Image forming apparatus

Abstract

The objective is to provide an image forming apparatus that, when the developing roller is not in contact with the photoreceptor drum, applies voltage while rotating the photoreceptor drum using a motor, and then, when the developing roller is in contact with the photoreceptor drum, determines whether or not toner has solidified in the toner storage section based on the rotation of the process motor. [Solution] With the developing roller in the separated position, the photoreceptor drum is rotated using a process motor while a voltage is applied to the charger using a high-voltage power supply board. Then, with the developing roller moved from the separated position to the contact position using a contact separation mechanism, a toner adhesion determination process is performed to determine whether or not toner has adhered in the toner storage section based on the rotation of the process motor.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus that determines toner fixation.

Background Art

[0002] Conventionally, in an image forming apparatus including a developing cartridge having a developer accommodating portion that accommodates toner and a developing roller that supplies toner to a photosensitive drum, toner may fix inside the developing cartridge when the developing cartridge is left standing at high temperature.

[0003] Here, Japanese Patent Laid-Open No. 2002-148886 proposes a technique that includes a motor for driving a toner stirring member, estimates the state of toner by comparing the rotation speed of the motor with an initially set target speed, and determines toner fixation.

Prior Art Literature

Patent Literature

[0004]

Patent Literature 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] Patent Document 1 discloses a technique for determining toner adhesion by the speed of a motor that rotates a component that contacts the toner. On the other hand, an image forming apparatus has a mechanism that allows the developing roller to contact the photoreceptor drum and a mechanism that allows the developing roller to not contact the photoreceptor drum, and when the developing roller is in contact with the photoreceptor drum, the driving force from the motor is transmitted to the developing roller so that the developing roller can rotate. In such an image forming apparatus, by using the developing roller as the component that contacts the toner, it is conceivable to determine toner adhesion by the speed of the motor that rotates the developing roller. However, in such an image forming apparatus, the developing roller does not rotate unless it is in contact with the photoreceptor drum, so when the developing roller is rotated to detect the state of the toner in the developing cartridge as in Patent Document 1, the toner moves from the developing roller to the photoreceptor drum, resulting in the problem of wasted toner in the developing cartridge.

[0006] The present invention was made to solve the aforementioned problems of the conventional invention, and aims to provide an image forming apparatus that applies voltage while rotating the photoreceptor drum using a motor when the developing roller is not in contact with the photoreceptor drum, and then determines whether or not toner has solidified in the toner storage section based on the rotation of the process motor when the developing roller is in contact with the photoreceptor drum. [Means for solving the problem]

[0007] To achieve the above objective, the image forming apparatus according to the present invention includes a developing cartridge having a photoreceptor drum, a charger for charging the photoreceptor drum, a toner storage section for storing toner, and a developing roller for supplying the toner to the photoreceptor drum; a contact-separation mechanism for moving the developing roller between a contact position in contact with the photoreceptor drum and a separation position away from the photoreceptor drum; a process motor for rotating the photoreceptor drum and the developing roller; and a drive transmission mechanism for transmitting the driving force from the process motor to the developing roller, wherein when the developing roller is in the contact position, the driving force from the process motor is transmitted to the developing roller, and the developing roller The device comprises a drive transmission mechanism that does not transmit the driving force from the process motor to the developing roller when it is in the separated position, a high-voltage power supply board that applies a voltage to the charger to charge the photoreceptor drum, and a control unit, wherein the control unit, when the developing roller is in the separated position, rotates the photoreceptor drum using the process motor and applies the voltage to the charger using the high-voltage power supply board, and then, when the developing roller is moved from the separated position to the contact position using the contact separation mechanism, performs a toner adhesion determination process that determines whether or not toner has adhered in the toner storage section based on the rotation of the process motor.

[0008] According to this, when the toner adhesion detection process is performed, a potential difference is created between the photoreceptor drum and the developing roller in advance when they are separated. This prevents toner from flowing from the developing roller towards the photoreceptor drum even when the photoreceptor drum and the developing roller come into contact.

[0009] The image forming apparatus may also be characterized in that, when the control unit applies the voltage to the charger using the high-voltage power supply board while the developing roller is in the separated position, after the process motor reaches a first predetermined rotational speed corresponding to one or more rotations of the photoreceptor drum, it uses the contact separation mechanism to move the developing roller from the separated position to the contact position.

[0010] According to this method, a potential difference can be created between the entire surface of the photoreceptor drum and the developing roller, thus eliminating any possibility of toner flowing from the developing roller towards the photoreceptor drum.

[0011] The image forming apparatus may be characterized in that, when the control unit determines toner adhesion based on the rotation of the process motor while the developing roller has been moved from the separated position to the contact position using the contact separation mechanism, if the rotation speed of the process motor reaches a second predetermined number of times or more within a first predetermined time, it does not determine toner adhesion, and if the rotation speed of the process motor does not reach a second predetermined number of times or more within the first predetermined time, it determines toner adhesion.

[0012] According to this method, toner adhesion can be determined by monitoring the rotation speed of the process motor.

[0013] The image forming apparatus is a three-phase brushless motor having a three-phase drive coil, a Hall element for detecting the rotational position of the rotor, and an FG sensor that generates an induced electromotive force as the rotor rotates. The apparatus further includes a motor drive circuit that controls the amount of current supplied to the three-phase drive coil and switches the timing of supplying current to the three-phase drive coil in accordance with a control signal input from the control unit. The control unit may be characterized in that, when rotating the process motor, it detects the rotational speed of the process motor based on a Hall signal from the Hall element input via the motor drive circuit, detects the rotational speed of the motor based on an FG signal from the FG sensor input via the motor drive circuit, and performs feedback control that changes the pulse width of the control signal output to the motor drive circuit in accordance with the rotational speed.

[0014] According to this, the control unit can precisely control the speed of the process motor, thereby optimizing its operating performance.

[0015] In addition to the preceding, the image forming apparatus may further include a non-volatile memory in which predetermined upper limits of the pulse width of the control signal are stored for each manufacturer of the process motor, so as the amount of current supplied to the drive coil of the process motor increases, the drive transmission mechanism is not damaged by the rotation of the process motor, and the control unit may be characterized in that, when it determines the manufacturer of the process motor based on the signal from the process motor and performs feedback control to change the pulse width of the control signal output to the motor drive circuit according to the rotation speed, it sets the upper limit of the pulse width of the control signal to the upper limit of the manufacturer stored in the non-volatile memory.

[0016] According to this, the upper limit of the control signal pulse width is determined according to the values ​​specific to each process motor manufacturer, thus preventing damage to the drive transmission mechanism without excessively rotating the process motor.

[0017] The image forming apparatus further comprises a fixing apparatus for thermally fixing a toner image formed on a sheet by the photoreceptor drum, the fixing apparatus having a heating rotating body with a heater, a pressing rotating body that presses the sheet against the heating rotating body, and a main motor for rotating the rotating body of the fixing apparatus, wherein the contact separation mechanism is characterized in that the developing roller is movable between the contact position and the separation position by the driving force from the main motor.

[0018] According to this, the image forming apparatus can fix the toner image using the fixing device, and furthermore, the developing roller can be moved with the same driving force.

[0019] The image forming apparatus may be characterized in that the toner is a positively charged toner that is charged with positive polarity, and when the control unit applies the voltage to the charger using the high-voltage power supply board while the developing roller is in the separated position, it applies a positive first voltage to the charger using the high-voltage power supply board so that the photoreceptor drum has a higher voltage than the developing roller.

[0020] According to this method, applying a positive voltage to the charger creates a potential difference between the photoreceptor drum and the developing roller, preventing positively charged toner from flowing from the developing roller to the photoreceptor drum even when the two are in contact.

[0021] The image forming apparatus may be characterized in that, when the toner is a positively charged toner that is charged with positive polarity, the control unit applies a second positive voltage to the charger using the high-voltage power supply board when the developing roller is in the separated position, and applies a positive developing voltage to the developing roller, and the voltage difference between the second voltage and the developing voltage causes the photoreceptor drum to have a higher voltage than the developing roller.

[0022] According to this method, by applying a positive voltage to the charger and the developing roller, a potential difference is created between the photoreceptor drum and the developing roller, preventing positively charged toner from flowing from the developing roller to the photoreceptor drum even when the photoreceptor drum and the developing roller are in contact.

[0023] The image forming apparatus may be characterized in that the toner is a negatively charged toner, and when the control unit applies the voltage to the charger using the high-voltage power supply board while the developing roller is in the separated position, it applies a negative third voltage to the charger using the high-voltage power supply board so that the voltage of the photoreceptor drum is lower than that of the developing roller.

[0024] According to this configuration, applying a negative voltage to the charging unit generates a potential difference between the photosensitive drum and the developing roller, which can prevent negatively charged toner from flowing from the developing roller to the photosensitive drum even when the photosensitive drum and the developing roller are in contact with each other.

[0025] The image forming apparatus may further include a cover, the developing cartridge is detachable from the image forming apparatus when the cover is opened, and the control unit may execute the toner adhesion determination process when the image forming apparatus is started for the first time or when it is detected that the developing cartridge is installed.

[0026] According to this configuration, even if the internal toner adheres due to the influence of temperature changes during transportation or long-term storage of the image forming apparatus or the developing cartridge, the toner adhesion determination can be performed before starting printing.

