JP2010197526A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To raise detection accuracy of a developer pattern by transfer of a groove part of a supply member, developer stripes to be generated in accordance with state change of developer, and image density. <P>SOLUTION: The image forming apparatus has: a developing part 30 which has a supply member 34 having the groove part 342 in a first direction, and a developer carrier which carries liquid developer supplied from the supply member 34; an image carrier 10 which carries an image developed by the developing 30; and an optical sensor 21 which has a light emitting part 210 which emits light on the image of the image carrier 10, a first light receiving part 211 which receives the light emitted by the light emitting part and reflected on the image, and a second light receiving part 212 which is arranged at a position different from that of the first light receiving part 211 to receive the light emitted by the light emitting part and reflected on the image, wherein a virtual line which connects the light emitting part 210 and the first light receiving part 211 is differentiated from the first direction of the groove part 342 and a moving direction of the image carrier 10. <P>COPYRIGHT: (C)2010,JPO&amp;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, and it also appears on the image on the photoreceptor. It may end up.

  Although developer streaks and developer patterns that cause these image unevenness can be eliminated by adjusting the state of various liquid developers, it is hoped to improve the detection accuracy of these developer streaks and developer patterns. It is rare.

SUMMARY OF THE INVENTION An object of the present invention is to improve the detection accuracy of a developer pattern due to transfer of a groove portion of a supply member, a developer streak generated with a change in the state of a liquid developer, and image density. For this reason, the following configuration is adopted.

  An image forming apparatus according to the present invention carries a developer storage section for storing a liquid developer having toner and carrier liquid, a supply member having a groove in a first direction, and the liquid developer supplied by the supply member A developing unit having a developer carrying member, an image carrier carrying an image developed by the developing unit, a light emitting unit that emits light to the image of the image carrier, and the image emitted by the light emitting unit. An optical element having a first light receiving unit that receives the light reflected by the first light receiving unit, and a second light receiving unit that is disposed at a different position from the first light receiving unit and receives the light emitted from the light emitting unit and reflected by the image. A virtual line connecting the light emitting unit and the first light receiving unit is different from the first direction of the groove and the moving direction of the image carrier. It is. With this configuration, it is possible to improve the detection accuracy of developer streaks and developer patterns generated on the image carrier.

  Furthermore, in the image forming apparatus of the present invention, the light emitting unit and the first light receiving unit are disposed at a position where an incident angle of light emitted from the light emitting unit is equal to a reflection angle of light reflected from the image. It is what is done. With this configuration, it is possible to efficiently receive regular reflection light by the first light receiving unit and accurately detect the developer concentration on the image carrier.

  Furthermore, in the image forming apparatus of the present invention, the second light receiving unit is disposed vertically above a position where light from the light emitting unit is incident on the image. With this configuration, it is possible to efficiently receive reflected light by the second light receiving unit and further improve the detection accuracy of the developer streaks and the developer pattern generated on the image carrier.

  Furthermore, in the image forming apparatus according to the present invention, the developing unit is in contact with the supply member and the developer carrier, and supplies the liquid developer supplied from the supply member to the developer carrier. It has a member. According to such a configuration, the liquid developer supplied to the developer carrier is sufficiently kneaded by passing through the nip portion of each roller a plurality of times, and the liquid developer having a uniform thickness is developed on the developer carrier. An agent film can be formed.

  Furthermore, the image forming apparatus of the present invention includes a control unit that changes a peripheral speed ratio between the peripheral speed of the image carrier and the peripheral speed of the second supply member. By changing the peripheral speed ratio in this way, it is possible to adjust the amount of the liquid developer supplied to the developer carrier, that is, the film thickness of the liquid developer formed on the developer carrier.

    Furthermore, in the image forming apparatus of the present invention, the supply member comes into contact with the developer carrying member, and the configuration of the developing unit can be simplified with such a configuration.

  Furthermore, the image forming apparatus of the present invention includes a control unit that changes a peripheral speed ratio between the peripheral speed of the image carrier and the peripheral speed of the supply member. By changing the peripheral speed ratio in this way, it is possible to adjust the amount of the liquid developer supplied to the developer carrier, that is, the film thickness of the liquid developer formed on the developer carrier.

