Image forming device

Abstract

To provide an image forming apparatus that can move a position where a developing roller is brought into contact with a photoreceptor and a position where the developing roller is separated from the photoreceptor, and can bring the developing roller into contact with the photoreceptor after sufficiently rotating the developing roller.SOLUTION: An image forming apparatus has: a photoreceptor; a developing roller; a first motor that is configured to drive the developing roller; a drive train that is configured to transmit a driving force of the first motor to the developing roller, and includes a drive switching unit that can switch between a transmission state and a non-transmission state; a developing switching unit; a control unit; and a current detection unit that detects a current flowing in the first motor. The developing switching unit can switch between a contact state where the developing roller is in contact with the photoreceptor and a separation state where the developing roller is separated from the photoreceptor. When the current flowing in the first motor changes, the control unit stops a second motor before the developing roller is brought into contact with the photoreceptor.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus using an electrophotographic method, such as a printer, a copying machine, or a facsimile machine. [Background technology]

[0002] There is known an image forming apparatus in which a developing roller can be moved between a position where it contacts a photosensitive member and a position where it is spaced apart from the photosensitive member. The image forming apparatus disclosed in Patent Document 1 has a separation cam that separates the developing roller from the photosensitive member, and a developing clutch that switches the developing roller between rotating and stopping. The separation cam and the developing clutch are synchronized with each other and are operated by a stepping motor. In the image forming apparatus disclosed in Patent Document 1, the developing roller contacts the photosensitive member after it starts to rotate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-292868 Summary of the Invention [Problem to be solved by the invention]

[0004] It is desirable that the developing roller be sufficiently coated with toner when it comes into contact with the photosensitive member, and therefore it is preferable that the developing roller come into contact with the photosensitive member after the developing roller has rotated sufficiently.

[0005] On the other hand, in the configuration of Patent Document 1, if the stepping motor is stopped after the developing roller rotates but before it contacts the photosensitive member, the developing roller can be rotated and coated with toner before it contacts the photosensitive member. However, the time from when the stepping motor starts to drive until the developing roller starts to rotate and the time from when the stepping motor starts to drive until the developing roller contacts the photosensitive member vary due to component tolerances, etc. Therefore, it can be difficult to reliably stop the stepping motor at the timing after the developing roller rotates but before it contacts the photosensitive member.

[0006] The object of the present invention is to provide an image forming device in which the developing roller can be moved between a position where it contacts the photosensitive member and a position where it is separated from the photosensitive member, and in which the developing roller can be brought into contact with the photosensitive member after being sufficiently rotated. [Means for solving the problem]

[0007] In order to solve the above problems, one of the inventions of the present application is as follows.

[0008] A photoreceptor; A developing roller; a first motor configured to drive the developing roller; a drive train configured to transmit a driving force of the first motor to the developing roller, the drive train including a drive switching unit capable of switching between a transmission state in which the driving force is transmitted to the developing roller and a non-transmission state in which the driving force is not transmitted to the developing roller; a development switching unit capable of switching between a contact state in which the developing roller is in contact with the photosensitive member and a separation state in which the developing roller is separated from the photosensitive member, the development switching unit being configured to operate in conjunction with the operation of the drive switching unit; a second motor configured to drive the development switching unit and the drive switching unit; a control unit that controls the first motor and the second motor; a current detection unit configured to detect a current flowing through the first motor; and When the drive switching unit transitions from the non-transmission state to the transmission state and the magnitude of the current detected by the current detection unit changes, the control unit is capable of executing a stop operation to stop the second motor before the developing roller contacts the photosensitive member while driving the first motor. and the control unit drives the second motor so that the developing roller contacts the photosensitive member after the stopping operation is continued for a predetermined time. An image forming apparatus comprising: [Effects of the Invention]

[0009] According to the present invention, an image forming device can be provided in which the developing roller is configured to be movable between a position in contact with the photosensitive body and a position away from the photosensitive body, and the developing roller can be brought into contact with the photosensitive body after being sufficiently rotated. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic cross-sectional view of an image forming apparatus. [Figure 2] FIG. 2 is an explanatory diagram showing the configuration of a motor control unit. [Figure 3] FIG. 2 is an explanatory diagram showing the structure of the A motor. [Figure 4] 3A and 3B are diagrams illustrating the driving and movement of the developing roller. [Figure 5] 10A and 10B are diagrams illustrating timing of driving a developing roller and movement relative to a photosensitive member. [Figure 6] 5A to 5C are explanatory diagrams of the driving of the developing roller and its contact with the photosensitive member according to the first embodiment. [Figure 7] 4 is a flowchart of a seal removal sequence according to the first embodiment. [Figure 8] 10A and 10B are explanatory diagrams of the driving of the developing roller and its contact with the photosensitive member according to the second embodiment. [Figure 9] 10 is a flowchart of a seal removal sequence according to the second embodiment. [Figure 10] FIG. 2 is a schematic diagram of a cartridge. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of the components described in the following embodiments may be changed as appropriate depending on the configuration of the device to which the present invention is applied and various conditions. Therefore, unless otherwise specified, the scope of the present invention is not intended to be limited to these. [Example]

[0012] (Image forming device) An image forming apparatus 100 according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic cross-sectional view of the image forming apparatus 100. The image forming apparatus 100 according to this embodiment is a tandem color laser printer that uses an electrophotographic process. The configuration of the image forming apparatus 100 will be described with reference to Fig. 1.

[0013] Image forming apparatus 100 is configured to output full-color images by overlaying toner of four colors: yellow (Y), magenta (M), cyan (C), and black (K). To form images of each color, image forming apparatus 100 is equipped with laser scanners (11Y, 11M, 11C, 11K) as exposure devices and cartridges (12Y, 12M, 12C, 12K). The cartridges (12Y, 12M, 12C, 12K) are configured to be detachable from apparatus main body 100A of image forming apparatus 100.

[0014] The cartridges (12Y, 12M, 12C, 12K) have photosensitive members (13Y, 13M, 13C, 13K) that rotate in the direction of the arrow in the figure, and photosensitive member cleaners (14Y, 14M, 14C, 14K) that are provided in contact with the photosensitive members. The cartridges (12Y, 12M, 12C, 12K) further have charging rollers (15Y, 15M, 15C, 15K) and developing rollers (16Y, 16M, 16C, 16K).

[0015] The photoconductors (13Y, 13M, 13C, 13K) are photoconductor drums serving as image carriers that carry electrostatic latent images. The photoconductor cleaners (14Y, 14M, 14C, 14K) are cleaning members that come into contact with the photoconductors (13Y, 13M, 13C, 13K) and remove toner as a developer from the surfaces of the photoconductors (13Y, 13M, 13C, 13K). The charging rollers (15Y, 15M, 15C, 15K) are charging members that charge the photoconductors (13Y, 13M, 13C, 13K). The developing rollers (16Y, 16M, 16C, 16K) are developer carriers (developing members) that carry toner and develop the electrostatic latent images formed on the surfaces of the photoconductors (13Y, 13M, 13C, 13K).

