JP2006071837A - Toner concentration measuring mechanism for liquid developing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner concentration measuring mechanism for a liquid developing apparatus, capable of highly accurately measuring toner concentration in developer without causing soil on the surface of an optical sensor. <P>SOLUTION: The developer L is transferred/supplied from a developer supply part 21 to a pattern roller 33 through a draw-up roller 34. The developer L is applied from the pattern roller 33 to the developing roller 32, then, the developer is stuck to a photoreceptor drum 11, and an image is developed in accordance with an electrostatic latent image. The optical sensor 44 is arranged according to the toner layer of the pattern roller 33. A transparent protecting pipe 47 is attached to the outer circumferential side of the optical sensor 44 so that it can be rotated by a motor. A cleaning blade 55 is brought in contact with the outer circumferential surface of the rotating protecting pipe 47, then, the developer sticking to the outer circumferential surface of the pipe is cleaned before the developer becomes dry and firmly sticks to the outer circumferential surface of the pipe. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a toner concentration measuring mechanism in a liquid developing device.

  In general, a liquid developing device forms an electrostatic latent image by irradiating the surface of a photosensitive drum with light according to image information, and a developer including toner particles and a carrier is formed on the electrostatic latent image. Is adhered by a developing roller to form a toner image on the photosensitive drum. On the outer peripheral surface of the developing roller, the developer stored in the developer storage container is applied by a drawing roller and a pattern roller.

  In the liquid developing device, a toner concentration measuring mechanism is provided in order to adjust the toner concentration of the developing solution to ensure an appropriate image density, and the developer storing is based on the measured value of the toner concentration measured by the measuring mechanism. The toner density in the container is adjusted.

As the toner density measuring mechanism, a mechanism disclosed in Patent Document 1 has been proposed. This toner density measuring mechanism is configured such that a reflecting roller is brought into rolling contact with a pattern roller having a pattern groove in which a lower half portion is immersed in a developing solution of a developing solution (liquid toner). The developer is transferred to the surface. In addition, light is irradiated from the irradiation part of the optical sensor toward the toner layer formed on the surface of the reflection roller, the reflected light is received by the light receiving part, and the change in the amount of received light is converted into an electric quantity. What has been proposed is proposed.
JP 2003-270959 A

  The optical sensor is provided with a light irradiating part and a light receiving part arranged side by side, and the irradiation light depends on the amount of light received by the light receiving part as reflected from the surface of the reflecting roller. In order to read such subtle changes, it is necessary to always keep the surface of the optical sensor clean and unstained. Further, when the developer adheres to the surface of the optical sensor and dries, there is a problem that the adhesion is strong and it is difficult to sufficiently clean.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a toner concentration measuring mechanism in a liquid developing device that can accurately measure the toner concentration of a developing solution without fouling the surface of an optical sensor.

  In order to solve the above problem, the invention according to claim 1 is a toner concentration measuring mechanism in a liquid developing device that measures a toner concentration of a developer composed of toner particles and a carrier by a light projecting / receiving optical sensor. The gist of the invention is that a transparent protective member is interposed between the optical sensor and a toner layer carrier that carries the developer as a toner layer, and a cleaning means for cleaning the surface of the protective member is provided.

The gist of a second aspect of the present invention is that, in the first aspect, the protection member is configured to be movable by a movement mechanism.
A third aspect of the present invention is the protective pipe according to the first aspect, wherein the protective member covers the optical sensor and is rotatably disposed at a predetermined position by a rotation mechanism. The gist is that a cleaning blade or a cleaning brush as a cleaning means is in contact with the outer peripheral surface.

  A fourth aspect of the present invention provides the pattern groove according to any one of the first to third aspects, wherein the toner layer carrier carries, as a toner layer, a developer transferred and supplied from a developer supply unit by a pumping roller. The gist of the present invention is that the developing solution is transferred from the pattern roller to the developing roller, and the developing solution is transferred from the developing roller to the photosensitive member.