[0027] In addition to the above features, in the image forming apparatus, the photosensitive drum is a plurality of photosensitive drums, the developing cartridges are a plurality of developing cartridges arranged correspondingly to each of the plurality of photosensitive drums, and the control unit may execute the toner adhesion determination process in a state where one developing cartridge among the plurality of developing cartridges is installed, and determine whether toner adheres to said one developing cartridge.

[0028] According to this configuration, since toner adhesion is determined for one developing cartridge, it is possible to determine whether toner adheres to the corresponding developing cartridge.

[0029] In addition to the preceding, the image forming apparatus may further include a display unit, and the control unit, when it performs the toner solidification determination process with one of the plurality of developing cartridges installed, and does not determine that the toner is solidified, may display on the display unit an instruction to remove the one developing cartridge and an instruction to install a developing cartridge different from the one developed cartridge.

[0030] According to this method, it is possible to sequentially determine the toner adhesion of each developing cartridge, and to determine the adhesion of each individual toner.

[0031] In addition to the preceding steps, the image forming apparatus may also be characterized in that each of the plurality of developing cartridges has a storage unit, and the control unit, when it determines that toner has solidified as a result of the toner solidification determination process performed with one of the developing cartridges installed, performs a toner solidification information storage process to store toner solidification information in the storage unit of the one developing cartridge.

[0032] According to this, by storing toner adhesion information, it is possible to record that toner has adhered to a developing cartridge where toner has adhered.

[0033] In addition to the preceding, the image forming apparatus may be characterized in that, after the toner adhesion information storage process, when a new developing cartridge is installed, the control unit executes the toner adhesion determination process if toner adhesion information is not stored in the storage unit of the newly installed developing cartridge, and does not execute the toner adhesion determination process if toner adhesion information is stored in the storage unit of the installed developing cartridge.

[0034] According to this method, unintended and duplicate toner adhesion detection processes can be eliminated by determining toner adhesion information. In addition, the process of driving the developing roller of a developing cartridge with toner adhesion can be reduced.

[0035] The image forming apparatus further comprises a cover and a display unit, wherein the photoreceptor drum is a plurality of photoreceptor drums, and the developing cartridges are arranged corresponding to each of the plurality of photoreceptor drums and are detachable from the image forming apparatus when the cover is open, and the control unit, when all of the plurality of developing cartridges are installed, performs the toner solidification determination process and determines that toner solidification has occurred, displays an instruction on the display unit to install only the developing cartridge containing black toner, and thereafter performs the toner solidification determination process with only the developing cartridge containing black toner installed, and if it does not determine that toner solidification has occurred, displays on the display unit that monochrome printing is possible, and if it determines that toner solidification has occurred, displays an error message on the display unit indicating that printing is not possible.

[0036] According to this, even if toner solidifies in a developer cartridge other than the one containing black toner, monochrome printing can still be performed using the developer cartridge containing black toner, allowing the user to print until a new developer cartridge is installed.

[0037] In addition to the features described above, the image forming apparatus may also be characterized in that the control unit rotates the process motor while the developing roller is in the separated position, determines whether the rotational speed of the process motor reaches a target speed within a second predetermined time, and determines that the process motor is faulty if the target speed is not reached within the second predetermined time, and the toner adhesion determination process is performed after the execution of the fault determination process if the process motor is not determined to be faulty.

[0038] According to this method, the toner solidification is determined only after it has been confirmed that the process motor is not malfunctioning. This prevents the system from mistakenly detecting toner solidification as being caused by a malfunctioning process motor. [Effects of the Invention]

[0039] According to the image forming apparatus of the present invention having the above-mentioned features, a potential difference is generated between the photoreceptor drum and the developing roller, so even if the photoreceptor drum and the developing roller come into contact, it is possible to determine toner adhesion without toner flowing from the developing roller towards the photoreceptor drum. [Brief explanation of the drawing]

[0040] [Figure 1] This is a schematic diagram of the image forming apparatus according to this embodiment. [Figure 2] This is a block diagram showing the configuration of the image forming apparatus according to this embodiment. [Figure 3] This is a schematic diagram of the drive transmission mechanism according to this embodiment. [Figure 4] This is a schematic diagram of the process motor according to this embodiment. [Figure 5] This diagram illustrates the high-voltage substrate used in the toner adhesion detection process. [Figure 6] This diagram illustrates the relationship between static charge and toner movement. [Figure 7] This is a flowchart for the toner adhesion detection process. [Figure 8] This is a flowchart for determining motor failure. [Figure 9] This is a flowchart for toner swapping. [Figure 10] This is a flowchart for the mode used to determine solid coloration. [Figure 11] This is a flowchart for determining whether monochrome printing is possible. [Modes for carrying out the invention]

[0041] Hereinafter, one embodiment of the image forming apparatus according to the present invention will be described in detail with reference to the drawings. First, Figure 1 is a schematic diagram of the image forming apparatus according to this embodiment.

[0042] As shown in Figure 1, the image forming apparatus 1 is a color printer and comprises a housing 10, a display unit 14, a front cover 11, a sheet supply unit 20, an image forming unit 30, and a second discharge roller 84 as a discharge roller. In this embodiment, the left side of Figure 1 is referred to as "front," and the right side as "rear." The top of Figure 1 is referred to as "up," and the bottom of Figure 1 is referred to as "down." The front of the page in Figure 1 is referred to as "right," and the back of the page in Figure 1 is referred to as "left."

[0043] The housing 10 has an opening 10A at its front. The front cover 11 opens and closes the opening 10A. Specifically, the front cover 11 is rotatable relative to the housing 10 between a closed position shown by a solid line and an open position shown by a dashed line. The closed position is the position in which the opening 10A is closed, and the open position is the position in which the opening 10A is opened.

[0044] The display unit 14 is a liquid crystal display and is mounted on the housing 10. It also displays various information to the user based on image signals acquired from the ASIC 92.

[0045] The sheet supply unit 20 comprises a sheet tray 21 and a sheet supply mechanism 22. Sheets S are set in the sheet tray 21. The sheet supply mechanism 22 is a mechanism that supplies sheets S to the photosensitive drums 50 (50Y, 50M, 50C, 50K) of the image forming unit 30, which will be described later, by receiving a driving force. The sheet supply mechanism 22 comprises a pickup roller 23, a separation roller 24, a separation pad 25, a transport roller 26, and a registration roller 27.

[0046] The sheet supply mechanism 22 feeds the sheet S from the sheet tray 21 using the pickup roller 23. Next, the sheet supply mechanism 22 separates the sheet S into individual sheets between the separation roller 24 and the separation pad 25. After that, the sheet supply mechanism 22 supplies the sheet S toward the image forming unit 30 using the transport roller 26 and the registration roller 27.

[0047] The image forming unit 30 comprises an exposure unit 40, four photosensitive drums 50, four developing cartridges 60, a transfer unit 70, and a fuser 80. The exposure unit 40 includes, for example, a light source, a deflector, a lens, and a mirror. The exposure unit 40 emits a light beam, indicated by a dashed line, to expose the surface of the photoreceptor drum 50.

[0048] The photoconductor drum 50 includes a photoconductor drum 50Y corresponding to yellow, a photoconductor drum 50M corresponding to magenta, a photoconductor drum 50C corresponding to cyan, and a photoconductor drum 50K corresponding to black. The four photoconductor drums 50 are arranged in the order of photoconductor drum 50Y, photoconductor drum 50M, photoconductor drum 50C, and photoconductor drum 50K from upstream to downstream in the transport direction of the sheet S.

[0049] Specifically, the photoreceptor drum 50Y is positioned upstream of the photoreceptor drum 50M in the conveying direction of the sheet S. The photoreceptor drum 50M is positioned upstream of the photoreceptor drum 50C in the conveying direction of the sheet S. The photoreceptor drum 50C is positioned upstream of the photoreceptor drum 50K in the conveying direction of the sheet S.

[0050] In this specification and the drawings, for components corresponding to each color, the designation Y, M, C, or K is added to the designation when the colors are distinguished, and Y, M, C, or K is omitted when the colors are not distinguished.

[0051] The image forming apparatus 1 further includes a drawer 55. The drawer 55 is movable in a direction in which the photoreceptor drum 50 is aligned between an inner position and an outer position, through an opening 10A of the housing 10, which is exposed when the front cover 11 is opened. The inner position is the position in which the drawer 55 is housed within the housing 10, and the outer position is the position in which at least a portion of the drawer 55 is exposed outside the housing 10. In this embodiment, the outer position is the position in which the drawer 55 is pulled forward from the inner position. In this embodiment, the drawer 55 is also detachable from the housing 10.

[0052] The drawer 55 has a frame 55F. The frame 55F rotatably supports four photoreceptor drums 50 (50Y, 50M, 50C, 50K). The frame 55F also supports four chargers 52. The chargers 52 charge the surface of the corresponding photoreceptor drums 50.

[0053] The developing cartridge 60 has a toner storage section 63 for storing toner, and includes a developing cartridge 60Y having a toner storage section 63Y for storing yellow toner, a developing cartridge 60M having a toner storage section 63M for storing magenta toner, a developing cartridge 60C having a toner storage section 63C for storing cyan toner, and a developing cartridge 60K having a toner storage section 63K for storing black toner. The developing cartridge 60Y has a developing roller 61Y that supplies yellow toner to the photoconductor drum 50Y. The developing cartridge 60M has a developing roller 61M that supplies magenta toner to the photoconductor drum 50M. The developing cartridge 60C has a developing roller 61C that supplies cyan toner to the photoconductor drum 50C. The developing cartridge 60K has a developing roller 61K that supplies black toner to the photoconductor drum 50K.