[0016] The image forming apparatus 100 has an intermediate transfer belt 19 that contacts the photosensitive members (13Y, 13M, 13C, 13K) and primary transfer rollers (18Y, 18M, 18C, 18K). The intermediate transfer belt 19 is disposed so that a portion of the intermediate transfer belt 19 is sandwiched between the primary transfer rollers (18Y, 18M, 18C, 18K) and the photosensitive members (13Y, 13M, 13C, 13K).

[0017] The image forming apparatus 100 has an A motor 101, a B motor 102, and a C motor 103. In this embodiment, the A motor 101 rotates the developing rollers (16Y, 16M, 16C, 16K), the B motor 102 rotates the photosensitive members (13Y, 13M, 13C), and the C motor 103 rotates the intermediate transfer belt 19 and the photosensitive member 13K. The A motor 101, the B motor 102, and the C motor 103 are all DC brushless motors. Note that which member each motor rotates is not limited to the above configuration.

[0018] The image forming apparatus 100 has a cassette 22 that stores sheets 21 as recording materials. The sheets 21 may be paper, resin film, or the like. A feed roller 25, a conveyance roller 26a, a separation roller 26b, and a registration roller 27 are provided downstream of the cassette 22 in the conveyance direction of the sheets 21. A conveyance sensor 28 is provided downstream of the registration roller 27 in the conveyance direction of the sheets 21, and a secondary transfer roller 29 is disposed downstream of the conveyance sensor 28 so as to be in contact with the intermediate transfer belt 19. A fixing unit 30 is disposed downstream of the secondary transfer roller 29.

[0019] Reference numeral 31 denotes a controller (printer control unit) that is a control unit of the image forming apparatus 100, and includes a CPU (Central Processing Unit) 32 equipped with a ROM 32a, a RAM 32b, a timer 32c, etc., and various input / output control circuits (not shown), etc. Reference numeral 33 denotes a display panel, on which images are displayed in response to signals from the CPU 32 of the controller 31. The images displayed on the display panel 33 include characters and figures. The display panel 33 displays information related to how to use the image forming apparatus 100 and information related to the status of the image forming apparatus 100, including the status of the cartridges (12Y, 12M, 12C, 12K).

[0020] Next, a brief description will be given of the image forming operation for forming an image on the sheet 21. In a dark place inside the cartridges (12Y, 12M, 12C, 12K), the surfaces of the photoconductors (13Y, 13M, 13C, 13K) are uniformly charged by the charging rollers (15Y, 15M, 15C, 15K). The photoconductors (13Y, 13M, 13C) are rotated by the driving force of the B motor 102 transmitted by a drive transmission unit including gears. Similarly, the photoconductor 13K and the intermediate transfer belt 19 are rotated by the driving force of the C motor 103 transmitted by a drive transmission unit including gears.

[0021] Next, the laser scanners (11Y, 11M, 11C, 11K) irradiate the surfaces of the photoconductors (13Y, 13M, 13C, 13K) with laser light according to the image data. The charge in the areas irradiated with the laser light is removed, and an electrostatic latent image is formed on the surfaces of the photoconductors (13Y, 13M, 13C, 13K).

[0022] A developing bias is applied to the developing rollers (16Y, 16M, 16C, 16K) that carry toner, causing the toner to adhere from the developing rollers (16Y, 16M, 16C, 16K) to the electrostatic latent images formed on the surfaces of the photoconductors (13Y, 13M, 13C, 13K). As the toner adheres to the surfaces of the photoconductors (13Y, 13M, 13C, 13K) in accordance with the electrostatic latent images, toner images of each color are formed on the surfaces of the photoconductors (13Y, 13M, 13C, 13K).

[0023] Furthermore, a primary transfer bias is applied to the primary transfer rollers (18Y, 18M, 18C, 18K). As a result, the toner images formed on the surfaces of the photoconductors (13Y, 13M, 13C, 13K) are attracted to the intermediate transfer belt 19 at nip portions (primary transfer portions) formed between the photoconductors (13Y, 13M, 13C, 13K) and the intermediate transfer belt 19.

[0024] The CPU 32 controls the timing of image formation in each of the cartridges (12Y, 12M, 12C, 12K) according to the moving speed of the intermediate transfer belt 19. A toner image is transferred from each of the cartridges (12Y, 12M, 12C, 12K) onto the intermediate transfer belt 19, and a full-color image is finally formed on the intermediate transfer belt 19.

[0025] On one hand, the sheet 21 inside the cassette 22 is conveyed by the feeding roller 25. By the conveying roller 26a and the separating roller 26b, a single sheet 21 is separated and conveyed toward the registration roller 27. The sheet 21 passes through the registration roller 27 and is conveyed toward the secondary transfer roller 29. In the nip portion (secondary transfer portion) formed by the secondary transfer roller 29 and the intermediate transfer belt 19, the toner image on the intermediate transfer belt 19 is transferred to the sheet 21. The toner image transferred to the sheet 21 is subjected to heat fixing treatment by the fixing device 30. The sheet 21 with the toner image fixed thereon is discharged to the outside of the image forming apparatus 100.

[0026] In the present embodiment, the image forming apparatus 100 includes an environmental temperature sensor 40 that measures the environmental temperature of the outside air, and can perform an image forming operation according to the measured environmental temperature. For example, the magnitude of the developing bias and the primary transfer bias can be changed according to the external environmental temperature.

[0027] <Configuration for driving the A motor> Next, with reference to FIG. 2, a configuration for driving the A motor 101 will be described. FIG. 2 is an explanatory diagram showing the configuration of the motor control unit 120.

[0028] In the present embodiment, the A motor  101 is a brushless motor controlled by vector control. The motor control unit 120 is a circuit for rotating the A motor 101. The CPU 32 of the controller 31 controls the A motor 101 via the motor control unit 120. The motor control unit 120 includes, for example, arithmetic processing means using a microcomputer (microcontroller) 121. The microcomputer 121 incorporates a communication port 122, an AD converter 129, a counter 123, a non-volatile memory 124, a reference clock generation unit 125, a crystal oscillator 126, a PWM port 127, and a current calculation unit 128. The counter 123 performs a counting operation based on the reference clock generated by the reference clock generation unit 125. Based on this counting, measurement of the period of the input pulse, generation of a PWM signal, etc. are performed.

[0029] The PWM port 127 has six terminals and outputs three high-side PWM signals (UH, VH, WH) and three low-side PWM signals (UL, VL, WL). The motor control unit 120 has a three-phase inverter 131 made up of three high-side and three low-side switching elements. The switching elements may be, for example, transistors or FETs.