  According to the present invention, a transparent protective member is interposed between the optical layer and the toner layer carrier that carries the developer as a toner layer, and cleaning means for cleaning the surface of the protective member is provided. Thus, the surface of the optical sensor can be prevented from being soiled. Also, since the developer adhering to the protective member can be reliably cleaned by the cleaning means before it dries and strongly adheres, the protective member is always kept in a clean state from the optical sensor to the surface of the toner layer carrier. It is possible to appropriately transmit the irradiation light and the reflected light applied to the toner, and improve the measurement accuracy of the toner concentration of the developer.

  Hereinafter, an embodiment in which the toner concentration measurement mechanism of the developer of the present invention is embodied in a liquid developing device used in a tandem color image forming apparatus (hereinafter simply referred to as a wet image forming apparatus) will be described with reference to the drawings. To do.

  FIG. 1 is a schematic configuration diagram showing one liquid developing device among a plurality of liquid developing devices constituting a wet image forming apparatus. This liquid developing device includes a photosensitive drum 11 as an image carrier, a main charging device 12, an LPH (LED PRINT HEAD) 13, a liquid developing device 14, a transfer unit 15, a cleaning unit 17, and a charge eliminating lamp 18. By assembling it in the housing made in this way, it becomes a single unit and can be attached to an apparatus main body (not shown).

  The photosensitive drum 11 is an amorphous silicon drum and is charged by the main charging device 12 so that the dark potential at the developing position is about 300V. The LPH 13 irradiates light according to image information onto the surface of the charged photosensitive drum 11, thereby forming an electrostatic latent image on the surface of the photosensitive drum 11.

  The liquid developer 14 uses a developer L composed of toner particles and a carrier with stirring and mixing so as to have a predetermined concentration. The developer L is irradiated with light from the photosensitive drum 11 by a developing roller 32 described later. The toner image is formed (developed image) on the photosensitive drum 11 by applying to the electrostatic latent image of the portion. The dark potential of the photosensitive drum 11 is set to 300V, the developing bias is set to 200V, and the post-exposure potential is set to 20V. That is, the dark potential corresponds to the white portion of the image, the post-exposure potential corresponds to the black portion of the image, and this difference is a so-called contrast potential. The toner image developed (developed) of the electrostatic latent image formed as described above is transferred to an intermediate transfer belt 16 of a belt conveying unit (not shown) at the nip with the transfer unit 15. The transfer means 15 uses a transfer roller in this embodiment, and a voltage having a polarity opposite to the surface potential of the photosensitive drum 11 is set in a range of −200 to −1300 V and applied. .

  Further, the photosensitive drum 11 is neutralized by the neutralizing lamp 18 so as to reduce the residual potential on the surface and make it uniform, and thereafter, it is prepared for the next series of processes. The potential setting for image formation in this manner varies depending on the characteristics of the photosensitive drum 11, the performance of the toner particles, and the environment. The wet image forming apparatus is a method similar to the above liquid developing apparatus that develops an image corresponding to black on a photosensitive drum, and another three types of liquid developing apparatuses are used to generate images corresponding to magenta, cyan, and yellow. A full-color image is formed by developing on the drum and sequentially and repeatedly transferring on the intermediate transfer belt 16 without deviation.

Next, a specific configuration of the liquid developing device 14 will be described with reference to FIG.
The liquid developing device 14 according to the present embodiment schematically includes a developing solution supply unit 21 and a developing unit 22 for transferring the developing solution supplied by the developing solution supply unit 21 to the photosensitive drum 11. The developing unit 22 and a developer toner concentration measuring mechanism 23 provided corresponding to the developing unit 22 are configured. Therefore, the configurations of the developer supply unit 21, the developing unit 22, and the toner density measuring mechanism 23 will be described in order below.

  The developer supply unit 21 includes a developer storage container 25 that forms a developer storage chamber 24 that stores the developer L. In the developer storage container 25, an upstream stirring screw 26 and a downstream stirring screw 27 as stirring members are rotatably supported at predetermined positions. The upstream stirring screw 26 and the downstream stirring screw 27 are rotated by a rotation drive mechanism (not shown).

  Accordingly, the upstream and downstream agitating screws 26 and 27 are rotated in opposite directions by the rotation drive mechanism (not shown), and the developer L stored in the developer storage container 25 is moved upstream and downstream. Stirring and mixing are performed by the stirring screws 26 and 27.

