Image forming apparatus and image forming method

Abstract

To suppress the deterioration of printing quality due to the influence of heat.SOLUTION: The image forming apparatus 1 stores, as the history high temperature TH, the highest internal temperature TN to which the toner in the toner cartridge 31 has been exposed in the past print processing, and stores, as the high-temperature drum rotation number DH, the drum rotation number DR while the internal temperature TN is higher than the deterioration temperature TD. Further, when performing a printing process, the image forming device 1 reads out the adjustment value corresponding to the history high temperature TH and the high-temperature drum rotation number DH from the adjustment value table TB1, adjusts the charging voltage, and prints an image based on the print job. As a result, the image forming apparatus 1 can appropriately correct the charging voltage according to the magnitude of the damage to the toner in the toner cartridge 31 due to heat in the past, and can satisfactorily suppress the occurrence of contamination or fogging on the sheet P on which an image is printed, thereby suppressing the deterioration of the print quality.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus and an image forming method, and is suitable for application to, for example, an electrophotographic image forming apparatus (so-called printer). [Background technology]

[0002] Conventionally, electrophotographic image forming devices have been widely used in which a toner image is formed using toner (also called developer) on the surface of a photosensitive drum (also called image carrier) in an image forming unit, and this toner image is then transferred from the photosensitive drum to a medium such as paper and fixed thereon, thereby printing an image. The image forming unit utilizes the electrostatic property of toner to apply different high voltages to multiple rollers, etc., and uses the voltage difference between the various parts to move (transfer) the developer while forming a toner image, which is then transferred to the surface of the medium.

[0003] However, when the amount of toner remaining in a toner cartridge containing the toner decreases, the toner tends to aggregate due to an increase in charging voltage, deterioration, etc., which may result in the toner being transferred to unwanted areas of the medium, causing stains and other problems that could lead to a decline in print quality. Therefore, an image forming device has been proposed that corrects the high voltage applied to each part depending on the amount of toner remaining in the toner cartridge (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-3313 A (Fig. 12, etc.) Summary of the Invention [Problem to be solved by the invention]

[0005] However, in recent years, for example, as the speed of image formation processing increases, the temperature inside the image forming device has risen and the low-temperature fixability of toner has improved, which can make the toner more susceptible to damage by heat. For this reason, when the remaining amount of low-temperature fixable toner in the toner cartridge decreases, simply correcting the high voltage may not be enough to adequately prevent the occurrence of smudges, etc., and may not be able to prevent a decline in print quality.

[0006] The present invention has been made in consideration of the above points, and aims to propose an image forming apparatus and an image forming method that can prevent deterioration of print quality due to the influence of heat. [Means for solving the problem]

[0007] In order to solve this problem, the image forming apparatus of the present invention is provided with an image carrier that carries a latent image, a charging member that is applied with a charging voltage and uniformly charges the image carrier, a developer carrier that is applied with a developing voltage and supplies developer to the image carrier to cause it to be carried, a developer supplier that is applied with a supply voltage and supplies developer to the developer carrier, a sensor that detects temperature, a temperature drive amount acquisition unit that acquires a temperature drive amount that represents the amount by which the image carrier is driven when the temperature detected by the sensor satisfies a predetermined temperature condition, and a control unit that controls the charging voltage, supply voltage, and developing voltage, and the control unit controls to correct at least one of the charging voltage, supply voltage, and developing voltage according to the temperature detected by the sensor and the temperature drive amount acquired by the temperature drive amount acquisition unit.

[0008] Furthermore, the image forming method of the present invention includes a temperature detection step of detecting temperature by a sensor, a temperature drive amount acquisition step of acquiring a temperature drive amount representing the amount by which the image carrier carrying the latent image has been driven when the temperature detected by the sensor satisfies a predetermined temperature condition, and a control step of controlling by a control unit a charging voltage applied to a charging member that uniformly charges the image carrier, a developing voltage applied to a developer carrier that supplies developer to the image carrier and causes it to carry the developer, and a supply voltage applied to a developer supply member that supplies developer to the developer carrier, and the control unit step controls to correct at least one of the charging voltage, supply voltage, and development voltage according to the temperature detected by the temperature detection step and the temperature drive amount acquired by the temperature drive amount acquisition step.

[0009] The present invention stores the amount by which the image carrier was driven under the temperature conditions in a previous image formation process as a temperature drive amount, and corrects at least one of the charging voltage, supply voltage, and developing voltage based on the detected temperature and temperature drive amount. This allows the present invention to appropriately correct the charging voltage, etc., to an appropriate degree according to the amount of heat damage the developer received in the previous image formation process. [Effects of the Invention]

[0010] According to the present invention, it is possible to realize an image forming apparatus and an image forming method that can suppress deterioration of print quality due to the influence of heat. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus. [Figure 2] FIG. 2 is a schematic diagram illustrating a configuration of an image forming unit. [Figure 3] FIG. 2 is a schematic block diagram illustrating a circuit configuration of the image forming apparatus. [Figure 4] 10A and 10B are schematic diagrams showing the relationship between the drum rotation speed and the charge amount of toner, and the relationship between the temperature after printing and the charge amount of toner. [Figure 5]5 is a schematic diagram showing the relationship between the drum rotation speed and the internal temperature in each comparative example and each example in the first embodiment. FIG. [Figure 6] 4 is a schematic diagram illustrating the configuration of a correction value table in the first embodiment. FIG. [Figure 7] FIG. 2 is a schematic diagram showing a paper sheet used in an evaluation test. [Figure 8] 5 is a schematic diagram showing the results of an evaluation test and an overall evaluation in the first embodiment. [Figure 9] 4 is a flowchart showing a printing process procedure according to the first embodiment. [Figure 10] 10 is a schematic diagram showing the relationship between the drum rotation speed and the internal temperature in each comparative example and each example in the second embodiment. FIG. [Figure 11] 10 is a schematic diagram illustrating the configuration of a correction value table according to the second embodiment. [Figure 12] 10 is a schematic diagram showing the results of an evaluation test and an overall evaluation in the second embodiment. [Figure 13] 10 is a flowchart showing a printing process procedure according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

[0013] 1. First Embodiment [1-1. External and hardware configuration of image forming device] As shown in a schematic side view in Figure 1, the image forming apparatus 1 according to the first embodiment is configured as an electrophotographic printer that forms (i.e., prints) an image on the surface of paper as a medium while transporting the paper.

[0014] In the following, the side of the image forming device 1 that the user faces will be referred to as the front side, and the opposite side will be referred to as the rear side. The left and right sides as seen from the user facing the front side will be referred to as the left and right sides, respectively, and the upper and lower sides will be further defined and explained.

[0015] The image forming apparatus 1 is broadly composed of a main body 2 at the front and a paper feed unit 3 at the rear. The main body 2 has a control unit 5 therein that controls the entire apparatus, and an operation unit 7 and a display unit 8 provided at the front of the upper part of the main body 2. The operation unit 7 is made up of, for example, a plurality of buttons and is a unit that accepts operations by the user. The display unit 8 is made up of, for example, a liquid crystal panel and is a unit that displays various information such as the status of the image forming apparatus 1.

[0016] The paper feed unit 3 has, from the rear side, a roll holder 11, a paper cut sensor 12, a pair of conveying rollers 13, a cutter unit 14, etc., and a conveying path W3 is formed along the front-to-rear direction. Each part of the paper feed unit 3 is controlled by the control unit 5 of the main body 2.

[0017] The roll holder 11 rotatably holds a roll of paper RP, which is a cylindrical roll of long paper LP. This long paper LP has black marks printed on the back side at predetermined intervals along the length of the roll. When the long paper LP is peeled off from the outermost periphery of the roll of paper RP, it travels forward along the transport path W3.

[0018] The paper cut sensor 12 is an optical sensor that detects a mark printed on the back side of the long sheet LP and notifies the control unit 5 of the main body 2. In response, the control unit 5 supplies a cutting instruction to the cutter unit 14 to cut the long sheet LP. The transport roller pair 13 clamps the long sheet LP between transport rollers arranged above and below the transport path W3, and transports the long sheet LP forward along the transport path W3 by rotating the transport rollers. The cutter unit 14 has a transport roller pair 14A and a cutter 14B, and cuts the long sheet LP with the cutter 14B in response to a cutting instruction supplied from the control unit 5. Hereinafter, the cut portion of the long sheet LP will be referred to as paper P.

[0019] Inside the main body 2, a transport path W2 is formed along the front-to-rear direction, through which the paper P passes, and various components of the electrophotographic printer are arranged along this transport path W2. Specifically, inside the main body 2, from the rear to the front, that is, from the upstream side to the downstream side of the transport path W2 along which the paper P is transported, there are provided a transport roller pair 21, a paper output sensor 22, a belt transport unit 23, image forming units 24C, 24M, and 24Y, a fixing unit 25, a discharge roller pair 26, and a paper output sensor 27.

[0020] The transport roller pair 21 is configured similarly to the transport roller pair 13, etc., and transports the paper P forward while sandwiching it. The paper writing sensor 22 has a rotating lever, a spring, an optical sensor, etc., and detects the leading edge of the paper P transported along the transport path W2, and notifies the control unit 5 of a writing detection signal representing the obtained detection result.

[0021] The belt conveying unit 23 is disposed below the conveying path W2 and extends over a relatively long range in the front-to-rear direction. The belt conveying unit 23 has an endless conveying belt 23C wound around rollers 23A and 23B disposed at the front and rear sides, respectively. The belt conveying unit 23 rotates the rollers 23A and 23B to move the upper surface of the conveying belt 23C forward. Transfer rollers 28C, 28M, and 28Y (hereinafter collectively referred to as transfer rollers 28) are provided directly below the image forming units 24C, 24M, and 24Y in the belt conveying unit 23, i.e., on the opposite side of the conveying belt 23C.

