Image forming apparatus

Abstract

To maintain image quality.SOLUTION: An image forming apparatus 1 is provided with: an image forming unit 10 that forms a toner image; a detection section 74 that detects the amount of toner in the image forming unit 10; a measuring section 75 that measures at least either of the humidity or the temperature around the image forming unit 10; and a determination section 76 that determines whether the amount of toner is equal to or less than a predetermined value. When the determination section 76 determines that the remaining amount of toner in the image forming unit 10 is equal to or less than the predetermined value, the amount of toner when at least either of the humidity or the temperature measured by the measuring section 75 is equal to or less than a predetermined humidity or a predetermined temperature is larger than the amount of toner when at least either of the humidity or the temperature measured by the measuring section 75 is higher than the predetermined humidity or the predetermined temperature.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus, and is suitably applicable to image forming apparatuses such as electrophotographic printers and copying machines. [Background technology]

[0002] Conventionally, a widely used image forming apparatus (also called a printer) performs printing processing by supplying a developer (also called a toner) from a toner cartridge to a developing device based on an image supplied from a computer device or the like, forming a developer image (also called a toner image) by the developing device, transferring it to a medium such as paper, and fixing it by applying heat and pressure.

[0003] Among such image forming apparatuses, there are some that detect when the remaining amount of developer in the developing device is low and notify the user of this (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-31521 A Summary of the Invention [Problem to be solved by the invention]

[0005] In such an image forming apparatus, as the developer deteriorates, image quality may decrease when there is a large difference in characteristics between the residual developer, which is the developer remaining in the developing device, and the newly supplied developer, which is the developer newly supplied from a new toner cartridge (also called a developer cartridge) after replacement. Therefore, there has been a demand for a system that can determine when the remaining amount of developer in the developing device is low at an appropriate time and replace the developer cartridge at an appropriate time.

[0006] The present invention has been made in consideration of the above points, and aims to propose an image forming apparatus capable of maintaining image quality. [Means for solving the problem]

[0007] In order to solve this problem, the image forming apparatus of the present invention includes an image forming unit that forms a developer image, a detection unit that detects the amount of developer in the image forming unit, a measurement unit that measures at least one of the humidity or temperature surrounding the image forming unit, and a judgment unit that judges whether the amount of developer is below a predetermined value, and when the judgment unit judges that the amount of developer in the image forming unit is below the predetermined value, the amount of developer when at least one of the humidity or temperature measured by the measurement unit is below the predetermined humidity or predetermined temperature is greater than the amount of developer when at least one of the humidity or temperature measured by the measurement unit is higher than the predetermined humidity or predetermined temperature.

[0008] The present invention can encourage replacement of the developer cartridge at a time when the remaining developer is little deteriorated, and can suppress the difference in characteristics between the remaining developer and newly supplied developer when the developer cartridge is replaced appropriately. Effect of the Invention

[0009] According to the present invention, it is possible to prompt replacement of the developer cartridge at a time when the remaining developer is little deteriorated, and when the developer cartridge is replaced appropriately, the difference in characteristics between the remaining developer and newly supplied developer can be suppressed, thereby realizing an image forming device that can maintain image quality. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a left side view showing the internal configuration of the image forming apparatus. [Diagram 2] FIG. 2 is a left side view showing the internal configuration of the image forming unit. [Diagram 3] FIG. 2 is a block diagram showing a control configuration of the image forming apparatus. [Figure 4] 4 is a flowchart showing a printing process procedure according to the first embodiment. [Diagram 5] 4 is a table showing a toner empty determination dot count value table according to the first embodiment. [Figure 6] FIG. 2 is a block diagram showing a functional configuration of the image forming apparatus. [Figure 7] FIG. 13 is a diagram showing a printed image for evaluation. [Figure 8] 1 is a table showing evaluation results according to the first embodiment. [Figure 9] 6 is a graph showing an increase in the potential and the amount of toner adhesion on the developing roller immediately after newly supplied toner is supplied when a toner empty state occurs according to the first embodiment. [Figure 10] 13 is a flowchart showing a print processing procedure (1) according to a second embodiment. [Figure 11] 13 is a flowchart showing a print processing procedure (2) according to the second embodiment. [Figure 12] 13 is a table showing a dot count value table for determining toner empty when the usage rate is 80% according to the second embodiment. [Figure 13] 13 is a table showing a dot count value table for determining toner empty when the usage rate is 90% according to the second embodiment. [Figure 14] 13 is a table showing evaluation results according to the second embodiment. [Figure 15] 13 is a graph showing an increase in the potential and the amount of toner adhesion on the developing roller immediately after newly supplied toner is supplied when a toner empty state occurs according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

[0012] 1. First embodiment [1-1. Configuration of image forming device] As shown in Fig. 1, the image forming apparatus 1 according to this embodiment is an electrophotographic printer that forms (i.e. prints) a color image on paper P as a medium. The image forming apparatus 1 has various parts arranged inside a housing 2 formed in a substantially box shape. Incidentally, in the following description, the right end portion in Fig. 1 is regarded as the front of the image forming apparatus 1, and the up-down direction, left-right direction, and front-rear direction are defined when viewed from the front. The image forming apparatus 1 is of a so-called direct transfer type, that is, it is configured to directly transfer a toner image as a developer image from a photoconductor drum 37 (described later) of an image forming unit 10 (described later) to paper P.

[0013] The image forming apparatus 1 is controlled by the control unit 15. The control unit 15 executes various processes by reading and executing a predetermined program from a memory 55 (FIG. 3). The control unit 15 is also connected to a higher-level device 16 (FIG. 3) such as a computer device by wire or wirelessly, and when image data representing an image to be printed is provided from the higher-level device 16 and an instruction is given to print the image data, the control unit 15 executes a print process to form a print image on the surface of the paper P.

[0014] A paper cassette 4 is provided at the bottom of the housing 2. The paper cassette 4 stores paper sheets P, such as paper, in a stacked state with the print surface, which is the surface to be printed, facing downward.

[0015] A hopping roller 5 is disposed above and in front of the paper cassette 4. The hopping roller 5 receives power from a drive source (not shown) via gears or the like and rotates to separate the paper P one by one and send it out to the conveying path W. Pinch rollers 6 and 7, a conveying roller 8, and a registration roller 9 are disposed downstream of the hopping roller 5 in the conveying direction of the paper P. The conveying roller 8 conveys the paper P by pinching the paper P between itself and the pinch roller 6 and receiving power from a drive source (not shown) via gears or the like and rotating. The registration roller 9 conveys the paper P toward the image forming unit 10K while correcting skew of the paper P by pinching the paper P between itself and the pinch roller 7 and receiving power from a drive source (not shown) via gears or the like and rotating.

[0016] Behind the pinch roller 7 and the registration roller 9, four image forming units 10K, 10C, 10M, and 10Y are arranged in this order from front to rear above the conveying path W. The image forming units 10K, 10C, 10M, and 10Y correspond to the colors black (K), cyan (C), magenta (M), and yellow (Y), respectively, but are all configured in the same way, with only the colors being different. Hereinafter, the image forming units 10K, 10C, 10M, and 10Y are collectively referred to as image forming units 10.

[0017] As shown in Fig. 2, the image forming unit 10 is made up of a developing device 11, a toner cartridge 12, and a print head 13. A plurality of rollers, such as a developing roller 35, a photosensitive drum 37, and the like, are incorporated inside the developing device 11. Each roller and the photosensitive drum 37 are formed in a cylindrical shape with a central axis aligned in the left-right direction, and are rotatably supported by the developing device 11. The photosensitive drum 37 has a portion near its lower end in contact with the transport path W. Some of the rollers are made of a conductive material, and a predetermined high voltage is applied to them (details will be described later).

[0018] The toner cartridge 12 contains toner and is attached to the upper side of the developing device 11. The toner cartridge 12 supplies the contained toner to the developing device 11. The toner is a negatively charged toner, and is composed of, for example, polyester resin, a colorant, a charge control agent, and a release agent, and an external additive (hydrophobic silica) is added. A developer having an average particle size of 7 μm in a pulverized form obtained by a pulverization method is used. Hereinafter, the toner remaining in the developing device 11 when the toner cartridge 12 is replaced with a new one is also referred to as residual toner, and the toner supplied from the new toner cartridge 12 to the developing device 11 is also referred to as newly supplied toner.

[0019] Also provided within the housing 2 (FIG. 1) are print heads 13K, 13C, 13M, and 13Y (hereinafter collectively referred to as print head 13) so as to correspond to the image forming units 10K, 10C, 10M, and 10Y, respectively. The print head 13 has a plurality of light emitting elements, such as LEDs (Light Emitting Diodes), arranged in the left-right direction, and emits light appropriately based on bitmap data supplied from the control unit 15.

[0020] When performing printing, the image forming unit 10 rotates the rollers of the developing device 11, the photosensitive drum 37, etc. as appropriate, and causes the print head 13 to emit light as appropriate while applying a predetermined high voltage to the rollers, etc. In this way, the image forming unit 10 forms a toner image on the circumferential side surface of the photosensitive drum 37 using toner supplied from the toner cartridge 12. At this time, the photosensitive drum 37 rotates to move the formed toner image to the vicinity of the lower end, i.e., the vicinity of the transport path W.

[0021] Meanwhile, a transfer transport section 20 is disposed below the transport path W, i.e., below the four image forming units 10. The transfer transport section 20 is composed of a front transport roller 21, a rear transport roller 22, a transfer belt 23, and four transfer rollers 24 (24K, 24C, 24M, and 24Y). Hereinafter, the transfer rollers 24K, 24C, 24M, and 24Y are collectively referred to as transfer rollers 24.

[0022] The front transport roller 21 and the rear transport roller 22 are cylindrical with their central axes aligned in the left-right direction, and are disposed in positions where the vicinity of their upper ends is extremely close to the transport path W. The transfer belt 23 is an endless belt made of a flexible material, and is stretched so as to go around the front transport roller 21 and the rear transport roller 22. Therefore, the upper portion of the transfer belt 23 stretched between the front transport roller 21 and the rear transport roller 22 runs along the transport path W, and is in contact with the vicinity of the lower ends of the photosensitive drums 37 in each image forming unit 10.

[0023] The transfer rollers 24 (24K, 24C, 24M, and 24Y) are disposed between the front conveying roller 21 and the rear conveying roller 22, at positions directly below the image forming units 10 (10K, 10C, 10M, and 10Y). Each transfer roller 24 is biased upward, and the vicinity of its upper end is in contact with the transfer belt 23. In other words, each transfer roller 24 holds the transfer belt 23 between itself and the photoconductor drum 37 of each image forming unit 10 on the conveying path W. A transfer voltage is applied to the transfer roller 24 to create a potential difference between the surface potential of the photoconductor drum 37 and the surface potential of the transfer roller 24 when a toner image formed by the toner attached on the photoconductor drum 37 is transferred to the paper P.

[0024] The transfer conveyance section 20 receives power from a drive source (not shown) via gears and the like to rotate the front conveyance roller 21, the rear conveyance roller 22, and each transfer roller 24 appropriately, thereby causing the transfer belt 23 to rotate around the front conveyance roller 21 and the rear conveyance roller 22 and run in the rear direction (hereinafter also referred to as the conveyance direction) on the conveyance path W. At this time, if a sheet P is supplied by the front pinch roller 7 and the registration roller 9, the transfer conveyance section 20 pinches it together with the transfer belt 23 between the photosensitive drum 37 of each image forming unit 10 and each transfer roller 24, and conveys it in the rear direction along the conveyance path W. Furthermore, if the image forming unit 10 has formed a toner image, the image forming unit 10 transfers the toner image from the outer circumferential surface of the photosensitive drum 37 to the upper surface of the sheet P (i.e., the printing surface).

[0025] In the image forming apparatus 1, a sheet P is advanced backward along a transport path W, and toner images of each color (i.e., a black toner image, a cyan toner image, a magenta toner image, and a yellow toner image) are sequentially transferred from image forming units 10K, 10C, 10M, and 10Y onto the sheet P. Hereinafter, the black toner image, the cyan toner image, the magenta toner image, and the yellow toner image are collectively referred to as color toner images.