[0054] The developing roller 61Y is movable relative to the photoreceptor drum 50Y between a contact position in contact with the photoreceptor drum 50Y and a separated position away from the photoreceptor drum 50Y. The developing roller 61M is movable relative to the photoreceptor drum 50M between a contact position in contact with the photoreceptor drum 50M and a separated position away from the photoreceptor drum 50M. The developing roller 61C is movable relative to the photoreceptor drum 50C between a contact position in contact with the photoreceptor drum 50C and a separated position away from the photoreceptor drum 50C. The developing roller 61K is movable relative to the photoreceptor drum 50K between a contact position in contact with the photoreceptor drum 50K and a separated position away from the photoreceptor drum 50K.

[0055] The frame 55F of the drawer 55 detachably supports the developing cartridges 60 (60Y, 60M, 60C, 60K). Each developing cartridge 60 can be replaced either when the drawer 55 is in its external position or when the drawer 55 is removed from the housing 10.

[0056] The developing cartridge 60 is supported by the frame 55F so as to be movable back and forth between a first position shown by a solid line and a second position shown by a dashed line. The first position is the position in which the corresponding developing roller 61 is in contact, and the second position is the position in which the corresponding developing roller 61 is in a separated position.

[0057] Specifically, the developing cartridge 60Y is movable relative to the photoreceptor drum 50Y between a first position in which the developing roller 61Y is in contact with the photoreceptor drum 50Y and a second position in which the developing roller 61Y is in a position away from the photoreceptor drum 50Y. In other words, the developing cartridge 60Y is movable relative to the photoreceptor drum 50Y between a first position in which the developing roller 61Y is in contact with the photoreceptor drum 50Y and a second position in which the developing roller 61Y is away from the photoreceptor drum 50Y.

[0058] Furthermore, the developing cartridge 60M is movable relative to the photoreceptor drum 50M between a first position in which the developing roller 61M is in contact with the photoreceptor drum 50M and a second position in which the developing roller 61M is in a position away from the photoreceptor drum 50M. In other words, the developing cartridge 60M is movable relative to the photoreceptor drum 50M between a first position in which the developing roller 61M is in contact with the photoreceptor drum 50M and a second position in which the developing roller 61M is away from the photoreceptor drum 50M.

[0059] Furthermore, the developing cartridge 60C is movable relative to the photoreceptor drum 50C between a first position in which the developing roller 61C is in contact with the photoreceptor drum 50C and a second position in which the developing roller 61C is in a position away from the photoreceptor drum 50C. In other words, the developing cartridge 60C is movable relative to the photoreceptor drum 50C between a first position in which the developing roller 61C is in contact with the photoreceptor drum 50C and a second position in which the developing roller 61C is away from the photoreceptor drum 50C.

[0060] Furthermore, the developing cartridge 60K is movable relative to the photoreceptor drum 50K between a first position in which the developing roller 61K is in contact with the photoreceptor drum 50K and a second position in which the developing roller 61K is in a position away from the photoreceptor drum 50K. In other words, the developing cartridge 60K is movable relative to the photoreceptor drum 50K between a first position in which the developing roller 61K is in contact with the photoreceptor drum 50K and a second position in which the developing roller 61K is away from the photoreceptor drum 50K.

[0061] Furthermore, each developing cartridge 60 is equipped with a toner IC 62. The toner IC 62 is a non-volatile memory unit that can be rewritten, and stores information such as toner adhesion information and identification information of the developing cartridge 60. Note that the toner IC 62 is just one example of a memory unit.

[0062] The transfer unit 70 comprises a drive roller 71, a driven roller 72, an endless conveyor belt 73, and four transfer rollers 74. The conveyor belt 73 is stretched between the drive roller 71 and the driven roller 72, with its outer surface in contact with the four photoreceptor drums 50. The transfer rollers 74 are positioned inside the conveyor belt 73, sandwiching the conveyor belt 73 between them and the corresponding photoreceptor drums 50.

[0063] The fuser 80 is an example of a fixing device, and is a device that heat-fixes the toner image transferred to the sheet S to the sheet S. The fuser 80 has a heating unit 81, a pressurizing unit 82, and a first discharge roller 83 as a discharge roller. The heating unit 81 is an example of a heating rotating body, and includes a heating roller 81A and a heater 81B. The heating roller 81A is a cylindrical roller made of metal. The heater 81B is a heater that heats the heating roller 81A and is positioned to pass inside the heating roller 81A.

[0064] The pressurizing section 82 is an example of a pressurizing rotating body, and presses the sheet S against the heating section 81. Specifically, the pressurizing section 82 is a pressurizing roller that sandwiches the sheet S between itself and the heating roller 81A. The pressurizing roller is a roller in which a rubber layer is covered around a core metal. The fuser 80, upon receiving a driving force, conveys the sheet S between the heating roller 81A of the heating section 81 and the pressurizing section 82 (pressurizing roller). The fuser 80 also conveys the sheet S by the first discharge roller 83 upon receiving a driving force.

[0065] The image forming unit 30 uniformly charges the surface of the photoreceptor drum 50 with the charger 52, and then exposes it with a light beam irradiated from the exposure unit 40. This causes the image forming unit 30 to form an electrostatic latent image on the photoreceptor drum 50 based on the image data. The image forming unit 30 also supplies toner contained in the developing cartridge 60 to the photoreceptor drum 50 from the developing roller 61 located at the contact position. This causes the image forming unit 30 to form a toner image on the photoreceptor drum 50.

[0066] The image forming unit 30 transfers the toner image formed on the photoreceptor drum 50 to the sheet S by transporting the sheet S supplied from the sheet supply unit 20 between the photoreceptor drum 50 and the transfer roller 74. Subsequently, the image forming unit 30 fixes the toner image to the sheet S by transporting the sheet S, on which the toner image has been transferred, between the heating roller 81A and the pressurizing unit 82.

[0067] The first discharge roller 83 and the second discharge roller 84, upon receiving a driving force, discharge the sheet S from between the heating section 81 and the pressurizing section 82 to the outside of the housing 10. Specifically, the first discharge roller 83 and the second discharge roller 84 discharge the sheet S on which the toner image has been fixed to the discharge tray 13.

[0068] Figure 2 is a block diagram showing the configuration of the image forming apparatus according to this embodiment. The main board 91 is connected to the main motor M1, the process motor M2, the high-voltage power supply board 51, and the display unit 14.

[0069] First, the main board 91 is a control board that controls the entire image forming apparatus, and includes an ASIC 92, a RAM 93 used as working memory for the ASIC 92 to perform various calculations, an NVRAM 94 in which control programs and the like are stored, a main motor drive circuit 101, and a process motor drive circuit 102. Note that the ASIC 92 is an example of a control unit.

[0070] The main motor drive circuit 101 is connected to the ASIC 92 and the main motor M1. The main motor drive circuit 101 controls the rotational speed and rotational direction of the main motor M1 based on instructions from the ASIC 92.

[0071] The process motor drive circuit 102 is connected to the ASIC 92 and the process motor M2. The process motor drive circuit 102 controls the rotational speed and direction of the process motor M2 based on instructions from the ASIC 92. Further details will be described later.

[0072] The high-voltage power supply board 51 applies a voltage to the charger 52 to charge the photoreceptor drum. It is also possible to apply a voltage to the developing roller 61.

[0073] The main motor M1 is connected to transmit driving force to the developing separation gear train GT1, the fixing drive gear train GT2, the nip pressure adjustment gear train GT3, and the sheet supply gear train GT4. It is also the motor that drives the separation cam of the contact separation mechanism 5, the fuser 80, the nip pressure adjustment mechanism 200, and the sheet supply mechanism 22 via each gear train. The main motor M1 can rotate in both forward and reverse directions, and rotates in the forward direction when transporting the sheet S from the sheet tray 21 towards the discharge tray 13 in order to form an image on the sheet S.

[0074] The process motor M2 is connected to transmit driving force to the drum drive gear train GT5 and the developer drive gear train GT6. It is also the motor that drives the photoreceptor drum 50, the developer roller 61, and the transfer unit 70 via each gear train.

[0075] The developing and separating gear train GT1 is a gear train that transmits the driving force of the main motor M1 to the separating cam 150 of the contact separating mechanism 5. The developing and separating gear train GT1 also includes electromagnetic clutches EC1 and EC2. Electromagnetic clutch EC1 is configured to be located between the main motor and the separating cams 150Y, 150M, and 150C. Electromagnetic clutch EC2 is configured to be located between the main motor and the separating cam 150K.

[0076] The fixing drive gear train GT2 is a gear train that receives the driving force of the main motor M1 via the developing separation gear train GT1 and transmits it to the fixing unit 80. Specifically, the fixing drive gear train GT2 receives the driving force of the main motor M1 from the developing separation gear train GT1 and transmits it to the heating roller 81A.

[0077] The nip pressure adjustment gear train GT3 is a gear train that receives the driving force of the main motor from the developing separation gear train GT1 and transmits it to the nip pressure adjustment mechanism 200. The seat supply gear train GT4 is a gear train that transmits the driving force of the main motor M1 to the seat supply mechanism 22. The drum drive gear train GT5 is a gear train that transmits the driving force of the process motor M2 to the photoreceptor drum 50 and the drive roller 71.

[0078] The developing drive gear train GT6 is a drive transmission mechanism that transmits the driving force of the process motor M2 to the developing roller 61. Further details will be described later.