[0022] The three image forming units 24C, 24M and 24Y (hereinafter collectively referred to as image forming units 24) correspond to the three colors of toner handled by the image forming device 1, and are arranged in a line in the front-to-back direction above the belt conveying section 23, i.e., above the conveying path W2.

[0023] 2, each image forming unit 24 has a toner cartridge 31, an image drum (ID) unit 32, an exposure head 33, etc. The toner cartridge 31, which serves as a developer container, has a space therein for storing toner (also called developer), and supplies the toner into the ID unit 32 from a supply port formed on the lower side surface.

[0024] The ID unit 32 has a toner storage space 41 for storing toner inside an ID unit housing 40 that forms the outer shell, and below or behind it, a supply roller 42, a developing roller 43, a developing blade 44, a photosensitive drum 45, a charging roller 46, a charging cleaning roller 47, a cleaning member 48, etc. are appropriately arranged.

[0025] When the toner cartridge 31 is attached to the top of the ID unit housing 40, the toner storage space 41 stores therein the toner supplied from the toner cartridge 31. A toner agitator (not shown) is provided in the toner storage space 41, and by appropriately agitating the stored toner, the toner is prevented from clumping and the toner is smoothly supplied to the supply roller 42 and the like.

[0026] The supply roller 42, developing roller 43, photosensitive drum 45, charging roller 46, and charging cleaning roller 47 are all configured in a columnar or cylindrical shape with their central axes aligned in the left-right direction, and are rotatably supported. These rollers, drums, etc. are rotated by a driving force supplied from a photosensitive drum motor 68 (FIG. 3), which will be described later.

[0027] The supply roller 42, which serves as a developer supply body, is disposed at the bottom within the toner storage space 41. The developing roller 43 is disposed diagonally above and behind the supply roller 42, in a position where it abuts against the supply roller 42 and the photosensitive drum 45, respectively. The supply roller 42 and the developing roller 43 are both formed in a cylindrical shape with their central axes aligned in the left-right direction and are supported so as to be rotatable about their respective central axes. A supply voltage and a developing voltage, which are predetermined high voltages, are applied to the supply roller 42 and the developing roller 43, respectively. The developing blade 44 is formed in a thin plate shape, with one end fixed to the ID unit housing 40 and the other end abutting against the peripheral side surface of the developing roller 43, and exerting an elastic force on the developing roller 43.

[0028] The photosensitive drum 45, which serves as an image carrier, is cylindrically shaped with its central axis aligned in the left-right direction and is supported rotatably about its central axis. A thin-film charge generating layer and a charge transport layer are sequentially formed on the peripheral surface of the photosensitive drum 45, enabling it to be charged. The charging roller 46, which serves as a charging unit, is cylindrically shaped with its central axis aligned in the left-right direction and is supported rotatably, and is provided so as to abut the upper front side of the photosensitive drum 45. The charging cleaning roller 47 is disposed above the charging roller 46 so as to abut against the charging roller 46. The charging cleaning roller 47 rotates in accordance with the rotation of the charging roller 46 or rotates at a different peripheral speed.

[0029] The exposure head 33, also referred to as an exposure unit, is formed in the shape of a long, thin rod extending in the left-right direction and is located above the photosensitive drum 45. This exposure head 33 has a plurality of light-emitting diode (LED) elements arranged in the main scanning direction (i.e., the left-right direction), and also has a rod lens array, etc. When the LED elements are appropriately illuminated under the control of an exposure control unit 67 (FIG. 3) described below, the exposure head 33 irradiates the light downward while converging the light, forming an image near the upper end of the circumferential side of the photosensitive drum 45, thereby exposing the surface of the photosensitive drum 45 and forming an electrostatic latent image.

[0030] The cleaning member 48 is provided in front of the photosensitive drum 45 and is made of a flexible resin material in the shape of a thin plate. The cleaning member 48 has a front end fixed to the ID unit housing 40 and a rear end that abuts against the peripheral side surface of the photosensitive drum 45.

[0031] In this configuration, when performing printing processing, each image forming unit 24 (24C, 24M, and 24Y) rotates the developing roller 43, charging roller 46, and transfer roller 28 of the ID unit 32 in the direction of arrow R2, and rotates the photosensitive drum 45 and supply roller 42 in the direction of arrow R1, based on the control of the control unit 5.

[0032] At the same time, under the control of the control unit 5, the image forming unit 24 supplies predetermined high voltages to the developing roller 43, the supply roller 42, the developing blade 44, the charging roller 46, and the transfer roller 28 from the developing voltage control unit 61, the supply voltage control unit 62, the layer formation voltage control unit 63, the charging voltage control unit 64, and the transfer voltage control unit 65 (Figure 3).

[0033] Supply roller 42 is charged to cause toner in toner storage space 41 to adhere to its peripheral surface, and rotation causes this toner to adhere to the peripheral surface of developing roller 43. After excess toner is removed from the peripheral surface of developing roller 43 by developing blade 44 to form a thin layer of toner, developing roller 43 brings this thin layer of toner into contact with the peripheral surface of photosensitive drum 45.

[0034] Furthermore, the charging roller 46 contacts the photosensitive drum 45 in a charged state, thereby uniformly charging the circumferential surface of the photosensitive drum 45. At this time, the charging cleaning roller 47 scrapes off the toner and external additives of the toner adhering to the charging roller 46.

[0035] Meanwhile, the control unit 5 generates print data based on a print job received from the higher-level device 100 (FIG. 3), and supplies this print data as dot data for each line from the exposure control unit 67 (FIG. 3) to the exposure head 33. The exposure head 33 emits light in an emission pattern based on the supplied dot data, exposing the photosensitive drum 45. As a result, an electrostatic latent image is formed on the peripheral side surface of the photosensitive drum 45 near its upper end.

[0036] Next, photosensitive drum 45 rotates in the direction of arrow R1, bringing the area where the electrostatic latent image is formed into contact with developing roller 43. As a result, toner is deposited on the circumferential surface of photosensitive drum 45 based on the electrostatic latent image, and a toner image based on the image data is developed. As photosensitive drum 45 rotates, the developed toner image reaches the area where it is sandwiched with transfer roller 28, i.e., the transfer position on transport path W2.

[0037] At this time, when paper P is being transported along transport path W2, image forming unit 24 (FIG. 1) charges paper P with a high voltage applied to transfer roller 28, and due to potential differences between various parts, transfers a toner image from the circumferential side surface of photosensitive drum 45 onto paper P. In this way, image forming unit 24 can form a toner image based on print data and transfer the toner image onto paper P being transported from the front along transport path W2.

[0038] In this connection, in the image forming unit 24, if toner remains on the circumferential surface of the photosensitive drum 45 after it has passed through the transfer area, the cleaning member 48 scrapes off the toner.

[0039] The fixing unit 25 is located downstream of the image forming unit 24Y and has a heating roller and a pressure roller positioned opposite each other across the conveyance path W2. The fixing unit 25 fixes the toner image onto the paper P by applying heat and pressure to the paper P onto which the toner image has been transferred.

[0040] The discharge roller pair 26 is composed of two transport rollers arranged vertically opposite each other across the transport path W2 on the downstream side (front side) of the fixing unit 25, and the paper P that has passed through the fixing unit 25 is sandwiched between the transport rollers and transported, thereby discharging it to the front side of the main body unit 2. The paper discharge sensor 27 detects whether or not the paper P is present. When the paper discharge sensor 27 detects the presence of the paper P, this means that the paper P is being discharged from the image forming apparatus 1.

[0041] Next, the circuit configuration of the image forming apparatus 1 will be described using the block diagram shown in Fig. 3. The control unit 5 of the image forming apparatus 1 has, as its internal functional components, a print control unit 51 and a temperature drive amount acquisition unit 52. The control unit 5 is also connected to a CPU (Central Processing Unit) 53, a memory 54, an interface unit 57, a temperature and humidity sensor 58, an operation unit 7, and a density sensor 59. The control unit 5 is also connected to a process control unit 60, a development voltage control unit 61, a supply voltage control unit 62, a layer formation voltage control unit 63, a charging voltage control unit 64, a transfer voltage control unit 65, a motor control unit 66, and an exposure control unit 67.

[0042] The print control unit 51 cooperates with the CPU 53 and other components to comprehensively control each component when executing the print process. The CPU 53 performs various arithmetic operations. The memory 54 has a ROM (Read Only Memory) 55 and a RAM (Random Access Memory) 56. The ROM 55 is, for example, a rewritable flash memory, and stores various programs and various setting values. In addition, the ROM 55 is provided with an internal device temperature recording unit, an internal device humidity recording unit, a transfer belt temperature recording unit, and a date and time recording unit. The RAM 56 is provided with an internal device temperature recording unit, an internal device humidity recording unit, a transfer belt temperature recording unit, and a date and time recording unit.

[0043] The interface unit 57 is, for example, an interface such as a wired LAN (Local Area Network), a wireless LAN, or a USB (Universal Serial Bus). The interface unit 57 transmits and receives various information to a host device 100, which is a computer or the like. For example, when the interface unit 57 receives a print job from the host device 100, it supplies the print job to the print control unit 51. The print control unit 51 performs predetermined expansion processing, color conversion processing, and the like based on the print job to generate print data for cyan (C), magenta (M), and yellow (Y), and supplies the print data to the exposure control unit 67.