[0026] A fixing device 25 is disposed behind the image forming unit 10 and the transfer transport section 20. The fixing device 25 heats the heat roller 31 and the fixing belt 32, which are disposed so as to face each other across the transport path W, under the control of the control section 15, and rotates the heat roller 31 and the fixing belt 32 in a predetermined direction, respectively, by transmitting power from a drive source (not shown) via gears or the like. In this way, the fixing device 25 applies heat and pressure to the paper P received from the transfer transport section 20, i.e., the paper P onto which the toner images of each color have been transferred in layers, to fix the toner, and then passes the paper P to the rear.

[0027] Pinch rollers 26 and 27 and discharge rollers 28 and 29 are disposed behind and above the fixing unit 25. The discharge roller 28 conveys the paper P delivered from the fixing unit 25 upward and rearward by pinching the paper P between itself and the pinch roller 26 and rotating with power transmitted from a driving source (not shown) via gears or the like. The discharge roller 29 pinches the paper P between itself and the pinch roller 27 and rotating with power transmitted from a driving source (not shown) via gears or the like, thereby discharging the paper P to a stacker unit 30 provided on the upper side of the housing 2.

[0028] In this manner, in the image forming apparatus 1, a toner image is formed using toner in the image forming unit 10, the toner image is transferred to the paper P transported by the transfer belt 23 in the transfer transport section 20, and then the toner image is fixed in the fixing device 25, thereby printing an image on the paper P (i.e., forming an image).

[0029] Further, a temperature and humidity sensor 14 is disposed within the housing 2. The temperature and humidity sensor 14 measures the temperature and humidity within the housing 2, and sends the measurement results to the control unit 15. Further, a density sensor 17 is disposed within the housing 2. The density sensor 17 detects a pattern for density measurement created on the transfer belt 23, and sends the detection results to the control unit 15. Based on the detection results obtained from the density sensor 17, the control unit 15 performs image quality maintenance operations such as density correction.

[0030] [1-2. Configuration of image forming unit] Next, a description will be given of the configuration of the image forming unit 10. As described above, the image forming unit 10 (FIG. 2) is made up of the developing device 11, the toner cartridge 12, and the print head 13. The developing device 11 has a toner storage space 39 for storing toner provided inside the housing, and below this, a charging roller 33, a supply roller 34, a developing roller 35, a developing blade 36, a photoconductor drum 37, and a cleaning blade 38 are arranged.

[0031] When the toner cartridge 12 is mounted above the developing device 11, the toner storage space 39 stores therein unused toner (newly supplied toner) supplied from the toner cartridge 12. A toner sensor 40 is provided in the toner storage space 39. The toner sensor 40 obtains a detection result according to the position of the top surface of the toner stored in the toner storage space 39, and sends this detection result to the control unit 15 (FIG. 1). Based on the detection result obtained from the toner sensor 40, the control unit 15 determines whether a toner-low state has occurred, in which the amount of toner stored in the toner storage space 39 has become equal to or less than a predetermined low value, which is a predetermined amount.

[0032] The charging roller 33 rotates in the direction indicated by the arrow, and charges the photosensitive drum 37 by applying a charging voltage, which is a negative high voltage. The supply roller 34 rotates in the direction indicated by the arrow, and applies a supply voltage, which is a negative high voltage, to the developing roller 35, thereby supplying toner. The developing blade 36 forms a thin layer of the toner supplied onto the developing roller 35. The developing roller 35 is disposed opposite the photosensitive drum 37, rotates in the direction indicated by the arrow, and applies a developing voltage, which is a negative high voltage, to the developing roller 35, thereby developing the toner carried by the developing roller 35 onto the electrostatic latent image formed on the surface of the photosensitive drum 37. The photosensitive drum 37 is a member that carries the electrostatic latent image on its surface (surface layer portion), and transfers the toner image developed on the surface of the photosensitive drum 37 to the paper P by rotating in the direction indicated by the arrow. The cleaning blade 38 scrapes off and collects the transfer residual toner on the photosensitive drum 37.

[0033] In this configuration, when a print command is issued from control unit 15 (FIG. 1), photoconductor drum 37, developing roller 35, supply roller 34, charging roller 33, and transfer roller 24 each rotate. At the same time, heat roller 31 (FIG. 1) rotates, and fixing belt 32 rotates in conjunction with the rotation of heat roller 31. The rotational directions of each roller and drum are as shown by the arrows in FIG. 2.

[0034] The surface layer of the photoconductor drum 37 is uniformly charged by the charging voltage applied to the charging roller 33 and its rotation. When the charged portion of the photoconductor drum 37 reaches below the print head 13, the print head 13 emits light in accordance with the image to be printed sent from the control unit 15, and forms an electrostatic latent image on the photoconductor drum 37. When the portion of the photoconductor drum 37 on which the electrostatic latent image has been formed reaches the developing roller 35, the toner on the developing roller 35, which has been thinned by the developing blade 36, moves to the photoconductor drum 37 due to the potential difference between the electrostatic latent image on the photoconductor drum 37 and the developing roller 35.

[0035] The toner transferred onto the paper P is fixed onto the paper P by the heat from the heated heat roller 31 and the pressure between the heat roller 31 and the fixing belt 32. Meanwhile, a portion of the toner that has not been transferred and remains on the photoconductor drum 37 is scraped off by a cleaning blade 38, and after printing is completed, it is collected in a waste toner box via a waste toner tube (not shown).

[0036] [1-3. Control configuration of image forming apparatus] As shown in FIG. 3, the image forming apparatus 1 has a control unit 15, an interface control unit 53, an operation display unit 54, a memory 55, various sensors 63, a process control unit 64, a development voltage control unit 65, a supply voltage control unit 66, a layer formation voltage control unit 67, a charging voltage control unit 68, an exposure control unit 69, a motor control unit 70, and a transfer voltage control unit 71.

[0037] The control unit 15 is mainly composed of a CPU (Central Processing Unit) which is a microprocessor, and controls each unit connected to an input / output port by reading and executing a predetermined program from a memory 55, and receives print data and control commands from a higher-level device 16 to control the entire image forming device 1 and perform a printing operation. The control unit 15 has a print control unit 50 and a toner usage control unit 51. The print control unit 50 controls the printing operation of the image forming device 1 based on the print data and control commands received via an interface control unit 53. The toner usage control unit 51 determines an available dot count which indicates the amount of toner that can be used from the occurrence of a toner low state until it is determined that the toner is empty (i.e., the dot count Dot).

[0038] The interface control unit 53 transmits information about the image forming apparatus 1 to the higher-level device 16, and receives print jobs including print data and control commands from the higher-level device 16. The operation display unit 54 is an operation panel or the like configured with an input unit such as operation buttons that accept input operations by an operator, and a display unit such as a display.

[0039] The memory 55 is a storage unit consisting of a ROM (Read Only Memory) 56 and a RAM (Random Access Memory) 57. This memory 55 stores a toner empty determination dot count value table TB1 shown in FIG. 5. The memory 55 also stores a drum count Dr of the developing device 11. The drum count Dr is a measurement value of the number of rotations (printing distance) of the photosensitive drum 37, and is a value that indicates the number of times the photosensitive drum 37 has been used. The memory 55 also stores a dot count Dot. The dot count Dot is the amount of toner converted into a value in dot units, which are the units of exposure by the print head 13.

[0040] The ROM 56 stores control programs (software) and control data for controlling and processing the overall operation of the image forming apparatus 1. The ROM 56 also has an internal temperature recording section 58A, an internal humidity recording section 59A, a transfer belt temperature recording section 60A, and a date and time recording section 61A. The internal temperature recording section 58A stores an internal temperature T indicating the temperature inside the image forming apparatus 1 acquired by the control section 15 from the temperature and humidity sensor 14 (FIG. 1). The internal humidity recording section 59A stores an internal humidity H indicating the humidity inside the image forming apparatus 1 acquired by the control section 15 from the temperature and humidity sensor 14 (FIG. 1). Hereinafter, the internal temperature T and the internal humidity H are also collectively referred to as the internal temperature and humidity. The transfer belt temperature recording section 60A stores a transfer belt temperature indicating the temperature of the transfer belt 23 acquired by the control section 15 from a transfer belt thermometer (not shown) provided in the housing 2 for measuring the temperature of the surface of the transfer belt 23. The date and time recording section 61A stores the measurement date and time, which is the date and time when the above-mentioned internal temperature and humidity and transfer belt temperature were measured. Furthermore, the ROM 56 stores the internal temperature T, internal humidity H, transfer belt temperature, and measurement date and time of the internal temperature recording section 58B, internal humidity recording section 59B, transfer belt temperature recording section 60B, and date and time recording section 61B in the RAM 57, respectively, when the power supply of the image forming apparatus 1 is cut off, for example.

[0041] The RAM 57 is, for example, a rewritable flash ROM, and temporarily stores various information generated with the execution of the control program. The RAM 57 also has an internal device temperature recording section 58B, an internal device humidity recording section 59B, a transfer belt temperature recording section 60B, and a date and time recording section 61B. The internal device temperature recording section 58B, the internal device humidity recording section 59B, the transfer belt temperature recording section 60B, and the date and time recording section 61B temporarily store the above-mentioned internal device temperature T, internal device humidity H, transfer belt temperature, and measurement date and time, respectively.

[0042] The various sensors 63 include a temperature and humidity sensor 14, a toner sensor 40, and a plurality of sensors for detecting the paper P.

[0043] The process control unit 64 controls the voltage applied to each roller based on an instruction from the print control unit 50. The development voltage control unit 65 controls the development voltage, which is the voltage applied to the development roller 35 in the development device 11. The supply voltage control unit 66 controls the supply voltage, which is the voltage applied to the supply roller 34 in the development device 11. The layer formation voltage control unit 67 controls the voltage applied to the development blade 36 in the development device 11. The charging voltage control unit 68 controls the charging voltage, which is the voltage applied to the charging roller 33. The exposure control unit 69 controls the exposure of each LED of the print head 13 according to the print data. The motor control unit 70 controls the photosensitive drum motor (not shown) to rotate the photosensitive drum 37. The photosensitive drum 37 has gears meshed with the development roller 35 and the supply roller 34 (FIG. 1) at one end, and rotates the development roller 35 and the supply roller 34 by transmitting the rotational driving force. The transfer voltage control unit 71 controls the transfer voltage, which is the voltage applied to each transfer roller 24.

[0044] The interface control unit 53, operation display unit 54, memory 55, various sensors 63, and density sensor 17 described above are connected to the print control unit 50, and perform input and output of signals to and from the print control unit 50. In addition, the process control unit 64, development voltage control unit 65, supply voltage control unit 66, layer formation voltage control unit 67, charging voltage control unit 68, transfer voltage control unit 71, and motor control unit 70 are connected to the print control unit 50, and operate by receiving output signals from the print control unit 50.

[0045] [1-4. Printing control to prevent smudges] Next, a description will be given of the stain fogging countermeasure printing control by suppressing the difference in charging characteristics between the remaining toner and newly supplied toner after replacing the toner cartridge 12 according to the first embodiment. This stain fogging countermeasure printing control comprises an available dot count determination process and an image forming process. In the available dot count determination process, the control unit 15 determines the available dot count when a toner low state occurs. In the image forming process, the control unit 15 prints only the available dot count after the toner low state occurs.

[0046] Based on the detection result from the toner sensor 40, the control unit 15 detects the remaining amount of toner in the developing device 11, and judges whether or not a toner-low state occurs through the print control unit 50. If a toner-low state does not occur, the control unit 15 performs a printing operation through the print control unit 50. At this time, the print control unit 50 controls the motor control unit 70, the exposure control unit 69, the development voltage control unit 65, the supply voltage control unit 66, the layer formation voltage control unit 67, the charging voltage control unit 68, and the transfer voltage control unit 71. When the motor control unit 70 receives an instruction from the print control unit 50, it controls the photoconductor drum motor to rotate the photoconductor drum 37. When the exposure control unit 69 receives an instruction from the print control unit 50, it controls the light emission of the print head 13. When the development voltage control unit 65, the supply voltage control unit 66, the layer formation voltage control unit 67, the charging voltage control unit 68, and the transfer voltage control unit 71 receive an instruction from the print control unit 50, they control the voltages applied to the development roller 35, the supply roller 34, the development blade 36, the charging roller 33, and the transfer roller 24, respectively.

[0047] On the other hand, when a toner-low state occurs, the control unit 15 determines the available dot count by the toner usage control unit 51 based on the detection result from the temperature and humidity sensor 14 in the available dot count determination step.