[0030] Each switching element is connected to a PWM port 127 via a gate driver 132, and can be controlled to be turned on or off by a PWM signal output from the PWM port 127. Each switching element is turned on when the PWM signal is H, and turned off when the PWM signal is L.

[0031] The U, V, and W phase outputs 133 of the inverter 131 are connected to the coils 135, 136, and 137 of the A motor 101, and can control the coil currents flowing through the coils 135, 136, and 137, respectively.

[0032] The coil currents flowing through the coils 135, 136, and 137 of the A motor 101 are detected by a current detection unit. The current detection unit has a current sensor 130, an amplifier unit 134, an AD converter 129, and a current value calculation unit 128. First, the currents flowing through the coils 135, 136, and 137 are converted into voltages by the current sensor 130. The voltages are amplified and an offset voltage is applied by the amplifier unit 134, and then input to the AD converter 129 of the microcomputer.

[0033] For example, if the current sensor 130 outputs a voltage of 0.01 V per 1 A, the amplification factor of the amplifier unit 134 is 10, and the applied offset voltage is 1.6 V, the output voltage of the amplifier unit 134 when a current of -10 A to +10 A flows will be 0.6 to 2.6 V. The AD converter 129 outputs a voltage of, for example, 0 to 3 V as an AD value of 0 to 4095. Therefore, when a current of -10 A to +10 A flows, the AD value will be approximately 819 to 3549. Note that the positive and negative signs of the current are defined as positive when the current flows from the three-phase inverter 131 to the A motor 101.

[0034] The current value calculation unit 128 performs a predetermined operation on the AD-converted data (hereinafter referred to as the AD value) to calculate the current value. That is, the offset value is subtracted from the AD value, and then the result is multiplied by a predetermined coefficient to obtain the current value. The offset value is the AD value at an offset voltage of 1.6V, and is approximately 2184. The coefficient is approximately 0.00733. In this embodiment, the AD value that is read and stored when no coil current is flowing is used as the offset value. The coefficient is stored in advance as a standard coefficient in the non-volatile memory 124.

[0035] The microcomputer 121 controls the three-phase inverter 131 via the gate driver 132, causing current to flow through coils 135, 136, and 137 of the A motor 101. The microcomputer 121 detects the current flowing through the coils 135, 136, and 137 using the current sensor 130, amplifier unit 134, and AD converter 129, and calculates the rotor position and speed of the A motor 101 from the detected current. In this way, the microcomputer 121 can control the rotation of the A motor 101.

[0036] Next, the structure of the A motor 101 will be described with reference to Fig. 3. Fig. 3 is an explanatory diagram showing the structure of the A motor 101.

[0037] The A motor 101 has a six-slot stator 140 and a four-pole rotor 141. The stator 140 has U-phase, V-phase, and W-phase coils 135, 136, and 137. The rotor 141 is made of a permanent magnet and has two pairs of N / S poles. The U-phase, V-phase, and W-phase coils 135, 136, and 137 are connected to the inverter output.

[0038] <Configuration for driving and moving the developing roller> Next, a drive configuration for rotating the developing rollers (16Y, 16M, 16C, 16K) and a mechanism for moving the developing rollers (16Y, 16M, 16C, 16K) relative to the photosensitive bodies (13Y, 13M, 13C, 13K) will be described with reference to Figure 4. Figure 4 is a diagram for explaining the drive and movement of the developing rollers (16Y, 16M, 16C, 16K).

[0039] The image forming apparatus 100 has an A motor (first motor) 101 configured to drive the developing rollers (16Y, 16M, 16C, 16K), and a drive train for transmitting the driving force of the A motor 101 to the developing rollers (16Y, 16M, 16C, 16K).

[0040] Specifically, the image forming apparatus 100 has drive transmission units (YA, YB, MA, MB, CA, CB, KA, KB) and mechanical clutches (105Y, 105M, 105C, 105K) as a drive train. YA, MA, CA, and KA can be referred to as upstream drive transmission units. YB, MB, CB, and KB can be referred to as upstream drive transmission units. The mechanical clutches (105Y, 105M, 105C, 105K) are disposed between the upstream drive transmission units (YA, MA, CA, KA) and the downstream drive transmission units (YB, MB, CB, KB). The upstream drive transmission units (YA, MA, CA, KA) and the downstream drive transmission units (YB, MB, CB, KB) are gear trains each having at least one gear. Note that the cartridges (12Y, 12M, 12C, 12K) may have part of the drive train.

[0041] The image forming apparatus 100 has developing device movement mechanisms (106Y, 106M, 106C, 106K) and a D motor (second motor) 104. The D motor 104 is configured to drive the developing device movement mechanisms (106Y, 106M, 106C, 106K) and mechanical clutches (105Y, 105M, 105C, 105K). In this embodiment, the D motor 104 is a motor (e.g., a stepping motor) whose rotational position can be controlled.

[0042] The mechanical clutches (105Y, 105M, 105C, 105K) are drive switching units configured to be able to switch between a transmission state in which the driving force of the A motor 101 is transmitted to the developing rollers (16Y, 16M, 16C, 16K) and a non-transmission state in which the driving force is not transmitted. When the mechanical clutches (105Y, 105M, 105C, 105K) are driven by the D motor 104, the transmission state and non-transmission state of the mechanical clutches (105Y, 105M, 105C, 105K) are switched.

[0043] The developing movement mechanism (106Y, 106M, 106C, 106K) is a developing switching unit (developing contact / separation mechanism) that can switch the positional relationship between the photosensitive drums (13Y, 13M, 13C, 13K) and the developing rollers (16Y, 16M, 16C, 16K) between a contact position and a separated position. The state in which the photosensitive drums (13Y, 13M, 13C, 13K) and the developing rollers (16Y, 16M, 16C, 16K) are in contact is called the contact state. The state in which the developing rollers (16Y, 16M, 16C, 16K) are separated from the photosensitive drums (13Y, 13M, 13C, 13K) is called the separated state. The developing movement mechanisms (106Y, 106M, 106C, 106K) can also be said to be configured to be able to switch the states of the photosensitive bodies (13Y, 13M, 13C, 13K) and developing rollers (16Y, 16M, 16C, 16K) between a contact state and a separated state.

[0044] In this embodiment, the developing movement mechanisms (106Y, 106M, 106C, 106K) are configured to press against portions of the cartridges (12Y, 12M, 12C, 12K). As a result, the developing rollers (16Y, 16M, 16C, 16K) move relative to the photosensitive members (13Y, 13M, 13C, 13K). Cams that press against portions of the cartridges (12Y, 12M, 12C, 12K) are used as the developing movement mechanisms (106Y, 106M, 106C, 106K).

