JP2006243492A - Image forming apparatus and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a drum from reaching the end of its life before toner during continuous printing at a low printing rate, with the result that the toner remains. <P>SOLUTION: A bias for image formation is controlled based upon information about toner use history (an amount of remaining toner, a printing rate, etc.) and an amount of use of the drum. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrophotographic image forming apparatus using an electrophotographic method, such as a laser beam printer, a copying machine, a facsimile, or a multifunction printer combining these.

  There are various types of image forming apparatuses that form an image based on an image signal sent from a host computer, such as an electrophotographic system, an inkjet system, and a thermal system. Among these, electrophotographic image forming apparatuses have become very popular in recent years because of advantages such as high speed, high image quality, and quietness.

<Image formation process>
FIG. 8 is a schematic configuration diagram showing an example of an image forming apparatus such as a copying machine, a printer, and a facsimile using a conventional electrophotographic system.

  The image forming apparatus 111 includes a process cartridge 110 that is detachable. The photosensitive drum 101 is rotationally driven in the direction of an arrow (clockwise), and the surface thereof is uniformly charged by a charging roller 102 to which a charging bias is applied, and then an image exposure L corresponding to an input image signal is performed by a laser exposure device 103. An electrostatic latent image is formed. This electrostatic latent image is developed as a toner image 104b by the developing sleeve 106 of the developing device 105 carrying a thin layer of toner 104a on its surface. The toner image 104 b formed on the photosensitive drum 101 is transferred by a transfer roller 107 to which a transfer bias is applied to a transfer material P such as paper conveyed to a transfer nip N between the photosensitive drum 101 and the transfer roller 107. The

  That is, a transfer bias having a polarity opposite to that of the toner is applied to the transfer roller 107 contacting the photosensitive drum 101 at the transfer nip portion N, and a charge having a polarity opposite to that of the toner from the back side where the toner image of the transfer material P is not formed. Is applied, the toner image 104b on the photosensitive drum 101 is transferred to the surface of the transfer material P.

  The transfer material P holds the transferred toner image 104c and is conveyed to the fixing device 108. After the toner image is thermally fixed on the surface of the transfer material P by the fixing device 108, it is discharged to the outside. Further, the transfer residual toner 104d remaining on the photosensitive drum 101 after the transfer is removed by the cleaning blade 109 and collected. Of these series of image forming processes, the photosensitive drum 101, the charging roller 102, the developing device 105, the developing sleeve 106, and the cleaning blade 109 are integrally included to form a process cartridge 110.

  The image forming apparatus 111 using such a laser exposure method develops image data sent from an external information processing device (not shown) such as a personal computer or a workstation into bitmap data, and turns on the laser based on the bitmap data. / OFF signal is generated and input to a laser drive circuit (not shown). As a result, the semiconductor laser diode is driven to emit light to perform image exposure L, and an electrostatic latent image is formed by laser exposure corresponding to the input image data to form an image.

<About process cartridges>
Each component of the electrophotographic image forming apparatus is worn or consumed every time an image is formed, so that it is necessary to perform maintenance after forming a certain amount of image. In particular, the surface of the photosensitive drum is worn by rubbing against the cleaning blade every time image formation is performed. Further, since the toner is also consumed by image formation, the degree of wear is larger than that of other parts, and the replacement frequency is increased.

  Therefore, in order to replace these consumables as easily as possible, the photosensitive drum unit and the toner cartridge can be replaced independently, as described above, the photosensitive drum, the charging roller, the developing device, the developing sleeve, and the cleaning blade. In many cases, a process cartridge system in which these are integrated in a compact manner is employed. The former is mainly used in copying machines, and only the photosensitive drum unit is replaced when the photosensitive drum reaches the end of its life, and only the toner cartridge is replaced when the toner runs out. Each life is informed to the user by issuing a warning on the display panel of the image forming apparatus by each life detecting means. According to this method, the photosensitive drum and toner can be replaced independently, which is economical. However, when replacing the toner cartridge, it is necessary to work carefully so that the user does not touch the toner.

  On the other hand, the latter process cartridge system has an advantage that it is easy to handle because the process cartridge is replaced when the toner runs out. In addition, since the user can perform the maintenance of the apparatus independently of the service person, the operability can be remarkably improved. In recent years, it has become widespread mainly in small image forming apparatuses such as laser beam printers.

  In such a process cartridge, in order to prevent the occurrence of image defects due to toner depletion and photosensitive drum wear, information relating to the remaining amount of toner and the photosensitive drum life is detected by some means, and the result is connected to the image forming apparatus. It is often notified to the host computer etc. to inform the user.

  There are various methods for detecting the remaining amount of toner. For example, a piezoelectric sensor method for detecting the presence or absence of toner depending on whether or not the toner is in contact, an antenna sensing method for detecting a change in capacitance due to the presence or absence of toner, and toner An optical method for detecting the amount of light transmitted through the toner container containing the toner, a pixel signal integration method for counting individual image signals forming dots and multiplying the count number by a predetermined coefficient to obtain toner consumption, etc. is there.