[0048] At this time, the toner usage control unit 51 selects one of the 16 toner empty determination dot count values ​​Dot_e1 in the toner empty determination dot count value table TB1 shown in Fig. 5, and determines it as the toner empty determination dot count Dot_E (described later) indicating the available dot count. As shown in the toner empty determination dot count value table TB1, the toner empty determination dot count value Dot_e1 is set to the reference toner empty determination dot count value Dot_st (120000 dot counts), which is a reference value, when 30[°C]<temperature T inside the device, and when 20[°C]<temperature T inside the device≦30[°C] and 20[%]<humidity H inside the device. In addition, for the same humidity H inside the device, the higher the temperature T inside the device, the higher the toner empty determination dot count value Dot_e1 becomes until it reaches the reference toner empty determination dot count value Dot_st. Furthermore, for the same internal device temperature T, the higher the internal device humidity H, the higher the toner empty determination dot count value Dot_e1 becomes until it reaches the reference toner empty determination dot count value Dot_st.

[0049] Here, in the image forming apparatus 1, the lower the internal temperature T, the more likely the environment is to cause printing defects due to the charge difference between the remaining toner and newly supplied toner when replacing the toner cartridge 12. Also, in the image forming apparatus 1, the lower the internal humidity H, the more likely the environment is to cause printing defects due to the charge difference between the remaining toner and newly supplied toner when replacing the toner cartridge 12.

[0050] Next, the control unit 15 performs a printing operation using the print control unit 50 in the image formation process. At this time, the toner usage control unit 51 increases the dot count Dot by the amount required for the printing operation. The print control unit 50 executes the printing operation until the dot count used after the toner low state occurs, which is the dot count Dot from when the toner low state occurred, reaches the usable dot count. On the other hand, when the dot count used after the toner low state occurs reaches the usable dot count, the print control unit 50 stops the printing operation and prompts the user to replace the toner cartridge 12 with a new one.

[0051] [1-5. Printing process] Next, a specific procedure of the printing process by the image forming apparatus 1 will be described with reference to the flowchart shown in FIG. 4. The control unit 15 starts the printing process procedure RT1 and proceeds to step SP1. At the start of the printing process procedure RT1, the toner empty determination dot count Dot_E is preset to the reference toner empty determination dot count value Dot_st. In step SP1, the control unit 15 acquires the temperature and humidity inside the device (temperature T inside the device and humidity H inside the device), the drum count Dr, and the dot count Dot by the print control unit 50, and proceeds to step SP2. In step SP2, the control unit 15 receives a print job from the print control unit 50 via the interface control unit 53, and proceeds to step SP3.

[0052] In step SP3, the control unit 15 determines whether or not a toner-low state has occurred using the print control unit 50. If a positive result is obtained here, this indicates that the toner is currently low, and the control unit 15 then proceeds to step SP4. On the other hand, if a negative result is obtained in step SP3, this indicates that the toner is not currently low and normal printing operations will continue, and the control unit 15 then skips steps SP4 to SP10 and proceeds to step SP11, where the print control unit 50 executes the printing operations for the current print job.

[0053] In step SP4, the control unit 15 sets the dot count Dot acquired in step SP1 as the toner-low occurrence dot count Dot_L, which is the dot count Dot when a toner-low state occurs, using the toner usage control unit 51, and proceeds to step SP5. In step SP5, the control unit 15 selects and sets the toner empty determination dot count Dot_E, which is the dot count Dot that determines a toner empty state based on the internal device temperature T and internal device humidity H, from the toner empty determination dot count value Dot_e1 in the toner empty determination dot count value table TB1 shown in Figure 5, using the toner usage control unit 51, and proceeds to step SP6.

[0054] In step SP6, the control unit 15 calculates the dot count used after the toner-low occurrence by subtracting the dot count Dot_L when the toner-low occurred from the dot count Dot (i.e., the dot count Dot-the dot count Dot_L when the toner-low occurred) using the toner usage control unit 51, and then proceeds to step SP7.

[0055] In step SP7, the control unit 15 determines using the toner usage control unit 51 whether the value obtained by subtracting the dot count Dot_L when a toner low occurs from the dot count Dot (the dot count used after a toner low occurs) is greater than or equal to the toner empty determination dot count Dot_E (i.e., the toner empty determination dot count Dot_E≦dot count Dot−dot count Dot_L when a toner low occurs).

[0056] If a negative result is obtained here, this indicates that the current state is not determined to be a toner empty state, there is sufficient toner remaining in the developing device 11, there is no need to replace the toner cartridge 12, and normal printing operation will continue because there will be no fading that tends to occur when the remaining toner amount is low. In this case, the control unit 15 skips steps SP8 to SP10 and proceeds to step SP11, where the printing operation of the current print job is executed by the print control unit 50. In reality, the dot count Dot-dot count at toner low occurrence Dot_L is 0 until the printing operation of the print job is executed immediately after it is determined that a toner low state has occurred, so the control unit 15 obtains a negative result in step SP7 and proceeds to step SP11. In step SP11, the control unit 15 executes printing of the current print job by the print control unit 50, and proceeds to step SP12.

[0057] In step SP12, the control unit 15 determines, by the print control unit 50, whether the drum count Dr after printing is equal to or greater than the drum count life Dr_end, which is the drum count Dr that indicates the life of the photosensitive drum 37 (i.e., drum count life Dr_end≦drum count Dr). If a negative result is obtained here, this means that the photosensitive drum 37 (i.e., the developing device 11) has not yet reached the end of its life, and therefore the above-mentioned processing will continue, and the control unit 15 then returns to step SP1.

[0058] As printing continues, the dot count Dot increases, and when the dot count used after the toner-low occurrence reaches or exceeds the toner empty determination dot count Dot_E, the control unit 15 obtains a positive result in step SP7 and proceeds to step SP8. That is, when a positive result is obtained in step SP7, this indicates that the dot count Dot for determining a toner empty state has been reached (i.e., the dot count used after the toner-low occurrence has reached the usable dot count), so there is not enough toner remaining in the developing device 11 and it is necessary to replace the toner cartridge 12, and there is a risk of fading, which tends to occur when the remaining toner amount is low, occurring and reducing image quality, so that the toner cartridge 12 needs to be replaced, and in this case the control unit 15 proceeds to step SP8.

[0059] In step SP8, the control unit 15 stops printing through the print control unit 50, and proceeds to step SP9. In step SP9, because the toner is empty, the control unit 15 causes the print control unit 50 to display a toner cartridge replacement prompting message, which is a message encouraging the user to replace the toner cartridge 12, on the operation display unit 54, and proceeds to step SP10.

[0060] In step SP10, the control unit 15 waits with the toner cartridge replacement prompting message displayed on the operation display unit 54 until the toner cartridge 12 is replaced with a new one, and proceeds to step SP11 when the toner cartridge 12 is replaced with a new one. In step SP11, the control unit 15 executes printing of the current print job by the print control unit 50, and proceeds to step SP12.

[0061] If a negative result is obtained in step SP12, this means that the photoconductor drum 37 (i.e., the developing device 11) has not yet reached the end of its life, so the above-mentioned processing continues, and at this time the control unit 15 returns to step SP1. In this way, once the toner cartridge 12 has been replaced, printing is possible as long as the developing device 11 has not reached the end of its life, so the control unit 15 returns to a standby state for receiving the next print job.

[0062] On the other hand, if a positive result is obtained in step SP12, this indicates that the photoconductor drum 37 (i.e., the developing device 11) has reached the end of its life and printing will continue until the toner inside the toner cartridge 12 is used up, at which point the control unit 15 proceeds to step SP13. In step SP13, the control unit 15 returns the toner empty determination dot count Dot_E to the reference toner empty determination dot count value Dot_st (120,000 dot counts) by the toner usage control unit 51, continues printing until the toner inside the toner cartridge 12 runs out, and then proceeds to step SP14, ending the printing process procedure RT1.

[0063] In this way, even if the developing device 11 has reached the end of its life, the image forming device 1 allows printing and continues printing until the toner in the toner cartridge 12 is used up. Therefore, the image forming device 1 prevents printing from becoming impossible because the developing device 11 has reached the end of its life regardless of the state of toner remaining in the toner cartridge 12, and can maintain the benefits of the user. However, since the developing device 11 has reached the end of its life, the toner cartridge 12 will not be replaced thereafter. Therefore, the image forming device 1 returns the toner empty determination dot count Dot_E to the reference toner empty determination dot count value Dot_st, thereby returning the amount of toner available from the toner low state until the toner empty state is determined to be the default value (i.e., the reference value) so that printing can be performed up to the limit of the remaining toner amount without causing blurring.

[0064] [1-6. Functional configuration of image forming device] Next, a description will be given of the functional configuration of the image forming apparatus 1. The control unit 15 (FIG. 3) of the image forming apparatus 1 reads out and executes a print processing program stored in advance in the memory 55, thereby forming each functional block as shown in FIG.

[0065] The image forming unit 10 forms a toner image as a developer image. The detection unit 74 corresponds to the print control unit 50 and the toner sensor 40, and detects the amount of toner as the amount of developer of the image forming unit 10. The measurement unit 75 corresponds to the print control unit 50 and the temperature and humidity sensor 14, and measures at least one of the humidity and the temperature around the image forming unit 10. The determination unit 76 corresponds to the toner usage amount control unit 51, and determines whether the amount of toner has become equal to or less than a predetermined value and a toner empty state has occurred.

[0066] The low determination unit 77 corresponds to the print control unit 50 and the toner sensor 40, and determines whether the toner amount has become equal to or less than a predetermined low value and a toner low state has occurred. The developer usable amount setting unit 78 corresponds to the toner usage control unit 51, and sets the toner usable amount, which is the amount of toner that can be used from when the low determination unit 77 determines that the toner amount is equal to or less than the low predetermined value until the determination unit 76 determines that the toner amount is equal to or less than the predetermined value (i.e., from when the toner low state occurs until when the toner empty state occurs), to a smaller amount when at least one of the humidity or temperature measured by the measurement unit 75 is equal to or less than the predetermined humidity or temperature than when at least one of the humidity or temperature measured by the measurement unit 75 is higher than the predetermined temperature or humidity.

[0067] [1-7. Evaluation of printing control to prevent smudges] Next, an evaluation of the print control for preventing stain fogging will be described. Regarding the evaluation of the print control for preventing stain fogging, printing was performed using the image forming apparatus 1 (FIG. 1) configured as described above under the conditions of Comparative Example 1-1, Comparative Example 1-2, Comparative Example 1-3, Comparative Example 1-4, Example 1-1, Example 1-2, Example 1-3, Example 1-4, Example 1-5, Example 1-6, Example 1-7, Example 1-8, Example 1-9, and Example 1-10 shown below, and the printouts were sampled. The sampled printouts were evaluated for stains and fogging, and the respective evaluation results were comprehensively judged.

[0068] In this evaluation, the above-mentioned printing process procedure RT1 was performed in the image forming apparatus 1, and after the toner was consumed to create a toner empty state, the toner cartridge 12 was replaced with a new one. Immediately after that, printing was performed with a print image density of 50% and a blank sheet of paper, and the printout was visually checked for stains and checked for fog using color differences to determine whether or not there were any problems with the print quality due to differences in toner charge.

