JP5015475B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to an image forming apparatus and an image forming method, and more particularly to an image forming apparatus and an image forming method which can be changed to an appropriate transfer voltage.

  2. Description of the Related Art In recent years, in an image forming apparatus, a transfer unit such as a roller that applies a voltage to a transfer material (such as a belt) on the opposite surface of an image carrier is provided to transfer a toner image on the image carrier to a transfer material. Intermediate transfer systems have been proposed.

  By the way, the electrical resistance value of the primary transfer roller of the transfer portion in the intermediate transfer system employed in the image forming apparatus is the accumulation of fatigue such as the temperature of the primary transfer roller, the relative humidity of the surroundings, and the increase in energization or use. It always fluctuates due to recovery during the suspension period.

  With reference to FIG. 1 and FIG. 2, the fluctuation of the electrical resistance value of the primary transfer roller will be described.

  First, the environmental dependence of the electrical resistance value of the primary transfer roller will be described with reference to FIG.

  As shown by the solid line a in FIG. 1, the electrical resistance values of the primary transfer roller are 10 ° C./20% RH (temperature 10 ° C./relative humidity 20%), 23 ° C./50% RH (temperature 23 ° C./relative). The humidity tends to decrease as the environmental conditions become high temperature and humidity, such as 30 ° C. and 85% RH (temperature 30 ° C. and relative humidity 85%). In the example of FIG. 1, the ratio of the electrical resistance value of the primary transfer roller in two environments of 10 ° C./20% RH and 30 ° C./85% RH is about 100 times. That is, this indicates that the electric resistance value of the primary transfer roller is higher in the winter than in the summer, and the electric resistance value of the primary transfer roller is higher in the morning than in the daytime.

  Next, with reference to FIG. 2, the fluctuation | variation by continuous use of the electrical resistance value of a primary transfer roller is demonstrated.

  As indicated by the solid line b in FIG. 2, the electrical resistance value of the primary transfer roller increases as the primary transfer roller is used continuously. In the case of the example in FIG. 2, the electrical resistance value of the primary transfer roller is 10 times the electrical resistance value at the start of use after approximately 200 minutes of continuous use. Note that when the use of the primary transfer roller, which has been fatigued due to fluctuations in energization and has an increased electrical resistance value, is stopped, the increased electrical resistance value starts to gradually decrease and then returns to the value at the start of use.

  Thus, the electrical resistance value of the primary transfer roller is subject to fluctuation due to the effect of the combination of the environment around the primary transfer roller and the continuous use time.

  Accordingly, a transfer voltage (hereinafter referred to as “primary transfer voltage”) applied to the primary transfer roller based on the electrical resistance value of the primary transfer roller at a predetermined time is set once in an appropriate range in advance. Even if it is fixed to the set primary transfer voltage, the appropriate range of the primary transfer voltage of the primary transfer roller is shifted as the electric resistance value of the primary transfer roller fluctuates. The toner image cannot be transferred sufficiently.

  Therefore, a method has been proposed in which the transfer voltage is constantly changed and optimized so that a sufficient transfer voltage can be applied (see, for example, Patent Document 1).

According to the method proposed in Patent Document 1, a transfer bias is selected based on the size and thickness of a sheet detected by a paper type detection program, and a generated voltage measured by a voltmeter. A transfer bias selected from the above is applied. As a result, a transfer bias corresponding to the size and thickness of the paper to be transferred is always applied even if the electrical resistance value of the transfer roller fluctuates depending on the paper size and thickness, temperature, and humidity. Can be transferred.
JP 2003-287966 A

  According to the method proposed in Patent Document 1, it is possible to obtain a good image by constantly changing appropriate transfer voltages (primary transfer voltage and secondary transfer voltage). If the transfer voltage is frequently changed due to the time required for the change, the printing productivity (number of printable sheets per minute, hereinafter used in the same manner) is extremely reduced.

  In recent image forming apparatuses, the printing interval between sheets to be printed tends to be shortened as much as possible in order to increase productivity, and the printing interval between sheets is set to 0.3 seconds, for example. However, in the method proposed in Patent Document 1, the transfer voltage cannot be changed during a printing interval of 0.3 seconds. Therefore, when changing the transfer voltage, the execution of printing must be temporarily stopped. If the transfer voltage is frequently changed in order to obtain a good image, the execution of printing is temporarily performed each time. As a result, the printing productivity is reduced.

  In particular, when printing a large number of sheets continuously in a series of print jobs, if the transfer voltage is changed in advance before starting printing, a good image can be obtained in the first half of the print job, but the print job In the second half, the preset transfer voltage deviates from the appropriate transfer voltage range as the electric resistance value fluctuates, and a good image cannot be acquired. Therefore, in order to obtain a good image throughout the entire print job, a method of periodically stopping the execution of printing and periodically changing the transfer voltage can be considered, but the more the transfer voltage is changed, the more This will reduce printing productivity.

  As described above, the image forming apparatus employing the intermediate transfer system has a problem that it is difficult to change to an appropriate transfer voltage while preventing a decrease in printing productivity.

  The present invention has been made in view of such circumstances, and an image forming apparatus capable of changing to an appropriate transfer voltage at a suitable time while preventing a decrease in printing productivity and an image thereof An object is to provide a forming method.

  In order to solve the above-described problems, an image forming apparatus of the present invention includes a transfer unit that transfers a toner image on an image carrier, a power source that applies a transfer voltage to the transfer unit, and a transfer voltage that is applied to the transfer unit. The transfer voltage calculating means for calculating the transfer voltage, the transfer voltage applied to the transfer means by the power supply based on the calculation result by the transfer voltage calculating means, and the transfer voltage changing means applying the transfer voltage to the transfer means. And a change time setting means for setting a change time for changing the transfer voltage.

  The image forming apparatus further includes a voltage detection unit that detects a voltage when a predetermined current set in advance is applied to the transfer unit, and the change timing setting unit applies a predetermined current set in the transfer unit. The change time can be set based on the voltage detected by the voltage detection means with reference to a change time database in which the voltage and the change time are registered in advance in association with each other.

  The change time registered in advance in the change time database can be made shorter as the voltage when a predetermined current set in advance is applied to the transfer means is larger.

  The change times registered in advance in the change time database can be divided into a plurality of categories according to the voltage when a predetermined current set in advance is applied to the transfer means.

  The image forming apparatus includes a voltage detection unit that detects a voltage when a predetermined current set in advance is applied to the transfer unit, and a change time calculation unit that calculates a change time based on the voltage detected by the voltage detection unit. The change time setting means can set the change time based on the calculation result calculated by the change time calculation means.

  The image forming apparatus further includes a current detection unit that detects a current when a predetermined voltage set in advance is applied to the transfer unit, and the change timing setting unit applies a predetermined voltage set in the transfer unit. The change time can be set based on the current detected by the current detection means with reference to the change time database in which the current when applied and the change time are registered in advance.

  The change time registered in advance in association with the change time database can be made shorter as the current when a predetermined voltage set in advance is applied to the transfer means is smaller.

