JP2011170143A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the quality of print images by preventing the generation of non-uniform images. <P>SOLUTION: An image forming apparatus includes: an image carrier 10 for carrying an image developed by a developing section 30; an optical sensor 21, having a light emitting section 210 for emitting light to the image on the image carrier 10; a first light-receiving section 211 for receiving light reflected by the image, and a second light-receiving section 212, disposed at a place different from the first light-receiving section 211; and a control section for adjusting the bias applied to a developer carrier 36 by an output signal from the first light-receiving section 211 and for controlling a bias applied to a squeeze member 13 by an output signal from the second light-receiving section 212. <P>COPYRIGHT: (C)2011,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. The toner particles are very fine particles having a particle diameter of about 1 μm, and can achieve higher image quality than a conventional dry image forming apparatus using a particle diameter of 7 μm.
As an image forming apparatus using such a liquid developer, for example, in Patent Document 1, a patch pattern is printed in order to cope with changes in image density due to environmental changes and toner characteristic changes, and the density is referred to. An image forming method for changing printing conditions is disclosed.

JP 2008-170602 A

In an image forming apparatus using a liquid developer, it has been found that when the liquid developer is transferred from the developing roller to the photoconductor, image unevenness on the vertical stripes called a riblet (about 500 μm to 1 mm) occurs. . This is caused by fluidly unstable splitting when the liquid developer passes between the developing roller and the photoreceptor, and is an image unevenness unique to the liquid developing method that does not occur in the dry developing method.
In order to prevent such image unevenness, printing conditions such as charging conditions and development conditions are initially optimized and the printer is shipped. However, when the viscosity of the developer changes due to a change in environmental temperature, the fluid characteristics of the liquid developer may change and image unevenness may occur. In addition, the fluid characteristics may change due to the change of the liquid developer over time, which may cause image unevenness.
However, although the prior art can correct the image density based on the patch density reference, it cannot detect the image unevenness and prevent it. In particular, even if the image density is corrected to be constant, image unevenness occurs in some cases, or image unevenness hardly occurs in some cases, resulting in a print quality disorder. Even if there is no noticeable image unevenness, the gloss of the printed matter changes due to the change in the film state of the liquid developer formed on the paper. .
In order to prevent such image unevenness, the present invention presents a method for detecting image unevenness as a voltage signal and optimizing printing conditions based on the reference information.

The image forming apparatus of the present invention squeezes a developer carrying member carrying a liquid developer, an image carrying member carrying an image developed from the developer carrying member, and an image carried on the image carrying member. A squeeze member, a light emitting unit that emits light to the image of the image carrier, a first light receiving unit that receives light reflected by the image, and a second light receiving unit disposed at a position different from the first light receiving unit. The bias applied to the developer carrier is adjusted by an optical sensor having a light receiving portion and the output signal of the first light receiving portion, and the bias applied to the squeeze member is adjusted by the output signal of the second light receiving portion. And a control unit.
According to this configuration, it is possible to quantitatively detect image unevenness by the optical sensor, and by performing bias control based on the detection signal, it is possible to keep the image density constant and to prevent occurrence of image unevenness. Can be prevented.

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 light is scattered light.
According to this configuration, the amount of light absorbed by the toner varies depending on the image density, and the magnitude of the specularly reflected light component varies, so that the image density can be detected by the first light receiving unit. In addition, when the image unevenness increases, the unevenness of the toner image increases, and the scattering component increases, so that the second light receiving unit can detect the image unevenness.

Further, in the image forming apparatus of the present invention, the control unit increases the bias applied to the developer carrier when the output signal of the first light receiving unit is larger than the upper limit of the reference range, When the output signal of the light receiving unit is smaller than the lower limit of the reference range, developer carrier bias adjustment is performed to reduce the bias applied to the developer carrier.
According to this configuration, when the specular reflection light is large (when the image density is small), if the voltage of the developing roller is increased accordingly, the amount of toner transferred to the photoreceptor increases, and the image density can be kept within a predetermined range. On the other hand, when the specular reflection light is small (when the image density is high), if the developing roller voltage is decreased accordingly, the amount of toner transferred to the photoreceptor is reduced, and the image density can be kept within a predetermined range. By doing so, the image density can be kept constant.