[0045] The developing device moving mechanisms (106Y, 106M, 106C, 106K) and the mechanical clutches (105Y, 105M, 105C, 105K) are connected by switching transmission units (YC, MC, CC, KC). In this embodiment, the switching transmission units (YC, MC, CC, KC) are gear trains including at least one gear. Therefore, when the mechanical clutches (105Y, 105M, 105C, 105K) operate, the developing device moving mechanisms (106Y, 106M, 106C, 106K) also operate. More specifically, after the mechanical clutches (105Y, 105M, 105C, 105K) operate, the developing device moving mechanisms (106Y, 106M, 106C, 106K) operate a predetermined time later.

[0046] When an image formation operation is performed, the D motor 104 is driven, and the mechanical clutches (105Y, 105M, 105C, 105K) are sequentially switched from a non-transmitting state to a transmitting state, and the driving force of the A motor 101 is transmitted to the developing rollers (16Y, 16M, 16C, 16K). In conjunction with the operation of the mechanical clutches (105Y, 105M, 105C, 105K), the developing roller movement mechanisms (106Y, 106M, 106C, 106K) are sequentially operated. The developing roller movement mechanisms (106Y, 106M, 106C, 106K) sequentially switch the state of the developing rollers (16Y, 16M, 16C, 16K) relative to the photosensitive bodies (13Y, 13M, 13C, 13K) from a separated state to a contact state.

[0047] At this time, the developing device moving mechanism (106Y) operates so that the developing roller 16Y contacts the photosensitive member 13Y after the mechanical clutch 105Y transitions from the non-transmitting state to the transmitting state. The developing device moving mechanisms (106M, 106C, 106K) and the mechanical clutches (105M, 105C, 105K) also operate in the same manner.

[0048] When the image forming operation is completed, the D motor 104 is driven, and the developing roller movement mechanisms (106Y, 106M, 106C, 106K) are sequentially operated. The developing roller movement mechanisms (106Y, 106M, 106C, 106K) sequentially switch the state of the developing rollers (16Y, 16M, 16C, 16K) relative to the photosensitive bodies (13Y, 13M, 13C, 13K) from a contact state to a separation state. In conjunction with the operation of the developing roller movement mechanisms (106Y, 106M, 106C, 106K), the mechanical clutches (105Y, 105M, 105C, 105K) are sequentially operated. Thereafter, the mechanical clutches (105Y, 105M, 105C, 105K) are sequentially switched from the transmitting state to the non-transmitting state, and the transmission of the driving force of the A motor 101 to the developing rollers (16Y, 16M, 16C, 16K) is interrupted. As a result, the developing rollers (16Y, 16M, 16C, 16K) are sequentially stopped.

[0049] <Developing Roller Drive and Movement Timing> The timing of driving the developing rollers (16Y, 16M, 16C, 16K) and moving them relative to the photosensitive members (13Y, 13M, 13C, 13K) will be described with reference to FIG.

[0050] 5 is a diagram illustrating the timing of driving the developing rollers (16Y, 16M, 16C, 16K) and moving them relative to the photosensitive bodies (13Y, 13M, 13C, 13K). In FIG. 5, the horizontal axis represents the number of steps of the D motor 104, and the timing of driving and stopping the developing rollers (16Y, 16M, 16C, 16K) and the timing of contact with and separation from the photosensitive bodies (13Y, 13M, 13C, 13K) are shown.

[0051] As described above, the driving and stopping of the developing rollers (16Y, 16M, 16C, 16K) are controlled by the mechanical clutches (105Y, 105M, 105C, 105K). In addition, the contact and separation of the developing rollers (16Y, 16M, 16C, 16K) with respect to the photosensitive bodies (13Y, 13M, 13C, 13K) are controlled by the developing movement mechanisms (106Y, 106M, 106C, 106K).

[0052] A position sensor is connected to the D motor 104, and detects the home position when driving and stopping the developing rollers (16Y, 16M, 16C, 16K) and switching between contact and separation with the photosensitive bodies (13Y, 13M, 13C, 13K).

[0053] Using the CPU 32, the controller 31 controls the D motor 104, with the timing at which the signal from the position sensor is detected as the home position. Specifically, the controller 31 operates the D motor 104 by a predetermined number of steps from the timing at which the signal from the position sensor is detected, and switches between driving and stopping the developing rollers (16Y, 16M, 16C, 16K) and between contact with and separation from the photosensitive bodies (13Y, 13M, 13C, 13K).

[0054] For example, during image formation, as shown in FIG. 5, the D motor 104 is operated to the full step number, and the developing rollers (16Y, 16M, 16C, 16K) are driven and brought into contact with the photosensitive bodies (13Y, 13M, 13C, 13K).

[0055] At this time, as the D motor 104 rotates, the developing roller 16Y is driven, the developing roller 16Y is brought into contact, the developing roller 16M is driven, the developing roller 16M is brought into contact, the developing roller 16C is driven, the developing roller 16C is brought into contact, the developing roller 16K is driven, and the developing roller 16K is brought into contact. Then, the number of steps of the D motor 104 reaches FULL. The developing roller movement mechanisms (106Y, 106M, 106C, 106K) and the mechanical clutches (105Y, 105M, 105C, 105K) are connected by the switching transmission units (YC, MC, CC, KC). Therefore, when the D motor 104 rotates in one direction, the above order is not reversed.

[0056] When the image forming operation is completed, the D motor 104 operates from the step number FULL to HOME, and the developing rollers (16Y, 16M, 16C, 16K) stop and move away from the photosensitive bodies (13Y, 13M, 13C, 13K).

[0057] At this time, the developing roller 16Y is separated, the developing roller 16Y is stopped, the developing roller 16M is separated, the developing roller 16M is stopped, the developing roller 16C is separated, the developing roller 16C is stopped, the developing roller 16K is separated, and the developing roller 16K is stopped, along with the rotation of the D motor 104. Then, the step count of the D motor 104 reaches HOME.

[0058] By performing the image formation operation in conjunction with the above operation, it is possible to shorten the rotation time of the developing rollers (16Y, 16M, 16C, 16K) and the contact time with the photoconductors (13Y, 13M, 13C, 13K) while shortening the FPOT (First Print Out Time), which in turn makes it possible to suppress deterioration of parts such as the toner and developing rollers (16Y, 16M, 16C, 16K).

[0059] Due to tolerances of various components of the image forming apparatus 100, the timing at which the developing rollers (16Y, 16M, 16C, 16K) actually switch between being driven and stopped may vary with respect to the number of steps of the D motor 104. Similarly, the timing at which the developing rollers (16Y, 16M, 16C, 16K) actually contact and separate from the photosensitive bodies (13Y, 13M, 13C, 13K) may also vary. Thus, the region in which the operation of the D motor 104 may or may not perform the desired operation depending on the degree of variation is hereinafter referred to as the indefinite region.