  The change time setting means refers to a change time database in which the transfer voltage calculated by the transfer voltage calculation means and the change time are registered in advance, and changes based on the transfer voltage calculated by the transfer voltage calculation means. You can set the time.

  In the image forming method of the present invention, in order to solve the above-described problem, a transfer voltage calculating step for calculating a transfer voltage to be applied to the transfer portion, and a transfer voltage to be applied to the transfer portion by a power source are processed in the transfer voltage calculating step. A transfer voltage changing step that changes based on the calculation result of the above, and a change time setting step that sets a change time for changing the transfer voltage applied to the transfer portion by the power source by the processing of the transfer voltage changing step. .

  In the image forming apparatus of the present invention, the toner image on the image carrier is transferred, the transfer voltage is applied to the transfer unit by the power source, the transfer voltage applied to the transfer unit is calculated, and the transfer voltage applied to the transfer unit by the power source The voltage is changed based on the calculation result, and a change time for changing the transfer voltage applied to the transfer unit is set.

  In the image forming method of the present invention, the transfer voltage applied to the transfer unit is calculated, the transfer voltage applied to the transfer unit by the power source is changed based on the calculation result, and the transfer voltage applied to the transfer unit by the power source is changed. The change time is set.

  According to the present invention, it is possible to set a time for changing to an appropriate transfer voltage at a suitable time while preventing a decrease in printing productivity.

  In the following description of the embodiments of the present invention, this example exemplifying the correspondence relationship between the invention described in the claims and the “embodiment of the invention” is an embodiment that supports the invention described in the claims. It is for confirming what is described in this specification. Therefore, even if there are embodiments in the “embodiments of the invention” that are not actively described as corresponding to the invention, this does not mean that the embodiments correspond to the invention. It doesn't mean not. On the contrary, even if an embodiment is described herein as corresponding to the invention, this does not mean that the embodiment does not correspond to an invention other than the invention.

  The image forming apparatus according to claim 1 (for example, the image forming apparatus 1 in FIG. 3) includes a transfer unit (for example, a transfer unit) that transfers a toner image on an image carrier (for example, the photosensitive drums 12a to 12d in FIG. 3). The primary transfer rollers 20a to 20d in FIG. 3, a power source for applying a transfer voltage to the transfer unit (for example, the power source 29 in FIG. 3), and a transfer voltage calculating unit for calculating the transfer voltage to be applied to the transfer unit (for example, 5 and a transfer voltage changing means for changing the transfer voltage applied to the transfer means by the power source based on the calculation result by the transfer voltage calculation means (for example, FIG. 5). A primary transfer voltage changing unit 46), and a change time setting unit (for example, a print number setting unit 47 in FIG. 5) for setting a change time for changing the transfer voltage applied to the transfer unit by the transfer voltage changing unit. To prepare It is characterized by.

  The image forming method according to claim 9 is a transfer unit (for example, primary transfer rollers 20a to 20d in FIG. 3) that transfers a toner image on an image carrier (for example, the photosensitive drums 12a to 12d in FIG. 3). And an image forming method of an image forming apparatus (for example, the image forming apparatus 1 of FIG. 3) that applies a transfer voltage to the transfer unit (for example, the power source 29 of FIG. 3). A transfer voltage calculating step (for example, step S9 in FIG. 7) for calculating a transfer voltage, and a transfer voltage applied to the transfer unit by the power source based on a calculation result obtained by the process of the transfer voltage calculating step. A change step (for example, step S10 in FIG. 7) and a change time setting step for setting a change time for changing the transfer voltage applied to the transfer portion by the process of the transfer voltage change step. (For example, step S12 in FIG. 7).

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 3 shows a schematic mechanical configuration of a cross section of the image forming apparatus 1 to which the present invention is applied.

  As shown in FIG. 3, the image forming apparatus 1 includes a scanner unit 2, an image forming unit 3, and a paper feeding unit 4.

  The scanner unit 2 irradiates light on a document set on a document table, guides reflected light from the document to a light receiving element through a plurality of optical members, performs photoelectric conversion, and supplies an image signal to the image forming unit 3.

  The image forming unit 3 is provided with process cartridges 11a, 11b, 11c, and 11d. Each of the process cartridges 11a, 11b, 11c, and 11d includes photosensitive drums 12a, 12b, 12c, and 12d that are image carriers, and forms an image of a developer on these photosensitive drums.

  The photosensitive drum 12a has a cylindrical shape with a diameter of 30 mm, for example, and is provided to be rotatable in the direction of the arrow shown in the drawing. Attached devices are arranged around the photosensitive drum 12a along the rotation direction. First, a charging charger 13a is provided as an attachment device so as to face the surface of the photosensitive drum 12a. The charging charger 13a uniformly negatively (−) charges the photosensitive drum 12a. An exposure device 14a that exposes the charged photosensitive drum 12a to form an electrostatic latent image is provided downstream of the charging charger 13a. The exposure device 14a exposes the photosensitive drum 12a with a laser beam that is light-modulated corresponding to the image signal supplied from the scanner unit 2. The exposure device 14a may use an LED (Light Emitting Diode) instead of the laser beam.

  Further, a developing device 15a is provided downstream of the exposure device 14a. The developer 15a stores yellow developer and reversely develops the electrostatic latent image formed by the exposure device 14a with the developer. Further, an intermediate transfer belt 17 that is an image forming medium is installed so as to be in contact with the photosensitive drum 12a.

  A cleaner 16 a is provided upstream of the contact position between the photosensitive drum 12 a and the intermediate transfer belt 17. The cleaner 16a removes and stores residual toner on the photoconductor after transfer. A neutralizing lamp (a neutralizing lamp 31 in FIG. 4 described later) neutralizes the surface charge of the photosensitive drum 12a by uniform light irradiation. Thus, one cycle of image formation is completed, and in the next image forming process, the charging charger 13a again charges the uncharged photosensitive drum 12a uniformly.

  The intermediate transfer belt 17 has a length (width) substantially equal to the length of the photosensitive drum 12a in a direction orthogonal to the conveyance direction (the depth direction in the drawing). The intermediate transfer belt 17 has an endless (seamless) belt shape. The intermediate transfer belt 17 is stretched over and supported by a driving roller 18 that rotates the belt at a predetermined speed and a secondary transfer counter roller 19 that is a driven roller. The Reference numeral 27 denotes a tension roller for holding the intermediate transfer belt 17 at a constant tension.

The intermediate transfer belt 17 is formed of polyimide having a thickness of 100 μm, for example, in which carbon is uniformly dispersed. The intermediate transfer belt 17 has an electric resistance of 10 ⁻⁹ Ωcm and exhibits semiconductivity. The material of the intermediate transfer belt 17 may be any material that exhibits semiconductivity with a volume resistance of 10 ⁻⁸ to 10 ⁻¹¹ Ωcm. For example, in addition to polyimide in which carbon is dispersed, conductive particles such as carbon may be dispersed in polyethylene terephthalate, polycarbonate, polytetrafluoroethylene, polyvinylidene fluoride, or the like. A polymer film whose electric resistance is adjusted by adjusting the composition without using conductive particles may be used. Furthermore, such a polymer film mixed with an ion conductive substance, or a rubber material such as silicon rubber or urethane rubber having a relatively low electric resistance may be used.