[0044] The temperature and humidity sensor 58 is a sensor that detects the temperature and humidity inside the main body 2, and supplies information indicating the detected temperature (hereinafter referred to as the internal temperature TN) and humidity to the control unit 5. The density sensor 59 is disposed below the belt conveying unit 23, and detects the toner density of the toner image of the test pattern transferred from each image forming unit 24 to the conveying belt 23C, and supplies information indicating the obtained density to the control unit 5.

[0045] The process control unit 60 controls the voltages applied to each roller based on instructions from the print control unit 51. The development voltage control unit 61 controls the development voltage, which is a high voltage applied to the development roller 43. The supply voltage control unit 62 controls the supply voltage, which is a high voltage applied to the supply roller 42. The layer formation voltage control unit 63 controls the layer formation voltage, which is a high voltage applied to the development blade 44. The charging voltage control unit 64 controls the charging voltage, which is a high voltage applied to the charging roller 46. The transfer voltage control unit 65 controls the transfer voltage, which is a high voltage applied to the transfer roller 28.

[0046] Motor control unit 66 controls photosensitive drum motor 68. This photosensitive drum motor 68 generates a driving force based on the control of motor control unit 66 and supplies the driving force to photosensitive drum 45 of each image forming unit 24 to rotate it. Incidentally, image forming unit 24 (FIG. 2) is configured so that driving force can be transmitted between supply roller 42, developing roller 43, photosensitive drum 45, charging roller 46, etc., by gears or the like (not shown). Therefore, in image forming unit 24, supply roller 42, developing roller 43, charging roller 46, etc. also rotate in conjunction with photosensitive drum 45.

[0047] The exposure control unit 67 controls the exposure process by appropriately causing each LED element of the exposure head 33 to emit light based on the print data supplied from the print control unit 51 .

[0048] In addition, the temperature drive amount acquisition unit 52, which serves as a developer remaining rate acquisition unit, acquires the internal temperature TN detected by the temperature and humidity sensor 58, the dot count CD which is the number of toner dots used in each toner cartridge 31, the drum rotation number DR which is the rotation number of the photosensitive drum 45 in each ID unit 32, etc. each time a printing process is performed.

[0049] Of these, the dot count CD is a value used to calculate the toner remaining rate RE, which indicates the proportion of toner remaining in each toner cartridge 31. For example, it is calculated by counting the number of dots that use toner in print data for each color generated based on print job data. This toner remaining rate RE is expressed as a percentage, with the amount of toner in a new toner cartridge 31 being 100%. For convenience of explanation, the toner remaining rate RE will also be referred to as the developer remaining rate hereinafter.

[0050] The drum rotation count DR is calculated as the rotation count of the photosensitive drum 45 by counting the number of times the photosensitive drum motor 68 is rotated by the motor control unit 66 and multiplying this count by a predetermined coefficient based on the gear ratio of the gears (not shown) in each ID unit 32.

[0051] [1-2. Evaluation tests and preliminary experiments] In the image forming apparatus 1, the toner contained in the toner cartridge 31 and the toner containing space 41 of the ID unit 32 tends to aggregate when the toner deteriorates due to heat transmitted from the surroundings during printing, etc. When printing is performed using aggregated toner, so-called "fog" or "stains" may occur on the printed paper P, potentially resulting in a decrease in print quality. In addition, in the image forming apparatus 1, the degree of deterioration of the toner in the toner cartridge 31 is thought to progress according to the cumulative amount of time the toner is exposed to relatively high temperatures.

[0052] It is believed that such stains occur because the fluidity of toner decreases in a high-temperature environment, making it more likely to aggregate, and a large amount of toner with reduced chargeability adheres to the surface of developing roller 43. In other words, in this case, the amount of toner developed in accordance with the potential difference between developing roller 43 and photosensitive drum 45 increases more than usual, and even toner that should not have been developed ends up being developed, which is thought to result in stains appearing on the printed paper P.

[0053] In the image forming apparatus 1, the internal temperature TN detected by the temperature and humidity sensor 58 can be considered to be the temperature to which the toner in the toner cartridge 31 is exposed. Also, in the image forming apparatus 1, with respect to the integrated value of time, the drive amount (i.e., the number of rotations) of the photosensitive drum 45 can be considered to be roughly proportional to the time required for the printing process.

[0054] Therefore, in the image forming apparatus 1, if the internal temperature TN exceeds a predetermined degradation temperature TD (for example, 20°C, hereinafter also referred to as the temperature threshold) when a print job was executed in the past, the internal temperature TN is stored as a historical high temperature TH. Also, in the image forming apparatus 1, the drum rotation speed DR while the internal temperature TN exceeds the degradation temperature TD is calculated as the rotation speed of the photosensitive drum 45 in a high-temperature environment (hereinafter referred to as the high-temperature drum rotation speed DH) and is integrated.

[0055] The historical high temperature TH and the high temperature drum rotation speed DH are initialized when the toner cartridge 31 is replaced, so that the influence of heat on the toner contained in the toner cartridge 31 is reflected. These processes are performed by the temperature drive amount acquisition unit 52 (FIG. 3).

[0056] Then, preliminary experiments were conducted under several conditions to examine the relationship between the historical high temperature TH, the high-temperature drum rotation speed DH, and the toner charge amount using the image forming apparatus 1. The conditions were six in total, combining two conditions, one where the remaining amount of toner in the toner cartridge (TC) 31 was relatively high and one where it was relatively low, and three conditions where the toner was exposed to temperatures of 20°C, 35°C, and 40°C.

[0057] The results of this preliminary experiment were summarized and the graph shown in Figure 4(A) was obtained. From this graph in Figure 4(A), it can be seen that when the temperature to which the toner in the toner cartridge 31 is exposed exceeds approximately 20°C, the toner charge decreases, making the toner easier to develop. From the graph in Figure 4(A), it can also be seen that the toner charge varies depending on the temperature to which the toner is exposed. Furthermore, it can be seen that the toner charge tends to decrease as the value of the high-temperature drum rotation speed DH increases. On the other hand, as shown by the dashed line in Figure 4(A), it was also found that as long as the charge exceeds -10 μC, there are almost no problems with print quality when printing.

[0058] Therefore, in the image forming device 1, it is possible to change the high voltage during development depending on the historical high temperature TH and the high-temperature drum rotation speed DH, specifically, to correct the absolute value of the high voltage applied to each roller such as the charging roller 46 so as to decrease it.

[0059] Here, the degradation temperature TD, which is the reference temperature for detecting the historical high temperature TH, was set to 20°C as a temperature according to the characteristics of the toner contained in the toner cartridge 31, based on the results of the preliminary experiment shown in Fig. 4(A). In the following, the degradation temperature TD is also referred to as the temperature condition, and if the internal temperature of the image forming apparatus 1 is higher than the degradation temperature TD, it is considered that this temperature condition is met.

[0060] The high voltage to be corrected is the charging voltage applied to the charging roller 46. This charging voltage is generally set to a negative high voltage such as -1000 V, but it is desirable to correct it so that the charging voltage is increased (the absolute value is reduced) in order to prevent "fogging" and "staining."

[0061] Next, evaluation tests were conducted by printing predetermined evaluation test images on paper P for five comparative examples and 14 examples in which the conditions for the historical high temperature TH and the high-temperature drum rotation speed DH were variously changed using the image forming apparatus 1. In the first embodiment, each evaluation test was conducted when the toner remaining rate RE in each toner cartridge 31 was 50% or higher.

[0062] Specifically, in this evaluation test, the historical high temperature TH was divided into 5°C intervals between 20°C and 40°C, and the high-temperature drum rotation speed DH was divided into 250 rotation intervals between 250 rotations and 1250 rotations.

[0063] In this evaluation test, after several preliminary tests, six comparative examples C1-1 to C1-6 (hereinafter collectively referred to as comparative example C1) were carried out, each of which had different combinations of the historical high temperature TH and the high-temperature drum rotation speed DH, as shown in Figure 5(A). In this comparative example C1, the charging voltage was not corrected.

[0064] In addition, in this evaluation test, 15 examples E1-1 to E1-15 (hereinafter collectively referred to as example E1) were carried out, each having a different combination of the historical high temperature TH and the high-temperature drum rotation speed DH, as shown in Fig. 5(B). In example E1, the charging voltage was corrected using a correction value corresponding to the combination of the historical high temperature TH and the high-temperature drum rotation speed DH, in accordance with correction value table TB1 shown in Fig. 6.

[0065] In this correction value table TB1, the correction value is "0" when the historical high temperature TH is relatively low and the high-temperature drum rotation speed DH is relatively low, and the correction value is greater than "0" in other areas. Specifically, in correction value table TB1, if the historical high temperature TH is 20°C or less, the correction value is "0" regardless of the high-temperature drum rotation speed DH. Also, in correction value table TB1, if the historical high temperature TH is greater than 20°C but less than 25°C, the correction value is "0" when the high-temperature drum rotation speed DH is 1250 rpm or less. Conversely, if the historical high temperature TH is greater than 25°C but less than 30°C, the correction value is "0" when the high-temperature drum rotation speed DH is 1000 rpm or less. Furthermore, in the correction value table TB1, if the historical high temperature TH is higher than 30°C and lower than 35°C, the correction value is "0" when the high-temperature drum rotation speed DH is 750 rotations or less, and if the historical high temperature TH is higher than 35°C and lower than 40°C, the correction value is "0" when the high-temperature drum rotation speed DH is 500 rotations or less. Furthermore, in the correction value table TB1, the correction value is "0" when the historical high temperature TH is higher than 40°C and the high-temperature drum rotation speed DH is 250 rotations or less.

