Image forming apparatus

Abstract

To effectively execute a developer supply step by reducing the unnecessary consumption of developer and unnecessary interruption time of image formation.SOLUTION: An image forming apparatus 100 has: a control unit 101 that can control an image forming operation, and a supply operation to supply developer to a contact part G between an image carrier 1 and a cleaning member 51; a driving unit 21 that can drive the image carrier 1 at a first rotation speed being at least one rotation speed during the image forming operation and a second rotation speed lower than the first rotation speed; and a torque detection unit 80 that detects information on load torque during the rotation of the image carrier 1. When an instruction to start the image forming operation is input, the control unit 101 starts up the driving unit 21 to rotate the image carrier 1 at the second rotation speed and acquires a result of detection performed by the torque detection unit 80 while the image carrier 1 rotates at the second rotation speed, and based on the result of detection performed by the torque detection unit 80, can determine whether to perform the supply operation before the image forming operation.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an image forming apparatus such as a printer, a copier, and a facsimile apparatus using an electrophotographic method or an electrostatic recording method.

Background Art

[0002] Conventionally, for example, in an image forming apparatus using an electrophotographic method, a cleaning blade as a cleaning member is often used as a cleaning means for removing deposits such as transfer residual toner adhering to the surface of an image carrier such as a photosensitive drum. The cleaning blade is disposed in contact with the surface of the image carrier, and as the image carrier rotates, deposits such as transfer residual toner are scraped off from the surface of the image carrier and collected. In a tandem type image forming apparatus capable of forming a color image by transferring a toner image from a plurality of image carriers onto an intermediate transfer body or a recording material carried on a recording material carrier, a cleaning blade is provided for each of the plurality of image carriers.

[0003] In recent years, for the purpose of reducing the size and cost of an image forming apparatus, the motors for driving a plurality of image carriers may be shared, or the motor for driving the image carrier may be shared with that for driving other members. Also, in recent years, for the purpose of increasing the throughput of an image forming apparatus, the rotational speed of the motor has been increased. As described above, a cleaning blade that contacts the image carrier is used as a cleaning means for the image carrier. However, as the frictional resistance between the cleaning blade and the image carrier increases, the torque (load torque) applied to the motor for driving the image carrier at startup increases. And when the motors for driving a plurality of members are shared as described above, in order to ensure stable driving, it may be necessary to increase the size of the motor.

[0004] To reduce the load torque, one method is to perform a developer supply process, for example, by supplying a developer (such as toner or toner additives) as a lubricant to the contact area between the cleaning blade and the image carrier (Patent Document 1). Whether or not to perform the developer supply process can be determined based on the environment and the time the image forming apparatus has been left idle, in order to suppress excessive consumption of the developer as a lubricant and interruption time for image formation. For example, it is desirable to perform the developer supply process when high load torque is expected, such as during the first run in the morning under high humidity, that is, during the first run (cooling) after the image carrier has been left idle in a high-humidity environment.

[0005] Specifically, for example, when an image forming apparatus receives an image forming request, it increases the drive speed (rotation speed) of the image carrier to a predetermined speed and brings the developing device into contact with the image carrier. Then, if the load torque is expected to be high, the image forming apparatus performs the developer supply process in this state before performing image forming; if the load torque is expected to be low, it performs image forming as is. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2010-156859 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, in the conventional configuration described above, if a high load torque is expected, the developer supply process may be executed even if the actual load torque is low. This can result in excessive developer consumption or unnecessary interruptions in image formation.

[0008] Therefore, the objective of the present invention is to enable the developer supply process to be carried out effectively by suppressing the consumption of excess developer and the interruption time of image formation. [Means for solving the problem]

[0009] The above objective is achieved by the image forming apparatus according to the present invention. In summary, the present invention comprises a rotatable image carrier, a developing member that supplies a developer to the surface of the image carrier, a transfer device that transfers an image formed with the developer on the surface of the image carrier to a recording material, a cleaning member that contacts the surface of the image carrier to form a contact portion and cleans the surface of the image carrier at the contact portion, a control unit capable of controlling an image forming operation in which an image to be transferred to the recording material is formed on the surface of the image carrier, and a supply operation in which the developer supplied from the developing member to the image carrier is supplied to the contact portion by the rotation of the image carrier, and a drive unit capable of driving the image carrier at a first rotational speed and a second rotational speed, wherein the first rotational speed is the image forming operation The image forming apparatus comprises a drive unit which has at least one rotational speed, the second rotational speed being lower than the first rotational speed, and a torque detection unit which detects information regarding the load torque during the rotation of the image carrier, wherein the control unit, when an instruction to start the image forming operation is input while the image carrier is stopped, activates the drive unit to rotate the image carrier at the second rotational speed, acquires the detection result of the torque detection unit while the image carrier is rotating at the second rotational speed, and can determine whether or not to perform the supply operation before the image forming operation based on the detection result of the torque detection unit. [Effects of the Invention]

[0010] According to the present invention, it is possible to effectively perform the developer supply process by suppressing the consumption of excess developer and the interruption time of image formation. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view of an image forming apparatus. [Figure 2] This is a schematic block diagram showing the control mechanism of an image forming apparatus. [Figure 3] This is a timing chart illustrating the operation of a typical printing process. [Figure 4] It is a schematic diagram for explaining the developer supply process. [Figure 5] It is a flowchart showing an overview of the printing process steps in Example 1. [Figure 6] It is a timing chart showing the operation when it is determined that the load torque is high after long-term storage in Example 1. [Figure 7] It is a timing chart showing the operation when it is determined that the load torque is low after long-term storage in Example 1. [Figure 8] It is a flowchart showing an overview of the printing process steps in the comparative example. [Figure 9] It is a timing chart showing the operation after long-term storage in the comparative example. [Figure 10] It is a flowchart showing an overview of the printing process steps in Example 2. [Figure 11] It is a timing chart showing the operation when it is determined that the load torque is high after long-term storage in Example 2. [Figure 12] It is a flowchart showing an overview of the printing process steps in Example 3. [Figure 13] It is a timing chart showing the transition of the load torque for each load torque detection result in Example 3. [Figure 14] It is a flowchart showing an overview of the printing process steps in Example 4. [Figure 15] It is a timing chart showing the operation when it is determined that the load torque is high after long-term storage in Example 4. [Figure 16] It is a flowchart showing an overview of the printing process steps in Example 5. [Figure 17] It is a schematic diagram of the developing contact / separation mechanism and the belt contact / separation mechanism.

Modes for Carrying Out the Invention

[0012] [[ID=4*]] Hereinafter, the image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

[0013] [Example 1] <Configuration and Operation of Image Forming Apparatus> FIG. 1 is a schematic cross-sectional view of an image forming apparatus 100 according to the present embodiment. The image forming apparatus 100 according to the present embodiment is a color laser printer that employs a tandem system (4-drum system) and an intermediate transfer member system and is capable of forming a full-color image using an electrophotographic method.

[0014] The image forming apparatus 100 includes four image forming units (stations) SY, SM, SC, and SK that form images of yellow (Y), magenta (M), cyan (C), and black (K), respectively. For elements having the same or corresponding functions or configurations in each of the image forming units SY, SM, SC, and SK, the Y, M, C, and K at the end of the reference numerals indicating that they are elements for any one of the colors may be omitted and described collectively. Further, when referring to elements for each of the colors Y, M, C, and K, the Y, M, C, and K at the end of the reference numerals may be omitted and described as Y to K. In the present embodiment, the image forming unit S includes a photosensitive drum 1 (1Y to 1K), a charging roller 2 (2Y to 2K), an exposure device 3 (3Y to 3K), a developing device 4 (4Y to 4K), a primary transfer roller 6 (6Y to 6K), a cleaning device 5 (5Y to 5K), and the like.

[0015] The photosensitive drum 1, which is a rotatable drum-shaped (cylindrical) photoreceptor (electrophotographic photoreceptor) serving as the first image carrier, is driven to rotate at a predetermined peripheral speed (process speed) in the direction of arrow R1 (clockwise direction) in Figure 1. The surface of the rotating photosensitive drum 1 is uniformly charged to a predetermined potential with a predetermined polarity (negative polarity in this embodiment) by a charging roller 2, which is a roller-type charging member serving as a charging means. During the charging process, a charging voltage (charging bias), such as a DC voltage of -1200V, is applied to the charging roller 2 by a charging power supply E1 (Figure 2). As a result, the surface of the photosensitive drum 1 is uniformly charged to, for example, -700V. The charging roller 2 is in contact with the photosensitive drum 1 and rotates in conjunction with the rotation of the photosensitive drum 1. The surface of the charged photosensitive drum 1 is scanned and exposed by an exposure device (laser scanner unit) 3, which acts as an exposure means, with laser light corresponding to the image information of the color components corresponding to each image forming section S, and an electrostatic latent image (electrostatic image) is formed on the photosensitive drum 1. The exposure device 3 has a reflective mirror and a laser diode (light-emitting element) and irradiates the photosensitive drum 1 with laser light. The potential of the area on the surface of the photosensitive drum 1 exposed by the laser light of the exposure device 3 becomes, for example, -100V.

