JP2007286112A - Control roller, one-component developing device using it, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control roller for preventing the occurrence of irregularity of a toner conveying amount and a charge amount by reducing pressure irregularity of the surface of the control roller using a foamed body layer, and to provide a one-component device using it and an image forming apparatus. <P>SOLUTION: The control roller 24 arranged in contact with a developing roller 22 of the one-component developing device 20 has a foamed elastic body layer 26 formed of a foamed elastic body, and a tube 27 arranged thereon. Hardness measured from the outer face of the tube 27 is 80 degrees or less at Asker FP, and a weight required for obtaining a prescribed push amount by an indenter from the outer face of the tube 27 of the foamed elastic body layer 26 is 1.5 times or more of a weight required for obtaining the similar push amount by the indenter from the outer face of the foamed elastic body layer 26. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a one-component developing device using one-component toner, a regulating roller used for the same, and an image forming apparatus having the one-component developing device. More specifically, the present invention relates to a regulating roller as a regulating member that regulates and measures the amount of toner on the developing roller and charges the toner, and a one-component developing device and an image forming apparatus using the regulating roller.

  Conventionally, in a one-component developing device in an electrophotographic image forming apparatus, a regulating member is brought into contact with a developing roller that supplies toner to an image carrier to regulate and measure the amount of toner. Further, the toner is charged by friction when the toner passes through the nip between the developing roller and the regulating member. As such a restricting member, a flat plate-like restricting blade has been widely used. However, the restricting blade has a problem that the progress of wear is relatively fast and the toner is easily aggregated.

  Particularly in recent years, as the toner particle size is reduced, the surface area of the toner per unit amount increases, so that the amount of the external additive added to the toner per unit amount tends to increase. For this reason, the toner is pressed against the developing roller by the contact pressure of the restricting member, and the rate of occurrence of detachment of the external additive or embedding in the base material is increased. As a result, there has been a problem that the charging characteristics and fluidity of the toner change.

  In addition, the introduction of full-color machines in offices and other places where the frequency of monochrome printing is relatively high has led to continuous monochrome printing on full-color machines. In such a method of use, the number of times or time that pressure is applied to the toner on the developing roller increases in the developing device other than for black toner. For this reason, in the toners of the respective colors other than black, the change in toner characteristics tends to be further increased.

On the other hand, as a regulating member, a developing device having a roller-like regulating roller having a metal cylindrical cored bar and an elastic foam layer formed on the outer periphery thereof is disclosed (for example, see Patent Document 1). .) Further, a developing device is disclosed that includes a metal cylindrical cored bar and an elastic foam layer formed on the outer periphery thereof, and further includes a regulating roller covered with a tube on the outer periphery thereof (for example, Patent Documents). 2). According to such a restricting member, it is said that a wide restricting nip can be secured while reducing the pressure applied to the toner, durability can be improved, and a long life can be achieved.
JP 2004-29357 A JP 2004-85623 A

  However, since the elastic foam layer is used to reduce the pressure in the regulation roller of the conventional developing device described above, the surface of the layer has irregularities peculiar to the foam. Therefore, there is a possibility that minute pressure unevenness occurs on the surface of the regulating roller, and unevenness occurs in the toner transport amount and the charge amount. In the developing device described in Patent Document 2, a tube is further coated on the outer periphery of the elastic foam layer. However, this tube is considerably thin and pressure unevenness cannot be sufficiently prevented. Furthermore, if pressure unevenness occurs at the contact position between the regulating roller and the developing roller, unevenness may occur in the toner conveyance amount and the charge amount, and as a result, there is a risk of causing image quality deterioration such as unevenness in image density and graininess. There was a problem that there was.

  The present invention has been made to solve the problems of the conventional developing device described above. That is, the subject is a regulation roller that can reduce pressure unevenness on the surface of the regulation roller using the foam layer, and can prevent occurrence of unevenness in toner conveyance amount and charge amount, and one-component development using the regulation roller An apparatus and an image forming apparatus are provided.

  In order to solve this problem, the restriction roller of the present invention is a restriction roller disposed in contact with the developing roller of the one-component developing device, and includes a roller member formed of a foamed elastic body and a roller member. The hardness measured from the outer surface of the tube is 80 degrees or less with the Asker FP, and the load required to obtain a predetermined pushing amount from the outer surface of the tube with the indenter is the same from the outer surface of the roller member. This is 1.5 times or more the load required to obtain the indentation amount with the indenter.

