Image forming apparatus

Abstract

After detecting that the rotational load torque of the driven member has exceeded a predetermined value, the system can maintain that detection state even if the rotational load torque of the driven member falls below that predetermined value. [Solution] The image forming apparatus comprises a driven member, a first rotating body, a second rotating body which is rotated by the first rotating body and is rotatable relative to the first rotating body from a first phase to a second phase relative to the first rotating body, and a detection means capable of detecting when the second rotating body is in the second phase. The first and second rotating bodies rotate in the first phase when the rotational load torque of the driven member is the first torque, and in the second phase when the second torque is greater than the first torque. The image forming apparatus also has a restricting means that restricts the return from the second phase to the first phase, even if the rotational load torque of the driven member decreases from the second torque to the first torque when it changes from the first phase to the second phase.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus such as a printer, a copier, a facsimile apparatus, or a multifunction peripheral having a plurality of functions among these functions, using an electrophotographic method or an electrostatic recording method.

Background Art

[0002] In an image forming apparatus such as a printer using an electrophotographic method, after transferring a toner image from an image carrier to a transfer body, waste toner such as toner remaining on the image carrier is removed from the image carrier by cleaning means and collected in a waste toner collection container.

[0003] In the waste toner collection container, a waste toner conveying screw as a waste toner conveying member may be provided to convey the waste toner to a predetermined position in the waste toner collection container or level the waste toner in the waste toner collection container. And between the waste toner conveying screw and a drive motor that rotationally drives the screw, torque detection means for detecting the rotational load torque of the waste toner conveying screw may be provided. By providing this torque detection means, when the waste toner in the waste toner collection container increases due to an increase in the number of sheets passed through the image forming apparatus and the rotational load torque of the waste toner conveying screw exceeds a predetermined value (overload state), this can be detected. Based on the detection result of this torque detection means, by notifying the user that the waste toner collection container is full or nearly full and prompting the replacement of the waste toner collection container, damage to the drive motor and the waste toner conveying screw, and overflow of waste toner from the waste toner collection container can be prevented.

[0004] Patent Document 1 discloses torque detection means configured to detect a phase difference between two rotating bodies provided coaxially and detect the rotational load torque based on the phase difference, which varies depending on the magnitude of the rotational load torque.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Patent No. 6729176 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, with the conventional torque detection means described above, once it detects that the rotational load torque of the waste toner transport screw has exceeded a predetermined value, the detection state is canceled if the rotational load torque temporarily falls below the predetermined value. In other words, the detection state that the waste toner collection container is full or nearly full is canceled.

[0007] For example, if the user operates the waste toner collection container, the state of the waste toner inside the container may change, causing the rotational load torque of the waste toner transport screw to fall below a predetermined value. If more waste toner is then collected in the waste toner collection container, the capacity of the container may be exceeded, potentially leading to damage to the drive motor or waste toner transport screw, or leakage of waste toner from the waste toner collection container.

[0008] Therefore, an object of the present invention is to enable the detection state to be maintained even when the rotational load torque of the driven member falls below a predetermined value, after the rotational load torque of the driven member has been detected to be above a predetermined value. [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 is an image forming apparatus comprising: a driven member; a drive source that generates a driving force to rotate the driven member; a first rotating body that rotates when the driving force from the drive source is input to it; a second rotating body provided coaxially with the first rotating body, which rotates when the driving force from the drive source is transmitted by the first rotating body and transmits the driving force toward the driven member, wherein the second rotating body is rotatable relative to the first rotating body from a first phase to a second phase, where the phases of the relative positions of the second rotating body with respect to the first rotating body in the rotation direction of the first rotating body are different; and detection means capable of detecting when the second rotating body is in the second phase, wherein the first rotating body and the second rotating body are The image forming apparatus is configured such that when the rotational load torque of the driven member is a first torque, the second rotating body rotates in the first phase, and when the rotational load torque of the driven member is a second torque greater than the first torque, the second rotating body rotates in the second phase, such that the phase changes as the rotational load torque of the driven member changes from the first torque to the second torque, and the apparatus has a restricting means that restricts the phase from returning from the second phase to the first phase even if the rotational load torque of the driven member decreases from the second torque to the first torque when the phase changes from the first phase to the second phase. [Effects of the Invention]

[0010] According to the present invention, therefore, an object of the present invention is to maintain the detection state even when the rotational load torque of the driven member falls below a predetermined value after detecting that the rotational load torque of the driven member has exceeded a predetermined rotational load torque. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view showing the overall configuration of the printer. [Figure 2] This is a cross-sectional view showing a printer with its door open. [Figure 3]It is a cross-sectional view showing a printer in a state where the fixing device has moved. [Figure 4] It is a cross-sectional view showing a printer in a state where the transfer unit and the tray unit are pulled out. [Figure 5] It is a cross-sectional view showing a printer in a state where the transfer unit is pulled out alone. [Figure 6] It is a perspective view showing the overall configuration of the transfer unit. [Figure 7] It is a perspective view of the transfer unit for explaining the conveyance path of waste toner. [Figure 8] It is a perspective view showing the conveyance path of waste toner and the drive connection mechanism. [Figure 9] It is a perspective view of the drive connection mechanism in Example 1. [Figure 10] It is an exploded perspective view of the drive connection mechanism in Example 1. [Figure 11] It is a perspective view and a front view of the movable gear and the fixed gear in Example 1. [Figure 12] It is a schematic diagram for explaining the operation of the drive connection mechanism in Example 1. [Figure 13] It is a perspective view for explaining the operation of the torque detection mechanism in Example 1. [Figure 14] It is a cross-sectional view for explaining the operation of the torque detection mechanism in Example 1. [Figure 15] It is a perspective view of the drive connection mechanism in Example 2. [Figure 16] It is an exploded perspective view of the drive connection mechanism in Example 2. [Figure 17(a)] It is a perspective view of the torque detection mechanism in Example 2. [Figure 17(b)] It is a perspective view of the torque detection mechanism in Example 2. [Figure 18] It is a cross-sectional view of the drive gear in Example 2. [Figure 19] It is a cross-sectional view of the driven gear in Example 2. [Figure 20] It is a cross-sectional view for explaining the operation of the torque detection mechanism in Example 2. [Figure 21] It is a perspective view showing the overall configuration of the torque detection mechanism in Example 3. [Figure 22] It is an exploded perspective view of the drive coupling mechanism in Example 3. [Figure 23] It is a perspective view of the first rotating body in Example 3. [Figure 24] It is a perspective view of the second rotating body in Example 3. [Figure 25] It is a cross-sectional view for explaining the operation of the torque detection mechanism in Example 3. [Figure 26] It is a perspective view of the torsion spring in Example 3. [Figure 27(a)] It is a front view for explaining the operation of the torque detection mechanism in Example 3. [Figure 27(b)] It is a front view for explaining the operation of the torque detection mechanism in Example 3. [Figure 28] It is a schematic diagram for explaining the operation of the torque detection mechanism in Example 3. [Figure 29] It is a block diagram showing the schematic control configuration of the printer.

Mode for Carrying Out the Invention

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

[0013] [Example 1] <Overall Configuration of the Image Forming Apparatus> Using FIG. 1, the overall configuration of the image forming apparatus of this embodiment will be described. FIG. 1 is a cross-sectional view showing the overall configuration of the image forming apparatus of this embodiment. In this embodiment, the image forming apparatus is a tandem type color laser beam printer (hereinafter simply referred to as "printer") 1 that adopts an intermediate transfer method and can form a full-color image on a sheet S using an electrophotographic method.

[0014] Regarding printer 1 and its elements, the right side in Figure 1 is referred to as the "front" side, and the left side in Figure 1 is referred to as the "rear" side. Also, regarding printer 1 and its elements, the left side (the front of the paper in Figure 1) when viewed from the front of printer 1 is referred to as the "left" side, and the right side (the back of the paper in Figure 1) is referred to as the "right" side. The left-right direction connecting the left and right sides is assumed to be approximately parallel to the rotation axis direction of the photosensitive drum 61, which will be described later, and the rotation axis direction of the tension roller of the intermediate transfer belt 41, which will be described later. Furthermore, in this embodiment, printer 1 is positioned so that the front-back direction and the left-right direction are approximately parallel to the horizontal direction H, and is used for image formation. Also, regarding printer 1 and its elements, up and down refers to up and down in the direction of gravity (vertical direction) V, but does not mean only directly above and directly below, but also includes the sides above and below the horizontal plane passing through the position or element of interest. Furthermore, while sheet S is typically made of paper, and therefore sometimes referred to simply as paper, sheet S is not limited to paper. It can also be made of materials other than paper, such as plastic sheets, or materials containing materials other than paper.

[0015] The printer 1 comprises a main body (housing) 1a, a scanner 2 which is an exposure device as an exposure means, a control unit (control circuit) 3 as a control means, and a door 20 which is an opening / closing member that can be opened and closed relative to the main body 1a. The printer 1 also comprises a sheet feeding unit 30, a transfer unit 40 which is a transfer device (intermediate transfer device) as a transfer means, a tray unit 50 as a moving unit (support unit), and a fixing device 80 as a fixing means. The part including the main body 1a and the door 20 can also be called the main frame 1i. The main frame 1i includes the exterior of the printer 1.

[0016] The main unit 1a houses a scanner 2, a control unit 3, a sheet feeding unit 30, a transfer unit 40, a tray unit 50, and a fixing device 80.

[0017] The sheet feeding unit 30 includes a loading tray 31 for loading sheets S, which are sheet-shaped recording materials (transfer materials, recording media, paper), and a feeding roller 32 as a feeding member. The loading tray 31 can be pulled out from the main body 1a toward the door 20 (front side). Sheets S can then be replenished in the loading tray 31 that has been pulled out from the main body 1a.

[0018] The tray unit 50 includes a tray 51 as a support member (drawer) and four cartridges (image forming units) PY, PM, PC, and PK. The tray 51 has a tray handle 52. Each cartridge PY, PM, PC, and PK is removably mounted on the tray 51.

[0019] In this embodiment, each cartridge PY, PM, PC, and PK is independently removable from the tray 51. The four cartridges PY, PM, PC, and PK each form images (toner images) of yellow (Y), magenta (M), cyan (C), and black (K), respectively. The four cartridges PY, PM, PC, and PK each contain toner as a developer for yellow (Y), magenta (M), cyan (C), and black (K), respectively. In this embodiment, a one-component developer is used as the developer. Each cartridge PY, PM, PC, and PK has substantially the same configuration except for the color of the toner it contains. Elements with the same or corresponding functions or configurations provided for each of the yellow, magenta, cyan, and black colors may be described collectively by omitting the Y, M, C, and K at the end of the symbols indicating that they are elements for one of the colors. The tray unit 50 can be said to have a plurality of cartridges P and a tray 51 on which the plurality of cartridges P are removablely mounted.

[0020] In this embodiment, the tray unit 50 has a plurality of photosensitive drums 61 (61Y, 61M, 61C, 61K), a plurality of charging rollers 62 (62Y, 62M, 62C, 62K), and a plurality of developing rollers 71 (71Y, 71M, 71C, 71K). Specifically, the tray unit 50 has four photosensitive drums 61, four charging rollers 62, and four developing rollers 71. The photosensitive drum 61 is a rotatable drum-type (cylindrical) photoreceptor (electrophotographic photoreceptor) as a first image carrier. The charging rollers 62 are roller-type charging members as charging means. The developing rollers 71 are developer carriers (developing members) that carry toner in the toner storage section provided in the tray 51 or cartridge P and transport it toward the photosensitive drum 62. The rotation axis direction of the photosensitive drum 61, the rotation axis direction of the developing roller 71, and the rotation axis direction of the charging roller 62 are approximately parallel.

[0021] The parts that form the image for each color (including the photosensitive drum 61, charging roller 62, and developing roller 71) can also be called stations. The black cartridge PK is installed in the black station. The cyan cartridge PC is installed in the cyan station. The magenta cartridge PM is installed in the magenta station. The yellow cartridge PY is installed in the yellow station.

[0022] The photosensitive drum 61, the charging roller 62, and the developing roller 71 may be provided in either the cartridge P or the tray 51. In this embodiment, the cartridge P includes the photosensitive drum 61, the charging roller 62, and the developing roller 71. The tray unit 50 may also have a drum cleaning unit (drum cleaning device) as a photoreceptor cleaning means for removing toner from each photosensitive drum 61. In other words, the tray unit 50 may have multiple drum cleaning units that clean the surface of each photosensitive drum 16. The drum cleaning unit can be provided in either the cartridge P or the tray 51. For example, the drum cleaning unit uses a cleaning blade, which acts as a cleaning member that contacts the surface of the photosensitive drum 61, to scrape toner from the surface of the rotating photosensitive drum 61 and collect it in a recovered toner storage unit provided in the tray 51 or cartridge P.

[0023] The transfer unit 40 includes an intermediate transfer belt (hereinafter also simply referred to as "belt") 41, primary transfer rollers 42 (42Y, 42M, 42C, 42K), a cleaning unit 43, a drive roller 46, and tension rollers (driven rollers) 47. The belt 41 is an intermediate transfer body composed of an endless belt, serving as a second image carrier. The primary transfer rollers 42 are roller-type primary transfer members serving as primary transfer means. The cleaning unit (belt cleaning device) 43 is a cleaning means for cleaning the surface of the belt 41. The drive rollers 46 and tension rollers 47 are tension rollers that tension the belt 41. The drive rollers 46 drive the belt 41. The tension rollers 47 apply a predetermined tension to the belt 41. The drive roller 46 and tension roller 47 form a primary transfer surface 41a on the belt 41, which is the surface onto which the toner image is transferred from the photosensitive drums 61Y, 61M, 61C, and 61K.

