JP2010204467A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve quality of images to be formed by preventing image unevenness caused by a developer pattern transferred by grooves of a supply member and developer stripes caused by a change in state of a developer. <P>SOLUTION: An image forming apparatus includes: an image carrier 10 for carrying images developed with a developing part 30; an optical sensor 21 having a light emitting part 210 for emitting light on the images developed on the image carrier 10, a first light receiving part 211 for receiving light reflected on the images, and a second light receiving part 212 disposed at a position different from the first light receiving part 211; and a control part for regulating a moving speed of a second supply member 35 by an output signal of the first light receiving part 211 and regulating bias applied on an electrification member 11 by an output signal of the second light receiving part 212. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention performs image formation by developing an electrostatic latent image formed on an image carrier with a liquid developer having toner and carrier liquid, and transferring and fixing the developed developer image onto a recording material. The present invention relates to an image forming apparatus and an image forming method.

Various image forming apparatuses for developing and visualizing an electrostatic latent image using a high-viscosity liquid developer in which a toner composed of a solid component is dispersed in a liquid solvent as a carrier liquid have been proposed. The developer used in this image forming apparatus has solid components (toner particles) suspended in a highly viscous organic solvent (carrier liquid) having electrical insulation properties such as silicon oil, mineral oil, and edible oil. Is. For the toner particles, extremely fine particles having a particle diameter of about 1 μm are used.
Compared with a conventional dry image forming apparatus using a particle diameter of 7 μm, high image quality can be achieved.

  As an image forming apparatus using such a liquid developer, for example, Patent Documents 1 to 3 describe an image forming apparatus that performs development by contacting a developing roller and a photoreceptor. In particular, as described in paragraph 46 of Patent Document 1, it is known that when the toner is weakly compressed, vertical streak-like image disturbances called riblets occur in the development nip. This phenomenon is formed between the developer carrying member and the photosensitive member as a result of the toner compression being weak and the toner particle moving speed at the developing nip being insufficient and the pressing to the photosensitive member being insufficient. This is because the liquid developer causes a stringing phenomenon at the developing nip exit.

JP 2008-170602 A US Pat. No. 5,610,694 US Pat. No. 5,737,666

  Such riblets (referred to as “developer streaks” in this specification) generated on the photoconductor also affect the transferred image onto a recording material such as paper, resulting in image unevenness in the transferred image. appear.

  On the other hand, one of the causes of image unevenness is a supply roller (anilox roller). The supply roller is a roller having a finely and obliquely grooved portion formed on the surface thereof, and supplies the liquid developer pumped up in the groove to the developing roller. The developer pattern generated by the groove usually disappears when supplied to the developing roller, and a uniform developer thin film is formed on the developing roller. However, due to various environmental changes, such as the viscosity of the liquid developer fluctuating due to temperature changes, the developer pattern does not disappear on the developing roller, which appears as image unevenness on the photoreceptor. It may end up.

  The present invention suppresses image unevenness caused by a developer pattern caused by a developer streak and a groove portion of a supply roller, and also maintains high image quality by maintaining a constant image density that fluctuates due to suppression of image unevenness. It is intended to be performed, and therefore the following various configurations are adopted.

  The image forming apparatus according to the present invention includes a first supply member having a groove, a second supply member carrying the liquid developer supplied by the first supply member, and the liquid developer supplied by the second supply member. A developer carrying member to be developed, a developing unit having a charging member for charging the liquid developer carried on the developer carrying member, an image carrier carrying an image developed in the developing unit, and the image A light emitting unit for emitting light to the image developed on the carrier, a first light receiving unit for receiving the light reflected by the image, and a second light receiving unit disposed at a position different from the first light receiving unit. An optical sensor, and a control unit that adjusts a moving speed of the second supply member by an output signal of the first light receiving unit and adjusts a bias applied to the charging member by an output signal of the second light receiving unit; It is characterized by having.

  With this configuration, it is possible to suppress image unevenness, maintain a constant image density, and perform high-quality image formation.

  Furthermore, in the image forming apparatus according to the aspect of the invention, when the output signal of the first light receiving unit is a first output value, the control unit moves the second supply member at a first moving speed, and When the output signal of the light receiving unit is a second output value larger than the first output value, the moving speed of the second supply member is adjusted to a second moving speed that is faster than the first moving speed. Yes. According to this configuration, the image density can be kept constant by simple control.

  Further, in the image forming apparatus according to the present invention, when the output signal of the second light receiving unit is a third output value, the control unit sets the bias applied to the charging member as the first bias, and the second light receiving unit. When the output signal of the unit is a fourth output value larger than the third output value, the bias of the charging member is adjusted to a second bias that is larger in absolute value than the first bias. According to this configuration, it is possible to suppress image unevenness with simple control.

  Furthermore, in the image forming apparatus of the present invention, the light detected by the first light receiving unit is a regular reflection light of the light reflected by the image, and the light detected by the second light receiving unit is reflected by the image. It is assumed that the scattered light is scattered light. According to this configuration, it is possible to accurately detect image density and image unevenness.