  As a means for detecting the life of the photosensitive drum, for example, a method for detecting the film thickness of the photosensitive drum, a method for calculating the film thickness of the photosensitive drum according to the number of printed sheets, a driving time of the photosensitive drum, and an integration of the charging time are detected. There are methods.

  By the way, in a process cartridge in which a developing unit including toner, a photosensitive drum, or other process unit is integrated, the lifetime is not always determined by the remaining amount of toner. For example, when an image having a low printing rate is continuously printed, the photosensitive drum may be worn out before the toner is consumed, and the service life may be reached. Since the consumption per developer print is almost constant depending on the printing rate, the photosensitive drum film thickness corresponding to the life of the process cartridge is estimated in advance by taking into consideration the amount of abrasion of the photosensitive drum and the consumption of toner per sheet. The amount of toner to be filled may be determined. It goes without saying that there is no waste in terms of resources and economics if the lifetimes of both sides are equal.

Therefore, a method is disclosed in which the lifespans of these detection means are compared and the process cartridge having the least remaining life is made the life of the process cartridge (Patent Document 1). In addition, a method for estimating the wear level of various consumables and automatically determining the life of the consumables is disclosed (Patent Document 2). Also disclosed is a method of supplying the developer so that the photosensitive drum is used up to the end of its life (Patent Document 3).
Japanese Patent Laid-Open No. 10-274908 (page 6, FIG. 1) JP-A-9-179458 (pages 12-14, FIGS. 1-6) JP-A-9-190068 (pages 7-8, FIGS. 1-6)

  In the process cartridge system in which the photosensitive drum and the developer are not independent, there are many cases where a margin is provided for the life of the photosensitive drum rather than the life of the toner. This is because the printing rate to be printed differs depending on the use application of the user, so that the developer is not wasted. However, if an image with a low printing rate is continuously printed, the toner consumption is kept low, and even if there is sufficient toner, the wear of the photosensitive drum does not change. There is a possibility that a situation may occur in which a defect occurs or the process cartridge must be replaced.

  In addition, when low-consumption printing continues, the amount of toner that does not fly to the photosensitive drum increases even when the toner is conveyed to the developing unit by the developing sleeve of the developing device, and the toner circulates in the developing device, causing heat and mechanical stress. In some cases, the toner gradually deteriorates and developability deteriorates.

  The present invention has been made in view of such problems. Even when an image having a low printing rate is often printed, the developer remaining at the time when the process cartridge reaches the end of its life by controlling the process conditions. An object of the present invention is to provide an image forming apparatus and a process cartridge which are reduced in amount as much as possible and more economical.

  In the image forming apparatus for forming a visible image on a predetermined recording medium based on the input image data, the object is to provide at least an image carrier for holding an electrostatic latent image and a developer containing the developer. A process cartridge that integrally includes a container, and is detachably attached to the main body of the image forming apparatus, a detection unit that detects information about a life of the image carrier, and a developer printing rate history of the developer container. At least two detection means for detecting information, and having a plurality of image forming modes for suppressing consumption of the developer by correcting the density of the image data, When the detection result reaches a predetermined value, according to the detection result of the developer printing rate history, the process conditions relating to image formation, the consumption amount of the developer, and the image carrier are determined. It can be achieved by controlling the combined conditions life.

  In addition, an image carrier for holding at least an electrostatic latent image and a developer container for storing the developer are integrally included, and visible on a predetermined recording medium based on input image data. In a process cartridge that is detachable from an image forming apparatus main body that forms an image, a detection unit that detects information about a life of the image carrier and a detection unit that detects information about a developer printing rate history of the developer container A plurality of image forming modes for suppressing consumption of the developer by correcting the density of the image data, and the detection result of the image carrier life detection means becomes a predetermined value; At this point, according to the detection result of the developer printing rate history, the process condition for image formation is controlled to a condition that matches the consumption amount of the developer with the life of the image carrier. In can be achieved.

  As described above, according to the present invention, in an image forming apparatus that forms a visible image on a predetermined recording medium based on input image data, an image carrier for holding at least an electrostatic latent image; A process cartridge that integrally includes a developer accommodating portion that accommodates a developer, which is detachably attached to the main body of the image forming apparatus, a detection unit that detects information about the life of the image carrier, and the developer accommodating portion A plurality of image forming modes that suppress consumption of the developer by correcting the density of the image data. When the detection result of the image carrier life detection means reaches a predetermined value, the process conditions relating to image formation are set in accordance with the detection result of the developer printing rate history. Controlling the consumption of the combined conditions the life of the image bearing member, without be leftover as much as possible waste toner makes it possible to use economically the image forming apparatus.