[0079] The electromagnetic clutch EC1 can be switched between a transmission state and a disconnection state. For example, the electromagnetic clutch EC1 is in the transmission state when energized and in the disconnection state when not energized. In the transmission state, the driving force from the main motor M1 is transmitted to the separation cams 150Y, 150M, and 150C. In the disconnection state, the driving force from the main motor M1 is not transmitted to the separation cams 150Y, 150M, and 150C. The electromagnetic clutch EC1 is controlled by the ASIC92.

[0080] The electromagnetic clutch EC2 can be switched between a transmission state and a disconnection state. For example, the electromagnetic clutch EC2 is in a transmission state when energized and in a disconnection state when not energized. In the transmission state, the driving force from the main motor M1 is transmitted to the separation cam 150K. In the disconnection state, the driving force from the main motor M1 is not transmitted to the separation cam 150K. The electromagnetic clutch EC2 is controlled by ASIC92.

[0081] The contact-separation mechanism 5 is a mechanism that moves the developing roller 61 between a contact position and a separated position by receiving driving force from the main motor M1. The contact-separation mechanism 5 comprises four separation cams 150 and a structure that moves the developing roller 61 by the rotation of the separation cams 150. The separation cams 150 include separation cam 150Y, separation cam 150M, separation cam 150C, and separation cam 150K.

[0082] The separation cam 150Y rotates by receiving driving force from the main motor M1, moving the developing roller 61Y between a contact position and a separation position. Specifically, the separation cam 150Y rotates, moving the developing cartridge 60Y between a first position and a second position, thereby moving the developing roller 61Y between a contact position and a separation position. The separation cam 150M rotates by receiving driving force from the main motor M1, moving the developing roller 61M between a contact position and a separation position. Specifically, the separation cam 150M rotates, moving the developing cartridge 60M between a first position and a second position, thereby moving the developing roller 61M between a contact position and a separation position.

[0083] The separation cam 150C rotates by receiving driving force from the main motor M1, moving the developing roller 61C between a contact position and a separation position. Specifically, the separation cam 150C rotates, moving the developing cartridge 60C between a first position and a second position, thereby moving the developing roller 61C between a contact position and a separation position. The separation cam 150K rotates by receiving driving force from the main motor M1, moving the developing roller 61K between a contact position and a separation position. Specifically, the separation cam 150K rotates, moving the developing cartridge 60K between a first position and a second position, thereby moving the developing roller 61K between a contact position and a separation position.

[0084] The nip pressure adjustment mechanism 200 switches the nip pressure generated by the heating section 81 and pressurizing section 82 of the fuser 80 between a first nip pressure and a second nip pressure.

[0085] Figure 3 shows the separation cam 150 and a portion of the gear train of the developing drive gear train GT6, which is the drive transmission mechanism. Figure 3 shows the gear train when viewed from right to left in the image forming apparatus 1. First, the separation cam 150Y (cam gear 115Y), separation cam 150M (cam gear 115M), separation cam 150C (cam gear 115C), separation cam 150K (cam gear 115K), idler gear 118, and gear 116 are a portion of the gear train of the developing separation gear train GT1.

[0086] The separation cam 150C (cam gear 115C) meshes with the separation cam 150M (cam gear 115M) via gear 116, and the separation cam 150M (cam gear 115M) meshes with the separation cam 150Y (cam gear 115Y) via idler gear 118. In addition, the separation cam 150C (cam gear 115C) can transmit the driving force of the main motor M1 to the developing cartridges 60Y, 60M, and 60C via the electromagnetic clutch EC1. As a result, when the electromagnetic clutch EC1 is in the transmission state, the separation cams 150Y (cam gear 115Y), 150M (cam gear 115M), and 150C (cam gear 115C) move the developing cartridges 60Y, 60M, and 60C between the contact position and the separation position in conjunction. When the main motor M1 rotates in the forward direction, it moves from the separated position to the contact position, and when the main motor M1 rotates in the reverse direction, it moves from the contact position to the separated position. In addition, when the electromagnetic clutch EC1 is disengaged, it maintains either the contact position or the separated position.

[0087] The separation cam 150K (cam gear 115K) can transmit the driving force of the main motor M1 to the developing cartridge 60K via the electromagnetic clutch EC2. As a result, when the electromagnetic clutch EC2 is in the transmission state, the separation cam 150K (cam gear 115K) moves the developing cartridge 60K between the contact position and the separation position. When the main motor M1 rotates forward, it moves from the separation position to the contact position; when the main motor M1 rotates backward, it moves from the contact position to the separation position. Furthermore, when the electromagnetic clutch EC2 is disengaged, either the contact position or the separation position is maintained.

[0088] According to the development separation gear train GT1 described above, the driving force of the main motor M1 can be controlled by electromagnetic clutches EC1 and EC2 to either transmit or disconnect the force. In the transmission state, the contact separation mechanism 5 can move the development rollers 61 (61Y, 61M, 61C, 61K) to a contact position or a separation position where they are in contact with the photoreceptor drum 50 (50Y, 50M, 50C, 50K). Furthermore, by disengaging only electromagnetic clutch EC1, it is possible to move only the development roller 61K to a contact position or a separation position where they are in contact with the photoreceptor drum 50K.

[0089] The developing drive gear train GT6 includes gear 421, gear 422, gear 423, moving gear 424, first output gear 425, coupling gear 426Y, coupling gear 426M, gear 427, coupling gear 426C, gear 431, gear 432, gear 433, gear 434, gear 435, first gear 436, planetary gear mechanism 180, coupling gear 426K as the second gear, and a switching cam.

[0090] Gear 421 is a two-stage gear having a large-diameter gear and a small-diameter gear, with the large-diameter gear meshing with the motor gear MG2. The motor gear MG2 is located in the front-rear direction between the rotation center of the coupling gear 426M and the rotation center of the coupling gear 426C. Gear 422 meshes with the smaller diameter gear of gear 421. Gear 423 is meshed with gear 422.

[0091] The moving gear 424 is a gear that receives driving force from the process motor M2 and meshes with gear 423. The moving gear 424 is movable relative to the first output gear 425 between a first transmission position shown by a solid line and a first disconnection position shown by a dashed line. Specifically, the moving gear 424 is supported so as to be able to swing around gear 423 between the first transmission position and the first disconnection position.

[0092] The first transmission position is the position where the first output gear 425 engages, and the driving force of the process motor M2 is output towards the developing rollers 61Y, 61M, and 61C. The first cutting position is the position where the first output gear 425 does not engage, and the driving force of the process motor M2 is not output towards the developing rollers 61Y, 61M, and 61C. The moving gear 424 is biased by a spring from the first cutting position towards the first transmission position. The moving gear 424 moves between the first transmission position and the first cutting position by a switching cam (not shown).

[0093] The first output gear 425 is a gear that outputs driving force towards the developing rollers 61Y, 61M, and 61C. The first output gear 425 is a two-stage gear having a large diameter gear and a small diameter gear, with the large diameter gear meshing with the moving gear 424, which is located in the first transmission position.

[0094] The coupling gear 426Y meshes with the small-diameter gear of the first output gear 425. The coupling gear 426Y is the gear that outputs the driving force from the process motor M2 toward the developing roller 61Y. Specifically, the coupling gear 426Y outputs the driving force from the process motor M2 toward the developing cartridge 60Y.

[0095] The coupling gear 426M meshes with the small-diameter gear of the first output gear 425. The coupling gear 426M is the gear that outputs the driving force from the process motor M2 toward the developing roller 61M. Specifically, the coupling gear 426M outputs the driving force from the process motor M2 toward the developing cartridge 60M. Gear 427 meshes with coupling gear 426M.

[0096] The coupling gear 426C meshes with gear 427. The coupling gear 426C is a gear that outputs the driving force from the process motor M2 towards the developing roller 61C. Specifically, the coupling gear 426C outputs the driving force from the process motor M2 to the developing cartridge 60C.

[0097] Furthermore, gear 431 meshes with gear 422. Gear 432 meshes with gear 431. Gear 433 is meshed with gear 432. Gear 434 meshes with gear 433. Gear 434 rotates coaxially with coupling gear 426C. Gear 435 meshes with gear 434.

[0098] The first gear 436 is a gear that receives driving force from the process motor M2 and meshes with gear 435. The first gear 436 meshes with the planetary gear mechanism 180. The first gear 436 rotates coaxially with the coupling gear 426K.

[0099] The planetary gear mechanism 180 meshes with the coupling gear 426K, and when the rotation of the internal gear is stopped, the first gear 436 outputs the driving force of the process motor M2 toward the developing roller 61K. On the other hand, when the rotation of the internal gear is not stopped, the driving force of the process motor M2 transmitted from the first gear 436 does not rotate the coupling gear 426K and does not output the driving force toward the developing roller 61K.

[0100] The separation cam 150K (cam gear 115K) corresponding to the black gear has a projection 154 protruding from its outer surface. The projection 154 is also capable of contacting the selector lever 160. The projection 154 contacts the arm 160A of the selector lever 160 in accordance with the rotation of the separation cam 150K, thereby causing the selector lever 160 to rotate. Furthermore, in addition to the arm 160A that contacts the projection 154, the selector lever 160 has an arm 160B that contacts the internal gear of the planetary gear mechanism 180. By contacting the internal gear of the planetary gear mechanism 180, the arm 160B makes it impossible for the internal gear to rotate. On the other hand, by not contacting the internal gear of the planetary gear mechanism 180, the arm 160B enables the internal gear to rotate.