  Furthermore, in the image forming apparatus of the present invention, the control unit performs adjustment of the moving speed of the second supply member and adjustment of the bias applied to the charging member after printing a predetermined number of recording materials. Yes. As described above, by adjusting the adjustment timing after a predetermined number of sheets, it is possible to maintain the image quality in accordance with the state of the developer and the environmental change.

  Further, in the image forming method of the present invention, the liquid developer stored in the developer storage portion is supplied to the second supply member by the first supply member having the groove portion, and is supplied to the second supply member. A liquid developer is supplied to the developer carrier, the liquid developer supplied to the developer carrier is charged by a charging member, and the liquid developer charged by the charging member is used to form an image carrier. The formed latent image is developed, light is emitted to the developed image of the image carrier, and the light reflected by the image is received by the first light receiving unit, and the light reflected by the image is received by the first light. Light is received by a second light receiving unit disposed at a position different from the light receiving unit, the moving speed of the second supply member is adjusted by the output signal of the first light receiving unit, and the output signal of the second light receiving unit is used. A bias applied to the charging member is adjusted. It is.

  With this configuration, it is possible to suppress image unevenness, maintain a constant image density, and perform high-quality image formation.

1 is a cross-sectional view illustrating a main configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating main components of an image forming unit and a developing unit according to the embodiment of the present invention. The perspective view of the supply roller which concerns on embodiment of this invention. FIG. 4 is a diagram illustrating a state of liquid developer transfer in the developing device according to the embodiment of the invention. FIG. 4 is a diagram illustrating a state of transfer of a liquid developer from a developing roller to an image carrier. FIG. 4 is a diagram illustrating developer streaks in a test image on an image carrier. The figure which shows the optical sensor which concerns on embodiment of this invention. FIG. 3 is a diagram illustrating a toner charger according to an embodiment of the present invention. FIG. 3 is a diagram illustrating control of the image forming apparatus according to the embodiment of the invention. FIG. 3 is a flowchart showing control of the image forming apparatus according to the embodiment of the invention. 6 is a table used for control of the image forming apparatus according to the embodiment of the present invention. The figure which shows the relationship between an intermediate roller peripheral speed and a regular reflection light received signal. The figure which shows the relationship between a toner charger grid voltage and a scattered light received signal. FIG. 9 is a flowchart showing control of an image forming apparatus according to another embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a main configuration of an image forming apparatus according to an embodiment of the present invention. The four developing devices 30Y, 30M, 30C, and 30K are arranged at the lower part of the image forming unit with respect to the image forming unit arranged at the center of the image forming apparatus, and the intermediate transfer body 40, the secondary transfer unit ( The secondary transfer unit 60) is disposed above the image forming unit. Hereinafter, the image forming unit and the developing devices 30Y, 30M, 30C, and 30K will be described. However, since the configurations of the respective colors are the same, the alphabetical suffixes indicating the colors are omitted. Note that the image forming apparatus of the present embodiment is capable of forming a full-color image with four colors of YMCK, but is not limited to this embodiment, and may be an image forming apparatus that employs an appropriate number of colors such as a single color.

  The image forming unit includes an image carrier 10, a corona charger 11, an exposure unit 12, and the like. The exposure unit 12 includes a light source such as an LED or a semiconductor laser, and irradiates light based on an input image signal to form an electrostatic latent image on the charged image carrier 10.

  The developing device 30 generally includes a developer container 31 that stores the liquid developer of each color, a supply roller 34 that applies the liquid developer from the developer container 31 to the intermediate roller 35, and the like. The electrostatic latent image formed on the image carrier 10 is developed. The intermediate transfer member 40 is configured by an endless belt or the like, is stretched around a driving roller 41 and a tension roller 42, and is rotationally driven by the driving roller 41 while being in contact with the image carrier 10 by the primary transfer unit 50. In the primary transfer unit 50, the image carrier 10 and the primary transfer backup roller 51 are arranged to face each other with the intermediate transfer member 40 interposed therebetween, and development is performed with the contact position of these image carrier 10 as the transfer position. The toner images of the respective colors on the image carrier 10 thus formed are sequentially superimposed and transferred onto the intermediate transfer member 40 to form a full color toner image.

  In the secondary transfer unit 60, a secondary transfer roller 61 is disposed to face the driving roller 41 with the intermediate transfer body 40 interposed therebetween. Further, a secondary transfer roller cleaning unit 62 is disposed with the blade abutting against the secondary transfer roller 61. Then, at the transfer position on the secondary transfer roller 61, a recording material such as paper, film, cloth, or the like, on which the single-color toner image or full-color toner image formed on the intermediate transfer body 40 is conveyed through the sheet material conveyance path L Transcript to.

Further, a fixing unit (not shown) is disposed downstream of the sheet material conveyance path L, and a single color toner image or a full color toner image transferred onto a recording material such as paper is fused to the recording material such as paper. To fix. In addition, the tension roller 42 stretches the intermediate transfer body 40 together with the driving roller 41, and the intermediate transfer body cleaning unit 46 is brought into contact with the tension roller 42 at a position stretched on the tension roller 42 of the intermediate transfer body 40. Arranged.

  Next, an image forming unit and a developing device according to an embodiment of the present invention will be described. FIG. 2 is a cross-sectional view illustrating main components of the image forming unit and the developing device 30. Since the configurations of the image forming unit and the developing device for each color are the same, the description is based on the yellow (Y) image forming unit and the developing device, and the subscript alphabet is omitted.