[0060] For example, in FIG. 5, the timing at which the developing roller 16Y switches between stopped and driven is early, at the left end of the indefinite region, and late, at the right end of the indefinite region. Similarly, the timing at which the developing roller 16Y switches between separated and contact is early, at the left end of the indefinite region, and late, at the right end of the indefinite region. However, the developing roller movement mechanism 106Y and the mechanical clutch 105Y are connected by a switching transmission unit YC to prevent the timing at which the developing roller 16Y switches between stopped and driven and the timing at which the developing roller 16Y switches between separated and contact from being reversed. For example, the developing roller 16Y contacts the photosensitive element 13Y after the developing roller 16Y is driven, and stops after it is separated from the photosensitive element 13Y. The image forming apparatus 100 is also configured so that the developing roller 16M is not driven earlier than the developing roller 16Y. This relationship is also true for the other developing rollers 16M, 16C, and 16K.

[0061] <Cartridge> The cartridges (12Y, 12M, 12C, 12K) in this embodiment will be described in more detail.

[0062] In this embodiment, the cartridges (12Y, 12M, 12C, 12K) and the members that act on the cartridges (12Y, 12M, 12C, 12K) constitute stations that form images of each color. These stations have the same configuration except for the color of toner stored in the cartridges (12Y, 12M, 12C, 12K). Therefore, when it is not necessary to distinguish between the stations, the symbols (Y, M, C, K) that indicate the color of the toner stored will be omitted in the description.

[0063] 10 is a schematic diagram of cartridge 12 in this embodiment. Cartridge 12 has drum unit 12CU including photoconductor 13 and charging roller 15, and developing unit 12DU including developing roller 16. In this embodiment, developing unit 12DU is configured to be movable relative to drum unit 12CU. As developing unit 12DU moves relative to drum unit 12CU, developing roller 16 moves between a contact position where it contacts photoconductor 13 and a position spaced apart from photoconductor 13. In this embodiment, developing unit 12DU is moved relative to drum unit 12CU by being pushed by developer moving mechanism 106.

[0064] The developing unit 12DU has a developing frame 23 as a storage section. The developing frame 23 has a toner chamber 23b that stores toner T, a developing chamber 23a that is provided with the developing roller 16, and a partition wall 23c that separates the toner chamber 23b from the developing chamber 23a. An opening 23d that connects the toner chamber 23b to the developing chamber 23a is formed in the partition wall 23c. The toner T stored in the toner chamber 23b is supplied to the developing roller 16 through the opening 23d.

[0065] The developing unit 12DU has a seal member 24a that covers the opening 23d and an unsealing member 24b that moves the seal member 24a. Before the cartridge 12 is used (when the cartridge 12 is new), the seal member 24a is attached to the partition wall 23c of the current additional frame 23 so as to cover the opening 23d. As a result, the toner T is prevented from moving from the toner chamber 23b to the developing chamber 23a. In this embodiment, the unsealing member 24b is rotatably supported by the developing frame 23 and is housed in the toner chamber 23b. When the unsealing member 24b rotates, the seal member 24a is taken up by the unsealing member 24b. As a result, the seal member 24a retracts from the position covering the opening 23d, exposing the opening 23d. The position where the seal member 24a covers the opening 23d can be referred to as the sealing position, and the position where the opening 23c is exposed can be referred to as the unsealing position. That is, the unsealing member 24b driven by the A motor 101 moves the sealing member 24a from the sealing position to the unsealing position.

[0066] In this embodiment, when a new cartridge 12 is installed in the image forming apparatus 100, the controller 31 initiates a seal removal sequence to move the seal member 24a from the sealing position to the unsealing position. Specifically, the controller 31 is configured to control the A motor 101 and the D motor 104 via the CPU 32, and drives the A motor 101 and the D motor 104 to impart the driving force of the A motor 101 to the developing unit 12DU. The driving force of the A motor 101 imparted to the developing unit 12DU drives the developing roller 16 and the unsealing member 24b, and the seal member 24a is moved from the sealing position to the unsealing position. When the seal member 24a is positioned in the unsealing position, the toner T contained in the toner chamber 23b is supplied to the developing roller 16 through the opening 23d.

[0067] Whether the cartridge 12 is new or not is determined by the controller 31 based on information stored in the memory 12MU of the cartridge 12, for example.

[0068] In this embodiment, when the cartridge 12 is replaced, the drum unit 12CU and the developing unit 12DU are replaced at the same time. However, the developing unit 12DU and the drum unit 12CU may be independently detachable from the apparatus main body 100A. In this case, the seal removal sequence is executed when the developing unit 12DU is removed from the apparatus main body 100A and replaced with a new one. The developing unit 12DU may also have a memory equivalent to the memory 12MU.

[0069] <Contact between developing roller and photosensitive drum> It is preferable that the developing roller 16 be sufficiently coated with toner when it contacts the photoconductor 13. For example, by uniformly supplying the external additive of toner to the photoconductor cleaner 14 in the direction of the rotation axis of the photoconductor 13, the photoconductor cleaner 14 can stably clean the photoconductor 13. In this case, if the developing roller 16 is not sufficiently coated with toner, the external additive may not be uniformly supplied to the photoconductor cleaner 14. This phenomenon is likely to occur when the cartridge 12 is new, i.e., when the developing unit 12DU is new.

[0070] Therefore, it is preferable to rotate the developing roller 16 for a certain period of time before bringing it into contact with the photosensitive member 13. Furthermore, while the seal removal sequence is being performed, the toner T contained in the toner chamber 23b is not sufficiently supplied to the developing roller 16, which makes it easy for the developing roller 16 to be insufficiently coated with toner. Therefore, it is preferable that the seal removal sequence is also performed with the developing roller 16 separated from the photosensitive member 13.

[0071] Here, the D motor 104 can be stopped at any number of steps. If the D motor 104 is stopped after the developing roller 16 has rotated but before it comes into contact with the photosensitive member 13, the developing roller 16 can be rotated while being separated from the photosensitive member 13.

[0072] Here, the time from the start of the image forming operation to the completion of image formation on the first sheet 21 is called the first printing time. In order to shorten the first printing time and to suppress wear on the developing roller 16, it is preferable that the time from when the developing roller 16 starts to rotate until it comes into contact with the photosensitive member 13 is short.

[0073] However, if the time from when the developing roller 16 starts to rotate until it comes into contact with the photosensitive member 13 is short, as in the image forming apparatus 100 of this embodiment, it becomes difficult to determine in advance the timing at which the D motor 104 stops. Conversely, if the time from when the developing roller 16 starts to rotate until it comes into contact with the photosensitive member 13 is lengthened, the initial printing time becomes longer and the number of rotations of the developing roller 16 also increases.

