Image forming device

Abstract

To correct positional deviation of a cartridge when a cover is opened by a predetermined amount.SOLUTION: An image forming apparatus (1) comprises: a cover 20 that opens and closes an opening 10A of a housing 10; cartridges 50 that each have a photoreceptor (51) and a developing roller 53; a cam (translation cam 60) that brings the developing rollers 53 into contact with the photoreceptors and separates the developing rollers from the photoreceptors; a sensor that detects the cam; and a control unit 100. When the cover 20 opens, the cam is moved by the cover 20 to move in one direction, and when the cover 20 closes, the cam is not moved by the cover 20. When the cover 20 is opened by a predetermined amount or more, the cam is located within a specific range. The control unit 100 specifies the position of the cam based on a signal from the sensor, when determining that the position of the cam is within the specific range, executes initialization driving processing of driving the cartridges 50 for initialization, and when determining that the position of the cam is not within the specific range, does not execute the initialization driving processing.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus having a cover that opens and closes an opening in a housing, and a cartridge that is detachably mountable to the housing through the opening. [Background technology]

[0002] Conventionally, an image forming apparatus has been known that includes a cartridge having a photosensitive drum and a developing roller, a linear cam that brings the developing roller into contact with and separates from the photosensitive drum, a sensor that detects the position of the linear cam, and a control unit that acquires the history of opening and closing of the cover based on a signal from the sensor (see Patent Document 1). Specifically, this technology is configured such that when the cover is moved from the closed position to the open position, the linear cam moves to the frontmost position in conjunction with the cover, and when the cover is moved from the open position to the closed position, the linear cam does not move.

[0003] The control unit determines whether the linear cam is located at the forward-most position based on a signal from the sensor. If the control unit determines that the linear cam is located at the forward-most position, it determines that there is a history of the cover being opened and closed. If the cover has been opened and closed, there is a possibility that the cartridge may be misaligned due to the installation and removal of the cartridge, so the control unit executes a correction process to suppress color misalignment caused by the cartridge being misaligned. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-204838 Summary of the Invention [Problem to be solved by the invention]

[0005] However, even if the cover is opened to an intermediate position between the closed and open positions and then closed, there is a risk that the user may touch the cartridge, causing it to become misaligned. Such misalignment of the cartridge can be corrected by driving the cartridge for initialization.

[0006] However, in the conventional technology, it is only determined that the cover has been opened and closed when the linear cam is positioned in the forwardmost position, i.e., when the cover is fully open, which creates the problem that it is not possible to perform the drive for initializing the cartridge as described above.

[0007] Therefore, an object of the present invention is to provide an image forming apparatus that can correct the cartridge position shift even if the cartridge position shift occurs when the cover is opened by a predetermined amount less than the full open position. [Means for solving the problem]

[0008] In order to solve the above problem, the image forming apparatus of the present invention comprises a housing having an opening, a cover, a cartridge having a photosensitive body and a developing roller, a cam that moves the developing roller between a contact position where it contacts the photosensitive body and a spaced position away from the photosensitive body, a motor that moves the cam, a sensor that detects a detectable portion provided on the cam, and a control unit. The cover moves between a closed position where the opening of the housing is closed and an open position where the opening is open. The cartridge is attachable to and detachable from the housing through the opening. The cam is moved by the cover to move in one direction when the cover moves from the closed position toward the open position, and is not moved by the cover when the cover moves in the direction from the open position toward the closed position. The cam is positioned in a specific range when the cover is opened by a predetermined amount or more. The control unit executes a cam position specifying process for specifying the position of the cam based on the signal from the sensor. If the control unit determines that the position of the cam is within the specific range, it executes an initialization drive process to drive the cartridge for initialization, and if it determines that the position of the cam is not within the specific range, it does not execute the initialization drive process.

[0009] With this configuration, even if the user touches the cartridge while the cover is open a predetermined amount, causing the cartridge to shift out of position, the control unit determines that the cam is within a specific range and executes an initialization drive process, thereby correcting the cartridge's position shift.

[0010] The image forming device may also be provided with a cover sensor that detects whether the cover is in the closed position, and the control unit may execute the cam position identification process when the cover is in the closed position based on a signal from the cover sensor.

[0011] The control unit may also execute the cam position specifying process when started up.

[0012] In addition, the control unit may move the cam in the cam position identification process and identify the position of the cam based on a change in the signal of the sensor.