  In addition, an image carrier for holding at least an electrostatic latent image and a developer container for storing the developer are integrally included, and visible on a predetermined recording medium based on input image data. In a process cartridge that is detachable from an image forming apparatus main body that forms an image, a detection unit that detects information about a life of the image carrier and a detection unit that detects information about a developer printing rate history of the developer container A plurality of image forming modes for suppressing consumption of the developer by correcting the density of the image data, and the detection result of the image carrier life detection means becomes a predetermined value; At this point, according to the detection result of the developer printing rate history, the process condition for image formation is controlled to a condition that matches the consumption amount of the developer with the life of the image carrier. , Without be leftover as much as possible waste toner makes economically possible to use a process cartridge.

  Embodiments of the present invention will be described in detail with reference to the drawings.

  A first embodiment of the present invention will be described.

<Description of Image Forming Apparatus and Image Forming Process>
FIG. 2 is a schematic cross-sectional view showing a schematic mechanism of the image forming apparatus of this embodiment. An image forming apparatus 13 using electrophotographic technology includes a photosensitive drum 1 as an image carrier. Around the photosensitive drum 1, a charging roller 2, a developing device 3, a transfer roller 4, and a cleaning blade 5 are disposed in this order along the rotation direction of the photosensitive drum 1, and above the charging roller 2 and the developing device 3. Is provided with an exposure device 6. A fixing device 7 is disposed downstream of the transfer nip N formed between the photosensitive drum 1 and the transfer roller 4 in the transfer material conveyance direction. Of these, the photosensitive drum 1, the charging roller 2, the developing device 3, and the cleaning blade 5 are integrally included to form a process cartridge 14 that is detachable from the main body of the image forming apparatus 13.

  In this embodiment, the photosensitive drum 1 is a negatively charged organic photosensitive drum having a diameter of 30 mm. The photosensitive drum 1 has an OPC photosensitive layer on an aluminum drum base, and is provided with a driving unit (not configured) provided on the image forming apparatus 13 side. The predetermined peripheral speed is 150 mm / sec. It is rotationally driven in the direction of the arrow (clockwise) at (process speed), and is charged uniformly with negative polarity by the charging roller 2 that contacts in the rotational process.

  A charging roller 2 serving as a charging unit contacts and rotates with the surface of the photosensitive drum 1 with a predetermined pressing force, and uniformly charges the photosensitive drum 1 with a predetermined polarity and potential by a charging bias applied from a charging bias power source 8. To do. The charging roller 2 has an elastic layer in which conductive carbon is dispersed in 3 mm thick urethane rubber, EPDM or the like on the peripheral surface of a core metal having a diameter of 6 mm, and epichlorohydrin having a thickness of 100 to 500 μm without an adhesive member on the surface. It is configured by covering a high-resistance surface layer such as rubber, and has a roller shape with an outer shape of 12 mm and a longitudinal length of 250 mm. As the charging bias, a DC voltage Vprdc corresponding to the drum dark portion potential Vd is superimposed and applied to the AC voltage Vpp at which the charging roller 2 is sufficiently discharged. In this embodiment, Vprdc = −650V. A sine wave having a frequency of 1300 Hz is used as the AC voltage waveform. For the AC AC component of the charging bias, constant current control is performed so that a constant current always flows between the photosensitive drum 1 and the charging roller 2. In this example, the constant current value was set to 1200 μA, and at this time, uniform and good charging was obtained in a normal temperature and normal humidity environment.

The exposure apparatus 6 uses a laser output unit (not shown) as a laser beam (exposure beam) obtained by modulating image information input from a personal computer (not shown) or the like according to a time-series electric digital image signal by the video controller 27. The electrostatic latent image corresponding to the image information is formed by scanning and exposing the surface of the charged photosensitive drum 1. In this embodiment, the amount of laser light was 2.5 mJ / m ^2, and the light portion potential Vl on the photosensitive drum of the laser exposure portion was Vl = −200V. The image resolution was 600 dpi (dot per inch).

  The developing device 3 is arranged in an opening so as to face the surface of the photosensitive drum 1 and is rotatable with a predetermined interval, a developing sleeve 9 that is rotatable, a toner 10 as a developer, and a rotatable stirring member 11 that stirs the toner. A developing blade 12 for frictionally charging the toner on the developing sleeve 9 is provided. The toner 10 is conveyed to the developing sleeve 9 by the agitating member 11, and the toner 10 is taken into the developing sleeve 9. At that time, the toner 10 is regulated in layer thickness by the developing blade 12, and simultaneously charged by friction and sent to the developing region. In the development area, the toner 10 is attached to the electrostatic latent image on the photosensitive drum 1 to be visualized as a toner image. In the developing sleeve 9, a magnet roller (not shown) in which a plurality of magnetic poles N and S are alternately formed is disposed so as not to move relative to the developing sleeve 9. The magnet roller does not rotate and is always held at a fixed position and kept in the same magnetic pole direction. The developing blade 12 gives a charge necessary for development to the toner 10 and regulates the layer thickness of the toner on the developing sleeve 9. A one-component magnetic developer is used for the toner 10 and reversal development is performed. The toner uses a one-component magnetic developer, but is not limited to this. From the developing sleeve 9, the toner sent into the developing region flies onto the photosensitive drum 1 by a developing bias in which direct current DC and alternating current AC are applied from a power source (not shown). The development bias was such that the DC voltage was Vdc = −500V, and the development contrast was | Vdc−Vl | = 300V. The AC voltage Vpp was Vpp = 1500 V, and a rectangular wave with a frequency of 2500 Hz was used.