  On the intermediate transfer belt 17, process cartridges 11 b, 11 c, and 11 d are sequentially arranged between the driving roller 18 and the secondary transfer counter roller 19 along the conveyance direction of the intermediate transfer belt 17 in addition to the process cartridge 11 a. ing. Each of the process cartridges 11b, 11c, and 11d has the same configuration as the process cartridge 11a.

  Photosensitive drums 12b, 12c, and 12d are provided substantially at the center of each process cartridge. Charging chargers 13b, 13c, and 13d are provided to face the surfaces of the photosensitive drums 12b, 12c, and 12d, respectively. Downstream of the charging chargers 13b, 13c, and 13d, exposure devices 14b, 14c, and 14d that expose the charged photosensitive drums 12b, 12c, and 12d to form electrostatic latent images are provided. Downstream of the exposure devices 14b, 14c, and 14d, developing devices 15b, 15c, and 15d that reversely develop the electrostatic latent images formed by the exposure devices 14b, 14c, and 14d are provided. Cleaners 16b, 16c, and 16d are provided on the upstream side of the contact position between the photosensitive drums 12b, 12c, and 12d and the intermediate transfer belt 17. The developing devices 15b, 15c, and 15d contain a magenta developer, a cyan developer, and a black developer, respectively.

  The intermediate transfer belt 17 is in contact with the respective photosensitive drums (photosensitive drums 12a to 12d) sequentially. Primary transfer rollers 20a, 20b, 20c, and 20d are provided corresponding to the respective photosensitive drums in the vicinity of the contact positions between the intermediate transfer belt 17 and the respective photosensitive drums. That is, the primary transfer rollers 20a to 20d are provided in back contact with the intermediate transfer belt 17 above the corresponding photosensitive drum, and face the process cartridges 11a to 11d through the intermediate transfer belt 17. The primary transfer rollers 20a to 20d are connected to a direct current power source of a positive (+) power source 29 which is a voltage applying unit. A primary transfer roller voltage detector (not shown) that detects the voltage applied to each primary transfer roller 20a to 20d is provided near each primary transfer roller 20a to 20d (described later with reference to FIG. 5). A primary transfer roller voltage detector 40) is provided.

  An intermediate transfer belt cleaner 21 that removes and accommodates residual toner on the intermediate transfer belt 17 is provided in the vicinity of the driving roller 18.

  On the other hand, a paper feed cassette 23 of the paper feed unit 4 that houses paper (transfer material) is provided below the image forming unit 3. The paper feed unit 4 is further provided with a pickup roller 24 that picks up paper one by one from the paper feed cassette 23. A registration roller pair 25 is rotatably provided near the secondary transfer roller 22 of the image forming unit 3. The registration roller pair 25 supplies the sheet at a predetermined timing to a secondary transfer portion where the secondary transfer roller 22 and the secondary transfer counter roller 19 face each other with the intermediate transfer belt 17 interposed therebetween.

  Further, a fixing device 26 for fixing the developer onto the paper is provided on the upper portion of the intermediate transfer belt 17. The fixing device 26 applies predetermined heat and pressure to the paper holding the toner image to fix the melted toner image on the paper.

  Further, an environmental sensor 28 that detects an environment such as temperature and relative humidity in the image forming apparatus 1 is provided at a predetermined position below the intermediate transfer belt 17. A power source 29 that supplies power to each unit of the image forming apparatus 1 is provided at a predetermined location of the image forming apparatus 1.

  Since the process cartridges 11a to 11d have the same configuration, in the following, the process cartridges 11 are collectively referred to when there is no need to distinguish them individually. The same applies to each part provided in the process cartridge 11 (11a to 11d).

  Next, a color image forming operation (printing process) of the image forming apparatus 1 will be described.

  When an instruction to start an image forming operation is given (that is, when an instruction to start printing is given), the photosensitive drum 12a starts to rotate by receiving a driving force from a driving mechanism (not shown). The charging charger 13a uniformly charges the photosensitive drum 12a to, for example, -600V. The exposure device 14a irradiates the photosensitive drum 12 uniformly charged by the charging charger 13a with light corresponding to an image (character) to be printed to form an electrostatic latent image. The developing device 15a contains a developer (yellow Y toner + ferrite carrier: two-component developer), and a developing bias power source of the power source 29 applies a bias value, for example, −380V to a developing sleeve (described later with reference to FIG. 4). A developing electric field is formed between the photosensitive drum 12a and the developing sleeve 35). The negatively charged Y toner is reversal development that adheres to the region of the image portion potential (high potential portion: considering the sign) of the electrostatic latent image on the photosensitive drum 12a.

  Next, the developing device 15b develops the electrostatic latent image with a magenta developer, and forms a magenta M toner image on the photosensitive drum 12b. At this time, the M toner, like the Y toner, has an average particle diameter of several microns (for example, 7 microns), and is negatively charged by friction charging with ferrite magnetic carrier particles (not shown) having an average particle diameter of about 60 microns. . The developing bias value is, for example, about −380 V as with the developing device 15 b and is applied to the developing sleeve 35 by a bias power source of the power source 29. The direction of the developing electric field is from the surface of the photosensitive drum 12b toward the developing sleeve 35 in the image portion, and negatively charged M toner adheres to the high potential portion of the latent image.

  The developing device 15c develops the electrostatic latent image with a cyan developer, and forms a cyan C toner image on the photosensitive drum 12c. At this time, C toner, like Y toner, has an average particle size of about several microns (for example, 7 microns), and is negative due to frictional charging with ferrite magnetic carrier particles (not shown) having an average particle size of about several tens of microns (60 microns). Is charged. The developing bias value is, for example, about −380 V like the developing device 15 c, and is applied to the developing sleeve 35 by the bias power source of the power source 29. The direction of the developing electric field is from the surface of the photosensitive drum 12c toward the developing sleeve 35 in the image portion, and negatively charged C toner adheres to the high potential portion of the latent image.

  The developing device 15d develops the electrostatic latent image with a black developer and forms a black B toner image on the photosensitive drum 12d. At this time, the B toner, like the Y toner, has an average particle size of about several microns (for example, 7 microns), and ferrite magnetic carrier particles (not shown) having an average particle size of about several tens of microns (for example, 60 microns) and frictional charging. Negatively charged. The developing bias value is about −380 V, for example, as in the developing device 15 d, and is applied to the developing sleeve 35 by the bias power source of the power source 29. The direction of the developing electric field is from the surface of the photosensitive drum 12d toward the developing sleeve at the image portion, and negatively charged B toner adheres to the high potential portion of the latent image.