[0013] According to this configuration, even if the absolute position of the cam cannot be obtained by the sensor, the position of the cam can be identified based on a change in the signal of the sensor.

[0014] The control unit may also determine the direction of movement of the cam based on a detection result of the sensor when the cam position identification process is started.

[0015] Furthermore, the cover may be movable between a first intermediate position between the closed position and the open position and a second intermediate position closer to the open position than the first intermediate position, the cam may be movable from a first position to a second position when the cover moves from the closed position to the first intermediate position, may be movable from the second position to a third position when the cover moves from the first intermediate position to the second intermediate position, and may be movable from the third position to a fourth position when the cover moves from the second intermediate position to the open position, and the control unit may perform the initialization drive process if the cam is located at the third position or the fourth position when the cam position identification process is started, and may not perform the initialization drive process if the cam is located at the first position or the second position when the cam position identification process is started.

[0016] In addition, the control unit may separate the developing roller from the photosensitive member by positioning the cam at the first position in a standby state in which no printing is performed.

[0017] Furthermore, when the cam is located at the third position or the fourth position, the developing roller may come into contact with the photosensitive member.

[0018] According to this configuration, when the cover is opened and the cartridge is removed, the developing roller can be brought into contact with the photosensitive member.

[0019] The image forming device may also include a plurality of cartridges, and the cam may be a linear cam extending in the arrangement direction of the cartridges, displacing the developing roller in each of the cartridges to the contact position or the separated position.

[0020] According to this configuration, the developing rollers of the plurality of cartridges can be displaced by one linear cam. [Effects of the Invention]

[0021] According to the present invention, even if the cartridge is misaligned when the cover is opened by a predetermined amount less than the full open position, the misalignment of the cartridge can be corrected. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 2 is a diagram showing a color printer according to an embodiment, in which a translation cam is located at a first position. [Figure 2] FIG. 10 is a diagram showing the color printer, illustrating a state in which the linear cam is located at a second position. [Figure 3] FIG. 10 is a diagram showing the color printer, illustrating a state in which the linear cam is located at a third position. [Figure 4] FIG. 10 is a diagram showing the color printer, illustrating a state in which the linear cam is located at a fourth position. [Figure 5] These figures show the relationship between the detected part of the linear cam and the sensor, with (a) showing the linear cam in a first position, (b) showing the linear cam in a second position, (c) showing the linear cam in a third position, and (d) showing the linear cam in a fourth position. [Figure 6] 10 is a flowchart showing a part of an initialization process. [Figure 7] 10 is a flowchart showing another part of the initialization process. [Figure 8] 10A to 10C show the relationship between the linear cam and the sensor when the cam position identification process is executed when the linear cam is in the first position at the start of the cam position identification process, and FIG. 10D shows the waveform of the sensor signal. [Figure 9] 10A to 10D are diagrams showing the relationship between the linear cam and the sensor when the cam position identification process is executed when the linear cam is in the third position at the start of the cam position identification process, and FIG. 10E is a diagram showing the waveform of the sensor signal. [Figure 10]10A and 10B show the relationship between the linear cam and the sensor when the cam position identification process is executed when the linear cam is in the second position at the start of the cam position identification process, and FIG. 10C shows the waveform of the sensor signal. [Figure 11] 10A to 10C show the relationship between the linear cam and the sensor when the cam position identification process is executed when the linear cam is in the fourth position at the start of the cam position identification process, and FIG. 10D shows the waveform of the sensor signal. DETAILED DESCRIPTION OF THE INVENTION

[0023] Next, the embodiments will be described in detail with reference to the drawings as appropriate. As shown in FIG. 1, a color printer 1, which is an example of an image forming apparatus, includes a housing 10, a cover 20, a supply unit 30, and an image forming unit 40.

[0024] Housing 10 has an opening 10A at the top. Cover 20 is movable between a closed position (position in FIG. 1) in which opening 10A of housing 10 is closed, and an open position (position shown by the two-dot chain line in FIG. 4) in which opening 10A is open. Specifically, cover 20 is rotatable about axis X1.

[0025] The supply unit 30 is provided at the bottom inside the housing 10. The supply unit 30 includes a supply tray 31 and a supply mechanism (not shown). The supply tray 31 is a tray that stores sheets S. The supply mechanism includes a pickup roller and the like, and transports the sheets S stored in the supply tray 31 to the image forming unit 40.