[0016] The electrostatic latent image formed on the photosensitive drum 1 is developed (visualized) by a developing device 4, which is a developing means, when toner is supplied as a developer, and a toner image (toner image, developer image) is formed on the photosensitive drum 1. The developing device 4 includes a developing container 42 and a developing roller 41 as a developing member (developer carrier) provided inside the developing container 42. The developing device 4 is configured so that the developing roller 41 can move toward and away from the photosensitive drum 1. In this embodiment, the developing device 4 uses a non-magnetic one-component developer as the developer. During the developing process, the developing roller 41 is in contact with the photosensitive drum 1. Also, during the developing process, the developing roller 41 is rotated at a predetermined peripheral speed in a direction in which the direction of movement of the surface of the photosensitive drum 1 and the direction of movement of the surface of the developing roller 41 are in the forward direction at the contact point between the photosensitive drum 1 and the developing roller 41. In this embodiment, the developing roller 41 rotates at approximately the same peripheral speed as the peripheral speed of the photosensitive drum 1. Furthermore, during the development process, a development voltage (development bias), which is a DC voltage of, for example, -350V, is applied to the development roller 41 by the development power supply E2 (Figure 2). As a result, the negatively polarized toner supported on the development roller 41 moves onto the photosensitive drum 1 in accordance with the electrostatic latent image and adheres to the photosensitive drum 1. Thus, in this embodiment, toner charged with the same polarity as the charging polarity of the photosensitive drum 1 (negative polarity in this embodiment) adheres to the exposed area (image area) on the photosensitive drum 1, where the absolute value of the potential has decreased after uniform charging treatment and exposure (reverse development method). In this embodiment, the normal charging polarity of the toner, which is the main charging polarity of the toner during development, is negative polarity.

[0017] An intermediate transfer belt (ITB) 30, which is an intermediate transfer body composed of an endless belt as a second image carrier, is arranged opposite the four photosensitive drums 1. The intermediate transfer belt 30 is stretched by a plurality of tension rollers (support rollers), including drive rollers 31, pre-transfer rollers 32, and secondary transfer opposing rollers 33. In this embodiment, the drive rollers 31 also serve as tension rollers that apply a predetermined tension to the intermediate transfer belt 30. The intermediate transfer belt 30 rotates (circumferentially moves) in the direction of arrow R2 (counterclockwise) in Figure 1 at a peripheral speed (process speed) approximately the same as the peripheral speed of the photosensitive drums 1, as the drive rollers 31 are rotated. On the inner circumferential surface side of the intermediate transfer belt 30, primary transfer rollers 6Y to 6K, which are roller-type primary transfer members that serve as primary transfer means, are arranged corresponding to each photosensitive drum 1Y to 1K. The primary transfer roller 6 presses the intermediate transfer belt 30 toward the photosensitive drum 1, forming a primary transfer section (primary transfer nip section) N1, which is the contact area between the photosensitive drum 1 and the intermediate transfer belt 30. The pre-transfer roller 32, the secondary transfer opposing roller 33, and each primary transfer roller 6 rotate in conjunction with the rotation of the intermediate transfer belt 30. The toner image formed on the photosensitive drum 1 is transferred (primary transfer) onto the rotating intermediate transfer belt 30 in the primary transfer section N1 by the action of the primary transfer roller 6. During the primary transfer process, a primary transfer voltage (primary transfer bias) of, for example, +1000V, is applied to the primary transfer roller 6 by the primary transfer power supply E3 (Figure 2), which is a DC voltage with the opposite polarity to the normal charging polarity of the toner (positive polarity in this embodiment). For example, when forming a full-color image, the toner images of each color, Y, M, C, and K, formed on each photosensitive drum 1Y to 1K, are sequentially transferred onto the intermediate transfer belt 30 so as to be superimposed. In this embodiment, the intermediate transfer belt 30 is 1 × 10 7 ~1 × 10 14 It is composed of an endless film-like material with a volume resistivity of Ωcm and a thickness of approximately 50-150μm. The above volume resistivity was obtained using a measurement probe compliant with JIS method K6911 and an ADVANTEST R2340 high-resistivity meter, under conditions of 25°C and 50% relative humidity, with a voltage of 50-100V applied.

[0018] On the outer circumferential surface of the intermediate transfer belt 30, a secondary transfer roller 7, which is a roller-type secondary transfer member serving as a secondary transfer means, is positioned opposite the secondary transfer opposing roller 33. The secondary transfer roller 7 is pressed toward the secondary transfer opposing roller 33 and contacts the secondary transfer opposing roller 33 via the intermediate transfer belt 30, forming a secondary transfer portion (secondary transfer nip portion) N2, which is the contact portion between the intermediate transfer belt 30 and the secondary transfer roller 7. The secondary transfer roller 7 may rotate in conjunction with the rotation of the intermediate transfer belt 30, or it may be rotationally driven independently of the intermediate transfer belt 30. The toner image formed on the intermediate transfer belt 30 is transferred (secondary transfer) in the secondary transfer portion N2 to the recording material P, which is being transported sandwiched between the intermediate transfer belt 30 and the secondary transfer roller 7, by the action of the secondary transfer roller 7. During the secondary transfer process, a secondary transfer voltage (secondary transfer bias), which is a DC voltage with the opposite polarity (positive polarity in this embodiment) to the normal charging polarity of the toner, is applied to the secondary transfer roller 7 by the secondary transfer power supply E4 (Figure 2). Recording material (transfer material, recording medium, sheet) P, such as recording paper or a plastic sheet, is housed in the recording material storage section (cassette) 12. When the operation of the job (printing process) starts, the recording material P is separated one by one from the recording material storage section 12 by a pickup roller 13 or the like, which acts as a feeding member, and fed out. After the leading edge position of the recording material P fed out from the recording material storage section 12 is detected by the resist sensor 8, the transport of the recording material P is temporarily stopped when the leading edge has slightly passed the transport roller pair (resist roller pair) 14, 15. This recording material P is then transported to the secondary transfer section N2 by the transport roller pair 14, 15, with the timing synchronized with the toner image on the intermediate transfer belt 30 in the secondary transfer section N2. Then, in the secondary transfer section N2, the toner image is transferred onto the recording material P from the intermediate transfer belt 30.

[0019] The recording material P onto which the toner image has been transferred is transported to a fixing device 9, which serves as a fixing means. The fixing device 9 uses fixing roller pairs 10 and 11 to heat and pressurize the recording material P carrying the unfixed toner image, thereby fixing (melting and solidifying) the toner image onto the recording material P. After that, the recording material P with the fixed toner image is discharged (output) onto an output tray 16 located outside the main body 110 of the image forming apparatus 100.

[0020] On the other hand, any deposits such as toner that remain on the photosensitive drum 1 without being transferred onto the intermediate transfer belt 30 during the primary transfer (transfer residue toner) are removed from the photosensitive drum 1 and collected by a cleaning device 5, which serves as a cleaning means. The cleaning device 5 includes a cleaning blade 51 as a cleaning member and a cleaning container 52. The cleaning blade 51 is a plate-shaped (blade-shaped) elastic member made of an elastic material such as urethane rubber. The cleaning blade 51 contacts the surface of the photosensitive drum 1 with a predetermined pressure in a direction that is counter to the direction of movement of the surface of the photosensitive drum 1, forming a contact portion (cleaning portion) G (Figure 4) between the photosensitive drum 1 and the cleaning blade 51. More specifically, the cleaning blade 51 is positioned such that its longitudinal direction is substantially parallel to the rotation axis direction of the photosensitive drum 1, and its free end, which is one end in its short direction, is located upstream of the direction of movement of the surface of the photosensitive drum 1 compared to its fixed end, which is the other end. The cleaning blade 51 is positioned such that the edge portion on the photosensitive drum 1 side of the longitudinally extending edge portion that forms the end face of the free end is in contact with the surface of the photosensitive drum 1. The fixed end of the cleaning blade 51 is fixed to a support member (not shown), and the support member is fixed to the cleaning container 52. The cleaning device 5 uses the cleaning blade 51 to scrape off any attached materials such as residual toner from the rotating photosensitive drum 1 and collects them in the cleaning container 52.

[0021] Furthermore, any deposits such as toner that remain on the intermediate transfer belt 30 without being transferred onto the recording material P during secondary transfer (transfer residue toner) are removed and collected from the intermediate transfer belt 30 by a belt cleaning device 34, which serves as an intermediate transfer body cleaning means. The belt cleaning device 34 comprises a belt cleaning blade 35 as a belt cleaning member and a belt cleaning container 36. The belt cleaning device 34 uses the belt cleaning blade 35 to scrape off deposits such as transfer residue toner from the rotating intermediate transfer belt 30 and collects them in the belt cleaning container 36.

[0022] In this embodiment, in each image forming unit S, the photosensitive drum 1, the charging roller 2 acting thereon as a process means, the developing device 4, and the cleaning device 5 are integrally formed into a process cartridge that can be attached to and detached from the main body 110 of the image forming apparatus 100.

[0023] In this embodiment, the image forming apparatus 100 has a drum motor (stepping motor) 21 as a common drive source (drive unit) for four photosensitive drums 1Y to 1K (Figure 2). Also in this embodiment, the image forming apparatus 100 has a developing motor (stepping motor) 22 as a common drive source for four developing rollers 41Y to 41K (Figure 2). Also in this embodiment, the image forming apparatus 100 has a belt motor (stepping motor) 23 as a drive source for the intermediate transfer belt 30 (drive roller 31) (Figure 2).

