JP2005266234A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of replenishing the appropriate quantity of toner even in the case of forming an image on a sheet other than a normal sheet, regarding the image forming apparatus for forming the image on the sheet with the toner. <P>SOLUTION: The image forming apparatus (1) is provided with an image forming part (13) for forming a latent image on the surface of a photoreceptor, developing the latent image by using developer containing the toner of nearly fixed concentration and transferring the toner as a developed image from the photoreceptor to the sheet, and a toner replenishing part (20) for replenishing the toner to the developing part of the image forming part (13). In the image forming apparatus (1), whenever the image is formed on the sheet, the quantity of toner to be replenished is calculated based on the number of dots presenting the formed image, further, the calculated quantity of toner to be replenished is corrected in accordance with the kind of the sheet on which the image is formed, then, the toner is replenished. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that forms an image on a sheet with toner.

  There are various image forming methods employed in image forming apparatuses such as copiers and printers that form images on sheets, but the most common way is to represent images with toner. In this method, the surface of the photoconductor is irradiated with light to form a latent image of the image, the toner is attached to the surface of the photoconductor on which the latent image is formed and developed, and the toner is transferred from the surface of the photoconductor to the sheet. By transferring, an image is formed on the sheet. Thereafter, the toner is fixed on the sheet.

  In such an image forming apparatus that forms an image with toner, it is common to use a two-component developer composed of toner and carrier, and the toner concentration in the developer is kept substantially constant. Conventionally, plain paper has been used as an image forming sheet, and development with toner has been performed under certain conditions. For example, in order to move the toner from the developing unit to the surface of the photoconductor, the bias voltage applied between the developing unit and the photoconductor is constant. Thus, an image having a constant density can be formed on a sheet using a developer having a constant toner density.

  Since the toner is consumed by image formation, it is necessary to replenish the toner appropriately in order to keep the toner density constant. Various methods are employed to determine an appropriate amount of toner to be replenished.

For example, in Japanese Patent Laid-Open No. 2000-250275, each time an image is formed on a sheet, the number of dots representing the image is obtained, and toner is supplied to the developing unit by an amount proportional to the obtained number of dots. In this method, an appropriate toner replenishment amount can be obtained even if the amount of toner consumed varies depending on the size of the image and the blank ratio in the image.
JP 2000-250275 A

  In recent years, there is a growing demand to form an image on not only plain paper but also thick paper or an OHP sheet (a resin transparent sheet used in an overhead projector). In order to form an image with an appropriate density on a sheet other than plain paper while using a developer having a substantially constant toner density, development conditions such as a bias voltage applied between the developing unit and the photoconductor are set on the plain paper. The amount of toner consumed varies even when the same image is formed. In particular, when an image is formed on a transparent OHP sheet, the amount of toner consumption increases because the image is darker than when an image is formed on plain paper.

  Although the method of the above publication is simple and useful, the toner replenishment amount is obtained based only on the number of dots. Therefore, when an image is formed on a sheet different from plain paper, the obtained replenishment amount is not always appropriate. This is not always the case, and the toner density in the developing unit tends to fluctuate.

  The present invention has such has been made in view of the problems, even when an image is formed on other than plain paper sheet, and an object thereof is to provide an image forming apparatus capable of supplying the toner of the appropriate amount .

  In order to achieve the above object, in the present invention, a latent image representing an image is formed, and the latent image is developed by attaching the toner to the latent image using a developer containing toner having a substantially constant density. the an image forming apparatus for forming an image on a sheet by transferring to a sheet, together with changing the development conditions depending on the type of the image formation sheet, the toner in order to maintain the toner density of the developer substantially constant in those replenished to the developer, based on the number of dots representing the formed image to calculate the amount of toner replenished to the developer, to correct the replenishing amount of the toner is calculated according to the type of the sheet to form an image To.

  The image forming apparatus is based on the number of dots forming the image obtaining the toner supply amount, not only to, the replenishment amount calculated, is corrected in accordance with the type of the sheet to form an image. Therefore, the toner density of the developer can be kept constant not only when an image is formed on plain paper but also when an image is formed on a sheet other than plain paper.

  The image forming apparatus of the present invention, when an image is formed on the non-plain-paper sheet also, it is possible to replenish the developer the toner proper amount, is always possible to form an image of appropriate density is there.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The configuration of the image forming apparatus 1 of the present embodiment is schematically shown in FIG. The image forming apparatus 1 includes an image reading unit 11, document transport section 12, image forming section 13, sheet feeding unit 14, an image fixing unit 15, the sheet discharge unit 16, operation unit 17, display unit 18, a communication unit 19, the toner A replenishing unit 20 and a control / processing unit 21 are provided.