[0074] In FIG. 5, if the D motor 104 is stopped at the step numbers indicated by Y, M, C, and K, the D motor 104 is stopped before the developing rollers (16Y, 16M, 16C, and 16K) contact the photosensitive bodies (13Y, 13M, 13C, and 13K). However, the step numbers indicated by Y, M, C, and K overlap with an indefinite region for stopping and switching the driving of the developing rollers (16Y, 16M, 16C, and 16K). Therefore, in the image forming apparatus 100 in which the driving of the developing rollers (16Y, 16M, 16C, and 16K) starts late, the developing rollers (16Y, 16M, 16C, and 16K) are stopped.

[0075] Similarly, in FIG. 5, if the D motor 104 is stopped at the step numbers indicated by Y', M', C', and K', the D motor 104 is stopped after the development rollers (16Y, 16M, 16C, and 16K) start to be driven. However, the step numbers indicated by Y', M', C', and K' overlap with an indefinite region for the switching between separation and contact of the development rollers (16Y, 16M, 16C, and 16K). Therefore, in an image forming apparatus 100 in which the development rollers (16Y, 16M, 16C, and 16K) contact the photosensitive members (13Y, 13M, 13C, and 13K) early, the development rollers (16Y, 16M, 16C, and 16K) will be in contact with the photosensitive members (13Y, 13M, 13C, and 13K).

[0076] As described above, with the method of stopping the D motor 104 at a predetermined number of steps, it is difficult to reliably rotate the developing roller 16 in a state where the developing roller 16 is separated from the photosensitive member 13.

[0077] <Detecting the drive of the developing roller> A method for rotating the developing roller 16 in a state where the developing roller 16 is separated from the photosensitive member 13 will be described with reference to FIG.

[0078] As described above, the image forming apparatus 100 of this embodiment has an indeterminate region for switching between stopping and driving the developing roller 16, and an indeterminate region for switching between separation and contact of the developing roller 16. If it is known that the developing roller 16 has actually been driven, the D motor 104 can be stopped before the developing roller 16 contacts the photosensitive member 13.

[0079] In the image forming apparatus 100 according to this embodiment, the current detection unit detects a change in the current flowing through the A motor 101, thereby making it possible to detect that the developing roller 16 has actually started to drive. Based on the current detection unit's detection of a change in the current flowing through the A motor 101, the controller 31 of the image forming apparatus 100 stops the D motor 104 before the developing roller 16 contacts the photosensitive member 13. At this time, the A motor 101 is in a driven state, so the developing roller 16 rotates while separated from the photosensitive member 13.

[0080] FIG. 6 is an explanatory diagram of the drive of developing roller 16Y and its contact with photoconductor 13Y. The operations of developing rollers 16M, 16C, and 16K are the same as those of developing roller 16Y, and therefore will not be described here. The horizontal axis of FIG. 6 represents time. The vertical axis of FIG. 6 represents the drive state of developing roller 16Y, the contact / separation state of developing roller 16Y, the rotational progress of A motor 101, the torque progress of A motor 101, and the current value progress of A motor 101.

[0081] First, the A motor 101 and the D motor 104 are activated and each starts rotating. When the number of steps of the D motor 104 matches the number of steps at timing A, the indefinite region of drive of the developing roller 16Y begins.

[0082] The timing when the mechanical clutch 105Y switches from the non-transmitting state to the transmitting state is defined as timing B. When the mechanical clutch 105Y enters the transmitting state, the torque of the A motor 101 increases. Because the A motor 101 is speed-controlled at a predetermined rotation speed, when the torque of the A motor 101 increases, the current value of the A motor 101 also increases. The current value of the A motor 101 up to timing A and the increase in the current value at timing B are detected by a current detection unit. The CPU 32 of the controller 31 can detect the timing when the drive of the developing roller 16Y is connected by detecting the magnitude of the current flowing through the A motor 101 using the current detection unit.

[0083] As described above, the developing roller 16Y comes into contact with the photosensitive member 13Y after the developing roller 16Y has been driven. Therefore, the D motor 104 is stopped at timing C, a predetermined time after the timing at which the developing roller 16Y starts to be driven, before the developing roller 16Y comes into contact with the photosensitive member 13Y. When the D motor 104 stops, the developing roller moving mechanism 106Y also stops, and the operation of the developing roller 16Y to approach the photosensitive member 13Y also stops. As a result, the developing roller 16Y can be driven and maintained in a state separated from the photosensitive member 13Y.

[0084] In other words, when the mechanical clutch 105 transitions from the non-transmitting state to the transmitting state and the magnitude of the current flowing through the A motor 101 detected by the current detection unit changes, the controller 31 performs an operation to stop the D motor 104 before the developing roller 16Y contacts the photosensitive member 13Y. At this time, the A motor 101 continues to be driven, the developing roller 16Y continues to rotate while the developing roller moving mechanism 106 stops. In this embodiment, the stopping of the D motor 104 by the controller 31 based on the magnitude of the current flowing through the A motor 101 detected by the current detection unit as described above is referred to as a stop operation (stop operation, stop control, stop sequence). After continuing the stop operation for a predetermined time, the controller 31 again drives the D motor 104 and the developing roller moving mechanism 106 so that the developing roller 16Y contacts the photosensitive member 13Y. As a result, the developing roller 16Y contacts the photosensitive member 13Y while coated with toner.

[0085] The controller 31 can also perform the stopping operation for the developing rollers 16M, 16C, and 16K in the same manner as for the developing roller 16Y. As a result, the developing rollers (16M, 16C, and 16K) can be driven in a state separated from the photoconductors 13Y, 13M, and 13K.

[0086] <Seal removal sequence> When the cartridge 12 in this embodiment is new, the seal member 24a covers the opening 23d, preventing the supply of toner to the developing roller 16. When the cartridge 12 is new, the controller 31 performs the seal removal sequence while the stopping operation is being performed.

[0087] The seal removal sequence in this embodiment will be described with reference to Fig. 7. Fig. 7 is a flowchart of the seal removal sequence according to this embodiment.

[0088] When the sticker removal sequence starts, the CPU 32 sets the counter N to 1 as an initial setting in S101 and starts the A motor 101. In S102, it is determined whether or not the start-up of the A motor 101 has been completed, and when the start-up of the A motor 101 has been completed, the CPU 32 advances the process to S103.

[0089] Here, counter N corresponds to each station Y, M, C, and K. If counter N is 1, the seal removal sequence for cartridge 12Y is performed. If counter N is 2, the seal removal sequence for cartridge 12M is performed. If counter N is 3, the seal removal sequence for cartridge 12C is performed. If counter N is 4, the seal removal sequence for cartridge 12K is performed.

[0090] In S103, the CPU 32 starts the rotation of the D motor 104, sets the number of steps S of the D motor 104 to S=0, and starts counting the number of steps S. In addition, the current detection unit starts detecting the current flowing through the A motor 101 (S104). The current value calculated by the current calculation unit 128 is passed to the controller 31.