[0024] In this embodiment, the printer 1 has an optical sensor 44 that detects the toner image transferred to the belt 41. In this embodiment, the belt 41 is positioned below each of the photosensitive drums 61Y, 61M, 61C, and 61K. The belt 41 is able to contact the photosensitive drum 61 so that a primary transfer portion is formed between the belt 41 and the photosensitive drum 61. The printer 1 also has a secondary transfer roller 45 positioned opposite the drive roller 46 via the belt 41. The secondary transfer roller 45 is a roller-type secondary transfer member that serves as a secondary transfer means. The secondary transfer roller 45 contacts the belt 41 so that a secondary transfer portion is formed between the belt 41 and the secondary transfer roller 45. The rotational axis direction of the primary transfer roller 42, the rotational axis direction of the drive roller 46, the rotational axis direction of the tension roller 47, and the rotational axis direction of the secondary transfer roller 45 are substantially parallel. In the conveying direction of the sheet S, a pair of registration rollers 4 are positioned in front of the secondary transfer portion as synchronous conveying members.

[0025] The fixing device 80 includes a fixing unit 81 and a flapper 5. The fixing device 80 is in the use position when the image forming operation is performed to form an image on the sheet S. The fixing device 80 is housed inside the main body 1a when it is in the use position. The fixing device 80 is also configured to heat the sheet S when it is in the use position. In this embodiment, the fixing unit 81 includes a heating unit (heating roller) including a heater and a pressurizing unit (pressure roller) that grips and conveys the sheet S together with the heating unit.

[0026] The movement of the transfer unit 40 and the tray unit 50 will be explained using Figures 1, 2, 3, 4, and 5. Figure 2 is a cross-sectional view showing the printer 1 with the door 20 open. Figure 3 is a cross-sectional view showing the printer 1 with the fuser 80 moved. Figure 4 is a cross-sectional view showing the printer 1 with the transfer unit 40 and the tray unit 50 pulled out from the main body 1a. Figure 5 is a cross-sectional view showing the printer 1 with the transfer unit 40 pulled out from the main body 1a by itself.

[0027] The transfer unit 40 and the tray unit 50 are movable from the inside to the outside of the device body 1a. In the horizontal direction H (front-to-back direction), the device body 1a has a first end 1b1 with a body opening 1a1, which is an opening, and a second end 1b2 on the opposite side of the first end 1b1. The tray unit 50 is movable through the body opening 1a1 to a first inner position inside the device body 1a and to a first outer position outside the device body 1a. The transfer unit 40 is movable through the body opening 1a1 to a second inner position inside the device body 1a and to a second outer position outside the device body 1a. The body opening 1a1 may be configured to have an opening through which the tray unit 50 passes and an opening through which the transfer unit 40 passes. When the transfer unit 40 moves from the second inner position to the second outer position, at least the belt 41 moves, and at least a part of the belt 41 protrudes from the device body 1a toward the outside of the device body 1a.

[0028] The direction in which the tray unit 50 moves from the first inner position to the first outer position is called the tray removal direction Dd1, and the direction opposite to the tray removal direction Dd1 is called the tray mounting direction Da1. The tray removal direction Dd1 can be described as the direction from the second end 1b2 to the first end 1b1. The direction in which the transfer unit 40 moves from the second inner position to the second outer position is called the transfer removal direction Dd2, and the direction opposite to the transfer removal direction Dd2 is called the transfer mounting direction Da2. In the transfer removal direction Dd2, the drive roller 46 is located downstream of the tension roller 47. The transfer removal direction Dd2 can be described as the direction from the second end 1b2 to the first end 1b1. The tray removal direction Dd1 and the tray mounting direction Da1 are directions that intersect (preferably approximately perpendicular) with the rotation axis direction of the photosensitive drum 61. The transfer removal direction Dd2 and the transfer mounting direction Da2 are directions that intersect (preferably approximately perpendicular) with the rotation axis direction of the drive roller 46. The rotation axis direction of the drive roller 46 is approximately parallel to the rotation axis direction of the photosensitive drum 61. In the horizontal direction H (front-to-back direction), the fixing device 80 is positioned on one end of the device body 1a (the side on which the first end 1b1 is located).

[0029] The door 20 attached to the main body 1a of the device is movable between a closed position and an open position. As shown in Figure 1, when the door 20 is in the closed position (closed state), the door 20 covers the opening 1a1 of the main body. As shown in Figure 2, when the door 20 is in the open position (open state), the opening 1a1 of the main body is exposed.

[0030] As shown in Figure 1, when the door 20 is in the closed position, the door 20 covers the fuser unit 80 attached to the main body 1a of the device. More specifically, when the door 20 is in the closed position, the upper cover portion 20b of the door 20 is located above the fuser unit 80. The upper cover portion 20b of the door 20 functions as part of the exterior of the printer 1.

[0031] The door 20 can move between an open position and a closed position while the fixing device 80 is supported by the device body 1a. In other words, the door 20 moves from the closed position to the open position so as to move away from the fixing device 80 supported by the device body 1a. Therefore, as shown in Figure 2, when the door 20 is in the open position, the door 20 is away from the fixing device 80 supported by the device body 1a.

[0032] As will be described later, the fixing device 80 is movable from the state shown in Figure 2 to the state shown in Figure 3 so that the main body opening 1a1 is widely exposed. With the door 20 and the fixing device 80 moved as shown in Figure 3, the transfer unit 40 and the tray unit 50 can move from the inside to the outside of the device body 1a through the main body opening 1a1, and after the movement, it will be in the state shown in Figure 4.

[0033] As shown in Figure 4, with the tray unit 50 moved outside the main body 1a of the device, it is permissible to remove each cartridge PY, PM, PC, and PK from the tray 51 and to attach each cartridge PY, PM, PC, and PK to the tray 51. This allows each cartridge PY, PM, PC, and PK to be replaced with a new cartridge PY, PM, PC, and PK, respectively. In this embodiment, cartridge P is detachable from the tray 51 in a direction that intersects (preferably approximately perpendicular to) the rotation axis of the photosensitive drum 61.

[0034] Each cartridge PY, PM, PC, and PK is removed from the tray 51 by moving it away from the transfer unit 40 relative to the tray 51. In other words, each cartridge PY, PM, PC, and PK is removed from the tray 51 by moving it away from the transfer unit 40 relative to the tray 51. In this embodiment, the transfer unit 40 is located below the tray unit 50. Therefore, each cartridge PY, PM, PC, and PK is removed from the tray 51 by moving it upward relative to the tray 51.

[0035] Furthermore, as shown in Figure 5, the transfer unit 40 can be removed from the main body 1a of the apparatus independently of the tray unit 50. This allows the transfer unit 40 to be replaced with a new one.

[0036] <Image Formation Process> The image formation operation of printer 1 will be explained using Figure 1. The control unit 3 of printer 1 starts an image formation operation to form an image on sheet S based on image information (image signal) received from an external host device 400. The external host device 400 is, for example, a personal computer, an image reader, or a facsimile machine.

[0037] When the image forming operation is performed, the fixing device 80 is in the operating position, the tray unit 50 is in the first inner position, the transfer unit 40 is in the second inner position, and the door 20 is in the closed position. With the transfer unit 40 in the second inner position, the belt 41 can contact each of the photosensitive drums 61Y, 61M, 61C, and 61K. At this time, the tray unit 50 is positioned above the transfer unit 40.

[0038] When the image forming operation starts, the photosensitive drum 61 is driven to rotate, and a charging voltage is applied to the charging roller 62. The photosensitive drum 61 is driven to rotate in a clockwise direction in Figure 1. The belt 41 is also driven to rotate. The belt 41 rotates (circumnavigates) in a counterclockwise direction in Figure 1 as the drive roller 46 is driven by the drive motor 5 (Figure 29) which acts as the drive source. The surface of the photosensitive drum 61 is uniformly charged to a predetermined potential with a predetermined polarity (negative polarity in this embodiment) by the charging roller 62. A laser corresponding to the image information is irradiated from the scanner 2 onto the charged surface of the photosensitive drum 61, and the surface of the photosensitive drum 61 is exposed. As a result, an electrostatic latent image (electrostatic image) corresponding to the image information is formed on the surface of the photosensitive drum 61.

[0039] In this embodiment, the developing roller 71 carries the toner in the toner storage section provided in the cartridge P. A developing voltage is applied to the developing roller 71, and toner is supplied from the developing roller 71 to the surface of the photosensitive drum 61 in accordance with the electrostatic latent image formed on the surface of the photosensitive drum 61. As a result, the surface of the photosensitive drum 61 is developed (visualized), and a toner image (toner image, developer image) is formed on the surface of the photosensitive drum 61. In this embodiment, toner charged with the same polarity as the charging polarity of the photosensitive drum 61 (negative polarity in this embodiment) adheres to the exposed area on the photosensitive drum 61, where the absolute value of the charge has decreased after being uniformly charged and then exposed. In this embodiment, the normal charging polarity of toner, which is the main charging polarity of toner during development, is negative polarity. In this embodiment, the developing roller 71 develops the electrostatic latent image while in contact with the photosensitive drum 61. However, the printer 1 may be configured such that the developing roller 71 develops the electrostatic latent image with a gap between the developing roller 71 and the photosensitive drum 61.

[0040] For example, when forming a full-color image, toner images of yellow, magenta, cyan, and black are formed on the photosensitive drums 61Y, 61M, 61C, and 61K, respectively.

[0041] In this embodiment, with the tray unit 50 in the first inner position, the developing roller 71 is movable between a contact position in contact with the photosensitive drum 61 and a separated position away from the photosensitive drum 61. Specifically, a switching device (not shown) provided on the main body 1a of the apparatus switches between the developing roller 71 being in the contact position and the developing roller 71 being in the separated position. This allows the developing roller 71 to be kept away from the photosensitive drum 61 when no image forming operation is being performed.

[0042] Furthermore, printer 1 can perform monochrome printing when the developing roller 71 and photosensitive drum 61 of cartridge PK are in contact, and the developing rollers 71 and photosensitive drums 61 of cartridges PY, PM, and PC are separated. Also, printer 1 can perform full-color printing when the photosensitive drums 61 and belt 41 of cartridges PY, PM, PC, and PK are in contact.

[0043] The toner image formed on the photosensitive drum 61 is transferred (primary transfer) to the rotating transfer surface, the belt 41, in the primary transfer section by the action of the primary transfer roller 42. During primary transfer, a primary transfer voltage with the opposite polarity to the normal charging polarity of the toner is applied to the primary transfer roller 42. The toner image transferred onto the belt 41 is transported by the rotation of the belt 41 toward the secondary transfer section, which is formed by the belt 41 and the secondary transfer roller 45. For example, when forming a full-color image, the toner images of yellow, magenta, cyan, and black formed on the photosensitive drums 61Y, 61M, 61C, and 61K are sequentially transferred so that they are superimposed on the same image forming area on the belt 41.

[0044] On the other hand, the main body 1a of the device has a transport path (first path, first transport path) 1c through which the sheet S heading toward the fuser 80 passes. The door 20 also has a double-sided transport path (second path, second transport path) 20a through which the sheet S that has passed through the fuser 80 passes. When the door 20 is closed, it covers the transport path 1c. As shown in Figure 2, when the door 20 is opened, the transport path 1c and the double-sided transport path 20a are exposed. In the sheet feeding section 30, one sheet S is separated from the sheets S loaded on the loading tray 31 at a predetermined timing by the feeding roller 32 and fed. This sheet S is transported through the transport path 1c toward the secondary transfer section and the fuser 80. In other words, the sheet S sent out from the loading tray 31 by the feeding roller 32 is transported to the registration roller pair 4. This sheet S is then transported to the secondary transfer section by the registration roller pair 4 in time with the toner image on the belt 41.

[0045] The toner image formed on the belt 41 is transferred (secondary transfer) in the secondary transfer section to the sheet S, which is being transported between the belt 41 and the secondary transfer roller 45, by the action of the secondary transfer roller 45. During secondary transfer, a secondary transfer voltage with the opposite polarity to the normal charging polarity of the toner is applied to the secondary transfer roller 45. Toner that remains on the belt 41 without being transferred to the sheet S (residual toner) is removed from the belt 41 and collected by the cleaning section 43. The cleaning section 43 has a cleaning blade 43a as a cleaning member that contacts the surface of the belt 41, and a cleaning container 43b that forms a toner collection section. The cleaning blade 43a is located inside the cleaning container 43b. The cleaning section 43 scrapes the toner from the surface of the rotating belt 41 with the cleaning blade 43a and collects it in the cleaning container 43b. The toner removed from the surface of the belt 41 by the cleaning unit 43 is transported from the cleaning unit 43 to the waste toner collection container 10 (Figure 7), which will be described later, and collected (stored) as waste toner.

[0046] The sheet S onto which the toner image has been transferred in the secondary transfer section is transported toward the fuser unit 80. The fuser unit 81 of the fuser unit 80 heats and pressurizes the sheet S carrying the unfixed toner image to fix (melt and solidify) the toner image onto the sheet S. The sheet S with the fixed toner image is then transported toward the flapper 5, which acts as a path switching section.

