JP2013195901A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of detecting photoreceptor characteristics with high accuracy.SOLUTION: An image forming device includes: a photoreceptor 1; charging means 2 which charges a surface of the photoreceptor; exposure means 3 which exposes the surface of the photoreceptor charged by the charging means, and forms a latent image; spot light irradiation means 12 which irradiates the latent image on the surface of the photoreceptor and its surroundings with spot light; induction current detection means 11 which detects a change in a surface charge amount caused by optical attenuation of the photoreceptor by being irradiated with the spot light as induction current; and latent image measurement means 10 which measures the latent image formed on the surface of the photoreceptor on the basis of a detection result of the induction current detection means. The latent image measurement means irradiates a plurality of measurement positions on the surface of the photoreceptor with spot light by means of the spot light irradiation means simultaneously or substantially simultaneously, and the induction current detection means detects the induction current at the plurality of measurement positions.

Description

  The present invention relates to an image forming apparatus such as a printer, a facsimile machine, and a copying machine.

  Conventionally, image degradation of dot images and line images has occurred as image blur due to fluctuations in the characteristics of the photoconductor over time and in the environment. Therefore, it is required to accurately detect the characteristics of the photoconductor from the shape of the dot latent image or line latent image by measuring the dot latent image or line latent image formed on the surface of the photoconductor in the image forming apparatus. Yes.

  The shape of the latent image formed on the surface of the photoconductor can be expressed by the potential of the surface of the photoconductor. As a method for measuring the latent image, an induced current method using light attenuation is known (for example, Patent Document 1 and Non-patent document 1).

  In this induced current method, the surface of a rotating photoconductor is charged by a charging device, and the charged photoconductor surface is exposed and scanned once in the axial direction of the photoconductor by an exposure device to write a line latent image. Then, a spot light irradiation region irradiated with a spot light irradiation device from the back surface of the transparent electrode installed in the vicinity of the surface of the photosensitive member is irradiated with a spot light irradiation region having an irradiation width smaller than the width of the line latent image in the rotation direction of the photosensitive member. When the line latent image arrives with the rotation of the body, charging and rotation of the photosensitive member are stopped. Further, in order to know the potentials at a plurality of locations in the photosensitive drum rotation direction of the line latent image, a plurality of measurement positions obtained by dividing the line latent image in the photosensitive drum rotation direction are set on the same straight line in the photosensitive drum rotation direction. . After stopping the charging and rotation of the photoconductor as described above, spot light is irradiated from the spot light irradiation device to the measurement position located on the most downstream side in the rotation direction of the photoconductor among the plurality of measurement positions. A surface potential change is caused in the minute region due to the attenuation. Then, a change in the amount of charge induced in the transparent electrode by this surface potential change, that is, an induced current is detected.

  Next, after rotating the photosensitive member by a predetermined pitch, the rotation of the photosensitive member is stopped, and the induced current induced in the transparent electrode is detected by irradiating spot light to the next measurement position. Such measurement is repeated until the measurement is performed at all the measurement positions of the line latent image in the photoconductor rotation direction. From the detected amount of induced current, the potential of the surface of the photoconductor before spot light irradiation at the measurement position can be determined, and the shape of the line latent image in the direction of rotation of the photoconductor is determined by the potential distribution at each measurement position on the surface of the photoconductor. can do.

  In this way, by grasping the shape of the latent image, if the shape of the latent image is blurred due to fluctuations in the photoreceptor characteristics, the desired image can be formed by changing the image forming process conditions, The deterioration of the image can be suppressed by exchanging the body.

  However, the rotation and stop of the photoconductor is repeated, and the induced current at each measurement position is detected while sequentially changing the measurement position in the photoconductor rotation direction. It takes time to finish the measurement at the measurement position. Therefore, under the influence of the dark decay of the charged potential on the surface of the photoconductor, the amount of induced current decreases toward the later measurement position, and the latent image is measured shallower than actual. Therefore, the measured latent image is measured as a latent image that is more blurred than the actual latent image, and there is a problem that the photoconductor characteristics cannot be accurately detected based on the measurement result of the latent image.

  The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus capable of accurately detecting the characteristics of a photoreceptor.

  In order to achieve the above object, the invention of claim 1 includes a photoconductor that is rotatably provided, a charging unit that charges the surface of the photoconductor, and a surface of the photoconductor that is charged by the charging unit. Exposing means for forming a latent image by exposing the surface of the photosensitive member, spot light irradiating means for irradiating the surface of the photosensitive member with spot light in an irradiation range smaller than the latent image formed by the exposure means, and the spot light is irradiated In this way, there is induced current detection means for detecting a change in the surface charge amount due to light attenuation of the photoconductor as an induced current, and a latent image formed on the surface of the photoconductor based on the detection result of the induced current detection means. In the image forming apparatus including a latent image measuring unit for measuring an image, the latent image measuring unit is configured to simultaneously or substantially simultaneously apply the spot light irradiation unit to the latent image and a plurality of measurement positions set in the vicinity thereof. Therefore irradiating the spot light, it is characterized in detecting the induced current measurement position of the plurality of by the induced current detector.