  The image reading unit 11 reads an image from a document. The document conveying unit 12 conveys the document to a position where the image reading unit 11 reads an image. The image forming unit 13 forms an image on a sheet with toner. The sheet supply unit 14 supplies a sheet on which an image is formed to the image forming unit 13. The image fixing unit 15 fixes the image formed on the sheet by the image forming unit 13, that is, the toner adhering to the sheet, to the sheet. The sheet discharge unit 16 discharges the sheet after image fixing.

  The operation unit 17 is operated by a user and receives an instruction regarding image formation. The display unit 18 displays the state of the image forming apparatus 1, information related to image formation, operation guidance, and the like. The display unit 18 displays the types and sizes of sheets that can be supplied by the sheet supply unit 14, and the user selects a desired one from among them and designates it from the operation unit 17. Sheet feeding unit 14, when the type and size of the sheet is designated to supply the sheet as specified in the image forming unit 13, when the type and size of the sheet is not specified, the original size The plain paper corresponding to the above is supplied to the image forming unit 13.

  The communication unit 19 is connected to a LAN cable 19a and communicates with a personal computer on a LAN (local area network). The communication unit 19 is also connected to a public telephone line 19b and communicates with an external facsimile machine. The toner supply unit 20 supplies toner to the image forming unit 13. The control / processing unit 21 controls the overall operation of the image forming apparatus 30 through the control of each unit described above, and performs image processing necessary for image formation.

  In FIG. 1, the conveyance of a white sheet is shown, and a thick arrow indicates toner supply. In addition, thin arrows indicate data and control signals.

  The configuration of the image forming unit 13 is schematically shown in FIG. The image forming unit 13 includes a photosensitive drum 131, a charging unit 132, an exposure unit 133, a developing unit 134, a transfer unit 135, a cleaning unit 136, and a charge eliminating unit 137. The photoconductive drum 131 has a photoconductive layer whose charging potential is changed by light on the surface, and rotates in the direction of arrow A. The charging unit 132 charges the surface of the photosensitive drum 131 by discharging, and the exposure unit 133 irradiates the surface of the photosensitive drum 131 with the laser light L to change the potential of the irradiated part, thereby changing the potential of the photosensitive drum 131. A latent image representing an image is formed on the surface.

  The developing unit 134 holds a developer composed of toner and carrier, and develops the latent image by attaching the toner to the latent image formed on the surface of the photosensitive drum 131. The toner concentration of the developer is kept substantially constant. In the image forming apparatus 1 that can form an image on a sheet other than plain paper, the development conditions are changed in accordance with the type of the sheet on which the image is formed. For example, in order to move the toner to the surface of the photosensitive drum 131, the bias voltage applied between the developing unit 134 and the photosensitive drum 131 is changed according to the type of sheet.

  Transfer section 135, as shown by the arrow B, and along the rotational direction of the photosensitive drum 131, the sheet S conveyed between the photosensitive drum 131, adhering to the surface of the photosensitive drum 131 The toner representing the image is transferred to form an image on the sheet S. The cleaning unit 136, a toner remaining after transfer is removed from the surface of the photosensitive drum 131, a discharge unit 137, in preparation for the next charging by the charging unit 132 neutralizes the surface of the photosensitive drum 131.

  The image processing apparatus 1 including the image reading unit 11, the image forming unit 13, and the communication unit 19 has functions as a copying machine, a printer, a facsimile machine, and an image scanner. The function as a copying machine is realized by reading an image from a document by the image reading unit 11 and forming the read image on a sheet by the image forming unit 13. Functions as a printer, receives data representing an image from a personal computer on the LAN by a communication unit 19, the control / processing unit 21 applies processing to the received data, the image of the image data after processing represents forming unit 13 This is realized by forming on a sheet.

  The function as a facsimile apparatus is that an image is read from an original by the image reading unit 11, the read image is transmitted to an external facsimile apparatus by the communication unit 19, and an image is received from the external facsimile apparatus by the communication unit 19 and received. This is realized by forming the formed image on a sheet by the image forming unit 13. The function as an image scanner is realized by reading an image from a document by the image reading unit 11 and transmitting the read image to a personal computer on the LAN by the communication unit 19.