[0024] In this embodiment, the image forming apparatus 100 also has a developing contact / separation mechanism 60 as a switching unit for switching the contact / separation state between the photosensitive drum 1 and the developing roller 41 of the four image forming units SY to SK (Figure 17(a)). In this embodiment, the developing contact / separation mechanism 60 can synchronously switch the contact / separation state between the photosensitive drum 1 and the developing roller 41 of the four image forming units SY to SK. The developing contact / separation mechanism 60 is configured as follows, for example. As shown in Figure 17(a), the developing container 42 is rotatable (oscillating) around a rotation axis substantially parallel to the rotation axis direction of the photosensitive drum 1, and is biased by a biasing member such as a spring so that the developing roller 41 rotates in a direction in which it contacts the photosensitive drum 1. The developing contact / separation mechanism 60 also has a developing contact / separation solenoid 61 as a drive source, and a developing contact / separation moving member 62 driven by the developing contact / separation solenoid 61. The developing-to-contact mechanism 60 can control the pressing and release of the developing-to-contact moving member 62 against the receiving portion 43 provided on the developing container 42 of the developing device 4. By pressing the receiving portion 43 with the developing-to-contact moving member 62, the developing roller 41 can be separated from the photosensitive drum 1. Conversely, by releasing the pressure on the receiving portion 43 by the developing-to-contact moving member 62, the developing roller 41 can be brought into contact with the photosensitive drum 1. In this embodiment, the developing-to-contact mechanism 60 generally brings the developing roller 41 into contact with the photosensitive drum 1 during developing. Also, when the image forming apparatus 100 is stopped (standby state, sleep state, power OFF state, etc.), the developing-to-contact mechanism 60 separates the developing roller 41 from the photosensitive drum 1.

[0025] Furthermore, in this embodiment, the image forming apparatus 100 has a belt contact / separation mechanism 70 as a switching unit for the contact / separation state between the photosensitive drum 1 and the intermediate transfer belt 30 (Figure 17(b)). In this embodiment, the belt contact / separation mechanism 70 can synchronously switch the contact / separation state between the photosensitive drum 1 and the intermediate transfer belt 30 of the four image forming units SY to SK. The belt contact / separation mechanism 70 has, for example, the following configuration. In the four image forming units SY to SK, the primary transfer roller 6 is movable in a direction toward and away from the photosensitive drum 1. As shown in Figure 17(b), the belt contact / separation mechanism 70 has a belt contact / separation solenoid 71 as a drive source and a moving member 72 driven by the belt contact / separation solenoid 71. The moving member 72 moves the four primary transfer rollers 6Y to 6K. The belt contact / separation mechanism 70 is capable of controlling the movement of the primary transfer rollers 6Y to 6K by the moving member 72. The belt contact / separation mechanism 70 moves the primary transfer roller 6 away from the photosensitive drum 1 (retracts it), thereby separating the intermediate transfer belt 30 from the photosensitive drum 1. Alternatively, the belt contact / separation mechanism 70 can move the primary transfer roller 6 closer to the photosensitive drum 1, bringing the intermediate transfer belt 30 into contact with the photosensitive drum 1. In this embodiment, the belt contact / separation mechanism 70 can switch the contact / separation state between the photosensitive drums 1Y~1K and the intermediate transfer belt 30 in each image forming unit SY~SK between the following states: "fully separated state" and "fully in contact state". The "fully separated state" is when the intermediate transfer belt 30 is separated from the photosensitive drum 1 in all four image forming units SY~SK. The "fully in contact state" is when the intermediate transfer belt 30 is in contact with the photosensitive drum 1 in all four image forming units SY~SK. In this embodiment, for example, when the image forming apparatus 100 is stopped (standby state, sleep state, power-off state), the "fully separated state" is used. During image formation, the "fully contacted state" is used.

[0026] <Control configuration of image forming apparatus> Figure 2 is a schematic block diagram showing the control configuration of the image forming apparatus 100 in this embodiment. The CPU 101, acting as the control unit, controls each part of the image forming apparatus 100 using the RAM 103, acting as a storage unit, as a work area, based on various control programs stored in the ROM 102, acting as a storage unit. The ROM 102 stores various control programs, various data, tables, etc. The RAM 103 is allocated a program load area, a work area for the CPU 101, a storage area for various data, etc., and also includes a drum motor stop time counting unit 104, which will be described later as a counting means. The drum motor stop time counting unit 104 is an example of an acquisition unit that acquires information (a count value as an index value indicating time) regarding the time that the photosensitive drum 1Y~1K (drum motor 21) is stopped between the end of the previous job and the input of the start instruction for the current job to the CPU 101.

[0027] Furthermore, a drive control unit 108 is connected to the CPU 101. In this embodiment, the drive control unit 108 is connected to a drum motor 21, a developing motor 22, a belt motor 23, a developing contact / separation mechanism 60, a belt contact / separation mechanism 70, and the like. The drive control unit 108 is also connected to a charging power supply E1, a developing power supply E2, a primary transfer power supply E3, a secondary transfer power supply E4, and a torque detection unit 80, which will be described later. Although not shown in Figure 2, in this embodiment, the charging power supply E1, the developing power supply E2, and the primary transfer power supply E3 are each independently provided for each image forming unit S. For example, the drive control unit 108 controls the operation of motors for driving various driven members, the application of various voltages, and exposure by the exposure device 3, according to commands from the CPU 101. The various driven members include the photosensitive drum 1, the developing roller 41, and the intermediate transfer belt 30. The various voltages include the charging voltage, the developing voltage, the primary transfer voltage, and the secondary transfer voltage. In this embodiment, as described above, the image forming apparatus 100 has a drum motor 21 as a common driving means for driving all photosensitive drums 1. In this embodiment, the image forming apparatus 100 also has a torque detection unit 80 as a torque detection means for detecting the total load torque of all photosensitive drums 1. In this embodiment, as described above, the image forming apparatus 100 also has a developing motor 22 as a common driving means for driving all developing rollers 41. In this embodiment, the drive control unit 108 can control these motors independently. In this embodiment, as described above, the image forming apparatus 100 has a belt contact / separation solenoid 71 that switches the contact / separation state between the photosensitive drums 1Y~1K and the intermediate transfer belt 30. In this embodiment, the image forming apparatus 100 also has a developing contact / separation solenoid 61 that switches the contact / separation state between the photosensitive drums 1Y~1K and the developing rollers 41Y~41K. In this embodiment, the drive control unit 108 can control these solenoids independently.

[0028] Furthermore, a non-volatile memory 109 is connected to the CPU 101 as a storage unit. The non-volatile memory 109 is a storage device that stores various types of data.

[0029] Here, the image forming apparatus 100 executes a job (printing process), which is a series of operations that form and output an image on one or more recording materials P, initiated by a single start instruction. In this embodiment, the start instruction is input to the image forming apparatus 100 from an external device (not shown), such as a personal computer connected to the image forming apparatus 100. A job (printing process) generally includes an image forming process, a pre-rotation process, an inter-paper process when forming an image on multiple recording materials P, and a post-rotation process. The image forming process is the period during which the electrostatic latent image, toner image, primary transfer of the toner image, and secondary transfer of the image to be actually formed and output on the recording material P are performed, and this period is referred to as the image forming time (image forming period). More specifically, the timing of the image forming time differs depending on the position where each of these processes—the formation of the electrostatic latent image, the formation of the toner image, the primary transfer of the toner image, and the secondary transfer of the toner image—is performed. The pre-rotation process is the period during which preparatory operations are performed before the image forming process, from when the start instruction is input until the image is actually formed. The inter-paper process (inter-recording material process, inter-image process) is the period between recording materials P when image formation is performed continuously on multiple recording materials P (continuous image formation). The post-rotation process is the period during which the tidying operations (preparation operations) after the image formation process are performed. Non-image formation time (non-image formation period) is the period other than the image formation time, and includes the pre-rotation process, inter-paper process, post-rotation process, and pre-multi-rotation process, which is the preparation operation when the image forming apparatus 100 is powered on or when it returns from sleep mode. Furthermore, non-image formation time includes the standby state, sleep state, and power-off state of the image forming apparatus 100. The standby state is the state in which the image forming apparatus 100 is powered on and waiting for job information input. The sleep state is the state in which the image forming apparatus 100 is powered on and waiting to return to the standby state or other state in a state where power consumption is lower than in the standby state.

[0030] <Torque detection unit> Next, the torque detection unit 80, which serves as a torque detection means in this embodiment, will be described.

[0031] In this embodiment, the image forming apparatus 100 can detect the total load torque of the four photosensitive drums 1Y to 1K while the four photosensitive drums 1Y to 1K are being driven, using the torque detection unit 80. Specifically, the torque detection unit 80 indirectly detects the load torque generated when driving the four photosensitive drums 1Y to 1K by detecting the magnitude of the current (drive current) flowing through the drum motor 21. When the torque detection unit 80 detects the current value flowing through the drum motor 21, it sends the detection result to the drive control unit 108. The CPU 101, acting as a calculation unit, then acquires the detection result of the current value sent to the drive control unit 108 and converts it into load torque.

[0032] In order to accurately detect the load torque, it is desirable to perform the load torque detection while the rotation speed of the photosensitive drum 1 is stable.

[0033] Furthermore, if the load torque is detected while the developing roller 41 is in contact with the photosensitive drum 1, it would take extra time for contact and also impose an extra driving load. Therefore, in this embodiment, the load torque is detected while the developing roller 41 is separated from the photosensitive drum 1.