[0069] [1-7-1. How to collect printed matter] · Comparative Example 1-1: Maintain the internal temperature and humidity of the apparatus at 10 < T [°C] ≤ 20 and 20 < H [%] ≤ 50 from the toner low state. Keep the toner empty determination dot count value Dot_e1 as the reference toner empty determination dot count value Dot_st, generate a toner empty state, then replace the toner cartridge 12 with a new one, and collect the printed matter immediately after that. · Comparative Example 1-2: Maintain the internal temperature and humidity of the apparatus at 10 < T [°C] ≤ 20 and 50 < H [%] ≤ 80 from the toner low state. Keep the toner empty determination dot count value Dot_e1 as the reference toner empty determination dot count value Dot_st, generate a toner empty state, then replace the toner cartridge 12 with a new one, and collect the printed matter immediately after that. · Comparative Example 1-3: Maintain the internal temperature and humidity of the apparatus at 10 < T [°C] ≤ 20 and 80 < H [%] from the toner low state. Keep the toner empty determination dot count value Dot_e1 as the reference toner empty determination dot count value Dot_st, generate a toner empty state, then replace the toner cartridge 12 with a new one, and collect the printed matter immediately after that. · Comparative Example 1-4: Maintain the internal temperature and humidity of the apparatus at 20 < T [°C] ≤ 30 and H [%] ≤ 20 from the toner low state. Keep the toner empty determination dot count value Dot_e1 as the reference toner empty determination dot count value Dot_st, generate a toner empty state, then replace the toner cartridge 12 with a new one, and collect the printed matter immediately after that. · Example 1-1: Maintain the internal temperature and humidity of the apparatus at T [°C] ≤ 10 and H [%] ≤ 20 from the toner low state. Change the toner empty determination dot count value Dot_e1 from the reference toner empty determination dot count value Dot_st to 90000 as shown in the toner empty determination dot count value table TB1 (Figure 5) to generate a toner empty state, then replace the toner cartridge 12 with a new one, and collect the printed matter immediately after that. · Example 1-2: Maintain the internal temperature and humidity of the device at T[℃] ≤ 10 and 20 < H[%] ≤ 50 from the toner low state. Change the toner empty determination dot count value Dot_e1 from the reference toner empty determination dot count value Dot_st to 96000 as shown in the toner empty determination dot count value table TB1 (Figure 5) to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards. · Example 1-3: Maintain the internal temperature and humidity of the device at T[℃] ≤ 10 and 50 < H[%] ≤ 80 from the toner low state. Change the toner empty determination dot count value Dot_e1 from the reference toner empty determination dot count value Dot_st to 102000 as shown in the toner empty determination dot count value table TB1 (Figure 5) to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards. · Example 1-4: Maintain the internal temperature and humidity of the device at T[℃] ≤ 10 and 80 < H[%] from the toner low state. Change the toner empty determination dot count value Dot_e1 from the reference toner empty determination dot count value Dot_st to 108000 as shown in the toner empty determination dot count value table TB1 (Figure 5) to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards. · Example 1-5: Maintain the internal temperature and humidity of the device at 10 < T[℃] ≤ 20 and H[%] ≤ 20 from the toner low state. Change the toner empty determination dot count value Dot_e1 from the reference toner empty determination dot count value Dot_st to 96000 as shown in the toner empty determination dot count value table TB1 (Figure 5) to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards. · Example 1-6: Maintain the internal temperature and humidity of the device at 10 < T[℃] ≤ 20 and 20 < H[%] ≤ 50 from the toner low state. Change the toner empty determination dot count value Dot_e1 from the reference toner empty determination dot count value Dot_st to 102000 as shown in the toner empty determination dot count value table TB1 (Figure 5) to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards. · Example 1-7: Maintain the internal temperature and humidity of the device at 10 < T [°C] ≤ 20 and 50 < H [%] ≤ 80 from the toner low state. Change the toner empty determination dot count value Dot_e1 from the reference toner empty determination dot count value Dot_st to 108,000 as shown in the toner empty determination dot count value table TB1 (Figure 5) to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards. · Example 1-8: Maintain the internal temperature and humidity of the device at 10 < T [°C] ≤ 20 and 80 < H [%] from the toner low state. Change the toner empty determination dot count value Dot_e1 from the reference toner empty determination dot count value Dot_st to 114,000 as shown in the toner empty determination dot count value table TB1 (Figure 5) to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards. · Example 1-9: Maintain the internal temperature and humidity of the device at 20 < T [°C] ≤ 30 and H [%] ≤ 20 from the toner low state. Change the toner empty determination dot count value Dot_e1 from the reference toner empty determination dot count value Dot_st to 108,000 as shown in the toner empty determination dot count value table TB1 (Figure 5) to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards. · Example 1-10: Maintain the internal temperature and humidity of the device at 20 < T [°C] ≤ 30 and 20 < H [%] ≤ 20 from the toner low state. Keep the toner empty determination dot count value Dot_e1 as the reference toner empty determination dot count value Dot_st and generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards.

[0070] [1-7-2. Evaluation of dirt] In this evaluation, the stains on the paper surface were evaluated. In this evaluation, as shown in Fig. 7(A), a print pattern PT with a print image density of 50% was formed over the entire area of ​​a blank A4 paper P, and the resulting print was visually observed to determine whether stains 80 occurred. Here, the print image density is a value that represents the ratio of the number of pixels that transfer toner to the paper P out of the total number of pixels when an image is broken down into pixels.

[0071] Here, under low temperature and low humidity conditions, when the toner deteriorates, the charge of the toner on the developing roller 35 tends to increase, and the potential and amount of toner adhesion tend to increase. If newly supplied toner with a low charge is mixed with such residual toner, it becomes difficult to make the toner layer thickness on the developing roller 35 uniform, and even toner that is not originally developed is developed, which is thought to cause stains.

[0072] In this evaluation, if the stain was not visible to the naked eye on the printed matter and no stain had occurred, the stain was judged to be good and an "O" was entered in Figure 8; if the printed matter looked darker in some areas and the density was darker when the eye was squinting, the stain was judged to be within the acceptable range and a "△" was entered in Figure 8; and if the stain was visible to the naked eye and had occurred on the printed matter, the stain was judged to be poor and an "X" was entered in Figure 8.

[0073] [1-7-3. Evaluation of fogging] In this evaluation, fog within the paper surface was evaluated. In this evaluation, as shown in Fig. 7(B), a blank A4 paper P (Excellent Paper PPR-DA4TDB_55kg paper: manufactured by Oki Electric Industry Co., Ltd.) was not printed on the entire area, and one blank sheet of the paper P was printed in transverse feed, and the color values ​​of the blank part 82 where fog did not occur were measured as L1, a1, and b1, and the color values ​​of the fog-occurring part 84 where fog occurred were measured as L2, a2, and b2 using a spectrodensitometer (X-Rite 528: manufactured by X-Rite Co., Ltd.) with a D50 light source, an angle of 2[°], and status I. In this evaluation, the color difference ΔE between the printed paper P and the same unprinted paper P was calculated according to the following formula (1).

[0074]

number

[0075] Furthermore, in this evaluation, when the color difference ΔE≦0.50 and the fog was not noticeable to the naked eye, the color difference ΔE was judged to be good and an "O" was entered in Figure 8; when the color difference ΔE was 0.50<color difference ΔE≦1.00 and the fog was visible when one squinted but not bothersome, the color difference ΔE was judged to be within the acceptable range and an "△" was entered in Figure 8; and when the color difference ΔE<1.00 and the fog was noticeable to the naked eye, the color difference ΔE was judged to be poor and an "X" was entered in Figure 8.

[0076] [1-7-4. Overall Judgment] As shown in FIG. 8, if the evaluations of both dirt and color difference were "○", the overall judgment was marked "◎" as effective, if either the evaluation of dirt or color difference was "×", the overall judgment was marked "×" as ineffective, and if one of the evaluations of dirt and color difference was "△" and the other was "○", the overall judgment was marked "○" as effective based on visual observation.

[0077] [1-8. Effects, etc.] In the above configuration, the image forming device 1 changes the amount of toner available from when a toner-low state occurs until a toner-empty state is determined to be an appropriate value according to the internal temperature and humidity (internal temperature T and internal humidity H) that indicate the environment in which the image forming device 1 is placed. Specifically, when a toner-low state occurs in a low humidity environment, the image forming device 1 determines that a toner-empty state is occurring when there is more toner remaining in the developing device 11 than in a high humidity environment. Therefore, in the toner-empty state, the image forming unit 10 has more toner remaining in the developing device 11 in a low humidity environment than in a high humidity environment.

[0078] Furthermore, when the image forming device 1 is in a low temperature environment and the toner-low state occurs, the image forming device 1 determines that the toner-empty state has occurred when there is more toner remaining in the developing device 11 than when the image forming device 10 is in a high temperature environment. Therefore, when the image forming unit 10 is in a toner-empty state, the amount of toner remaining in the developing device 11 is more in a low temperature environment than when the image forming device 10 is in a high temperature environment.

[0079] Therefore, compared to a case where the amount of usable toner from when a toner-low state occurs until a toner-empty state is determined to be constant regardless of the temperature and humidity inside the device (temperature T inside the device and humidity H inside the device), the image forming device 1 can reduce the charge difference between the remaining toner remaining in the developing device 11 and the newly supplied toner supplied from the new toner cartridge 12 when the toner cartridge 12 is replaced in a toner-empty state. This allows the image forming device 1 to reduce the occurrence of smudges and fogging due to the charge difference between the remaining toner and the newly supplied toner, improving print quality.

[0080] In response to this, the image forming apparatus 1 may be able to suppress the occurrence of stains and fogging caused by the charge difference between the remaining toner and newly supplied toner by appropriately changing the developing voltage before and after replacing the toner cartridge 12 and controlling the toner layer on the developing roller 35 to a constant thickness. In this case, however, the image forming apparatus 1 needs to carry out a complex process of appropriately changing the developing voltage.

[0081] Also, the image forming apparatus 1 may perform idle control before printing after replacing the toner cartridge 12, by rotating the supply roller 34, developing roller 35, developing blade 36, and charging roller 33 to agitate the remaining toner in the developing device 11 and stabilize the charge, thereby suppressing the occurrence of stains and fogging caused by the charge difference between the remaining toner and newly supplied toner. However, in this case, the image forming apparatus 1 requires time to perform the idle control, which reduces the print first speed, and the rollers of the developing device 11 wear out and approach the end of their lives because the supply roller 34, developing roller 35, developing blade 36, and charging roller 33 are rotated for the idle control.

[0082] In response to this, the image forming apparatus 1 can eliminate the need for complex processing to appropriately change the development voltage, and by eliminating the need for idle control, the print first speed can be improved, the amount of wear on each roller of the developing device 11 can be reduced, and the lifespan can be extended, while the occurrence of smudges and fogging due to the charge difference between the remaining toner and newly supplied toner can be suppressed.

[0083] FIG. 9(A) shows the measurement results of the image forming apparatus of the comparative example, in which all the toner empty determination dot count values ​​Dot_e1 in the toner empty determination dot count value table TB1 (FIG. 5) are set as the reference toner empty determination dot count value Dot_st. The temperature T inside the apparatus during this measurement is 9 to 12°C, and the humidity H inside the apparatus is 10 to 14%. FIG. 9(A) also shows a state in which the drum count Dr is 50% of the drum count life Dr_end, that is, the usage rate of the developing device 11 relative to the developing device life is 50%. Hereinafter, the usage rate of the developing device 11 relative to the developing device life is also referred to as the developing device usage rate. The graph Gr150te on the left side of FIG. 9(A) shows the potential and toner adhesion amount on the developing roller 35 when the toner empty state occurs. 9A shows the potential on the developing roller 35 and the amount of toner adhesion immediately after the toner cartridge 12 is replaced with a new one after the toner empty state occurs and new toner is supplied from the toner cartridge 12 to the developing device 11. Compared with graph Gr150te, graph Gr150tc shows that the potential on the developing roller 35 has increased by about -10 [V] and the amount of toner adhesion on the developing roller 35 has increased by 0.2 [mg cm 2 ] has increased by some degree.

[0084] On the other hand, FIG. 9(B) shows the measurement results in the case of the image forming apparatus 1 of the present embodiment, in which the toner empty determination dot count value Dot_e1 in the toner empty determination dot count value table TB1 (FIG. 5) is appropriately changed to the reference toner empty determination dot count value Dot_st as shown in FIG. 5. FIG. 9(B) shows the state in which the development device usage rate is 50[%], as in FIG. 9(A). The graph Gr50te on the left side of FIG. 9(B) shows the potential and toner adhesion amount on the development roller 35 when the toner empty state occurs, as in the graph Gr150te. Also, the graph Gr50tc on the right side of FIG. 9(B) shows the potential and toner adhesion amount on the development roller 35 immediately after the toner cartridge 12 is replaced with a new one after the toner empty state occurs and newly supplied toner is supplied from the toner cartridge 12 to the development device 11, as in the graph Gr150tc. In comparison with graph Gr50te, graph Gr50tc shows that the potential on the developing roller 35 is increased by about -5 [V], and the amount of toner adhesion on the developing roller 35 is 0.1 [mg cm 2 ] has increased by some degree.