  Here, the toner that does not have a sufficient charge necessary for development remains on the developing sleeve 9 or, even if it flies on the photosensitive drum 1, it is on the developing sleeve 9 due to the magnetic force of the magnet roller and the AC pullback component of the developing bias. Pulled back to. On the other hand, the toner 10 having sufficient charge converts the electrostatic latent image into a visible toner image.

  The transfer roller 4 serving as a transfer unit is brought into contact with the surface of the photosensitive drum 1 with a predetermined pressing force to form a transfer nip portion N, and is transferred to the photosensitive drum 1 by a transfer bias applied from a transfer bias power source (not shown). The toner image on the surface of the photosensitive drum 1 is transferred to a transfer material P such as paper at the transfer nip N between the rollers 4.

  The fixing device 7 includes a heating roller having a halogen heater (not shown) and a pressure roller therein, and transfers the transfer material P while nipping and conveying the transfer material P at a fixing nip between the fixing roller and the pressure roller. The toner image transferred to the surface of the material P is heated, melted and pressurized to be thermally fixed to obtain a permanent image. The permanent image on the transfer material P that has been fixed is discharged out of the image forming apparatus 13.

  In this embodiment, the cleaning blade 5 as a cleaning means is a casting type made of urethane rubber. The contact pressure against the photosensitive drum 1 is 40 to 50 gf / cm, and the rotational direction of the photosensitive drum 1 is It is pressed from the opposite direction. Toner remaining without being transferred onto the photosensitive drum 1 is cleaned by the cleaning blade 5, and the photosensitive drum 1 is again used for image formation.

<Developer remaining amount detection and photosensitive drum life detection>
Next, an example of the remaining toner amount detection mechanism used in this embodiment will be described with reference to FIGS.

  In the process cartridge 14, two parallel sheet metals, a plate antenna sheet metal (hereinafter abbreviated as PA) 15 for detecting the remaining amount of developer and a PA sheet metal 16, extend in the longitudinal direction in the process cartridge 3. These are fixedly arranged so as to face each other.

  A developing bias in which a direct current and an alternating current component are superimposed is applied from the power source 17 to the developing bias to cause the toner to fly to the photosensitive drum 1. A residual amount detection bias is applied to PA 16 from the same power source 17 as the development bias. At this time, the current value induced in the PA 15 can be measured, and the electrostatic capacity between the PAs 15 and 16 or between the PA 15 and the developing sleeve 9 can be measured by the developer remaining amount detection circuit 18.

  The remaining amount of toner is detected by measuring the capacitance between the PAs 15 and 16 because the developing device 3 is sufficiently filled with toner when the remaining amount of toner is large. If there is a small amount of toner, the amount of toner in the developing device 3 is small and a certain amount is in the vicinity of the developing sleeve 9, so that it can be detected by measuring the capacitance between the PA 15 and the developing sleeve 9. By changing the position and number of PAs, it is possible to detect the remaining amount more finely and accurately.

  PA 16 is an input electrode member to which a detection voltage is input in the developer remaining amount detection mechanism of the image forming apparatus 13, and PA 15 is a developer amount (toner remaining amount) existing between PA 16 and the developing sleeve 9. It functions as an output electrode member that outputs the corresponding capacitance to the image forming apparatus 13.

  The electrostatic capacity C between the sheet metals as the two electrode members is in the relationship of the area S of the sheet metal, the distance d, the relative dielectric constant Kε between the two sheet metals, and the following equation (1).

C = Kε × S / d (1)
The relative dielectric constant Kε is a value that changes according to the amount of toner between the sheet metals. When the ratio of toner between the sheet metals is large, Kε increases, and when it is small, Kε decreases, so the remaining amount of toner and the capacitance are related, and the remaining amount of toner is converted from the relative dielectric constant Kε.

As a configuration used in this example, nonmagnetic SUS plates having an area S = 15 cm ² were used for PA15 and PA16. The distance between the developing sleeve 5 and PA15 is 2 mm, and the distance between PA15 and PA16 is 50 mm. As a result, the remaining amount of toner can be detected sequentially and a warning can be given to the user.

  As shown in FIG. 4, the developer remaining amount detection circuit performs a predetermined calculation process on the current amount detection unit 20 that detects the current amount from the PA 15 and the detected current amount (1). The calculation control unit 23 that converts the electrostatic capacity into the remaining amount of toner from the equation, the storage unit 24 that stores the result of the remaining toner detection, and the remaining amount of toner, for example, converted into a percentage display and displayed on the main body of the image forming apparatus. And display means 25. This PA method is a toner near-end method that enables detection from the time when the amount of remaining toner becomes small.