  An image carrier cleaning unit 18, a corona charger 11, an exposure unit 12, a developing roller 36, and an image carrier squeeze roller 13 are disposed on the outer periphery of the image carrier 10 along the rotation direction. The image carrier squeeze roller 13 is provided with an image carrier squeeze roller cleaning unit 14 in contact with the blade as an additional component. A primary transfer backup roller 51 of the primary transfer unit 50 is disposed along the intermediate transfer body 40 at a position facing the image carrier 10.

  The image carrier 10 is a photosensitive drum made of a cylindrical member that is wider than the developing roller 36 and has a photosensitive layer formed on the outer peripheral surface thereof. For example, the image carrier 10 rotates in a clockwise direction as shown in FIG. . The photosensitive layer of the image carrier 10 is made of amorphous silicon or an organic photoconductor. The corona charger 11 is disposed upstream of the nip portion between the image carrier 10 and the developing roller 36 in the rotation direction of the image carrier 10, and the corona charger 11 coronas the image carrier 10 by a voltage applied from a power supply device (not shown). Charge. The exposure unit 12 irradiates the image carrier 10 charged by the corona charger 11 with light on the downstream side in the rotation direction of the image carrier 10 from the corona charger 11, and generates an electrostatic latent image on the image carrier 10. Form.

  The developing device 30 includes a developing roller 36, an intermediate roller 35, a supply roller 34, a developer container 31 that stores a liquid developer in a state where toner is dispersed in a carrier at a weight ratio of approximately 20%, and a developing roller 36. A toner charger 37 for charging the toner on the upper side is a main component. On the outer periphery of the developing roller 36, a cleaning blade 361, an intermediate roller 35, and a toner charger 37 are disposed. The surface of the intermediate roller 35 is in contact with the developing roller 36 and the supply roller 34, and an intermediate roller cleaning unit 351 is disposed on the outer periphery thereof. A regulating member 341 that adjusts the amount of liquid developer pumped up from the developer reservoir 311 is in contact with the supply roller 34. In the three-roller system using the intermediate roller 35 as in the developing device of this embodiment, the regulating member 341 is configured to adjust the amount of liquid developer by the intermediate roller 35 coming into contact with the supply roller 34. It can be omitted.

The liquid developer conveyed to the developer storage unit 311 is volatile at room temperature at a low concentration (1 to 2 wt%) and low viscosity using Isopar (trademark: exon) as a carrier, which is generally used conventionally. Not a volatile liquid developer, but a solid having an average particle diameter of 1 μm, in which a colorant such as a pigment is dispersed in a non-volatile resin having a high concentration and high viscosity at room temperature, an organic solvent, silicon oil, mineral oil or It is a liquid developer having a high viscosity (about 30 to 10000 mPa · s) added to a liquid solvent such as edible oil together with a dispersant and having a toner solid content concentration of about 20%.

  The supply roller 34 (“first supply member” in the present invention) has a function of supplying the liquid developer to the intermediate roller 35. The supply roller 34 is a cylindrical member, and is a roller having a groove portion such as a spiral groove that is finely and uniformly engraved spirally on the surface so that the liquid developer can be easily carried on the surface. The liquid developer pumped up by the groove is precisely measured by the contact regulating member 341 and supplied to the intermediate roller 35. During operation of the apparatus, as shown in the figure, the conveying screw 33 rotates clockwise to supply the liquid developer to the supply roller 34, and the supply roller 34 rotates clockwise to supply the liquid developer to the intermediate roller 35. Apply.

  The regulating member 341 is an elastic blade made of metal or having a surface covered with an elastic body. In this embodiment, it is composed of a rubber portion made of urethane rubber or the like that comes into contact with the surface of the supply roller 34, and a metal plate or the like that supports the rubber portion. Then, the film thickness and amount of the liquid developer carried and conveyed by the supply roller 34 are regulated and adjusted, and the amount of liquid developer supplied to the intermediate roller 35 is adjusted. In addition, it may replace with this control member 341 and it is good also as using the control roller comprised by the roller.

  The developing roller 36 (“developer carrier” in the present invention) is a cylindrical member, and rotates counterclockwise around the rotation axis as shown in FIG. The developing roller 36 is provided with an elastic layer such as polyurethane rubber, silicon rubber, NBR, or PFA tube on the outer periphery of an inner core made of metal such as iron. The developing roller cleaning blade 361 is made of rubber or the like that comes into contact with the surface of the developing roller 36, and is disposed downstream of the developing nip portion where the developing roller 36 comes into contact with the image carrier 10 in the rotation direction of the developing roller 36. The liquid developer remaining on the developing roller 36 is scraped off and removed.

  The intermediate roller 35 (“second supply member” in the present invention) is a cylindrical member, and rotates counterclockwise like the developing roller 36 as shown in FIG. Counter contact with 36. Similar to the developing roller 36, the intermediate roller 35 is configured by providing an elastic layer on the outer periphery of a metal inner core.

  An intermediate roller cleaning unit 351 is disposed downstream of the contact position between the intermediate roller 35 and the developing roller 36 with the blade contacting the intermediate roller 35 and scrapes off the liquid developer that has not been supplied to the developing roller 36. Take it and collect it in the recovered liquid reservoir.