[0101] Furthermore, the separation cam 150K (cam gear 115K) rotates in response to the rotation of the main motor M1 in order to move the developing cartridge 60K from the contact position to the separation position, and the projection 154 makes contact with the arm 160A of the switching lever 160. In other words, in conjunction with the contact separation mechanism 5 moving the developing cartridge 60K from the contact position to the separation position by the driving force of the main motor M1, the switching lever 160 does not come into contact with the internal gear of the planetary gear mechanism 180, the driving force of the process motor M2 does not rotate the coupling gear 426K, and does not output driving force toward the developing roller 61K.

[0102] The switching cam (not shown) is a plate cam that rotates by receiving driving force from the main motor M1. The structure for transitioning gears between contact and non-contact states using the switching cam is known technology and will not be explained in detail, but the switching cam rotates by receiving driving force from the main motor M1 via the cam gear 115M, and moves the moving gear 424 of the developing drive gear train GT6 relative to the first output gear 425 between the first transmission position shown by the solid line and the first disconnection position shown by the dashed line. When the main motor M1 rotates forward, the switching cam moves the moving gear 424 from the first disconnection position to the first transmission position. Also, when the main motor M1 rotates backward, the switching cam moves the moving gear 424 from the first transmission position to the first disconnection position.

[0103] According to the development drive gear train GT6, which is the drive transmission mechanism described above, when the development rollers 61 (61Y, 61M, 61C, 61K) are separated from the photoreceptor drum 50 (50Y, 50M, 50C, 50K) by the development separation gear train GT1, the driving force from the process motor M2 is not transmitted to the development rollers 61 (61Y, 61M, 61C, 61K). On the other hand, when they are in contact, the driving force from the process motor M2 is transmitted to the development rollers 61 (61Y, 61M, 61C, 61K). Furthermore, when only the electromagnetic clutch EC1 is disengaged, and only the development roller 61K is in contact with the photoreceptor drum 50K, the driving force from the process motor M2 is transmitted only to the development roller 61K.

[0104] As shown in Figure 4, the process motor M2 is a three-phase brushless motor, and the stator has three-phase (U, V, W) drive coils M2C, and Hall elements M2U, M2V, M2W, and an FG sensor M2S for detecting the rotational position of the rotor.

[0105] The FG sensor M2S is configured to generate an induced electromotive force in the FG sensor as the rotor of the brushless motor rotates. The FG sensor M2S outputs an AC signal (FG signal) with a frequency corresponding to the rotor's rotation speed. When the brushless motor rotates at a high speed, the frequency of the FG signal increases, and when the rotation speed is slow, the frequency decreases.

[0106] The ASIC92 detects the rotational speed of the three-phase brushless motor based on the FG signal input via the process motor drive circuit 102. Based on the FG signal output from the FG sensor M2S, the ASIC92 performs feedback control and modifies the pulse width (duty cycle) PWM signal, which is the control signal, through feedback control before outputting it to the motor drive circuit. The process motor drive circuit 102 controls the amount of current supplied to the three-phase drive coil M2C according to the duty cycle of the input PWM signal, and also switches the timing of the current supply to the three-phase drive coil M2C based on the Hall signals input from Hall elements M2U, M2V, and M2W, thereby switching the direction of the magnetic field created by the three-phase drive coil M2C and rotating the rotor.

[0107] Furthermore, the main motor M1 is also a 3-phase brushless motor, and its rotation is controlled by the ASIC92 using a similar configuration. The motor drive circuit uses the main motor drive circuit 101, as shown in Figure 2.

[0108] In the image forming apparatus 1 having the above configuration, the charging of each part during the toner adhesion determination process will be explained with reference to Figure 5. The high-voltage power supply board 51 is configured to apply voltage to the charger 52 and the developing roller 61. Furthermore, the high-voltage power supply board 51 can apply voltage whether the developing roller 61 is in a separated position or in a contact position.

[0109] At the separated position, the high-voltage power supply board 51 applies a positive first voltage to the charger 52. Furthermore, the ASIC 92 rotates the process motor M2, which in turn rotates the photoreceptor drum 50 and the drive roller 71 via the drum drive gear train GT5. The charger 52 positively charges the surface of the photoreceptor drum 50 based on the positive first voltage applied from the high-voltage power supply board 51. In addition, as the photoreceptor drum 50 rotates, the entire surface of the photoreceptor drum 50 is uniformly positively charged. Here, the toner contained in the developing cartridge 60 is positively charged toner, and the surface of the photoreceptor drum 50 is at a higher voltage than the developing roller 61.

[0110] Here, when charging the photoreceptor drum 50, the photoreceptor drum 50 is rotated for at least one full rotation. The ASIC 92 moves the developing roller 61 from the separated position to the contact position when the rotational speed of the process motor M2 reaches a predetermined rotational speed or higher, which is necessary to rotate the photoreceptor drum 50 for at least one full rotation. This allows the photoreceptor drum 50 to be charged at a predetermined rotational speed, regardless of the torque of the photoreceptor drum 50, and to be charged uniformly and completely across its entire surface. The predetermined rotational speed of the process motor M2 necessary to rotate the photoreceptor drum 50 for at least one full rotation may be stored in the NVRAM 94 in advance, based on the gear ratio of the drum drive gear train GT5, etc.

[0111] As a result, as shown in Figure 6, when the developing roller 61 is moved from a separated position to a contact position, the positively charged toner that has moved to the surface of the developing roller 61 will not move from the developing roller 61 to the photoreceptor drum 50, and the positively charged toner will not move to the surface of the photoreceptor drum 50 due to the potential difference. On the other hand, if the entire surface of the photoreceptor drum 50 is not uniformly positively charged, the toner will unintentionally move to the photoreceptor drum 50.

[0112] Furthermore, the high-voltage power supply board 51 may also apply a developing voltage to the developing roller 61 in addition to the charger 52. When a positive second voltage is applied to the charger 52 and the developing roller 61 is in a separated position, the high-voltage power supply board 51 applies different positive voltages to the developing roller 61 and the charger 52. The voltage is such that the voltage on the surface of the photoreceptor drum 50 is higher than that on the developing roller 61.

[0113] As a result, when the developing roller 61 is moved from a separated position to a contact position, the positively charged toner that has moved to the surface of the developing roller 61 will not move from the developing roller 61 to the photoreceptor drum 50, and the positively charged toner will not move to the surface of the photoreceptor drum 50 due to the potential difference.

[0114] Furthermore, the high-voltage power supply board 51 may also apply a negative third voltage, and in the separated position, the high-voltage power supply board 51 applies a negative third voltage to the charger 52. In addition, the ASIC 92 rotates the process motor M2, thereby rotating the photoreceptor drum 50 and the drive roller 71 via the drum drive gear train GT5. The charger 52 negatively charges the surface of the photoreceptor drum 50 based on the negative third voltage applied from the high-voltage power supply board 51. Also, as the photoreceptor drum 50 rotates, the entire surface of the photoreceptor drum 50 is uniformly negatively charged. Here, the toner contained in the developing cartridge 60 is negatively charged toner that is negatively charged, and the surface of the photoreceptor drum 50 is in a state where the voltage is lower than that of the developing roller 61.

[0115] As a result, when the developing roller 61 is moved from a separated position to a contact position, the negatively charged toner that has moved to the surface of the developing roller 61 will not move from the developing roller 61 to the photoreceptor drum 50, and the negatively charged toner will not move to the surface of the photoreceptor drum 50 due to the potential difference.

[0116] Next, the toner adhesion determination process will be explained based on Figure 7. First, each step will be abbreviated as S below. In S1, the ASIC92 determines the manufacturer of the process motor M2. Specifically, based on the FG signal and Hall signal input to the ASIC92 via the process motor drive circuit 102 from the Hall elements M2U, M2V, M2W, and FG sensor M2S, the ASIC92 determines the manufacturer of the process motor M2 based on its characteristics. Alternatively, the manufacturer may be determined by reading the determination terminal provided on the process motor M2.

[0117] In S2, ASIC92 sets the upper limit of the pulse width for process motor M2. The NVRAM94 has pre-stored upper limits of pulse width predetermined for each manufacturer. Based on the manufacturer of process motor M2 determined in S1, ASIC92 sets the upper limit of pulse width stored in the NVRAM94 as the upper limit of the pulse width for process motor M2.

[0118] The upper limit of the pulse width is the upper limit at which the development drive gear train GT6, which is the drive transmission mechanism, is not damaged by the rotation of the process motor M2 when the ASIC92 outputs a control signal to increase the amount of current supplied to the three phases of the drive coil of the process motor M2.

[0119] In step S3, the ASIC92 drives the process motor M2. The high-voltage power supply board 51 applies a voltage to the charger 52, and the charger 52 positively charges the surface of the photoreceptor drum 50 based on the positive voltage applied from the high-voltage power supply board 51. As explained in Figure 5, the developing roller 61 is in a separated position.

[0120] In S4, the ASIC92 determines whether the rotational speed of the process motor M2 has reached a first predetermined rotational speed or higher, which is necessary to rotate the photoreceptor drum 50 at least once. The ASIC92 repeats this determination until the rotational speed of the process motor M2 reaches a first predetermined rotational speed or higher, and proceeds to S5 if it reaches the first predetermined rotational speed or higher. As described above, the photoreceptor drum 50 is charged at a predetermined rotational speed, and the entire surface is charged uniformly and without omission.