[0047] The flapper 5 is movable to an discharge position that guides the sheet S, which has passed through the fuser 80, toward the discharge path 1d, and to a reversal position that guides it toward the reversal path 1e. When single-sided printing is performed, in which an image is formed on one side of the sheet S, the sheet S is guided by the flapper 5 to the discharge path 1d and discharged (output) to the discharge tray 1f formed on the top of the device body 1a. On the other hand, when double-sided printing is performed, in which an image is printed on the first side (front side) and the second side (back side) of the sheet S, the sheet S, with the toner image fixed to the first side, is guided by the flapper 5 to the reversal path 1e. After being guided to the reversal path 1e, the direction of transport of this sheet S is reversed. Then, this sheet S is transported toward the secondary transfer section through the double-sided transport path 20a formed in the door 20, and the toner image is transferred to the second side. After that, this sheet S passes through the fuser 80, is guided by the flapper 5 to the discharge path 1d, and discharged to the discharge tray 1f of the device body 1a.

[0048] In this embodiment, the image forming unit 1h is configured to form a toner image on the sheet S by the image forming unit P, the transfer unit 40, the secondary transfer roller 45, etc. In this embodiment, the belt cleaning unit 43 is an example of a cleaning unit that collects toner in the image forming unit 1h. In this embodiment, the waste toner collection container 10 (Figure 7), which will be described later, which contains the toner collected from the belt 41, is an example of a waste toner collection container that contains the toner collected by the cleaning unit (waste toner collected in the main body of the device).

[0049] <Control Configuration> Figure 29 is a block diagram showing the schematic control configuration of printer 1. Printer 1 has a control unit 3 as a control means for comprehensively controlling printer 1. The control unit 3 is composed of a CPU 3a as an arithmetic processing means (arithmetic processing unit), a memory 3b as a storage means (storage unit), and an input / output circuit (not shown) as an input / output means (input / output unit). Memory 3b is composed of ROM, RAM, and EEPROM. Control programs and application programs executed by the CPU 3a are stored in the ROM. RAM functions as a work area for executing the processing of control programs. EEPROM holds data such as various settings that are desired to be retained even when the power to printer 1 is turned off. The CPU 3a controls printer 1 according to the program stored in memory 3b (ROM).

[0050] The control unit 3 is connected to, for example, a torque detection mechanism 100 (described later), an operation unit 4, a drive motor 5, a scanner 2, and a high-voltage power supply 6. The torque detection mechanism 100 can detect when the rotational load torque of the waste toner transport screw 113 provided on the waste toner collection container 10 exceeds a predetermined value (overload state), as described later. The torque detection mechanism 100 inputs a signal indicating the detection result to the control unit 3. The operation unit 4 is configured to have a display unit that displays information to the user (operator) under control by the control unit 3, and an input unit that inputs various settings and other information to the control unit 3 based on user operations. The operation unit 3 may be configured to have a touch panel or the like that has the functions of both a display unit and an input unit. In this case, the operation unit 4 displays information on the screen to the user and accepts touch input from the user. The drive motor 5 is a drive source that generates the driving force to rotate the belt 41 (drive roller 46). The printer 1 may also be provided with other drive motors as drive sources for other driven parts such as the photosensitive drum 61 and the fuser unit 80. Furthermore, the drive source for the drive roller 46, which is a driven part, and at least a portion of the drive sources for other driven parts such as the photosensitive drum 61 and the fuser 80 may be shared. The high-voltage power supply 6 applies a predetermined voltage to the charging roller 62, developing roller 71, primary transfer roller 42, secondary transfer roller 45, etc. A separate high-voltage power supply 6 may be provided for each of the above-mentioned application targets, or the high-voltage power supply 6 may be shared for multiple of the above-mentioned application targets. In addition, an external host device 400 is connected to the control unit 3. Based on the print instructions and image information input from the external host device 400, the control unit 3 can control each part of the printer 1 to perform image forming operations. Furthermore, as will be described later, the control unit 3 can perform detection and notification of the near-full and full state of the waste toner collection container 10.

[0051] <Waste toner transport route> The waste toner transport path will be explained using Figures 6, 7, and 8. Figure 6 is a perspective view showing the overall configuration of the transfer unit 40 in this embodiment. Figure 7 is a perspective view of the transfer unit 40 to explain the waste toner transport path in this embodiment, showing the transfer unit 40 with the belt 41 and the cleaning container 43b of the cleaning unit 43 removed. Figure 8 is a perspective view showing the waste toner transport path and drive coupling mechanism in this embodiment.

[0052] The cleaning unit 43 includes a cleaning container 43b and a cleaning blade 43a provided inside the cleaning container 43b. The cleaning blade 43a extends along the width direction (left-right direction), which is substantially perpendicular to the direction of movement of the surface of the belt 41. The cleaning blade 43a is positioned to contact the drive roller 46 via the belt 41. The cleaning blade 43a is also positioned to contact the surface (outer circumferential surface) of the belt 41 in a counter-direction opposite to the direction of movement of the belt 41. In other words, the cleaning blade 43a is positioned so that its free end in the short direction, which is substantially perpendicular to the longitudinal direction along the width direction of the belt 41, faces upstream of the direction of movement of the surface of the belt 41, and is in contact with the surface of the belt 41. The cleaning blade 43a scrapes toner from the surface of the rotating belt 41 and collects it as waste toner inside the cleaning container 43b. Here, the cleaning blade 43a is in contact with the belt 41 at a predetermined angle, and the toner can be removed from the surface of the belt 41 as the belt 41 moves in one direction. In this embodiment, no driving force is input from the drive source to the drive roller 46 so that the belt 41 and the drive roller 46 rotate in opposite directions.

[0053] The transfer unit 40 has a transfer frame 48 as a frame that supports the drive roller 46, tension roller 47, and each primary transfer roller 42. In this embodiment, a space (region) capable of accommodating waste toner is provided inside the transfer frame 48. In other words, in this embodiment, the transfer frame 48 also serves as the waste toner collection container 10. However, the waste toner collection container 10 may be configured separately from the transfer frame 48 and attached to the transfer frame 48. That is, in this embodiment, the waste toner collection container 10 is provided within the region formed by the inner circumferential surface of the belt 41. In this embodiment, within the device body 1a, the waste toner collection container 10 is positioned so that its bottom surface intersects with the direction of gravity. Also, in this embodiment, the waste toner collection container 10 is configured to be substantially rectangular in shape when viewed in a direction substantially perpendicular to the primary transfer surface 41a of the belt 41. On the upper surface of the waste toner collection container 10, grooves 10bY, 10bM, 10bC, and 10bK are formed along the rotation axis direction (left-right direction) of each primary transfer roller 42, in the portion facing the primary transfer rollers 42Y, 42M, 42C, and 42K. This prevents the waste toner collection container 10 from restricting the rotation of each primary transfer roller 42. The drive roller 46, tension roller 47, and each primary transfer roller 42 are rotatably supported via support parts provided on the transfer frame 48.

[0054] The cleaning unit 43 has a cleaning screw 111 and an intermediate screw 112 inside it, which serve as waste toner transport members for transporting the waste toner removed from the belt 41 by the cleaning blade 43a. The cleaning screw 111 has a rotating shaft arranged along the width direction (left-right direction) of the belt 41 and a helical transport section formed along the axial direction of this rotating shaft. The cleaning screw 111 is driven and connected to a drive roller 46 by a drive coupling (not shown), and rotates by receiving a driving force input from the drive motor 5 to the drive roller 46 via this drive coupling. As the cleaning screw 111 rotates, it transports the waste toner in the direction of arrow Ta in Figure 8 (from right to left). The intermediate screw 112 has a rotating shaft arranged along a direction intersecting the rotation axis direction of the cleaning screw 111 (a direction intersecting the horizontal direction) and a helical transport section formed along the axial direction of this rotating shaft. One end (upper end) of the intermediate screw 112 in the direction of its rotational axis is positioned close to one end (left end) of the cleaning screw 111 in the direction of its rotational axis. The intermediate screw 112 is driven and connected to the cleaning screw 111 at this end and rotates by receiving driving force from the cleaning screw 111. As the intermediate screw 112 rotates, it transports waste toner in the direction of arrow Tb in Figure 8 (from top to bottom). The other end of the intermediate screw 112 in the direction of its rotational axis is positioned close to one end (left and front end) of the waste toner transport screw 113, which will be described later, in the direction of its rotational axis. The intermediate screw 112 is located inside the transport path 43b1 (Figure 6) provided at the left end of the cleaning container 43b. This transport path 43b1 is connected to the inlet 10a (Figure 8) of the waste toner collection container 10, and the inside of the waste toner collection container 10 and the inside of the transport path 43b1 are in communication through this inlet 10a. The waste toner conveyed by the cleaning screw 111 in the direction of arrow Ta in Figure 8 is conveyed by the intermediate screw 112 in the direction of arrow Tb in Figure 8 and flows into the inside of the waste toner collection container 10 from the inlet 10a.

[0055] Furthermore, a waste toner transport screw 113 is provided inside the waste toner collection container 10 as a waste toner transport member. The waste toner transport screw 113 has a rotating shaft and a helical transport section formed along the axial direction of this rotating shaft. One end of the waste toner transport screw 113 in the direction of the rotation axis (the left and front end) is positioned close to the inlet 10a of the waste toner collection container 10. The other end of the waste toner transport screw 113 in the direction of the rotation axis is rotatably supported by a bearing section 10c provided inside the waste toner collection container 10. The waste toner transport screw 113 is driven and connected to a drive roller 46 by a drive coupling mechanism 120, which will be described later, and rotates by receiving driving force input from the drive motor 5 to the drive roller 46 via this drive coupling mechanism 120. As the waste toner transport screw 113 rotates, it transports the waste toner that has flowed into the waste toner collection container 10 from the inlet 10a in the direction of arrow Tc in Figure 8.

[0056] The rotation axis direction of the waste toner transport screw 113 is, when viewed in a direction approximately perpendicular to the primary transfer surface 41a of the belt 12, not perpendicular to the direction of movement of the primary transfer surface 41a (front-to-back direction) or the width direction of the belt 41 (left-to-right direction), but intersects with these directions. The waste toner that flows into the waste toner collection container 10 from the inlet 10a is transported by the waste toner transport screw 113 toward the approximate center of the waste toner collection container 10 when viewed in a direction approximately perpendicular to the primary transfer surface 41a of the belt 41, as shown by the arrow Tc in Figure 8. The end of the spiral transport section of the waste toner transport screw 113 opposite the inlet 10a in the rotation axis direction is located approximately in the center of the waste toner collection container 10. Therefore, the waste toner transported by the waste toner transport screw 113 fills the waste toner collection container 10 while diffusing concentrically from the approximate center of the waste toner collection container 10.

[0057] In this way, the toner removed from the belt 41 by the cleaning blade 43a is transported to the waste toner collection container 10 by the cleaning screw 111 and intermediate screw 112 located inside the cleaning container 43b. The waste toner collection container 10 is also equipped with a waste toner transport screw 113 that transports the waste toner toward the approximate center of the waste toner collection container 10, and the waste toner is accumulated inside the waste toner collection container 10. The waste toner transport screw 113, as a driven member, rotates when driving force is input from the drive motor 5, which is the driving source, via the drive coupling mechanism 120 described later. When the number of sheets of paper fed by the printer 1 increases and the amount of waste toner increases, the waste toner is transported radially from the center outwards in the waste toner collection container 10.

[0058] In this embodiment, when the amount of waste toner accumulated in the waste toner collection container 10 exceeds a predetermined amount (typically exceeding the predetermined amount), this condition is detected and a warning is issued to the user. In this embodiment, this condition is referred to as the "near-full state," and the warning issued to the user when this condition occurs is referred to as the "near-full notification." In this embodiment, even after the near-full notification is issued, the printer 1 can continue printing until the amount of waste toner collected in the waste toner collection container 10 reaches a predetermined amount (second predetermined amount). When the amount of waste toner collected in the waste toner collection container 10 reaches a predetermined amount (second predetermined amount) that can be stored in the waste toner collection container 10, this condition is detected and a warning is issued to the user. In this embodiment, this condition is referred to as the "full state," and the warning issued to the user when this condition occurs is referred to as the "full notification." In this embodiment, when the full notification is issued, the printer 1 stops operating (printing is prohibited).

[0059] As the amount of waste toner in the waste toner collection container 10 increases, the density of the waste toner increases. As a result, the resistance generated when the waste toner is transported by the waste toner transport screw 113 increases, and the rotational load torque of the waste toner transport screw 113 increases.

[0060] In this embodiment, when the rotational load torque of the waste toner transport screw 113 exceeds a predetermined value (overload condition) (typically exceeding the predetermined value), the torque detection mechanism 100 (Figure 13, etc.), described later, detects that the waste toner collection container 10 is nearly full. Based on the detection result by the torque detection mechanism 100, the control unit 3 notifies the user of a warning, such as by displaying a message on the screen of the operation unit 4 provided on the printer 1. This warning can be given by displaying a message prompting the user to prepare to replace the waste toner collection container 10. Alternatively, or in addition to the operation unit 4, a similar warning can be displayed on the display unit of an external host device 400 connected to the printer 1.

[0061] Furthermore, in this embodiment, even after detecting that the waste toner collection container 10 is nearly full, the printer 1 can continue printing until the amount of waste toner collected in the waste toner collection container 10 reaches a predetermined amount and fills it. In this embodiment, the control unit 3 calculates the amount of toner consumed by the printing operation based on image information from the nearly full state to the full state. In other words, the control unit 3 can calculate the amount of toner consumed by the printing operation by counting the number of pixels in the printed image. When the amount of toner consumed by the printing operation since the near full state was detected reaches a predetermined amount, the control unit 3 notifies the user of the warning by displaying it on the screen of the operation unit 4 provided on the printer 1. This warning can be given by displaying a message prompting the user to replace the waste toner collection container 10. However, the means for detecting the amount of waste toner collected in the waste toner collection container 10 after the near full state is detected is not limited to the method described above. For example, methods such as counting the number of sheets of paper fed, providing a detection means to detect when the printer is full, or counting the rotation time or number of rotations of the drive roller 46 (transfer unit 40) may be used. In addition, similar warnings can be displayed on the display unit of an external host device 400 connected to the printer 1, instead of or in addition to the operation unit 4.