[0034] In this embodiment, a torque detection unit 80 that indirectly detects the load torque of the photosensitive drums 1Y to 1K was used as the torque detection means. However, a torque detection means that directly detects the load torque of the photosensitive drums 1Y to 1K can also be used. Such a torque detection means could be a torque measuring device installed on the rotating shaft of the photosensitive drums 1Y to 1K.

[0035] <Normal printing process> The printing process includes a monochrome printing process in which image formation is possible only in the black image forming unit PK, and a full-color printing process in which image formation is possible in four image forming units PY to PK. Furthermore, the image forming apparatus 100 is capable of changing the process speed in the printing process according to various conditions, such as the type of recording material P on which the image is formed. The full-color printing process will be explained below as an example.

[0036] The operation of the normal printing process in this embodiment will be explained using Figure 3. Figure 3 is a chart showing the relationship between the operation timing of the drive system and the formation timing of the image (electrostatic latent image) in the printing process when plain paper is used as the recording material P, and the change in the load torque applied to the drum motor 21. In Figure 3, LR1 indicates the start timing of electrostatic latent image formation.

[0037] When the CPU 101 receives a full-color print command from an external device, it starts the belt motor 23, drum motor 21, and developing motor 22 at a target speed of the normal speed (normal speed start-up process). This normal speed is the rotational speed of the belt motor 23, drum motor 21, and developing motor 22 (or intermediate transfer belt 30, photosensitive drum 1, and developing roller 41) corresponding to the process speed during image formation when plain paper is used as the recording material P. The CPU 101 brings the photosensitive drum 1Y~1K into contact with the intermediate transfer belt 30 when the rotational speeds of the intermediate transfer belt 30 and the photosensitive drum 1Y~1K have all converged to the normal speed (belt contact process). Furthermore, the CPU 101 brings the photosensitive drum 1Y~1K into contact with the developing roller 41Y~41K at a predetermined timing after the rotational speeds of the developing roller 41Y~41K and the photosensitive drum 1Y~1K have all converged to the normal speed (development contact process). More specifically, in this embodiment, the charging process of the photosensitive drum 1 by the charging roller 2 begins after the rotational speed of the photosensitive drum 1 reaches its normal speed. In a normal printing process, the development contact process is performed so that the development roller 41 contacts the photosensitive drum 1 after the timing when the charged area on the photosensitive drum 1 reaches a position (development position) where it can contact the development roller 41 in the rotational direction of the photosensitive drum 1. Then, the CPU 101 controls as follows, starting from timing LR1, when the contact between the intermediate transfer belt 30 and the photosensitive drums 1Y~1K, and the contact between the photosensitive drums 1Y~1K and the development rollers 41Y~41K are completed. In other words, starting from timing LR1, the CPU 101 controls the formation of electrostatic latent images for image formation in the order of Y, M, C, and K with predetermined time differences, and develops these electrostatic latent images with toners of each color (image formation process).

[0038] <Developer supply process> In this embodiment, the image forming apparatus 100 performs a developer supply process as a supply operation with the aim of reducing the coefficient of friction between the photosensitive drum 1 and the cleaning blade 51. Figure 4 is a schematic diagram illustrating the developer supply process. In Figure 4, P1 indicates the lubricant supplied to the cleaning blade 51.

[0039] In the developer supply process, a developer (toner or toner additives (such as external additives)) is applied as a lubricant to the non-image area outside the image area (the area where a toner image can be formed) from the leading edge to the trailing edge in the rotational direction of the photosensitive drum 1. Examples of means for applying toner or toner additives to the photosensitive drum 1 include: One method involves forming an electrostatic latent image on the photosensitive drum 1 with the developing roller 41 in contact with the drum (by performing a charging process, exposure process, and development process to form a toner image). In this method, for example, a predetermined toner image (supply toner image) with a predetermined width can be formed in the direction of movement of the surface of the photosensitive drum 1 (sub-scanning direction) over substantially the entire image formation area in the rotational axis direction (main scanning direction) of the photosensitive drum 1. The supply toner image may be a solid image (image at the highest density level) or a halftone image. Another method involves bringing the developing roller 41 into contact with the photosensitive drum 1 and adjusting the charging voltage and developing voltage to facilitate the adhesion of the developer (lubricant) in the developing device 4 to the photosensitive drum 1 (by applying at least one of the charging voltage or developing voltage to adhere the toner without performing an exposure process). In this method, for example, the developer can be adhered to the photosensitive drum 1 by applying the developing voltage without performing a charging process. Alternatively, the photosensitive drum 1 can be rotated for a certain period of time while the developing roller 41 is in contact with the photosensitive drum 1. When the developer adhering to the photosensitive drum 1 due to the contact between the photosensitive drum 1 and the developing roller 41 reaches the vicinity of the edge of the cleaning blade 51, this developer acts as a lubricant, and the frictional force between the photosensitive drum 1 and the cleaning blade 51 begins to decrease.

[0040] In this embodiment, in order to facilitate the supply of lubricant to the contact area G between the photosensitive drum 1 and the edge portion of the cleaning blade 51, the primary transfer roller 6 is retracted from the photosensitive drum 1 during the developer supply process, thereby separating the intermediate transfer belt 30 from the photosensitive drum 1. Alternatively, instead of retracting the primary transfer roller 6 from the photosensitive drum 1 to separate the intermediate transfer belt 30 from the photosensitive drum 1, the following may be used: With the intermediate transfer belt 30 in contact with the photosensitive drum 1, a DC voltage with the same polarity as the charge polarity of the lubricant, for example, -1000V, may be applied to the primary transfer roller 6 to prevent the lubricant from being transferred from the photosensitive drum 1 to the intermediate transfer belt 30.

[0041] Furthermore, the effect of reducing the friction coefficient between the photosensitive drum 1 and the cleaning blade 51 increases as the amount of developer supplied increases, but the effect does not increase significantly beyond a certain amount. Therefore, it is desirable to supply an appropriate amount as needed.

[0042] In this embodiment, the developer (toner or toner additive) acting as a lubricant is supplied to the contact area G between the photosensitive drum 1 and the cleaning blade 51 by simply rotating the photosensitive drum 1 for a certain period of time while the developing roller 41 is in contact with the photosensitive drum 1. In other words, in this embodiment, in the developer supply process, the photosensitive drum 1 is rotated for a predetermined time while the developing roller 41 is in contact with the photosensitive drum 1, without applying either a charging voltage or a developing voltage.

[0043] The developer supply process reduces the coefficient of friction between the photosensitive drum 1 and the cleaning blade 51, thereby reducing the load torque on the drum motor 21 and ensuring stable operation. Furthermore, the developer supply process suppresses the generation of abnormal noise due to friction between the cleaning blade 51 and the photosensitive drum 1, as well as the curling of the cleaning blade 51.

[0044] <Printing process after long-term storage> During the charging process of the photosensitive drum 1 by the charging roller 2, discharges generate discharge products such as ozone and NOx, which may adhere to the surface of the photosensitive drum 1. These discharge products are scraped off by the cleaning blade 51, but if the amount adhering to the surface of the photosensitive drum 1 exceeds the amount scraped off by the cleaning blade 51, they gradually accumulate on the surface of the photosensitive drum 1 through repeated image forming operations. When discharge products adhere to the surface of the photosensitive drum 1, the coefficient of friction between the surface of the photosensitive drum 1 and the cleaning blade 51 increases. In particular, if the photosensitive drum 1 remains stationary for a long period of time in a high-humidity environment (also referred to here as "long-term storage"), the absorption of moisture by the deposits on the surface of the photosensitive drum 1 is accelerated, and the coefficient of friction between the photosensitive drum 1 and the cleaning blade 51 may increase even further.

[0045] Therefore, in this embodiment, the image forming apparatus 100 reduces the frictional force between the photosensitive drum 1 and the cleaning blade 51 by effectively performing a developer supply process as needed during the printing process after a long period of storage.

[0046] Figure 5 is a flowchart illustrating the general procedure of the printing process in this embodiment.

[0047] When the CPU 101 receives a full-color print command from an external device, it first determines whether the device is in a state of prolonged inactivity (S101). In this embodiment, the CPU 101 determines whether the elapsed time since the drum motor 21 stopped, as counted by the drum motor stop time counting unit 104, is above a predetermined threshold. For example, if the elapsed time since the drum motor 21 stopped is 12 hours or more, it can be determined that the device is in a state of prolonged inactivity.