  Next, an example of the photosensitive drum life detection mechanism used in this embodiment will be described with reference to FIGS.

  The surface of the photosensitive drum 1 is deteriorated by receiving AC + DC charging, particularly an AC component, from the charging roller 2, and wear by the cleaning blade 5 is promoted. Therefore, the wear of the photosensitive drum 1 is determined by the photosensitive drum driving time integrated value t1 and the charging AC bias application time integrated value t2. Since the amount of shaving of the photosensitive drum varies depending on each drive, the usage amount of the photosensitive drum 1 is calculated by combining the weighted coefficients A and B, the photosensitive drum film thickness, the characteristic constant of the charging roller, and the like. it can. That is, it calculates from the following arithmetic expression.

T = A × t1 + B × t2 + α (2)
In this embodiment, the abrasion amount of the photosensitive drum is set to A = 1 and B = 4 from the contribution of the driving time and the charging AC bias application time.

  Each time is intermittent printing per sheet t1 = 10 sec. , T2 = 5 sec. In continuous printing, t1 = t2 = 2.5 sec. Met. The shortest time for the photosensitive drum to reach the end of its life is all in the case of single-sheet intermittent printing, and the longest is in the case of continuous printing.

  From these values, the photosensitive drum film thickness, the drive time for each print, and the charging bias application time, the value of T at which the photosensitive drum reaches the end of its life can be calculated. By using this value as T0 and comparing it with the sequentially calculated T value, it is possible to calculate how many intermittent prints are used and the remaining usable number. It is also possible to calculate the photosensitive drum usage rate as a percentage by T / T0.

  As shown in FIG. 4, the photosensitive drum life detection circuit includes a photosensitive drum driving time detection unit 21 that detects a driving time from the photosensitive drum 1 and a charging AC bias detection that detects a charging AC bias application time applied to the charging roller 2. Unit 22, a calculation control unit 23 that converts the photosensitive drum usage amount into a photosensitive drum usage rate according to the above equation (2) by performing a predetermined calculation process, a storage unit 24 that stores the photosensitive drum usage rate, And display means 25 for displaying the photosensitive drum usage rate on the main body of the image forming apparatus.

<Process condition control>
In this embodiment, process control is performed when the photosensitive drum reaches the end of its life. That is, when the usage amount of the photosensitive drum reaches 80% of the process cartridge life, that is, 80% of the toner life in the printing of the A4 paper 4% printing rate in the normal mode, the toner consumption is less than 80%. When the remaining amount is more than 20%, the toner is not wasted by switching to a process condition that consumes more than before. The toner is filled in such a manner that the life of the A4 paper of 4% print rate in the normal mode reaches 6000 sheets, and this is the life of the process cartridge. On the other hand, the photosensitive drum was set so as to reach the end of its life by 1.5 times this, that is, 9000 intermittent single-sheet prints. If there are many continuous prints, the life of the photosensitive drum reaches 9000 prints. However, if there are many intermittent prints, the amount of shaving of the photosensitive drum will increase, and there will be a lot of toner for users with many prints with a low printing rate. The situation is likely to happen.

  The process condition switching will be described with reference to the flowchart of FIG. While the image forming apparatus is being driven, a process condition change determination is started as appropriate (step 1). First, the drum usage is detected according to the above-described method (step 2), and the accumulated photosensitive drum usage up to that time is calculated, and the drum usage is set to a predetermined ratio of 9000 photosensitive drum lifetimes, 80% in this embodiment. Is judged (step 3). In this case, if it is equal to or more than 7200 intermittent prints, YES is determined, and if it is smaller than that, NO is determined. If NO, the remaining amount of toner is detected (step 4) and the process conditions are maintained (step 5). On the other hand, if the answer is YES, the remaining toner amount is detected (step 6). If the remaining toner amount is 20% or more in this embodiment, YES, if it is 20% or less, NO. (Step 7). If NO, process conditions are maintained (step 5). On the other hand, if YES, the process condition is changed (step 8). This completes the process condition change determination (step 9).

  As a process condition to be changed, in this embodiment, the DC voltage value of the developing bias is changed, and the toner consumption is changed. The characteristics at this time are shown in FIG. The vertical axis represents the latent image potential on the photosensitive drum, and the horizontal axis represents the image line width. By changing the DC component Vdc of the development bias and changing the development contrast | Vdc−Vl |, the line width can be changed and the toner consumption can be changed. The variable amount of the 4 dot line width depending on the development contrast was as shown in FIG. Table 1 shows the amount of toner consumed when printing on A4 paper at 4% when the respective development contrasts are density adjustment values (1) to (4). The toner consumption ratio indicates a ratio when the normal contrast (density adjustment value (1)) is 1.