  In the transfer area Ta formed by the photosensitive drum 12a, the intermediate transfer belt 17, and the primary transfer roller 20a, a required voltage, for example, a bias voltage of about +1000 V is applied to the primary transfer roller 20a. A transfer electric field is formed between the primary transfer roller 20a and the photosensitive drum 12a, and the Y toner image on the photosensitive drum 12a is transferred onto the intermediate transfer belt 17 according to the transfer electric field.

  The configuration of the primary transfer rollers 20b, 20c, and 20d is basically the same as that of the primary transfer roller 20a, and the description thereof will be omitted because it is repeated.

  The image on the intermediate transfer belt 17 onto which the Y toner image has been transferred in the transfer area Ta is conveyed toward the transfer area Tb. In the transfer region Tb, a magenta M toner image is transferred onto the Y toner image by applying a required voltage, for example, a bias voltage of about +1200 V, from the DC power supply of the power supply 29 to the primary transfer roller 20b. By applying a required voltage, for example, a bias voltage of about + 1400V to the primary transfer roller 20c in the transfer region Tc, and by applying a required voltage, for example, a voltage of about + 1600V, to the primary transfer roller 20d in the transfer region Td. A cyan developer image and a black developer image are sequentially transferred onto the transferred developer image. On the other hand, the pickup roller 24 takes out the paper from the paper feed cassette 23, and the registration roller pair 25 supplies the paper to the secondary transfer unit.

  In the secondary transfer unit, a required bias voltage is applied to the secondary transfer counter roller 19, and a transfer electric field is formed between the intermediate transfer belt 17 and the secondary transfer roller 22. Batch transfer color toner images to paper. The developer images of the respective colors collectively transferred in this way are fixed on the paper by the fixing device 26, and a color image is formed. The fixed paper is discharged onto an in-body paper discharge unit (not shown).

  FIG. 4 shows a schematic configuration inside the process cartridge 11 of FIG.

  As shown in FIG. 4, the process cartridge 11 is integrally composed of a photosensitive drum 12, a charging charger 13, a developing device 15, a cleaner 16, and the like, and is detachable from the main body of the image forming apparatus 1. ing.

  The developing device 15 is provided to face the photosensitive drum 12 at a predetermined position. A cleaner 16, a charge eliminating lamp 31, and a charging charger 13 are arranged in this order on the downstream side in the rotation direction from the developing position facing the developing device 15 of the photosensitive drum 12. A toner cartridge 32 for storing fresh toner is detachably attached to the image forming apparatus 1, and is connected to the developing device 15 via the supply motor auger 33 in the image forming device 1, thereby developing the developing device. 15 is supplied with fresh toner. The supply motor auger 33 supplies a predetermined amount of toner from the toner cartridge 32 to the developing device 15.

  Inside the developing unit 15, there are a mixer 34-1 and a mixer 34-2 for stirring and charging the toner supplied from the toner cartridge 32 via the supply motor auger 33 and the carrier previously stored in the developing unit 15. Is provided. Above the mixer 34-1 and the mixer 34-2 in the developing unit 15, a magnet inclusion for conveying a two-component developer composed of toner and carrier to the development position by being stirred and charged by the mixer 34-1 and the mixer 34-2. The developing sleeve 35 is provided. Near the lower part of the developing device 15, a magnetic sensor 36 for detecting the toner density in the developing device 15 is provided.

  The control device 37 generally controls driving of the image forming apparatus 1. The input unit 38 is provided in an upper part of the image forming apparatus 1 and has an input device such as a display panel and buttons for inputting various instructions of the user.

  In the image forming apparatus 1, for example, the rotational speed of the photosensitive drum 12 and the paper conveyance speed from the paper feeding cassette 23 are both required speeds, for example, 200 mm / sec, and the ratio of the developing sleeve 35 to the photosensitive body is 2.0. The developer is rotated up to twice the peripheral speed, and the developer is conveyed to the electrostatic latent image on the photosensitive drum 12 to form an image.

  FIG. 5 shows a schematic configuration of a control system in the image forming apparatus 1 of FIG.

  As shown in FIG. 5, an input unit 38, an environment detection unit 39, and a primary transfer roller voltage detection unit 40 are connected to the control device 37.

  The control device 37 includes a main control unit 41, a print-related data acquisition unit 42, a storage unit 43, a photosensitive drum surface potential setting unit 44, a primary transfer voltage calculation unit 45, a primary transfer voltage change unit 46, and a print number setting. A unit 47, a print number addition determination unit 48, and a set print number addition determination unit 49 are connected to each other via an input / output interface 50.

  The main control unit 41 includes a CPU (Central Processing Unit) or MPU (Micro Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and the like, and generates and supplies various control signals. The image forming apparatus 1 is comprehensively controlled.

  The print-related data acquisition unit 42 acquires and acquires print-related data from the input unit 38 or an external device (not shown) via an electric cable or the like when the user operates a display panel or a button. The printing related data is supplied to the data storage unit 51 of the storage unit 43. The print-related data includes, for example, data related to the size of paper (transfer material) on which images and characters are printed, print data of images and characters to be printed, and set print number data related to the number of prints.

  The storage unit 43 includes a data storage unit 51 and a print number database 52.

  The data storage unit 51 acquires the print-related data supplied from the print-related data acquisition unit 42 and stores the acquired print-related data. Further, the data storage unit 48 appropriately supplies various data stored in each unit of the image forming apparatus 1 in accordance with instructions from the main control unit 41.

  In the print number database 52, a voltage V0 when a predetermined current I0 set in advance is applied to the primary transfer roller 20, and an appropriate primary transfer voltage V1 calculated from the voltage V0 (hereinafter referred to as “appropriate primary”). A transfer voltage ”) is applied to the primary transfer roller 20 to register the number of post-optimized printed sheets in association with each other in advance.

  The photosensitive drum surface potential setting unit 44 controls the charging charger 13 to set the surface potential of the photosensitive drum 12 to a predetermined potential.

  The primary transfer voltage calculation unit 45 calculates an appropriate primary transfer voltage V1 based on the primary transfer roller voltage detection signal supplied from the primary transfer roller voltage detection unit 40, and calculates the calculated appropriate primary transfer voltage. Appropriate primary transfer voltage data, which is V1 data, is supplied to the primary transfer voltage changing unit 46.

  The primary transfer voltage changing unit 46 acquires appropriate primary transfer voltage data supplied from the primary transfer voltage calculating unit 45 and applies it to the primary transfer roller 20 based on the acquired appropriate primary transfer voltage data. The primary transfer voltage is changed to an appropriate primary transfer voltage V1.

  The print number setting unit 47 reads the print number database 52 of the data storage unit 43 and refers to the read print number database 52 to detect the primary transfer roller voltage supplied from the primary transfer roller voltage detection unit 40. Based on the signal, an appropriate primary transfer voltage V1 calculated from the voltage V0 is applied to the primary transfer roller 20 to set the post-optimization number of prints to be printed. The printed sheet number setting unit 47 supplies the data storage unit 51 with the optimized printed sheet number data, which is data of the set optimized printed sheet number.