[0048] If the CPU 101 determines in S101 that the machine has been left idle for a long period of time ("Yes"), it proceeds to the printing process after the long period of idle time. Specifically, the CPU 101 starts the belt motor 23, drum motor 21, and developing motor 22 at a low speed (low-speed start-up process) (S105). This low speed is the rotational speed of the belt motor 23, drum motor 21, and developing motor 22 (or intermediate transfer belt 30, photosensitive drum 1, and developing roller 41) which is lower than the normal speed mentioned above. The CPU 101 also uses the torque detection unit 80 to detect the load torque when the rotational speed of the photosensitive drum 1Y~1K, etc., is stable at a low speed (load torque detection process) (S106). Next, the CPU 101 determines whether the detected load torque is above a predetermined threshold (S107). In this embodiment, the predetermined threshold for load torque is set to 3 (kgf / cm). If the CPU 101 determines in S107 that the load torque is high ("Yes"), it brings the developing rollers 41Y~41K into contact with the photosensitive drums 1Y~1K (developing contact process) (S108). Then, with the developing rollers 41Y~41K in contact with the photosensitive drums 1Y~1K, the CPU 101 performs a developer supply process in which it rotates the photosensitive drums 1Y~1K for a predetermined amount of time (S109). After performing the developer supply process, the CPU 101 stops all operations of the photosensitive drums 1 and the developing device 4 (stopping process) (S110). After that, the CPU 101 performs the aforementioned normal printing process, namely the normal speed start process (S102), the belt contact process and the developing contact process (S103), and the image formation process (S104), and then finishes the printing process. On the other hand, if the CPU 101 determines in S107 that the load torque is low ("No"), it increases the rotational speed of the belt motor 23, drum motor 21, and developing motor 22 to the normal speed (S111). After that, the CPU 101 performs the belt contact process, the developing contact process (S103), and the image formation process (S104) to complete the printing process.

[0049] Furthermore, if the CPU 101 determines in S101 that the machine is not in a state of prolonged inactivity ("No"), it controls the machine as follows: It performs the aforementioned normal printing process, namely the normal speed startup process (S102), the belt contact process and the development contact process (S103), and the image formation process (S104), and then terminates the printing process.

[0050] Here, we will further explain the operation when the load torque is determined to be high in S107 of Figure 5, using Figure 6. Figure 6 is a chart similar to Figure 3, which explains the operation when the load torque is determined to be high in the printing process after a long period of inactivity.

[0051] When the CPU 101 receives a full-color printing instruction from an external device, it starts the belt motor 23, drum motor 21, and developing motor 22 at a low speed as the target speed (low-speed start-up step). Next, after the above start-up, the CPU 101 detects the load torque using the torque detection unit 80 once the rotation speed of the photosensitive drum 1Y~1K etc. has stabilized (load torque detection step). Then, if the CPU 101 determines that the load torque TM1 (kgf / cm) detected in the load torque detection step is 3 (kgf / cm) or higher, i.e., the load torque is high, it proceeds to the developing contact step described above. Next, the CPU 101 proceeds to the developer supply step described above, and after performing the developer supply step for a predetermined time, it proceeds to the stop step described above. That is, the CPU 101 separates the photosensitive drum 1Y~1K and the developing roller 41Y~41K and stops the drum motor 21 and the developing motor 22. Furthermore, once the CPU 101 moves to the developer supply process, it no longer needs to drive the belt motor 23, so it stops the belt motor 23. Then, after stopping all operations of the photosensitive drum 1 and the developing device 4 through the stopping process, the CPU 101 performs the aforementioned normal printing process.

[0052] Next, we will explain why the belt motor 23, drum motor 21, and developing motor 22 are started at low speeds. Table 1 shows the maximum load torque of the drum motor 21 at startup in a normal temperature and humidity environment (25°C, 50%RH) and in a high temperature and high humidity environment (30°C, 80%RH) where moisture absorption by the surface of the photosensitive drum 1 is accelerated and the load torque tends to increase. Table 1 shows the load torque values ​​for a normal temperature and humidity environment when the standing time is 150 hours or more, and the load torque values ​​for a standing time of 0 hours, 12 hours, 24 hours, 48 ​​hours, 96 hours, and 150 hours or more in the high temperature and high humidity environment. In this embodiment, the low speed and normal speed are 100 mm / s and 300 mm / s, respectively. Note that the low speed and normal speed are represented by the peripheral speed of the photosensitive drum 1. In this embodiment, the low speed and normal speed of the intermediate transfer belt 30 and developing roller 41 are approximately the same as the low speed and normal speed of the photosensitive drum 1. The starting speed in Table 1 is the target rotational speed (peripheral speed) of the photosensitive drum 1 when the drum motor 21 is started.

[0053] [Table 1]

[0054] At all startup speeds, the maximum load torque at startup increases with increasing idle time. After 150 hours or more of idle time, the maximum load torque tends to converge to a predetermined value. The maximum load torque at a startup speed of 100 mm / s, even after the convergence, is at the same level as the maximum load torque at a startup speed of 300 mm / s with an idle time of 0 hours. As shown in Figure 6, the load torque is highest just before the developer supply process. In this embodiment, the peak value of the load torque can be reduced by driving at a low speed in that region. As a result, it is not necessary to increase the load capacity torque, making it possible to reduce the motor size.

[0055] Next, using Figure 7, we will further explain the operation when the load torque is determined to be low in S107 of Figure 5. Figure 7 is a chart similar to Figure 3 for explaining the operation when the load torque is determined to be low in the printing process after a long period of inactivity.

[0056] The process up to the load torque detection step in Figure 7 is the same as in Figure 6. If the CPU 101 determines that the load torque TM1 (kgf / cm) detected in the load torque detection step is smaller than a predetermined threshold TTH1, that is, that the load torque is low, it increases the rotation speed of the belt motor 23, drum motor 21, and developing motor 22 to the normal speed. Then, once the rotation speeds of the intermediate transfer belt 30, photosensitive drum 1Y~1K, and developing roller 41Y~41K have all converged to the normal speed, the CPU 101 performs the developing contact step, belt contact step, and image formation step in the same way as the normal printing process described above.

[0057] <Conventional printing process after long-term storage> Next, as a comparative example, a printing process in which the developer supply process is always performed after a long period of storage will be described. In addition, elements of the comparative image forming apparatus that have the same or corresponding functions or configurations as those of the image forming apparatus in this embodiment will be denoted by the same reference numerals as those of the image forming apparatus in this embodiment. The configuration and operation of the comparative image forming apparatus 100 are the same as those of the image forming apparatus 100 in this embodiment, except that the printing process after a long period of storage is different, as will be described below.

[0058] Figure 8 is a flowchart illustrating the general steps of the printing process in the comparative example.

[0059] When the CPU 101 receives a full-color print command from an external device, it first determines whether the device is in a state of long-term inactivity using the same method as in Figure 5 (S201). If the CPU 101 determines in S201 that the device is not in a state of long-term inactivity ("No"), it performs the aforementioned normal printing process, namely the normal speed start-up process (S202), the belt contact process and the developer contact process (S203), and the image formation process (S204), and then terminates the printing process. If the CPU 101 determines in S201 that the device is in a state of long-term inactivity ("Yes"), it starts the drum motor 21 and the developer motor 22 at normal speed (normal speed start-up process) (S205). Then, after executing the developer supply process (S206), the CPU 101 stops all operations of the photosensitive drum 1 and the developer device 4 (stop process) (S207). Subsequently, the CPU 101 performs the aforementioned normal printing process, namely the normal speed startup process (S202), the belt contact process and the development contact process (S203), and the image formation process (S204), and then completes the printing process.

[0060] Next, using Figure 9, we will further explain the operation when it is determined that the product has been left unattended for a long period of time in S201 of Figure 8. Figure 9 is a chart similar to Figure 3 for explaining the operation of the printing process after being left unattended for a long period of time in the comparative example.

[0061] If the CPU 101 determines that the machine has been left idle for a long period of time, it starts the drum motor 21 and the developing motor 22 at their normal speed (start-up process). Next, when the rotation speeds of the photosensitive drums 1Y~1K and the developing rollers 41Y~41K have all converged to their normal speeds, the CPU 101 brings the photosensitive drums 1Y~1K and the developing rollers 41Y~41K into contact (development contact process). After the CPU 101 has performed the developer supply process for a predetermined amount of time, it proceeds to the stop process described above. That is, the CPU 101 separates the photosensitive drums 1Y~1K and the developing rollers 41Y~41K and stops the drum motors 21 and the developing motors 22.

[0062] <Comparison of required time and load torque between comparative example and this embodiment> Next, we will compare and explain the time required until the completion of the printing process and the load torque when the image forming apparatus 100 receives a print instruction after being left idle for a long period of time, using the comparative example described above and this embodiment.

[0063] Table 2 shows the time required for each step until the end of the printing process and the maximum load torque for the comparative example and this embodiment described above. The time required for starting up individual motors is as follows.

[0064] The motor starts and stops at low speed, each taking 0.3 seconds; starts and stops at normal speed, each taking 0.5 seconds; increases from low speed to normal speed, taking 0.3 seconds; load torque is detected, taking 0.1 seconds; contact between the photosensitive drum 1Y~1K and the intermediate transfer belt 30, taking 0.5 seconds; contact and separation between the photosensitive drum 1Y~1K and the developing rollers 41Y~41K, each taking 0.4 seconds; developer is supplied at low speed, taking 10 seconds; and developer is supplied at normal speed, taking 3.4 seconds.

[0065] The required times in Table 2 were calculated based on these values, determining the time for each process in Figures 3, 6, 7, and 9. The maximum load torque values ​​are all obtained after sufficient time of inactivity and are for high-temperature, high-humidity environments (30°C, 80%RH). The low detected load torque values ​​in this embodiment are for normal temperature and humidity environments (25°C, 50%RH).

[0066] [Table 2]

[0067] In this embodiment, when the image forming apparatus 100 receives a print command after being left idle for a long period of time, a load torque detection step is performed, and whether or not to perform the developer supply step is determined according to the result. As a result, unlike the comparative example, the developer supply step can be skipped if the load torque is low.