  The process condition is changed with reference to the consumption amount. For example, when printing is continued at an average printing rate of 2.5%, the toner is consumed for about 9,600 sheets, and the service life is reached. Since the photosensitive drum has a service life equivalent to 9000 intermittent prints per sheet, the toner remains at the end of the life of the photosensitive drum. If the photosensitive drum life is 80% and the average printing rate up to 7200 sheets is 2.5%, the remaining amount of toner at that point is 25% (corresponding to 4500 sheets in 4% printing), and process control is performed. to decide.

Which density adjustment value to select
W = (number of remaining toner prints / number of remaining photosensitive drum prints)
Is compared with the toner consumption ratio in Table 1. A toner consumption ratio that is closest to the value of W may be selected.

  In this case, the remaining printable number of photosensitive drums is 1800, the remaining number of printable toners is 1500 for 4% printing, and 2400 for 2.5%. Accordingly, if the toner consumption is set to W = 2400/1800 = 1.33... Times, the photosensitive drum can be used until the end of its life without leaving any toner. In this case, the density adjustment value (4) is selected. As a result, the process cartridge can be used economically without wasting toner as much as possible. In addition, when there are many prints with a low printing rate, the amount of toner that does not fly to the photosensitive drum increases even when the toner is conveyed to the developing section by the developing sleeve of the developing device, and the toner circulates in the developing device, causing heat and mechanical The toner may gradually deteriorate due to stress. In this case as well, the development contrast can be compensated for by changing the development contrast and controlling the toner consumption amount to a higher density direction.

  Further, if this process condition change determination is performed a plurality of times after 80%, the toner consumption can be controlled in accordance with the change in the printing rate. Furthermore, when this process condition is changed, the user may be warned on the display means. Furthermore, usability can be improved if the user selects whether or not to make changes. In this embodiment, the development bias DC voltage is changed and the development contrast is adjusted. However, the toner consumption is changed even if the AC component Vpp, frequency, laser light quantity, irradiation time, etc. of the development bias are changed. The effect of the present invention is not impaired as long as it is.

  A second embodiment of the present invention will be described.

  This embodiment is different from the first embodiment in that the remaining amount of toner is detected by the PA, the pixel signal integration method is used, the average print rate of the print is appropriately obtained, and the process conditions are controlled. In the PA method, the detection accuracy is not sufficient unless the remaining amount of toner is about 30% or less. Therefore, it is possible to control the developing bias after the remaining amount of toner. Therefore, before the remaining amount of toner can be detected by PA, the average printing rate is obtained by the pixel signal integration method, and the development bias is controlled.

  Since the configuration of the image forming apparatus, the image forming method, the photosensitive drum life detection, and the toner remaining amount detection by PA are the same as in the first embodiment, they will be omitted, and the toner remaining amount detection by pixel signal integration and process control will be described. .

  As in the first embodiment, the life of the toner is set to 6000 sheets in the normal mode A4 paper 4% printing rate, which is the life of the process cartridge, and the photosensitive drum is set to reach the life of 9000 intermittent prints. did.

  An average printing rate detection by pixel signal integration in this embodiment will be described. The number of dots of the image signal per print page is counted, the toner consumption per dot is determined in advance, and this is multiplied by the number of dots to determine the consumption per page. This is integrated to detect the remaining amount of toner. If the print number information is also combined, the integrated average print rate can be calculated. When the recording paper is A4 paper (210 × 297 mm), the image formable area is 200 × 287 mm, and converted to dots, 4724 × 6800 dots = 32123200 dots (total number of dots).

Here, a flow for obtaining the toner consumption will be described with reference to FIG. Data to be printed out from the host computer is sent to the image signal processing unit 26 as an electrical signal. The image signal processing unit 26 converts this data into a video signal for each scanning line, generates a laser drive signal corresponding to the video signal, controls the laser ON / OFF signal, and irradiates the photosensitive drum. When the video signal becomes a signal for laser emission, a horizontal synchronizing signal (BD signal) comes to the head of the scanning line. Since the video signal comes after a certain time from the BD signal, the start position of the video signal can be known by detecting the BD signal. The dot number counting means 27 counts the number of dots on each page and sends it to the dot number storage memory 28. Here, the number of dots per page is stored. The multiplication means 29 multiplies the number of dots by the toner consumption per dot, thereby calculating the toner consumption per page. The toner consumption per dot is 41 × 10 ⁻⁹ g in this embodiment. This value varies depending on the image forming apparatus, and it is necessary to determine the value by measuring in advance. Alternatively, this may be converted for each dot area (for example, a line image and a solid black image). This toner consumption amount is stored in the consumption amount storage memory 30. Next, the toner consumption up to that time is integrated by the integration means 31, and the integrated toner consumption is stored in the integrated consumption storage memory 32. Here, the average number of prints is calculated by combining the number of prints from the number-of-prints counting unit 33 and the number of accumulated dots, and the average print rate storage memory 34 stores the average print rate. Note that there is no problem even if each of the storage memories described above also serves as the storage means of FIG.