[0062] <Drive coupling mechanism> Using Figures 8, 9, and 10, the drive coupling mechanism 120, which serves as a drive coupling means (drive coupling section) for transmitting driving force from the drive motor 5 to the waste toner transport screw 113 in this embodiment, will be explained. Figure 9 is a perspective view of the drive coupling mechanism 120 in this embodiment. Figure 10 is an exploded perspective view of the drive coupling mechanism 120 in this embodiment.

[0063] As shown in Figure 8, the waste toner transport screw 113 and the drive roller 46 are driven and connected by a drive coupling mechanism 120 provided on the transfer unit 40. The drive coupling mechanism 120 is provided on the left end of the drive roller 46 in the direction of its rotation axis. As shown in Figures 9 and 10, the drive coupling mechanism 120 is composed of a movable gear 121, a fixed gear 122, a detection lever 123, a biasing spring 124, a cover member 125, a drive gear 126, and an idler gear 127.

[0064] The movable gear 121 is a drive transmission member that receives driving force from the drive roller 46 side and is provided to be movable along its rotation axis. As will be described later, the movable gear 121 is movable between a first position and a second position, in which its relative position to the fixed gear 122 in the rotation axis direction is different, in conjunction with the change in the relative position of the fixed gear 122 with respect to the movable gear 121 in the rotation direction according to the magnitude of the rotation load torque of the waste toner transport screw 113. The fixed gear 122 is a drive transmission member that engages with the movable gear 121 to receive driving force from the movable gear 121 and also engages with the waste toner transport screw gear 113a provided on the waste toner transport screw 113 to transmit driving force to the waste toner transport screw 113. The waste toner transport screw gear 113a is provided at one end (the left and front end) in the rotation axis direction of the waste toner transport screw 113, on the rotation axis of the waste toner transport screw 113, so as to rotate integrally with the waste toner transport screw 113. The detection lever 123 is a detection member for detecting the movement of the movable gear 121 by moving integrally with the movable gear 121 along the rotation axis direction of the movable gear 121, as will be described later. The detection lever 123 has a lever portion 123a and a lever support portion 123b, the lever support portion 123b is fitted into a movable gear recess 121f provided in the movable gear 121. As a result, the detection lever 123 is held on the movable gear 121 so as to be rotatable relative to the movable gear 121, maintaining the position of the lever portion 123a in the rotation direction of the movable gear 121. The biasing spring 124 is a biasing member (in this embodiment, an elastic member, which is a compression coil spring) that acts as a biasing means to bias the movable gear 121 toward the fixed gear 122 along the rotation axis direction of the movable gear 121 via the detection lever 123. The cover member 125 is a holding member that has the function of holding the drive coupling mechanism 120 to the transfer frame 48, and is fixed to the transfer frame 48. The drive gear 126 is provided at one end (the left end) in the direction of the rotation axis of the drive roller 46, on the rotation axis 46a of the drive roller 46, so as to rotate integrally with the drive roller 46.The idler gear 127 engages with the drive gear 126 to receive driving force from the drive gear 126, and also engages with the movable gear 121 to transmit driving force to the movable gear 121. In other words, the drive gear 126 transmits drive to the movable gear 121 via the idler gear 127. Driving force is input from the drive motor 5 to the drive roller 46 via a drive coupling part (not shown) provided, for example, at the other end (right end) in the direction of the rotation axis of the drive roller 46.

[0065] Here, the side of the fixed gear 122 opposite to the movable gear 121 in the direction of its rotation axis abuts against the wall of the transfer frame 48. The biasing spring 124 is positioned between the fixed cover member 125 and the detection lever 123, which is movable along the rotation axis of the movable gear 121 together with the movable gear 121. The movable gear 121 and the detection lever 123 are biased by the biasing spring 124 toward the fixed gear 122 along the rotation axis of the movable gear 121. In other words, the movable gear 121 and the detection lever 123 are positioned between the fixed gear 122 and the cover member 125 with degrees of freedom to move along the rotation axis of the movable gear 121.

[0066] Thus, the drive coupling mechanism 120 includes a movable gear 121 as a first rotating body (first member, rotating member) positioned on the input side of the rotational driving force, a fixed gear 122 as a second rotating body (second member, rotated member) provided coaxially and relatively rotatable with respect to the first rotating body and positioned on the output side of the rotational driving force, a biasing spring 124 as a biasing member (elastic member) that applies a biasing force (elastic force) in a direction that causes the movable gear 121 and the fixed gear 122 to press against each other along the rotation axis direction, and a detection lever 123 that can move together with the movable gear 121.

[0067] Figure 11 shows a perspective view and a front view in more detail of the movable gear 121 and the fixed gear 122 in this embodiment. Figure 11(a) is a perspective view showing the side of the movable gear 121 facing the fixed gear 122 in the direction of the rotation axis, and Figure 11(b) is a front view showing that side of the movable gear 121. Figure 11(c) is a perspective view showing the side of the fixed gear 122 facing the movable gear 121 in the direction of the rotation axis, and Figure 11(d) is a front view showing that side of the fixed gear 122. The movable gear 121 and the fixed gear 122 have cam shapes (cam-shaped portions) that engage with each other.

[0068] The movable gear 121 rotates in the direction of arrow R1 in the figure. The movable gear 121 has a cam shape along the rotational direction (circumferential direction) on the surface facing the fixed gear 122 in the direction of the rotation axis. The movable gear 121 has a first inclined surface 121a, a flat surface 121b, a first vertical wall 121c, a second vertical wall 121d, and a second inclined surface 121e. Of the first inclined surface 121a and the second inclined surface 121e, the first inclined surface 121a is located on the downstream side in the rotational direction of the movable gear 121, and the second inclined surface 121e is located on the upstream side in the rotational direction of the movable gear 121. The first inclined surface 121a is inclined with respect to the rotational axis of the movable gear 121 such that it approaches the fixed gear 122 as it moves upstream in the rotational direction of the movable gear 121. Furthermore, the second inclined portion 121e is inclined with respect to the rotation axis direction of the movable gear 121 such that it moves away from the fixed gear 122 as it moves upstream in the rotation direction of the movable gear 121. A convex portion 121h having a first vertical wall portion 121c, a second vertical wall portion 121d, and a flat portion 121b is provided on the fixed gear 122 side surface of the base portion 121g on which the first inclined portion 121a and the second inclined portion 121e are formed. The first vertical wall portion 121c and the second vertical wall portion 121d each extend along the rotation axis direction of the movable gear 121 (approximately parallel in this embodiment). Of the first vertical wall portion 121c and the second vertical wall portion 121d, the first vertical wall portion 121c is provided on the downstream side in the rotation direction of the movable gear 121, and the second vertical wall portion 121d is provided on the upstream side in the rotation direction of the movable gear 121. The planar portion 121b extends between the first vertical wall portion 121c and the second vertical wall portion 121d along a plane that intersects (approximately perpendicular in this embodiment) with the rotation axis direction of the movable gear 121. The movable gear 121 also has a gear portion 121i on its outer circumference.

[0069] The fixed gear 122 rotates in the direction of arrow R2 in the figure. The fixed gear 122 has a cam shape along the rotational direction (circumferential direction) on the side of the movable gear 121 in the direction of the rotation axis. The fixed gear 122 has a first fixed inclined surface portion 122a, a first fixed flat surface portion 122b, a first fixed vertical wall portion 122c, a second fixed vertical wall portion 122d, a second fixed inclined surface portion 122e, and a second fixed flat surface portion 122f. Of the first fixed inclined surface portion 122a and the second fixed inclined surface portion 122e, the first fixed inclined surface portion 122a is provided on the upstream side in the rotational direction of the fixed gear 122, and the second fixed inclined surface portion 122e is provided on the downstream side in the rotational direction of the fixed gear 122. The first fixed inclined surface portion 122a is inclined with respect to the rotational axis direction of the fixed gear 122 such that it moves away from the movable gear 122 as it moves upstream in the rotational direction of the fixed gear 122. Furthermore, the second fixed inclined surface 122e is inclined with respect to the rotation axis direction of the fixed gear 122 such that it approaches the movable gear 121 as it moves upstream in the rotation direction of the fixed gear 122. A fixed convex shape portion 122h having a first fixed vertical wall portion 122c and a second fixed vertical wall portion 122d is provided on the movable gear 121 side surface of the fixed base portion 122g on which the first fixed inclined surface portion 122a and the second fixed inclined surface portion 122e are formed. The first fixed vertical wall portion 122c and the second fixed vertical wall portion 122d each extend along the rotation axis direction of the fixed gear 122 (approximately parallel in this embodiment). Of the first fixed vertical wall portion 122c and the second fixed vertical wall portion 122d, the first fixed vertical wall portion 122c is provided on the upstream side in the rotation direction of the fixed gear 122, and the second fixed vertical wall portion 122d is provided on the downstream side in the rotation direction of the fixed gear 122. The first fixed plane portion 122b and the second fixed plane portion 122f each extend along a plane that intersects (approximately perpendicular in this embodiment) with the rotation axis direction of the fixed gear 122. Of the first fixed plane portion 122b and the second fixed plane portion 122f, the first fixed plane portion 122b is provided on the upstream side in the rotation direction of the fixed gear 122, and the second fixed plane portion 122f is provided on the downstream side in the rotation direction of the fixed gear 122. The first fixed plane portion 122b and the second fixed plane portion 122f are provided on the upstream and downstream sides of the fixed convex shape portion 122h in the rotation direction of the fixed gear 122. The fixed gear 122 also has a gear portion 122i on its outer circumference.

[0070] In this embodiment, the movable gear 121 is also provided with the same cam shape as described above on the opposite side of the rotation axis of the movable gear 121 (at a position shifted 180 degrees in the rotational direction). Similarly, in this embodiment, the fixed gear 122 is also provided with the same cam shape as described above on the opposite side of the rotation axis of the fixed gear 122 (at a position shifted 180 degrees in the rotational direction).

[0071] Figure 12 is a cross-sectional view of the cam shapes of the movable gear 121 and fixed gear 122, cut along the dashed lines in Figures 11(b) and 11(d), schematically illustrating the operation of the drive coupling mechanism 120 during the rotational operation of the drive roller 46. Figures 12(a), 12(b), and 12(c) show the state of the movable gear 121 and fixed gear 122 when the amount of waste toner in the waste toner collection container 10 (rotational load torque of the waste toner transport screw 113) is different, as will be described later.

[0072] The movable gear 121 is biased by a biasing spring 124 with a spring force (spring pressure) Fs toward the fixed gear 122 along the rotation axis direction of the movable gear 121. When the movable gear 121 receives a drive input and rotates in the direction of arrow R1, the first inclined surface (first contact part) 121a and the first fixed inclined surface (third contact part) 122a come into contact, and the movable gear 121 receives a reaction force Ft corresponding to the magnitude of the rotational load torque of the fixed gear 122. Figure 12(a) shows a state in which the amount of waste toner in the waste toner collection container 10 is less than a predetermined amount (here, this state is also called the "normal state"). In this state, since the amount of waste toner in the waste toner collection container 10 is less than a predetermined amount, the rotational load torque of the fixed gear 122 that receives the transport resistance of the waste toner is smaller than a predetermined value. In other words, since the reaction force Ft acting on the movable gear 121 is smaller than the spring force Fs, the first inclined surface 121a and the first fixed inclined surface 122a come into contact (engage), and the driving force is transmitted from the movable gear 121 to the fixed gear 122. The fixed gear 122 then rotates in the direction of arrow R2.

[0073] When the amount of waste toner in the waste toner collection container 10 reaches a predetermined amount (near full in this embodiment), the rotational load torque of the fixed gear 122 increases, and the reaction force Ft acting on the movable gear 121 balances the spring force Fs. As the amount of waste toner in the waste toner collection container 10 increases, the first inclined surface 121a and the first fixed inclined surface 122a slide relative to each other, as shown in Figure 12(b). As a result, the movable gear 121 moves in the opposite direction to the biasing direction of the biasing spring 124 (away from the fixed gear 122 along the rotation axis direction of the movable gear 121).

[0074] Subsequently, as shown in Figure 12(c), the first inclined surface 121a and the first fixed inclined surface 122a become separated. Then, as shown in Figure 12(c), the flat surface 121b and the first fixed flat surface 122b come into contact (engage), and the first vertical wall (second contact part) 121c and the first fixed vertical wall (fourth contact part) 122c come into contact (engage). That is, when the amount of waste toner in the waste toner collection container 10 exceeds a predetermined amount, the first vertical wall 121c and the first fixed vertical wall 122c come into contact, and driving force is transmitted from the movable gear 121 to the fixed gear 122.

[0075] As described above, in this embodiment, the rotational drive direction of the drive roller 46 that drives the belt 41 is unidirectional, and the movable gear 121 does not rotate in the reverse direction. Therefore, when the movable gear 121 and the fixed gear 122 are in the state shown in Figure 12(c), the movable gear 121 is held in a state where it cannot move in the direction of the rotation axis of the movable gear 121, with the planar portion 121b and the first fixed planar portion 122b in contact. The planar portion 121b and the first fixed planar portion 122b function as restricting parts that restrict the phase, which is the relative position of the fixed gear 122 with respect to the rotation direction of the movable gear 121, from the second phase (a state in which the rotational load torque is above a predetermined value) to the first phase (a state in which the rotational load torque is below a predetermined value). As described above, if the state of the waste toner in the waste toner collection container 110 changes due to factors such as vibration caused by user operation, and the transport resistance of the waste toner transport screw 113 decreases, the rotational load torque of the fixed gear 122 may decrease. In this embodiment, once the state shown in Figure 12(c) is reached, even if the rotational load torque of the fixed gear 122 decreases thereafter, the movable gear 121 and the fixed gear 122 maintain the state shown in Figure 12(c). That is, the flat portion 121b and the first fixed flat portion 122b remain in contact, while the first inclined portion 121a and the first fixed inclined portion 122a remain separated. In other words, even if the state of the waste toner in the waste toner collection container 10 changes and the transport resistance of the waste toner transport screw 113 decreases, the state shown in Figure 12(a), where the first inclined portion 121a and the first fixed inclined portion 122a are in contact and the driving force is transmitted, will not be returned.