[0068] As a result, as shown in Table 2, in the comparative example, the time required to start image formation for the developer supply process is always extended after prolonged storage, whereas in this embodiment, even after prolonged storage, the developer supply process is not performed if the load torque is low. Therefore, in this embodiment, even after prolonged storage, if the load torque is low, the time required to start image formation for the developer supply process is not extended, and the opportunities for FPOT (First Printout Time) to be extended can be reduced. Although the time required for the printing process is longer when the detected load torque is high, this is only in limited cases such as high temperature and high humidity environments, and in most cases after prolonged storage, the time required for the printing process can be reduced.

[0069] Furthermore, the relationship between the comparative example and this embodiment regarding the extension time is the same for developer consumption. In other words, in this embodiment, the developer supply process is not performed when the load torque is not high, thus reducing the consumption of excess developer.

[0070] Furthermore, in this embodiment, by starting the motor at a low speed, the maximum load torque can be reduced, ensuring stable operation while allowing for a smaller motor size compared to the comparative example. As a guideline, while the comparative example requires a motor with a load torque of 14 kgf / cm, this embodiment can use a motor with a load torque of around 7 kgf / cm.

[0071] Thus, in this embodiment, the image forming apparatus 100 includes a rotatable image carrier 1, a developing member 41 that supplies developer to the surface of the image carrier 1, transfer devices 6, 30, and 7 that transfer the image formed with developer on the surface of the image carrier 1 to a recording material P, a cleaning member 51 that contacts the surface of the image carrier 1 to form a contact area G and cleans the surface of the image carrier 1 at the contact area G, a control unit 101 capable of controlling the image forming operation to form an image to be transferred to the recording material P on the surface of the image carrier 1, and the supply operation to supply developer supplied from the developing member 41 to the image carrier 1 to the contact area G by the rotation of the image carrier 1, and a drive unit capable of driving the image carrier 1 at a first rotational speed and a second rotational speed. The control unit 101 includes a drive unit 21, the first rotational speed being at least one rotational speed during the image forming operation, and a second rotational speed being lower than the first rotational speed, and a torque detection unit 80 that detects information regarding the load torque while the image carrier 1 is rotating. When an instruction to start the image forming operation is input while the image carrier 1 is stopped, the control unit 101 starts the drive unit 21 to rotate the image carrier 1 at the second rotational speed, and acquires the detection result of the torque detection unit 80 while the image carrier 1 is rotating at the second rotational speed. Based on the detection result of the torque detection unit 80, the control unit 101 can decide whether or not to perform a supply operation before the image forming operation. In this embodiment, the control unit 101 controls the system to perform a supply operation before the image forming operation if the load torque indicated by the detection result of the torque detection unit 80 is above a predetermined threshold. In this embodiment, the control unit 101 also controls the system to stop the image carrier 1 after the supply operation before performing the image forming operation. In this embodiment, the drive unit 21 drives the image carrier 1 at a rotational speed less than or equal to the rotational speed during image formation during the supply operation. In this embodiment, the image forming apparatus 100 has an acquisition unit 104 that acquires information about the time the image carrier 1 is stopped between the completion of the image forming operation and the next time the start instruction is input to the control unit 101. When the control unit 101 receives a start instruction for the image forming operation while the image carrier 1 is stopped, it controls the torque detection unit 80 to detect information about the load torque if the time indicated by the acquisition result of the acquisition unit 104 is greater than or equal to a predetermined threshold. In this embodiment, the cleaning member 51 is a cleaning blade.In this embodiment, the image forming apparatus 100 has a switching unit (developing contact / separation mechanism) 60 that switches the state of the developing member 41 between a first state in which the developing member 41 supplies developer to the image carrier 1 and a second state in which it does not supply developer. The control unit 101 controls the developing member 41 to the first state using the switching unit 60 when supplying developer, and controls the developing member 41 to the second state using the switching unit 60 when the torque detection unit 80 detects information regarding the load torque. In this embodiment, the switching unit 60 switches the state of the developing member 41 between a first state in which the developing member 41 is in contact with the image carrier 1 and a second state in which the developing member 41 is separated from the image carrier 1.

[0072] As explained above, in this embodiment, even after being left idle for a long time, the developer supply process is not executed if the motor load torque is low. This prevents the consumption of excess developer and unnecessary interruptions in image formation. In other words, according to this embodiment, when the printing process is executed after the photosensitive drum 1 has been stopped and left idle for a long time, the opportunity for interruptions in image formation that extend FPOT can be reduced. Furthermore, according to this embodiment, while ensuring stable driving, the peak value of the load torque of the drum motor 21 can be reduced, thereby suppressing the need to increase the size of the motor. Thus, according to this embodiment, it is possible to effectively execute the developer supply process while suppressing the consumption of excess developer and interruptions in image formation, while suppressing the need to increase the size of the motor that drives the photosensitive drum 1.

[0073] [Example 2] Next, other embodiments of the present invention will be described. The basic configuration and operation of the image forming apparatus in this embodiment are the same as those of the image forming apparatus in Embodiment 1. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus in Embodiment 1 are denoted by the same reference numerals as in Embodiment 1, and detailed descriptions are omitted.

[0074] In this embodiment, the photosensitive drum 1 is not stopped after the developer supply process is completed. Instead, the rotation speed of the photosensitive drum 1 is changed to the rotation speed used during the image formation operation, and the image formation operation is performed. This allows for further time reduction compared to Embodiment 1. The printing process after long-term storage in this embodiment will now be described.

[0075] Figure 10 is a flowchart illustrating the general procedure of the printing process in this embodiment.

[0076] When the CPU 101 receives a full-color print command from an external device, it first determines whether the machine has been left idle for a long period of time in the same manner as in Figure 5 (S301). If the CPU 101 determines in S301 that the machine has been left idle for a long period of time ("Yes"), it proceeds to the printing process after the long period of idle time. Specifically, the CPU 101 starts the belt motor 23, drum motor 21, and developing motor 22 at a low speed (low-speed start-up process) (S305). The CPU 101 also uses the torque detection unit 80 to detect the load torque when the rotational speed of the photosensitive drum 1Y~1K is stable at a low speed (load torque detection process) (S306). Next, the CPU 101 determines whether the detected load torque is above a predetermined threshold (S307). In this embodiment, the predetermined threshold for load torque is set to 3 (kgf / cm). If the CPU 101 determines in S307 that the load torque is high ("Yes"), it brings the developing rollers 41Y~41K into contact with the photosensitive drums 1Y~1K (developing contact process) (S308). Then, with the developing rollers 41Y~41K in contact with the photosensitive drums 1Y~1K, the CPU 101 executes a developer supply process in which it rotates the photosensitive drums 1Y~1K for a predetermined amount of time (S309). Next, the CPU 101 increases the rotation speed of the drum motor 21 and the developing motor 22 to normal speed, and starts the belt drive motor 23, which was stopped when the developer supply process started, at normal speed, similar to Example 1 (S310). After that, the CPU 101 brings the intermediate transfer belt 30 into contact with the photosensitive drums 1Y~1K (belt contact process) (S311), performs the image formation process (S304), and finishes the printing process. On the other hand, if CPU 101 determines in S307 that the load torque is low ("No"), it performs steps S312, S303, and S304, similar to steps S111, S103, and S104 in Figure 5, and terminates the printing process.

[0077] Furthermore, if the CPU 101 determines in S301 that the machine is not in a state of prolonged inactivity ("No"), it controls the machine as follows: It performs the aforementioned normal printing process, namely the normal speed startup process (S302), the belt contact process and the development contact process (S303), and the image formation process (S304), and then terminates the printing process.

[0078] Thus, in this embodiment, after the supply operation, the control unit 101 controls the image carrier 1 to change its rotation speed to the rotation speed used during the image forming operation without stopping the image carrier 1, and then performs the image forming operation.

[0079] Here, we will further explain the operation when the load torque is determined to be high in S307 of Figure 10, using Figure 11. Figure 11 is a chart similar to Figure 6 in Example 1, used to explain the operation when the load torque is determined to be high in the printing process after a long period of inactivity in this embodiment.

[0080] The process up to the completion of the developer supply process in Figure 11 is the same as in Figure 6 of Example 1. However, in this example, when the developer supply process is completed, the CPU 101 restarts the belt motor 23 to normal speed in preparation for the image forming process. After that, the CPU 101 moves to a speed increase process to increase the speed of the drum motor 21 and the developer motor 22 to normal speed, and then moves to a belt contact process to bring the photosensitive drums 1Y~1K into contact with the intermediate transfer belt 30. Then, the CPU 101 performs the normal image forming process starting from timing LR1, when this contact operation is completed.

[0081] Table 3 shows a comparison of the time required in Example 1, where the photosensitive drum 1 and other components are temporarily stopped when transitioning to the image formation operation after the developer supply process is completed, and in this example, where they are not temporarily stopped.

[0082] [Table 3]

[0083] In this embodiment, after the developer supply process is completed, the photosensitive drum 1 is not stopped, but the rotation speed of the photosensitive drum 1 is changed to the rotation speed used during the image formation operation, and the image formation operation is performed. As a result, as shown in Table 3, the FPOT extension time can be shortened.

[0084] [Example 3] Next, other embodiments of the present invention will be described. The basic configuration and operation of the image forming apparatus in this embodiment are the same as those of the image forming apparatuses in Embodiments 1 and 2. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatuses in Embodiments 1 and 2 are denoted by the same reference numerals as in Embodiments 1 and 2, and detailed descriptions are omitted.

