. The drum current amount Ipc is the amount of current generated when the emission current amount Ie flows through the photosensitive drum 15, and is approximately equal to the emission current amount Ie. For this reason, the electric field generation current amount Iea measured by the electric field ammeter 131 is set as an estimated value of the emission current amount Ie, and this estimation value (electric field generation current amount Iea) becomes the target value AIe of the emission current amount Ie. Further, by controlling the drive voltage Vd of the drive power supply 115, the actual emission current amount Ie can be controlled with high accuracy in real time, and the charge amount and the charge potential on the surface of the photosensitive drum 15 can be appropriately controlled. It becomes possible.
<Experimental example 2 according to the second embodiment>
Next, in Experimental Example 2, the relationship between the electric field generation current amount Iea measured by the electric field ammeter 131 and the emission current amount Ie is clarified.

  First, even if the emission current amount Ie of the electron emitter 111 cannot be directly determined, if the drum current amount Ipc flowing between the photosensitive drum 15 and the ground point is measured, the following equation (4) is obtained. As shown, the drum current amount Ipc can be treated as an estimated value of the emission current amount Ie.

Ie≈Ipc (4)
However, as is clear from FIG. 1, not only the charging unit 21 but also the developing unit 12 and the transfer unit 13 are disposed around the photosensitive drum 15. In addition to the drum current amount Ipc corresponding to Ie, various currents flow from the developing unit 12, the transfer unit 13, and the like. For this reason, even if the current flowing through the photosensitive drum 15 in the electrophotographic process unit 11 in operation is measured, the measured current cannot be regarded as the emission current amount Ie.

  Therefore, the present inventors have provided only the charging unit 21 around the photosensitive drum 15 and excluded the other developing unit 12, the transfer unit 13 and the like, and used for the experiment in which the above formula (4) is satisfied. After the system is configured, the surface of the photosensitive drum 15 is charged to a predetermined charging amount and charging potential by the electron-emitting device 111, and at this time, the drum current amount Ipc that flows through the photosensitive drum 15 and the electric field generating power source 116 flow. The electric field generation current amount Iea and the like were measured.

  As is apparent from FIG. 6, the drum current amount Ipc can be measured between the metal cylinder 15a of the photosensitive drum 15 and the grounding point. The electric field generation current amount Iea can be measured by the electric field ammeter 131.

  Further, the environment detection unit 118 measures the temperature T and the humidity H around the electron-emitting device 111, and selectively sets the low temperature and low humidity environment LL, the normal temperature and normal humidity environment NN, and the high temperature and high humidity environment HH, or is sensitive. The drum surface current (process speed) Pv of the body drum 15 was changed, and the drum current amount Ipc and the electric field generation current amount Iea in various environments and operating conditions were measured and obtained.

  The results are shown in a chart St in FIG. In the chart St of FIG. 7, for each experiment number 1 to 6, the process speed Pv, the temperature / humidity environment, and the charging potential Vs of the photosensitive drum 15 are variously set and combined, and then the drum current amount Ipc and the electric field are set. The result of measuring the generated current amount Iea is shown.

  For example, in each of Experiment Nos. 1 to 3, after setting the room temperature and humidity environment NN and setting the charging potential Vs of the photosensitive drum 15 to −600 V, the process speed Pv is 112.5 mm / sec, 165 mm / sec, The result of measuring the drum current amount Ipc and the electric field generation current amount Iea by changing to 225 mm / sec is shown. Comparison of the measurement results of each experiment number 1 to 3 shows that the drum current amount Ipc and the electric field generation current amount Iea are substantially equal even if the process speed Pv is changed.

  In each of experiment numbers 1, 4, and 5, the process speed Pv is set to 112.5 mm / sec, the charging potential Vs of the photosensitive drum 15 is set to −600 V, and the temperature and humidity environment is set to the low temperature and low humidity environment LL. The results of measuring the drum current amount Ipc and the electric field generated current amount Iea by changing to a high temperature and high humidity environment HH are shown. From the comparison of the measurement results of the experiment numbers 1, 4, and 5, it can be seen that the drum current amount Ipc and the electric field generation current amount Iea are substantially equal even when the temperature and humidity environment is changed.

  Furthermore, in each experiment number 1 and 6, the normal temperature and humidity environment NN is set, the process speed Pv is set to 112.5 mm / sec, and the charging potential Vs of the photosensitive drum 15 is changed to −600V and −800V. The results of measuring the drum current amount Ipc and the electric field generation current amount Iea are shown. By comparing the measurement results of the experiment numbers 1 and 6, it can be seen that the drum current amount Ipc and the electric field generation current amount Iea are substantially equal even if the charging potential Vs of the photosensitive drum 15 is changed.