  The regulating roller of the present invention has a roller member formed of a foamed elastic body and a tube disposed on the roller member. Since the hardness measured from the outer surface of the tube is relatively soft and 80 degrees or less with Asker FP, the stress applied to the toner is relatively small. Furthermore, since the load required to obtain a predetermined pushing amount from the outer surface of the tube with the indenter is 1.5 times or more than the load required to obtain the same pushing amount from the outer surface of the roller member, the roller member The pressure non-uniformity on the outer surface is reduced. Therefore, it is a regulating roller that can reduce pressure unevenness on the surface of the regulating roller using the foam layer, and can prevent occurrence of unevenness in the toner conveyance amount and the charging amount.

  The present invention is also a one-component developing device having a developing roller and a regulating roller disposed in contact with the developing roller, the regulating roller being disposed on the roller member formed of a foamed elastic body, and the roller member The hardness measured from the outer surface of the tube is 80 degrees or less with the Asker FP, and the load required to obtain the same amount of pressing with the developing roller from the outer surface of the tube with the indenter is a roller member. This also extends to a one-component developing device that is 1.5 times or more the load required to obtain the same amount of pushing from the outer surface of the sheet.

  The present invention also includes a photosensitive member and a one-component developing device that develops the photosensitive member. The one-component developing device is an image forming apparatus that includes a developing roller and a regulating roller disposed in contact with the developing roller. The regulating roller has a roller member formed of a foamed elastic body and a tube disposed on the roller member, and the hardness measured from the outer surface of the tube is 80 degrees or less with an Asker FP. In an image forming apparatus, the load required to obtain the same pushing amount from the outer surface with the indenter with the indenter is 1.5 times or more than the load required to obtain the same pushing amount from the outer surface of the roller member with the indenter. It also extends.

  According to the regulating roller of the present invention and the one-component developing device and the image forming apparatus using the regulating roller, the pressure unevenness on the surface of the regulating roller using the foam layer is reduced, and the unevenness of the toner conveyance amount and the charging amount is prevented. can do.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to a so-called tandem color printer.

  The color printer 10 of this embodiment is a so-called tandem image forming apparatus in which image forming units 11Y, 11M, 11C, and 11K for four colors are arranged along the intermediate transfer belt 12, as shown in FIG. . The color printer 10 further includes a paper feeding device 13, an exposure device 14, a belt transfer device 15, and a fixing device 16. As shown by a dotted line in FIG. 1, the apparatus forms and discharges an image while conveying a sheet. Since this image forming operation is a general one, its description is omitted here.

  Each of the image forming units 11Y, 11M, 11C, and 11K includes the photoreceptors 17Y, 17M, 17C, and 17K, and cleaners 18Y, 18M, 18C, and 18K arranged around the photosensitive members 17Y, 17M, 17C, and 17K, and charging devices 19Y, 19M, 19C, and 19K. Devices 20Y, 20M, 20C, and 20K. Each color device has the same configuration, and in the following description, the YMCK suffix is omitted.

  As schematically shown in FIG. 2, the developing device 20 of the present embodiment is provided with a toner storage unit 21 that stores toner T, and a developing roller 22, a supply roller 23, and a regulating roller 24 provided therein. The developing roller 22, the supply roller 23, and the regulating roller 24 are all arranged with their axial directions parallel to each other, and are rotated as indicated by arrows in the drawing. The developing roller 22 is disposed so as to face the photoconductor 17. The developing device 20 is a one-component developing device that uses one-component toner.

The developing roller 22 has a conductive elastic layer formed on a metal shaft. The resistivity of the elastic layer is such that the resistance value between the metal shaft and the conductor in contact with the roller surface is 10 ⁸ Ω or less. The supply roller 23 has a conductive foamed elastic layer formed on a metal shaft. The resistivity of the foamed elastic layer is such that the resistance value between the metal shaft and the conductor in contact with the roller surface is 10 ⁵ Ω or less. The developing roller 22 and the supply roller 23 are brought into contact with each other and rotated counter. Here, the outer diameter of the developing roller 22 is 16 mm, and the outer diameter of the supply roller 23 is 12 mm. The outer diameter of the photoconductor 17 is φ30 mm.

As shown in FIG. 3, the regulating roller 24 has a foamed elastic layer 26 formed on the outer periphery of the metal shaft 25, and further has a tube 27 on the outer periphery thereof. The foamed elastic body layer 26 is a cylindrical foam layer made of a urethane material, and the tube 27 is an unfoamed elastic layer made of a polyamide material. The tube 27 is bonded to the foamed elastic layer 26 with a conductive adhesive. The resistivity of the foamed elastic layer 26 is such that the resistance value between the metal shaft 25 and the conductor in contact with the surface of the tube 27 is 10 ⁵ Ω or less. This foamed elastic layer 26 corresponds to a roller member.

  In addition, the regulating roller 24 is arranged to be pushed into the developing roller 22 by a predetermined pushing amount (here, 1 mm). Further, as shown by an arrow in FIG. Here, as the dimensions of each part of the regulating roller 24, the outer diameter is φ12 mm, the outer diameter of the metal shaft 25 is φ5 mm, and the thickness of the tube 27 is 100 μm.