[0026] The image forming section 40 includes four LED units 41, four cartridges 50, a transfer unit 70, and a fixing unit 80.

[0027] The four LED units 41 are provided corresponding to the four photosensitive drums 51, respectively. The LED units 41 expose the surfaces of the photosensitive drums 51 by blinking the light-emitting portions based on image data, and form electrostatic latent images on the photosensitive drums 51.

[0028] The cartridges 50 are indicated by the symbols 50Y, 50M, 50C, and 50K containing toner of each color, yellow, magenta, cyan, and black, and are arranged in this order from upstream in the conveyance direction of the sheet S. In this specification and drawings, when specifying the photosensitive drum 51, developing roller 53, etc. corresponding to the toner color, the symbols Y, M, C, and K will be used to correspond to yellow, magenta, cyan, and black, respectively.

[0029] In this specification and drawings, the arrangement direction of the four cartridges 50 is also referred to as the "front-rear direction." Furthermore, when the cover 20 is in the closed position, the tip end side of the cover 20 is also referred to as the "front side," and the base end side of the cover 20 is also referred to as the "rear side."

[0030] The cartridge 50 has a photosensitive drum 51 as an example of a photosensitive member, a charger 52, and a developing roller 53. The cartridge 50 is detachable from the housing 10 through the opening 10A when the cover 20 is in the open position.

[0031] The developing roller 53 is movable between a contact position (position in FIG. 3) where it contacts the photosensitive drum 51 and a separation position (position in FIG. 1) where it is separated from the photosensitive drum 51. The structure for moving the developing roller 53 will be described in detail later.

[0032] The transfer unit 70 is provided vertically between the supply unit 30 and the four photosensitive drums 51. The transfer unit 70 includes a drive roller 71, a driven roller 72, a conveyor belt 73, and four transfer rollers 74.

[0033] The drive roller 71 and the driven roller 72 are arranged to be spaced apart in the front-rear direction. The conveyor belt 73 is an endless belt. The conveyor belt 73 is wound around the drive roller 71 and the driven roller 72. Four transfer rollers 74 are arranged inside the conveyor belt 73 and sandwich the conveyor belt 73 between the corresponding photosensitive drums 51.

[0034] The fixing unit 80 includes a heating roller 81 and a pressure roller 82 that sandwiches the sheet S between the heating roller 81 and the pressure roller 82.

[0035] In the image forming unit 40, first, the surface of the photosensitive drum 51 is charged by the charger 52 and then exposed by the LED unit 41. As a result, an electrostatic latent image is formed on the photosensitive drum 51. Thereafter, the developing roller 53 supplies toner to the electrostatic latent image on the photosensitive drum 51, thereby forming a toner image on the photosensitive drum 51.

[0036] Next, the sheet S supplied onto the conveyor belt 73 passes between the photosensitive drum 51 and the transfer roller 74. At this time, the toner image on the photosensitive drum 51 is transferred onto the sheet S being conveyed by the conveyor belt 73. Then, the fixing device 80 thermally fixes the toner image transferred onto the sheet S onto the sheet S.

[0037] The color printer 1 further includes a linear cam 60 as an example of a cam, a motor MT, a locking mechanism R, and a control unit 100.

[0038] The linear cam 60 is a member that moves the developing roller 53 between a contact position and a separated position. More specifically, the linear cam 60 is a plate-shaped member that extends in the arrangement direction of the four cartridges 50, and displaces the developing roller 53 in each of the four cartridges 50 to the contact position or the separated position.

[0039] The linear cam 60 is movable to a first position shown in FIG. 1, a second position shown in FIG. 2, a third position shown in FIG. 3, and a fourth position shown in FIG. 4. The first position is the rearmost position. The second position is a position further forward than the first position. The third position is a position further forward than the second position. The fourth position is the frontmost position.

[0040] When the linear cam 60 is located at the first position, it separates all of the developing rollers 53Y, 53M, 53C, and 53K from the corresponding photosensitive drums 51Y, 51M, 51C, and 51K. When the linear cam 60 is located at the second position, it brings only the black developing roller 53K into contact with the photosensitive drum 51K, and separates the developing rollers 53Y, 53M, and 53C of the other three colors from the corresponding photosensitive drums 51Y, 51M, and 51C. When the linear cam 60 is located within a specific range from the third position to the fourth position, it brings all of the developing rollers 53Y, 53M, 53C, and 53K into contact with the corresponding photosensitive drums 51Y, 51M, 51C, and 51K.