[0085] As shown in FIG. 9, compared to the comparative example, the image forming apparatus 1 according to the present embodiment is able to suppress an increase in the amount of toner adhesion and the potential on the developing roller 35 immediately after the toner cartridge 12 is replaced with a new one and newly supplied toner is supplied from the toner cartridge 12 to the developing device 11 after the toner empty state occurs.

[0086] In this way, the image forming apparatus 1 can maintain the charging characteristics of the remaining toner close to those of newly supplied toner by optimizing the amount of toner remaining in the developing device 11 according to the temperature and humidity environment of the image forming apparatus 1.

[0087] According to the above configuration, the image forming device 1 includes an image forming unit 10 that forms a toner image, a detection unit 74 that detects the amount of toner in the image forming unit 10, a measurement unit 75 that measures at least one of the humidity and temperature surrounding the image forming unit 10, and a judgment unit 76 that judges whether the amount of toner is below a predetermined value, and when the judgment unit 76 judges that the remaining amount of toner as a developer in the image forming unit 10 is below a predetermined value, the amount of toner when at least one of the humidity and temperature measured by the measurement unit 75 is below the predetermined humidity or the predetermined temperature is greater than the amount of toner when at least one of the humidity and temperature measured by the measurement unit 75 is higher than the predetermined humidity or the predetermined temperature.

[0088] This allows the image forming apparatus 1 to prompt replacement of the toner cartridge 12 at a time when the remaining toner is less degraded, and when the toner cartridge 12 is replaced appropriately, the difference in characteristics between the remaining toner and newly supplied toner can be reduced.

[0089] 2. Second embodiment [2-1. Configuration of image forming device] As shown in Figures 1 and 3, image forming apparatus 101 according to the second embodiment differs from image forming apparatus 1 according to the first embodiment in that it has control unit 115 instead of control unit 15, but is otherwise configured in the same manner.

[0090] [2-2. Control configuration of image forming device] As shown in FIG. 3, the control unit 115 of the second embodiment differs from the control unit 15 of the first embodiment in that it has a print control unit 150 instead of the print control unit 50, and a toner usage control unit 151 instead of the toner usage control unit 51, but is otherwise configured similarly.

[0091] [2-3. Printing control to prevent smudges] Next, a description will be given of a second embodiment of a printing control for preventing stain fogging by suppressing the difference in charging characteristics between the remaining toner and newly supplied toner after replacing the toner cartridge 12. This printing control for preventing stain fogging comprises an available dot count determination process and an image forming process. In the available dot count determination process, the control unit 115 determines the available dot count according to the development device usage rate when a toner low state occurs. In the image forming process, the control unit 115 prints only the available dot count after the toner low state occurs.

[0092] Based on the detection result from the toner sensor 40, the control unit 115 detects the remaining amount of toner in the developing device 11, and determines whether or not a toner-low state has occurred using the print control unit 150. If a toner-low state has not occurred, the control unit 115 performs a printing operation using the print control unit 150 in the same manner as in the first embodiment.

[0093] On the other hand, when a toner-low state occurs, in the usable dot count determination step, the control unit 115 determines the usable dot count by the toner usage control unit 151 based on the development device usage rate and the detection results from the temperature and humidity sensor 14.

[0094] At this time, if the development device usage rate is 80% or more, the toner usage control unit 151 selects one of the 16 toner empty determination dot count values ​​Dot_e2 in the toner empty determination dot count value table TB101 for an 80% usage rate shown in Figure 12, and determines it as the toner empty determination dot count Dot_E.

[0095] On the other hand, at this time, if the development device usage rate is 90% or more, the toner usage control unit 151 selects one of the 16 toner empty determination dot count values ​​Dot_e3 in the toner empty determination dot count value table TB102 for a usage rate of 90% shown in Figure 13, and determines it as the toner empty determination dot count Dot_E.

[0096] When comparing table TB102, which is the dot count value determining when toner is empty when the usage rate is 90%, with table TB101, which is the dot count value determining when toner is empty when the usage rate is 80%, when the conditions of temperature and humidity inside the device (temperature T inside the device and humidity H inside the device) are the same, at many temperatures and humidity inside the device, the dot count value Dot_e3 determining when toner is empty is smaller than the dot count value Dot_e2.

[0097] Here, in the image forming apparatus 101, similarly to the image forming apparatus 1, the lower the internal temperature T or internal humidity H of the apparatus, the more likely it is that printing defects will occur due to the charge difference between the remaining toner and newly supplied toner after replacing the toner cartridge 12. In addition, in the image forming apparatus 101, when the usage rate of the developing device increases and the developing device 11 approaches the end of its life, wear of each roller in the developing device 11 progresses, and the frequency of occurrence of stains and fogging is likely to increase.

[0098] Next, the control unit 115 performs a printing operation using the print control unit 150 in the image formation process. At this time, the toner usage control unit 151 increases the dot count Dot and the drum count Dr by the amount required for the printing operation. The print control unit 150 executes the printing operation until the used dot count after the toner low occurrence reaches the usable dot count. On the other hand, when the used dot count after the toner low occurrence reaches the usable dot count, the print control unit 150 stops the printing operation and prompts the user to replace the toner cartridge 12 with a new one.

[0099] [2-4. Printing process] 10 and 11, in which steps corresponding to those in the printing procedure RT1 (FIG. 4) are given the same reference numerals. In steps SP1 to SP4, the control unit 115 performs the same processes as those in the printing procedure RT1 (FIG. 4), and then proceeds to step SP101.

[0100] In step SP101, the control unit 115 determines whether the value obtained by dividing the drum count Dr by the drum count life Dr_end is equal to or greater than 90%, which is the drum count threshold Drth90 at a 90% usage rate as a first life determination value (i.e., drum count Dr / drum count life Dr_end≧drum count threshold Drth90 at a 90% usage rate) through the print control unit 150. If a negative result is obtained here, this indicates that the current development device usage rate is less than 90%, and the control unit 115 then proceeds to step SP105.

[0101] In step SP105, the control unit 115 determines using the print control unit 150 whether the value obtained by dividing the drum count Dr by the drum count life Dr_end is greater than or equal to 80%, which is the drum count threshold Drth80 at an 80% usage rate as the second life determination value (i.e., drum count Dr / drum count life Dr_end≧drum count threshold Drth80 at an 80% usage rate). If a negative result is obtained here, this indicates that the current development device usage rate is less than 80%, and the rollers in the development device 11 are not worn out, so printing problems due to the charge difference between the remaining toner due to replacement of the toner cartridge 12 and newly supplied toner are unlikely to occur, and therefore the toner empty determination dot count Dot_E will remain at the reference toner empty determination dot count value Dot_st.In this case, the control unit 115 skips steps SP106 to SP108 and steps SP8 to SP10 (Figure 11) and proceeds to step SP11 (Figure 11), and the printing operation of the current print job is executed by the print control unit 150.

[0102] On the other hand, when printing is repeated and the usage rate of the developing device reaches 80% or more, wear of the rollers in the developing device 11 progresses, and printing problems are likely to occur due to the charge difference between the remaining toner after replacing the toner cartridge 12 and newly supplied toner. Therefore, the control unit 115 obtains a positive result in step SP105 and proceeds to step SP106 (Figure 10).

[0103] In step SP106, the control unit 115 selects and sets the toner empty determination dot count Dot_E from the toner empty determination dot count value Dot_e2 in the toner empty determination dot count value table TB101 for a toner empty usage rate of 80% shown in Figure 12 based on the temperature T inside the device and the humidity H inside the device using the toner usage control unit 151, and then proceeds to step SP107.

[0104] In step SP107, control unit 115 calculates the dot count used after the toner low occurrence by subtracting the dot count Dot_L when the toner low occurred from the dot count Dot (i.e., dot count Dot - dot count Dot_L when the toner low occurred) using toner usage control unit 151, and then proceeds to step SP108.

[0105] In step SP108, the control unit 115 determines using the toner usage control unit 151 whether the value obtained by subtracting the dot count Dot_L when a toner low occurs from the dot count Dot (the dot count used after a toner low occurs) is greater than or equal to the toner empty determination dot count Dot_E (i.e., the toner empty determination dot count Dot_E≦dot count Dot−dot count Dot_L when a toner low occurs).

[0106] If a negative result is obtained here, this means that although the current usage rate of the developing device is 80% or more, the state is not judged to be a toner empty state, there is sufficient toner remaining in the developing device 11, so there is no need to replace the toner cartridge 12, and since there will be no smearing, which is likely to occur when the remaining toner is low, normal printing operation will continue.In this case, the control unit 115 skips steps SP8 to SP10 (Figure 11) and proceeds to step SP11, and the printing operation of the current print job is executed by the print control unit 150.

[0107] On the other hand, when printing is repeated and the development device usage rate is between 80% and 90%, and toner empty determination dot count Dot_E≦dot count Dot-toner low occurrence dot count Dot_L, printing problems are likely to occur due to the charge difference between the remaining toner after replacement of toner cartridge 12 and newly supplied toner, so the control unit 115 obtains a positive result in step SP108 (Figure 10), moves to step SP8 (Figure 11), and performs processing similar to that of printing processing procedure RT1 (Figure 4).

[0108] On the other hand, if printing is repeated after the developing device usage rate reaches 80% or more, and the developing device usage rate reaches 90% or more before the toner empty determination dot count Dot_E≦dot count Dot - dot count Dot_L when toner low occurs, the rollers in the developing device 11 will wear further than when the developing device usage rate was 80% or more, and printing problems due to the charge difference between the remaining toner after replacing the toner cartridge 12 and newly supplied toner will be more likely to occur, so the control unit 115 obtains a positive result in step SP101 (Figure 10) and proceeds to step SP102.

[0109] In step SP102, the control unit 115 selects and sets the toner empty determination dot count Dot_E from the toner empty determination dot count value Dot_e3 in the toner empty determination dot count value table TB102 at a usage rate of 90% shown in Figure 13 based on the temperature T inside the device and the humidity H inside the device using the toner usage control unit 151, and proceeds to step SP103.

[0110] In step SP103, control unit 115 calculates the dot count used after the toner low occurrence by subtracting the dot count Dot_L when the toner low occurred from the dot count Dot (i.e., dot count Dot - dot count Dot_L when the toner low occurred) using toner usage control unit 151, and then proceeds to step SP104.

[0111] In step SP104, the control unit 115 determines using the toner usage control unit 151 whether the value obtained by subtracting the dot count Dot_L when a toner low occurs from the dot count Dot (the dot count used after a toner low occurs) is greater than or equal to the toner empty determination dot count Dot_E (i.e., the toner empty determination dot count Dot_E≦dot count Dot−dot count Dot_L when a toner low occurs).

[0112] If a negative result is obtained here, this indicates that although the current usage rate of the developing device is 90% or more, the state is not judged to be a toner empty state, there is sufficient toner remaining in the developing device 11, there is no need to replace the toner cartridge 12, and there will be no smearing, which is likely to occur when the remaining toner is low, so normal printing operation will continue.In this case, the control unit 115 skips steps SP8 to SP10 (FIG. 11) and moves to step SP11 (FIG. 11), and the printing operation of the current print job is executed by the print control unit 150.

[0113] On the other hand, when printing is repeated after the development device usage rate reaches 90% or more, and toner empty determination dot count Dot_E≦dot count Dot-toner low occurrence dot count Dot_L, printing problems are likely to occur due to the charge difference between the remaining toner due to replacement of toner cartridge 12 and newly supplied toner, so the control unit 115 obtains a positive result in step SP104, moves to step SP8 (Figure 11), and performs processing similar to that of the printing processing procedure RT1 (Figure 4).

[0114] Meanwhile, in steps SP12 and SP13 (FIG. 11), the control unit 115 performs the same processes as in the printing procedure RT1 (FIG. 4), moves to step SP15, and ends the printing procedure RT101.