[0076] Thus, in this embodiment, even if the amount of waste toner in the waste toner collection container 10 increases and the transport resistance of the waste toner transport screw 113 increases, the drive transmission between the movable gear 121 and the fixed gear 122 continues by changing the part to which the driving force is transmitted. Therefore, even after the near-full state is detected, it is possible to continue transporting waste toner to the waste toner collection container 10. As a result, it is possible to continue collecting waste toner in the same space (area), i.e., the waste toner collection container 10 in this embodiment, before and after the near-full state is detected. In other words, there is no need to secure a separate space to collect the waste toner transported after the near-full state is detected. Furthermore, there is no need to accumulate the amount of waste toner after the near-full state is detected in the waste toner transport path. Therefore, it is possible to reduce the size and cost of the printer 1.

[0077] In this embodiment, both the first inclined surface portion 121a and the first fixed inclined surface portion 122a, which are in contact with each other, are inclined surfaces with respect to the rotation axis direction of the movable gear 121. However, at least one of them may be such an inclined surface. For example, one may be an inclined surface with respect to the rotation axis direction of the movable gear 121, and the other may be a rib shape or boss shape that contacts that surface. Also, in this embodiment, both the first vertical wall portion 121c and the first fixed vertical wall portion 122c, which are in contact with each other, are surfaces that are substantially parallel to the rotation axis direction of the movable gear 121. However, at least one of them may be such a surface. For example, one may be an surface that is substantially parallel to the rotation axis direction of the movable gear 121, and the other may be a rib shape or boss shape that contacts that surface. Furthermore, in this embodiment, the planar portion 121b, which serves as a restricting portion on the movable gear 121, contacts the first fixed planar portion 122b of the fixed gear to restrict the phase change of the fixed gear 122. However, as can be seen from Figure 12(c), the regulating portion (the flat portion at the top of the fixed convex shape portion 122h) provided on the fixed gear 122 may contact the movable gear 121 to restrict the phase change of the fixed gear 122. In other words, the regulating portion only needs to be provided on at least one of the movable gear 121 or the fixed gear 121.

[0078] Figure 13 is a perspective view showing the torque detection mechanism 100, which serves as a torque detection means (torque detection unit) for detecting when the rotational load torque of the waste toner transport screw 113 exceeds a predetermined value (overload condition) in this embodiment. Figure 14 is a cross-sectional view showing the torque detection mechanism 100 in this embodiment.

[0079] As shown in Figures 13 and 14, the detection flag 130 and the detection sensor 131 are attached to and held by a sensor holder 132 provided on the main body side plate 1g, which is a side plate of the device body 1a. The detection flag 130 has a flag rotation axis 130a, a movable receiving portion 130b that can contact the lever portion 123a of the detection lever 123 provided on the drive coupling mechanism 120, and a light-shielding portion 130c that can enter and retract from the detection area 131c of the detection sensor 131. The detection flag 130 is attached to the sensor holder 132 so as to be rotatable around the flag rotation axis 130a, by having the flag rotation axis 130a rotatably supported by the sensor holder 132. Furthermore, the orientation of the detection flag 130 is maintained by a spring and a stopper (not shown) such that the movable receiving portion 130b moves toward the detection lever 123 and the light-shielding portion 130c is retracted from the detection area 131c of the detection sensor 131 (at least the optical axis of the detection light). In other words, the orientation of the detection flag 130 is maintained in the state shown in Figure 14(a). In this embodiment, the detection sensor 131 constituting the detection means is composed of a light-shielding and light-transmitting detection sensor (photosensor). The detection sensor 131 is configured in a U-shape in cross-section and has a light-emitting portion 131a, a light-receiving portion 131b, and a detection area 131c formed between the light-emitting portion 131a and the light-receiving portion 131b. The detection area 131c constitutes the optical path of the detection light from the light-emitting portion 131a toward the light-receiving portion 131b and allows the light-shielding portion 130c of the detection flag 130 to be located there. In this embodiment, the torque detection mechanism 100 is configured with a drive coupling mechanism 120 having a movable gear 121, a fixed gear 122, a detection lever 123, a biasing spring 124, and a cover member 125, a detection flag 130, and a detection sensor 131. In this embodiment, the torque detection mechanism 100 can detect whether the phase, which is the relative position of the fixed gear 122 with respect to the rotation direction of the movable gear 121, is in a first phase (a state in which the rotational load torque is less than a predetermined value) or a second phase (a state in which the rotational load torque is greater than or equal to a predetermined value) by having the detection sensor 131 detect the state of light shielding and transmission of detection light.

[0080] Figures 13(a) and 14(a) show the state where the amount of waste toner in the waste toner collection container 10 is less than a predetermined amount. In other words, Figures 13(a) and 14(a) show the normal state in which the movable gear 121 and the fixed gear 122 are engaged at the first inclined surface portion 121a and the first fixed inclined portion 122a. Figures 13(b) and 14(b) show the state in which the amount of waste toner in the waste toner collection container 10 has reached a predetermined amount, i.e., the near-full state. In other words, Figures 13(b) and 14(b) show the state in which the movable gear 121 and the fixed gear 122 are in contact at the flat portion 121b and the first fixed flat portion 122b, and also at the first vertical wall portion 121c and the first fixed vertical wall portion 122c.

[0081] As shown in Figures 13(a) and 14(a), when the amount of waste toner in the waste toner collection container 10 is less than a predetermined amount, the detection lever 123 is separated from the movable receiving portion 130b of the detection flag 130. The light-shielding portion 130c of the detection flag 130 is retracted from the detection area 131c of the detection sensor 131 (at least the optical axis of the detection light). As shown in Figures 13(b) and 14(b), when the amount of waste toner in the waste toner collection container 10 reaches a predetermined amount, the movable gear 121 and the detection lever 123 move along the rotation axis direction of the movable gear 121 due to the aforementioned operation. As a result of this movement, the lever portion 123a of the detection lever 123 comes into contact with the movable receiving portion 130b of the detection flag 130, causing the detection flag 130 to rotate around the flag rotation axis 130a. As a result, the light-shielding portion 130c of the detection flag 130 enters the detection area 131c of the detection sensor 131, blocking the optical axis of the detection light of the detection sensor 131. In this way, by detecting the light-shielding state of the detection sensor 131, the torque detection mechanism 100 can detect that the waste toner collection container 10 is nearly full. In other words, the detection sensor 131 can transition between a first state, a transparent state, and a second state, a light-shielding state. The detection flag member 130 causes the detection sensor 131 to transition between a light-shielding state and a light-transmitting state. The detection flag 130 causes the detection sensor 131 to be in a light-shielding state by blocking the optical path of the detection sensor 131, and causes the detection sensor 131 to be in a light-transmitting state by opening the optical path. The detection sensor 131 outputs different detection signals depending on whether it is in a light-shielding state or a light-transmitting state. For example, the output signal of the detection sensor 131 is set to OFF for the transparent state and ON for the light-shielding state. This signal is input to the control unit 3. This allows the control unit 3 to determine (detect) that the waste toner collection container 10 is nearly full. The detection sensor 131 only needs to be able to detect at least one of the blocking or transmission of the detection light.

[0082] As mentioned above, the state of waste toner in the waste toner collection container 10 is not always stable, and impacts from user operation or other factors can reduce the rotational load torque of the waste toner transport screw 113. In this embodiment, when the rotational load torque of the waste toner transport screw 113 exceeds a predetermined value (overload state), i.e., when it is nearly full, the torque detection mechanism 100 (drive coupling mechanism 120) enters the following state. That is, as shown in Figure 12(c), the movable gear 121 and the fixed gear 122 come into contact at the flat portion 121b and the first fixed flat portion 122b. Therefore, even if the rotational load torque of the waste toner transport screw 113 decreases as described above after the torque detection mechanism 100 detects the nearly full state, it maintains the state shown in Figure 12(c) and does not return to the normal state shown in Figure 12(a). In other words, even if the state of the waste toner in the waste toner collection container 10 changes due to factors such as vibration after detecting a near-full state, and the rotational load torque of the waste toner transport screw 113 decreases, the torque detection mechanism 100 can maintain the state in which it detected a near-full state.

[0083] Thus, the image forming apparatus (printer) 1 of this embodiment includes a driven member (waste toner transport screw) 113, a drive source (drive motor) 5 that generates a driving force to rotate the driven member 113, a first rotating body (movable gear) 121 that rotates when the driving force from the drive source 5 is input, a second rotating body (fixed gear) 122 that is provided coaxially with the first rotating body 121 and rotates when the driving force from the drive source 5 is transmitted by the first rotating body 121, and transmits the driving force toward the driven member 113, wherein the second rotating body 122 is rotatable relative to the first rotating body 121 from a first phase to a second phase, which are different phases in the rotation direction of the first rotating body 121, and detection means (detection flag 130, detection sensor 131) that can detect when the second rotating body 122 is in the second phase. Furthermore, in this embodiment, the first rotating body 121 and the second rotating body 122 are configured such that when the rotational load torque of the driven member 113 is the first torque, the second rotating body 122 rotates in the first phase, and when the rotational load torque of the driven member 113 is the second torque, which is greater than the first torque, the second rotating body 122 rotates in the second phase, so that the phase changes as the rotational load torque of the driven member 113 changes from the first torque to the second torque. In this embodiment, the image forming apparatus 1 has restricting means (planar portion 121b, first fixed planar portion 122b) that restrict the phase from returning from the second phase to the first phase, even if the rotational load torque of the driven member 113 decreases from the second torque to the first torque when the phase changes from the first phase to the second phase.

[0084] In this embodiment, the first rotating body 121 has a first contact portion (first inclined surface portion) 121a that contacts the second rotating body 122 when the second rotating body 122 is in the first phase and transmits driving force to the second rotating body 122, and a second contact portion (first vertical wall portion) 121c that contacts the second rotating body 122 when the second rotating body 122 is in the second phase and transmits driving force to the second rotating body 122, and the second rotating body 122 has a third contact portion (first fixed inclined surface portion) that contacts the first contact portion 121a when the second rotating body 122 is in the first phase and receives driving force from the first rotating body 121. The first rotating body 121 has a 122a and a fourth contact portion (first fixed vertical wall portion) 122c that contacts the second contact portion (first vertical wall portion) 121c when the second rotating body 122 is in the second phase and receives driving force from the first rotating body 121. When the rotational load torque of the driven member 113 changes from the first torque to the second torque, the relative position of the first contact portion 121a with respect to the third contact portion 122a in the direction of the rotation axis of the first rotating body 121 changes, and the relative position of the first rotating body 121 with respect to the second rotating body 122 in the direction of the rotation axis of the first rotating body 121 changes. Here, at least one of the first contact portion 121a or the third contact portion 122a can be configured to have a surface inclined with respect to the rotation axis of the first rotating body 121. Furthermore, at least one of the second contact portion 121c or the fourth contact portion 122c may be configured to have a surface substantially parallel to the rotation axis direction of the first rotating body 121. In this embodiment, the regulating means is configured to have at least one of the following: a regulating portion (planar portion) 121b provided on the first rotating body 121 that contacts the second rotating body 122 when the second rotating body 122 is in the second phase and regulates the change in the relative position of the first rotating body 121 with respect to the second rotating body 122 in the rotation axis direction of the first rotating body 121; or a regulating portion provided on the second rotating body 122 that contacts the first rotating body 121 when the second rotating body 122 is in the second phase and regulates the change in the relative position of the first rotating body 121 with respect to the second rotating body 122 in the rotation axis direction of the first rotating body 121.

[0085] Furthermore, in this embodiment, the image forming apparatus 1 has a biasing member (biasing spring) 124 that applies a biasing force in a direction that causes the first rotating body 121 and the second rotating body 122 to press against each other along the rotation axis direction of the first rotating body 121. Furthermore, in this embodiment, the detection means is configured to include a flag (detection flag 130) whose position changes in conjunction with the change in phase, such that it is located in a first position (retracted position) when the second rotating body 122 is in a first phase and in a second position (protruding position) when the second rotating body 122 is in a second phase, and a sensor (detection sensor) 131 that can detect when the flag 130 is in the second position. In this embodiment, the sensor 131 is configured to include a photosensor that detects at least one of the shielding or transmission of detection light due to the change in the position of the flag 130. In this embodiment, the image forming apparatus 1 includes an image forming unit (cartridge) P that forms a toner image, an endless belt 41 onto which the toner image formed in the image forming unit P is transferred, a cleaning unit 43 that removes toner from the belt 41, a waste toner collection container 10 that contains the toner removed from the belt 41 by the cleaning unit 43, and a waste toner transport member 113 that transports toner in the waste toner collection container 10, with the driven member being the waste toner transport member 113. In this embodiment, the second torque is the rotational load torque of the waste toner transport member 113 when the amount of toner contained in the waste toner collection container 10 reaches a predetermined amount. In this embodiment, a unit (transfer unit) 40 including the belt 41, the cleaning unit 43, the waste toner collection container 10, the waste toner transport member 113, the first rotating body 121, and the second rotating body 122 is detachably attached to the main body 1a of the image forming apparatus 1.