  Next, the developing unit 22 will be described. The developing unit 22 includes a storage case 31 that is bonded and fixed to the upper end opening of the developer storage container 25. A developing roller 32 as a developer carrying member that is in rolling contact with the outer peripheral surface of the photosensitive drum 11 is supported on the upper portion of the housing case 31. A pattern roller 33 that is in rolling contact with the outer peripheral surface of the developing roller 32 is supported on the housing case 31. Similarly, a pumping roller 34 that is in contact with the pattern roller 33 is rotatably supported in the housing case 31, and the developer L is transferred from the developer storage chamber 24 to the pattern roller 33.

  As shown in FIGS. 2 and 3, a pattern groove 33a is formed on the outer peripheral surface of the pattern roller 33, and the developer L is attached to the pattern groove 33a by the pumping roller. The pattern grooves 33a are formed in a plurality of locations in an annular shape in the circumferential direction of the pattern roller 33 and at an equal pitch in the axial direction, but are illustrated as one groove in FIG. A doctor blade 35 is brought into contact with the outer peripheral surface of the pattern roller 33 to remove excess developer L protruding from the pattern groove 33a, and the toner layer T having a predetermined thickness is measured in the pattern groove 33a. It comes to adhere. The housing case 31 is provided with a cleaning blade 36 for removing residual developer that has not been transferred from the pattern roller 33 to the developing roller 32. In this embodiment, the pattern roller 33 is a toner layer carrier.

  The housing case 31 is provided with a cleaning blade 37 for removing the excess developer on the developing roller 32 that has not been transferred to the photosensitive drum 11, and for discharging the removed excess developer to the outside. A discharge screw 38 is provided. The developing roller 32, the pattern roller 33, the drawing roller 34, the discharge screw 38, and the like are rotationally driven in a direction indicated by an arrow in FIG. 1 by a drive motor (both not shown) through a drive transmission mechanism including a gear train and the like.

The developer L is adjusted so that the toner particles are dispersed at a high concentration in a carrier made of a nonpolar insulating liquid such as silicone oil.
The pattern roller 33 applies a developing solution L onto the developing roller 32 to form a thin layer of the developing solution L on the developing roller 32. In the developing area on the photosensitive drum 11, the latent image is developed by the developer L.

Next, the developer concentration measuring mechanism 23 will be described.
As shown in FIG. 3, the housing case 31 supports fixed support shafts 41 and 42 parallel to the pattern roller 33, and a sensor holder is formed by bending a plate material into a flat U-shape between the support shafts. Both ends of 43 are connected. An optical sensor 44 is attached to the sensor holder 43. The optical sensor 44 includes an irradiation unit 45 that irradiates measurement light toward the toner layer T formed in the pattern groove 33a of the pattern roller 33, and a light receiving unit 46 that receives the measurement light reflected by the toner layer T. Is provided. The optical sensor 44 converts the change in the amount of measurement light (changed according to the toner density) irradiated and reflected from the irradiation unit 45 onto the surface of the toner layer T of the pattern roller 33, thereby converting the toner in the toner layer T to an electric signal. Concentration is measured.

  The fixed support shafts 41 and 42, the sensor holder 43, and the optical sensor 44 are protected by a protective pipe 47 as a transparent protective member formed in a cylindrical shape by, for example, a glass tube or an acrylic resin pipe. A boss portion 48 a of a flange 48 that is rotatably supported on the fixed support shaft 41 is fitted and fixed to one end portion of the protective pipe 47. A boss 49a of a gear 49 that is rotatably supported on the fixed support shaft 42 is fitted and fixed to the other end of the protective pipe 47.

  A motor 51 is attached to the outer surface of the housing case 31 via a bracket 50, and a gear 53 that meshes with the gear 49 is attached to a rotating shaft 52 of the motor 51. In this embodiment, the rotation mechanism of the protective pipe 47 is constituted by the flange 48, the gear 49, the motor 51, the gear 53, and the like. As shown in FIG. 2, the housing case 31 is provided with a cleaning blade 55 as a cleaning means made of, for example, rubber or synthetic resin for removing the developer attached to the outer peripheral surface of the protective pipe 47. . The cleaning blade 55 may be disposed over the entire length of the protective pipe 47 or locally at a position corresponding to the optical sensor 44.