[0121] In S5, the ASIC92 moves the developing roller 61 from the separated position to the contact position. Specifically, the ASIC92 starts driving the main motor M1. Then, by energizing the electromagnetic clutches EC1 and EC2, it switches from the disconnected state to the transmission state, transmitting the driving force of the main motor M1 to the developing separation gear train GT1. As a result, the contact separation mechanism 5 moves the developing roller 61 from the separated position to the contact position using the driving force of the main motor M1. Along with the movement to the contact position, the developing drive gear train GT6, which is the drive transmission mechanism, moves the moving gear 424 from the first disconnected position to the first transmission position. Also, the switching lever 160 stops the rotation of the internal gear of the planetary gear mechanism 180. After a certain period of time has elapsed, the ASIC92 switches from the transmission state to the disconnected state by stopping the energization of the electromagnetic clutches EC1 and EC2, and stops driving the main motor M1.

[0122] In S6, ASIC92 drives the process motor M2 and measures the rotational speed of the process motor M2 based on the Hall signals input from Hall elements M2U, M2V, and M2W. Furthermore, it determines whether the process motor M2 has rotated at or above a second predetermined rotational speed. If the process motor M2 has not rotated at or above the second predetermined rotational speed, the process proceeds to S7; if the process motor M2 has rotated at or above the second predetermined rotational speed, the process proceeds to S9.

[0123] In S7, the ASIC92 determines whether the elapsed time since the start of driving the process motor M2 has exceeded a first predetermined time. Here, the first predetermined time is the time required for the process motor M2 to rotate at a second predetermined rotational speed when the toner in the developer cartridge 60 is not solidified, and the time insufficient for the process motor M2 to rotate at the second predetermined rotational speed when the toner in the developer cartridge 60 is solidified. For example, the first predetermined time and second predetermined rotational speed may differ depending on the manufacturer of the process motor M2 determined in S1. If the elapsed time since the start of driving the process motor M2 has exceeded the first predetermined time, the process proceeds to S8; otherwise, the process proceeds to S6.

[0124] In S8, the ASIC92 determines that the toner in the developer cartridge 60 has solidified. In other words, it determines that the process motor M2 cannot rotate at the second predetermined rotational speed within the first predetermined time due to the solidification of the toner in the developer cartridge 60.

[0125] In S9, the ASIC92 determines that the toner in the developer cartridge 60 is not solidified.

[0126] In S10, the ASIC92 stops driving the process motor M2. Also, the high-voltage power supply board 51 stops applying voltage to the charger 52.

[0127] In S11, the ASIC92 moves the developing roller 61 from the contact position to the separation position. Specifically, the ASIC92 starts driving the main motor M1. Then, by energizing the electromagnetic clutches EC1 and EC2, it switches from the disconnected state to the transmission state and transmits the driving force of the main motor M1 to the developing separation gear train GT1. As a result, the contact separation mechanism 5 moves the developing roller 61 from the contact position to the separation position using the driving force of the main motor M1. Along with the movement to the separation position, the developing drive gear train GT6, which is the drive transmission mechanism, moves the moving gear 424 from the first transmission position to the first disconnected position. Also, the switching lever 160 moves to a position where the rotation of the internal gear of the planetary gear mechanism 180 is not stopped. After a certain period of time has elapsed, the ASIC92 switches from the transmission state to the disconnected state by stopping the energization of the electromagnetic clutches EC1 and EC2, and stops driving the main motor M1.

[0128] Next, the motor failure detection will be explained based on Figure 7. First, in S21, the ASIC92 switches from a transmission state to a disconnected state by stopping the power supply to electromagnetic clutches EC1 and EC2, and stops the drive of the main motor M1. If the developing roller 61 is in the contact position, as previously explained, the developing roller 61 is moved from the contact position to the separated position, stopping the electromagnetic clutches EC1 and EC2 and stopping the drive of the main motor M1.

[0129] In S22, the ASIC92 drives the process motor M2. Here, since the developing rollers 61 are in a separated position, the driving force from the process motor M2 is not transmitted to the developing rollers 61 (61Y, 61M, 61C, 61K).

[0130] In S23, the ASIC92 determines whether the rotational speed of the process motor M2 reached the target speed within the second predetermined time. If the target speed was reached within the second predetermined time, the process proceeds to S24; otherwise, the process proceeds to S25.

[0131] In S24, ASIC92 determines that the process motor M2 is functioning normally. The process motor M2 is a three-phase brushless motor, and based on the FG signal output from the FG sensor M2S, ASIC92 performs feedback control, modifying the PWM signal (pulse width / duty cycle), which is the control signal, through feedback control to achieve the target rotational speed. Therefore, if the target rotational speed is reached, it is determined that the process motor M2 is operating normally.

[0132] In S25, ASIC92 determines that the process motor M2 is faulty. Similarly, if the target rotational speed is reached, it is determined that the process motor M2 is faulty.

[0133] Next, we will explain the usage patterns of the toner solidification detection process and motor failure detection described above. It should be noted that, beyond the explanations provided below, the toner solidification detection and motor failure detection can be performed at any desired time.

[0134] Firstly, Figure 9 is a flowchart showing the control of the image forming apparatus 1 during toner swapping, and the housing 10 is executed when the front cover 11 is opened and closed. First, in S31, the ASIC 92 determines whether a toner swap has been performed. In other words, it determines whether the developer cartridge 60 has been replaced. Specifically, it monitors whether there has been a change in the identification information by reading the toner IC 62 that each developer cartridge 60 has. If a developer cartridge 60 is installed, the process proceeds to S32, and if the developer cartridge 60 is not replaced, this control is terminated. The terms in parentheses will be explained later.

[0135] In S32, ASIC92 performs a motor failure check. The motor failure check is the same as already explained, so the explanation will be omitted. In S33, if the failure check performed in S32 determines that the process motor M2 is faulty, the process proceeds to S37; if the process motor M2 is determined to be normal, the process proceeds to S34.

[0136] In S34, the ASIC92 performs a toner adhesion determination process. The toner adhesion determination is the same as already explained, so the explanation will be omitted. In S35, if the toner adhesion determination process performed in S34 determines that the toner in the developer cartridge 60 is adhered, the process proceeds to S36. If it determines that the toner in the developer cartridge 60 is not adhered, this control is terminated.

[0137] According to this, the toner solidification detection process is executed after the motor failure detection process has been performed, and only if the process motor M2 is not determined to be faulty. This prevents the toner solidification detection process from incorrectly detecting toner solidification due to the process motor M2 being faulty, even if the rotation speed of the process motor M2 is set to a second predetermined rotation speed.

[0138] In S36, the display unit 14 displays an error image to inform the user of toner solidification. This notifies the user of toner solidification and prompts them to swap the toner. In S37, the display unit 14 displays an error image to inform the user of a motor failure. This notifies the user of toner buildup and prompts them to perform maintenance.

[0139] Here, S31 may determine whether the image forming apparatus 1 is new. Specifically, when the power supply to the image forming apparatus 1 is turned on, the ASIC92 determines whether it is the first time the image forming apparatus 1 is being started. The subsequent processing is the same as in Figure 9. In addition, as a method for determining whether it is the first time the image forming apparatus 1 is being started, the startup history in the NVRAM94 is set to empty at the time of shipment, and the startup history is stored in subsequent startups. As a result, the ASIC92 refers to the startup history stored in the NVRAM94 and determines that it is the first time the image forming apparatus 1 is being started if there is no startup history. With this, it is possible to determine whether toner has solidified due to temperature changes during transport or long-term storage before printing is performed.

[0140] Secondly, Figure 10 is a flowchart showing the control of the image forming apparatus 1 in the mode for determining solid coloring. First, in S41, the ASIC 92 determines, similar to the flowchart in Figure 9, whether the developing cartridge 60 has been replaced or whether it is the first startup of the image forming apparatus 1. If affirmative, proceed to S42; otherwise, terminate this control.

[0141] In S42, the ASIC92 determines whether toner fixation information is stored in the toner IC62 of the developing cartridge 60. Toner fixation information is a history of toner fixation that is stored in the toner IC62, which is the storage unit, when toner fixation is determined by the toner fixation determination process. If it is determined that fixation information is stored, the process proceeds to S52; if it is determined that fixation information is not stored, the process proceeds to S43.

[0142] In S43, ASIC92 sets the value of variable N to 1. Variable N can be an integer between 1 and 4. Also in S43, although not shown in this flowchart, motor failure detection may be performed. In S44, the display unit 14 displays an instruction to install only the developing cartridge 60 corresponding to the value of variable N. This allows the user to install and remove the developing cartridges 60 in a manner that ensures only the specified developing cartridge 60 is installed. Note that N=1 corresponds to developing cartridge 60Y, N=2 to developing cartridge 60M, N=3 to developing cartridge 60C, and N=4 to developing cartridge 60K.

[0143] In step S45, the ASIC92 performs toner adhesion detection processing. The toner adhesion detection processing is performed with one of the four developing cartridges installed, and the presence or absence of toner adhesion in that one developing cartridge is determined. In S46, if the toner solidification determination process in S45 determines that the toner in the developing cartridge 60 is solidified, the process proceeds to S47. If it determines that the toner in the developing cartridge 60 is not solidified, the process proceeds to S48.

[0144] In S47, the ASIC92 performs a toner fixation information storage process to store toner fixation information in the toner IC62 of the developer cartridge 60 that the toner fixation determination process in S45 determined to have toner fixed. As a result, individual toner fixation information is stored in the toner IC62 of the developer cartridge 60. In S48, the display unit 14 displays an error image to inform the user that the developing cartridge 60 has solidified toner.