  The toner charger 37 (“charging member” in the present invention) is an electric field applying unit that increases the charging bias on the surface of the developing roller 36. The liquid developer conveyed by the developing roller 36 is charged by applying an electric field by corona discharge at a position close to the toner charger 37.

  On the other hand, the charged liquid developer carried on the developing roller 36 corresponds to the electrostatic latent image on the image carrier 10 by a desired electric field in the developing nip portion where the developing roller 36 contacts the image carrier 10. Developed. The developer that has not contributed to the development is scraped off by the developing roller cleaning blade 361 and dropped into the collected liquid storage unit. The dropped developer is adjusted in its concentration by the liquid developer concentration adjusting unit and supplied to the developer storing unit 311 again to be reused.

  The image carrier squeeze device disposed on the upstream side of the primary transfer is disposed on the downstream side of the developing roller 36 so as to face the image carrier 10, and excessively develops the toner image developed on the image carrier 10. An apparatus for recovering the agent, the image carrier squeeze roller 13 comprising an elastic roller member that is coated with an elastic body and is in contact with the image carrier 10 and rotates, and the image carrier squeeze roller 13 And a cleaning blade 14 that contacts and cleans the surface, and has a function of recovering excess carrier from the developer developed on the image carrier 10 and increasing the toner particle ratio in the visible image. In the present embodiment, one image carrier squeeze roller 13 is provided as an image carrier squeeze device before primary transfer. However, a plurality of image carrier squeeze rollers may be provided. In that case, the image carrier squeeze roller that contacts and separates may be switched according to the state of the liquid developer.

In the primary transfer unit 50, the developer image developed on the image carrier 10 is transferred to the intermediate transfer member 40 by the primary transfer backup roller 51. Here, the image carrier 10 and the intermediate transfer member 40 are moved at the same speed, thereby reducing the driving load of rotation and movement and suppressing the disturbance effect on the visible toner image of the image carrier 10. .

  The image carrier cleaning unit 18 is a member that faces the image carrier 10 and is disposed downstream of the primary transfer unit 50. The image carrier 10 is brought into contact with the image carrier 10, so that the image carrier 10 The transfer residual liquid developer and the untransferred liquid developer are cleaned. The liquid developer scraped off by the image carrier cleaning unit 18 falls vertically downward and drops into the recovered liquid storage unit.

  The image forming apparatus according to the embodiment of the present invention has been described above. Next, the developer pattern generated by the supply roller 34 (the “first supply member” in the present invention) that causes image unevenness is illustrated in FIGS. 4 will be described.

  FIG. 3 is a perspective view of the supply roller 34 used in the present invention, and an enlarged view of a part thereof. The supply roller 34 in the present invention is provided with a concave pattern forming region at the center of the surface thereof as indicated by the hatched lines in the figure. The concave pattern formation region is intended to accurately measure the liquid developer and improve the supply efficiency. In the present embodiment, a spiral groove 342 is employed. The liquid developer pumped up by the groove 342 is supplied to the intermediate roller 35 with which the supply roller 34 abuts.

Next, the state of the developer pattern formed by the groove 342 of the supply roller 34 will be described with reference to FIG. FIG. 4A is a cross-sectional view of the developing device, and FIG. 4B is a diagram showing the state of the developer pattern on each roller. FIG. 4 (a) is similar to FIG.
) Is a cross-sectional view taken along the line AA ′, and the thick lines described on the surfaces of the supply roller 34, the intermediate roller 35, and the developing roller 36 indicate that the liquid developer pumped up from the developer storage unit 311 is transferred. Show. In this figure, the configuration around each roller is omitted.

  First, the liquid developer stored in the developer storage unit 311 is pumped up by the supply roller 34 that rotates clockwise, and the amount applied to the surface is regulated by the regulating member 341 that contacts the supply roller 34. The liquid developer applied to the supply roller 34 rotates counterclockwise and is supplied to the intermediate roller 35 that contacts the supply roller 34 in the forward direction. The liquid developer supplied to the intermediate roller 35 rotates counterclockwise and is supplied to the developing roller 36 that contacts the intermediate roller 35 in the reverse direction. The liquid developer supplied to the developing roller 36 develops a latent image on the image carrier 10 (not shown) to form an image.

  Since the groove 342 is formed on the surface of the supply roller 34 of the present embodiment, the liquid developer pumped up by the supply roller 34 has a developer pattern of the liquid developer on the surfaces of the intermediate roller 35 and the development roller 36. Form. The state of the developer pattern transfer is shown in FIG. FIG. 4B is a view of FIG. 4A viewed from the direction indicated by symbol A, and shows the state of the developer pattern on each roller. As shown in the figure, when the groove part 342 formed in the supply roller 34 has a diagonally downward pattern, the developer patterns on the surfaces of the intermediate roller 35 and the developing roller 36 are as shown in the figure. Specifically, a developer pattern that rises to the right is formed on the surface of the intermediate roller 35 that contacts the supply roller 34 in the forward direction, and even on the surface of the developing roller 36 that contacts the intermediate roller 35 in the opposite direction, A developer pattern that rises to the right is formed.