[0066] From another perspective, in the correction value table TB1, the correction value becomes a value other than "0" and the charging voltage is corrected only when the historical high temperature TH is higher than 20°C. Also, in the correction value table TB1, the correction value becomes a value other than "0" and the charging voltage is corrected only when the high-temperature drum rotation speed DH is greater than 250 rotations. Therefore, 250 rotations will be referred to as the temperature driving amount threshold below.

[0067] In addition, in the correction value table TB1, if the high-temperature drum rotation speed DH is constant, the higher the historical high temperature TH, the larger the correction value, and further, if the historical high temperature TH is constant, the higher the high-temperature drum rotation speed DH, the larger the correction value.

[0068] Specific evaluation test conditions for Comparative Examples C1-1 to C1-6 and Examples E1-1 to E1-15 are as follows:

[0069] <Comparative Example C1-1> When the historical high temperature TH was greater than 20°C and less than 25°C, the high temperature drum rotation speed DH was greater than 1250 rotations, and the toner remaining rate RE was greater than 50%, the printing process was performed without correcting the charging voltage.

[0070] <Comparative Example C1-2> When the historical high temperature TH was higher than 25°C and lower than 30°C, the high temperature drum rotation speed DH was higher than 1000 rpm and lower than 1250 rpm, and the toner remaining rate RE was 50% or higher, the printing process was performed without correcting the charging voltage.

[0071] <Comparative Example C1-3> When the historical high temperature TH was higher than 25°C and lower than 30°C, the high temperature drum rotation speed DH was greater than 1250 rotations, and the toner remaining rate RE was 50% or higher, the printing process was performed without correcting the charging voltage.

[0072] <Comparative Example C1-4> When the historical high temperature TH was higher than 30°C and lower than 35°C, the high temperature drum rotation speed DH was higher than 750 rotations and lower than 1000 rotations, and the toner remaining rate RE was 50% or higher, the printing process was performed without correcting the charging voltage.

[0073] <Comparative Example C1-5> When the historical high temperature TH was higher than 35°C and lower than 40°C, the high temperature drum rotation speed DH was higher than 500 rotations and lower than 750 rotations, and the toner remaining rate RE was 50% or higher, the printing process was performed without correcting the charging voltage.

[0074] <Comparative Example C1-6> When the historical high temperature TH was higher than 40°C, the high temperature drum rotation speed DH was greater than 250 rotations and less than 500 rotations, and the toner remaining rate RE was 50% or more, the printing process was performed without correcting the charging voltage.

[0075] <Example E1-1> When the historical high temperature TH was higher than 20°C and lower than 25°C, the high temperature drum rotation speed DH was greater than 1250 rotations, and the toner remaining rate RE was 50% or higher, the charging voltage was corrected to be increased by 5V, and the printing process was performed.

[0076] <Example E1-2> When the historical high temperature TH was higher than 25°C and lower than 30°C, the high temperature drum rotation speed DH was higher than 1000 rpm and lower than 1250 rpm, and the toner remaining rate RE was 50% or higher, the charging voltage was corrected to be increased by 5V, and the printing process was performed.

[0077] <Example E1-3> When the historical high temperature TH was higher than 25°C and lower than 30°C, the high temperature drum rotation speed DH was greater than 1250 rotations, and the toner remaining rate RE was 50% or higher, the charging voltage was corrected to be increased by 10V, and the printing process was performed.

[0078] <Example E1-4> When the historical high temperature TH was higher than 30°C and lower than 35°C, the high temperature drum rotation speed DH was higher than 750 rpm and lower than 1000 rpm, and the toner remaining rate RE was 50% or higher, the charging voltage was corrected to be increased by 5 V, and the printing process was performed.

[0079] <Example E1-5> When the historical high temperature TH was higher than 30°C and lower than 35°C, the high temperature drum rotation speed DH was higher than 1000 rpm and lower than 1250 rpm, and the toner remaining rate RE was 50% or higher, the charging voltage was corrected to be increased by 10 V, and the printing process was performed.

[0080] <Example E1-6> When the historical high temperature TH was higher than 30°C and lower than 35°C, the high temperature drum rotation speed DH was greater than 1250 rotations, and the toner remaining rate RE was 50% or higher, the charging voltage was corrected to be increased by 15V, and the printing process was performed.

[0081] <Example E1-7> When the historical high temperature TH was higher than 35°C and lower than 40°C, the high temperature drum rotation speed DH was higher than 500 rotations and lower than 750 rotations, and the toner remaining rate RE was 50% or higher, the charging voltage was corrected to be increased by 5V, and the printing process was performed.

[0082] <Example E1-8> When the historical high temperature TH was higher than 35°C and lower than 40°C, the high temperature drum rotation speed DH was higher than 750 rotations and lower than 1000 rotations, and the toner remaining rate RE was 50% or higher, the charging voltage was corrected to be increased by 10V, and the printing process was performed.

[0083] <Example E1-9> When the historical high temperature TH was greater than 35°C and less than 40°C, the high temperature drum rotation speed DH was greater than 1000 rpm and less than 1250 rpm, and the toner remaining rate RE was 50% or greater, the charging voltage was corrected to be increased by 15V, and the printing process was performed.

[0084] <Example E1-10> When the historical high temperature TH was higher than 35°C and lower than 40°C, the high temperature drum rotation speed DH was greater than 1250 rotations, and the toner remaining rate RE was 50% or higher, the charging voltage was corrected to be increased by 20V, and the printing process was performed.

[0085] <Example E1-11> When the historical high temperature TH was higher than 40°C, the high temperature drum rotation speed DH was greater than 250 rotations and less than 500 rotations, and the toner remaining rate RE was 50% or more, the charging voltage was corrected to be increased by 5V, and the printing process was performed.

[0086] <Example E1-12> When the historical high temperature TH was higher than 40°C, the high temperature drum rotation speed DH was greater than 500 rotations and less than 750 rotations, and the toner remaining rate RE was 50% or more, the charging voltage was corrected to be increased by 10V, and the printing process was performed.

[0087] <Example E1-13> When the historical high temperature TH was higher than 40°C, the high temperature drum rotation speed DH was greater than 750 rotations and less than 1000 rotations, and the toner remaining rate RE was 50% or higher, the charging voltage was corrected to be increased by 15V, and the printing process was performed.

[0088] <Example E1-14> When the historical high temperature TH was higher than 40°C, the high temperature drum rotation speed DH was greater than 1000 rotations and less than 1250 rotations, and the toner remaining rate RE was 50% or more, the charging voltage was corrected to be increased by 20V, and the printing process was performed.

[0089] <Example E1-15> When the historical high temperature TH was higher than 40°C, the high temperature drum rotation speed DH was greater than 1250 rotations, and the toner remaining rate RE was 50% or higher, the charging voltage was corrected to be increased by 25V, and the printing process was performed.

[0090] Next, an evaluation of the paper P printed in Comparative Example C1 and Example E1 will be described. In this evaluation test, a stain evaluation and a color difference evaluation were carried out.

[0091] For the stain evaluation, as shown in Fig. 7(A), a stain evaluation image PE made up of a single color cyan with a print image density of 50% was printed on paper P, and an observer visually inspected the paper P. Then, the stain was evaluated using three levels: "not generated," "partially generated," and "generated," and these were expressed with the symbols "○," "△," and "×," as shown in Fig. 8.

[0092] The evaluation "not occurring" represented by the symbol "○" means that the stain was not visible on the paper P, and therefore the evaluation was made that no stain occurred. The evaluation "partial occurrence" represented by the symbol "△" means that when the observer looked closely at the paper P, the printed part appeared dark, and therefore the evaluation was made that the density of part of the printed evaluation image PE was high. The evaluation "occurred" represented by the symbol "×" means that the stain was visible on the paper P, and therefore the evaluation was made that stain occurred.

[0093] On the other hand, for the color difference evaluation, as shown in Fig. 7(B), a color difference evaluation image PW in which all pixels were colorless (white) was printed on paper P, and evaluation was performed based on the color difference (ΔE) between it and unprinted paper (not shown) that had not been subjected to printing processing. Specifically, an X-Rite 528 (manufactured by X-Rite) was used to measure the color difference, and the color value of the unprinted paper was set to (L1, a1, b1) and the color value of the evaluation paper P was set to (L2, a2, b2), and the color difference ΔE was calculated using the following formula (1):

[0094]

number

[0095] An evaluation was then made according to the color difference ΔE value, and the results are shown in Figure 8 along with the color difference ΔE value. Specifically, if the color difference ΔE was 0.50 or less, it was considered to be in a good condition where no fog was visible to the naked eye, and was represented by the symbol "○". If the color difference ΔE was greater than 0.50 and less than 1.00, the fog was visible if the eye was squinted, but was not noticeable, and it was considered to be within the acceptable range, and was represented by the symbol "△". Furthermore, if the color difference ΔE was greater than 1.00, it was considered to be in a poor condition where the fog was visible to the naked eye, and was represented by the symbol "X".

[0096] Furthermore, in Fig. 8, an overall evaluation was made for each Comparative Example C1 and each Example E1. This overall evaluation was expressed in three levels: a symbol "◎" indicating a sufficient effect, a symbol "◯" indicating a certain degree of effect, and a symbol "×" indicating no effect.

[0097] Specifically, if the judgment results for both the stain evaluation and the color difference evaluation were the symbol "○", the symbol was marked "◎", if at least one of the judgment results was the symbol "×", the symbol was marked "×", and if at least one of the judgment results was the symbol "△", the symbol was marked "○".

[0098] 8, in each comparative example C1, the overall evaluation was "X." In other words, under these conditions, since the charging voltage was not corrected, smudges and fogging occurred on the printed paper P, and print quality was reduced.