[0145] In S49, the display unit 14 displays an image instructing the removal of the developing cartridge 60, which the toner fixation determination process in S45 determined to have no toner fixation on it.

[0146] In S50, the ASIC92 determines whether the value of variable N is 4. If the determination is negative, the process proceeds to S51. If the determination in S51 is positive, i.e., N=4, it means that the toner adhesion determination process was performed individually on all four developing cartridges 60 (60Y, 60M, 60C, 60K) and no toner adhesion was detected. In S51, the ASIC92 increments the value of variable N by 1. Then, the process proceeds to S44, where the display unit 14 displays an instruction to install a developing cartridge different from the one that has already undergone the toner adhesion determination process. This allows the ASIC92 to sequentially execute the toner adhesion determination process with one developing cartridge installed.

[0147] In S52, the display unit 14 indicates that a developer cartridge 60 containing toner solidification information is installed. In other words, if toner solidification information is stored in the toner IC 62 of the developer cartridge 60 in S42, the ASIC 92 does not perform the toner solidification determination process.

[0148] Based on the above, when a toner solidification detection process is performed with one developing cartridge 60 installed, it is possible to identify the developing cartridge 60 on which the toner has solidified if toner solidification is detected. Furthermore, by storing and detecting toner solidification information, unintended duplicate toner solidification detection processes can be eliminated.

[0149] Thirdly, Figure 11 is a flowchart showing the control of the image forming apparatus 1 in the mode for determining whether monochrome printing is possible. Here, steps S71 to S76 are the same as steps S31 to S35 and S37 in Figure 9, so their explanation is omitted.

[0150] In S77, the display unit 14 displays an instruction to install only the 60K developer cartridge containing black toner. In S78, the ASIC92 performs toner solidification detection processing with only the 60K developer cartridge installed. That is, in S76, with all the 60 developer cartridges (60Y, 60M, 60C, 60K) installed, if toner solidification is detected during the toner solidification detection processing, it is determined whether the toner solidification is due to the 60K developer cartridge.

[0151] In S79, if the toner solidification determination process in S78 determines that the toner in the 60K developer cartridge is solidified, the process proceeds to S80. If the process determines that the toner in the 60K developer cartridge is not solidified, the process proceeds to S81.

[0152] In the S80, the display unit 14 displays an error message indicating that printing is not possible and an error image to inform the user of toner solidification. This notifies the user of toner solidification and prompts them to swap the toner. It may also indicate that at least the 60K developer cartridge containing the black toner is solidified.

[0153] In S81, the display unit 14 displays an error image to inform the user of toner solidification. It may also display that at least one of the following is toner solidification: developer cartridge 60Y, developer cartridge 60M, or developer cartridge 60C.

[0154] In S82, the ASIC92 is configured to enable monochrome printing using only black toner. Specifically, electromagnetic clutch EC1 is configured to be unable to switch from the disconnected state to the transmission state, while electromagnetic clutch EC2 is configured to be able to switch from the disconnected state to the transmission state. As a result, the developer cartridges 60Y, 60M, and 60C are positioned at a distance from each other and are configured not to receive the driving force from the process motor M2. The display unit 14 also displays an image to inform the user that monochrome printing is possible.

[0155] As described in detail above, according to the image forming apparatus 1 of this embodiment, the ASIC 92 rotates the photoreceptor drum 50 using the process motor M2 while the developing roller 61 is in a separated position and applies a voltage to the charger 52 using the high-voltage power supply board 51 (S3). Then, using the contact separation mechanism 5, the developing roller 61 is moved from the separated position to the contact position (S5). In this state, the ASIC 92 performs a toner adhesion determination process (S6, S7, S8, S9) that determines whether or not toner has adhered in the toner storage section based on the rotation of the process motor M2.

[0156] According to this, when the photoreceptor drum 50 and the developing roller 61 are separated, a potential difference is created between them in advance. This prevents toner from flowing from the developing roller 61 to the photoreceptor drum 50 even when the photoreceptor drum 50 and the developing roller 61 come into contact.

[0157] Furthermore, when the ASIC92 applies voltage to the charger 52 using the high-voltage power supply board 51 while the developing roller 61 is in a separated position (S3), after the process motor M2 reaches a first predetermined rotational speed or higher corresponding to more than one rotation of the photoreceptor drum 50 (S4), the ASIC92 uses the contact separation mechanism 5 to move the developing roller 61 from the separated position to the contact position (S5). According to this, a potential difference can be generated between the photoreceptor drum 50 and the developing roller 61 across the entire surface of the drum, thus eliminating any possibility of toner flowing from the developing roller 61 towards the photoreceptor drum 50.

[0158] Furthermore, when the ASIC92 determines toner adhesion based on the rotation of the process motor M2 with the developing roller 61 moved from the separated position to the contact position using the contact separation mechanism 5, if the rotation speed of the process motor M2 exceeds a second predetermined number of rotations within a first predetermined time (S6: YES), it does not determine toner adhesion (S9), and if the rotation speed of the process motor M2 does not exceed a second predetermined number of rotations within a first predetermined time (S7: YES), it determines toner adhesion (S8). According to this method, toner adhesion can be determined by monitoring the rotation speed of the process motor M2.

[0159] Furthermore, when the ASIC92 determines the manufacturer of the process motor M2 based on the signal from the process motor M2 (S1), and performs feedback control to change the pulse width of the control signal output to the motor drive circuit 102 according to the rotational speed of the process motor M2, it sets the upper limit of the pulse width of the control signal to the upper limit of the manufacturer stored in the NVRAM94 (S2).

[0160] According to this, by setting an upper limit on the pulse width of the control signal according to a value specific to the manufacturer of the process motor M2, the process motor M2 is not rotated excessively, thereby preventing damage to the developing drive gear train GT6.

[0161] Furthermore, the ASIC92 performs toner adhesion detection processing (S35, S46, S76, S79) when it is the first startup of the image forming apparatus 1 (S31, S41, S71) or when it detects that the developing cartridge 60 has been installed (S31, S41, S71).

[0162] According to this, even if the toner inside the image forming apparatus 1 or the developing cartridge 60 solidifies due to temperature changes during transport or long-term storage, it is possible to determine if the toner has solidified before printing.

[0163] Furthermore, the ASIC92 performs a toner adhesion determination process with one of the multiple developing cartridges 60 installed, and determines whether or not toner has adhered to that one developing cartridge (S46, S79).

[0164] According to this, the ASIC92 determines whether toner has adhered to one developer cartridge 60, and therefore it can determine whether toner has adhered to that particular developer cartridge 60. When the ASIC92 performs a toner solidification detection process with one of the multiple developing cartridges 60 installed (S46), if it does not determine that toner solidification has occurred (S46: NO), it displays on the display unit 14 an instruction to remove one of the developing cartridges 60 (S49) and an instruction to install a different developing cartridge 60 (S51, S44).

[0165] According to this, the ASIC92 can sequentially determine the toner adhesion of each developing cartridge 60, and can determine the adhesion of each toner.

[0166] Furthermore, if the ASIC92 determines that toner has solidified (S46:YES) after performing the toner solidification determination process with one developer cartridge 60 installed, it performs a toner solidification information storage process (S47) in which the toner IC62 of the developer cartridge 60 stores the toner solidification information.

[0167] According to this, the ASIC92 can store toner adhesion information in the toner IC62, thereby determining that toner has adhered to the developer cartridge 60 where toner has adhered.

[0168] Furthermore, if a new developer cartridge 60 is installed after the toner fixation information storage process (S47) (S41), the ASIC92 will execute the toner fixation determination process (S46) if the toner IC62 of the newly installed developer cartridge 60 does not store toner fixation information (S42: NO), but will not execute the toner fixation determination process if the toner IC62 of the installed developer cartridge 60 does store toner fixation information (S42: YES).

[0169] According to this, the ASIC92 can eliminate unintended duplicate toner adhesion detection processes by determining whether or not toner adhesion information is stored in the toner IC62.

[0170] Furthermore, if the ASIC92 determines that toner has solidified after performing the toner solidification detection process (S47: YES), it displays an instruction on the display unit 14 to install only the developer cartridge 60K containing black toner (S77). Subsequently, the toner solidification detection process is performed again with only the developer cartridge 60K containing black toner installed (S78). If the result does not determine that toner has solidified (S79: NO), the display unit 14 displays that monochrome printing is possible (S82). If it determines that toner has solidified (S79: YES), it displays an error message on the display unit 14 indicating that printing is not possible (S80).

[0171] According to this, even if toner solidifies in a developer cartridge 60 other than the one containing black toner (60K), monochrome printing can still be performed using the developer cartridge 60 containing black toner.

[0172] Furthermore, the ASIC92 rotates the process motor M2 with the developing roller 61 in a separated position (S22), determines whether the rotational speed of the process motor M2 reaches the target speed within a second predetermined time (S23), and executes a fault determination process (S25) which determines that the process motor M2 is faulty if the target speed is not reached within the second predetermined time (S23: NO). The toner adhesion determination process (S35, S46, S76) is executed after the execution of the fault determination process (S33, S43, S73) if the process motor M2 is not determined to be faulty.

[0173] According to this, the ASIC92 determines whether the process motor M2 is malfunctioning before determining whether toner has solidified, thus preventing false detection that the toner has solidified due to a malfunction in the process motor M2.

[0174] It should be noted that the present invention is not limited to the embodiments described above, and various improvements and modifications are possible without departing from the spirit of the invention. For example, although the above embodiment was described as a laser printer, it could also be a multifunction device with the same configuration, or a home or industrial printer.