  In the present invention, the induced light is detected by the induced current detecting means by irradiating the spot light from the spot light irradiating means simultaneously or substantially simultaneously to the latent image on the surface of the photosensitive member and a plurality of measurement positions set in the periphery thereof . As a result, it is possible to shorten the time until measurement is completed at all measurement positions, compared with the case where measurement is performed by sequentially changing the measurement positions, so the amount of induced current is reduced due to the effect of dark decay of the charged potential on the surface of the photoconductor. Can be suppressed. Therefore, it is possible to prevent the latent image from being measured to be shallower than the actual measurement based on the detection result of the induced current detection means, and to detect the latent image based on the measurement result of the latent image, rather than performing measurement by sequentially changing the measurement position. Body characteristics can be detected with high accuracy.

  As described above, according to the present invention, there is an excellent effect that the characteristics of the photoconductor can be detected with high accuracy.

The figure which shows the example of arrangement | positioning of the electrode with respect to a photoreceptor. 1 is a schematic configuration diagram of a main part of an image forming apparatus according to an embodiment. Explanatory drawing of a latent image measuring device. The graph which shows latent image charge density distribution. The graph which shows latent image charge density distribution. 1 is a schematic configuration diagram of a main part of a multicolor image forming apparatus. The figure which shows the example of arrangement | positioning of the electrode with respect to a photoreceptor. FIG. 9 is a schematic configuration diagram of a main part of an image forming apparatus according to a third embodiment. The flowchart concerning control of latent image measurement. The graph which shows the example of a photoreceptor light attenuation characteristic.

  Embodiments in which the present invention is applied to an image forming apparatus will be described below. FIG. 2 is a schematic configuration diagram of a main part of the image forming apparatus according to the present embodiment.

[Example 1]
A photoconductor 1 that is a drum-shaped image carrier is provided to be rotatable in the direction of arrow C in the drawing. At this time, the surface of the photoconductor 1 is charged by the charging device 2 to a predetermined polarity, in this embodiment, a negative polarity. The charged photoreceptor surface is exposed based on image information by the exposure device 3, and an electrostatic latent image is formed on the photoreceptor 1. The electrostatic latent image is visualized as a toner image by the developing device 4. The toner image on the photosensitive member 1 is transferred to the transfer material P fed in the direction of arrow X in the drawing by a function of the transfer device 5 from a paper supply device (not shown). The transfer material P onto which the toner image has been transferred passes through the fixing device 6 and is fixed to the transfer material P by heat and pressure. Further, after the toner image is transferred from the photosensitive member 1 to the transfer material P, the transfer residual toner remaining on the surface of the photosensitive member is removed by the cleaning device 7. The surface of the photosensitive member 1 cleaned by the cleaning device 7 is irradiated with the neutralizing light from the neutralizing lamp 8 which is a neutralizing device, and the surface potential of the photosensitive member 1 is initialized.

  In the example of the image forming apparatus shown in FIG. 2, the toner image formed on the photosensitive member 1 is directly transferred to the final transfer material P. However, the toner image on the photosensitive member 1 is transferred. It is also possible to transfer to a transfer material made of an intermediate transfer member and transfer the toner image on the intermediate transfer member to the final transfer material.

  A latent image measuring device 10 is disposed between the exposure device 3 and the developing device 4. As will be described later, the latent image measuring device 10 includes a transparent electrode disposed at a predetermined distance from the photoconductor 1, a laser beam optical system, and a measuring unit that measures an induced current. The laser beam optical system may include a semiconductor laser (LD), or a light emitting diode (LED) may be used instead of the laser beam.

  The latent image measurement by the latent image measuring device 10 is not performed at the time of normal image formation, but when the image forming apparatus is controlled at the time of start-up, after a certain number of images are formed, or after a certain time has elapsed, for example, the image forming process conditions are changed. This should be done at the time of process control execution.

  During the latent image measurement, the surface of the photoreceptor 1 is exposed by the exposure device 3 to form a predetermined test latent image pattern (line latent image or dot latent image). Then, when the part on the photosensitive member 1 corresponding to the position where the detection light is irradiated comes immediately before the signal detection unit, charging of the photosensitive member surface by the charging device 2 and rotation of the photosensitive member 1 are stopped, and latent image measurement is performed. The detection light is emitted from the device 10, the amount of the induced current generated is detected, and the latent image is measured.

  Thus, by providing the latent image measuring device 10 in the image forming apparatus and measuring the latent image, it is possible to accurately detect the characteristics of the photoconductor that has changed over time or in the environment, and in accordance with the image forming process condition accordingly. High quality image formation can be performed by performing control to change the.