[0099] On the other hand, as can be seen from Figure 8, in each Example E1, the overall evaluation was either "○" or "◎". In other words, under these conditions, correcting the charging voltage suppressed smearing and fogging on the printed paper P, and it was possible to suppress a decline in print quality.

[0100] Therefore, in the image forming device 1, by correcting the correction voltage using the correction value obtained from the correction value table TB1 (Figure 6) according to the high-temperature drum rotation speed DH and the historical high temperature TH, it is possible to appropriately suppress the occurrence of stains and fogging on the printed paper P and prevent a decrease in print quality.

[0101] Therefore, the image forming apparatus 1 stores the correction value table TB1 in advance in the memory 54, and reads out the correction value corresponding to the historical high temperature TH and the high-temperature drum rotation speed DH from the correction value table TB1.

[0102] Incidentally, Figure 4(B) shown next is a graph showing the relationship between the temperature drop over time and the charge amount of the toner after the toner in the toner cartridge 31 was exposed to high temperatures (35°C or 45°C) as another preliminary experiment.

[0103] 4(B) shows that in the image forming apparatus 1, even if the toner in the toner cartridge 31 is exposed to high temperatures and the charge amount decreases, the charge amount of the toner recovers to some extent as the temperature decreases over time. In particular, when the temperature decreases to 20°C, the charge amount of the toner recovers to above -10 μC, so it is thought that there will be almost no deterioration in print quality when a printing process is performed.

[0104] This means that in the image forming device 1, even if the charging voltage is corrected in response to the toner in the toner cartridge 31 being exposed to high temperatures, if the temperature drops to about 20°C over time, the charge amount of the toner will have recovered, and the charging voltage should be returned to its original value.

[0105] [1-3. Printing process procedure] Next, a description will be given of the printing process performed by the image forming apparatus 1. When the control unit 5 of the image forming apparatus 1 receives a print job from the upper device 100 (FIG. 3), it reads and executes a print program from the memory 54, thereby starting the printing process procedure RT1 shown in FIG. 9, and proceeds to the first step SP1.

[0106] In step SP1, the control unit 5 performs an acceptance process for the received print job, and then proceeds to the next step SP2. This acceptance process involves generating print data based on the print job data, etc. In step SP2, the control unit 5 reads and acquires the historical high temperature TH and the high-temperature drum rotation speed DH from the memory 54, and then proceeds to the next step SP3.

[0107] In step SP3, the control unit 5 determines whether the historical high temperature TH is higher than 20°C. If a positive result is obtained here, this indicates that the toner in the toner cartridge 31 is exposed to a relatively high temperature, and therefore the charging voltage needs to be corrected depending on the value of the high-temperature drum rotation speed DH. In this case, the control unit 5 proceeds to the next step SP4.

[0108] In step SP4, the control unit 5 determines whether the high-temperature drum rotation speed DH is greater than 250 [rpm]. If a positive result is obtained here, this indicates that the toner in the toner cartridge 31 has been exposed to a relatively high temperature for a relatively long time, and therefore the charging voltage needs to be corrected. In this case, the control unit 5 proceeds to the next step SP5.

[0109] In step SP5, the control unit 5 refers to the correction value table TB1 stored in the memory 54, reads out the correction value corresponding to the historical high temperature TH and the high-temperature drum rotation speed DH, corrects the charging voltage using the correction value, and then proceeds to the next step SP6.

[0110] In step SP6, control unit 5 executes the print job accepted in step SP1, and then proceeds to the next step SP7. Specifically, control unit 5 forms a toner image in image forming unit 24 based on the print data generated based on the print job, transfers the toner image to paper P, and causes fixing unit 25 to fix the toner image to paper P.

[0111] In step SP7, the control unit 5 updates the values ​​of the historical high temperature TH and the high-temperature drum rotation speed DH based on the internal temperature TN and the drum rotation speed DR when the print job was executed in step SP6, and then proceeds to the next step SP8. In step SP8, the control unit 5 obtains the latest internal temperature TN and proceeds to the next step SP9.

[0112] In step SP9, the control unit 5 determines whether the latest internal temperature TN is greater than 20°C. If a positive result is obtained here, this indicates that the temperature inside the toner cartridge 31 remains relatively high, and therefore the corrected charging voltage should be maintained as is. In this case, the control unit 5 proceeds to the next step SP14.

[0113] On the other hand, if a negative result is obtained in step SP9, this indicates that the temperature inside the toner cartridge 31 has dropped sufficiently and there is no longer any need to correct the charging voltage. In this case, the control unit 5 proceeds to the next step SP10. In step SP10, the control unit 5 returns the charging voltage to the normal value and proceeds to the next step SP14.

[0114] On the other hand, if a negative result is obtained in step SP3, this indicates that the historical high temperature TH is lower than 20°C, and therefore the toner in the toner cartridge 31 is unlikely to have deteriorated. In this case, the control unit 5 proceeds to the next step SP11.

[0115] If a negative result is obtained in step SP4, this indicates that the high-temperature drum rotation speed DH is less than 250 [rpm], and therefore the toner in the toner cartridge 31 is unlikely to have deteriorated. In this case, the control unit 5 proceeds to the next step SP11.

[0116] In step SP11, the control unit 5 sets the charging voltage to a normal value and proceeds to the next step SP12. In step SP12, the control unit 5 executes the print job accepted in step SP1, as in step SP6, and proceeds to the next step SP13. In step SP13, the control unit 5 updates the values ​​of the historical high temperature TH and the high-temperature drum rotation speed DH, as in step SP7, and proceeds to the next step SP14.

[0117] In step SP14, the control unit 5 determines whether or not the next print job has been received from the host device 100. If a positive result is obtained here, the control unit 5 returns to step SP1 to repeat the series of processes in order to execute the next print job. On the other hand, if a negative result is obtained in step SP14, the control unit 5 proceeds to the next step SP15 and ends the print processing procedure RT1.

[0118] [1-4. Effects, etc.] In the above configuration, the image forming apparatus 1 according to the first embodiment regards the highest internal temperature TN to which the toner in the toner cartridge 31 was exposed in past printing processes as the historical high temperature TH, and also calculates the drum rotation speed DR while the internal temperature TN is higher than the degradation temperature TD as the high temperature drum rotation speed DH, and stores each of these in the memory 54.

[0119] Then, when the image forming device 1 receives a new print job, if the historical high temperature TH is higher than 20°C and the high temperature drum rotation speed DH is higher than 250 rotations, it reads a correction value corresponding to these values ​​from the correction value table TB1 (Figure 6), corrects the charging voltage, and then prints an image based on the print job.

[0120] This allows the image forming device 1 to correct the charging voltage using an appropriate correction value according to the temperature and length of time to which the toner in the toner cartridge 31 has been exposed in the past, thereby effectively preventing stains and fogging on the paper P on which the image has been printed and suppressing a decline in print quality.

[0121] In other words, by using the historical high temperature TH and the high temperature drum rotation speed DH, the image forming device 1 can determine the degree of heat damage that the toner in the toner cartridge 31 has suffered during printing processing based on past print jobs, and can obtain an appropriate correction amount according to the degree of this damage.

[0122] From another perspective, the image forming apparatus 1 reads out the correction value for the charging voltage from the correction value table TB1 (FIG. 6) based on the high-temperature drum rotation speed DH in addition to the historical high temperature TH. This allows the image forming apparatus 1 to select an appropriate correction value for the charging voltage based on both the length of time that the toner in the toner cartridge 31 has been exposed to high temperatures, which is represented by the high-temperature drum rotation speed DH, and the historical high temperature TH.

[0123] In addition, in the image forming apparatus 1, after executing a print job by correcting the charging voltage based on the values ​​of the historical high temperature TH and the high-temperature drum rotation speed DH, if the internal temperature TN is 20°C or less, the charging voltage is returned to the normal value. This allows the image forming apparatus 1 to apply an appropriate charging voltage when the charge amount of the toner has recovered to a certain extent due to a drop in temperature, thereby preventing a deterioration in print quality due to the occurrence of blurring, etc.

[0124] With the above configuration, the image forming apparatus 1 determines the highest internal temperature TN to which the toner in the toner cartridge 31 was exposed in past printing processes as the historical high temperature TH, and calculates and stores the drum rotation speed DR while the internal temperature TN was above the degradation temperature TD as the high-temperature drum rotation speed DH. Furthermore, when performing printing, the image forming apparatus 1 reads a correction value corresponding to the historical high temperature TH and the high-temperature drum rotation speed DH from the correction value table TB1 to correct the charging voltage and print an image based on the print job. This allows the image forming apparatus 1 to appropriately correct the charging voltage according to the extent of heat damage previously caused to the toner in the toner cartridge 31, effectively reducing the occurrence of smearing and fogging on the paper P on which the image has been printed and reducing degradation of print quality.

[0125] 2. Second Embodiment Image forming apparatus 201 according to the second embodiment differs from image forming apparatus 1 according to the first embodiment in that it has control unit 205 instead of control unit 5, but is otherwise configured similarly.

[0126] The control unit 205 (FIG. 3) differs from the control unit 5 according to the first embodiment in that it has a memory 254 instead of the memory 54, but is otherwise configured similarly. The memory 254 stores programs and data that are partially different from those stored in the memory 54 according to the first embodiment (this will be described in detail later).

[0127] [2-1. Evaluation tests and preliminary experiments] In the second embodiment, unlike the first embodiment, a plurality of evaluation tests were conducted when the remaining amount of toner in the toner cartridge 31 was relatively small, specifically, when it was less than 50%.