  The number-of-printing-addition determining unit 48 sequentially adds the number of printed pages out of the number of printed sheets after optimization, and reads out and reads out the number of printed sheets after optimization stored in the data storage unit 51. Based on the optimized number-of-printed-sheet data, it is determined whether the added current number of printed sheets is the maximum value of the number of printed sheets after optimization set by the number-of-printed-number setting unit 47, and the determination result is the main control. Supplied to the unit 41.

  The set print number addition determination unit 49 sequentially adds the number of printed pages, reads the print related data stored in the data storage unit 51, and sets the set print number data included in the read print related data. Based on the above, it is determined whether or not the added current print number is the maximum value of the print number preset by the user, and the determination result is supplied to the main control unit 41.

  The environment detection unit 39 includes, for example, the environment sensor 28 in FIG. 3 and the like, detects an environment such as temperature and relative humidity in the image forming apparatus 1 according to an instruction from the main control unit 41, and detects the detected temperature and relative humidity. Based on the above, an environment detection signal is generated and supplied to the photosensitive drum surface potential setting unit 44. The environment detection signal includes environmental data such as temperature and relative humidity in the image forming apparatus 1.

  The primary transfer roller voltage detection unit 40 detects the voltage applied to the primary transfer roller 20, generates a primary transfer roller voltage detection signal based on the detected voltage, and sends it to the primary transfer voltage calculation unit 45. Supply.

  Here, the relationship between the electrical resistance value of the primary transfer roller 20 and the range of the appropriate primary transfer voltage will be described with reference to FIG.

As shown in FIG. 6, when the electrical resistance value of the primary transfer roller 20 is less than about 1.0 × 10 ⁷ Ω (particularly, when it is 3.0 × 10 ⁶ Ω or less), the primary transfer roller 20 Even if the electric resistance value slightly fluctuates, the appropriate range of the primary transfer voltage hardly changes, and the primary transfer voltage shows a value in the range of 500V to 1000V. However, when the electrical resistance value of the primary transfer roller 20 is about 1.0 × 10 ⁷ Ω or more, the appropriate range of the primary transfer voltage varies greatly even if the electrical resistance value of the primary transfer roller 20 slightly varies. Resulting in.

Therefore, when changing the transfer voltage applied to the primary transfer roller 20, if the electrical resistance value of the primary transfer roller 20 is less than a required resistance value, for example, less than 1.0 × 10 ⁷ Ω, a good image is obtained. Therefore, it is not necessary to frequently change the transfer voltage, but if the electrical resistance value of the primary transfer roller 20 is a required resistance value, for example, 1.0 × 10 ⁷ Ω or more, a good image is obtained. In order to achieve this, it is necessary to frequently change the transfer voltage.

This is because the transfer voltage changing process is not performed so frequently until the electrical resistance value of the primary transfer roller 20 reaches a required resistance value, for example, 1.0 × 10 ⁷ Ω or more after the start of printing. After the start, after the electric resistance value of the primary transfer roller 20 becomes a required resistance value, for example, 1.0 × 10 ⁷ Ω or more, the transfer voltage changing process is frequently performed in order to obtain a good image. This means that it is possible to change to an appropriate transfer voltage at a suitable time while preventing a decrease in printing productivity.

Specifically, when the number of printed sheets is, for example, 1000, the transfer voltage change process is performed once at the start of printing, and the transfer voltage changed by the transfer voltage change process is applied to the electrical resistance of the primary transfer roller 20. The transfer voltage changing process is not performed until the value reaches a required resistance value, for example, 1.0 × 10 ⁷ Ω or more, and printing is performed without stopping, for example, 500 sheets. Thereafter, when the electrical resistance value of the primary transfer roller 20 becomes a required resistance value, for example, 1.0 × 10 ⁷ Ω or more, the number of prints to be printed at a time is 200, 100, 50, etc. While decreasing, the transfer voltage changing process is frequently performed every time a predetermined number of printed sheets are printed. Thus, a suitable time for changing the transfer voltage to an appropriate transfer voltage is set in accordance with the environment in the image forming apparatus 1. Hereinafter, the transfer voltage changing process using the relationship between the electric resistance value of the primary transfer roller 20 and the appropriate primary transfer voltage range will be described.

  The transfer voltage changing process in the image forming apparatus 1 in FIG. 5 will be described with reference to the flowchart in FIG.

  In step S <b> 1, the main control unit 41 determines whether or not an instruction to start printing is made by the user operating the input unit 38, and printing is started by the user operating the input unit 38. Wait until it is determined that an instruction has been given.

  If it is determined in step S1 that the user has issued an instruction to start printing by operating the input unit 38, the print-related data acquisition unit 42 in step S2 causes the user to operate a display panel, a button, or the like. Print-related data is acquired from the input unit 38 or an external device (not shown) via an electric cable or the like, and the acquired print-related data is supplied to the data storage unit 51. The data storage unit 51 acquires the print-related data supplied from the print-related data acquisition unit 42 and stores the acquired print-related data.

  In step S <b> 3, the main control unit 41 generates an environment detection start control signal for starting detection of the environment, and supplies the environment detection start control signal to the environment detection unit 39. In step S4, the environment detection unit 39 detects the environment such as the temperature and relative humidity in the image forming apparatus 1 based on the environment detection start control signal supplied from the main control unit 41, and detects the detected temperature and relative humidity. An environment detection signal is generated based on humidity and the like, and supplied to the photosensitive drum surface potential setting unit 44.

  In step S <b> 5, the photosensitive drum surface potential setting unit 44 stores environmental data such as temperature and relative humidity in the image forming apparatus 1 included in the environment detection signal supplied from the environment detection unit 39, and the data storage unit 51. Based on the accumulated accumulated rotation time of the photosensitive drum 12, a charging condition potential (potential of the charging charger 13) that makes the surface potential of the photosensitive drum 12 the specified potential Vdrum is calculated.

  In step S6, the photosensitive drum surface potential setting unit 44 controls the charging charger 13 based on the calculated charging condition potential according to the control of the main control unit 41, and sets the surface potential of the photosensitive drum 12 to the specified potential Vdrum. Set.

  In step S <b> 7, the main control unit 41 controls each part of the image forming apparatus 1 such as the photosensitive drum 12 and applies a predetermined current I <b> 0 to the primary transfer roller 20. In step S8, the primary transfer roller voltage detector 40 detects a voltage V0 when a predetermined current I0 is applied to the primary transfer roller 20, and a primary transfer roller voltage detection signal based on the detected voltage V0. Is supplied to the primary transfer voltage calculation unit 45 and the print number setting unit 47. The primary transfer roller voltage detection signal includes data of the voltage V 0 detected when a predetermined current I 0 is applied to the primary transfer roller 20.