  The photoconductor characteristics information includes photoconductor film thickness, surface characteristics (friction coefficient, unevenness), surface potential (before and after each process), surface energy, scattered light, temperature, color, surface position (flare), line Speed, potential decay speed, resistance / capacitance, surface moisture content, and the like.

The latent image measuring device 10 will be described with reference to FIG.
The latent image measuring device 10 includes a transparent electrode 11, a laser beam optical system 12 that emits detection light, a measuring unit 13 that measures an induced current, and the like.

  The transparent electrode 11 is formed by forming a transparent conductive thin film on transparent glass, and is capable of irradiating laser light from the back surface of the electrode toward the photoreceptor 1. The transparent glass preferably has a wide transmission wavelength range such as quartz glass, and the transparent conductive thin film is generally ITO (indium tin oxide), but there is no problem in addition to these.

  The transparent conductive thin film may be formed on the entire surface of one side of the transparent glass, or may be formed in a mesh shape with a fine line (≦ 1 [mm]) using a pattern mask.

  In this case, if the area ratio of [area of ITO film forming portion / area of non-ITO film forming portion] is about 0.2, the light passing through the transparent electrode 11 has a wavelength of 800 [nm] or more. When this is included, light of this wavelength can be passed through without significant loss.

  Moreover, when the light to pass is a laser, it is preferable to attach an antireflection film to the glass surface of the transparent glass on the laser incident side. This is to prevent so-called return light noise, in which the laser beam reflected by the glass surface on the laser incident side returns to the light emitting part to form a composite resonator and the laser light fluctuates.

  Next, the laser beam optical system 12 that irradiates the detection light will be described. It is desirable to use a laser light source having a wavelength having the sensitivity of the photosensitive member 1 as the light source that is the detection light irradiation means to be used. The LD driver 14 is a laser light source including the laser beam optical system 12 and a driving device thereof, and laser light irradiation is performed by adjusting LD power and lighting time. Further, the LD drive current is controlled from the PC controller 15 through the pulse generator 16. The exposure energy given to the photosensitive member 1 by the laser light source is adjusted to the saturation potential (for example, −100 [V]) that attenuates the predetermined charging potential (for example, −800 [V]) most by adjusting the LD power and the lighting time. The exposure energy is required to be about the same level as the above.

  The LD power is preferably determined by adjusting the laser drive current, and the laser lighting time is preferably set to be less than this with reference to the carrier transit time of the photoreceptor 1. This is because the measured signal intensity is the flow of charge density induced in the electrode, and the shorter the time, the greater the signal.

Also, the beam spot diameter of the LD (assuming that the laser beam is usually a Gaussian-distributed beam, the range position (diameter) where the intensity is 1 / e ² (about 13.5 [%]) of the maximum intensity) is the detection light. It is desirable that the signal intensity (inductive current) is large enough to be measured. Further, as disclosed in Patent Document 1, it is also desirable to use a line LD or the like that improves the S / N ratio of the detection signal by increasing the size in the main scanning direction.

  Using these laser beam optical systems 12, when the measurement latent image on the photosensitive member 1 reaches a desired position, the detection light is turned on to measure the induced current. The measuring unit 13 that measures the induced current includes a current amplifier 18 that amplifies the current and an oscilloscope 17 that outputs a signal. The PC controller 15 controls the laser beam optical system 12 that irradiates the detection light, the measurement unit 13 that measures the induced current, and the drive rotation controller 19 that drives the photosensitive member 1.

  FIG. 1 shows an arrangement example of the transparent electrode 11 with respect to the photoreceptor 1. In FIG. 1, a plurality of transparent electrodes 11 are arranged in the photoconductor axial direction.

  For example, when measuring the line latent image 30 extending in the main scanning direction which is the photosensitive member axial direction, the plurality of transparent electrodes 11 are in the main scanning direction and in the direction orthogonal to the main scanning direction and the photosensitive member rotation direction. Arranged in the sub-scanning direction. When the width of the line latent image 30 in the sub-scanning direction is 100 [μm], the transparent electrodes 11a, 11b, 11c, 11d, 11e, and 11f are arranged so as to be shifted by a distance A in the sub-scanning direction. Here, the distance A is set to 50 [μm], and each transparent electrode 11 measures an image portion in which the line latent image 30 is formed on the photoreceptor 1 and a non-image portion in which the line latent image 30 is not formed. I can do it.

  Each transparent electrode 11 is arranged with a gap of about 0.1 [mm] with respect to the surface of the photoreceptor 1. At this time, it is desirable to perform gap control using a gap adjusting roller 20 (see FIG. 3) or the like.

  The distance B shifted in the main scanning direction between the adjacent transparent electrodes 11 is preferably equal to or smaller than the gap between the surface of the photoreceptor 1 and the transparent electrode 11 described above. And the non-image portion can be measured.