  As described above, in a state where the developer pattern by the groove portion 342 is transferred onto the developing roller 36, unevenness occurs in the image to be formed. Since the developer pattern depends on the viscosity of the liquid developer, it is desirable to suppress the developer pattern when the viscosity of the liquid developer fluctuates with various environmental changes.

  Next, a developer streak (riblet) that causes another image unevenness will be described in detail with reference to FIGS. FIG. 5 is a diagram showing a state of movement of the liquid developer between the image carrier 10 and the developing roller 36. As shown in the figure, the image carrier 10 and the developing roller 36 move in the same direction, and the latent image formed on the image carrier 10 is formed with a liquid developer applied on the surface of the developing roller 36. develop. During the development, the liquid developer moves from the developing roller 36 to the image carrier 10, but the fluid behavior of the liquid developer is disturbed near the nip exit between the developing roller 36 and the image carrier 10, and the liquid development is performed. A phenomenon occurs in which the agent leaves while pulling the thread.

  FIG. 6 shows the disturbance of the image on the image carrier 10 due to this phenomenon. FIG. 6A is a test image (AM screen, 283 lines, 50% halftone dot (1200 dpi, 3 × 3 lattice), also referred to as a patch image) formed on the image carrier 10. FIG. 6B is an enlarged view of a part of this test image. In the normal state, this test image is a uniform image with light and shade, but when the above phenomenon occurs, the test image is perpendicular to the moving direction of the image carrier 10 as shown in FIG. The density of the image is generated in the direction (lateral direction in the figure), and an image including a developer streak such as a stream (riblet) is formed along the moving direction of the image carrier 10.

  Similar to the developer pattern described above, this developer streak also affects the transferred image onto a recording material such as paper, and appears as image unevenness in the transferred image. It is desirable to suppress the occurrence of this developer streak and improve the image quality.

  The present invention is characterized in that generation of these developer patterns and developer streaks is suppressed, and the quality of an image finally printed on a recording material is improved. Then, the developer pattern and the image density that fluctuates when suppressing the generation of the developer streaks are also adjusted.

  Now, the configuration of the present invention will be described with reference to FIGS. FIG. 7 is a diagram showing the optical sensor 21 used in the embodiment of the present invention. The optical sensor 21 includes a light emitting unit 210, a first light receiving unit 211, and a second light receiving unit 212 as its configuration. The light emitting unit 210 is composed of a light emitting element such as an LED, and irradiates the base material with light at a predetermined incident angle (direction of incident light indicated by an arrow in the figure).

  The first light receiving unit 211 is a sensor provided to detect the image density of the developer layer applied on the surface of the substrate. When the image density is high, the specular reflection light becomes small, and conversely, when the image density is low, the specular reflection light becomes large. In order to capture regular reflection light efficiently, it is preferably disposed at a position where the reflection angle and the incident angle are equal.

  The second light receiving unit 212 is a sensor provided to detect unevenness of the developer layer applied to the substrate surface. When unevenness occurs in the developer layer, the scattered light becomes large, and conversely, the unevenness of the developer layer is detected by utilizing the characteristic that the scattered light becomes small when there is no unevenness. In the present embodiment, the second light receiving unit 212 is disposed vertically above the light incident position, so that scattered light can be detected efficiently.

  FIG. 8 is a diagram showing the toner charger 37 used in the embodiment of the present invention. The toner charger 37 is a member that charges the toner on the developing roller 36, and for example, a scorotron that charges by ion charging is used like the corona charger 11 provided in the image carrier 10. As the toner charger 37, not only this scorotron but also various toner chargers such as a contact type in which a roller or a blade is brought into contact for charging can be adopted.

The toner charger 37 using the scorotron is composed of a shield 371, a grid 372, and a metal wire 373. A constant current power supply 26 is connected to the metal wire 373, and a constant charge is released from the metal wire 373. In this embodiment, the value of the constant current power source is 2 [μA / mm]. The grid 372 is in electrical continuity with the shield 371, and the voltage from the voltage power source 25 connected to the shield 371 is applied as it is. The voltage applied to the grid 372 controls how much of the electric charge emitted from the metal wire 373 passes to the toner on the developing roller 36.

  The charge amount of the toner is a value determined by the voltage Vd applied to the developing roller 36 and the grid voltage Vg applied to the grid 372, and is an amount proportional to the difference Vg−Vd between the voltages. In the toner charger 37 using a scorotron, the charge amount is adjusted by changing the grid voltage Vg as a bias. In this embodiment, the representative value of Vd is 300 [V], and the representative value of Vg is 375 [V]. Note that when a toner charger 37 of a type other than Scorotron is used, the bias for adjusting the charge amount is adjusted according to the type.

  If the charge amount of the toner is small, the transferability of the toner from the developing roller 36 to the image carrier 10 is deteriorated and image unevenness is likely to occur. On the other hand, when the charge amount of the toner is large, the transferability of the toner from the developing roller 36 to the image carrier is improved, so that image unevenness hardly occurs. However, since the toner aggregates when the charge amount of the toner is excessively large, it is necessary to keep the charge amount of the toner moderately as much as necessary to suppress the occurrence of image unevenness.