In step S9, the primary transfer voltage calculation unit 45 follows the [Equation 1] based on the primary transfer roller voltage detection signal supplied from the primary transfer roller voltage detection unit 40 according to the control of the main control unit 41. An appropriate primary transfer voltage V1 to be applied to the primary transfer roller 20 is calculated, and appropriate primary transfer voltage data that is data of the calculated appropriate primary transfer voltage V1 is supplied to the primary transfer voltage changing unit 46.
[Equation 1]
V1 = A × V0 + B
Here, symbols A and B are coefficients obtained in advance through experiments or the like in order to calculate the appropriate primary transfer voltage V1 from the voltage V0.

  In step S <b> 10, the primary transfer voltage changing unit 46 acquires appropriate primary transfer voltage data supplied from the primary transfer voltage calculating unit 45 in accordance with the control of the main control unit 41, and acquires the acquired appropriate primary transfer voltage. Based on the data, the primary transfer voltage applied to the primary transfer roller 20 is changed to an appropriate primary transfer voltage.

  In step S <b> 11, the number-of-printing-number setting unit 47 performs an appropriate calculation calculated from the voltage V <b> 0 when the preset predetermined current I <b> 0 is applied to the primary transfer roller 20 and the voltage V <b> 0 according to the control of the main control unit 41. A database managed in the print number database 52 in which the post-optimization print number for executing printing by applying the primary transfer voltage V1 to the primary transfer roller 20 is registered in advance is read.

  FIG. 8 shows a configuration example of a database managed by the print number database 52 of FIG.

  In the first column and the second column of FIG. 8, “current band (V)” and “number of printed sheets” are described, and when a predetermined current I0 is applied to the primary transfer roller 20, respectively. A current band including the voltage V0, and the number of printed sheets after optimization in which printing is performed by applying the appropriate primary transfer voltage V1 calculated from the voltage V0 to the primary transfer roller 20 are shown.

In the case of the first row in FIG. 8, the “current band (V)” is “X _{1 to} X ₂ (V)”, and includes the voltage V 0 when a predetermined current I 0 is applied to the primary transfer roller 20. It is shown that the current band of “X _{1 to} X ₂ (V)”. “Number of printed sheets” is “Y1”, and the optimized number of printed sheets for performing printing by applying the appropriate primary transfer voltage V1 calculated from the voltage V0 to the primary transfer roller 20 is “Y1”. Show.

In the second row of FIG. 8, the “current band (V)” is “X _{2 to} X ₃ (V)”, and includes the voltage V 0 when a predetermined current I 0 is applied to the primary transfer roller 20. The current band is “X _{2 to} X ₃ (V)”. The “number of printed sheets” is “Y2”, and the optimized number of printed sheets for performing printing by applying the appropriate primary transfer voltage V1 calculated from the voltage V0 to the primary transfer roller 20 is “Y2”. Show.

In the case of the third row in FIG. 8, the “current band (V)” is “X _{3 to} X ₄ (V)”, and includes the voltage V 0 when a predetermined current I 0 is applied to the primary transfer roller 20. This indicates that the current band is “X _{3 to} X ₄ (V)”. The “number of printed sheets” is “Y3”, and the optimized number of printed sheets for performing printing by applying the appropriate primary transfer voltage V1 calculated from the voltage V0 to the primary transfer roller 20 is “Y3”. Show.

In the fourth row of FIG. 8, the “current band (V)” is “X _{4 to} X ₅ (V)”, and includes the voltage V 0 when a predetermined current I 0 is applied to the primary transfer roller 20. This indicates that the current band is “X _{4 to} X ₅ (V)”. The “number of printed sheets” is “Y4”, and the optimized number of printed sheets for performing printing by applying the appropriate primary transfer voltage V1 calculated from the voltage V0 to the primary transfer roller 20 is “Y4”. Show.

In the case of the fifth row in FIG. 8, the “current band (V)” is “X _{5 to} X ₆ (V)”, and includes the voltage V 0 when a predetermined current I 0 is applied to the primary transfer roller 20. This indicates that the current band to be generated is “X _{5 to} X ₆ (V)”. The “number of printed sheets” is “Y5”, and the optimized number of printed sheets for performing printing by applying the appropriate primary transfer voltage V1 calculated from the voltage V0 to the primary transfer roller 20 is “Y5”. Show.

  Note that “Y1” to “Y5” in the “number of printed sheets” in the second column in FIG. 8 are specifically, for example, 100 sheets, 200 sheets, 300 sheets, and the like. This means that the timing of the transfer voltage changing process performed at the same time is delayed.

  In step S <b> 12, the primary transfer voltage changing unit 46 performs optimization based on the primary transfer roller voltage detection signal supplied from the primary transfer roller voltage detection unit 40 with reference to the read print number database. The post-optimization print number that is the subsequent print number is set.

Specifically, in the example of FIG. 8, in a band of the current that contains the voltage V0 when applying a predetermined current I0 to the primary transfer roller 20 "Current band" is "X ₁ to X ₂ ' In some cases, the number of printed sheets after optimization is set to “Y1”.

  Thereby, it is possible to set a suitable number of prints according to the appropriate primary transfer voltage applied to the primary transfer roller 20, and it is possible to set the timing for changing to the appropriate transfer voltage.

  More specifically, the larger the voltage V0 when the predetermined current I0 is applied to the primary transfer roller 20, the smaller the number of printed sheets after optimization.

  The printed sheet number setting unit 47 supplies the data storage unit 51 with the optimized printed sheet number data, which is data of the set optimized printed sheet number.

  In step S13, when starting the execution of printing, the main control unit 41, the current number N of prints that have been printed and the current number of prints that has been optimized out of the number of prints that have been optimized. The initial values of n are set to N = 0 and n = 0, respectively.

  In step S14, the main control unit 41 controls driving of the entire image forming apparatus 1 and executes printing. That is, the photosensitive drum 12 starts to rotate in response to an instruction from the main control unit 41 by receiving a driving force from a driving mechanism (not shown). Thereafter, the image forming operation in the image forming apparatus 1 described with reference to FIG. 3 is started, and based on print data (image to be printed or character data) included in the print-related data stored in the data storage unit 51. Then, printing is executed.

  In step S <b> 15, the set print number addition determination unit 49 increments the current print number N on which printing has been performed by 1 according to the control of the main control unit 41. In step S <b> 16, the print number addition determination unit 48 reads the set print number data relating to the print number included in the print related data stored in the data storage unit 51, and based on the set print number data relating to the read print number. Thus, it is determined whether or not the current print number N is the maximum value of the print number N preset by the user.

  If it is determined in step S16 that the current number of printed sheets N is not the maximum value of the number of printed sheets N preset by the user, the number of printed sheets addition determining unit 48 is optimized in accordance with the control of the main control unit 41 in step S17. The current number n of post-optimized prints on which printing has been performed is incremented by one.

  In step S <b> 18, the print number addition determination unit 48 reads the optimized print number data stored in the data storage unit 51, and performs the current post-optimization print based on the read post-optimization print number data. It is determined whether the number n is the maximum value of the number N of prints set by the print number setting unit 47.