[0128] In this evaluation test, after several preliminary tests, six comparative examples C2-1 to C2-6 (hereinafter collectively referred to as comparative example C2) were carried out, each having a different combination of the hysteresis high temperature TH and the high-temperature drum rotation speed DH, as shown in Figure 10(A) corresponding to Figure 4(A). In this comparative example C2, the charging voltage was not corrected, as in the first embodiment.

[0129] In addition, in the evaluation test of the second embodiment, 20 examples E2-1 to E2-20 (hereinafter collectively referred to as example E2) were carried out, each having different combinations of the historical high temperature TH and the high-temperature drum rotation speed DH, as shown in Fig. 10(B) corresponding to Fig. 4(B). In example E2, the charging voltage was corrected using a correction value corresponding to the combination of the historical high temperature TH and the high-temperature drum rotation speed DH, in accordance with correction value table TB2 shown in Fig. 11 corresponding to Fig. 5.

[0130] In this correction value table TB2, similar to the correction value table TB1 (FIG. 6), when the historical high temperature TH is relatively low and the high-temperature drum rotation speed DH is relatively low, the correction value is "0," and in other areas the correction value is greater than "0." However, in the correction value table TB2, there are fewer combinations of the historical high temperature TH and the high-temperature drum rotation speed DH that result in a value of "0" compared to the correction value table TB1.

[0131] In addition, in the correction value table TB2, as in the case of the correction value table TB1 (FIG. 6), if the high-temperature drum rotation speed DH is constant, the higher the historical high temperature TH, the larger the correction value, and further, if the historical high temperature TH is constant, the higher the high-temperature drum rotation speed DH, the larger the correction value. Looking more closely, the correction values ​​in the correction value table TB2 are each larger than the correction values ​​in the correction value table TB1 when the historical high temperature TH and the high-temperature drum rotation speed DH are the same.

[0132] Specific evaluation test conditions for Comparative Examples C2-1 to C2-6 and Examples E2-1 to E2-20 are as follows:

[0133] <Comparative Example C2-1> When the historical high temperature TH was greater than 20°C and less than 25°C, the high temperature drum rotation speed DH was greater than 1000 rpm and less than 1250 rpm, and the toner remaining rate RE was less than 50%, the printing process was performed without correcting the charging voltage.

[0134] <Comparative Example C2-2> When the historical high temperature TH was greater than 20°C and less than 25°C, the high temperature drum rotation speed DH was greater than 1250 rotations, and the toner remaining rate RE was less than 50%, the printing process was performed without correcting the charging voltage.

[0135] <Comparative Example C2-3> When the historical high temperature TH was greater than 25°C and less than 30°C, the high temperature drum rotation speed DH was greater than 750 rotations and less than 1000 rotations, and the toner remaining rate RE was less than 50%, the printing process was performed without correcting the charging voltage.

[0136] <Comparative Example C2-4> When the historical high temperature TH was greater than 30°C and less than 35°C, the high temperature drum rotation speed DH was greater than 500 rotations and less than 750 rotations, and the toner remaining rate RE was less than 50%, the printing process was performed without correcting the charging voltage.

[0137] <Comparative Example C2-5> When the historical high temperature TH was greater than 35°C and less than 40°C, the high temperature drum rotation speed DH was greater than 250 rotations and less than 500 rotations, and the toner remaining rate RE was less than 50%, the printing process was performed without correcting the charging voltage.

[0138] <Comparative Example C2-6> When the historical high temperature TH was higher than 40°C, the high temperature drum rotation speed DH was 250 rotations or less, and the toner remaining rate RE was less than 50%, the printing process was performed without correcting the charging voltage.

[0139] <Example E2-1> When the historical high temperature TH was greater than 20°C and less than 25°C, the high temperature drum rotation speed DH was greater than 1000 rpm and less than 1250 rpm, and the toner remaining rate RE was less than 50%, the charging voltage was corrected to be increased by 5 V, and the printing process was performed.

[0140] <Example E2-2> When the historical high temperature TH was greater than 20°C and less than 25°C, the high temperature drum rotation speed DH was greater than 1250 rotations, and the toner remaining rate RE was less than 50%, the charging voltage was corrected to be increased by 10 V, and the printing process was performed.

[0141] <Example E2-3> When the historical high temperature TH was higher than 25°C and lower than 30°C, the high temperature drum rotation speed DH was higher than 750 rotations and lower than 1000 rotations, and the toner remaining rate RE was less than 50%, the charging voltage was corrected to be increased by 5V, and the printing process was performed.

[0142] <Example E2-4> When the historical high temperature TH was greater than 25°C and less than 30°C, the high temperature drum rotation speed DH was greater than 1000 rpm and less than 1250 rpm, and the toner remaining rate RE was less than 50%, the charging voltage was corrected to be increased by 10 V, and the printing process was performed.

[0143] <Example E2-5> When the historical high temperature TH was higher than 25°C and lower than 30°C, the high temperature drum rotation speed DH was greater than 1250 rotations, and the toner remaining rate RE was less than 50%, the charging voltage was corrected to be increased by 15V, and the printing process was performed.

[0144] <Example E2-6> When the historical high temperature TH was greater than 30°C and less than 35°C, the high temperature drum rotation speed DH was greater than 500 rpm and less than 750 rpm, and the toner remaining rate RE was less than 50%, the charging voltage was corrected to be increased by 5 V, and the printing process was performed.

[0145] <Example E2-7> When the historical high temperature TH was greater than 30°C and less than 35°C, the high temperature drum rotation speed DH was greater than 750 rpm and less than 1000 rpm, and the toner remaining rate RE was less than 50%, the charging voltage was corrected to be increased by 10 V, and the printing process was performed.

[0146] <Example E2-8> When the historical high temperature TH was greater than 30°C and less than 35°C, the high temperature drum rotation speed DH was greater than 1000 rpm and less than 1250 rpm, and the toner remaining rate RE was less than 50%, the charging voltage was corrected to be increased by 15 V, and the printing process was performed.

[0147] <Example E2-9> When the historical high temperature TH was higher than 30°C and lower than 35°C, the high temperature drum rotation speed DH was greater than 1250 rotations, and the toner remaining rate RE was less than 50%, the charging voltage was corrected to be increased by 20V, and the printing process was performed.

[0148] <Example E2-10> When the historical high temperature TH was greater than 35°C and less than 40°C, the high temperature drum rotation speed DH was greater than 250 rotations and less than 500 rotations, and the toner remaining rate RE was less than 50%, the charging voltage was corrected to be increased by 5V, and the printing process was performed.

[0149] <Example E2-11> When the historical high temperature TH was greater than 35°C and less than 40°C, the high temperature drum rotation speed DH was greater than 500 rpm and less than 750 rpm, and the toner remaining rate RE was less than 50%, the charging voltage was corrected to be increased by 10 V, and the printing process was performed.

[0150] <Example E2-12> When the historical high temperature TH was greater than 35°C and less than 40°C, the high temperature drum rotation speed DH was greater than 750 rpm and less than 1000 rpm, and the toner remaining rate RE was less than 50%, the charging voltage was corrected to be increased by 15 V, and the printing process was performed.

[0151] <Example E2-13> When the historical high temperature TH was greater than 35°C and less than 40°C, the high temperature drum rotation speed DH was greater than 1000 rpm and less than 1250 rpm, and the toner remaining rate RE was less than 50%, the charging voltage was corrected to be increased by 20 V, and the printing process was performed.

[0152] <Example E2-14> When the historical high temperature TH was higher than 35°C and lower than 40°C, the high temperature drum rotation speed DH was greater than 1250 rotations, and the toner remaining rate RE was less than 50%, the charging voltage was corrected to be increased by 25V, and the printing process was performed.

[0153] <Example E2-15> When the historical high temperature TH was higher than 40°C, the high temperature drum rotation speed DH was 250 rpm or less, and the toner remaining rate RE was less than 50%, the charging voltage was corrected to be increased by 5 V, and the printing process was performed.

[0154] <Example E2-16> When the historical high temperature TH was higher than 40°C, the high temperature drum rotation speed DH was greater than 250 rotations and less than 500 rotations, and the toner remaining rate RE was less than 50%, the charging voltage was corrected to be increased by 10 V, and the printing process was performed.

[0155] <Example E2-17> When the historical high temperature TH was higher than 40°C, the high temperature drum rotation speed DH was greater than 500 rotations and less than 750 rotations, and the toner remaining rate RE was less than 50%, the charging voltage was corrected to be increased by 15 V, and the printing process was performed.

[0156] <Example E2-18> When the historical high temperature TH was higher than 40°C, the high temperature drum rotation speed DH was greater than 750 rotations and less than 1000 rotations, and the toner remaining rate RE was less than 50%, the charging voltage was corrected to be increased by 20 V, and the printing process was performed.

[0157] <Example E2-19> When the historical high temperature TH was higher than 40°C, the high temperature drum rotation speed DH was greater than 1000 rotations and less than 1250 rotations, and the toner remaining rate RE was less than 50%, the charging voltage was corrected to be increased by 25 V, and the printing process was performed.

[0158] <Example E2-20> When the historical high temperature TH was higher than 40°C, the high temperature drum rotation speed DH was greater than 1250 rotations, and the toner remaining rate RE was less than 50%, the charging voltage was corrected to be increased by 30 V, and the printing process was performed.

[0159] Then, for the paper P printed by these comparison example C2 and example E2, a stain evaluation and a color difference evaluation were performed in the same manner as in the first embodiment, and an overall judgment was also performed. The evaluation results and judgment results shown in FIG. 12, which corresponds to FIG. 7, were obtained.