  When measuring the line latent image 30 extending in the main scanning direction with a width of 100 [μm] in the sub-scanning direction, the adjacent transparent electrodes 11 are separated by several tens [μm] to 100 [μm] in the sub-scanning direction. It is desirable to arrange. In FIG. 1, six transparent electrodes 11 are disposed on the photoreceptor 1, but the number of the transparent electrodes 11 is not limited thereto. The distance in the main scanning direction between the adjacent transparent electrodes 11 is preferably set to a distance of several [mm] to several tens [mm] so as not to affect the measurement of the induced current by each transparent electrode 11.

Next, the latent image measurement procedure in the present embodiment will be specifically described.
First, the photosensitive member 1 is rotated, the surface of the photosensitive member is charged by the charging device 2, and the latent image is written on the surface of the photosensitive member by the exposure device 3. The latent image is preferably a line latent image in the main scanning direction in which an induced current at the time of detection light irradiation can be easily measured. However, the latent image is not limited to this, and may be a dot latent image. Here, a line latent image extending in the main scanning direction is formed as a latent image, the width of the line latent image in the sub-scanning direction is a 2-dot line, and the line width is about 100 [μm].

  Next, when a predetermined part on the photosensitive member 1 on which the line latent image is formed reaches the signal detection unit, the charging by the charging device 2 and the rotation of the photosensitive member 1 are stopped, and each position is set as shown in FIG. The detection light is simultaneously irradiated from the installed transparent electrodes 11. The detection light is irradiated by using an arbitrary waveform generator to generate a one shot pulse, which is used as a trigger.

  Simultaneous irradiation refers to irradiation within a short period of time until the detection light is irradiated and carriers are generated and moved inside the photoconductor to change the electric field inside the photoconductor. Of the positive and negative carriers generated in the carrier generating layer, the internal electric field is affected by positive carriers in the process of moving positive carriers in the carrier moving layer toward the surface of the photoreceptor according to the electric field. Therefore, the simultaneous irradiation may be performed within the time during which positive carriers pass through the carrier generation layer. Although this time depends on the type of the photoreceptor 1, it is about several [μs] to several tens [μs].

  The induced current (displacement current) due to the potential decay (= charge change) generated at this time is measured. The measurement is performed in consideration of the transit time until the generated carrier due to the detection light moves. The transit time at −800 [V] is about 300 [μs]. For the control of the position in the main scanning direction, only the lighting start time is controlled using scanning using a polygon mirror or the like. Further, when the photosensitive member rotates, the static elimination lamp 8 is turned on to remove the charge on the photosensitive member surface. Next, the measurement examples performed in this study are shown below.

Photoconductor: laminated OPC (organic optical semiconductor) drum, 60 [mm] φ × 334 [mm] long ・ Charging potential: −800 [V]
Writing laser beam diameter (1 / e ² diameter): 50 [μm] × 60 [μm]

<Detection light conditions>
Laser beam diameter (1 / e ² diameter): 655 [nm] line laser beam in main scanning direction 24 [μm] × sub-scanning direction 3 [mm] Exposure energy: 0.3 [μJ / cm ² ] ( (Required exposure energy for changing the photosensitive member charging potential from −800 [V] to −100 [V])
・ Laser trigger: Arbitrary waveform generator (Agilent Technology HP33120A) is used ・ Lighting pulse width: 2 [μs]
・ Detection light irradiation position: Measured at six locations at a pitch of about 50 [μm] in the sub-scanning direction from a non-image portion position of about 150 [μm] from the top of the latent image

  As for the induced current, when the surface of the photosensitive member 1 is charged, the induced current corresponding to the charged charge amount is measured. The induced current is smaller in the image portion because the amount of charge on the photoconductor 1 is reduced in the image portion than in the non-image portion where a lot of electric charge is on the photoconductor 1. The induced current can be converted into an induced charge amount by multiplying the time when the current is measured.

  With reference to FIG. 4, each induced charge amount measured by the conventional method and the present method will be described in association with the latent image profile (charge amount distribution) predicted by the simulation.

  The thin line shown in FIG. 4 is the charge density distribution of the latent image calculated by simulation. The simulation used here uses the technique of applying the successive approximation method to the difference method based on the complete implicit method for the process from charge carrier generation to transport focusing on laser exposure in Non-Patent Document 2. A thin line is a charge density distribution of a predicted latent image on a normal photoreceptor 1.