  If it is determined in step S18 that the current optimized printing number n is not the maximum value of the printing number N set by the printing number setting unit 47, the process returns to step S14. Repeated. Accordingly, the appropriate primary transfer voltage V1 calculated from the voltage V0 can be applied to the primary transfer roller 20, and the optimized number of prints set by the print number setting unit 47 can be printed. Therefore, a good image can be acquired in printing the number of prints after optimization set by the print number setting unit 47.

  When it is determined in step S18 that the current post-optimization print number n is the maximum value of the post-optimization print number n set by the print number setting unit 47, the print number addition determination unit 48 sets the determination result as the main result. It supplies to the control part 41. In step S <b> 19, the main control unit 41 determines the determination result supplied from the print number addition determination unit 48 (the maximum value of the post-optimization print number n in which the current post-optimization print number n is set by the print number setting unit 47). And an environment detection start control signal for starting the detection of the environment in the image forming apparatus 1 is generated based on the set result of determination that all of the set post-optimization printing sheets n have been executed) To the unit 39. Thereafter, the process proceeds to step S4, and the transfer voltage changing process after step S4 is repeated.

  As a result, even when the electrical resistance value of the primary transfer roller 20 fluctuates due to the environment in the image forming apparatus 1 or the continuous use time, the primary transfer voltage applied to the primary transfer roller 20 is set to an appropriate 1 It is possible to execute printing by changing the primary transfer voltage to an appropriate primary voltage and applying the changed primary transfer voltage to the primary transfer roller 20.

  When it is determined in step S16 that the current print number N is the maximum value of the print number N preset by the user, the main control unit 41 ends the execution of printing in step S20. Thereby, when there is no need to perform the next transfer voltage changing process depending on the remaining number of printed sheets, the transfer voltage changing process for reducing the printing productivity can be prevented from being performed wastefully.

In the image forming apparatus 1 shown in the first embodiment of the present invention, the appropriate primary calculated from the detected voltage V0 and the voltage V0 each time the primary transfer voltage is changed to an appropriate primary transfer voltage. The primary transfer roller voltage supplied from the primary transfer roller voltage detection unit 40 with reference to the print number database in which the optimized number of prints for executing printing by applying the transfer voltage V1 is registered in advance. Since the number of printed sheets after optimization, which is the number of printed sheets after optimization, is set based on the detection signal, the appropriate range of the primary transfer voltage does not vary so much (the electrical resistance value of the primary transfer roller 20 is In the case of less than about 1.0 × 10 ⁷ Ω, it is possible to obtain a good image while performing a relatively large number of prints without reducing the printing productivity. Proper transfer voltage If circumference varies greatly (electrical resistance value of the primary transfer roller 20 is equal to or greater than approximately 1.0 × 10 ⁷ Ω), while preventing a decrease in productivity of the printing, to obtain a good image In addition, the transfer voltage can be changed frequently. Thus, it is possible to change to an appropriate transfer voltage at a suitable time while preventing a decrease in printing productivity.

  In the transfer voltage changing process described with reference to the flowchart of FIG. 7, a voltage V0 when a predetermined current I0 set in advance is applied to the primary transfer roller 20 and an appropriate value calculated from the voltage V0. Applying the primary transfer voltage V to the primary transfer roller 20 to perform printing is performed with reference to a print number database in which post-optimization print sheet numbers are registered in association with each other so as to set the post-optimization print sheet number. However, the optimized number of printed sheets may be calculated from the voltage V0 detected by the primary transfer roller voltage detecting unit 40, and the optimized number of printed sheets may be set based on the calculation result. The transfer voltage changing process in this case will be described below.

  FIG. 9 shows another schematic functional configuration of the control system in the image forming apparatus 1 of FIG. The components corresponding to the configuration of the image forming apparatus 1 in FIG. 5 are denoted by the same reference numerals, and the description thereof is omitted because it is repeated.

  The printed sheet number calculating unit 61 calculates the number of printed sheets after optimization based on the primary transfer roller voltage detection signal supplied from the primary transfer roller voltage detecting unit 40, and supplies the calculated result to the printed sheet number setting unit 47.

  The print number setting unit 47 acquires the calculation result supplied from the print number calculation unit 61, and sets the optimized print number based on the acquired calculation result. The printed sheet number setting unit 47 supplies the data storage unit 51 with the optimized printed sheet number data, which is data of the set optimized printed sheet number.

  The transfer voltage changing process in the image forming apparatus 1 in FIG. 9 will be described with reference to the flowchart in FIG. Note that the processes in steps S31 to S40 and steps S43 to S50 in FIG. 10 are the same as the processes in steps S1 to S10 and steps S13 to S20 in FIG.

In step S41, the number-of-print-sheets calculation unit 61 calculates the optimized number of prints according to [Equation 2] based on the primary transfer roller voltage detection signal supplied from the primary transfer roller voltage detection unit 40, and calculates the calculation result. This is supplied to the print number setting unit 47.
[Equation 2]
Number of printed sheets after optimization = C x D- ^{(E x V0)}
Here, symbols C, D, and E are coefficients obtained in advance by experiments or the like in order to calculate the number of printed sheets after optimization from the voltage V0.

  For example, when C = 1115, D = 2.72, and E = −0.0008, when V0 = 600 (V), the number of printed sheets after optimization is 689. Similarly, when V0 = 800 (V), 1200 (V), 2000 (V), and 3000 (V), the number of printed sheets after optimization is 587, 426, 224, and 100, respectively. It becomes.

  In step S42, the print number setting unit 47 acquires the calculation result supplied from the print number calculation unit 61, and sets the post-optimization print number based on the acquired calculation result. As a result, a suitable number of printed sheets can be set by an appropriate primary transfer voltage applied to the primary transfer roller 20, and the timing for changing to an appropriate transfer voltage can be set more suitably.

  The printed sheet number setting unit 47 supplies the data storage unit 51 with the optimized printed sheet number data, which is data of the set optimized printed sheet number.

In the transfer voltage changing process described with reference to the flowchart of FIG. 10, every time the primary transfer voltage is changed to an appropriate primary transfer voltage, the appropriate number of prints after optimization based on the detected voltage V0. Since the number of printed sheets after calculation is calculated and set based on the calculated number of printed sheets after optimization, the appropriate range of the primary transfer voltage does not vary so much (the electrical resistance value of the primary transfer roller 20 is In the case of less than about 1.0 × 10 ⁷ Ω, it is possible to obtain a good image while performing a relatively large number of prints without reducing the printing productivity. When the appropriate range of the secondary transfer voltage fluctuates greatly (when the electrical resistance value of the primary transfer roller 20 is about 1.0 × 10 ⁷ Ω or more), it is good while preventing a decrease in printing productivity. To get a good image The copying voltage can be changed frequently. Thereby, it is possible to change to an appropriate transfer voltage at a more suitable time while preventing a decrease in printing productivity.

  In the image forming apparatus 1 shown in the embodiment of the present invention, the voltage V0 when the predetermined current I0 is applied to the primary transfer roller 20 is detected. The current I0 when the voltage V0 is applied may be detected. In that case, the smaller the current I0 when the predetermined voltage V0 is applied to the primary transfer roller 20, the smaller (shorter) the number of printed sheets (change time) after optimization.