[0160] 12, in each comparative example C2, the overall evaluation was "X" as in the first embodiment. In other words, under these conditions, since the charging voltage was not corrected, stains and fogging occurred on the printed paper P, and print quality was reduced.

[0161] 12, in each example E2, the overall evaluation was either "○" or "◎", similar to the first embodiment. In other words, under these conditions, correcting the charging voltage suppressed smearing and fogging on the printed paper P, and it was possible to suppress a decline in print quality.

[0162] Therefore, in the image forming device 201, if the toner remaining rate RE is less than 50%, the correction voltage is corrected using the correction value obtained from the correction value table TB2 (Figure 11) according to the high-temperature drum rotation speed DH and the historical high temperature TH, thereby appropriately suppressing the occurrence of stains and fogging on the printed paper P and preventing a decrease in print quality.

[0163] On the other hand, in the image forming device 201, if the toner remaining rate RE is 50% or more, as in the first embodiment, the correction voltage is corrected using the correction value obtained from the correction value table TB1 (Figure 6) according to the high-temperature drum rotation speed DH and the historical high temperature TH, thereby appropriately suppressing the occurrence of stains and fogging on the printed paper P and preventing a decrease in print quality.

[0164] Therefore, the image forming apparatus 1 stores a correction value table TB2 (FIG. 11) in advance in the memory 254 in addition to the correction value table TB1 (FIG. 6) similar to that in the first embodiment.

[0165] [2-2. Printing process procedure] Next, a description will be given of the printing process by the image forming apparatus 201. When the control unit 205 of the image forming apparatus 201 receives a print job from the upper device 100 (FIG. 3), it reads and executes a print program from the memory 254, thereby starting a printing process procedure RT2 shown in FIG. 13, which corresponds to FIG. 9, and proceeding to the first step SP21.

[0166] In step SP21, the control unit 205 performs acceptance processing for the received print job, similar to step SP1 (FIG. 9), and proceeds to the next step SP22. In step SP22, the control unit 205 reads and acquires the historical high temperature TH, the high-temperature drum rotation number DH, and the dot count CD from the memory 54, and proceeds to the next step SP23.

[0167] In step SP23, the control unit 205 calculates the remaining toner rate RE of the toner cartridge 31 based on the dot count CD, and then proceeds to the next step SP24. Specifically, the control unit 205 stores in the memory 54 the total dot count corresponding to all the toner at the start of use of the toner cartridge 31, and calculates the remaining toner rate RE by subtracting the dot count CD from the total dot count and dividing the result by the total dot count.

[0168] In step SP24, the control unit 205 determines whether the historical high temperature TH is higher than 20° C., similarly to step SP3 (FIG. 9). If a positive result is obtained here, the control unit 205 proceeds to the next step SP25.

[0169] In step SP25, the control unit 205 determines whether the toner remaining rate RE calculated in step SP23 is 50% or more. If a positive result is obtained here, this indicates that a correction value for when the remaining toner amount is relatively large should be used. In this case, the control unit 205 proceeds to the next step SP26, selects correction value table TB1 (FIG. 6, hereinafter also referred to as the high remaining rate correction table) as the correction value table to refer to, and proceeds to the next step SP28.

[0170] On the other hand, if a negative result is obtained in step SP25, this indicates that the correction value for when the remaining toner amount is relatively low should be used. In this case, the control unit 205 proceeds to the next step SP27, selects correction value table TB2 (FIG. 11, hereinafter also referred to as the low remaining rate correction table) as the correction value table to refer to, and proceeds to the next step SP28.

[0171] In step SP28, the control unit 205 refers to the correction value table TB1 or TB2 stored in the memory 54, reads out the correction value corresponding to the values ​​of the historical high temperature TH and the high-temperature drum rotation speed DH, corrects the charging voltage using the correction value, and proceeds to the next step SP29.

[0172] In step SP29, the control unit 205 executes the print job accepted in step SP21, as in step SP6, and then proceeds to the next step SP30. In step SP30, the control unit 5 updates the values ​​of the historical high temperature TH, the high-temperature drum rotation speed DH, and the dot count CD based on the internal temperature TN, the drum rotation speed DR, and the number of dots used when the print job was executed in step SP29, and then proceeds to the next step SP31.

[0173] In step SP31, the control unit 205 acquires the latest internal temperature TN and proceeds to the next step SP32. In step SP33, the control unit 205 determines whether the latest internal temperature TN is greater than 20°C, as in step SP9. If a positive result is obtained here, the control unit 205 proceeds to the next step SP37.

[0174] On the other hand, if a negative result is obtained in step SP32, the control section 205 proceeds to the next step SP33, where it returns the charging voltage to the normal value, and then proceeds to the next step SP37.

[0175] On the other hand, if a negative result is obtained in step SP34, it indicates that there is a low possibility that the toner in the toner cartridge 31 has deteriorated. In this case, the control section 5 proceeds to the next step SP34.

[0176] In step SP34, the control unit 205 sets the charging voltage to a normal value, and then proceeds to the next step SP35. In step SP35, the control unit 205 executes the print job accepted in step SP21, as in step SP29, and then proceeds to the next step SP36. In step SP36, the control unit 205 updates the values ​​of the historical high temperature TH, the high-temperature drum rotation speed DH, and the dot count CD, as in step SP30, and then proceeds to the next step SP37.

[0177] In step SP37, the control unit 205 determines whether or not the next print job has been received from the host device 100. If a positive result is obtained here, the control unit 205 returns to step SP21 to repeat the series of processes in order to execute the next print job. On the other hand, if a negative result is obtained in step SP38, the control unit 205 proceeds to the next step SP38 and ends the print processing procedure RT2.

[0178] [2-3. Effects, etc.] In the above configuration, the image forming apparatus 201 according to the second embodiment, like the first embodiment, stores in memory 254 the historical high temperature TH, the high temperature drum rotation speed DH, and the dot count CD since the toner cartridge 31 was last replaced when performing a printing process.

[0179] That is, the image forming apparatus 201 stores the highest internal temperature TN to which the toner in the toner cartridge 31 has been exposed as the historical high temperature TH. The image forming apparatus 201 also integrates the drum rotation count DR while the internal temperature TN is above the degradation temperature TD as the high-temperature drum rotation count DH, and stores this in the memory 254. The image forming apparatus 201 also stores the integrated value of the number of dots used in each printing process as the dot count CD in the memory 254.

[0180] As a result, the image forming device 201, like the first embodiment, can correct the charging voltage using an appropriate correction value according to the temperature and length of time to which the toner in the toner cartridge 31 has been exposed in the past, thereby effectively suppressing the occurrence of dirt and fogging on the paper P on which the image has been printed and preventing a decrease in print quality.

[0181] In particular, the image forming apparatus 201 switches between referring to the correction value table TB1 (FIG. 6) and referring to the correction value table TB2 (FIG. 11) depending on whether the toner remaining rate RE of the toner cartridge 31 exceeds 50%. Therefore, compared to the first embodiment, the image forming apparatus 201 can correct the charging voltage using a more appropriate correction value according to the toner remaining rate RE.

[0182] Furthermore, when the toner remaining rate RE of the toner cartridge 31 is less than 50%, the image forming apparatus 201 can refer to the correction value table TB2 to set a larger correction value than when the toner remaining rate RE is 50% or more (i.e., when the correction value table TB1 is referred to). This allows the image forming apparatus 201 to set a relatively large correction range for the charging voltage when the amount of toner remaining in the toner cartridge 31 is decreasing and the toner charge is expected to be increasing, and to bring the charging voltage closer to an appropriate value.

[0183] In other respects as well, the image forming apparatus 201 according to the second embodiment can achieve the same effects as the image forming apparatus 1 according to the first embodiment.

[0184] 3. Other Embodiments In the first embodiment described above, when fog or stains occur on the printed paper P, the charging voltage is a high negative voltage (for example, -1000 V), and the charging voltage is corrected by increasing the charging voltage (to a value with a small absolute value) by the correction value read from the correction value table TB1 (FIG. 6). However, the present invention is not limited to this. For example, when fading occurs on the printed paper P, the charging voltage may be corrected by decreasing the charging voltage (to a value with a large absolute value) by the correction value read from the correction value table TB1 (FIG. 6). The same applies to the second embodiment.

[0185] In the first embodiment described above, the charging voltage is corrected using a correction value read from the correction value table TB1 (FIG. 6). However, the present invention is not limited to this, and various other voltages may be corrected, such as the supply voltage supplied to the supply roller 42 and the developing voltage supplied to the developing roller 43. Furthermore, the voltage may be corrected not only at one location but also at two or more locations. Specifically, for example, it is conceivable to change the voltage difference between the developing voltage and the charging voltage to an appropriate value by increasing or decreasing the developing voltage while maintaining the value of the charging voltage. The same applies to the second embodiment.

[0186] Furthermore, in the first embodiment described above, the number of drum rotations DR while the internal temperature TN is above the degradation temperature TD is counted as the number of high-temperature drum rotations DH, and the length of time that the toner in the toner cartridge 31 has been exposed to high temperatures is measured based on this number of high-temperature drum rotations DH. However, the present invention is not limited to this. For example, the control unit 5 may be provided with a timing circuit capable of acquiring the current time, and the high-temperature time may be calculated and accumulated based on the start and end times of the period during which the internal temperature TN is above the degradation temperature TD, and a correction value may be determined based on this high-temperature time. The same applies to the second embodiment.