Also, in FIG. 4, the induced charge amount by the latent image measuring method in which the conventional detection light irradiation and induced current measurement are repeated is indicated by white circles, and the induced charge amount by the latent image measuring method of the present embodiment is indicated by black circles. Yes. In the conventional method of sequential measurement, the amount of induced charge is reduced due to the influence of the previously lit detection light, and the amount of induced charge in the non-image area is −600 [μC / m ² ], In the latent image measuring method of this embodiment, the measured current amount is increased by about −750 [μC / m ² ] and 15 [%]. From this, it was confirmed that an induced charge amount equivalent to the charge amount of the non-image part by simulation could be measured. Thus, although the latent image shape is broadly measured in the conventional measurement method, the latent image measurement method of the present embodiment enables accurate latent image measurement. The same applies to the deteriorated photoreceptor 1.

Next, FIG. 5 shows a simulation result and measurement example of the deteriorated photoreceptor latent image.
In FIG. 5, the measurement latent image of the normal photoconductor 1 by simulation is indicated by a thin line, and the deteriorated latent image is indicated by a dotted line. In addition, the measurement result shows the case of the normal photoconductor 1 with a black circle, and the case of the deteriorated photoconductor 1 with a black triangle. As can be seen from FIG. 5, the distribution of the deteriorated latent image is broader than that of the normal measured latent image of the photoreceptor 1, and it can be measured that the latent image is deteriorated.

  In contrast, the conventional latent image measurement method takes several seconds to several tens of seconds, whereas the latent image measurement method of this embodiment requires only one measurement, so there is no time loss. It is not affected by dark decay or the like in which the electric charge is attenuated.

  Further, in this embodiment, the detection light irradiation position is a photosensitive body from a non-image portion at a position about 150 [μm] away from the upper end in the sub scanning direction of the line latent image as a measurement latent image on the upstream side in the rotational direction of the photosensitive body. Measurement is performed with six transparent electrodes 11 at a pitch of 50 [μm] on the downstream side in the rotation direction, but the number of measurements and the interval are not limited to this.

  In the present embodiment, the measurement of the line latent image extending in the main scanning direction has been described. However, the present invention can also be applied to the case of measuring a line latent image extending in the sub scanning direction or a dot latent image. .

  In the present embodiment, the line laser beam has been described as the detection light. However, it is also possible to use a laser beam having the same laser beam diameter in the main scanning direction and the sub-scanning direction. Moreover, it is also possible to use a plurality of LEDs arranged at electrode positions instead of the laser beam as the detection light.

  Further, in this embodiment, the ratio of the induced charge amount between the image portion and the non-image portion on the photosensitive member 1 is compared, so that the latent image is not detected as a deteriorated latent image even when the charged potential is lowered by process control. The amount of change in the shape of the image can be predicted.

  Further, the latent image measuring method of this embodiment can be developed to a color image forming apparatus in which a plurality of photosensitive members 1 and their peripheral devices are arranged.

  FIG. 6 shows a schematic configuration of a main part of the color image forming apparatus. In the drawing, “Y” indicates yellow, “M” indicates magenta, “C” indicates cyan, and “K” indicates black.

  In FIG. 6, the photoconductors 1Y, 1M, 1C, and 1K rotate in the clockwise direction in the drawing. The charging devices 2Y, 2M, 2C, and 2K, the developing devices 4Y, 4M, 4C, and 4K, the transfer devices 5Y, 5M, 5C, and 5K, and the cleaning devices 7Y, 7M, 7C, and 7K in the rotation order are the photoreceptors 1Y, It is arranged around 1M, 1C, 1K.

  The exposure device 3 irradiates the photosensitive member surface between the charging devices 2Y, 2M, 2C, and 2K and the developing devices 4Y, 4M, 4C, and 4K with a beam, and latent images are formed on the photosensitive members 1Y, 1M, 1C, and 1K. It is supposed to be formed. Then, toner images are formed on the respective photoreceptors 1 by using the developing devices 4Y, 4M, 4C, and 4K with respect to the latent images. Further, the transfer devices 5Y, 5M, 5C, and 5K transfer the respective color sequential transfer toner images onto the transfer material P carried on the conveyance belt 40 from the photoreceptors 1Y, 1M, 1C, and 1K, and finally the fixing device. 6 fixes the image on the transfer material P.

  Further, in the rotation direction of the photoconductors 1Y, 1M, 1C, and 1K, the latent image is formed so as to face the surface of the photoconductor between the latent image writing position by the exposure device 3 and the developing devices 4Y, 4M, 4C, and 4K. Measuring devices 10Y, 10M, 10C, and 10K are arranged. Then, the states of the latent images of the photoreceptors 1Y, 1M, 1C, and 1K can be measured by the latent image measuring devices 10Y, 10M, 10C, and 10K by the measurement method of the present embodiment described above.

[Example 2]
In this embodiment, a case where a line latent image extending in the sub-scanning direction that is the photosensitive member rotation direction is measured as shown in FIG. 7 will be described. Thus, by measuring the line latent image in the sub-scanning direction, effective measurement can be performed with a small number of measurements.