  In the image forming apparatus 1 shown in the embodiment of the present invention, the number of print sheets is counted. However, the present invention is not limited to such a case. For example, the rotation amount (several number of photosensitive drums) other than the number of print sheets. ) Or driving time may be counted. In addition, the number of sheets, the rotation amount, the driving time, and the like are collectively referred to as a printing amount.

  The present invention is applied to the primary transfer voltage applied to the primary transfer roller 20 in the intermediate transfer system. However, the present invention is not limited to this. For example, the present invention is applied to the secondary transfer roller 22 in the intermediate transfer system. Alternatively, the transfer belt method (a method in which the paper is carried on the transfer belt) or the transfer method in which a transfer member is installed on the opposite surface of the paper to transfer the toner image on the photosensitive member. You may make it apply.

  Furthermore, in the image forming apparatus 1 shown in the embodiment of the present invention, the surface potential of the photosensitive drum 12 is set to a specified potential by the environmental sensor 28 provided in the image forming apparatus 1. For example, a surface potential sensor may be provided on the downstream side of the charging charger 13 to directly detect the surface potential of the photosensitive drum 12.

  In the image forming apparatus 1 shown in the embodiment of the present invention, the voltage V0 when the predetermined current I0 is applied to the primary transfer roller 20 and the number of printed sheets are registered in association with the printed number database 52 in advance. However, for example, the appropriate primary transfer voltage V1 and the number of prints may be registered in advance in the print number database 52.

  In the embodiment of the present invention, by setting the number of printed sheets according to the appropriate primary transfer voltage applied to the primary transfer roller 20, a suitable timing for changing to the appropriate transfer voltage is set. However, the present invention is not limited to such a case. For example, by setting a predetermined time during which a predetermined appropriate primary transfer voltage is applied to the primary transfer roller 20, it is preferable to change the transfer voltage to an appropriate transfer voltage. A suitable time may be set.

  In the embodiment of the present invention, the steps of the flowchart show examples of processing performed in time series in the order described, but parallel or individual execution is not necessarily performed in time series. The processing to be performed is also included.

The figure explaining the environmental dependence of the electrical resistance value of a primary transfer roller. The figure explaining the fluctuation | variation by continuous use of the electrical resistance value of a secondary transfer roller. 1 is a block diagram showing a schematic mechanical configuration of a cross section of an image forming apparatus to which the present invention is applied. FIG. 4 is a block diagram showing a schematic mechanical configuration inside the process cartridge of FIG. 3. FIG. 4 is a block diagram showing a schematic functional configuration of a control system inside the image forming apparatus of FIG. 3. The figure explaining the relationship between the electrical resistance value of a primary transfer roller, and the range of an appropriate primary transfer voltage. 6 is a flowchart for describing a transfer voltage changing process in the image forming apparatus 1 of FIG. The figure which shows the structural example of the database managed by the printing number database of FIG. FIG. 4 is a block diagram showing another schematic functional configuration of a control system inside the image forming apparatus of FIG. 3. 10 is a flowchart for describing a transfer voltage changing process in the image forming apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Scanner part 3 Image forming part 4 Paper feeding part 11a thru | or 11d Process cartridge 12a thru | or 12d Photosensitive drum 13a thru | or 13d Charger 14a thru | or 14d Exposure apparatus 15a thru | or 15d Developing device 16a thru | or 16d Cleaner 17 Intermediate transfer belt 18 Driving roller 19 Secondary transfer counter roller 20a to 20d Primary transfer roller 21 Intermediate transfer belt cleaner 22 Secondary transfer roller 23 Paper feed cassette 24 Pickup roller 25 Registration roller pair 26 Fixing device 27 Tension roller 28 Environmental sensor 29 Power supply 31 Static elimination lamp 32 toner cartridge 33 supply motor auger 34-1 to 34-2 mixer 35 developing sleeve 36 magnetic sensor 37 control device 38 input unit 39 environment detection unit 40 primary transfer roller voltage detection unit 41 main control unit 42 printing related data acquisition unit 43 Storage Unit 44 Photosensitive Drum Surface Potential Setting Unit 45 Primary Transfer Voltage Calculation Unit 46 Primary Transfer Voltage Change Unit 47 Printed Number Setting Unit 48 Printed Sheet Addition Determination Unit 49 Set Printed Sheet Number Addition Determination Unit 50 Input / Output Interface 51 Data Storage Section 52 Number of printed sheets database 61 Number of printed sheets calculation section

Claims (8)

Transfer means for transferring a toner image on the image carrier;
A power supply for applying a transfer voltage to the transfer means;
A transfer voltage calculating means for calculating a transfer voltage applied to the transfer means;
A transfer voltage changing means for changing a transfer voltage applied to the transfer means by the power source based on a calculation result by the transfer voltage calculating means;
A change time setting means for setting a change time for changing the transfer voltage applied to the transfer means by the transfer voltage changing means;
Detecting means for detecting a voltage when a preset predetermined current is applied to the transfer means, or a current when a preset predetermined voltage is applied to the transfer means;
With
The change time setting means sets the change time based on the voltage or the current detected by the detection means.
An image forming apparatus. The change time setting means is detected by the detection means with reference to a change time database in which a voltage when a predetermined current set in advance to the transfer means is applied and the change time are registered in advance. The image forming apparatus according to claim 1, wherein the change time is set based on the applied voltage. 3. The change time registered in association with the change time database in advance becomes shorter as the voltage when a predetermined current set in advance is applied to the transfer unit is larger. The image forming apparatus described. The change time registered in association with the change time database in advance is divided into a plurality of categories according to a voltage when a predetermined current set in advance is applied to the transfer means. Item 3. The image forming apparatus according to Item 2. The change time setting unit calculates a change time based on the voltage detected by the detection unit, and sets the change time based on the calculated change time. Image forming apparatus. The change time setting means is detected by the detection means with reference to a change time database in which the current when the predetermined voltage set in advance to the transfer means is applied and the change time are registered in advance. The image forming apparatus according to claim 1, wherein the change time is set based on the applied current. 7. The change time registered in advance in association with the change time database becomes shorter as the current when a predetermined voltage set in advance is applied to the transfer means is smaller. The image forming apparatus described. In an image forming method of an image forming apparatus, comprising: a transfer unit that transfers a toner image on an image carrier; and a power source that applies a transfer voltage to the transfer unit.
A transfer voltage calculating step for calculating a transfer voltage applied to the transfer portion;
A transfer voltage changing step of changing a transfer voltage applied to the transfer portion by the power source based on a calculation result of the transfer voltage calculating step;
A change time setting step for setting a change time for changing the transfer voltage applied to the transfer portion by the processing of the transfer voltage change step;
A detection step of detecting a voltage when a preset predetermined current is applied to the transfer portion , or a current when a preset predetermined voltage is applied to the transfer portion ;
With
The change time setting step sets the change time based on the voltage or the current detected by the detection step .
An image forming method.

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