[0115] [2-5. Evaluation of printing control to prevent smudges] Next, the evaluation of the anti-smudging printing control will be described. Regarding the evaluation of this anti-smudging printing control, under the conditions of Comparative Example 2-1, Comparative Example 2-2, Comparative Example 2-3, Comparative Example 2-4, Comparative Example 2-5, Comparative Example 2-6, Comparative Example 2-7, Example 2-1, Example 2-2, Example 2-3, Example 2-4, Example 2-5, Example 2-6, Example 2-7, Example 2-8, Example 2-9, Example 2-10, Example 2-11, Example 2-12, Example 2-13, Example 2-14, Example 2-15, Example 2-16, Example 2-17, Example 2-18, Example 2-19, Example 2-20, Example 2-21, Example 2-22, Example 2-23, Example 2-24, Example 2-25, Example 2-26, Example 2-27, Example 2-28, Example 2-29, and Example 2-30 shown below, printing was performed by the image forming apparatus 101 (FIG. 1) having the above-described configuration, the printed matter was collected, and the collected printed matter was evaluated for smudging and fogging, respectively, and the respective evaluation results were comprehensively determined.

[0116] In this evaluation, in the image forming apparatus 101, the above-described printing processing procedure RT101 was carried out. Similar to the first embodiment, after consuming toner to generate a toner empty state, the toner cartridge 12 was replaced with a new one, and immediately thereafter, printing with a printing image density of 50 [%] and printing on white paper were carried out. The smudging on the printed matter was visually confirmed, and the fogging was confirmed by color difference, thereby determining whether there was a defect in the print quality due to the charging difference of the toner.

[0117] [2-5-1. Method of Collecting Printed Matter] · Comparative Example 2-1... Maintaining the internal temperature and humidity of the apparatus at 10 < T [°C] ≦ 20 and 50 < H [%] ≦ 80 in the toner low state, keeping the toner empty determination dot count values Dot_e2 and Dot_e3 as the reference toner empty determination dot count value Dot_st, generating a toner empty state, replacing the toner cartridge 12 with a new one, and collecting the printed matter immediately thereafter · Comparative Example 2-2: Maintain the internal temperature and humidity of the device at 10 < T [°C] ≤ 20 and 80 < H [%] from the toner low state, keep the toner empty determination dot count values Dot_e2 and Dot_e3 as the reference toner empty determination dot count value Dot_st, generate a toner empty state, then replace the toner cartridge 12 with a new one, and collect the printed matter immediately after that. · Comparative Example 2-3: Maintain the internal temperature and humidity of the device at 20 < T [°C] ≤ 30 and H [%] ≤ 20 from the toner low state, keep the toner empty determination dot count values Dot_e2 and Dot_e3 as the reference toner empty determination dot count value Dot_st, generate a toner empty state, then replace the toner cartridge 12 with a new one, and collect the printed matter immediately after that. · Comparative Example 2-4: Maintain the internal temperature and humidity of the device at 20 < T [°C] ≤ 30 and 20 < H [%] ≤ 50 from the toner low state, keep the toner empty determination dot count values Dot_e2 and Dot_e3 as the reference toner empty determination dot count value Dot_st, generate a toner empty state, then replace the toner cartridge 12 with a new one, and collect the printed matter immediately after that. · Comparative Example 2-5: Maintain the internal temperature and humidity of the device at 20 < T [°C] ≤ 30 and 80 < H [%] from the toner low state, keep the toner empty determination dot count values Dot_e2 and Dot_e3 as the reference toner empty determination dot count value Dot_st, generate a toner empty state, then replace the toner cartridge 12 with a new one, and collect the printed matter immediately after that. · Comparative Example 2-6: Maintain the internal temperature and humidity of the device at 30 < T [°C] and H [%] ≤ 20 from the toner low state, keep the toner empty determination dot count values Dot_e2 and Dot_e3 as the reference toner empty determination dot count value Dot_st, generate a toner empty state, then replace the toner cartridge 12 with a new one, and collect the printed matter immediately after that. · Comparative Example 2-7: Maintain the internal temperature and humidity of the apparatus at 30 < T [°C] and 50 < H [%] ≤ 80 from the toner low state, keep the toner empty determination dot count values Dot_e2 and Dot_e3 as the reference toner empty determination dot count value Dot_st, generate a toner empty state, then replace the toner cartridge 12 with a new one, and collect the printed matter immediately after that. · Example 2-1: Maintain the internal temperature and humidity of the apparatus at T [°C] ≤ 10 and H [%] ≤ 20 from the toner low state when the developing device usage rate is 90 [%] or more. Change the toner empty determination dot count value Dot_e3 from the reference toner empty determination dot count value Dot_st to 78000 as shown in the toner empty determination dot count value table TB102 (Figure 13) at 90% usage rate to generate a toner empty state. Then replace the toner cartridge 12 with a new one, and collect the printed matter immediately after that. · Example 2-2: Maintain the internal temperature and humidity of the apparatus at T [°C] ≤ 10 and 20 < H [%] ≤ 50 from the toner low state when the developing device usage rate is 90 [%] or more. Change the toner empty determination dot count value Dot_e3 from the reference toner empty determination dot count value Dot_st to 84000 as shown in the toner empty determination dot count value table TB102 (Figure 13) at 90% usage rate to generate a toner empty state. Then replace the toner cartridge 12 with a new one, and collect the printed matter immediately after that. · Example 2-3: Maintain the internal temperature and humidity of the apparatus at T [°C] ≤ 10 and 50 < H [%] ≤ 80 from the toner low state when the developing device usage rate is 90 [%] or more. Change the toner empty determination dot count value Dot_e3 from the reference toner empty determination dot count value Dot_st to 96000 as shown in the toner empty determination dot count value table TB102 (Figure 13) at 90% usage rate to generate a toner empty state. Then replace the toner cartridge 12 with a new one, and collect the printed matter immediately after that. · Example 2-4... With the usage rate of the developing device being 90% or more, maintain the internal temperature and humidity of the device at T[℃] ≤ 10 and 80 < H[%] in the toner-low state. Change the toner empty determination dot count value Dot_e3 from the reference toner empty determination dot count value Dot_st to 102000 as shown in the toner empty determination dot count value table TB102 (Figure 13) at 90% usage rate to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately after that. · Example 2-5... With the usage rate of the developing device being 90% or more, maintain the internal temperature and humidity of the device at 10 < T[℃] ≤ 20 and H[%] ≤ 20 in the toner-low state. Change the toner empty determination dot count value Dot_e3 from the reference toner empty determination dot count value Dot_st to 84000 as shown in the toner empty determination dot count value table TB102 (Figure 13) at 90% usage rate to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately after that. · Example 2-6... With the usage rate of the developing device being 90% or more, maintain the internal temperature and humidity of the device at 10 < T[℃] ≤ 20 and 20 < H[%] ≤ 50 in the toner-low state. Change the toner empty determination dot count value Dot_e3 from the reference toner empty determination dot count value Dot_st to 90000 as shown in the toner empty determination dot count value table TB102 (Figure 13) at 90% usage rate to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately after that. · Example 2-7... With the usage rate of the developing device being 90% or more, maintain the internal temperature and humidity of the device at 10 < T[℃] ≤ 20 and 50 < H[%] ≤ 80 in the toner-low state. Change the toner empty determination dot count value Dot_e3 from the reference toner empty determination dot count value Dot_st to 96000 as shown in the toner empty determination dot count value table TB102 (Figure 13) at 90% usage rate to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately after that. · Example 2-8... While the usage rate of the developing device is 90% or more, maintain the internal temperature and humidity of the device at 10 < T [°C] ≤ 20 and 80 < H [%] in the toner-low state. Change the toner empty determination dot count value Dot_e3 from the reference toner empty determination dot count value Dot_st to 108,000 as shown in the toner empty determination dot count value table TB102 (Figure 13) at 90% usage rate to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards · Example 2-9... While the usage rate of the developing device is 90% or more, maintain the internal temperature and humidity of the device at 20 < T [°C] ≤ 30 and H [%] ≤ 20 in the toner-low state. Change the toner empty determination dot count value Dot_e3 from the reference toner empty determination dot count value Dot_st to 90,000 as shown in the toner empty determination dot count value table TB102 (Figure 13) at 90% usage rate to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards · Example 2-10... While the usage rate of the developing device is 90% or more, maintain the internal temperature and humidity of the device at 20 < T [°C] ≤ 30 and 20 < H [%] ≤ 50 in the toner-low state. Change the toner empty determination dot count value Dot_e3 from the reference toner empty determination dot count value Dot_st to 96,000 as shown in the toner empty determination dot count value table TB102 (Figure 13) at 90% usage rate to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards · Example 2-11... While the usage rate of the developing device is 90% or more, maintain the internal temperature and humidity of the device at 20 < T [°C] ≤ 30 and 80 < H [%] in the toner-low state. Change the toner empty determination dot count value Dot_e3 from the reference toner empty determination dot count value Dot_st to 102,000 as shown in the toner empty determination dot count value table TB102 (Figure 13) at 90% usage rate to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards · Example 2-12... When the usage rate of the developing device is 90% or more, maintain the internal temperature and humidity of the device at 30 < T [°C] and H [%] ≤ 20 from the toner low state. Change the toner empty determination dot count value Dot_e3 from the reference toner empty determination dot count value Dot_st to 102000 as shown in the toner empty determination dot count value table TB102 (Figure 13) at 90% usage rate to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards · Example 2-13... When the usage rate of the developing device is 90% or more, maintain the internal temperature and humidity of the device at 30 < T [°C] and 20 < H [%] ≤ 50 from the toner low state. Change the toner empty determination dot count value Dot_e3 from the reference toner empty determination dot count value Dot_st to 108000 as shown in the toner empty determination dot count value table TB102 (Figure 13) at 90% usage rate to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards · Example 2-14... When the usage rate of the developing device is 90% or more, maintain the internal temperature and humidity of the device at 30 < T [°C] and 50 < H [%] ≤ 80 from the toner low state. Change the toner empty determination dot count value Dot_e3 from the reference toner empty determination dot count value Dot_st to 102000 as shown in the toner empty determination dot count value table TB102 (Figure 13) at 90% usage rate to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards · Example 2-15... When the usage rate of the developing device is 90% or more, maintain the internal temperature and humidity of the device at 30 < T [°C] and 80 < H [%] from the toner low state. Change the toner empty determination dot count value Dot_e3 from the reference toner empty determination dot count value Dot_st to 102000 as shown in the toner empty determination dot count value table TB102 (Figure 13) at 90% usage rate to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards · Example 2-16... When the usage rate of the developing device is 80% or more and less than 90%, maintain the internal temperature and humidity of the device at T[℃]≤10 and H[%]≤20 from the toner-low state. Change the toner empty determination dot count value Dot_e2 from the reference toner empty determination dot count value Dot_st to 84000 as shown in the toner empty determination dot count value table TB101 (Figure 12) at 80% usage rate to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards. · Example 2-17... When the usage rate of the developing device is 80% or more and less than 90%, maintain the internal temperature and humidity of the device at T[℃]≤10 and 20<H[%]≤50 from the toner-low state. Change the toner empty determination dot count value Dot_e2 from the reference toner empty determination dot count value Dot_st to 96000 as shown in the toner empty determination dot count value table TB101 (Figure 12) at 80% usage rate to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards. · Example 2-18... When the usage rate of the developing device is 80% or more and less than 90%, maintain the internal temperature and humidity of the device at T[℃]≤10 and 50<H[%]≤80 from the toner-low state. Change the toner empty determination dot count value Dot_e2 from the reference toner empty determination dot count value Dot_st to 102000 as shown in the toner empty determination dot count value table TB101 (Figure 12) at 80% usage rate to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards. · Example 2-19... When the usage rate of the developing device is 80% or more and less than 90%, maintain the internal temperature and humidity of the device at T[℃]≤10 and 80<H[%] from the toner-low state. Change the toner empty determination dot count value Dot_e2 from the reference toner empty determination dot count value Dot_st to 108000 as shown in the toner empty determination dot count value table TB101 (Figure 12) at 80% usage rate to generate a toner empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately afterwards. · Example 2-20... With the usage rate of the developing device being 80% or more and less than 90%, maintain the internal temperature and humidity of the device at 10 < T [°C] ≤ 20 and H [%] ≤ 20 from the toner-low state. Change the toner-empty determination dot count value Dot_e2 from the reference toner-empty determination dot count value Dot_st to 90,000 as shown in the toner-empty determination dot count value table TB101 (Figure 12) at 80% usage rate to generate a toner-empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately after that. · Example 2-21... With the usage rate of the developing device being 80% or more and less than 90%, maintain the internal temperature and humidity of the device at 10 < T [°C] ≤ 20 and 20 < H [%] ≤ 50 from the toner-low state. Change the toner-empty determination dot count value Dot_e2 from the reference toner-empty determination dot count value Dot_st to 96,000 as shown in the toner-empty determination dot count value table TB101 (Figure 12) at 80% usage rate to generate a toner-empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately after that. · Example 2-22... With the usage rate of the developing device being 80% or more and less than 90%, maintain the internal temperature and humidity of the device at 10 < T [°C] ≤ 20 and 50 < H [%] ≤ 80 from the toner-low state. Change the toner-empty determination dot count value Dot_e2 from the reference toner-empty determination dot count value Dot_st to 102,000 as shown in the toner-empty determination dot count value table TB101 (Figure 12) at 80% usage rate to generate a toner-empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately after that. · Example 2-23... With the usage rate of the developing device being 80% or more and less than 90%, maintain the internal temperature and humidity of the device at 10 < T [°C] ≤ 20 and 80 < H [%] from the toner-low state. Change the toner-empty determination dot count value Dot_e2 from the reference toner-empty determination dot count value Dot_st to 108,000 as shown in the toner-empty determination dot count value table TB101 (Figure 12) at 80% usage rate to generate a toner-empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately after that. · Example 2-24... When the usage rate of the developing device is 80% or more and less than 90%, maintain the internal temperature and humidity of the device at 20 < T [°C] ≤ 30 and H [%] ≤ 20 from the toner-low state. Change the toner-empty determination dot count value Dot_e2 from the reference toner-empty determination dot count value Dot_st to 96,000 as shown in the toner-empty determination dot count value table TB101 (Figure 12) at 80% usage rate to generate a toner-empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately after that. · Example 2-25... When the usage rate of the developing device is 80% or more and less than 90%, maintain the internal temperature and humidity of the device at 20 < T [°C] ≤ 30 and 20 < H [%] ≤ 50 from the toner-low state. Change the toner-empty determination dot count value Dot_e2 from the reference toner-empty determination dot count value Dot_st to 102,000 as shown in the toner-empty determination dot count value table TB101 (Figure 12) at 80% usage rate to generate a toner-empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately after that. · Example 2-26... When the usage rate of the developing device is 80% or more and less than 90%, maintain the internal temperature and humidity of the device at 20 < T [°C] ≤ 30 and 80 < H [%] from the toner-low state. Change the toner-empty determination dot count value Dot_e2 from the reference toner-empty determination dot count value Dot_st to 108,000 as shown in the toner-empty determination dot count value table TB101 (Figure 12) at 80% usage rate to generate a toner-empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately after that. · Example 2-27... When the usage rate of the developing device is 80% or more and less than 90%, maintain the internal temperature and humidity of the device at 30 < T [°C] and H [%] ≤ 20 from the toner-low state. Change the toner-empty determination dot count value Dot_e2 from the reference toner-empty determination dot count value Dot_st to 108,000 as shown in the toner-empty determination dot count value table TB101 (Figure 12) at 80% usage rate to generate a toner-empty state. Then replace the toner cartridge 12 with a new one and collect the printed matter immediately after that. · Example 2-28... While the usage rate of the developing device is 80% or more and less than 90%, maintain the internal temperature and humidity of the device at 30 < T [°C] and 20 < H [%] ≤ 50 in the toner-low state. Keep the toner-empty determination dot count value Dot_e2 as the reference toner-empty determination dot count value Dot_st, generate a toner-empty state, then replace the toner cartridge 12 with a new one, and collect the printed matter immediately after that. · Example 2-29... While the usage rate of the developing device is 80% or more and less than 90%, maintain the internal temperature and humidity of the device at 30 < T [°C] and 50 < H [%] ≤ 80 in the toner-low state. Change the toner-empty determination dot count value Dot_e2 from the reference toner-empty determination dot count value Dot_st to 108000 as shown in the toner-empty determination dot count value table TB101 (Figure 12) at 80% usage rate to generate a toner-empty state, then replace the toner cartridge 12 with a new one, and collect the printed matter immediately after that. · Example 2-30... While the usage rate of the developing device is 80% or more and less than 90%, maintain the internal temperature and humidity of the device at 30 < T [°C] and 80 < H [%] in the toner-low state. Change the toner-empty determination dot count value Dot_e2 from the reference toner-empty determination dot count value Dot_st to 102000 as shown in the toner-empty determination dot count value table TB101 (Figure 12) at 80% usage rate to generate a toner-empty state, then replace the toner cartridge 12 with a new one, and collect the printed matter immediately after that.