  That is, although the process speed Pv, temperature and humidity environment, and the charging potential Vs of the photosensitive drum 15 are variously set and combined, the drum current amount Ipc and the electric field generation current amount are expressed as shown in the following equation (5). Iea is approximately equal.

Ipc ≒ Iea (5)
Therefore, the electric field generation current amount Iea can be set as an estimated value of the emission current amount Ie based on the above equations (4) and (5), and the electric field generation current amount Iea is directly measured by the electric field ammeter 131. Thus, an estimated value (electric field generation current amount Iea) approximate to the emission current amount Ie can be obtained with high accuracy, and this estimation value (electric field generation current amount Iea) becomes the target value AIe of the emission current amount Ie. By controlling the drive voltage Vd of the drive power supply 115 as described above, the actual emission current amount Ie can be controlled with high accuracy in real time.

Although the environment detection unit 118 is used in Experimental Example 2, the environment detection unit 118 can be omitted in the second embodiment because the environment detection unit 118 is not required.
<Third Embodiment>
Next, a charging unit 21B, which is a third embodiment of the electronic discharge device of the present invention, will be described in detail with reference to FIG. The charging unit 21B of the third embodiment is provided in the vicinity of the surface of the photosensitive drum 15 in the electrophotographic process unit 11 shown in FIG. 1 instead of the charging unit 21 of the first embodiment, and the surface of the photosensitive drum 15 is uniform. To be charged.

  FIG. 8 is a diagram schematically illustrating the charging unit 21 </ b> B and the photosensitive drum 15 of the third embodiment. In FIG. 8, the same reference numerals are given to portions that perform the same functions as those in FIGS. 2, 3 (a), 3 (b), and 6.

  In the charging unit 21B of the third embodiment, similarly to the charging unit 21 shown in FIGS. 2 and 3A and 3B, the electron discharge element 111, the power supply terminals 112 and 113, the pedestal 114, and the drive power supply 115 are used. Further, an electric field generating power source 116, an inflow ammeter 117, an environment detecting unit 118, and a control unit 119 are provided, and an electric field ammeter 131 shown in FIG. 6 is also provided.

  In the third embodiment, when the environment around the electron-emitting device 111 is a low-temperature and low-humidity environment LL or a normal temperature and normal-humidity environment NN, as shown in the graph of FIG. Since it is remarkably small, the electron emission efficiency η corresponding to the low temperature and low humidity environment LL or the normal temperature and normal humidity environment NN is obtained as in the first embodiment, and the estimated value MIe of the emission current amount Ie is obtained based on the above equation (3). ing. Thereby, an accurate estimated value MIe of the emission current amount Ie can be obtained, and the drive voltage Vd of the drive power supply 115 is set so that the estimated value MIe of the emission current amount Ie becomes the target value AIe of the emission current amount Ie. By controlling, the actual emission current amount Ie can be controlled with high accuracy.

  Further, when the environment around the electron-emitting device 111 is a high-temperature and high-humidity environment HH, the fluctuation range of the electron-emitting efficiency η with respect to the drive voltage Vd slightly increases as is apparent from the graph of FIG. Rather than obtaining the estimated value MIe of the emission current amount Ie as in the embodiment, the electric field generation current amount Iea measured by the field ammeter 131 is set as the estimated value of the emission current amount Ie as in the second embodiment. preferable. Then, the actual emission current amount Ie is controlled with high accuracy by controlling the drive voltage Vd of the drive power supply 115 so that the estimated value (electric field generation current amount Iea) becomes the target value AIe of the emission current amount Ie. Yes.

  Specifically, the control unit 119 refers to the data table Dt shown in FIG. 4, and the temperature T and humidity H around the electron-emitting device 111 measured by the environment detection unit 118 are the values of the environments LL, NN, and HH. If it corresponds to the low temperature / humidity environment LL or the normal temperature / humidity environment NN, the electron emission efficiency η corresponding to the determined environment is determined. Is retrieved from the data table Dt, the electron emission efficiency η and the in-element current amount Ip measured by the inflow ammeter 117 are substituted into the above equation (3), and the estimated value MIe of the emitted current amount Ie is substituted. And the drive voltage Vd of the drive power supply 115 is controlled so that the estimated value MIe becomes the target value AIe of the emission current amount Ie.

  Further, if the determined environment is a high temperature and high humidity environment HH, the control unit 119 sets the electric field generation current amount Iea measured by the electric field ammeter 131 as an estimated value of the emission current amount Ie, and this estimated value ( The drive voltage Vd of the drive power supply 115 is controlled so that the electric field generation current amount Iea) becomes the target value AIe of the emission current amount Ie.