In the image forming method of the present invention, the liquid developer stored in the developer storage portion is supplied to the developer carrier by a supply member having a groove in the first direction, and supplied to the developer carrier. The latent image formed on the image carrier is developed using the liquid developer thus formed, and the light emitting unit and the first light receiving unit are moved in a direction different from the first direction and the moving direction of the image carrier. Using the arranged optical sensor, the developed image of the image carrier is emitted by the light emitting unit, and the light reflected by the image is received by the first light receiving unit and reflected by the image. The light is received by a second light receiving portion disposed at a position different from the first light receiving portion. With this configuration, it is possible to improve the detection accuracy of developer streaks and developer patterns generated on the image carrier.

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. The figure which shows the angle which a developer pattern forms on each roller which concerns on embodiment of this 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. FIG. 3 is a diagram illustrating a developer pattern and developer stripes generated on an image carrier. The figure which shows the optical sensor which concerns on embodiment of this invention. FIG. 4 is a diagram illustrating control of a developing unit according to the embodiment of the present invention. The figure which shows the virtual line of the optical sensor on an image carrier. The figure which shows the prohibition direction of the virtual line of the optical sensor on the image carrier which concerns on embodiment of this invention. The figure which shows the angle which a developer pattern forms on each roller which concerns on embodiment of this invention. The figure which shows the angle which a developer pattern forms on each roller which concerns on embodiment of this invention. The figure which shows the angle which a developer pattern forms on each roller which concerns on embodiment of this invention. The figure which shows the angle which a developer pattern forms with respect to the peripheral speed of each roller which concerns on embodiment of this invention. The figure which shows the angle range of a developer pattern in the case of having a circumferential speed difference. Sectional drawing which shows the main structures of the image formation part which concerns on other embodiment of this invention, and the image development part.

  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 at 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 composed of an organic image carrier or an amorphous silicon image carrier. 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 a voltage is applied from a power supply device (not shown) to remove the image carrier 10 from the corona. 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 (“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 FIG. 2, the transport screw 33 rotates clockwise to supply the liquid developer to the supply roller 34, and the supply roller 34 rotates clockwise to perform liquid development on the intermediate roller 35. Apply the agent.

  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) is an electric field applying unit that increases the charging bias on the surface of the developing roller 36, and the liquid developer conveyed by the developing roller 36 is corona at a position close to the toner charger 37. An electric field due to discharge is applied and charged. The electric field applying means for charging the toner may use a compaction roller or the like instead of the corona discharge of the corona discharger. Such a compaction roller is a cylindrical member having a structure in which a conductive resin layer or rubber layer is provided on the surface layer of a metal roller base, and for example, it is rotated clockwise in the direction opposite to the developing roller 36. Good.

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, FIGS. 3 to 5 show developer patterns generated by the supply roller 34 (the “supply member” in the present invention) that causes image unevenness. It explains using.

  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 FIGS. 4 and 5. 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. 5 is a diagram illustrating the developer pattern by the supply roller 34.

FIG. 4A is a cross-sectional view taken along the line AA ′ in FIG. 4B, and the thick lines described on the surfaces of the supply roller 34, the intermediate roller 35, and the developing roller 36 are drawn from the developer reservoir 311. This shows how the liquid developer pumped up is transferred. 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,
It is supplied to an intermediate roller 35 that abuts 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 described in FIG. 3 is formed on the surface of the supply roller 34 of the present embodiment, the liquid developer pumped up by the supply roller 34 is liquid developed on the surfaces of the intermediate roller 35 and the development roller 36. A developer pattern of the agent is formed. 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.

  FIG. 5 is a schematic diagram for explaining a developer pattern on each roller, and the peripheral speed Vdr of the developing roller 36, the peripheral speed Vmr of the intermediate roller 35, and the peripheral speed Var of the supply roller 34 are equal. The developer pattern in each roller is shown. Here, the peripheral speed refers to the speed in the tangential direction of each roller surface. As described with reference to FIG. 4, the developer pattern formed on each roller is formed with a developer pattern indicated by diagonal lines in the drawing in the present embodiment in which the groove portion 342 has a spiral shape.