Furthermore, in the image forming apparatus of the present invention, the control unit increases a bias applied to the squeeze member when the output signal of the second light receiving unit is larger than an upper limit of a reference range, and the second light receiving unit When the output signal is smaller than the lower limit of the reference range, squeeze member application bias adjustment is performed to reduce the bias applied to the squeeze member.
According to this configuration, in the case of large scattered light (in the case of large image unevenness), when the voltage of the squeeze member is increased, the toner images are appropriately aggregated to be smooth and reduce image unevenness. Further, when the scattered light is small (when the image unevenness is small), the voltage of the squeeze member is decreased to reduce the electric field strength applied to the toner in order to prevent toner aggregation more than necessary by the squeeze member. By doing so, it is possible to prevent image unevenness while preventing toner aggregation.

Furthermore, in the image forming apparatus of the present invention, the controller performs the developer carrier applied bias adjustment and the squeeze member applied bias adjustment every time a predetermined number of recording materials are printed.
In this way, the above control is performed for every fixed number of printed sheets during a print job, so that there is no image unevenness and a constant image density can be maintained.

Furthermore, in the image forming apparatus according to the present invention, the control unit includes a bias to be applied to the developer carrier used last and a squeeze member when a predetermined time or more has not elapsed since the end of previous printing. Printing is started using a bias applied to the.
As described above, by reusing the previous value, it is possible to simplify the control and to maintain the quality of the image.

In the image forming method of the present invention, the latent image formed on the image carrier is developed using the liquid developer carried on the developer carrier, and the developed image of the image carrier is applied to the light emitting portion. The first light receiving unit receives the light reflected by the image and the second light receiving unit disposed at a position different from the first light receiving unit. The bias applied to the developer carrying member is adjusted by the output signal of the first light receiving unit, and the bias applied to the squeeze member is adjusted by the output signal of the second light receiving unit. .
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 showing the main configuration of an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view illustrating main configurations of an image forming unit and a developing unit according to Embodiment 1 of the present invention. The figure which shows the optical sensor which concerns on Embodiment 1 of this invention. The figure which shows the relationship between the state of a developer layer, and reflected light. The figure which shows the relationship between the state of a developer layer, and reflected light. The figure which shows the relationship between the state of a developer layer, and reflected light. The figure which shows the relationship between the state of a developer layer, and reflected light. FIG. 3 is a diagram illustrating control of the image forming apparatus according to the first embodiment of the invention. FIG. 3 is a flowchart showing control of the image forming apparatus according to the first embodiment of the present invention. 3 is a table used for control of the image forming apparatus according to the first exemplary embodiment of the present invention. The figure which shows the relationship between a developing roller voltage and a regular reflection light received signal. The figure which shows the relationship between a squeeze roller voltage and a scattered light received signal. FIG. 3 is a flowchart showing control of the image forming apparatus according to the first embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the main configuration of the image forming apparatus according to the present invention will be described. 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 on the upper part of 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 transported through the sheet material transport 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. Further, 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 where the intermediate transfer body 40 is stretched on the tension roller 42. 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 developing roller 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 a low-temperature (1 to 2 wt%) and low-viscosity room temperature using Isopar (registered trademark) (ExxonMobil Corporation) as a carrier, which is generally used conventionally. Is not a volatile liquid developer having high volatility, 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 is used as an organic solvent, silicon oil A liquid developer having a high viscosity (about 30 to 10,000 mPa · s) added to a liquid solvent such as mineral oil or edible oil together with a dispersant and having a toner solid content concentration of about 20%.

  The supply roller 34 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 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 is a cylindrical member, and rotates counterclockwise like the developing roller 36 and counter-contacts with the developing roller 36 as shown in FIG. 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 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 member 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 excessive development of the toner image developed on the image carrier 10 is performed. 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 It comprises an image carrier squeeze roller cleaning unit 14 that contacts and cleans the surface, and has the function of collecting 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 collected liquid storage unit.

  Next, an optical sensor for detecting image density and image unevenness in the present invention will be described with reference to FIG. FIG. 3 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. 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.

  In order to explain these detection principles in more detail, FIGS. 4 to 8 show the relationship between the state of the developer layer on the substrate and the magnitudes of specular reflection light and scattered light. FIG. 4 shows a case where the developer layer is thin and the surface of the developer layer is smooth (when the image density is low and image unevenness is small). In this case, since the developer layer is thin, light absorption in the developer layer is reduced, and specular reflection light is increased. Further, since the surface of the developer layer is smooth, light scattering on the developer surface is reduced, and scattered light is reduced.

  FIG. 5 shows a case where the developer layer is thick and the surface of the developer layer is smooth (when the image density is high and image unevenness is small). In this case, since the developer layer is thick, light absorption in the developer layer increases, and specular reflection light decreases. Further, since the surface of the developer layer is smooth, light scattering on the developer surface is reduced, and scattered light is reduced.