  By properly using the method of calculating the estimated value of the emission current amount Ie, the actual emission current amount Ie can be accurately measured in real time by effectively suppressing the influence of environmental changes and noise that causes current measurement errors. Therefore, it is possible to appropriately control the charge amount and the charge potential on the surface of the photosensitive drum 15.

  In each of the above embodiments, the charging unit of the monochrome image forming apparatus is illustrated. However, the electronic discharge device of the present invention can also be applied as a charging unit in a color image forming apparatus. The electron discharge device of the present invention is applied not only to charge the surface of the photosensitive drum, but also to charge other types of electron emission objects or discharge electrons to the space. be able to.

  As mentioned above, although preferred embodiment and modification of this invention were described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. It is understood.

DESCRIPTION OF SYMBOLS 1 Image forming system 2 Image forming apparatus 10 Photosensitive drum (electron emission target)
DESCRIPTION OF SYMBOLS 11 Electrophotographic process part 12 Developing unit 13 Transfer unit 14 Cleaning unit 21, 21A, 21B Charging unit (charging device)
22 Optical scanning unit 23 Fixing device 111 Electron emitting elements 112 and 113 Feeding terminal 114 Base 115 Drive power supply 116 Electric field generating power supply 117 Inflow ammeter (in-element current detection unit)
118 Environment Detection Unit 119 Control Unit 121 Substrate (First Electrode)
122 Inorganic insulator layer (intermediate layer)
123 Surface electrode (second electrode)
131 Field ammeter (field current detector)

Claims (10)

A drive voltage is applied between the first electrode, the second electrode, and an electron-emitting device having an intermediate layer provided between the first electrode and the second electrode, and the first electrode and the second electrode. An electron emission device including a drive power source for applying and emitting electrons from the electron emission element;
An in-element current detector for detecting an in-element current flowing through the electron-emitting device;
An environment detector for detecting the temperature or humidity of the environment in which the electron-emitting device is placed;
An electron emission apparatus comprising: a control unit that controls a drive voltage of the drive power source based on an in-element current detected by the in-element current detection unit and a temperature or humidity detected by the environment detection unit. . The electron emission device according to claim 1,
The controller is configured to estimate an electron emission amount or an emission current amount emitted from the electron-emitting device based on an in-element current detected by the in-element current detection unit and a temperature or humidity detected by the environment detection unit. And the drive voltage of the drive power supply is controlled so that the estimated value becomes a preset target value of the electron emission amount or the emission current amount. The electron-emitting device according to claim 1 or 2,
The control unit continuously maintains the target value at a constant value within a service life limit of the electron emission device. A drive voltage is applied between the first electrode, the second electrode, and an electron-emitting device having an intermediate layer provided between the first electrode and the second electrode, and the first electrode and the second electrode. And applying an electric field generating voltage between a driving power source for emitting electrons from the electron-emitting device, and the second electrode and an electron-emitting target facing the second electrode, so that the electrons are An electron emission device comprising an electric field generating power source for generating an electric field to be moved from two electrodes to the electron emission target,
An electric field current detector for detecting a current flowing from the electric field generating power source to the second electrode;
An electron emission apparatus comprising: a control unit that controls a drive voltage of the drive power source based on a current detected by the electric field current detection unit. The electron emission device according to claim 4,
The control unit sets the current detected by the electric field current detection unit as an estimated value of an electron emission amount or an emission current amount emitted from the electron-emitting device, and the estimated value is the electron emission amount or the emission current. An electron-emitting device characterized in that the drive voltage of the drive power supply is controlled to be a preset target value of the amount. The electron-emitting device according to claim 4 or 5,
The control unit continuously maintains the target value at a constant value within a service life limit of the electron emission device.   A charging device comprising the electron-emitting device according to claim 1.   An electrophotographic image forming apparatus comprising the charging device according to claim 7. In order to emit electrons from an electron-emitting device having a first electrode, a second electrode, and an intermediate layer provided between the first electrode and the second electrode, the first electrode, the second electrode, A method for controlling an electron emission device that applies a driving voltage between
Detecting an internal current flowing through the electron-emitting device;
Detecting the temperature or humidity of the environment in which the electron-emitting device is placed;
A control method for an electron-emitting device, wherein a drive voltage of the drive power supply is controlled based on the detected in-element current and the detected temperature or humidity. In order to emit electrons from an electron-emitting device having a first electrode, a second electrode, and an intermediate layer provided between the first electrode and the second electrode, the first electrode, the second electrode, A driving voltage is applied between the second electrode and the electron emission object to generate an electric field that moves the electrons from the second electrode to the electron emission object facing the second electrode. A control method of an electron emission device for applying an electric field generating voltage between
Detecting a current flowing from the electric field generating power source to the second electrode;
A control method for an electron-emitting device, wherein a drive voltage of the drive power supply is controlled based on the detected current.

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