  By the above means, it is possible to obtain the cumulative toner consumption and the average printing rate up to a certain point. When printing is performed so that the toner is consumed at 9000 sheets, which is the life of the photosensitive drum, the average printing rate is 2.66. When the drum usage rate reaches a predetermined ratio, the average printing rate is referred to. At this time, if the average printing rate is less than 2.66%, the developing bias is controlled in the direction where the toner consumption is large. If it exceeds 2.66%, the process conditions at that time are maintained.

Which density adjustment value is selected is performed as follows. Assume that processing is performed at a time corresponding to N drum usage. When the average printing rate is calculated, the remaining printable number M as toner at the printing rate is:
M = 6000 × (4% / average printing rate%) − N
Can be calculated as On the other hand, the remaining printable number D of photosensitive drums is
D = 9000-N
It is. When the average printing rate is less than 2.66%, M> N, and the toner remains at the end of the photosensitive drum life. In order to adjust the toner consumption in accordance with the remaining printable number D of photosensitive drums, the toner consumption may be increased M / D times.

For example, the average print rate is referred to at the time of 4500 sheets when the photosensitive drum usage amount is 50% of the lifetime of the photosensitive drum. When the average printing rate is 2.5%, it is less than 2.66%, so the developing bias is controlled. In this case, the remaining printable number M at a printing rate of 2.5% is
M = 6000 × (4% / 2.5%) − 4500 = 5100 sheets, and the remaining printable number D of photosensitive drums is
D = 9000-4500 = 4500 sheets. Therefore, if M / D = 5100/4500 = 1.13... Times the toner consumption, that is, 2.5 × 1.13 = 2.83. There is nothing.

  In this embodiment, the density adjustment value is selected with reference to Table 2. The individual values are the same as in Example 1.

  The closest value of the toner consumption increase rate on the right side of the table may be selected as the M / D value. In this case, (3) is selected.

  The process of obtaining the average printing rate by the pixel signal integration method is performed until the toner remaining amount detection by the PA is started. Since the detection of the remaining amount of toner in the PA is started from the remaining amount of toner 20%, the developing bias is controlled by the method of the first embodiment. In the pixel signal integration method, errors occur due to errors in toner consumption, errors due to toner deterioration, changes in sensitivity of the photosensitive drum, etc., and these are integrated, so that the remaining toner amount detection is accurate only from the average printing rate. It may be missing. Therefore, the electrostatic capacity is directly measured, and the remaining amount of toner is detected by the PA method for measuring the remaining amount of toner, and the development bias is controlled.

  As a result, the process cartridge can be used economically without wasting toner as much as possible. In addition, when there are many prints with a low printing rate, the amount of toner that does not fly to the photosensitive drum increases even when the toner is conveyed to the developing section by the developing sleeve of the developing device, and the toner circulates in the developing device, causing heat and mechanical The toner may gradually deteriorate due to stress. In this case as well, the development contrast can be compensated for by changing the development contrast and controlling the toner consumption amount to a higher density direction. Further, when this process condition is changed, the display means may be warned to that effect. Furthermore, usability can be improved if the user selects whether or not to make changes.

(Other examples)
In the case of the first and second embodiments, the image forming apparatus is provided not only for forming a single color image, but also provided with a plurality of developing means, and a plurality of color images (for example, two color images, three color images, or full color images). And the like can also be applied to an image forming apparatus.

  As the photosensitive drum life detection means, there is no problem in detecting the film thickness of the photosensitive drum, or calculating the capacitance by detecting the current value. As the toner remaining amount detecting means, the remaining amount detection by various sensors, the method of counting the dots of the pixel signal, and the like do not impair the effect of the present invention.

  As a developing method, various developing methods such as a known two-component magnetic brush developing method can be used in addition to the jumping development using the one-component magnetic toner of this embodiment.

  Further, the electrophotographic photosensitive member is not limited to the photosensitive drum of this embodiment, and for example, a photoconductive member may be used. For example, amorphous silicon, amorphous selenium, zinc oxide, titanium oxide, organic photoconductor, and the like are included. In addition, examples of the shape on which the photoconductor is mounted include a rotating body such as a drum shape and a belt shape, and a sheet shape. In general, drum-shaped or belt-shaped ones are used. For example, in the case of a drum-shaped photoconductor, a photoconductor is deposited or coated on a cylinder made of aluminum alloy or the like. It is.

  In addition to the blade shape of this embodiment, the photosensitive drum cleaning means may be configured using a fur brush, a magnetic brush, or the like.

  Further, in the embodiments, a laser beam printer is exemplified as the image forming apparatus. However, the present invention is not limited to this, and a process cartridge including toner and a photosensitive drum, which are integrally included, is used. It should be. Needless to say, the image forming apparatus can be used in other image forming apparatuses such as an electrophotographic copying machine, a facsimile machine, or a word processor.