  For example, when measuring a line latent image 70 of 100 [μm] in the sub-scanning direction, the transparent electrodes 11a and 11b are provided with an image portion where a line latent image is formed and a non-image portion where a line latent image is not formed. Are shifted by a distance A in the main scanning direction which is the photosensitive member axial direction. Further, the transparent electrode 11a and the transparent electrode 11b are arranged with a gap of about 0.1 [mm] with respect to the surface of the photoreceptor using a gap adjusting roller 20 (see FIG. 3) or the like. Further, the distance B shifted in the sub-scanning direction between the transparent electrode 11a and the transparent electrode 11b is spaced from several [mm] to several tens [mm] so as not to affect the measurement of each induced current measured by each other. Is desirable.

  In the present embodiment, the two transparent electrodes 11 are arranged on the photosensitive member 1, but it is possible to arrange three or more transparent electrodes 11, but at least an image portion and a non-image on the surface of the photosensitive member. Measurement is performed at two locations, one at a time, and deterioration of the photoconductor 1 is measured based on the amount of variation in the ratio of the induced charge amounts. Next, an example of measurement conditions is shown.

Photoconductor: laminated OPC (organic optical semiconductor) drum, 60 [mm] φ × 334 [mm] long ・ Charging potential: −800 [V]
Writing laser beam diameter (1 / e ² diameter): 50 [μm] × 60 [μm]

<Detection light conditions>
Laser beam diameter (1 / e ² diameter): 655 [nm] laser beam in the main scanning direction 24 [μm] × sub-scanning direction 24 [μm] Exposure energy: 0.3 [μJ / cm ² ] (photosensitive Exposure energy required to change the charged body potential from -800 [V] to -100 [V])
・ Laser trigger: Arbitrary waveform generator (Agilent Technology HP33120A) is used ・ Lighting pulse width: 2 [μs]
Detection light irradiation position: non-image portion 1 [mm] left from the irradiation position of the upper end portion in the sub-scanning direction and image portion 30 [μm] from the image end portion

As a result of measurement under such a measurement condition, the induced charge amount of the non-image portion is −750 [μC / m ² ], the induced charge amount of the image portion is −250 [μC / m ² ], and the image portion / The ratio of induced charges in the non-image area was about 1/3. On the other hand, the non-image area induced charge amount of the deteriorated photoreceptor 1 is −650 [μC / m ² ], the image area induced charge amount is −450 [μC / m ² ], and the image area / non-image area. The ratio of the induced charge amount of the part is increased to about 3/4. This means that the induced charge amount ratio in the image portion is high, that is, it can be measured that the digging is shallow and the latent image is deteriorated.

  In this embodiment, the case where the line latent image extending in the sub-scanning direction is measured has been described. However, the present invention can be applied to the case where the line latent image and the dot latent image extending in the main scanning direction are measured.

[Example 3]
FIG. 8 shows an embodiment for further improving the measurement accuracy with respect to the first embodiment and the second embodiment.
When dark decay deteriorates with the deterioration of the photoreceptor 1, the latent image spreads more after a certain amount of time, rather than measuring immediately after the latent image is written on the photoreceptor 1 by the exposure device 3. It becomes possible to measure the deterioration of the photoreceptor 1.

  For example, as shown in FIG. 8, a latent image measuring device 10 is provided opposite to the surface of the photoconductor on the downstream side of the photoconductor rotation direction from the cleaning device 7 and on the upstream side of the static discharge lamp 8 in the rotation direction of the photoconductor. It is desirable to measure the latent image. At this time, if toner adheres to the latent image, the latent image is measured shallow due to the charge of the toner. For this reason, when the latent image is measured by the latent image measuring device 10, it is desirable that the developing device 4 does not develop the latent image with toner and does not attach it. Further, it is desirable not to apply a bias in the transfer process by the transfer device 5. In addition, the latent image measurement position by the latent image measuring device 10 is not limited to before the charge removal by the charge removal lamp 8, but any position on the downstream side in the photosensitive member rotation direction from the developing device 4 and any upstream side in the photosensitive member rotation direction from the charge removal lamp 8. It is also possible to arrange at the position.

[Example 4]
The timing for performing latent image measurement will be described with reference to FIG.
An image forming apparatus controls a process that has changed over time or in the environment (process control), and forms a stable and high-quality image. In addition, what is necessary is just to use well-known various methods suitably as process control.

  An example of process control executed by the image forming apparatus of this embodiment will be described. In the image forming apparatus according to the present embodiment, process control is executed to suppress image quality fluctuations due to environmental fluctuations and temporal fluctuations. Specifically, when the process control is executed, an image of a certain toner pattern is formed on the photoconductor 1 under a condition that the development bias voltage is constant, and the image density is detected by an optical sensor (not shown), The developing ability of the developing device 4 can be grasped from the density change. The image quality can be kept constant by changing the set values of the image forming process conditions such as exposure energy, charging voltage and developing bias so that the developing ability becomes a predetermined target developing ability.