  Here, the acute angle formed by the supply roller 34 with the groove 342 in the surface movement direction is θar, the acute angle formed by the developer pattern on the intermediate roller 35 with the surface movement direction is θmr, and the developer pattern on the developing roller 36 is in the surface movement direction. When the acute angle formed is θdr, when the peripheral speeds of the rollers are equal, the angles formed by the developer patterns of the rollers with the surface movement direction are equal, and the relationship θar = θmr = θdr is established.

  As described above with reference to FIGS. 3 to 5, when the developer pattern formed by the groove 342 formed on the supply roller 34 is transferred onto the developing roller 36, unevenness occurs in the formed image. It becomes. Since this developer pattern depends on the viscosity of the liquid developer, when the viscosity of the liquid developer fluctuates with various environmental changes, it is desirable to accurately detect the occurrence of the developer pattern.

  Next, a developer streak (riblet) that causes another image unevenness will be described in detail with reference to FIGS. FIG. 6 is a diagram illustrating the 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. 7 shows the disturbance of the image on the image carrier 10 due to this phenomenon. FIG. 7A is a test image (AM screen, 283 lines, 50% halftone dot (1200 dpi, 3 × 3 grid), also referred to as patch image) formed on the image carrier 10. FIG. 7B 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.

  The developer streaks generated on the image carrier 10 have been described with reference to FIGS. 6 and 7. The developer streaks are also transferred images onto a recording material such as paper as in the developer pattern described above. The image also appears as image unevenness in the transferred image. It is desirable to detect this developer streak with high accuracy.

  FIG. 8 is a diagram schematically illustrating a developer pattern and developer streaks that cause image unevenness. FIG. 8A is a schematic diagram of a developer pattern, and the developer pattern forms an angle θdr with respect to the moving direction of the image carrier 10 as indicated by an arrow. On the other hand, FIG. 8B is a schematic diagram of a developer streak, and the streak is formed in the same direction as the moving direction of the image carrier as indicated by an arrow. An object of the present invention is to accurately detect the developer pattern and developer stripe.

  FIG. 9 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 small, the specular reflection light becomes large. Thus, the image density is detected. 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. 10 is a diagram illustrating an example of control of the image forming apparatus using the optical sensor 21. 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 regular reflection light signal is used by the developing unit 30 to adjust the image density. In the present embodiment, the application amount of the liquid developer from the developing roller 36 to the image carrier 10 is adjusted by adjusting the voltage to the developing roller 36. On the other hand, the detected scattered light signal is used for image unevenness adjustment. In the present embodiment, by adjusting the voltage applied to the toner charger 37, the degree of toner charge is changed, and the occurrence of image unevenness is suppressed. The adjustment of the image density and the image unevenness is not limited to this embodiment, and any appropriate form can be adopted.

  FIG. 11 shows a case where the optical sensor 21 described in FIG. 9 is disposed on the image carrier 10, and is a view of the base material surface (the surface of the image carrier 10) seen from above in FIG. In the optical sensor 21, the light emitting unit 210, the first light receiving unit 211, and the second light receiving unit 212 form virtual lines arranged on a straight line.

As shown in FIG. 11A, when the optical sensor 21 is disposed so that the developer pattern that forms the angle θdr with the moving direction of the image carrier 10 and the virtual line are in the same direction, the liquid developer Scattered light is hardly generated because there is little surface irregularity change. Therefore, even when a developer pattern is generated, the second light receiving element 212 cannot detect a signal, and it is difficult to detect the generation of the developer pattern.

  Then, as shown in FIG. 11B, when the optical sensor 21 is arranged so that the imaginary line is also in the same direction as the developer stripe in the same direction as the moving direction of the image carrier 10. Since the unevenness of the surface of the liquid developer is small, almost no scattered light is generated. Therefore, even if a developer streak occurs, the second light receiving element 212 cannot detect a signal, and it becomes difficult to detect the occurrence of the developer streak.