[0086] As explained above, according to this embodiment, even if the rotational load torque of the waste toner transport screw 113 falls below a predetermined value after it has been detected that the rotational load torque of the waste toner transport screw 113 has exceeded a predetermined value, the detection state can be maintained.

[0087] [Example 2] Next, other embodiments of the present invention will be described. In this embodiment, another example of a torque detection mechanism that detects when the rotational load torque of the waste toner transport screw exceeds a predetermined value (overload condition) 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, 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.

[0088] Figure 15 is a perspective view of the drive coupling mechanism 220 in this embodiment. Figure 16 is an exploded perspective view of the drive coupling mechanism 220 in this embodiment.

[0089] As shown in Figures 15 and 16, the drive coupling mechanism 220 includes a drive spool 201 as a first rotating body (first member, rotating member) positioned on the input side of the rotational driving force, a driven spool 202 as a second rotating body (second member, rotated member) provided coaxially and rotatably with respect to the first rotating body and positioned on the output side of the rotational driving force, a torsion spring 203 as a biasing member (elastic member) that applies a biasing force (elastic force) along the rotational direction between the drive spool 201 and the driven spool 202, and a detection flag 204. The drive spool 201 transmits the driving force input to the drive roller 46 to the driven spool 202. The driven spool 202 transmits the driving force received from the drive spool 201 to the waste toner transport screw 113, causing the waste toner transport screw 113 to rotate. The drive spool 201 rotates in the direction of arrow R3 in the figure. The driven sprocket 202 rotates in the direction of arrow R4 in the figure. Similar to Embodiment 1, in this embodiment, the rotational drive direction of the drive roller 46 that drives the belt 41 is unidirectional, and the driven sprocket 201 does not rotate in the reverse direction. The driven sprocket 201 and the driven sprocket 202 are rotatably mounted on a rotating shaft (not shown) via insertion holes 201h and 202h, respectively. The driven sprocket 201 and the driven sprocket 202 may be configured as simple rotating bodies, or they may be configured as gears with teeth (gear parts) such as spur teeth formed on their outer circumference to transmit rotational driving force.

[0090] Figure 17 is a perspective view of the torque detection mechanism 200 in this embodiment. Figure 17(a) shows the case when the rotational load torque is less than a predetermined value, and Figure 17(b) shows the case when the rotational load torque is greater than or equal to the predetermined value. The left figures of Figures 18(a) and (b) are cross-sectional views showing a cross section (section AA in the right figure) that is approximately perpendicular to the rotation axis direction of the drive top 201. Figure 18(a) shows the case when the rotational load torque is less than a predetermined value, and Figure 18(b) shows the case when the rotational load torque is greater than or equal to the predetermined value. The right figures of Figures 19(a) and (b) are cross-sectional views showing a cross section (section BB in the left figure) that is approximately perpendicular to the rotation axis direction of the driven top 202. Figure 19(a) shows the case when the rotational load torque is less than a predetermined value, and Figure 19(b) shows the case when the rotational load torque is greater than or equal to the predetermined value. The left diagram of Figures 20(a) and (b) is a cross-sectional view (section AA in the right diagram) that is approximately perpendicular to the rotation axis direction of the drive spool 201 and the driven spool 202, in order to explain the direction of the spring force of the torsion spring. Figure 20(a) shows the situation when the rotational load torque is less than a predetermined value, and Figure 20(b) shows the situation when the rotational load torque is greater than or equal to a predetermined value.

[0091] The drive spool 201 is configured to engage with the driven spool 202 with rotational play, i.e., a predetermined gap G (Figure 20(a)), and transmit rotational driving force to the driven spool 202 (Figures 16 and 20). One end 203a of the torsion spring 203 engages with a locking groove 201c provided on the drive spool 201, and the other end 203b of the torsion spring 203 engages with a locking groove 202c provided on the driven spool 202 (Figures 16 and 20). The torsion spring 203 is located between the drive spool 201 and the driven spool 202. Furthermore, the drive spindle 201 is provided with a first notch (engagement groove) 201d and a second notch (engagement groove) 201e that receive an elastically deformable stopper 205 provided on the driven spindle 202 (Figure 16). The first notch 201d and the second notch 201e are provided along the rotational direction (circumferential direction) of the drive spindle 201.

[0092] The torsion spring 203 biases the drive spool 201 and the driven spool 202 in the rotational direction with a predetermined spring force. When there is no rotational load torque, the first contact surface 201a of the drive spool 201 and the first contact surface 202a of the driven spool 202 are in contact (Figures 18, 19, and 20). Also, when there is no rotational load torque, the stopper 205 is received in the first notch 201d (Figures 17(a) and 20(a)). The spring force (spring pressure) of the torsion spring 203 is set to a predetermined rotational load torque when the waste toner transport screw 113 transports the waste toner in the waste toner collection container 10 when the waste toner collection container 10 is nearly full. As will be described later, after the rotational load torque exceeds a predetermined value, the stopper 205 is received in the second notch 201e, maintaining the relative position (phase) of the driven spool 202 with respect to the driven spool 201 in the rotational direction of the driven spool 201 (Figure 17(b)).

[0093] As shown in Figures 18 and 19, the detection flag 204 is provided with a first engagement portion 204a with a round hole shape and a second engagement portion 204b with an elongated hole shape. The detection flag 204 is positioned between the drive 201 and the driven 202, with the second engagement portion 204b slidably engaged with the boss 201f of the drive 201 and the first engagement portion 204a rotatably engaged with the boss 202d of the driven 202. The detection flag 204 can protrude away from the rotational axes of the drive 201 and the driven 202, and retract towards the rotational axes, as the relative position of the drive 201 and the driven 202 changes. As shown in Figure 17, the printer 1 is provided with a detection sensor 131 close to the detection flag 204. In this embodiment, the detection sensor 131, as a detection means, is composed of a light-shielding, light-transmitting detection sensor (photosensor) similar to that in Embodiment 1. The detection sensor 131 is configured in a U-shape in cross-section and has a light-emitting section 131a, a light-receiving section 131b, and a detection area 131c formed between the light-emitting section 131a and the light-receiving section 131b. When the detection flag 204 protrudes from the drive hub 201 and the driven hub 202, the light-shielding section 204c of the detection flag 204 enters the detection area 131c of the detection sensor 131, blocking the optical axis of the detection light. In this embodiment, the torque detection mechanism 200 is configured with a drive coupling mechanism 220 having a drive hub 201, a driven hub 202, a torsion spring 203, and a detection flag 204, and the detection sensor 131. In this embodiment, the torque detection mechanism 200 can detect whether the driven spool 202 is in the first phase or the second phase by having the detection sensor 131 detect the state of light shielding and transmission of the detection light.

[0094] In the configuration described above, when a driving force is input to the drive spool 201 and the rotational load torque of the waste toner transport screw 113 is less than a predetermined value, the driven spool 202 is pulled towards the drive spool 201 by the spring force of the torsion spring 203. The arrows in Figure 20(a) indicate the direction of the force acting by the spring force of the torsion spring 203 at this time. Then, the drive spool 201 and the driven spool 202 rotate with the first contact surface 201a of the drive spool 201 and the first contact surface 202a of the driven spool 202 in contact (with a gap G). At this time, the detection flags 204 engaged with the drive spool 201 and the driven spool 202 respectively rotate in a state where they do not protrude from the drive spool 201 and the driven spool 202 (retracted position) (Figures 17(a), 18(a), and 19(a)).

[0095] When the rotational load torque of the waste toner transport screw 113 exceeds a predetermined value, the relative position (phase) of the driven spool 202 with respect to the driven spool 201 in the rotational direction of the driven spool 201 changes to the upstream side, against the spring force of the torsion spring 203. The arrows in Figure 20(b) indicate the direction of the force acting due to the spring force of the torsion spring 203 at this time. Then, the gap G between the driven spool 201 and the driven spool 202 disappears, the second contact surface 201b of the driven spool 201 and the second contact surface 202b of the driven spool 202 come into contact, and the driven spool 202 rotates along with the driven spool 201. At this time, due to the change in the relative position of the drive top 201 and the driven top 202 in the rotational direction, the detection flag 204 rotates in a state where it protrudes from both the drive top 201 and the driven top 202 (protruding position) (Figures 17(b), 18(b), and 19(b)).

[0096] When the detection flag 204 rotates in a protruding state (protruding position), the detection flag 204 obstructs the optical axis of the detection light of the detection sensor 131 during the rotation period of the drive spool 201 and the driven spool 202. By detecting this with the detection sensor 131, it is possible to detect that the waste toner collection container 10 is nearly full. When the nearly full state is detected, the relative position (phase) of the driven spool 202 with respect to the drive spool 201 in the rotation direction of the drive spool 201 changes, and the stopper 205 of the driven spool 202 disengages from the first notch 201d of the drive spool. The stopper 205 of the driven spool 202 then rotates while bending radially inward and is received by the second notch 202e of the drive spool 201. After the nearly full state is detected, the stopper 205 remains received by the second notch 201e.

[0097] In this embodiment, the driven spool 202, which is engaged with the driven spool 201 with a predetermined gap G in the rotational direction, is biased by the torsion spring 203 in a direction that expands the gap G in the rotational direction. When the rotational load torque of the waste toner transport screw 113 exceeds a predetermined value, the rotational load torque acting on the driven spool 202 also exceeds a predetermined value, and the relative position (phase) of the driven spool 202 with respect to the driven spool 201 in the rotational direction changes. In other words, the gap G between the driven spool 201 and the driven spool 202 changes. As a result, the detection flag 204 protrudes, and this protruding detection flag 204 is detected by the detection sensor 131. The stopper 205 of the driven spool 202 moves from the first notch 201d to the second notch 201e of the driven spool 201 when a near-full state is detected. The stopper 205 has a shape that restricts the relative position (phase) of the driven spool 202 with respect to the driven spool 201 in the rotational direction of the driven spool 201 from shifting. Therefore, once the torque detection mechanism 200 changes to a state in which a near-full state is detected, the stopper 205 is restricted from moving away from the second notch 202e and to a position where it is received by the first notch 202d. As mentioned above, if the state of the waste toner in the waste toner collection container 10 changes due to factors such as vibration, and the transport resistance of the waste toner transport screw 113 decreases, the rotational load torque of the waste toner transport screw 113 may decrease. In this embodiment, even in this case, the relative position (phase) of the non-driven spool 202 with respect to the driven spool 201 in the rotational direction of the driven spool 201 does not change. Therefore, even if the rotational load torque of the waste toner transport screw 113 falls below a predetermined value, the detection flag 204 remains in the protruding position and is restricted from returning to the retracted position. In other words, the torque detection mechanism 200 can maintain the state of detecting a near-full state even if, after detecting a near-full state, the state of waste toner in the waste toner collection container 10 changes due to factors such as vibration, and the rotational load torque of the waste toner transport screw 113 decreases.

[0098] In this embodiment, the driven hub 202 is provided with a stopper 205 as an engaging portion that engages with the drive hub 201 to restrict changes in the phase of the driven hub 202. However, instead of or in addition to this, the drive hub 201 may also be provided with an engaging portion that engages with the driven hub 202 to restrict changes in the phase of the driven hub 202.

[0099] Thus, in this embodiment, the image forming apparatus 1 has a biasing member (torsion spring) 203 that engages with the first rotating body (driver) 201 and the second rotating body (driven) 202, and applies a biasing force between the first rotating body 201 and the second rotating body 202 along the rotational direction of the first rotating body 201. The biasing member 203 deforms such that when the second rotating body 202 is in the second phase (rotational load torque is above a predetermined value) rather than when the second rotating body 202 is in the first phase (rotational load torque is below a predetermined value), the second rotating body 202 is positioned more upstream relative to the first rotating body 201 in the rotational direction of the first rotating body 201. In this embodiment, the detection means comprises a flag (detection flag) 204 whose position changes in conjunction with the phase change of the second rotating body 202 relative to the first rotating body 201, such that it is located in a first position when the second rotating body 202 is in the first phase and in a second position when the second rotating body 202 is in the second phase, and a sensor (detection sensor) 131 capable of detecting that the flag 204 is in the second position. In this embodiment, the sensor 131 is configured to have a photosensor that detects at least one of the shielding or transmission of detection light due to the change in the position of the flag 204. In this embodiment, the regulating means comprises at least one of an engaging portion provided on the first rotating body 201 that engages with the second rotating body 202 when the second rotating body 202 is in the second phase, or an engaging portion (stopper) 205 provided on the second rotating body 202 that engages with the first rotating body 201 when the second rotating body 202 is in the second phase.

[0100] As described above, the same effects as in Example 1 can be obtained with the configuration of this embodiment.

[0101] [Example 3] Next, other embodiments of the present invention will be described. In this embodiment, another example of a torque detection mechanism that detects when the rotational load torque of the waste toner transport screw exceeds a predetermined value (overload condition) 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, 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.

[0102] Figure 21 is a perspective view showing the overall configuration of the torque detection mechanism 300 in this embodiment. Figure 22 is an exploded perspective view showing the components of the drive coupling mechanism 320 in this embodiment in a disassembled state.