  The deterioration of the photoreceptor 1 over time and environmental fluctuations also affect the image. Therefore, in the flowchart shown in FIG. 9, the latent image measurement is performed at the same time when the process control is performed (S1). For example, when the latent image is determined and the latent image becomes blurred and shallow (Yes in S2), Feedback is provided to the control unit of the apparatus main body so as to change the image forming process conditions. As a result, the image forming process conditions are changed in accordance with changes such as deterioration of the photoreceptor 1 with time and environmental changes (S3), and high-quality image formation can be performed.

  For example, an example will be described in which the film thickness of the photoreceptor 1 decreases due to use over time, and the sensitivity of the photoreceptor 1 decreases. When the sensitivity of the photosensitive member 1 is lowered, the induced charge amount ratio of the image portion / non-image portion is increased. This is because the digging of the latent image becomes shallow because the sensitivity of the photosensitive member 1 is reduced due to the thin film as shown in FIG. In this case, it is possible to form a similar latent image profile by lowering the charged potential on the surface of the photoreceptor.

  For example, when the initial image forming process condition is a charged potential of −800 [V] and the induced charge amount ratio of the image portion / non-image portion is increased, the charged potential on the surface of the photoconductor is −700 [V]. The image forming process conditions are changed so as to lower the charging voltage so as to be V]. Further, as an image forming process condition, the same latent image profile can be formed even if the exposure energy by the exposure apparatus 3 is increased without changing the charging potential.

  Further, an example will be described in which a latent image is blurred because a substance such as a charged product adheres to the surface layer of the photoconductor 1 due to use over time or the resistance of the photoconductor 1 varies due to environmental changes. These phenomena may be caused by a decrease in the resistance of the surface layer of the photoreceptor, a charge distribution being disrupted, and a latent image becoming shallow. In this case, it is possible to form a latent image deeply by increasing the charging potential on the surface of the photoreceptor or increasing the exposure energy, and to maintain a latent image distribution that can be visualized even if the latent image slightly flows. Control such as changing the process can be considered.

  As described above, when the induced charge amount ratio of the image portion / non-image portion becomes high, the image forming process conditions are varied as described above, and the change with time and environment is controlled to provide a good image. Is possible. By repeatedly performing these feedbacks, it is possible to perform more accurate control.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
A photosensitive member such as the photosensitive member 1; a charging unit such as a charging device 2 that charges the surface of the photosensitive member; and an exposure device 3 that exposes the surface of the photosensitive member charged by the charging unit to form a latent image. Exposure means, spot light irradiation means such as a laser optical system 12 for irradiating the surface of the photosensitive member with spot light in an irradiation range smaller than the latent image formed by the exposure means, and exposure by spot light irradiation. Inductive current detection means such as a transparent electrode 11 that detects a change in surface charge amount due to light attenuation of the body as an induced current, and a latent image formed on the surface of the photoconductor based on the detection result of the induced current detection means In an image forming apparatus provided with a latent image measuring means such as a latent image measuring apparatus 10 for measuring, the latent image measuring means has a plurality of spot light irradiating means and induced current detecting means. To a plurality of measurement positions set in the sides, the spot light is irradiated by the simultaneous or substantially simultaneously each spot light irradiating means, the induced current of the plurality of measurement positions is detected at each induced current detecting means. According to this, as described in the above embodiment, it is possible to accurately detect the photoconductor characteristics.
(Aspect B)
In (Aspect A), the plurality of measurement positions include an image portion where the latent image is formed and a non-image portion where the latent image is not formed. According to this, as described in the above embodiment, it is possible to accurately detect the characteristics of the photoconductor that has changed over time or in the environment.
(Aspect C)
In (Aspect A) or (Aspect B), a line latent image such as the line latent images 30 and 70 extending in the photosensitive member axial direction or the photosensitive member rotating direction is formed on the surface of the photosensitive member by the exposure means, and the spot light The irradiating means irradiates spot light having an irradiation width smaller than the width of the line latent image, and the latent image measuring means is positioned relative to the line latent image in each of the photosensitive member axial direction and the photosensitive member rotating direction. The spot light irradiating means irradiates a plurality of measurement positions set by shifting the spot light simultaneously or substantially simultaneously, and the induced current detection means detects the induced currents at the plurality of measurement positions. According to this, as described in the above embodiment, it is easy to measure the induced current at the time of spot light irradiation.
(Aspect D)
In (Aspect A), (Aspect B) or (Aspect C), the photosensitive member is rotatably provided, and a developing device 4 for developing a latent image formed on the surface of the photosensitive member to form a toner image. A transfer unit such as a transfer device 5 that is provided downstream of the developing unit in the rotation direction of the photosensitive member and transfers the toner image onto the transfer member such as the transfer paper P from the photosensitive member; And a discharging means such as a discharging lamp 8 for discharging the surface of the photosensitive member after the toner image is transferred from the photosensitive member to the transferring member by the transferring means. The latent image measuring means is located downstream of the developing means in the direction of rotation of the photoconductor and upstream of the static elimination means in the direction of rotation of the photoconductor. According to this, as described in the above embodiment, when the dark attenuation is deteriorated with the deterioration of the photoconductor, the photoconductor characteristics can be detected with higher accuracy.
(Aspect E)
In (Aspect A), (Aspect B), (Aspect C), or (Aspect D), the latent image is measured by the latent image measuring unit when the process control for changing the image forming process condition is executed. According to this, as described in the above embodiment, high-quality image formation can be performed.
(Aspect F)
In (Aspect A), (Aspect B), (Aspect C), (Aspect D) or (Aspect E), the induced current detection means is a transparent electrode arranged so as to face the surface of the photoreceptor at a predetermined interval. 11. A plurality of transparent electrode members such as 11 are provided, and the spot light irradiation means is positioned on the opposite side of the photoconductor across the transparent electrode member so that the photoconductor is irradiated with spot light through the transparent electrode member. Provided. According to this, as described in the above embodiment, the latent image can be measured by detecting the induced current with the transparent electrode.