  The present invention is intended to improve the quality of an image printed using the relationship between the toner charge amount and the occurrence of image unevenness. Now, control of the image forming apparatus according to the embodiment of the present invention will be described. FIG. 9 is a diagram showing an example of control of the image forming apparatus using the optical sensor 21 described in FIG. 7 and the toner charger 37 described in FIG. The optical sensor 21 is disposed on the image carrier 10 at a position where an image developed on the developing roller 36 can be detected. In the present embodiment, it is arranged before passing through the squeeze roller 13, but it may be arranged after passing through the squeeze roller 13 and before passing through the primary transfer unit 50.

  The optical sensor 21 arranged in this manner irradiates light on the surface of the image carrier 10 serving as a base material, and detects a specular reflection light signal and a scattered light signal. The detected scattered light signal is used for adjusting image unevenness. In this embodiment, the occurrence of image unevenness is suppressed by adjusting the grid voltage of the toner charger 37.

  On the other hand, as the toner charge amount is adjusted, the image density on the image carrier 10 varies. The image density also varies due to changes in the surrounding environment such as temperature and developer deterioration. In order to obtain a good printed image, in addition to suppressing image unevenness, it is necessary to appropriately adjust the image density. In the present embodiment, the image density on the image carrier 10 is detected by the optical sensor 21, and the peripheral density of the intermediate roller 35 ("moving speed" in the present invention) is adjusted to keep the image density constant. .

As the peripheral speed of the intermediate roller 35 is increased, the amount of liquid developer applied to the developing roller 36 increases, and the amount of liquid developer applied to the image carrier 10 also increases. In the present embodiment, by adjusting the peripheral speed of the intermediate roller 35, the coating amount on the developing roller 36 can be varied from 0.4 to 0.8 [mg / cm ² ].

Specifically, when the output value of the regular reflection light signal received by the first light receiving unit 211 is large, that is, when the image density is small, application is performed by increasing the peripheral speed of the intermediate roller 35 by the drive motor 24. Increase the amount to increase the image density. On the other hand, when the output value of the regular reflection light signal received by the first light receiving unit is small, that is, the image density is high, the image density is reduced by reducing the coating amount by slowing the peripheral speed of the intermediate roller 35. I am going to do that.

  When the peripheral speed of the intermediate roller 35 is changed, the peripheral speed of the supply roller 34 may be changed together. By making the peripheral speed of the intermediate roller 35 and the supply roller 34 constant, it is possible to prevent the intermediate roller 35 from being worn by the groove 342 of the supply roller 34.

  The control of the image forming apparatus according to the embodiment of the present invention will be described with reference to FIGS. FIG. 10 is a flowchart showing the control of the image forming apparatus, FIG. 11 is a table used for controlling the image forming apparatus, and FIG. 12 shows the relationship between the peripheral speed of the intermediate roller and the regular reflection light signal. FIG. 13 is a diagram showing the relationship between the grid voltage of the toner charger and the scattered light reception signal.

  In the flowchart of FIG. 10, when printing is started (S100), first, in S101, the application amount, that is, the peripheral speed of the intermediate roller 35, the toner charge amount, that is, the applied voltage to the toner charger 37, Each initial value is determined. If a predetermined time or more (for example, 1 hour) has not elapsed since the end of the previous printing, the value used at the end of the previous printing is used. On the other hand, when a predetermined time or more has elapsed, the respective initial values are determined in a second adjustment process described later. As described above, the entire process can be simplified by omitting the second adjustment process when the predetermined time has not elapsed.

  In S102, it is determined whether or not the remaining number of prints is less than n (for example, 5). If it is determined that there are more than n sheets, the adjustment process from S104 to S106 is executed after printing n sheets in S103. Thus, in this embodiment, image unevenness and image density are adjusted every time n sheets of recording materials are printed. On the other hand, if it is determined in S102 that the remaining number of prints is less than n, the remaining number of prints is executed in S107, and then the printing is terminated (S108).

  Now, the adjustment processing from S104 to S106 will be described in detail. First, a test image (also referred to as a patch image) is printed outside the image area of the image carrier 10 in S104. As this test image, an appropriate image such as a solid image (solid patch) or a grid-like image (screen patch) can be used, but it is preferable to use a solid image in order to detect image unevenness more accurately. Instead of using such a test image, an appropriate location suitable for detection of image unevenness and image density in the image used for printing may be used. In that case, image unevenness and image density can be detected during printing in S103, and the processing in S104 can be omitted.

  In S <b> 105, the test image printed in S <b> 104 is irradiated with light from the light emitting unit 210, regular reflection light is received by the first light receiving unit 211, and scattered light is received by the second light receiving unit 212. The received regular reflection light and scattered light are converted into a regular reflection light signal such as a voltage value and a scattered light signal by the optical sensor 21 and used for control.

  The specular reflection signal and the scattered light signal output from the optical sensor 21 are supplied from the control unit 22 with a control signal for the drive motor 24 that drives the intermediate roller 35 and a voltage power source that controls the grid voltage of the toner charger 37. 25 control signals are converted.

Now, control of image density in the present embodiment will be described. FIG. 12 is a diagram showing the relationship between the regular reflection light signal and the peripheral speed of the intermediate roller 35. A reference range including an optimum value is set for the regular reflection light signal. In this embodiment, if the output value of the regular reflection light signal is within this reference range, the image density is appropriate, and the peripheral speed of the intermediate roller 35 is set so that the output value of the regular reflection light signal is within the reference range. To control.