[0085] In this embodiment, the lower the load torque detected in the load torque detection step, the less developer is supplied (and the shorter the supply time) in the developer supply step. This reduces the consumption of excess developer in this embodiment. The printing process after long-term storage in this embodiment will be described below.

[0086] Figure 12 is a flowchart illustrating the general procedure of the printing process in this embodiment.

[0087] In this embodiment, the CPU 101 determines whether the load torque detected in the load torque detection step is high or low, and then executes a supply time determination step (S408) to determine the supply time in the developer supply step. The CPU 101 then executes the developer supply step (S410) for the determined supply time. The other operations are the same as those in Figure 10 of Embodiment 2. In other words, the operations S401-S407, S409, and S411-S413 in Figure 12 are the same as the operations S301-S307, S308, and S310-S312 in Figure 10, respectively.

[0088] Thus, in this embodiment, the control unit 101 can change the amount of developer supplied to the contact part G during the supply operation based on the detection result of the torque detection unit 80.

[0089] Here, the supply time determination process for S408 in Figure 12 will be explained using Table 4 and Figure 13. Figure 13 is a chart showing the changes in load torque when the developer supply process is performed when the load torque in each region is highest, with the load torque values ​​judged to be high divided into three regions, regions 1, 2, and 3, as shown in Table 4. As shown in Figure 13, by setting supply times of 6s, 7.8s, and 10s in regions 1, 2, and 3, respectively, the load torque immediately after the developer supply process can be reduced to 1.4 kgf / cm or less. Therefore, in this embodiment, as shown in Table 4, different supply times were set according to the value of the load torque TM1 (kgf / cm) detected in the load torque detection process.

[0090] [Table 4]

[0091] In this embodiment, the lower the load torque detected in the load torque detection step, the shorter the supply time, thereby reducing the consumption of excess developer.

[0092] Alternatively, the load torque may be detected in real time during the developer supply process, and the developer supply process may be terminated when the load torque drops to a predetermined value. This also yields the same effects as in this embodiment.

[0093] [Example 4] Next, other embodiments of the present invention will be described. The basic configuration and operation of the image forming apparatus in this embodiment are the same as those of the image forming apparatuses in Embodiments 1 to 3. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatuses in Embodiments 1 to 3 are denoted by the same reference numerals as in Embodiments 1 to 3, and detailed descriptions are omitted.

[0094] In this embodiment, the lower the load torque detected in the load torque detection step, the faster the rotation speed (supply speed) of the photosensitive drum 1 and other components in the developer supply step. This reduces the interruption time for image formation. The printing process after long-term storage in this embodiment will be described below.

[0095] Figure 14 is a flowchart illustrating the general procedure of the printing process in this embodiment.

[0096] In this embodiment, after determining the level of the load torque detected in the load torque detection step, the CPU 101 executes a supply speed and supply time determination step (S508) which determines the rotation speed (supply speed) of the photosensitive drum 1 in the developer supply step, in addition to the supply time described in Embodiment 3. Then, the CPU 101 executes an acceleration step (S509) to increase the supply speed to the determined supply speed, and also executes a developer supply step (S511) at the determined supply speed for the duration of the supply time. The other operations are the same as those in Figure 12 in Embodiment 3. In other words, the operations S501~S507, S510, S512~S514 in Figure 14 are the same as the operations S401~S407, S409, S411~S413 in Figure 12, respectively.

[0097] Here, we will further explain the operation when the load torque is determined to be high at S507 in Figure 14, using Figure 15. Figure 15 is a chart similar to Figure 6 in Example 1, used to explain the operation when the load torque is determined to be high in the printing process after a long period of inactivity in this embodiment.

[0098] Up to the load torque detection step shown in Figure 15, the process is the same as in Figure 6 of Example 1. If the CPU 101 determines that the load torque detected in the load torque detection step is high, it increases the rotational speed of the drum motor 21 and the developing motor 22 to the supply speed, and then brings the photosensitive drum 1Y~1K into contact with the developing rollers 41Y~41K (developing contact step). Once the CPU 101 moves to the speed increase step to the supply speed, it no longer needs to drive the belt motor 23, so it stops the belt motor 23. After that, the CPU 101 performs the developer supply step for the predetermined time determined as described above. When the developer supply step is completed, the CPU 101 restarts the belt motor 23 to normal speed in preparation for the image forming step. After that, the CPU 101 increases the speed of the drum motor 21 and the developing motor 22 to normal speed, and then brings the photosensitive drum 1Y~1K into contact with the intermediate transfer belt 30 (belt contact step). Then, the CPU 101 performs the normal image formation process starting from timing LR1, when this contact operation is completed.

[0099] Here, using Table 5, we will explain the process for determining the supply speed and supply time in S508 of Figure 14.

[0100] First, let's explain the supply speed. Based on Table 1 shown in Example 1, we can see the following: In other words, if the starting speed (target speed of the rotational speed (peripheral speed) of the photosensitive drum 1 when the drum motor 21 is started) is 100 mm / s and the load torque value is 4.5 kgf / cm or less, then even if the starting speed is 160 mm / s, the load torque value will be 6.3 kgf / cm or less. Therefore, in this case, it is possible to drive even with a motor with a load torque capacity of 7 kgf / cm. Also, in the developer supply process, the amount of developer supplied per unit area of ​​the surface of the photosensitive drum 1 is constant, so in order to finish supplying the same amount of developer quickly, it is better to have a rotational speed (peripheral speed) of the photosensitive drum 1 as fast as possible. Therefore, in this embodiment, as shown in Table 5, different supply speeds were set according to the value of the load torque TM1 (kgf / cm) detected in the load torque detection process. Table 5 shows the peripheral speed of the photosensitive drum 1 as the supply speed, but the peripheral speed of the developing roller 41 is also set in accordance with the peripheral speed of the photosensitive drum 1 (approximately the same peripheral speed as the photosensitive drum 1).

[0101] [Table 5]

[0102] Next, we will explain the supply time. Table 6 shows the supply time when the supply speed is set as shown in Table 5 (this embodiment) and when the supply speed is set to 100 mm / s regardless of the load torque detection result from the load torque detection process (Embodiment 3).

[0103] [Table 6]

[0104] In Table 6, the supply time value when the supply speed is fixed at 100 mm / s (Example 3) is the same as the value in Table 4, which shows the case where the developer supply process is performed at a low speed. The supply time value in Table 6 for this example is calculated from the supply speed in Table 5 to supply the same amount of developer as in that case. When the load torque TM1 (kgf / cm) detected in the load torque detection process is 3 ≤ TM1 < 4.5, this example is able to shorten the supply time compared to Example 3 because the supply speed is faster.

[0105] Thus, in this embodiment, the drive unit 21 can drive the image carrier 1 at a rotational speed greater than or equal to the rotational speed at which the torque detection unit 80 detects information regarding the load torque during the supply operation. Furthermore, in this embodiment, the drive unit 21 can drive the image carrier 1 at a first rotational speed and a third rotational speed lower than the first rotational speed during image formation, and the second rotational speed at startup is less than or equal to the third rotational speed. In addition, in this embodiment, the control unit 101 can change the rotational speed of the image carrier 1 during the supply operation based on the detection result of the torque detection unit 80.

[0106] In this embodiment, the lower the load torque detected in the load torque detection step, the faster the supply speed can be increased, thereby shortening the interruption time for image formation due to the developer supply step and reducing the time until image formation can begin.

[0107] [Example 5] Next, other embodiments of the present invention will be described. The basic configuration and operation of the image forming apparatus in this embodiment are the same as those of the image forming apparatuses in Embodiments 1 to 4. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatuses in Embodiments 1 to 4 are denoted by the same reference numerals as in Embodiments 1 to 4, and detailed descriptions are omitted.

[0108] In this embodiment, the interruption time for image formation is reduced by determining whether or not to execute the developer supply process based on the process speed during image formation (hereinafter also referred to as "image formation speed"). In this embodiment, the image forming apparatus 100 is provided with four types of image formation speeds (peripheral speed of the photosensitive drum 1): 100 mm / s (corresponding to the low speed mentioned above), 160 mm / s, 240 mm / s, and 300 mm / s (corresponding to the normal speed mentioned above). The printing process after long-term storage in this embodiment will be described below.

[0109] Figure 16 is a flowchart illustrating the general procedure of the printing process in this embodiment.

[0110] In this embodiment, after determining whether the load torque detected in the load torque detection step is high or low, the CPU 101 executes a step (S608) to determine whether the image formation speed of the printing process is the speed required by the developer supply process. The other operations are the same as those in Figure 14 of Embodiment 4. In other words, the operations S601-S607 and S609-S615 in Figure 16 are the same as the operations S501-S507 and S508-S514 in Figure 14, respectively. In this embodiment, instead of the normal speed in Embodiment 4, the machine is driven by the image formation speed of the printing process (S602, S613, S615).

[0111] Thus, in this embodiment, the control unit 101 can determine whether or not to perform a supply operation before starting the image forming operation, based on the detection result of the torque detection unit 80 and the setting of the rotation speed of the image carrier 1 during the image forming operation.