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging apparatus 3 Exposure apparatus 4 Developing apparatus 5 Transfer apparatus 6 Fixing apparatus 7 Cleaning apparatus 8 Static elimination lamp 10 Latent image measuring apparatus 11 Transparent electrode 12 Laser beam optical system 13 Measuring part 14 LD driver 15 Controller 16 Pulse generator 17 Oscilloscope 18 Current Amplifier 19 Drive Rotation Controller 20 Gap Adjustment Roller 30 Line Latent Image 70 Line Latent Image

JP 2006-038666 A

Takeshima, Aizawa et al., Japan Hardcopy 2001, Proceedings, B-32, 281 Watanabe, Kawamoto et al., Japan Hardcopy 2000 Proceedings, A-26, p. 125

Claims (6)

A photoconductor provided rotatably;
Charging means for charging the surface of the photoreceptor;
Exposure means for exposing the surface of the photoreceptor charged by the charging means to form a latent image;
Spot light irradiating means for irradiating the surface of the photosensitive member with spot light in an irradiation range smaller than the latent image formed by the exposure means, and surface charge amount due to light attenuation of the photosensitive member by irradiating the spot light And an latent image measuring means for measuring a latent image formed on the surface of the photosensitive member based on a detection result of the induced current detecting means. In the forming device,
The latent image measuring means irradiates the spot light to the plurality of measurement positions set around the latent image and its periphery simultaneously or substantially simultaneously by the spot light irradiating means, and generates induced currents at the plurality of measurement positions. An image forming apparatus characterized by detecting by an induced current detecting means. The image forming apparatus according to claim 1.
The image forming apparatus, wherein the plurality of measurement positions include an image portion on which the latent image is formed and a non-image portion on which the latent image is not formed. The image forming apparatus according to claim 1 or 2,
A line latent image extending in the photosensitive member axial direction or the photosensitive member rotating direction is formed on the surface of the photosensitive member by the exposing means,
The spot light irradiation means irradiates spot light having an irradiation width smaller than the width of the line latent image,
The latent image measuring unit is configured to shift the spot light by the spot light irradiating unit simultaneously or substantially simultaneously to a plurality of measurement positions set by shifting the position with respect to the line latent image in each of the photosensitive member axial direction and the photosensitive member rotating direction. , And the induced current detection means detects the induced current at the plurality of measurement positions. The image forming apparatus according to claim 1, 2 or 3.
Developing means for developing the latent image formed on the surface of the photoconductor to form a toner image;
A transfer unit provided on the downstream side in the rotation direction of the photoconductor relative to the developing unit, and transferring a toner image from the photoconductor onto the transfer body;
A discharger provided downstream of the transfer unit in the rotation direction of the photosensitive member and discharging the surface of the photosensitive member after the toner image is transferred from the photosensitive member to the transfer member by the transfer unit; And
An image forming apparatus, wherein the latent image measuring unit is provided downstream of the developing device in the rotation direction of the photosensitive member and upstream of the neutralizing unit in the rotation direction of the photosensitive member. The image forming apparatus according to claim 1, 2, 3, or 4.
An image forming apparatus, wherein measurement of a latent image by the latent image measuring unit is performed at the time of execution of process control for changing an image forming process condition. The image forming apparatus according to claim 1, 2, 3, 4, or 5.
The induced current detection means has a plurality of transparent electrode members arranged to face the surface of the photoreceptor with a predetermined interval,
The spot light irradiating means is provided on the opposite side of the photosensitive member so that the spot light is irradiated to the photosensitive member through the transparent electrode member. Image forming apparatus.

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