  FIG. 6 shows the case where the developer layer is thin and the surface of the developer layer has large irregularities (when the image density is thin and the image unevenness is large). In this case, since the developer layer is thin, light absorption in the developer layer is reduced, and specular reflection light is increased. Further, since the unevenness of the surface of the developer layer is large, the scattering of light on the surface of the developer is increased, and the scattered light is increased.

  FIG. 7 shows a case where the developer layer is thick and the surface of the developer layer has large irregularities (when the image density is high and image unevenness is large). In this case, since the developer layer is thick, light absorption in the developer layer increases, and specular reflection light decreases. Further, since the unevenness of the surface of the developer layer is large, the scattering of light on the surface of the developer is increased, and the scattered light is increased. As described above, the image density and the image unevenness can be detected by the relationship between the state of the developer layer shown in FIGS. 4 to 7 and the intensity of the specular reflection light and the scattered light.

  Next, image density control will be described. The image density varies due to changes in the surrounding environment such as temperature and developer deterioration. In order to obtain a good printed image, it is necessary to appropriately adjust the image density. In this embodiment, the image density on the image carrier 10 is detected by the optical sensor 21, and the voltage (bias) applied to the developing roller 36 is adjusted to keep the image density constant.

  Since the transfer rate of the developer from the developing roller 36 to the image carrier 10 is proportional to the voltage applied to the developing roller 36, the voltage applied to the developing roller 36 is adjusted to adjust the voltage applied to the image carrier 10. It is possible to control the coating amount of the liquid developer. In the present embodiment, by changing the voltage applied to the developing roller 36 to 200 to 400 [V], the transfer rate from the developing roller 36 to the image carrier 10 can be changed to 60 to 90 [%] (at the time of solid printing). The image density can be adjusted.

  Specifically, when the specularly reflected light signal received by the first light receiving unit 211 is large, that is, when the image density is small, the application amount is increased by increasing the voltage applied to the voltage power supply 27 to increase the image density. Let On the other hand, when the specularly reflected light signal received by the first light receiving unit is small, that is, when the image density is large, the voltage applied to the voltage power supply 27 is lowered to reduce the coating amount and reduce the image density. . In addition, when the voltage applied to the developing roller 36 is changed, the grid voltage of the toner charger 37 is also increased by the amount that the voltage of the developing roller 36 is changed in order to make the charge amount by the toner charger 37 constant. Need to change.

  Next, image unevenness control will be described. Similar to the image density, the image unevenness also varies due to changes in the surrounding environment such as temperature and developer deterioration. In order to obtain a good printed image, it is necessary to appropriately adjust this image unevenness. In the present embodiment, the image density on the image carrier 10 is detected by the optical sensor 21 and the voltage (bias) applied to the image carrier squeeze roller 13 is adjusted to suppress image unevenness.

  The image carrier squeeze roller 13 collects the excess developer of the toner image developed on the image carrier 10 as described above, and further compresses the toner image developed on the image carrier 10 toward the photoreceptor. It has. By compressing the toner image, the toner image becomes smooth and image unevenness can be reduced. As the voltage (bias) applied to the image carrier squeeze roller 13 is increased, the compression force increases and image unevenness is reduced.

  When the voltage applied to the image carrier squeeze roller 13 is small, the force for compressing the toner image toward the photosensitive member becomes weak, and image unevenness is likely to occur. On the other hand, when the voltage applied to the image carrier squeeze roller 13 is large, the force for compressing the toner image toward the photosensitive member becomes strong and image unevenness is less likely to occur. However, if the voltage applied to the image carrier squeeze roller 13 is increased too much, the toner adheres strongly to the photoconductor and the primary transfer efficiency is lowered. Therefore, the image carrier is appropriately moderated as necessary to suppress the occurrence of image unevenness. It is necessary to maintain the voltage applied to the body squeeze roller 13.

  The present invention aims to improve the quality of an image printed using the relationship between the voltage applied to the image carrier squeeze roller 13 and the occurrence of image unevenness. FIG. 8 is a diagram showing an example of an apparatus for controlling the voltage applied to the developing roller 36 and the voltage applied to the image carrier squeeze roller 13 based on the signal of the optical sensor 21 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 image carrier squeeze roller 13, but after passing through the image carrier squeeze roller 13 and before passing through the primary transfer unit 50. It is good as well.

  Now, control of the image forming apparatus according to the embodiment of the present invention will be described with reference to FIGS. FIG. 9 is a flowchart showing control of the image forming apparatus, FIG. 10 is a table used for control of the image forming apparatus, and FIG. 11 is a diagram showing the relationship between the developing roller voltage and the regular reflection light signal. FIG. 12 is a diagram showing the relationship between the squeeze roller voltage and the scattered light reception signal.

