JP2007206412A - Image forming apparatus and control method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic image forming apparatus, using two-component developer comprising of toner and carrier, wherein unevenness in print density is not generated, until the toner runs out, even if the ability to supply toner is degraded, as a result of the decrease in the quantity of residual toner, and to provide a control method therefor. <P>SOLUTION: The image forming apparatus includes an image memory 102 that takes in image data to be printed; an ROM 104 storing, for example, the absolute value of the ability to supply toner; a printing rate calculating means 106 by which the printing rate of the image data taken in the image memory 102 is calculated for each page; a toner consumption quantity calculating means 107 for calculating the quantity of toner consumption based on, for example, the print proportion calculated by the printing rate calculating means 106; a residual toner quantity calculating means 108 for calculating the quantity of residual toner from the quantity of each toner consumption; and a printing speed setting means 109 for setting the printing speed. When the ability of the toner supply device to supply toner, which is obtained from the quantity of remaining toner, has become degraded, the printing speed is switched to a low side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus using a two-component developer composed of a toner and a carrier, and a printing speed control method thereof.

  In an electrophotographic image forming apparatus in which an electrostatic latent image formed on the surface of a photoreceptor is visualized as a toner image by a developing device and then transferred to a predetermined sheet, a two-component system generally including toner and a carrier is used. A developer is used, and it is necessary to maintain the toner concentration in the developing device within a predetermined range in order to perform the visualization appropriately.

By the way, in an image forming technique in which a two-component developer is used, a replaceable toner cartridge that is used by being attached to a toner replenishing device generally has a unit when the remaining amount of toner decreases. Since the amount of toner discharged per hour decreases, the toner replenishment amount from the toner replenishing device cannot be kept constant, and the toner density in the developing tank can be maintained within a predetermined range even at a normal printing speed. There is a problem that it becomes impossible.

  FIG. 4 shows the relationship between the rotation time of the toner supply motor (the amount of rotation of the toner cartridge) and the toner discharge amount of the toner cartridge for a standard rotary type toner cartridge used by being mounted on the toner supply device. 2 shows toner discharge characteristics of a toner cartridge. As can be seen from FIG. 4, the remaining amount of toner decreases linearly until the rotation time of the toner motor reaches 30 minutes, that is, the toner discharge amount per unit time is constant. However, when the rotation time exceeds 30 minutes, the toner remaining amount curve becomes gentle, that is, the amount of toner discharged per unit time decreases. As a result, even with a normal printing rate document, if the printing speed is constant, the toner density cannot be maintained within a predetermined range, and the printing density varies in the middle of the job.

As a technique for preventing print density unevenness from occurring in print quality, for example, there is a technique disclosed in Patent Document 1. However, in this prior art, the toner replenishment amount per unit time is decreased from the steady replenishment amount until the toner concentration detected by the toner concentration sensor reaches a predetermined concentration after the start of toner replenishment. It does not correspond to the above-mentioned problem caused by the decrease in the remaining amount.
Japanese Patent Laid-Open No. 7-12018

  The present invention has been made to solve the above-described problems. In an image forming technique using a two-component developer, the toner replenishing capability of the toner replenishing device is reduced by reducing the remaining amount of toner in the toner cartridge. An object of the present invention is to provide an image forming apparatus and a printing speed control method thereof capable of printing with a constant print quality without density unevenness until just before the toner runs out even if the toner drops.

The present invention is constituted by the following technical means in order to solve the above-described problems.
The first technical means includes: a latent image carrier comprising a photosensitive drum; a developing device that stirs toner and carrier to supply a two-component developer to the surface of the latent image carrier; and a replaceable toner cartridge. A toner supply device for discharging toner and supplying toner to the developing device;
An image forming apparatus including an image memory to which image data to be printed is input and a control unit, wherein the control unit performs printing when the toner replenishing capability of the toner replenishing device becomes a predetermined value or less. The speed is switched to a low speed.

  The second technical means is characterized in that, in the first technical means, the timing for switching the printing speed is set to one job unit.

  According to a third technical means, in the first or second technical means, the remaining amount of toner is calculated based on image data input to the image memory.

  According to a fourth technical means, in any one of the first to third technical means, the toner cartridge is a rotary toner bottle.

  A fifth technical means includes: a latent image carrier comprising a photosensitive drum; a developing device that stirs toner and carrier to supply a two-component developer to the surface of the latent image carrier; and a replaceable toner cartridge. A printing speed control method for an image forming apparatus, comprising: a toner supply device that discharges toner and supplies toner to the developing device; and an image memory that receives image data to be printed. The printing speed is switched to a low speed when the toner replenishing capability of the toner replenishing device obtained from the remaining amount of toner falls below a predetermined value.

  A sixth technical means is the fifth technical means characterized in that the timing for switching the printing speed is set to one job unit.

  According to a seventh technical means, in the fifth or sixth technical means, the remaining amount of toner is calculated based on image data input to the image memory.

  According to the present invention, even when the remaining amount of toner in the toner cartridge is reduced and the toner replenishing capability of the toner replenishing device is equal to or less than a predetermined value, the print density unevenness caused by the toner density unevenness is constant until just before the toner runs out. Print quality can be maintained. Further, when the timing for switching the printing speed is set to one job unit, density unevenness does not occur in the same job.