[0103] As shown in Figures 21 and 22, the torque detection mechanism 300 includes a first rotating body (first member, rotating member) 311 positioned on the input side of the rotational driving force, a second rotating body (first member, rotated member) 312 provided coaxially and rotatably with respect to the first rotating body 311 and positioned on the output side of the rotational driving force, a torsion spring 313 as an example of a biasing member (elastic member) that applies a biasing force (elastic force) along the direction of rotation between the first rotating body 311 and the second rotating body 312, and a light-shielding and light-transmitting detection sensor 131 as an example of a detection means for detecting the phase difference in the rotation angle between the first rotating body 311 and the second rotating body 312. The first rotating body 311 and the second rotating body 312 are each rotatably supported with respect to the rotation shaft 315. The first rotating member 311 transmits the driving force input to the drive roller 46 to the second rotating member 312. The second rotating member 312 transmits the driving force received from the first rotating member 311 to the waste toner transport screw 113, causing the waste toner transport screw 113 to rotate. The first rotating member 311 rotates in the direction of arrow R5 in the figure. The second rotating member 312 rotates in the direction of arrow R6 in the figure. As with Embodiment 1, in this embodiment, the rotational drive direction of the drive roller 46 that drives the belt 41 is unidirectional, and the first rotating member 311 does not rotate in the reverse direction. In this embodiment, the drive coupling mechanism 320 is configured with the first rotating body 311, the second rotating body 312, and the torsion spring 313. The detection sensor 131 may have the same configuration as in Embodiments 1 and 2.

[0104] Figure 23 is a perspective view of the first rotating body 311. Figure 23(a) shows the front surface of the first rotating body 311 (the surface opposite to the second rotating body 312 in the direction of the rotation axis of the first rotating body 311), and Figure 23(b) shows the back surface of the first rotating body 311 (the surface on the second rotating body 312 side in the direction of the rotation axis of the first rotating body 311). Figure 24 is a perspective view of the second rotating body 312. Figure 24(a) shows the front surface of the second rotating body 312 (the surface opposite to the first rotating body 311 in the direction of the rotation axis of the second rotating body 312), and Figure 24(b) shows the back surface of the second rotating body 312 (the surface on the first rotating body 311 side in the direction of the rotation axis of the second rotating body 312). Figure 25 is a cross-sectional view of the torque detection mechanism 300 as seen from the second rotating body 312 side along the rotation axis of the first rotating body 311. Figure 26 is a perspective view of the torsion spring 313.

[0105] As shown in Figure 23, the first rotating body 311 has a cylindrical shaft support portion 311b with an insertion hole 316a in the center into which a rotating shaft 315 is inserted. The first rotating body 311 also has a disc portion 311d formed on one side of the shaft support portion 311b, which has a larger outer diameter (diameter) than the shaft support portion 311b. The first rotating body 311 also has a flange portion 311e formed on the outer peripheral end of the disc portion 311d so as to form part of a cylindrical shape, standing upright along the axial direction. The first rotating body 311 also has a first rotation angle detection portion 311a formed in a fan shape on the outer peripheral surface of the tip of the flange portion 311e along the axial direction, so as to make a predetermined central angle β smaller than the central angle α of the flange portion 311e, extending radially outward. The first rotating body 311 integrally comprises the pivot portion 311b, the disc portion 311d, the flange portion 311e, and the first rotation angle detection portion 311a. Furthermore, the insertion hole 316a for the pivot portion 311b is provided through the center of the disc portion 311d. Simultaneously, a cylindrical mounting portion 316 for mounting a torsion spring 313 is provided at the center of the disc portion 311d, having the same height (length) as the flange portion 311e along the axial direction. Additionally, a first locking groove 311c is formed in the flange portion 311e at a position corresponding to one end portion 311a2 of the first rotation angle detection portion 311a, and extends to a depth reaching the surface of the disc portion 311d to engage with the linearly formed end portion 313a of the torsion spring 313. Furthermore, an elastically deformable elastic engaging claw 314 is provided at one circumferential end of the flange portion 311e, such that its tip protrudes toward the second rotating body 312 along the rotation axis direction of the first rotating body 311. The first rotating body 311 is rotatably mounted on the rotating shaft 315. The first rotating body 311 may be configured as a simple rotating body, or it may be configured as a gear that transmits rotational driving force by forming teeth such as spur teeth on the outer circumference of the shaft support portion 311b.

[0106] The first rotation angle detection unit (first flag) 311a of the first rotating body 311 is for detecting the rotation angle of the first rotating body 311 by blocking light from the detection sensor 131. However, detecting the rotation angle of the first rotating body 311 does not mean detecting an absolute angle with respect to a certain position. Detecting the rotation angle of the first rotating body 311 means detecting the difference in rotation angles between it and the second rotating body 312, that is, detecting the rotation angles of the first rotating body 311 and the second rotating body 312 as a phase difference. Normally, of the fan-shaped first rotation angle detection unit 311a, one end edge 311a1 along the rotation direction (circumferential direction) is detected by the detection sensor 131. Furthermore, one end 313a of a torsion spring 313 is locked to the vicinity of the other end 311a2 of the first rotation angle detection unit 311a of the first rotating body 311, and the other end 311a2 of the first rotation angle detection unit 311a is the point on which rotational force acts. In addition, the elastic engaging claw 314 is used to maintain the phase difference between the first rotating body 311 and the second rotating body 312 when the rotational load torque acting on the first rotating body 311 and the second rotating body 312 exceeds a predetermined value.

[0107] On the other hand, as shown in Figure 24, the second rotating body 312 has a cylindrical shaft support portion 312b with an insertion hole 316b in the center into which a rotating shaft 315 is inserted. The second rotating body 312 also has a second rotation angle detection portion 312a formed in a fan shape on one side of the shaft support portion 312b so as to form a predetermined central angle γ radially outward. The second rotating body 312 also has a pair of locking protrusions 312e and 312f formed on the outer surface of the second rotation angle detection portion 312a and arranged opposite each other with a predetermined gap between them, for locking the other linearly formed end portion 312a2 of the torsion spring 313. The pair of locking protrusions 312e and 312f are arranged so that their outer circumferential surfaces coincide with the outer circumference of the flange portion 311e of the first rotating body 311 (Figure 25). Furthermore, the second rotating body 312 has an arc portion 312d with a smaller outer diameter formed within the opening of the second rotation angle detection unit 312a. The arc portion 312d is formed to have, for example, the same outer diameter as the disc portion 311d of the first rotating body 311. In addition, the second rotating body 312 has a first notch (engagement hole) 314a and a second notch (engagement hole) 314b formed in the second rotation angle detection unit 312a for receiving the elastic engagement claw 314 provided on the first rotating body 311. The first notch 314a and the second notch 314b are arranged along the outer circumference of the flange portion 311e of the first rotating body 311. The second rotating body 312 is rotatably mounted with respect to the rotation shaft 315. The second rotating body 312 may be configured as a simple rotating body, or it may be configured as a gear that transmits rotational driving force by forming teeth such as spur teeth on the outer circumference of the pivot portion 312d.

[0108] The second rotation angle detection unit (second flag) 312a of the second rotating body 312, like the first rotation angle detection unit 311a, is for detecting the rotation angle of the second rotating body 312 by blocking light from the detection sensor 131. However, detecting the rotation angle of the second rotating body 312 does not mean detecting an absolute angle with respect to a certain position. Detecting the rotation angle of the second rotating body 312 means detecting the difference in rotation angles between it and the first rotating body 311, that is, detecting the rotation angles of the second rotating body 312 and the first rotating body 311 as a phase difference. Normally, of the fan-shaped second rotation angle detection unit 312a, one edge 312a1 along the rotation direction (circumferential direction) is detected by the detection sensor 131. The second rotation angle detection unit 312a is formed in a fan shape with a central angle γ (for example, 180 degrees or more) that is larger than the central angle β of the first rotation angle detection unit 311a. Furthermore, the other end 313b of the torsion spring 313 is locked to the vicinity of one end 312a1 of the second rotation angle detection unit 312a of the second rotating body 312, and the vicinity of one end 312a1 of the second rotation angle detection unit 312a is the point where the rotational force acts.

[0109] As shown in Figures 21 and 22, the first rotating body 311 and the second rotating body 312 are arranged with the first rotation angle detection unit 311a and the second rotation angle detection unit 312a overlapping. Initially (when no rotational load torque is acting between them), the first rotating body 311 and the second rotating body 312 are combined as follows: That is, they are combined such that a predetermined angle gap is formed between the edge 311a1 of the first rotation angle detection unit 311a and the edge 312a1 of the second rotation angle detection unit 312a. In other words, in a free state where no rotational load torque is acting, one end 313a of the torsion spring 313 is locked in the groove 311c of the first rotating body 311, and the other end 313b is locked between the pair of locking protrusions 312e and 312f of the second rotating body 312. As a result, a predetermined angle gap is formed between the edge 311a1 of the first rotation angle detection unit 311a and the edge 312a1 of the second rotation angle detection unit 312a. As shown in Figure 26, the torsion spring 313 is set so that the elastic force (torsional rigidity) along the rotational direction of the first rotating body 311 and the second rotating body 312 is a predetermined value.

[0110] The first rotating body 311 and the second rotating body are assembled as follows. The rotating shaft 315 is inserted into the insertion hole 316a of the first rotating body 311, and the torsion spring 313 is inserted into the mounting portion 316 of the first rotating body 311, with one end 313a of the torsion spring 313 locked into the locking groove 311c. The second rotating body 312 is mounted on the rotating shaft 315 via the insertion hole 316b such that the first rotation angle detection portion 311a and the second rotation angle detection portion 312a overlap. At this time, as shown in Figure 25, the other end 313b of the torsion spring 313 is locked into a pair of locking protrusions 312e and 312f of the second rotating body 312. The first rotating body 311 and the second rotating body 312 are each supplied with rotational driving force in the directions of arrows R5 and R6 shown in Figure 21.

[0111] The operating principle of the torque detection mechanism 300 in this embodiment will now be explained. Figure 27 is a front view of the torque detection mechanism 300 for illustrating its operation in this embodiment. Figure 27(a) shows the situation when the rotational load torque is less than a predetermined value, and Figure 27(b) shows the situation when the rotational load torque is greater than or equal to a predetermined value.

[0112] As described above, the rotational driving force from the drive source is input to the first rotating body 311. The rotational driving force input to the first rotating body 311 is transmitted to the second rotating body 312 via the torsion spring 313. Then, the rotational driving force is output from the second rotating body 312 to the waste toner transport screw 113. The first rotating body 311 and the second rotating body 312 are mounted coaxially and rotatably with respect to the rotation axis 315. Furthermore, an elastic force (torsional rigidity) in the direction of rotation is applied between the first rotating body 311 and the second rotating body 312 by the torsion spring 313. When the first rotating body 311 is driven to rotate, the rotational driving force is transmitted to the second rotating body 312 via the torsion spring 313 with torsional rigidity acting on it. At this time, an elastic force corresponding to the rotational load torque acts on the torsion spring 313. As a result, the second rotating body 312 is driven to rotate with a delay of the first rotating body 311 by a phase difference of the rotation angle determined according to the rotational load torque.

[0113] As shown in Figures 27(a) and (b), the torque detection mechanism 300 is set so that a predetermined phase difference initially exists between the first rotation angle detection unit 311a and the second rotation angle detection unit 312a when no rotational load torque is acting between the first rotating body 311 and the second rotating body 312. As shown in Figure 27(a), when no rotational load torque is acting between the first rotating body 311 and the second rotating body 312, the elastic engaging claw 314 of the first rotating body 311 is received by the first notch 314b of the second rotating body 312. Also, as shown in Figure 27(b), when the rotational load torque of the waste toner transport screw 113 exceeds a predetermined value and a near-full state is detected, the elastic engaging claw 314 of the first rotating body 311 rotates while bending along the rotation axis direction of the first rotating body 311 and is received by the second notch 314b of the second rotating body 312. Then, after the near-full state is detected, the elastic engaging claw 314 is maintained in a state where it is received in the second notch 314b.

[0114] Figure 28 is a schematic diagram showing a state in which the angle between the first rotation angle detection unit 311a and the second rotation angle detection unit 312a, i.e., the phase difference, differs depending on the magnitude of the rotational load torque. Figure 28(a) shows the state when the rotational load torque is less than a predetermined value, Figure 28(b) shows the state just before the rotational load torque exceeds the predetermined value, and Figure 28(c) shows the state when the rotational load torque is above the predetermined value.

[0115] As the rotational load torque increases, the difference in rotation angles (phase difference) between the first rotation angle detection unit 311a and the second rotation angle detection unit 312a increases, and when a predetermined phase difference is reached, a near-full state is detected. Therefore, by detecting the phase difference between the first rotation angle detection unit 311a and the second rotation angle detection unit 312a using the exposure time of the detection sensor 131, it becomes possible to detect the rotational load torque. With this configuration, compared to detecting the rotational load torque by detecting the current flowing through the drive source, it is not necessary to detect the current flowing through the drive source, and the rotational load torque can be detected at any position where the driving force is transmitted, thereby improving the degree of freedom of the detection position.

[0116] Furthermore, when a near-full state is detected, the elastic engaging claw 314 of the first rotating body 311 moves from the first notch 314a to the second notch 314b of the second rotating body 312. The elastic engaging claw 314 has a shape that restricts the shift in the relative position (phase) of the second rotating body 312 with respect to the first rotating body 311 in the rotational direction of the first rotating body 311. Therefore, once the torque detection mechanism 300 changes to a state where a near-full state is detected, the elastic engaging claw 314 is restricted from moving from the second notch 314b to a position where it is received by the first notch 314a. As mentioned above, if the state of the waste toner in the waste toner collection container 10 changes due to factors such as vibration, and the transport resistance of the waste toner transport screw 113 decreases, the rotational load torque of the waste toner transport screw 113 may decrease. In this embodiment, even in this case, the relative position (phase) of the second rotating body 312 with respect to the first rotating body 311 in the rotational direction of the first rotating body 311 does not change. Therefore, even if the rotational load torque of the waste toner transport screw 113 falls below a predetermined value, the first rotating body 311 and the second rotating body 312 maintain a predetermined phase difference, preventing them from returning to the state in which the rotational load torque before the near-full state was detected was acting. In other words, even if the state of the waste toner in the waste toner collection container 10 changes due to factors such as vibration after the torque detection mechanism 300 detects the near-full state, and the rotational load torque of the waste toner transport screw 113 decreases, the torque detection mechanism 300 can maintain the state in which the near-full state was detected.