[0175] Furthermore, in the above embodiment, the toner IC 62, which is an example of a memory unit in the developing cartridge 60, was described as storing the history of toner solidification as toner solidification information. However, the toner IC 62, which is an example of a memory unit, may also store an identification number for referencing the toner solidification history as toner solidification information. The toner solidification history may then be stored in the NVRAM 94, and the toner solidification history may be retrieved from the NVRAM 94 according to the identification number. [Explanation of symbols]

[0176] 1…Image forming apparatus, 5…Contact separation mechanism, 10…Housing, 10A…Opening, 11…Front cover (cover), 20…Sheet supply unit, 21…Sheet tray, 22…Sheet supply mechanism, 23…Pickup roller, 24…Separation roller, 25…Separation pad, 26…Transport roller, 27…Registration roller, 30…Image forming unit, 40…Exposure unit, 50, 50Y, 50M, 50C, 50K…Photoreceptor drum, 51…High voltage power supply board, 52…Charger, 55…Drawer, 55F…Frame, 60, 60Y, 60M, 60C, 60K…Developing cartridge, 61, 61Y, 61M, 61C, 61K…Developing roller, 62…Toner IC ( 63...Toner storage unit, 70...Transfer unit, 71...Drive roller, 72...Driven roller, 73...Conveyor belt, 74...Transfer roller, 80...Fuser (Fuser device), 81...Heating unit (Heating rotating body), 81A...Heating roller, 81B...Heater, 82...Pressurizing unit (Pressurizing rotating body), 83...First discharge roller, 91...Main board, 92...ASIC (Control unit), 94...NVRAM (Non-volatile memory), 101...Main motor drive circuit, 102...Process motor drive circuit (Motor drive circuit), 180...Planetary gear mechanism, GT6...Developing drive gear train (Drive transmission mechanism), M1...Main motor, M2...Process motor (3-phase brushless motor). M2C...Drive coil (3-phase drive coil), M2U, M2V, M2W...Hall element, M2S...FG sensor.

Claims

1. Photosensitive drum and A charger for charging the photosensitive drum, A developing cartridge having a toner storage section for storing toner and a developing roller for supplying the toner to the photoreceptor drum, A contact-separation mechanism moves the developing roller between a contact position in contact with the photoreceptor drum and a separation position away from the photoreceptor drum, A process motor for rotating the photosensitive drum and the developing roller, A drive transmission mechanism for transmitting the driving force from the process motor to the developing roller, wherein the drive transmission mechanism transmits the driving force from the process motor to the developing roller when the developing roller is in the contact position, and does not transmit the driving force from the process motor to the developing roller when the developing roller is in the separated position, A high-voltage power supply board that applies a voltage to the charger for charging the photoreceptor drum, It comprises a control unit and, The control unit, With the developing roller in the separated position, the process motor is used to rotate the photoreceptor drum while the voltage is applied to the charger using the high-voltage power supply board. Then, with the developing roller moved from the separated position to the contact position using the contact separation mechanism, a toner adhesion determination process is performed to determine whether or not toner has adhered in the toner storage section based on the rotation of the process motor. Image forming apparatus.

2. The control unit, When the voltage is applied to the charger using the high-voltage power supply board while the developing roller is in the separated position, after the process motor reaches a first predetermined rotational speed corresponding to more than one rotation of the photoreceptor drum, the developing roller is moved from the separated position to the contact position using the contact separation mechanism. The image forming apparatus according to claim 1.

3. The control unit, When determining toner adhesion based on the rotation of the process motor while the developing roller is moved from the separated position to the contact position using the contact separation mechanism, if the rotation speed of the process motor exceeds a second predetermined number of rotations within a first predetermined time, toner adhesion is not determined; however, if the rotation speed of the process motor does not exceed a second predetermined number of rotations within a first predetermined time, toner adhesion is determined. The image forming apparatus according to claim 1.

4. The aforementioned process motor is A three-phase brushless motor having three-phase drive coils, a Hall element for detecting the rotational position of the rotor, and an FG sensor that generates an induced electromotive force as the rotor rotates, Furthermore, The motor drive circuit includes a control signal input from the control unit that controls the amount of current supplied to the three-phase drive coils and switches the timing of supplying current to the three-phase drive coils, The control unit, When rotating the aforementioned process motor, The rotational speed of the process motor is detected based on the Hall signal from the Hall element input via the motor drive circuit. The rotational speed of the motor is detected based on the FG signal from the FG sensor, which is input via the motor drive circuit. The system performs feedback control to change the pulse width of the control signal output to the motor drive circuit according to the rotational speed. The image forming apparatus according to claim 1.

5. Furthermore, To prevent damage to the drive transmission mechanism due to the rotation of the process motor as the amount of current supplied to the drive coil of the process motor increases, the system includes a non-volatile memory in which a predetermined upper limit of the pulse width of the control signal is stored for each manufacturer of the process motor. The control unit, Based on the signal from the process motor, the manufacturer of the process motor is determined. When performing feedback control to change the pulse width of the control signal output to the motor drive circuit according to the rotation speed, the upper limit of the pulse width of the control signal is set to the upper limit of the manufacturer stored in the non-volatile memory. The image forming apparatus according to claim 4.

6. Furthermore, A fixing device for thermally fixing a toner image formed on a sheet by the photoreceptor drum, comprising: a heating rotating body having a heater; and a pressing rotating body that presses the sheet against the heating rotating body; The fixing device comprises a main motor for rotating the rotating body, The aforementioned contact separation mechanism is The driving force from the main motor makes the developing roller movable between the contact position and the separated position. The image forming apparatus according to claim 1.

7. The toner is a positively charged toner that is charged with positive polarity, The control unit, When the voltage is applied to the charger using the high-voltage power supply board while the developing roller is in the separated position, the photoreceptor drum is made to have a higher voltage than the developing roller by applying a positive first voltage to the charger using the high-voltage power supply board. The image forming apparatus according to claim 1.

8. The toner is a positively charged toner that is charged with positive polarity, The control unit, When the voltage is applied to the charger using the high-voltage power supply board while the developing roller is in the separated position, a positive second voltage is applied to the charger using the high-voltage power supply board, and a positive developing voltage is applied to the developing roller, so that the voltage of the photoreceptor drum is higher than that of the developing roller due to the voltage difference between the second voltage and the developing voltage. The image forming apparatus according to claim 1.

9. The toner is a negatively charged toner that is negatively charged, The control unit, When the voltage is applied to the charger using the high-voltage power supply board while the developing roller is in the separated position, a negative third voltage is applied to the charger using the high-voltage power supply board so that the voltage of the photoreceptor drum is lower than that of the developing roller. The image forming apparatus according to claim 1.

10. Furthermore, it has a cover, The developing cartridge is detachable from the image forming apparatus when the cover is open. The control unit, If it is the first startup of the image forming apparatus, or if it is detected that the developing cartridge has been replaced, the toner adhesion determination process is executed. The image forming apparatus according to claim 1.

11. The aforementioned photoreceptor drum is a plurality of photoreceptor drums, The developing cartridges are a plurality of developing cartridges arranged in accordance with each of the plurality of photosensitive drums, The control unit, The toner adhesion determination process is performed with one of the plurality of developing cartridges installed, and it is determined whether or not the toner has adhered to the one developing cartridge. The image forming apparatus according to claim 10.

12. Furthermore, it is equipped with a display unit, The control unit, When the toner solidification detection process is performed with one of the aforementioned multiple developing cartridges installed, if toner solidification is not detected, the display unit will show an instruction to remove the one developing cartridge and an instruction to install a different developing cartridge. The image forming apparatus according to claim 11.

13. Each of the aforementioned multiple developing cartridges has a storage unit, The control unit, If, as a result of performing the toner solidification determination process with the one developing cartridge installed, it is determined that toner solidification has occurred, a toner solidification information storage process is performed to store the toner solidification information in the storage unit of the one developing cartridge. Execute The image forming apparatus according to claim 11.

14. The control unit, If a new developing cartridge is installed after the toner solidification information storage process, and the toner solidification information is not stored in the storage unit of the newly installed developing cartridge, the toner solidification determination process is executed. If the toner solidification information is stored in the storage unit of the installed developing cartridge, the toner solidification determination process is not executed. The image forming apparatus according to claim 13.

15. Furthermore, The cover and, It includes a display unit, The aforementioned photoreceptor drum is a plurality of photoreceptor drums, The developing cartridges are arranged in accordance with each of the plurality of photoreceptor drums and are detachable from the image forming apparatus when the cover is open, The control unit, When all of the aforementioned developer cartridges are installed, if the toner solidification detection process determines that the toner is solidified, the display unit will show an instruction to install only the developer cartridge containing black toner. Subsequently, with only the developer cartridge containing the black toner installed, the toner solidification detection process is performed. If the toner solidification is not detected, the display unit shows that monochrome printing is possible. If the toner solidification is detected, the display unit shows an error message indicating that printing is not possible. The image forming apparatus according to claim 1.

16. The control unit, A fault determination process in which the process motor is rotated while the developing roller is in the separated position, and it is determined whether the rotational speed of the process motor reaches the target speed within a second predetermined time, and if the target speed is not reached within the second predetermined time, it is determined that the process motor is faulty. Execute, The toner adhesion determination process is performed after the failure determination process has been executed, if the process motor has not been determined to be faulty. The image forming apparatus according to any one of claims 1 to 15.

Images