[0112] The operation when the load torque is determined to be high in S607 of Figure 16 will be further explained. If the CPU 101 determines that the load torque detected in the load torque detection step is high, it proceeds to the step of determining whether the image formation speed of the printing process is the speed required for the developer supply process (S608). If the CPU 101 determines in S608 that the speed is not the speed required for the developer supply process ("No"), it performs the same operation as when the load torque is determined to be low in S607. On the other hand, if the CPU 101 determines in S608 that the speed is the speed required for the developer supply process ("Yes"), it performs the same operation as from S508 onwards in Figure 14. The detailed operation in this case is the same as the operation explained using Figure 15 in Example 4, and the determined supply speed and supply time are applied. Note that in increasing the speed to the image formation speed (S613, S615), if the image formation speed is the same as the low speed of 100 mm / s, the speed is maintained without increasing the speed.

[0113] Here, using Table 7, we will further explain the process of determining whether the image formation speed in S608 of Figure 16 is a speed that requires the developer supply process. As mentioned above, based on Table 1 shown in Example 1, if the image formation speed is set as shown in Table 7, it is possible to drive with a motor with a load torque of 7 kgf / cm without performing the developer supply process. Therefore, in this embodiment, as shown in Table 7, the maximum value of the image formation speed at which the developer supply process does not require is set according to the value of the load torque TM1 (kgf / cm) detected in the load torque detection process, even if it is determined that the load torque is high.

[0114] [Table 7]

[0115] Thus, even when the image formation speed is high, a developer supply process is necessary. However, when the image formation speed is low and the load torque detected in the load torque detection process is small, printing may be possible without performing the developer supply process. Taking this into consideration, in this embodiment, the decision of whether or not to perform the developer supply process is made based on the image formation speed. This reduces the conditions under which the developer supply process is performed, and consequently reduces the frequency of the developer supply process, thereby reducing the interruption time during image formation and the consumption of excess developer.

[0116] The reason for increasing the supply speed as much as possible according to the load torque detection result in the load torque detection process is that this reduces the interruption time of image formation due to the developer supply process, thereby shortening the time until image formation can begin.

[0117] [others] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the embodiments described above.

[0118] In the above-described embodiment, the image forming apparatus was explained as employing an intermediate transfer method, but the present invention can also be applied to an image forming apparatus employing a direct transfer method. As is well known to those skilled in the art, a tandem image forming apparatus employing a direct transfer method has a recording material carrier composed of an endless belt or the like, instead of the intermediate transfer body in the above-described embodiment. The toner image formed on the image carrier of each image forming unit is then directly transferred to the recording material carried and transported on the recording material carrier, in the same manner as the primary transfer in an image forming apparatus employing an intermediate transfer method. Even in such an image forming apparatus, the same effects as in the above-described embodiment can be obtained by applying the present invention in accordance with the above-described embodiment.

[0119] Furthermore, although the above-described embodiment used a full-color image forming apparatus as an example, the present invention can also be applied to a mono-color image forming apparatus, and the same effects as those described in the above-described embodiment can be obtained.

[0120] Furthermore, in the above-described embodiment, as an example of a method for switching between a state in which developer can be supplied to the image carrier and a state in which it cannot be supplied, an example of a contact development method was shown in which the two states can be switched by bringing the photosensitive drum 1 and the developing roller 41 into contact and separating. However, the present invention is not limited to this, and a non-contact development method in which similar switching can be performed by developing voltage may also be used. In that case as well, the same effect can be obtained by supplying approximately the same amount of developer as in the above-described embodiment in the developer supply process. In this case, the switching unit is configured by a developing power supply that switches the developing voltage.

[0121] Furthermore, in the above-described embodiment, the system was configured to determine whether or not it had been left idle for a long period of time, and if so, the load torque was detected. However, it is also possible to start the system at a low speed and detect the load torque without determining whether or not it had been left idle for a long period of time.

[0122] Furthermore, in the above-described embodiment, the time of the developer supply process was adjusted when adjusting the amount of developer supplied in the developer supply process. However, if, for example, a strip-shaped toner image is formed in the developer supply process, the adjustment may be made by changing the size or density of the toner image.

[0123] Furthermore, although the above-described embodiment was explained as using the value of the load torque for control, similar control can be performed using any index value that correlates with the load torque, such as the value of the motor's drive current.

[0124] Furthermore, the above-described embodiment described the case where the cleaning member is a plate-shaped (blade-shaped) member. In this case, the coefficient of friction between the image carrier and the cleaning member tends to increase after prolonged storage, so the effects of the present invention are particularly pronounced. However, the present invention is not limited to this embodiment, and the same effects as the above-described embodiment can be obtained by applying the present invention as long as the cleaning member has a component that contacts the image carrier and has the potential to increase the coefficient of friction between it and the image carrier after prolonged storage. The cleaning member may be, for example, a flexible sheet-shaped member, a brush-shaped member that is fixedly or rotatably arranged, or a block-shaped member made of sponge rubber or the like. [Explanation of Symbols]

[0125] 1 Photosensitive drum 4. Developing device 5. Cleaning device 6. Primary transfer roller 7. Secondary transfer roller 30 Intermediate transfer belt 41 Developing Roller 51 Cleaning Blade 100 Image forming apparatus

Claims

1. A rotatable image carrier; a developing member for supplying a developer to a surface of the image carrier; a transfer device that transfers an image formed on the surface of the image carrier with a developer onto a recording material; a cleaning member that comes into contact with a surface of the image carrier to form a contact portion and cleans the surface of the image carrier at the contact portion; a control unit capable of controlling an image forming operation for forming an image to be transferred to the recording material on a surface of the image carrier, and a supplying operation for supplying the developer supplied from the developing member to the image carrier to the contact portion by rotation of the image carrier; a drive unit capable of driving the image carrier at a first rotation speed and a second rotation speed, the first rotation speed being at least one rotation speed during the image forming operation, and the second rotation speed being a rotation speed lower than the first rotation speed; a torque detection unit that detects information regarding a load torque during rotation of the image carrier; having an image forming apparatus characterized in that, when an instruction to start the image forming operation is input while the image carrier is stopped, the control unit starts the drive unit to rotate the image carrier at the second rotational speed, obtains a detection result of the torque detection unit while the image carrier is rotating at the second rotational speed, and is capable of determining whether or not to perform the supply operation before the image forming operation based on the detection result of the torque detection unit.

2. 2. The image forming apparatus according to claim 1, wherein the control unit controls the supply operation to be performed before the image forming operation when the load torque indicated by the detection result of the torque detection unit is equal to or greater than a predetermined threshold value.

3. 2. The image forming apparatus according to claim 1, wherein the control section controls the image carrier to stop once after the supplying operation, and then performs the image forming operation.

4. The image forming apparatus according to claim 1, wherein the control unit controls the image forming operation after the supply operation so that the rotation speed of the image carrier is changed to the rotation speed during the image forming operation without stopping the image carrier.

5. 2. The image forming apparatus according to claim 1, wherein the drive section drives the image carrier at a rotation speed during the supplying operation that is equal to or lower than a rotation speed during the image forming operation.

6. 2 . The image forming apparatus according to claim 1 , wherein the drive section drives the image carrier at a rotation speed during the supply operation that is equal to or higher than a rotation speed at which the torque detection section detects information regarding the load torque.

7. 2. The image forming apparatus according to claim 1, wherein the drive unit is capable of driving the image carrier at the first rotational speed and a third rotational speed lower than the first rotational speed during the image forming operation, and the second rotational speed is a rotational speed lower than or equal to the third rotational speed.

8. 8. The image forming apparatus according to claim 1, wherein the control unit is capable of changing an amount of developer supplied to the contact portion in the supplying operation based on a detection result of the torque detection unit.

9. 8. The image forming apparatus according to claim 1, wherein the control unit is capable of changing a rotation speed of the image carrier during the supply operation based on a detection result of the torque detection unit.

10. The image forming apparatus according to any one of claims 1 to 7, characterized in that the control unit is capable of determining whether or not to perform the supply operation before starting the image forming operation based on the detection result of the torque detection unit and a setting of the rotation speed of the image carrier during the image forming operation.

11. an acquisition unit that acquires information regarding a time during which the image carrier is stopped from the time when the image forming operation is completed until the start instruction is input to the control unit again; The image forming apparatus according to any one of claims 1 to 7, characterized in that when an instruction to start the image forming operation is input while the image carrier is stopped, the control unit controls the torque detection unit to detect information regarding the load torque if the time indicated by the acquisition result of the acquisition unit is equal to or longer than a predetermined threshold value.

12. 8. The image forming apparatus according to claim 1, wherein the cleaning member is a cleaning blade.

13. a switching unit that switches a state of the developing member between a first state in which the developing member supplies a developer to the image carrier and a second state in which the developing member does not supply a developer, 8. The image forming apparatus according to claim 1, wherein the control section controls the switching section to set the developing member to the first state during the supplying operation.

14. a switching unit that switches a state of the developing member between a first state in which the developing member supplies a developer to the image carrier and a second state in which the developing member does not supply a developer, 8. The image forming apparatus according to claim 1, wherein the control unit controls the switching unit to bring the developing member into the second state when the torque detection unit detects information regarding the load torque.

15. 14. The image forming apparatus according to claim 13, wherein the switching unit switches the state of the developing member between the first state in which the developing member is in contact with the image carrier and the second state in which the developing member is separated from the image carrier.

16. 15. The image forming apparatus according to claim 14, wherein the switching unit switches the state of the developing member between the first state in which the developing member is in contact with the image carrier and the second state in which the developing member is separated from the image carrier.

Images