  Here, the regulation roller 24 of this embodiment is formed so that its hardness is 80 degrees or less in Asker FP. Further, the tube 27 is selected so that the indentation load when the indenter is pressed against the outer surface of the regulating roller 24 and the indentation is pushed to a predetermined pushing amount satisfies the following condition. That is, it is set to 1.5 times or more of the indentation load required for indenting only the foamed elastic layer 26 without the tube 27 by the same indentation amount. Here, the predetermined pushing amount may be the same pushing amount as the pushing amount to the regulating roller 24 by the developing roller 22.

  Next, a method for measuring the indentation load will be described. As shown in FIG. 4, the hardness measuring machine 30 for measuring the indentation load has a support base 32 for horizontally supporting the regulating roller 24 and a load measuring column 33 fixed on a base 31. ing. Further, a load measuring unit 37 having a load meter 34, an indenter 35, and a dial 36 is attached to the column 33. The load measuring unit 37 is moved up and down along the column 33 by turning the dial 36. The indenter 35 has a circular shape with a diameter of about 20 mm at least on the lower surface in FIG.

  In the measurement of the indentation load by the hardness measuring device 30, first, the regulation roller 24 to be measured is fixed to the support base 32. Then, the dial 36 is operated so that the indenter 35 comes into contact with the surface of the regulating roller 24. Up to this point, the value indicated by the load meter 34 is zero. And the dial 36 is further operated to the position below 1 mm from there, and the load measurement part 37 is moved. The load value indicated by the load meter 34 at this time is read. Similarly, in the state before the tube 27 is bonded to the regulating roller 24, that is, in the case where only the elastic foam layer 26 is formed on the metal shaft 25 (hereinafter referred to as a tubeless roller), the 1 mm indentation load is similarly applied. Measure. Here, the reason why the distance is set to 1 mm is that the pushing amount when the regulating roller 24 is arranged with respect to the developing roller 22 is 1 mm.

  Thus, the result measured about various rollers is shown in FIG. Each of the regulating rollers A to E in FIG. 5 is different in the material and foaming conditions of the foamed elastic layer or the material and thickness of the tube. In any case, the column (a) shows the indentation load (N) when the regulating roller having a tube is used. The column (b) shows the pushing load (N) of the tubeless roller having no tube. The column (a) / (b) shows the ratio between (a) and (b). Furthermore, the “image quality” column shows the image quality when an image is formed using a color printer in which each roller is incorporated as a regulating roller 24. The image quality was evaluated by visual observation of density unevenness of the solid image and graininess of the halftone image.

  As shown in FIG. 5, an image with good image quality can be obtained if the ratio between (a) and (b) is 1.5 or more, regardless of the flexibility of the regulating roller 24 and the elastic foam layer 26 itself. Was found to be obtained. By selecting a pair of the foamed elastic layer 26 and the tube 27 that satisfies this condition, the pressure unevenness due to the uneven shape on the surface of the foamed elastic layer 26 is not transmitted to the surface of the tube 27.

  Next, the hardness of the regulating roller 24 will be described. The hardness was measured with a FP type durometer hardness meter for each of the regulation rollers having different materials and foaming conditions for the foamed elastic layer, or the material and thickness of the tube. The results of measuring the hardness of various rollers are shown in FIG. Further, using a color printer in which each roller is incorporated as a regulating roller 24, the change in characteristics of two types of toners was examined.

The method for measuring the change in toner characteristics is as follows. First, 6000 sheets of A4 size continuous paper were printed with a color printer incorporating each roller. This is a condition in which stress is most repeatedly applied to the toner. After that, the state of the toner was examined, and the case where the change in characteristics was at a level that affected the image quality was marked as x. In the two types of toners (toner α and toner β), the toner α has a volume average particle size of 6.5 μm and a SiO ₂ throughput of 1.7, and the toner β has a volume average particle size of 5.5 μm and SiO 2. _{2 The} throughput is 2.5. In both cases, the initial filling amount into the toner storage unit was 100 g.

  The rotation speed of each part of the color printer 10 was 180 rpm for the developing roller 22, 240 rpm for the supply roller 23, 240 rpm for the regulating roller 24, and 64 rpm for the photoconductor 17. As shown in FIG. 6, in the restriction roller (G, H) having a hardness of Asker FP and greater than 80 degrees, the toner characteristic change is large, and when normal image formation is performed after the above-mentioned printing with durability, Degradation in image quality such as a decrease in image density and fogging of the background occurs. From this, it was found that the restriction roller 24 of this embodiment preferably has a hardness of 80 degrees or less in Asker FP.