  As described above, when the imaginary line of the optical sensor 21 is rotated at the same peripheral speed, the direction of the developer pattern, that is, the supply roller 34, the intermediate roller 35, and the developing roller 36 as in the present embodiment. When the same direction as the groove 342 of the supply roller 34 is used, or when the imaginary line is the same as the direction of the developer streak, that is, the moving direction of the image carrier 10, the developer pattern and the developer streak Cannot be detected accurately. Therefore, in the present invention, in order to accurately detect the developer pattern and the developer stripe, the imaginary line of the optical sensor 21 is different from the moving direction of the groove portion 342 of the supply roller 34 and the image carrier 10. The optical sensor 21 is provided.

  FIG. 12 is a schematic diagram in which the developer pattern and the developer stripe are shown together on the image carrier 10, and the drawing shows the direction of the developer pattern and the direction of the developer stripe with arrows. ing. In the present invention, the imaginary line of the optical sensor 21 is arranged so as not to be in the direction of these arrows. Even if the imaginary line is slightly deviated from these arrows, it is possible to detect the developer pattern and the developer stripe, but the imaginary line does not fall within the range of ± 5 [°] with respect to the direction of the double arrow. As a result, it was confirmed that unevenness can be detected with high accuracy.

  As described above, according to the present invention, image unevenness is detected with high accuracy by taking into account the direction of the developer pattern and developer stripe generated on the image carrier 10 and the direction of the imaginary line of the optical sensor 21. It becomes possible.

  Now, another embodiment of the present invention will be described with reference to FIGS. As an example of control of the image forming apparatus using the optical sensor 21, in FIG. 10, the voltage to the developing roller 36 is adjusted, and the application amount of the liquid developer from the developing roller 36 to the image carrier 10 is adjusted. explained. Adjustment of the coating amount on the image carrier 10 can also be realized by changing and controlling the ratio of the peripheral speed of the developing roller 36 and the peripheral speed of the intermediate roller 35.

  When the peripheral speed ratio between the developing roller 36 and the intermediate roller 36 is changed and controlled, the angle of the developer pattern generated on the developing roller 36 also varies. Here, a case where the peripheral speed ratio between the developing roller 36 and the intermediate roller 36 is changed and controlled will be described.

  FIG. 13 is a view when the peripheral speed of the intermediate roller 35 is made slower than the peripheral speed of the developing roller 36. In this embodiment, the supply roller 34 rotates with the intermediate roller 35 in accordance with the peripheral speed of the intermediate roller 35. When the peripheral speed of the intermediate roller 35 is set slower than that of the developing roller 36 as described above, the angle θdr formed by the developer pattern on the image carrier 10 is formed by the developer pattern on the intermediate roller 35. It becomes smaller than the angle θmr to perform.

FIG. 14 is a diagram in the case where the peripheral speed of the intermediate roller 35 is higher than the peripheral speed of the developing roller 36. In this case, the angle θdr formed by the developer pattern on the image carrier 10 is larger than the angle θmr formed by the developer pattern on the intermediate roller 35.

FIG. 15 is a diagram for quantitatively explaining the angle formed by the developer pattern on the image carrier 10. As shown in the figure, the peripheral speed of the intermediate roller 35 is Vmr, the forming angle is θmr, the peripheral speed of the developing roller 36 is Vdr, and the forming angle is θdr. The amount Lmr applied by the intermediate roller 35 per unit time is equal to the amount Ldr applied by the developing roller 36 per unit time, and the distance d between the contact surfaces of the intermediate roller 35 and the developing roller 36 coincides.
Vdr · tan θdr = Vmr · tan θmr
The angle θdr formed by the developer pattern on the developing roller 36 is
tanθdr = Vmr / Vdr · tanθmr
It can ask for.

  FIG. 16 shows various numerical values used in this embodiment applied to the above relationship. When the peripheral speed Vmr of the developing roller is fixed at 250 [mm / s] and the peripheral speed Vdr of the intermediate roller 35 is varied in the range of 200 to 250 [mm / s], the angle θdr formed by the developer pattern is , And fluctuates in the range of 39 to 55 [°].