[0118] [2-5-2. Evaluation of dirt] In this evaluation, the dirt on the paper surface was evaluated by the same evaluation method as in the first embodiment. The evaluation results are shown in Figure 14.

[0119] [2-5-3. Evaluation of fogging] In this evaluation, the fogging was evaluated by the same evaluation method as in the first embodiment. The evaluation results are shown in Figure 14.

[0120] [2-5-4. Comprehensive determination] In this evaluation, a comprehensive evaluation was performed by the same evaluation method as in the first embodiment. The evaluation results are shown in Figure 14.

[0121] [2-6. Effects, etc.] In the image forming device 1 according to the first embodiment, when the toner cartridge 12 is replaced in a toner-empty state, the charge difference between the residual toner remaining in the developing device 11 and the newly supplied toner supplied from the new toner cartridge 12 can be reduced, thereby preventing the occurrence of smudges and fogging due to the charge difference between the residual toner and the newly supplied toner, and improving print quality.

[0122] However, when the usage rate of developing device 11 relative to the lifespan of the developing device increases and developing device 11 approaches the end of its lifespan, wear of each roller in developing device 11 progresses, and the frequency of occurrence of stains and fogging increases. As a result, it becomes difficult to simultaneously suppress both stains and fogging, and the stain and fogging prevention printing control of image forming apparatus 1 may sometimes be somewhat insufficient.

[0123] In response to this, image forming apparatus 101 first changes the amount of toner available from when a toner-low state occurs until a toner-empty state is determined to be, to an appropriate value, in accordance with the internal temperature and humidity (internal temperature T and internal humidity H) that indicate the environment in which image forming apparatus 101 is placed, just like image forming apparatus 1. Specifically, image forming apparatus 101, like image forming apparatus 1, determines a toner-empty state when there is more toner remaining in developing device 11 in a low humidity environment when a toner-low state occurs than in a high humidity environment. Also, image forming apparatus 1 determines a toner-empty state when there is more toner remaining in developing device 11 in a low temperature environment when a toner-low state occurs than in a high temperature environment.

[0124] In addition, the image forming apparatus 101 changes the amount of toner available from when a toner-low state occurs until a toner-empty state is determined to be an appropriate value according to the drum count Dr (specifically, the developing device usage rate), which is the number of rotations of the photoconductor drum 37. Specifically, after a toner-low state occurs, the image forming apparatus 101 determines that a toner-empty state is occurring when the remaining toner amount is large as the drum count Dr approaches the drum count life Dr_end, which is a predetermined number of rotations, and the developing device 11 approaches the end of its life.

[0125] Therefore, compared to the image forming device 1, which changes the amount of usable toner from when a toner-low state occurs until a toner-empty state is determined in accordance only with the temperature and humidity inside the device (temperature T inside the device and humidity H inside the device) regardless of the drum count Dr, the image forming device 101 can reduce the charge difference between the remaining toner remaining in the developing device 11 and the newly supplied toner supplied from the new toner cartridge 12 when the toner cartridge 12 is replaced in a toner-empty state, taking into consideration the increased frequency of stains and fogging caused by the wear of the rollers in the developing device 11. This allows the image forming device 101 to reduce the occurrence of stains and fogging caused by the charge difference between the remaining toner and the newly supplied toner, improving print quality.

[0126] FIG. 15(A) shows the measurement results of the image forming apparatus of the comparative example, in which all the toner empty determination dot count values ​​Dot_e2 in the toner empty determination dot count value table TB101 (FIG. 12) at 80% usage rate are set as the reference toner empty determination dot count value Dot_st. The temperature T inside the apparatus during this measurement is 9 to 12°C, and the humidity H inside the apparatus is 10 to 14%. FIG. 15(A) also shows a state in which the usage rate of the developing device is 80%. The graph Gr180te on the left side of FIG. 15(A) shows the potential and toner adhesion amount on the developing roller 35 when the toner empty state occurs. The graph Gr180tc on the right side of FIG. 15(A) also shows the potential and toner adhesion amount on the developing roller 35 immediately after the toner cartridge 12 is replaced with a new one after the toner empty state occurs and newly supplied toner is supplied from the toner cartridge 12 to the developing device 11. In comparison with graph Gr180te, graph Gr180tc shows that the potential on the developing roller 35 is increased by about -20 [V], and the amount of toner attached to the developing roller 35 is 0.4 [mg cm 2 ] has increased by some degree.

[0127] In this way, when the developer usage rate is 80%, the potential and amount of toner adhesion on the developing roller 35 are more likely to increase immediately after the toner cartridge 12 is replaced with a new one and newly supplied toner is supplied from the toner cartridge 12 to the developing device 11 after the toner empty state occurs, compared to when the developer usage rate is 50% as in the first embodiment (Figure 9).

[0128] On the other hand, FIG. 15(B) shows the measurement results in the case of the image forming apparatus 101 of this embodiment, in which the toner empty determination dot count value Dot_e2 in the toner empty determination dot count value table TB101 (FIG. 12) at a usage rate of 80% is appropriately changed to the reference toner empty determination dot count value Dot_st as shown in FIG. 12. FIG. 15(B) shows the state in which the usage rate of the developing device is 80[%], as in FIG. 15(A). The graph Gr80te on the left side of FIG. 15(B) shows the potential and toner adhesion amount on the developing roller 35 when the toner empty state occurs, as in the graph Gr180te. Also, the graph Gr80tc on the right side of FIG. 15(B) shows the potential and toner adhesion amount on the developing roller 35 immediately after the toner cartridge 12 is replaced with a new one after the toner empty state occurs and newly supplied toner is supplied from the toner cartridge 12 to the developing device 11, as in the graph Gr180tc. In comparison with graph Gr80te, graph Gr80tc shows that the potential on the developing roller 35 is increased by about -5 [V], and the amount of toner attached to the developing roller 35 is 0.15 [mg cm 2 ] has increased by some degree.

[0129] As shown in Figures 15(A) and 15(B), when the developing device usage rate is 80%, the image forming apparatus 101 according to this embodiment is able to suppress an increase in the potential and amount of toner adhesion on the developing roller 35 immediately after the toner cartridge 12 is replaced with a new one and newly supplied toner is supplied from the toner cartridge 12 to the developing device 11 after the toner empty state occurs, compared to the comparative example.

[0130] FIG. 15C shows the measurement results of the image forming apparatus of the comparative example in which all the toner empty determination dot count values ​​Dot_e3 in the toner empty determination dot count value table TB102 (FIG. 13) at a usage rate of 90% are set as the reference toner empty determination dot count value Dot_st. FIG. 15C also shows the state in which the usage rate of the developing device is 90%. The graph Gr190te on the left side of FIG. 15C shows the potential and toner adhesion amount on the developing roller 35 when the toner empty state occurs. The graph Gr190tc on the right side of FIG. 15C also shows the potential and toner adhesion amount on the developing roller 35 immediately after the toner cartridge 12 is replaced with a new one after the toner empty state occurs and newly supplied toner is supplied from the toner cartridge 12 to the developing device 11. In comparison with graph Gr190te, graph Gr190tc shows that the potential on the developing roller 35 is increased by about -35 [V], and the amount of toner attached to the developing roller 35 is 0.55 [mg cm 2 ] has increased by some degree.

[0131] In this way, when the developer usage rate is 90%, the potential and amount of toner adhesion on the developing roller 35 are more likely to increase immediately after the toner cartridge 12 is replaced with a new one and newly supplied toner is supplied from the toner cartridge 12 to the developing device 11 after the toner empty state occurs, compared to when the developer usage rate is 80% as in Figure 15 (A).