  Each time an image is formed, the toner in the developing unit 134 is consumed. In the image forming apparatus 1, in order to keep the toner density of the developing unit 134 constant, toner is supplied from the toner supplying unit 20 to the developing unit 134 every time an image is formed on a sheet. The control / processing unit 21 performs control for this purpose.

  The amount of toner consumed by forming an image varies depending on the size of the formed image and the proportion of blanks included in the formed image. Therefore, the image forming apparatus 1 calculates the number of dots representing the formed image, and calculates the toner replenishment amount based on the calculated number of dots. The number of dots of an image can be obtained from image data.

  The amount of toner consumed by the image formation varies depending on the development conditions. In the image forming apparatus 1, the development conditions are set according to the type of the sheet, and thus vary depending on the type of the sheet. Therefore, the image forming apparatus 1 corrects the toner replenishment amount calculated based on the number of dots of the image according to the type of the sheet used. That is, when forming the sheet to the image consumption is large toner than plain paper by increasing the supply amount of toner, the toner replenishment amount when forming the sheet to the image is smaller toner consumption than plain paper Reduce. Thus, the toner concentration of the developer in the developing unit 134 is always kept constant regardless of the type of sheet on which the image is formed. Therefore, even when image formation is continuously performed on sheets other than plain paper, an image with a constant density can be formed thereafter.

  Control / processing unit 21 has a memory 21a that stores parameters used for controlling and processing, the correspondence between the type and current conditions of the sheet, and also the correspondence between the correction value of the sheet type and the toner supply amount, It is stored in the memory 21a. Control / processing unit 21, in the control of development, to select the developing condition corresponding to the type of sheet specified by the user via the operating unit 17, also in the control of the toner supply, the operating unit 17 The toner replenishment amount is determined using a correction amount corresponding to the sheet type designated by the user.

  A flow of toner replenishment processing in the image forming apparatus 1 is shown in FIG. First, the number of dots of the formed image is obtained (step # 5). Next, based on the obtained number of dots, the toner replenishment amount when the sheet on which the image is formed is plain paper is calculated (# 10). Further, it is determined whether or not the sheet on which the image is actually formed is plain paper (# 15).

  When the sheet on which the image is actually formed is plain paper, toner is supplied from the toner supply unit 20 to the developing unit 134 by the supply amount calculated in step # 10 (# 25). On the other hand, when actually sheets forming the image is not plain paper, depending on the type of the sheet, the calculated supply amount corrected in step # 10 (# 20), only the corrected supply amount, the toner supply The toner is supplied from the unit 20 to the developing unit 134 (# 25).

  In this embodiment, the number of dots representing an image is obtained from the image data. However, an image actually formed on a sheet is read, and the number of dots included in the read image is counted. May be. However, this requires a means for reading the image formed on the sheet in addition to the image reading unit 11 for reading the image from the document, which complicates the configuration. Therefore, the number of dots is obtained from the image data. Is preferred.

  The formation of the image consumes some of the developer carrier as well as the toner. Therefore, when a certain number of images are formed, it is necessary to replace the developer or supply the carrier. When loading both toner and carrier, the toner density is different, that is, providing a ratio of toner and carrier two different developer for replenishment, depending on the amount of toner and carrier remaining in the developing unit By determining the ratio of the two types of developer to be replenished, the toner density in the developing portion can be kept constant. Even in this case, it is preferable to calculate the supply amount of two types of developer based on the number of dots of the formed image, and to correct the calculated supply amount according to the type of sheet on which the image is formed.

1 is a block diagram schematically showing the configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a side view schematically showing a configuration of an image forming unit of the image forming apparatus. 6 is a flowchart showing a flow of toner supply processing of the image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Image reading part 12 Document conveying part 13 Image forming part 131 Photosensitive drum 132 Charging part 133 Exposure part 134 Developing part 135 Transfer part 136 Cleaning part 137 Electric discharge part 14 Sheet supply part 15 Image fixing part 16 Sheet discharge part 17 Operation Unit 18 Display Unit 19 Communication Unit 20 Toner Supply Unit 21 Control / Processing Unit

Claims (1)

A latent image representing an image is formed, the toner is attached to the latent image using a developer containing toner having a substantially constant density, the latent image is developed, and the image is formed on the sheet by transferring the toner to the sheet. An image forming apparatus that changes development conditions according to the type of sheet on which an image is formed and supplies toner to the developer in order to keep the toner concentration of the developer substantially constant.
An image forming apparatus that calculates a toner replenishment amount based on the number of dots representing a formed image and corrects the toner replenishment amount calculated according to the type of sheet on which the image is formed.

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