  FIG. 17 is a diagram showing the variation of the angle θdr formed by this developer pattern. As described above, when the angle θdr formed by the developer pattern fluctuates, the developer pattern is arranged so that the imaginary line of the optical sensor 21 is not within this angle range and the direction of the developer stripe. In addition, the developer streak can be detected with high accuracy. Even in this case, it is possible to further improve the detection accuracy by providing a margin of ± 5 [°] in the angle range and the developer stripe direction.

  The variation of the developer pattern formation angle θdr generated by adjusting the coating amount on the developing roller 36 has been described above, but the adjustment of the coating amount on the developing roller 36 is not limited to this embodiment. For example, it is good also as changing the peripheral speed ratio of the intermediate | middle roller 35 and the supply roller 34, or changing the peripheral speed ratio of all the rollers. Even in these cases, the developer pattern forming angle θdr varies, but in this case as well, the imaginary line of the optical sensor 21 may be arranged so as not to fall within the variation range.

  FIG. 18 is a diagram illustrating a part of an image forming apparatus according to another embodiment of the present invention. The developing unit 30 described so far includes three rollers, a supply roller 34, an intermediate roller 35, and a developing roller 36. In contrast to the system, in the present embodiment, the supply roller 34 is a two-roller system that directly contacts the developing roller 36. In the three-roller system, the liquid developer is sufficiently kneaded at the contact portion of each roller, so that a uniform developer film can be formed on the developing roller 36, but the present invention adopts this two-roller system. It may be adopted.

  Also in this embodiment, it is possible to detect image unevenness with high accuracy by adopting the arrangement of the optical sensor 21 in consideration of the developer pattern and the developer stripe direction described above. Further, when adjusting the amount of the liquid developer supplied to the developing roller 36, the peripheral speed ratio between the developing roller 36 and the supply roller 34 may be adjusted. In this case, as in the case of the three-roller system, the optical sensor 21 is disposed in consideration of the developer pattern angle θdr.

  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 unit 36 ... developing roller (developer carrier), 361 ... developing roller cleaning unit, 37 ... toner charger (charging member),
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 (8)

Development having a developer storage part for storing a liquid developer having toner and carrier liquid, a supply member having a groove in the first direction, and a developer carrier for supporting the liquid developer supplied by the supply member And
An image carrier that carries an image developed in the developing unit;
A light emitting unit that emits light to the image of the image carrier, a first light receiving unit that receives light emitted from the light emitting unit and reflected by the image, and a position different from the first light receiving unit. An optical sensor having a second light receiving unit that receives light emitted from the light emitting unit and reflected by the image;
An imaginary line connecting the light emitting unit and the first light receiving unit is different from the first direction of the groove and the moving direction of the image carrier.   2. The image formation according to claim 1, wherein the light emitting unit and the first light receiving unit are disposed at a position where an incident angle of light emitted from the light emitting unit is equal to a reflection angle of light reflected from the image. apparatus.   The image forming apparatus according to claim 1, wherein the second light receiving unit is disposed vertically above a position where light from the light emitting unit is incident on the image.   The developing unit includes a second supply member that contacts the supply member and the developer carrier and supplies the liquid developer supplied from the supply member to the developer carrier. The image forming apparatus according to any one of the above.   The image forming apparatus according to claim 4, further comprising a control unit that changes a peripheral speed ratio between a peripheral speed of the image carrier and a peripheral speed of the second supply member.   The image forming apparatus according to claim 1, wherein the supply member is in contact with the developer carrying member.   The image forming apparatus according to claim 6, further comprising a control unit that changes a peripheral speed ratio between a peripheral speed of the image carrier and a peripheral speed of the supply member. Supplying the liquid developer stored in the developer storage section to the developer carrier with a supply member having a groove in the first direction;
Developing the latent image formed on the image carrier using the liquid developer supplied to the developer carrier,
Using the optical sensor having a light emitting unit and a first light receiving unit arranged in a direction different from the first direction and the moving direction of the image carrier, the light emitting unit is applied to the developed image of the image carrier. 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 second light receiving unit disposed at a position different from the first light receiving unit. An image forming method.

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