Flowchart showing process condition change determination according to Embodiment 1 Schematic cross-sectional view of an image forming apparatus according to Embodiments 1 and 2 Sectional schematic diagram of process cartridge according to first and second embodiments Schematic diagram of photosensitive drum life detection circuit and toner remaining amount detection circuit according to first and second embodiments. The figure which shows the relationship between the latent image electric potential on the photosensitive drum of the line image which concerns on Example 1, 2, and developing bias. The figure which shows the relationship between the development contrast and line width which concern on Example 1,2. The figure which shows the calculation method of the average printing rate by the pixel signal integration means based on Example 2. Schematic cross-sectional view of a conventional image forming apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging roller 3 Developing apparatus 4 Transfer roller 5 Cleaning blade 6 Exposure apparatus 7 Fixing apparatus 8 Charging bias power supply 9 Developing sleeve 10 Developer (toner)
DESCRIPTION OF SYMBOLS 11 Developer stirring rod 12 Developing blade 13 Image forming apparatus 14 Process cartridge 15 PA1 (input side electrode member)
16 PA2 (Output-side electrode member)
DESCRIPTION OF SYMBOLS 17 Developing bias power supply 18 Developer remaining amount detection circuit 19 Photosensitive drum lifetime detection circuit 20 Current amount detection part 21 Photosensitive drum drive detection part 22 Charge AC bias detection part 23 Arithmetic control part 24 Storage means 25 Display means 26 Image signal processing part 27 Dot number counting means 28 Dot number storage memory 29 Multiplication means 30 Consumption storage memory 31 Addition means 32 Accumulated consumption storage memory 33 Number of printed sheets counting means 34 Average printing rate storage memory N Transfer nip P Transfer material L Scan exposure

Claims (14)

In an image forming apparatus that forms a visible image on a predetermined recording medium based on input image data,
A process cartridge that integrally includes at least an image bearing member for holding an electrostatic latent image and a developer accommodating portion that accommodates a developer is detachably attached to the image forming apparatus main body,
Detecting means for detecting information on the lifetime of the image carrier;
Comprising at least two detection means of detection means for detecting information relating to the developer printing rate history of the developer container,
A plurality of image forming modes that suppress consumption of the developer by correcting the density of the image data;
When the detection result of the image carrier life detection means reaches a predetermined value,
According to the detection result of the developer printing rate history,
Controlling the process conditions for image formation to a condition that matches the consumption of the developer with the life of the image carrier;
An image forming apparatus. The developer printing rate history is
It is calculated from at least two of detection means for sequentially detecting the remaining amount of developer in the developer accommodating portion and detection means for counting the number of printed sheets.
The image forming apparatus according to claim 1. The developer printing rate history is
It is calculated from at least two of detection means for counting the number of pixel signal dots of the image data and detection means for counting the number of printed sheets,
The image forming apparatus according to claim 1.   4. The image forming apparatus according to claim 1, further comprising a warning display unit that warns a user of the contents when the process condition is switched. The process condition is characterized by changing a developing bias applied to the developer carrying member for visualizing the electrostatic latent image formed on the image carrying member with the developer.
The image forming apparatus according to claim 1. The process conditions are characterized in that the image carrier is exposed and the amount of light of an exposure means for forming an electrostatic latent image is changed.
The image forming apparatus according to claim 1. Using at least one or a combination of a plurality of the process conditions;
The image forming apparatus according to claim 1. An image carrier for holding at least an electrostatic latent image and a developer container that contains a developer are integrally included, and a visible image is displayed on a predetermined recording medium based on input image data. In a process cartridge that is detachable from the image forming apparatus main body to be formed,
Detecting means for detecting information on the lifetime of the image carrier;
Comprising at least two detection means of detection means for detecting information relating to the developer printing rate history of the developer container,
A plurality of image forming modes that suppress consumption of the developer by correcting the density of the image data;
When the detection result of the image carrier life detection means reaches a predetermined value,
According to the detection result of the developer printing rate history,
Controlling the process conditions for image formation to a condition that matches the consumption of the developer with the life of the image carrier;
Process cartridge characterized by. The developer printing rate history is
It is calculated from at least two of detection means for sequentially detecting the remaining amount of developer in the developer accommodating portion and detection means for counting the number of printed sheets.
The process cartridge according to claim 8. The developer printing rate history is
It is calculated from at least two of detection means for counting the number of pixel signal dots of the image data and detection means for counting the number of printed sheets,
The process cartridge according to claim 8.   11. The process cartridge according to claim 8, further comprising warning display means for warning a user of the contents when the process condition is switched. The process condition is characterized in that a developing bias applied to the developer carrying member for changing the developer to visualize an electrostatic latent image formed on the image carrying member is changed.
The process cartridge according to claim 8. The process conditions are characterized in that the image carrier is exposed and the amount of light of an exposure means for forming an electrostatic latent image is changed.
The process cartridge according to claim 8. Using at least one or a combination of the process conditions,
The process cartridge according to claim 8.

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