[0091] In S105, the CPU 32 determines whether the step number S of the D motor 104 has reached the step number SNd. The step number SNd corresponds to the start point of an indefinite region regarding the drive of the developing roller 16 in the cartridge 12 for which the seal removal sequence is being performed (see FIG. 5).

[0092] In S106, the CPU 32 calculates the average current value Iq_N_REF. The average current value Iq_N_REF is the average of the current values ​​flowing through the A motor 101 in the section from S=0 to SNd.

[0093] In S107, the CPU 32 calculates a moving average Iq_N_AVE of the current value of the A motor 101 for the most recent 10 ms. Furthermore, the CPU 32 determines whether the value obtained by subtracting Iq_N_REF from the moving average Iq_N_AVE exceeds a predetermined value (predetermined current value). When the drive force of the A motor 101 is transmitted to the developing roller 16, the current flowing through the A motor 101 increases. As a result, when the drive force of the A motor 101 is transmitted to the developing roller 16, the value obtained by subtracting Iq_N_REF from the moving average Iq_N_AVE exceeds the predetermined value.

[0094] When the value obtained by subtracting Iq_N_REF from the moving average Iq_N_AVE exceeds a predetermined value, in S108, the CPU 32 determines that rotation of the developing roller 16 has started. The CPU 32 resets the number of steps S of the D motor 104 to zero.

[0095] Immediately after the value obtained by subtracting Iq_N_REF from the moving average Iq_N_AVE exceeds the predetermined value, the mechanical clutch 105 may not have completely transitioned to the transmission state. Therefore, the CPU 32 stops the D motor 104 after a predetermined time has elapsed since the mechanical clutch 105 transitioned from the non-transmission state to the transmission state and the magnitude of the current detected by the current detection unit changed. In this embodiment, in S109, the CPU 32 determines whether the number of steps S of the D motor 104 has become equal to or greater than the predetermined number of steps S_ref. If the number of steps S becomes equal to or greater than the predetermined number of steps S_ref, the CPU 32 proceeds to S110.

[0096] In S110, the CPU 32 determines that the developing roller 16 is rotating and separated from the photosensitive member 13, and stops the D motor 104 and the developing device moving mechanism 106. Meanwhile, the A motor 101 continues to be driven. This causes the sealing member 24a to be removed by the unsealing member 24b. In other words, while the CPU 32 is performing the stopping operation, the unsealing member 24b moves the sealing member 24a from the position covering the opening 23d, exposing the opening 23d.

[0097] In S111, the CPU 32 determines whether a predetermined time has elapsed. If the predetermined time has elapsed, the CPU 32 determines that the sealing member 24a has been removed (S112). At this time, the CPU 32 may write information indicating that the cartridge 12 is not new (the sealing member 24a has been removed) to the memory 12MU of the cartridge 12.

[0098] In S113, the CPU 32 determines whether the counter N is 4. If the counter N is not 4, the CPU 32 proceeds to S114. In S114, the CPU 32 increments the counter N by 1, and proceeds to S103. When the D motor 104 is driven in S103, the developing device moving mechanism 106 is driven.

[0099] When the counter N reaches 4 in S113, the sticker removal sequence is completed for all cartridges (12Y, 12M, 12C, 12K). When the sticker removal sequence is completed, the CPU 32 drives the D motor 104 to return it to the home position.

[0100] In this embodiment, the cartridges (12Y, 12M, 12C, 12K) are new (the seal members 24a have not been removed from all of the cartridges (12Y, 12M, 12C, 12K)). However, if some of the cartridges (12Y, 12M, 12C, 12K) are new, the seal removal sequence may be executed only for the new cartridges. For example, the CPU 32 may start the seal removal sequence when any of the cartridges (12Y, 12M, 12C, 12K) is new, and determine whether the cartridge 12 corresponding to counter N is new before proceeding to S103. In this case, if the cartridge 12 corresponding to counter N is not new, the CPU 32 proceeds to S113. If counter N is not 4, the CPU 32 proceeds to S114 and then again determines whether the cartridge 12 corresponding to counter N is new before proceeding to S103.

[0101] As described above, the CPU 32 performs the seal removal sequence together with the stopping operation of stopping the D motor 104 and rotating the developing roller 16 after the developing roller 16 has started to rotate and before it comes into contact with the photosensitive member 13. Such a stopping operation and seal removal sequence are preferably performed when the cartridge 12 is new. On the other hand, when the cartridge 12 is not new, such as during normal image formation, the CPU 32 is preferably configured not to perform the stopping operation or seal removal sequence. However, the CPU 32 may perform the stopping operation when the cartridge 12 is not new, as necessary.

[0102] As described above, by detecting the magnitude of the current flowing through the A motor 101, the D motor 104 can be stopped and the developing roller 16 can be rotated after the developing roller 16 starts to rotate but before it comes into contact with the photosensitive member 13. As a result, the initial printing time can be shortened, wear on the developing roller 16 can be suppressed, and the developing roller 16 can be brought into contact with the photosensitive member 13 in a state where it is sufficiently coated with toner. [Example]

[0103] Next, a description will be given of Example 2. In the above-described Example 1, the D motor 104 is a stepping motor, but in Example 2, a description will be given of a case where the D motor 104 is a motor other than a stepping motor, that is, a case where the D motor 104 is a motor whose number of steps cannot be managed.

[0104] In the second embodiment, the following mainly describes the differences from the first embodiment. The same configurations and operations as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and the description thereof will be omitted in principle.

[0105] In the second embodiment, the D motor 104 is stopped using a position sensor of the D motor 104. The operation of the developing roller 16Y will be described below, but the operations of the developing rollers 16M, 16C, and 16K are the same, so the description will be omitted.

[0106] 8 is an explanatory diagram of the drive of the developing roller 16Y and its contact with the photosensitive member 13Y according to this embodiment. In FIG. 8, the horizontal axis represents time. In FIG. 8, the vertical axis represents the drive state of the developing roller 16Y, the contact / separation state of the developing roller 16Y, the rotation progress of the A motor 101, the torque progress of the A motor 101, the current value progress of the A motor 101, the position sensor output, and the rotation speed progress of the D motor 104.

[0107] First, the A motor 101 is started, and the D motor 104 starts to rotate. The D motor 104 is stopped with the position sensor output at a high position, and when the D motor 104 starts to rotate, the position sensor output switches to low. When it is detected that the position sensor output has switched to low, the HOME position is detected. After the HOME position is detected, the D motor 104 is rotated for a predetermined time, and timing A is reached. Timing A coincides with the start point of the indeterminate region for driving the developing roller 16Y.

[0108] When the mechanical clutch 105Y transitions from the non-transmitting state to the transmitting state, the current flowing to the A motor 101 increases. Based on the increase in the current flowing to the A motor 101, the CPU 32 issues a stop instruction to the D motor 104. As a result, the D motor 104 stops at timing C, and the developing roller 16Y is driven in a state in which the developing roller 16Y is separated from the photosensitive member 13Y.