  When the output value of the regular reflection light signal exceeds the upper limit of the reference range, it is determined that the image density is too small, and the control signal for the drive motor 24 is changed so that the peripheral speed of the intermediate roller 35 is increased. On the other hand, when the output value of the regular reflection signal falls below the lower limit of the reference range, it is determined that the image density is too high, and the control signal for the drive motor 24 is changed so that the peripheral speed of the intermediate roller 35 is decreased. In the present embodiment, when the output value of the regular reflection light signal exceeds the upper limit of the reference range, the peripheral speed of the intermediate roller 35 is increased by 5 [mm / s], and the output value of the regular reflection light signal is within the reference range. When the value falls below the lower limit, the peripheral speed of the intermediate roller 35 is decreased by 5 [mm / s].

  Next, image unevenness control in the present embodiment will be described. FIG. 13 is a diagram showing the relationship between the scattered light signal and the grid voltage of the toner charger 37. A reference range including an optimum value is set for the scattered light signal. In this embodiment, if the scattered light signal is within the reference range, the image unevenness is within the allowable range, and the grid voltage of the toner charger 37 is controlled so that the scattered light signal is within the reference range.

When the output value of the scattered light signal exceeds the upper limit of the reference range, it is determined that the image unevenness exceeds the allowable range, and the control signal for the voltage power supply 25 is changed so as to increase the grid voltage of the toner charger 37. When the grid voltage is negative, the control signal is changed so as to lower the grid voltage. In other words, control is performed so that the grid voltage of the toner charger 37 is increased in absolute value. On the other hand, when the output value of the scattered light signal falls below the lower limit of the reference range, the grid voltage of the toner charger 37 is lowered to avoid excessive toner aggregation (the grid voltage of the toner charger 37 is an absolute value). The control signal for the voltage power supply 25 is changed (to be smaller at In this embodiment, the grid voltage is increased by 5 [V] when the output value of the scattered light signal exceeds the upper limit of the reference range, and the grid voltage is increased when the output value of the scattered light signal falls below the lower limit of the reference range. By lowering by 5 [V], it is possible to suppress image unevenness without excessive toner aggregation.

  FIG. 11 shows a table used for control of the control unit 22 of the present embodiment. It can be seen that nine patterns are controlled by a combination of the scattered light signal and the regular reflection light signal. As described above, in this embodiment, the optical sensor 21 detects the scattered light signal of the image to detect image unevenness, and the bias applied to the toner charger 37 is controlled so as to suppress it. Then, by controlling the image unevenness and detecting the image density that changes with various environmental changes with the optical sensor 21, the image density is kept constant together with the image unevenness suppression, and high-quality image formation is achieved. Can be done.

  Next, the second adjustment processing according to the embodiment of the present invention will be described with reference to FIG. In the present embodiment, this second adjustment process is a process performed in S101 of FIG. 10 when a predetermined time or more has elapsed since the end of the previous printing, and is more accurate than the adjustment process of FIG. In this process, the peripheral speed of the roller 35 and the grid voltage of the toner charger 37 are adjusted.

  In this second adjustment process, first, in S201, the peripheral speed of the intermediate roller 35 and the initial value of the grid voltage of the toner charger 37 are determined. In the present embodiment, these initial values are the values at the end of the previous time. S202 to S205 are application amount control steps, and in the present embodiment, the application amount of the liquid developer is brought close to the optimum value by adjusting the peripheral speed of the intermediate roller 35.

In this coating amount control step, first, in S202, the peripheral speed of the intermediate roller 35 is reduced by a predetermined amount from the initial value (in this embodiment, 30 [mm / s]). Next, a test image is printed outside the image area of the image carrier 10 in S203. As this test image, a solid image (solid patch) or a grid-like image (screen patch) is used as in S104 of FIG. In S204, it is determined whether or not the regular reflection light signal for the test image is below the optimum value as shown in FIG. If it is determined that the speed is lower, the current peripheral speed of the intermediate roller 35 is adopted as a value used for control, and the coating amount control process is terminated. On the other hand, if it is determined that the speed is not lower, the peripheral speed of the intermediate roller 35 is increased by a predetermined amount in S205 (in this embodiment, 5 [mm / s]), and the process returns to S203. As described above, in this step, after the peripheral speed of the intermediate roller 35 is once lowered from the initial value, the peripheral speed is increased by a predetermined amount and the optimum peripheral speed of the intermediate roller 35 is searched. In the present embodiment, the optimum peripheral speed is searched while increasing the peripheral speed of the intermediate roller 35, but the optimum value may be searched while decreasing the peripheral speed.

  In S204, when the regular reflection light signal falls below the optimum value and the peripheral speed of the intermediate roller 35 is determined, the process proceeds from S206 to the toner charge amount control process in S209. In this step, as in the coating amount control step, a search for an optimal control value is performed by sequentially shifting the control value by a predetermined amount.