  In the flowchart of FIG. 9, when printing is started (S100), first, in S101, the application amount, that is, the voltage applied to the developing roller 36 and the voltage of the image carrier squeeze roller 13 are initial values. It 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 to the control unit 23 as a control signal for a voltage power source 27 for controlling the voltage applied to the developing roller 36 and a voltage for the image carrier squeeze roller 13. It is converted into a control signal of the voltage power supply 25 to be controlled.

  Now, control of image density in the present embodiment will be described. FIG. 11 is a diagram showing the relationship between the regular reflection light signal and the developing roller voltage. A reference range including an optimum value is set for the regular reflection light signal. In this embodiment, if the regular reflection light signal is within this reference range, the image density is appropriate, and the voltage applied to the developing roller 36 is controlled so that the regular reflection light signal is within the reference range.

  When the specular 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 voltage power supply 27 is changed so as to increase the voltage of the developing roller 36. On the other hand, if the specular 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 voltage power source 27 is changed so as to lower the voltage of the developing roller 36.

  In the present embodiment, when the specular reflected light signal exceeds the upper limit of the reference range, the voltage applied to the developing roller 36 is increased by 5 [V], and when the specular reflected light signal falls below the lower limit of the reference range, the developing roller The voltage applied to 36 is lowered by 5 [V]. Further, in order to make the charge amount by the toner charger 37 constant, the grid voltage of the toner charger 37 is also changed by the amount that the voltage applied to the developing roller 36 is changed.

  Next, image unevenness control in the present embodiment will be described. FIG. 12 is a diagram showing the relationship between the scattered light signal and the voltage of the image carrier squeeze roller 13. A reference range including an optimum value is set for the scattered light signal. In this embodiment, if the scattered light signal is within this reference range, the image unevenness is within the allowable range, and the voltage of the image carrier squeeze roller 13 is controlled so that the scattered light signal is within the reference range.

  When 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 voltage of the image carrier squeeze roller 13. On the other hand, when the scattered light signal falls below the lower limit of the reference range, the control signal for the voltage power supply 25 is changed so as to lower the voltage of the image carrier squeeze roller 13 in order to avoid toner sticking to the photoreceptor. In the present embodiment, when the scattered light signal exceeds the upper limit of the reference range, the voltage of the squeeze roller is increased by 5 [V], and when the scattered light signal falls below the lower limit of the reference range, the voltage of the squeeze roller is increased by 5 [V]. It is possible to suppress image unevenness while avoiding toner sticking to the photosensitive member by lowering by V].

  FIG. 10 shows a table used for control of the control unit 23 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.

  Thus, in this embodiment, the optical sensor 21 detects the regular reflection signal of the image to detect the image density, and controls the bias applied to the developing roller 36 voltage so as to keep the image density constant. Yes. In addition, the optical sensor 21 detects the scattered light signal of the image to detect image unevenness, and the bias applied to the voltage of the image carrier squeeze roller 13 is controlled so as to suppress it. In this way, it is possible to perform high-quality image formation with a constant image density and no image unevenness.

  Next, the second adjustment processing according to the embodiment of the present invention will be described with reference to FIG. In the present embodiment, the second adjustment process is a process performed in S101 of FIG. 9 when a predetermined time or more has elapsed since the end of the previous printing, and is more accurately developed than the adjustment process of FIG. In this process, the voltage applied to the roller 36 and the voltage applied to the voltage of the image carrier squeeze roller 13 are adjusted.

  In the second adjustment process, first, an initial value of the voltage applied to the developing roller 36 is determined at 301. In the present embodiment, these initial values are the values at the end of the previous time. Steps S <b> 302 to S <b> 305 are development voltage control steps. In this embodiment, the application amount of the liquid developer is brought close to the optimum value by adjusting the voltage applied to the development roller 36.

  In this developing voltage control step, first, in S302, the voltage applied to the developing roller 36 is reduced by a predetermined amount from the initial value (30 [V] in this embodiment). In step S303, a test image is printed outside the image area of the image carrier 10. As this test image, a solid image (solid patch) or a grid-like image (screen patch) is used as in S104 of FIG.

  In S304, 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 voltage is lower, the current voltage to be applied to the developing roller 36 is determined as a value used for actual control, and the developing roller voltage control process is terminated. On the other hand, if it is determined that the voltage is not lower, the voltage applied to the developing roller 36 and the grid voltage of the toner charger 37 are increased by a predetermined amount in S305 (both 5 V in this embodiment). ]), And returns to S303.