[0117] In this embodiment, the first rotating body 311 is provided with an elastic engaging claw stopper 205, which acts as an engaging portion that engages with the second rotating body 312 to restrict changes in the phase of the second rotating body 312. However, instead of or in addition to this, the second rotating body 312 may be provided with an engaging portion that engages with the first rotating body 311 to restrict changes in the phase of the second rotating body 312.

[0118] Thus, in this embodiment, the detection means comprises a first flag (first rotation angle detection unit) 311a provided on the first rotating body 311, a second flag (second rotation angle detection unit) 312a provided on the second rotating body 312, wherein the second flag (second rotation angle detection unit) 312a has a first position relative to the first flag 311a in the rotation direction of the first rotating body 311 when the second rotating body 312 is in a first phase (a state in which the rotation load torque is less than a predetermined value), and a second position relative to the first flag 311a in the rotation direction of the first rotating body 311 when the second rotating body 312 is in a second phase (a state in which the rotation load torque is greater than or equal to a predetermined value), and a sensor (detection sensor) 131 capable of detecting that the relative position of the second flag 312a with respect to the first flag 311a in the rotation direction of the first rotating body 311 is in the second position. In this embodiment, the sensor 131 is configured to have a photosensor that detects a change in at least one of the states of light shielding or transmission of detection light due to a change in the relative position of the first flag 311a and the second flag 312a in the rotation direction of the first rotating body 311. In this embodiment, the regulating means is configured to have at least one of the following: an engaging portion (elastic engaging claw) 314 provided on the first rotating body 311 that engages with the second rotating body 312 when the second rotating body 312 is in the second phase, or an engaging portion provided on the second rotating body 312 that engages with the first rotating body 311 when the second rotating body 312 is in the second phase.

[0119] As described above, the same effects as in Example 1 can be obtained with the configuration of this embodiment.

[0120] [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.

[0121] In general, mechanical devices are equipped with various rotating members. For example, in image forming devices such as printers, copiers, and multifunction devices, rotating members are used in process units necessary for image formation. In the above embodiment, the waste toner transport screw that transports waste toner in the waste toner collection container was used as an example of a device to detect when the rotational load torque exceeds a predetermined value (overload condition). However, the detection target is not limited to the waste toner transport screw. For example, it may be desirable to detect when process means such as the toner transport screw of a replenishment device that replenishes toner in a developing device, or the developing roller of a developing device, have entered an overload condition. The present invention can also be applied to such other detection targets.

[0122] Furthermore, waste toner is not limited to residual toner remaining on the image carrier after the transfer process. For example, in an image forming apparatus, toner (developer including toner and carrier in the case of a two-component developer) may be discharged from the developer to refresh the developer in the developer unit. Also, adjustment toner images (patches) that are not transferred to the recording material may be formed on the image carrier. The waste toner collected in the waste toner collection container includes any of these toners (which may include carriers). In addition, the toner removed from the image carrier is not limited to the toner removed from the intermediate transfer belt, but may also include the toner removed from the photosensitive drum.

[0123] Furthermore, in the above-described embodiment, the state in which the rotational load torque of the waste toner transport screw exceeds a predetermined value was described as the state in which the waste toner collection container is nearly full. However, for example, it could also be the state in which the waste toner collection container is full.

[0124] Furthermore, in the above-described embodiment, it was explained that the waste toner transport screw receives driving force from a drive source that rotates the belt (drive roller), but the image forming apparatus may have a separate drive source that rotates the waste toner transport screw.

[0125] Furthermore, although the above embodiment described an example where a photosensor is used as the detection sensor, a mechanical switch that is turned ON / OFF by a flag may also be used as the detection sensor.

[0126] Furthermore, by using multiple sets of first and second rotating bodies and multiple detection means, it is also possible to detect torque overload in multiple stages. For example, an image forming apparatus may have, in addition to the aforementioned first rotating body, second rotating body, and detection means, a third rotating body provided coaxially with the first rotating body and rotated by the second rotating body with driving force transmitted from a drive source; a fourth rotating body provided coaxially with the first rotating body and rotated by the third rotating body with driving force transmitted from a drive source and transmitting driving force toward a driven member, wherein the fourth rotating body is rotatable relative to the third rotating body from a third phase to a fourth phase, where the phase of the fourth rotating body relative to the third rotating body in the rotation direction of the third rotating body is different; and another detection means capable of detecting that the fourth rotating body is in the fourth phase. The third and fourth rotating bodies are configured such that when the rotational load torque of the driven member is a third torque different from the first and second torques described above, the fourth rotating body rotates in the third phase, and when the rotational load torque of the driven member is a fourth torque different from the first and second torques described above and greater than the third torque, the fourth rotating body rotates in the fourth phase, so that the phase of the fourth rotating body changes as the rotational load torque of the driven member changes from the third torque to the fourth torque. The image forming apparatus is configured to have another restricting means that prevents the phase of the fourth rotating body from returning from the fourth phase to the third phase, even if the rotational load torque of the driven member decreases from the fourth torque to the third torque when the phase of the fourth rotating body changes from the third phase to the fourth phase. [Explanation of Symbols]

[0127] 1. Image forming apparatus 10 Waste toner collection container 40 Transfer Units 41 Intermediate transfer belt 43 Cleaning Department 46 drive rollers 100 Torque detection mechanism 113 Waste Toner Transport Screw 120 Drive coupling mechanism 121 Movable Gear 122 Fixed Gear 123 Detection lever 124. Biasing spring 130 detection flag 131 Detection Sensor 200 Torque detection mechanism 220 Drive coupling mechanism 300 Torque detection mechanism 320 Drive coupling mechanism

Claims

1. The driven member and, A drive source that generates a driving force to rotate the driven member, A first rotating body that rotates when a driving force is input from the aforementioned drive source, A second rotating body is provided coaxially with the first rotating body, rotates when the driving force from the drive source is transmitted by the first rotating body, and transmits the driving force toward the driven member, wherein the second rotating body is rotatable relative to the first rotating body from a first phase to a second phase, where the phases of the relative positions of the second rotating body with respect to the first rotating body in the rotational direction of the first rotating body are different, A detection means capable of detecting that the second rotating body is in the second phase, An image forming apparatus having, The first and second rotating bodies are configured such that when the rotational load torque of the driven member is a first torque, the second rotating body rotates in the first phase, and when the rotational load torque of the driven member is a second torque greater than the first torque, the second rotating body rotates in the second phase, such that the phase changes as the rotational load torque of the driven member changes from a first torque to a second torque. An image forming apparatus characterized by having a restricting means for restricting the phase from returning from the second phase to the first phase, even if the rotational load torque of the driven member decreases from the second torque to the first torque when the phase changes from the first phase to the second phase.

2. The first rotating body has a first contact portion that contacts the second rotating body and transmits driving force to the second rotating body when the second rotating body is in the first phase, and a second contact portion that contacts the second rotating body and transmits driving force to the second rotating body when the second rotating body is in the second phase, The second rotating body has a third contact portion that contacts the first contact portion and receives a driving force from the first rotating body when the second rotating body is in the first phase, and a fourth contact portion that contacts the second contact portion and receives a driving force from the first rotating body when the second rotating body is in the second phase. The image forming apparatus according to claim 1, characterized in that when the rotational load torque of the driven member changes from the first torque to the second torque, the relative position of the first contact portion with respect to the third contact portion in the direction of the rotation axis of the first rotating body changes, and the relative position of the first rotating body with respect to the second rotating body in the direction of the rotation axis of the first rotating body changes.

3. The image forming apparatus according to claim 2, characterized in that at least one of the first contact portion or the third contact portion has a surface inclined with respect to the rotation axis direction of the first rotating body.

4. The image forming apparatus according to claim 2, characterized in that at least one of the second contact portion or the fourth contact portion has a surface substantially parallel to the rotation axis direction of the first rotating body.

5. The image forming apparatus according to claim 2, characterized in that the regulating means is configured to have at least one of the following: a regulating portion provided on the first rotating body that contacts the second rotating body when the second rotating body is in the second phase and regulates the change in the relative position of the first rotating body with respect to the second rotating body in the direction of the rotation axis of the first rotating body; or a regulating portion provided on the second rotating body that contacts the first rotating body when the second rotating body is in the second phase and regulates the change in the relative position of the first rotating body with respect to the second rotating body in the direction of the rotation axis of the first rotating body.

6. The image forming apparatus according to claim 2, further comprising a biasing member that applies a biasing force to the first rotating body and the second rotating body in a direction such that they press against each other along the rotation axis direction of the first rotating body.

7. The image forming apparatus according to claim 2, characterized in that the detection means comprises a flag whose position changes in conjunction with a change in phase such that it is located in a first position when the second rotating body is in the first phase and in a second position when the second rotating body is in the second phase, and a sensor capable of detecting that the flag is in the second position.

8. The image forming apparatus according to claim 7, characterized in that the sensor is configured to have a photosensor that detects at least one of the shielding or transmission of detection light due to a change in the position of the flag.

9. The image forming apparatus according to claim 1, comprising a biasing member that engages with the first rotating body and the second rotating body and applies a biasing force between the first rotating body and the second rotating body along the rotational direction of the first rotating body, wherein the biasing member deforms such that the second rotating body is positioned more upstream relative to the first rotating body in the rotational direction of the first rotating body when the second rotating body is in the second phase than when the second rotating body is in the first phase.

10. The image forming apparatus according to claim 9, characterized in that the detection means comprises a flag whose position changes in conjunction with a change in phase such that it is located in a first position when the second rotating body is in the first phase and in a second position when the second rotating body is in the second phase, and a sensor capable of detecting that the flag is in the second position.

11. The image forming apparatus according to claim 10, characterized in that the sensor is configured to have a photosensor that detects at least one of the shielding or transmission of detection light due to a change in the position of the flag.

12. The image forming apparatus according to claim 10, characterized in that the restricting means is provided on the first rotating body and has at least one of the engaging portion that engages with the second rotating body when the second rotating body is in the second phase, or provides on the second rotating body and has at least one of the engaging portion that engages with the first rotating body when the second rotating body is in the second phase.

13. The image forming apparatus according to claim 9, characterized in that the detection means comprises a first flag provided on the first rotating body, a second flag provided on the second rotating body, wherein the relative position of the second rotating body with respect to the first flag in the rotational direction of the first rotating body becomes a first position when the second rotating body is in the first phase, and the relative position of the second rotating body with respect to the first flag in the rotational direction of the first rotating body becomes a second position when the second rotating body is in the second phase, and a sensor capable of detecting that the relative position of the second flag with respect to the first flag in the rotational direction of the first rotating body is the second position.

14. The image forming apparatus according to claim 13, characterized in that the sensor has a photosensor that detects a change in at least one of the states of light shielding or transmission of detection light due to a change in the relative position of the first flag and the second flag in the rotation direction of the first rotating body.

15. The image forming apparatus according to claim 13, characterized in that the restricting means is provided on the first rotating body and has at least one of the engaging portion that engages with the second rotating body when the second rotating body is in the second phase, or provides on the second rotating body and has at least one of the engaging portion that engages with the first rotating body when the second rotating body is in the second phase.

16. A third rotating body is provided coaxially with the first rotating body and rotates by the second rotating body, with the driving force from the drive source being transmitted to it. A fourth rotating body provided coaxially with the first rotating body, which rotates when the driving force from the drive source is transmitted by the third rotating body, and transmits the driving force toward the driven member, wherein the fourth rotating body is rotatable relative to the third rotating body from a third phase to a fourth phase, where the phase of the relative position of the fourth rotating body with respect to the third rotating body in the rotation direction of the third rotating body is different, Another detection means capable of detecting that the fourth rotating body is in the fourth phase, It has, The third and fourth rotating bodies are configured such that when the rotational load torque of the driven member is a third torque different from the first and second torques, the fourth rotating body rotates in the third phase, and when the rotational load torque of the driven member is a fourth torque different from the first and second torques and greater than the third torque, the fourth rotating body rotates in the fourth phase, such that the phase of the fourth rotating body changes as the rotational load torque of the driven member changes from the third torque to the fourth torque. The image forming apparatus according to claim 1, further comprising a restricting means for restricting the phase of the fourth rotating body from returning to the third phase, even if the rotational load torque of the driven member decreases from the fourth torque to the third torque when the phase of the fourth rotating body changes from the third phase to the fourth phase.

17. An image forming unit that forms a toner image, An endless belt onto which the toner image formed in the image forming unit is transferred, A cleaning unit for removing toner from the belt, A waste toner collection container for collecting toner removed from the belt by the cleaning unit, The waste toner transport member in the aforementioned waste toner collection container transports toner, It has, The image forming apparatus according to any one of claims 1 to 16, characterized in that the driven member is the waste toner transport member.

18. The image forming apparatus according to claim 17, characterized in that the second torque is the rotational load torque of the waste toner transport member when the amount of toner contained in the waste toner collection container reaches a predetermined amount.

19. The image forming apparatus according to claim 17, characterized in that a unit including the belt, the cleaning unit, the waste toner collection container, the waste toner transport member, the first rotating body, and the second rotating body is detachably attached to the main body of the image forming apparatus.

Images