  In this toner charge amount control step, first, in S206, the grid voltage of the toner charger 37 is lowered by a predetermined amount from the initial value (in this embodiment, 30 [V]). Next, in S207, a test image is printed outside the image area of the image carrier 10 as in S203. In S208, it is determined whether or not the scattered light signal for the test image is below the optimum value as shown in FIG. If it is determined that the voltage is lower, the current grid voltage is adopted as a value used for control, and the toner charge amount control process is terminated.

  On the other hand, if it is determined that the voltage is not lower, the voltage of the toner charger 37 is increased by a predetermined amount in S209 (in this embodiment, 5 [V]), and the process returns to S207. As described above, in this step, the grid voltage of the toner charger 37 is once lowered from the initial value, and the grid voltage is sequentially shifted by a predetermined amount to search for the optimum grid voltage. In the toner charge amount control process, the optimum value may be searched for while lowering the grid voltage.

As described above, the second adjustment process according to another embodiment of the present invention has been described. In this second adjustment process, the application amount control process for determining the peripheral speed of the intermediate roller 35 and the grid voltage of the toner charger 37 are set. By performing the toner charge amount control process to be determined separately, the adjustment can be performed with higher accuracy than the adjustment process described with reference to FIG. Note that the second adjustment process of this embodiment is performed in the order of the application amount control process and the toner charge amount control process, but may be performed in the order of the toner charge amount control process and the application amount control process. . In the present embodiment, the amount to be sequentially shifted is a fixed predetermined amount. However, the predetermined amount is changed after being below the optimum value or approaching the optimum value (for example, the grid voltage) In some cases, 5 [
(V] is lowered to 1 [V]), and the process can be made closer to the optimum value. Although various embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and embodiments configured by appropriately combining the configurations of the respective embodiments also fall within the scope of the present invention. Is.

DESCRIPTION OF SYMBOLS 10 ... Image carrier, 11 ... Corona charger, 12 ... Exposure unit, 13 ... Image carrier squeeze roller, 14 ... Image carrier squeeze roller cleaning part, 18 ... Image carrier cleaning part,
21 ... Optical sensor, 210 ... Light emitting unit, 211 ... First light receiving unit, 212 ... Second light receiving unit,
DESCRIPTION OF SYMBOLS 30 ... Developing part, 31 ... Developer container, 311 ... Developer storage part, 34 ... Supply roller (supply member), 341 ... Restriction member, 342 ... Groove part, 35 ... Intermediate roller (second supply member), 351 ... Intermediate Roller cleaning section, 36 ... developing roller (developer carrier), 361 ... developing roller cleaning section, 37 ... toner charger (charging member), 371 ... shield, 372 ... metal wire, 373 ... grid,
40 ... Intermediate transfer member, 41 ... Driving roller, 42 ... Tension roller, 46 ... Intermediate transfer member cleaning unit,
50 ... primary transfer part, 51 ... primary transfer backup roller,
60 ... secondary transfer unit, 61 ... secondary transfer roller, 62 ... secondary transfer roller cleaning unit

Claims (6)

A first supply member having a groove, a second supply member for carrying the liquid developer supplied by the first supply member, a developer carrier for developing with the liquid developer supplied by the second supply member, and A developing unit having a charging member for charging the liquid developer carried on the developer carrying member;
An image carrier for carrying an image developed in the developing unit;
A light emitting unit that emits light to the image developed on the image carrier, a first light receiving unit that receives the light reflected by the image, and a second light receiving unit disposed at a position different from the first light receiving unit. An optical sensor having a portion;
A control unit that adjusts a moving speed of the second supply member based on an output signal of the first light receiving unit and adjusts a bias applied to the charging member based on an output signal of the second light receiving unit. An image forming apparatus. The control unit moves the second supply member at a first moving speed when the output signal of the first light receiving unit is a first output value.
When the output signal of the first light receiving unit is a second output value larger than the first output value, the moving speed of the second supply member is adjusted to a second moving speed that is faster than the first moving speed. The image forming apparatus according to claim 1. The control unit sets the bias applied to the charging member to the first bias when the output signal of the second light receiving unit is a third output value,
When the output signal of the second light receiving unit is a fourth output value that is larger than the third output value, the bias of the charging member is adjusted to a second bias that is larger in absolute value than the first bias. The image forming apparatus according to claim 1.   The light detected by the first light receiving unit is specularly reflected light of the light reflected by the image, and the light detected by the second light receiving unit is scattered light of the light reflected by the image. The image forming apparatus according to claim 1.   5. The control unit according to claim 1, wherein the control unit performs adjustment of a moving speed of the second supply member and adjustment of a bias applied to the charging member after printing a predetermined number of recording materials. The image forming apparatus described in 1. Supplying the liquid developer stored in the developer storage portion to the second supply member by the first supply member having the groove,
Supplying the liquid developer supplied to the second supply member to a developer carrier;
Charging the liquid developer supplied to the developer carrier with a charging member;
Developing the latent image formed on the image carrier using the liquid developer charged by the charging member,
Light emitted from the developed image of the image carrier and reflected by the image is received by the first light receiving unit, and the light reflected by the image is disposed at a position different from the first light receiving unit. Received by the second light receiving unit,
An image forming method comprising: adjusting a moving speed of the second supply member based on an output signal of the first light receiving portion, and adjusting a bias applied to the charging member based on an output signal of the second light receiving portion.

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