  In the developing device 20 of this embodiment, the toner T in the toner storage unit 21 is conveyed to the vicinity of the developing roller 22 by the rotation of the supply roller 23 and is supplied to the surface of the developing roller 22. The toner on the developing roller 22 is scraped off at the contact portion between the developing roller 22 and the regulating roller 24, so that the amount of toner thin layer is regulated and made uniform. The toner layer is further charged by receiving friction between the developing roller 22 and the regulating roller 24.

  Here, since the regulation roller 24 of the present embodiment has a hardness of 80 degrees or less in Asker FP, the pressure applied to the toner is small, and the deterioration of the image quality due to the change in the characteristics of the toner is prevented. Further, since the regulating roller 24 has a tube 27 on the outer periphery of the foamed elastic layer 26 and the ratio of the indentation load with the tubeless roller is 1.5 times or more, the surface of the foamed elastic layer 26 is Even if there are irregularities, the irregularities hardly appear on the surface of the tube 27. Therefore, minute pressure unevenness on the surface of the regulating roller 24 is prevented, and there is no possibility of unevenness in the toner conveyance amount and the charge amount.

  In this way, the toner layer that is uniformly thinned to a predetermined amount and charged to a predetermined charge amount faces the photoconductor 17 by the rotation of the developing roller 22. Further, the electrostatic latent image is developed by moving to the photosensitive member 17 in the developing region which is the closest portion between the developing roller 22 and the photosensitive member 17. Further, the toner remaining on the developing roller 22 even after passing through the developing region is scraped off by the supply roller 23 and returned to the toner storage unit 21.

  As described above in detail, according to the developing device 20 of the color printer 10 of the present embodiment, the regulating roller 24 has the tube 27 on the outer periphery of the foamed elastic layer 26 and has a hardness of 80 degrees in Asker FP. Therefore, the pressure applied to the toner is small, and the ratio of the indentation load with the roller without tube is 1.5 times or more, so that minute pressure unevenness on the roller surface is prevented. Accordingly, the developing device 20 can reduce the pressure unevenness on the surface of the regulating roller using the foam layer and prevent the unevenness of the toner conveyance amount and the charge amount.

  In addition, this form is only a mere illustration and does not limit this invention at all. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the outer diameter of each roller, the rotation direction, the rotation speed, the size and material of each part of the regulating roller, the pushing amount of the regulating roller, the potential condition of the regulating roller and the supply roller, the type of toner, etc. are all examples. Not limited to this. Further, the metal shaft 25 of the regulating roller may be cylindrical. In this embodiment, a color printer is used. However, the present invention can also be applied to an electrophotographic image forming apparatus such as a copying machine or a FAX.

1 is a cross-sectional view illustrating a schematic configuration of a color printer according to an embodiment. It is sectional drawing which shows schematic structure of the developing device which concerns on this form. It is sectional drawing which shows a control roller. It is a block diagram which shows schematic structure of a hardness measuring machine. It is a graph which shows the indentation load with respect to a control roller and a roller without a tube, and the relationship between those ratios and image quality. 6 is a chart showing the relationship between the hardness of a regulating roller and a change in toner characteristics during printing durability.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Color printer 20 Developing device 22 Developing roller 24 Regulating roller 26 Foam elastic layer (roller member)
27 tubes

Claims (3)

In the regulating roller arranged in contact with the developing roller of the one-component developing device,
A roller member formed of a foamed elastic body;
A tube disposed on the roller member;
The hardness measured from the outer surface of the tube is 80 degrees or less in Asker FP,
The load required to obtain a predetermined pushing amount from the outer surface of the tube with an indenter is 1.5 times or more than the load required to obtain a similar pushing amount from the outer surface of the roller member with the indenter. Regulatory roller. In the one-component developing device having a developing roller and a regulating roller disposed in contact with the developing roller, the regulating roller includes:
A roller member formed of a foamed elastic body;
A tube disposed on the roller member;
The hardness measured from the outer surface of the tube is 80 degrees or less in Asker FP,
The load required to obtain the same amount of pushing with the indenter from the outer surface of the tube with the indenter is 1.5 times or more than the load required to obtain the same amount of pushing with the indenter from the outer surface of the roller member. A one-component developing device. An image forming apparatus comprising: a photosensitive member; and a one-component developing device that develops the photosensitive member, wherein the one-component developing device includes a developing roller and a regulating roller disposed in contact with the developing roller. The regulation roller
A roller member formed of a foamed elastic body;
A tube disposed on the roller member;
The hardness measured from the outer surface of the tube is 80 degrees or less in Asker FP,
The load required to obtain the same amount of pushing with the indenter from the outer surface of the tube with the indenter is 1.5 times or more than the load required to obtain the same amount of pushing with the indenter from the outer surface of the roller member. An image forming apparatus, comprising:

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