  Thus, in this step, after the voltage applied to the developing roller 36 is once lowered, the optimum voltage of the developing roller 36 is searched by increasing it by a predetermined amount. In the present embodiment, the optimum voltage is searched while increasing the voltage, but the optimum value may be searched while decreasing.

  When the specularly reflected light signal falls below the optimum value in S304 and the voltage to be applied to the developing roller 36 is determined, the process proceeds from S306 to the squeeze voltage control process in S309. In this step, as in the development voltage control step, an optimum control value is searched for by sequentially shifting the control value by a predetermined amount.

  In this squeeze voltage control step, first, in S306, the voltage of the image carrier squeeze roller 13 is reduced by a predetermined amount from the initial value (in this embodiment, 30 [V]). Next, in S307, a test image is printed outside the image area of the image carrier 10 as in S303. In S308, 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 voltage of the image carrier squeeze roller 13 is adopted as a value used for control, and the squeeze voltage control step is terminated.

  On the other hand, if it is determined that the voltage is not lower, the voltage of the image carrier squeeze roller 13 is increased by a predetermined amount in S309 (in this embodiment, 5 [V]), and the process returns to S307. As described above, in this step, the voltage of the image carrier squeeze roller 13 is temporarily lowered from the initial value, and then the voltage of the image carrier squeeze roller 13 is sequentially shifted by a predetermined amount to optimize the image carrier. The voltage of the body squeeze roller 13 is searched. In this squeeze voltage control step, the optimum value may be searched while the voltage of the image carrier squeeze roller 13 is lowered.

  The second adjustment process according to the embodiment of the present invention has been described above. In the second adjustment process, the voltage applied to the developing roller 36 and the voltage of the image carrier squeeze roller 13 are determined. By separately performing the squeeze voltage control step to be determined, it is possible to perform the adjustment with higher accuracy than the adjustment process described with reference to FIG.

  In addition, the second adjustment process of this embodiment is performed in the order of the development voltage control process and the squeeze voltage control process, but may be performed in the order of the squeeze voltage control process and the development voltage control process. In the present embodiment, the amount to be sequentially shifted is set as a fixed predetermined amount. However, the predetermined amount is changed after being below the optimum value or approaching the optimum value (for example, the squeeze voltage). In some cases, the process may be made closer to the optimum value by lowering 5 [V] to 1 [V].

  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 212 212 Second light receiving unit 30. Developing unit 31. Developer container 311 Developer storing unit 34. 36, developing roller (developer carrier), 361 developing roller cleaning unit, 37 toner charger, 40 intermediate transfer member, 41 drive roller, 42 tension roller, 46 intermediate transfer member cleaning unit, 50: primary transfer portion, 51: primary transfer backup roller, 61: secondary transfer roller, 62: secondary transfer roller clear Training unit.

Claims (7)

A developer carrying member carrying a liquid developer;
An image carrier for carrying an image developed from the developer carrier;
A squeeze member for squeezing the image carried on the image carrier;
A light-emitting unit that emits light to the image of the image carrier; a first light-receiving unit that receives 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;
A control unit that adjusts a bias applied to the developer carrier by an output signal of the first light receiving unit, and adjusts a bias applied to the squeeze member by an output signal of the second light receiving unit;
An image forming apparatus comprising:   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 1.   When the output signal of the first light receiving unit is larger than the upper limit of the reference range, the control unit increases the bias applied to the developer carrier, and the output signal of the first light receiving unit is lower than the lower limit of the reference range. 2. The image forming apparatus according to claim 1, wherein the developer carrying member bias adjustment is performed to reduce a bias applied to the developer carrying member.   The control unit increases the bias applied to the squeeze member when the output signal of the second light receiving unit is larger than the upper limit of the reference range, and the output signal of the second light receiving unit is smaller than the lower limit of the reference range. 2. The image forming apparatus according to claim 1, wherein, when the squeeze member is small, squeeze member application bias adjustment is performed to reduce a bias applied to the squeeze member.   The image according to any one of claims 1 to 4, wherein the control unit performs the developer carrier application bias adjustment and the squeeze member application bias adjustment each time a predetermined number of recording materials are printed. Forming equipment.   The control unit starts printing using a bias applied to the developer carrier used last and a bias applied to the squeeze member when a predetermined time or more has not elapsed since the end of previous printing. The image forming apparatus according to any one of claims 1 to 5. The latent image formed on the image carrier is developed using the liquid developer carried on the developer carrier,
Light is emitted from the light emitting portion 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 comprising: adjusting a bias to be applied to the developer carrying member based on an output signal of the first light receiving portion; and adjusting a bias to be applied to the squeeze member based on an output signal of the second light receiving portion. .

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