Next, the operation of the developer concentration measuring mechanism 23 will be described.
At the same time as the developing solution supply unit 21 and the developing unit 22 are operated and the developing operation for applying the developing solution L to the photosensitive drum 11 is started, the optical sensor 44 and the motor 51 of the toner concentration measuring mechanism 23 are activated. . Then, the protective pipe 47 is rotated clockwise in FIG. 1 by the motor 51 via the gear 53 and the gear 49. For this reason, the developer L adhering to the outer peripheral surface of the protective pipe 47 is scraped off and reliably cleaned before being dried by the cleaning blade 55 and strongly adhering to the protective pipe 47. Further, since the protective pipe 47 is rotated for cleaning, the optical sensor 44 itself can be cleaned at all times as compared with cleaning when not measuring. Accordingly, the irradiation unit 45 and the light receiving unit 46 of the optical sensor 44 are always kept clean by the protection pipe 47, and the outer peripheral surface of the protection pipe 47 is always kept clean by the cleaning blade 55, and the measurement light protection pipe Since the attenuation due to contaminants when passing through 47 is prevented, the toner concentration of the toner layer T of the pattern roller 33 can be accurately measured.

  Note that the supply amounts of the high-concentration toner and the carrier respectively stored in two containers (not shown) to the developer storage container 25 are adjusted based on the measured values of the toner concentration, and the toner concentration in the developer storage container 25 is adjusted. Is adjusted to an appropriate value.

In addition, you may change the said embodiment as follows.
Although not shown, instead of the protective pipe 47, a protective plate is supported between the pattern roller 33 and the optical sensor 44 so as to be reciprocable by a moving mechanism, and a cleaning blade 55 is provided on the surface of the protective plate on the pattern roller 33 side. You may make it contact.

In place of the cleaning blade 55, a cleaning brush may be used.
The toner density of the toner layer applied to the drawing roller 34 or the developing roller 32 may be measured by the toner density measuring mechanism 23.

  In the above embodiment, the protective pipe 47 is rotated by the dedicated motor 51. Instead, the protective pipe 47 is rotated by a driving motor that drives the developing roller 32, the pattern roller 33, and the pumping roller 34. It may be.

FIG. 3 is a cross-sectional view of a liquid developing device provided with a developer toner concentration measuring mechanism of the present invention. FIG. 3 is an enlarged cross-sectional view illustrating a toner concentration measurement mechanism. FIG. 3 is a plan sectional view of a toner concentration measuring mechanism.

Explanation of symbols

  L ... developer, T ... toner layer, 21 ... developer supply unit, 32 ... developing roller, 33 ... pattern roller as toner layer carrier, 33a ... pattern groove, 34 ... pump roller, 55 ... cleaning as cleaning means Blades 44... Optical sensors 47. Protection pipes as protection members.

Claims (4)

In a toner concentration measuring mechanism in a liquid developing device that measures a toner concentration of a developer composed of toner particles and a carrier by a light projecting / receiving optical sensor,
A liquid developer comprising a transparent protective member interposed between a toner layer carrier that carries the developer as a toner layer and the optical sensor, and a cleaning means for cleaning the surface of the protective member. A toner density measuring mechanism in the apparatus. 2. The toner concentration measuring mechanism according to claim 1, wherein the protective member is configured to be movable by a moving mechanism. 2. The protective pipe according to claim 1, wherein the protective member is a protective pipe that covers the optical sensor and is rotatably arranged at a predetermined position by a rotation mechanism, and a cleaning means serving as a cleaning unit is disposed on an outer peripheral surface of the protective pipe. A toner concentration measuring mechanism in a liquid developing device, wherein a blade or a cleaning brush is in contact. The toner layer carrier according to any one of claims 1 to 3, wherein the toner layer carrier is a pattern roller having a pattern groove that bears, as a toner layer, a developer transferred and supplied from a developer supply unit by a scooping roller. A toner concentration measuring mechanism in a liquid developing device, wherein a developing solution is transferred from a pattern roller to a developing roller, and the developing solution is transferred from the developing roller to a photosensitive member.

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