[0132] On the other hand, FIG. 15(D) shows the measurement result in the case of the image forming apparatus 101 of the present embodiment, in which the toner empty determination dot count value Dot_e3 in the toner empty determination dot count value table TB102 (FIG. 13) at a usage rate of 90% is appropriately changed to the reference toner empty determination dot count value Dot_st as shown in FIG. 13. FIG. 15(D) shows the state where the usage rate of the developing device is 90[%], similar to FIG. 15(C). The graph Gr90te on the left side of FIG. 15(D) shows the potential and toner adhesion amount on the developing roller 35 when the toner empty state occurs, similar to the graph Gr190te. Also, the graph Gr90tc on the right side of FIG. 15(D) shows the potential and toner adhesion amount on the developing roller 35 immediately after the toner cartridge 12 is replaced with a new one after the toner empty state occurs and newly supplied toner is supplied from the toner cartridge 12 to the developing device 11, similar to the graph Gr190tc. In comparison with graph Gr90te, graph Gr90tc shows that the potential on the developing roller 35 is increased by about -5 [V], and the amount of toner attached to the developing roller 35 is 0.15 [mg cm 2 ] has increased by some degree.

[0133] As shown in Figures 15(D) and 15(C), when the developing device usage rate is 90%, image forming apparatus 101 according to this embodiment is able to suppress an increase in the potential and amount of toner adhesion on developing roller 35 immediately after toner cartridge 12 is replaced with a new one and newly supplied toner is supplied from toner cartridge 12 to developing device 11 after a toner empty state occurs, compared to the comparative example.

[0134] In this way, even if the developing device usage rate increases and the potential and amount of toner adhesion on the developing roller 35 are more likely to increase than when the developing device usage rate is low, the image forming device 101 can maintain the charging characteristics of the remaining toner close to those of newly supplied toner by optimizing the amount of toner remaining in the developing device 11 according to the environment.

[0135] In addition, image forming apparatus 101 according to the second embodiment can achieve the same effects as image forming apparatus 1 according to the first embodiment.

[0136] 3. Other embodiments In the first embodiment described above, the image forming device 1 prepares a toner empty determination dot count value Dot_e1 that increases as at least one of the internal device temperature T or internal device humidity H decreases, sets the toner empty determination dot count value Dot_e1 to the toner empty determination dot count Dot_E based on the internal device temperature T and internal device humidity H, accumulates the dot count Dot required for printing as the dot count used after a toner low occurs, and determines that the toner is empty when the dot count used after a toner low occurs is equal to or greater than the toner empty determination dot count Dot_E. The present invention is not limited to this, and the image forming apparatus 1 may set the toner empty determination dot count Dot_E to a uniform value regardless of the internal device temperature T and internal device humidity H, prepare a toner consumption correction coefficient that increases as the internal device temperature T or internal device humidity H decreases, determine the toner consumption correction coefficient based on the internal device temperature T and internal device humidity H, and multiply the dot count Dot required for printing after the toner low state occurs by the toner consumption correction coefficient, so that the lower at least one of the internal device temperature T or internal device humidity H is, the larger the calculated dot count Dot becomes than the actual dot count Dot, and accumulate it as the dot count used after the toner low state occurs, and determine that the toner empty state exists when the dot count used after the toner low state occurs is equal to or greater than the toner empty determination dot count Dot_E. The same applies to the second embodiment.

[0137] In the above-described first embodiment, the image forming apparatus 1 has been described as selecting and setting the toner empty determination dot count Dot_E from the toner empty determination dot count value Dot_e1 in the toner empty determination dot count value table TB1 (FIG. 5) based on the internal device temperature T and the internal device humidity H. The present invention is not limited to this, and the image forming apparatus 1 may select and set the toner empty determination dot count Dot_E from the toner empty determination dot count value Dot_e1 based on at least one of the internal device temperature T and the internal device humidity H. The same is true in the second embodiment.

[0138] Furthermore, in the above-mentioned second embodiment, the image forming apparatus 101 has been described as using two toner empty determination dot count value tables: a toner empty determination dot count value table TB101 (FIG. 12) for an 80% usage rate when the development device usage rate is 80% or more and less than 90%, and a toner empty determination dot count value table TB102 (FIG. 13) for a 90% usage rate when the development device usage rate is 90% or more. The present invention is not limited to this, and the image forming apparatus 101 may use toner empty determination dot count value tables corresponding to various other developer usage rates.

[0139] Furthermore, in the above-described second embodiment, the image forming apparatus 101 has been described as using the drum count Dr of the photoconductor drum 37 as the developing device usage rate. However, the present invention is not limited to this, and the image forming apparatus 101 may use the usage rates of various other rollers, such as the supply roller 34 and the developing roller 35, as the developing device usage rate.

[0140] Furthermore, in the above-described embodiment, the present invention has been described as being applied to the direct transfer type image forming apparatus 1 or 101. However, the present invention is not limited to this, and may be applied to printers of various types, such as an intermediate transfer type in which a toner image that has been primarily transferred onto an intermediate transfer belt is secondarily transferred onto paper.

[0141] Furthermore, in the above-described embodiment, the present invention has been described as being applied to the image forming apparatus 1 or 101 using four image forming units 10. However, the present invention is not limited to this, and the present invention may be applied to a monochrome image forming apparatus using one process unit, or an image forming apparatus using any number of image forming units, such as two, three, five or more.

[0142] Furthermore, in the above-described embodiment, the present invention has been described as being applied to the image forming apparatus 1 or 101, which is an electrophotographic printer. However, the present invention is not limited to this, and the present invention may be applied to image forming apparatuses having various other functions, such as a copying machine, a facsimile machine, or an MFP (Multi Function Peripheral) having the functions of an automatic document reader, etc.

[0143] Furthermore, in the above-described embodiment, the present invention has been described as being applied to the image forming apparatus 1 or 101 that prints on pre-cut paper. However, the present invention is not limited to this, and the present invention may also be applied to an image forming apparatus that is a label printer that prints on rolled paper.

[0144] Furthermore, the present invention is not limited to the above-mentioned embodiments and other embodiments. That is, the scope of application of the present invention extends to embodiments in which the above-mentioned embodiments and the other embodiments are combined in part or in whole in any manner. The scope of application of the present invention also extends to embodiments in which a part of the configuration described in any of the above-mentioned embodiments and other embodiments is extracted and replaced or diverted with a part of the configuration of any of the above-mentioned embodiments and other embodiments, or an embodiment in which a part of the extracted configuration is added to any of the embodiments.

[0145] Furthermore, in the above-mentioned first embodiment, a case has been described in which the image forming apparatus 1 is configured as an image forming apparatus by the image forming unit 10 as an image forming unit, the detection section 74 as a detection section, the measurement section 75 as a measurement section, and the determination section 76 as a determination section. The present invention is not limited to this, and the image forming apparatus may be configured by an image forming unit, a detection section, a measurement section, and a determination section having various other configurations. [Industrial Applicability]

[0146] The present invention can be used in electrophotographic printers. [Explanation of symbols]

[0147] 1, 101...image forming apparatus, 2...casing, 4...paper cassette, 5...hopping roller, 6, 7...pinch roller, 8...conveyor roller, 9...registration roller, 10...image forming unit, 11...developing device, 12...toner cartridge, 13...print head, 14...temperature and humidity sensor, 15, 115...control unit, 16...host device, 17...density sensor, 20...transfer conveyor unit, 21...front conveyor roller, 22...rear conveyor roller, 23...transfer belt, 24...transfer roller, 25...fixing unit, 26, 27...pinch roller, 28, 29...exhaust Output roller, 30... stacker unit, 31... heat roller, 32... fixing belt, 33... charging roller, 34... supply roller, 35... developing roller, 36... developing blade, 37... photoconductor drum, 38... cleaning blade, 39... toner storage space, 40... toner sensor, 50, 150... print control unit, 51, 151... toner usage control unit, 53... interface control unit, 54... operation display unit, 55... memory, 56... ROM, 57... RAM, 58A, 58B... device internal temperature recording unit, 59A, 59B... device internal humidity recording unit, 60A, 60B: Transfer belt temperature recording unit, 61A, 61B: Date and time recording unit, 63: Various sensors, 64: Process control unit, 65: Development voltage control unit, 66: Supply voltage control unit, 67: Layer formation voltage control unit, 68: Charge voltage control unit, 69: Exposure control unit, 70: Motor control unit, 71: Transfer voltage control unit, 74: Detection unit, 75: Measurement unit, 76: Determination unit, 77: Low determination unit, 78: Developer usable amount setting unit, 80: Stains, 82: Blank page unit, 84: Fog generation unit, TB1: Toner empty determination dot count value table, TB101: Usage rate Table of dot count values ​​to determine toner empty when the toner usage rate is 80%, TB102...Table of dot count values ​​to determine toner empty when the usage rate is 90%, P...Paper, Dr...Drum count, Dot...Dot count, Dot_L...Dot count when toner low occurs, Dot_E...Dot count to determine toner empty, Dot_e1, Dot_e2, Dot_e3...Dot count values ​​to determine toner empty, Dot_st...Standard dot count value to determine toner empty, Dr_end...Drum count life, Drth90...Drum count threshold when usage rate is 90%,Drth80: Drum count threshold when usage rate is 80%, T: Temperature inside the device, H: Humidity inside the device, W: Transport path, P: Paper.

Claims

1. an image forming unit for forming a developer image; a detection unit for detecting an amount of developer in the image forming unit; a measuring unit that measures at least one of the humidity and the temperature around the image forming unit; a determination unit for determining whether the amount of developer is equal to or less than a predetermined value; having When the determination unit determines that the amount of developer in the image forming unit is equal to or less than the predetermined value, the amount of developer when at least one of the humidity or the temperature measured by the measurement unit is equal to or less than the predetermined humidity or the predetermined temperature is greater than the amount of developer when at least one of the humidity or the temperature measured by the measurement unit is higher than the predetermined humidity or the predetermined temperature. Image forming device.

2. The measuring unit measures the humidity around the image forming unit, When the determining unit determines that the amount of developer is equal to or less than the predetermined value, the amount of developer when the humidity measured by the measuring unit is equal to or less than the predetermined humidity is greater than the amount of developer when the humidity measured by the measuring unit is higher than the predetermined humidity. The image forming apparatus according to claim 1 .

3. the measuring unit measures the humidity and temperature around the image forming unit; When the determination unit determines that the amount of developer is equal to or less than the predetermined value, the amount of developer when the humidity and temperature measured by the measurement unit are equal to or less than the predetermined humidity and equal to or less than the predetermined temperature is greater than the amount of developer when the humidity and temperature measured by the measurement unit are higher than the predetermined humidity and higher than the predetermined temperature. The image forming apparatus according to claim 2 .

4. a low determination unit that determines whether the amount of developer is equal to or less than a predetermined low value; a developer usable amount setting unit that sets a developer usable amount, which is an amount of the developer that can be used from when the low determination unit determines that the developer amount is equal to or less than the low predetermined value until when the determination unit determines that the developer amount is equal to or less than the predetermined value, to a smaller amount when at least one of the humidity or the temperature measured by the measurement unit is equal to or less than the predetermined humidity or the predetermined temperature, than when at least one of the humidity or the temperature measured by the measurement unit is higher than the predetermined temperature or the predetermined humidity; and The determination unit is When the developer is used in an amount equal to or greater than the usable amount of developer after the low determination unit determines that the amount of developer is equal to or less than the low predetermined value, the developer amount is determined to be equal to or less than the predetermined value. The image forming apparatus according to claim 1 .

5. The developer usable amount setting unit is The usable amount of developer is set to be smaller when the usage rate of the image forming unit is high than when the usage rate is low. The image forming apparatus according to claim 4 .

6. The developer usable amount setting unit is When the usage rate is equal to or greater than a predetermined first life judgment value, the usable amount of developer is set to be smaller than when the usage rate is equal to or greater than a predetermined second life judgment value lower than the first life judgment value and less than the first life judgment value. The image forming apparatus according to claim 5 .

7. The developer usable amount setting unit is When at least one of the humidity and the temperature measured by the measuring unit is equal to or lower than the predetermined humidity or the predetermined temperature, the usable amount of developer is set to be less than a predetermined reference value. The image forming apparatus according to claim 4 .

8. The developer usable amount setting unit is When the image forming unit reaches the end of its life, the amount of developer that can be used is returned to the reference value. The image forming apparatus according to claim 7.

9. The determination unit is At a time when new developer should be mixed with the developer remaining in the image forming unit, it is determined that the amount of developer has become equal to or less than the predetermined value. The image forming apparatus according to claim 1 .

Images