[0109] <Seal removal sequence> The seal removal sequence in this embodiment will be described with reference to Fig. 9. Fig. 9 is a flowchart of the seal removal sequence according to this embodiment.

[0110] After the sticker removal sequence is started and the processes of S101 and S102 are performed, the CPU 32 advances the process to S201 and starts the rotation of the D motor 104.

[0111] In S202, the CPU 32 determines whether or not a low level of the position sensor output has been detected. If a low level of the position sensor output has been detected, the CPU 32 resets the timer t of the D motor 104 in S203 and starts counting the timer t.

[0112] In S104, the current detection unit starts obtaining the value of the current flowing through the A motor 101. In S204, the CPU 32 determines whether the timer t has reached timing tNd. Timing tNd corresponds to the start of an indeterminate region regarding the drive of the developing roller 16 in the cartridge 12 for which the seal removal sequence is being performed (see FIGS. 5 and 8).

[0113] When the timer t for the D motor 104 reaches timing tNd, the CPU 32 proceeds to S205. In S205, the CPU 32 calculates Iq_N_REF. The average current value Iq_N_REF is the average of the current value flowing through the A motor 101 in the section from t=0 to tNd.

[0114] As in the first embodiment, in S107, the CPU 32 calculates a moving average Iq_N_AVE of the current value of the A motor 101 for the most recent 10 ms. Furthermore, the CPU 32 determines whether or not the value obtained by subtracting Iq_N_REF from the moving average Iq_N_AVE exceeds a predetermined value (predetermined current value).

[0115] When the value obtained by subtracting Iq_N_REF from the moving average Iq_N_AVE exceeds a predetermined value, the CPU 32 determines in S206 that the development roller 16 has started to rotate, and resets the timer t.

[0116] Immediately after the value obtained by subtracting Iq_N_REF from the moving average Iq_N_AVE exceeds the predetermined value, the mechanical clutches 105 (105Y, 105M, 105C, 105K) may not have completely transitioned to the transmission state. Therefore, the CPU 32 stops the D motor 104 after a predetermined time has elapsed since the mechanical clutch 105 transitioned from the non-transmission state to the transmission state and the magnitude of the current detected by the current detection unit changed. In this embodiment, in S207, the CPU 32 determines whether the timer t of the D motor 104 has reached or exceeded the predetermined timing t_ref. If the timer t reaches or exceeds the predetermined timing t_ref, the CPU 32 proceeds to S110.

[0117] Processes S111, S112, and S113 are the same as those in the first embodiment. In S113, the CPU 32 determines whether the counter N is 4. If the counter N is not 4, the CPU 32 proceeds to S208. In S208, the CPU 32 increments the counter N by 1 and starts the rotation of the D motor 104. Then, after resetting the timer t, the CPU 32 proceeds to S104.

[0118] When the counter N reaches 4 in S113, the sticker removal sequence is completed for all cartridges (12Y, 12M, 12C, 12K). When the sticker removal sequence is completed, the CPU 32 returns the D motor 104 to the home position.

[0119] In this embodiment, the cartridges (12Y, 12M, 12C, 12K) are brand new (the seal members 24a have not been removed from all of the cartridges (12Y, 12M, 12C, 12K)). However, if only some of the cartridges (12Y, 12M, 12C, 12K) are brand new, the seal removal sequence only needs to be performed on those brand new cartridges.

[0120] In this way, even if the D motor 104 is a motor that cannot manage the number of steps, it is possible to stop the D motor 104 and rotate the developing roller 16 after the developing roller 16 starts to rotate and before it comes into contact with the photosensitive member 13. As a result, the initial printing time is shortened, wear on the developing roller 16 is suppressed, and the developing roller 16 can come into contact with the photosensitive member 13 in a state where it is sufficiently coated with toner.

[0121] (Variation) In this embodiment, the A motor 101 is a brushless motor, but it may also be a brush motor.

[0122] In this embodiment, the CPU 32 determines whether the developing roller 16 has started to rotate based on whether the value obtained by subtracting Iq_N_REF from the moving average Iq_N_AVE exceeds a predetermined value. However, the present invention is not limited to this. For example, the CPU 32 may determine whether the developing roller 16 has started to rotate based on whether the current flowing through the A motor 101 exceeds a predetermined threshold value. [Explanation of symbols]

[0123] 101 A motor 104 D motor 31 Controller (printer control unit) 32 CPU 120 Motor control unit 105Y, 105M, 105C, 105K mechanical clutch 106Y, 106M, 106C, 106K development movement mechanism 13Y, 13M, 13C, 13K photoreceptor 16Y, 16M, 16C, 16K developing rollers

Claims

1. A photoreceptor; A developing roller; a first motor configured to drive the developing roller; a drive train configured to transmit a driving force of the first motor to the developing roller, the drive train including a drive switching unit capable of switching between a transmission state in which the driving force is transmitted to the developing roller and a non-transmission state in which the driving force is not transmitted to the developing roller; a development switching unit capable of switching between a contact state in which the developing roller is in contact with the photosensitive member and a separation state in which the developing roller is separated from the photosensitive member, the development switching unit being configured to operate in conjunction with the operation of the drive switching unit; a second motor configured to drive the development switching unit and the drive switching unit; a control unit that controls the first motor and the second motor; a current detection unit configured to detect a current flowing through the first motor; and The control unit is capable of executing a stop operation to stop the second motor before the developing roller contacts the photosensitive body while driving the first motor when the drive switching unit transitions from the non-transmission state to the transmission state and the magnitude of the current detected by the current detection unit changes, and the control unit continues the stop operation for a predetermined time, and then drives the second motor so that the developing roller contacts the photosensitive body.

2. a developing unit including: a developer storage section that stores developer and has an opening formed therein for supplying the developer to the developing roller; a seal member that covers the opening; an unsealing member that is driven by the driving force of the first motor and configured to move the seal member; and the developing roller; 2. The image forming apparatus according to claim 1, wherein, while the control unit is performing the stopping operation, the unsealing member moves the sealing member from a position covering the opening to expose the opening.

3. 3. The image forming apparatus according to claim 2, wherein the developing unit is detachable from the main body of the apparatus.

4. the second motor is a stepping motor; 4. The image forming apparatus according to claim 1, wherein the control unit is configured to stop the second motor after a predetermined time has elapsed since the drive switching unit transitioned from the non-transmission state to the transmission state and the magnitude of the current detected by the current detection unit changed.

5. 5. The image forming apparatus according to claim 1, wherein the first motor is a brushless motor.

6. 6. The image forming apparatus according to claim 1, wherein the first motor is controlled by vector control.

7. 7. The image forming apparatus according to claim 1, further comprising a cleaning member that contacts the photosensitive member.

Images