[0187] Furthermore, in the first embodiment described above, the correction value table TB1 (FIG. 6) is described as increasing the correction value as the historical high temperature TH increases when the high-temperature drum rotation speed DH is constant, and increasing the correction value as the high-temperature drum rotation speed DH increases when the historical high temperature TH is constant. However, the present invention is not limited to this. For example, the correction value may decrease as the high-temperature drum rotation speed DH increases when the high-temperature drum rotation speed DH is constant, or the correction value may decrease as the high-temperature drum rotation speed DH increases when the high-temperature drum rotation speed DH is constant. Alternatively, the correction value may be a discrete value that does not tend to increase or decrease monotonically with increases in the historical high temperature TH or the high-temperature drum rotation speed DH. Essentially, the correction value may be one that can appropriately suppress smearing on the printed paper P. The same applies to the second embodiment.

[0188] Furthermore, in the second embodiment described above, the values ​​of the correction values ​​in the correction value table TB2 (FIG. 11) are set to be larger than the values ​​of the correction values ​​in the correction value table TB1 (FIG. 6) when the historical high temperature TH and the high-temperature drum rotation speed DH are the same. However, the present invention is not limited to this, and for example, all or some of the correction values ​​in the correction value table TB2 may be set to be equal to or smaller than the values ​​of the correction values ​​in the correction value table TB1 when the historical high temperature TH and the high-temperature drum rotation speed DH are the same.

[0189] Furthermore, in the first embodiment described above, the degradation temperature TD, which is a condition for counting the high-temperature drum rotation number DH, is set to 20°C. However, the present invention is not limited to this, and the degradation temperature TD may be set to various other temperatures, such as 25°C, 30°C, or 45°C, depending on the characteristics of the toner in the toner cartridge 31. The same applies to the second embodiment.

[0190] Furthermore, in the first embodiment described above, only one type of correction value table TB1 (FIG. 6) is prepared, and the correction value table TB1 is shared by the image forming units 24 of each color. However, the present invention is not limited to this. For example, if the charging characteristics of each color of toner are different and the appropriate correction value is different even if the historical high temperature TH and the high-temperature drum rotation speed DH are the same, a correction value table for each color may be prepared, and the correction value for the corresponding color may be read from the correction value table. The same applies to the second embodiment.

[0191] Furthermore, in the second embodiment described above, two types of correction value tables (correction value table TB1 or TB2) are switched for reference depending on whether the toner remaining rate RE of the toner cartridge 31 is 50% or more. However, the present invention is not limited to this, and for example, four types of correction value tables may be prepared corresponding to four levels of the toner remaining rate RE of the toner cartridge 31: less than 25%; 25% or more but less than 50%; 50% or more but less than 75%; and 75% or more, and the correction value may be read out by switching to the correction value table corresponding to the toner remaining rate RE.

[0192] Furthermore, in the first embodiment described above, the correction value based on the historical high temperature TH and the high-temperature drum rotation speed DH is stored in advance in the correction value table TB1 (FIG. 6), and the correction value is read and used based on the values ​​of the historical high temperature TH and the high-temperature drum rotation speed DH. However, the present invention is not limited to this, and for example, the correction value may be calculated based on the values ​​of the historical high temperature TH and the high-temperature drum rotation speed DH using a pre-prepared function. The same applies to the second embodiment.

[0193] Furthermore, in the first embodiment described above, the correction value table TB1 (FIG. 6) is described as dividing the historical high temperature TH into 5°C intervals and dividing the high-temperature drum rotation speed DH into 250 rotations intervals. However, the present invention is not limited to this, and the historical high temperature TH may be divided into other temperature intervals, and the high-temperature drum rotation speed DH may be divided into other rotation speed intervals. Furthermore, these temperatures and rotation speeds do not necessarily have to be divided into equal intervals. The same applies to the second embodiment.

[0194] Furthermore, in the first embodiment described above, if the internal temperature TN drops below 20°C after a print job is executed by correcting the charging voltage based on the historical high temperature TH and the high-temperature drum rotation speed DH, the charging voltage is returned to its normal value. However, the present invention is not limited to this, and the charging voltage may remain at the corrected value after the print job is executed. In this case, when the next print job is executed, the charging voltage can be set to an appropriate value based on the historical high temperature TH and the high-temperature drum rotation speed DH at that time. The same applies to the second embodiment.

[0195] Furthermore, in the first embodiment described above, the image forming apparatus 1 is provided with three image forming units 24. However, the present invention is not limited to this, and two or less or four or more image forming units 24 may be provided. The same applies to the second embodiment.

[0196] Furthermore, in the first embodiment described above, an image is formed (printed) by the main body 2 on paper P cut from roll paper RP held by the paper feeder 3 (FIG. 1). However, the present invention is not limited to this, and it is also possible to provide a paper cassette or paper feed mechanism for feeding cut paper of, for example, A4 size, and form an image on the cut paper. The same applies to the second embodiment.

[0197] Furthermore, in the first embodiment described above, the image forming apparatus 1 is configured as a single-function printer. However, the present invention is not limited to this, and the image forming apparatus 1 may be configured as, for example, an MFP (Multi Function Peripheral) having the functions of a copier or facsimile machine. The same applies to the second embodiment.

[0198] Furthermore, the present invention is not limited to the above-described embodiments and other embodiments, and the scope of application of the present invention extends to embodiments in which the above-described embodiments and other embodiments are combined in part or in whole, or in which only a part of the above-described embodiments is extracted.

[0199] Furthermore, in the first embodiment described above, the image forming apparatus 1 is configured as an image forming apparatus including the photosensitive drum 45 as an image carrier, the charging roller 46 as a charging member, the developing roller 43 as a developer carrier, the supply roller 42 as a developer supply member, the temperature and humidity sensor 58 as a sensor, the temperature drive amount acquisition unit 52 as a temperature drive amount acquisition unit, and the control unit 5. However, the present invention is not limited to this, and the image forming apparatus may be configured as an image carrier, a charging member, a developer carrier, a developer supply member, a sensor, a temperature drive amount acquisition unit, and a control unit having various other configurations. [Industrial Applicability]

[0200] The present invention can be used in, for example, electrophotographic printers. [Explanation of symbols]

[0201] 1, 201...image forming apparatus, 5, 205...controller, 24...image forming unit, 28...transfer roller, 31...toner cartridge, 32...ID unit, 42...supply roller, 43...developing roller, 44...developing blade, 45...photosensitive drum, 46...charging roller, 51...printing control unit, 52...temperature drive amount acquisition unit, 54, 254...memory, 58...temperature and humidity sensor, 61...developing voltage control unit, 62...supply voltage control unit, 63...layer formation voltage control unit, 64...charging voltage control unit, 65...transfer voltage control unit, 205...controller, CD...dot count, DR...drum rotation speed, DH...high temperature drum rotation speed, P...paper, RE...toner remaining rate, TB1, TB2...correction value table, TD...deterioration temperature, TH...history high temperature, TN...internal temperature.

Claims

1. an image carrier that carries a latent image; a charging member to which a charging voltage is applied, which uniformly charges the image carrier; a developer carrier to which a development voltage is applied, and which supplies and carries a developer on the image carrier; a developer supply body to which a supply voltage is applied and which supplies the developer to the developer carrier; a sensor for detecting a temperature; a temperature driving amount acquisition unit that acquires a temperature driving amount that indicates an amount by which the image carrier is driven when the temperature detected by the sensor satisfies a predetermined temperature condition; a control unit that controls the charging voltage, the supply voltage, and the developing voltage; Equipped with The control unit performs control to correct at least one of the charging voltage, the supply voltage, and the developing voltage in accordance with the temperature detected by the sensor and the temperature driving amount acquired by the temperature driving amount acquisition unit. An image forming apparatus characterized by:

2. The control unit When the temperature detected by the sensor is high, the amount of correction for at least one of the charging voltage, the supply voltage, and the developing voltage is controlled to be larger than when the temperature is low.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

3. The control unit controls the voltage difference between the charging voltage and the developing voltage to be reduced when the temperature detected by the sensor is greater than a predetermined temperature threshold.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

4. The control unit controls the amount of correction when correcting at least one of the charging voltage, the supply voltage, and the developing voltage so that the amount of correction is larger when the temperature driving amount acquired by the temperature driving amount acquisition unit is large than when the temperature driving amount acquired by the temperature driving amount acquisition unit is small.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

5. When the temperature driving amount acquired by the temperature driving amount acquisition unit is greater than a predetermined temperature driving amount threshold, the control unit controls the voltage difference between the charging voltage and the developing voltage to be reduced.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

6. a developer storage section that stores the developer; a developer remaining rate acquisition unit that acquires a developer remaining rate, which is the rate of the developer remaining in the developer accommodating unit; Further comprising: The control unit controls the correction so as to be higher when the developer remaining rate is low than when the developer remaining rate is high.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

7. The temperature condition is that the temperature detected by the sensor is greater than a predetermined temperature threshold.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

8. The temperature driving amount is a value expressed by the number of rotations of the image carrier when the temperature detected by the sensor satisfies the temperature condition.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

9. a temperature detection step of detecting a temperature by a sensor; a temperature driving amount acquisition step of acquiring a temperature driving amount representing an amount by which an image carrier carrying a latent image is driven when the temperature detected by the sensor satisfies a predetermined temperature condition; a control step in which a control unit controls a charging voltage applied to a charging member that uniformly charges the image carrier, a developing voltage applied to a developer carrier that supplies and carries developer on the image carrier, and a supply voltage applied to a developer supply member that supplies the developer to the developer carrier; and In the control step, control is performed so as to correct at least one of the charging voltage, the supply voltage, and the developing voltage in accordance with the temperature detected in the temperature detection step and the temperature driving amount acquired in the temperature driving amount acquisition step. An image forming method comprising:

Images