  In addition, when a rotary toner bottle is used for the toner cartridge, the toner discharge amount does not deviate greatly from the calculated value regardless of the remaining amount of toner, so that the printing speed can be switched at an appropriate time.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a configuration of a developing device and a toner replenishing device in a general image forming apparatus using a two-component developer. Reference numeral 10 denotes a toner discharged from the toner cartridge C and developed through a carry-in tube 30. A toner replenishing device 40 for replenishing toner to the device 20 is a photosensitive drum as an electrostatic latent image carrier. The developing device 20 includes a toner carrying portion 21 for carrying toner from the toner replenishing device 10 into the developing tank 26, toner and a carrier stored in the developing tank 26 that is divided into two by communicating both ends with a partition wall 25. And a developing roll 24 for applying the stirred developer to the photosensitive drum 40.

  FIG. 2 is a block diagram for explaining the control function of the image forming apparatus according to the present invention. Hereinafter, a copying machine will be described as an example. 101 is an operation unit for setting various settings such as copy density, magnification, paper size, and number of copies, 102 is an image memory for storing image data of a document read by a scanner, and 103 is An image processing unit 104 that processes image data stored in the image memory based on various settings made by the user from the operation unit 101 includes a toner cartridge filling amount and a toner discharge characteristic of the toner cartridge (FIG. 4). A ROM 105 that stores a threshold value of the toner replenishment capability of the toner replenishing device determined in (5) is an EEEPRM that stores information such as the remaining amount of toner each time. 106 is a printing rate calculation unit that calculates the printing rate of each page of the image data captured in the image memory 102, 107 is a printing rate calculated by the printing rate calculation unit 106, a specified paper size, the number of copies, This is a toner consumption amount calculating means for calculating a toner consumption amount based on information such as print density, and this toner consumption amount is also a toner discharge amount discharged from the toner cartridge. 108 is a toner remaining amount calculation means for calculating by subtracting the amount of toner consumption each time from the new toner cartridge filling amount, and 109 is a toner replenishment capability of the toner replenishing device lower than the threshold value stored in the ROM 104. A printing speed setting means 110 for setting the printing speed to a low speed when the toner cartridge is driven, and a toner supply motor for intermittently rotating the toner cartridge to discharge the toner from the toner cartridge mounted on the toner supply device. Drive means.

  Next, an example of a processing flow in the control unit 100 of the image forming apparatus according to the present invention will be described with reference to FIG. First, in step S1, settings such as a monochrome mode and a color mode, a paper size, the number of copies, a print density, and the like are specified from the operation unit. When a print request is confirmed in step S2, the process proceeds to step S3. The image data to be printed is taken into the image memory. In step S4, the printing rate of each page is calculated based on the captured image data. In step S5, the toner consumption amount is calculated based on information such as the printing rate, paper size, number of copies, and printing density of each page. In step S6, the remaining amount of toner immediately before the printing process is calculated by subtracting the current consumption amount from the previous remaining amount of the toner cartridge C. In step S7, it is determined whether or not the toner replenishment capacity of the toner replenishing device obtained from the toner remaining amount is lower than the threshold value stored in the ROM 104. If the toner replenishment capacity is lower than the threshold value, the printing speed is decreased in step S8. Switch. If the toner replenishment capability is not less than or equal to the threshold value, the current process is terminated.

FIG. 3 is a configuration diagram of a developing device and a toner replenishing device in a general image forming apparatus using a two-component developer. 1 is a diagram illustrating a configuration of an image forming apparatus according to the present invention. FIG. 4 is a flowchart for explaining a printing speed setting in the image forming apparatus of the present invention. FIG. 6 is a diagram illustrating a relationship between a toner replenishment motor (TM) rotation time and a toner remaining amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Toner supply apparatus, 20 ... Developing apparatus, 21 ... Toner carrying-in means, 22, 23 ... Stirring means, 24 ... Developing roll, 25 ... Partition wall, 26 ... Storage tank, 30 ... Toner supply pipe, 40 ... Photosensitive drum .

Claims (7)

A latent image carrier comprising a photosensitive drum;
A developing device for stirring the toner and the carrier and supplying a two-component developer to the surface of the latent image carrier;
A toner supply device for discharging toner from a replaceable toner cartridge and supplying toner to the developing device;
An image memory for inputting image data to be printed;
Control means,
The image forming apparatus according to claim 1, wherein the control unit switches the printing speed to a low speed when a toner replenishing capability of the toner replenishing device obtained from a remaining amount of toner in the toner cartridge becomes a predetermined value or less.   2. The image forming apparatus according to claim 1, wherein the print speed is switched in units of one job.   The image forming apparatus according to claim 1, wherein the remaining amount of toner is calculated based on image data input to the image memory.   4. The image forming apparatus according to claim 1, wherein the toner cartridge is a rotary toner bottle. A latent image carrier comprising a photosensitive drum;
A developing device for stirring the toner and the carrier and supplying a two-component developer to the surface of the latent image carrier;
A toner supply device for discharging toner from a replaceable toner cartridge and supplying toner to the developing device;
An image memory for inputting image data to be printed;
A printing speed control method for an image forming apparatus comprising:
A printing speed control method, wherein a printing speed is switched to a low speed when a toner replenishing capacity of the toner replenishing device obtained from a toner remaining amount of the toner cartridge becomes a predetermined value or less.   6. The printing speed control method according to claim 5, wherein a timing for switching the printing speed is set to one job unit.   7. The printing speed control method according to claim 5, wherein the remaining amount of toner is calculated based on image data input to the image memory.

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