[0041] The linear cam 60 is configured to be moved in one direction, specifically forward, by the cover 20 when the cover 20 moves in the direction from the closed position toward the open position. The linear cam 60 is configured not to be moved by the cover 20 when the cover 20 moves in the direction from the open position toward the closed position.

[0042] The cover 20 is movable among a closed position shown by solid lines in FIGS. 1 to 4, a first intermediate position shown by two-dot chain lines in FIG. 2, a second intermediate position shown by two-dot chain lines in FIG. 3, and an open position shown by two-dot chain lines in FIG. 4. The first intermediate position is a position between the closed position and the open position. The second intermediate position is a position closer to the open position than the first intermediate position. Specifically, the angle from the closed position to the first intermediate position (the amount of movement of the cover 20) is smaller than the angle from the first intermediate position to the open position. The angle from the closed position to the second intermediate position (the amount of movement of the cover 20) is larger than the angle from the second intermediate position to the open position.

[0043] When the cover 20 moves from the closed position to the first intermediate position, the linear cam 60 is movable from the first position to the second position by the force received from the cover 20. When the cover 20 moves from the first intermediate position to the second intermediate position, the linear cam 60 is movable from the second position to the third position by the force received from the cover 20. When the cover 20 moves from the second intermediate position to the open position, the linear cam 60 is movable from the third position to the fourth position by the force received from the cover 20. When the cover 20 is opened by a predetermined amount or more, more specifically, when it is opened to a position within the range from the second intermediate position to the open position, the linear cam 60 is positioned in a specific range from the third position to the fourth position.

[0044] The motor MT is a motor for moving the linear cam 60. The linear cam 60 is configured to move forward when the motor MT is rotated forward, and to move backward when the motor MT is rotated backward. The control unit 100 has a CPU, ROM, RAM, etc., and is configured to execute various processes in accordance with pre-prepared programs and in response to receiving a print command, etc. The control unit 100 controls the motor MT to switch the position of the linear cam 60 to a first position, a second position, or a third position.

[0045] Specifically, the control unit 100 positions the linear cam 60 at the third position in a color mode in which color printing is performed. The control unit 100 positions the linear cam 60 at the second position in a monochrome mode in which monochrome printing is performed. Furthermore, the control unit 100 positions the linear cam 60 at the first position in a standby state in which printing is not performed.

[0046] The locking mechanism R includes a locking member R1 for locking the position of each photosensitive drum 51, a locking spring R2, and an interlocking member R3 for interlocking the locking member R1 with the linear cam 60. The locking member R1 is a plate-shaped member extending in the front-rear direction and is movable in the front-rear direction. The locking member R1 is movable between a locking position (position in FIG. 3) where the position of each photosensitive drum 51 is locked and an unlocking position (position in FIG. 4) where the lock on each photosensitive drum 51 is released.

[0047] The lock spring R2 is a spring that biases the lock member R1 from the unlocked position toward the locked position. The interlocking member R3 is a member that extends in the vertical direction and is rotatable around its center. When the linear cam 60 moves from the third position to the fourth position, the interlocking member R3 is pushed by the linear cam 60 and rotates clockwise as shown in the figure, thereby moving the lock member R1 from the locked position to the unlocked position against the biasing force of the lock spring R2.

[0048] The biasing force of the lock spring R2 is set to a level that prevents the translation cam 60 from moving rearward via the interlocking member R3. Therefore, as shown in Fig. 4, when the cover 20 is moved to the open position and then returned to the closed position, the translation cam 60 is maintained in the fourth position. Note that when the control unit 100 moves the translation cam 60 rearward with the cover 20 in the closed position and the translation cam 60 in the fourth position, the biasing force of the lock spring R2 moves the lock member R1 from the released position to the locked position.

[0049] The linear cam 60 contacts the upper end of the interlocking member R3 when it is located within the specific range shown in Figure 3 or 4, and moves away from the upper end of the interlocking member R3 when it is located outside the specific range shown in Figure 1 or 2. The lower end of the interlocking member R3 is always in contact with the front end of the locking member R1.

[0050] As shown in FIG. 5, the linear cam 60 has a detectable portion 61. The color printer 1 also has a sensor SE that detects the detectable portion 61. The detectable portion 61 has a first detectable portion 61A and a second detectable portion 61B that is spaced forward from the first detectable portion 61A. The sensor SE is, for example, an optical sensor that has a light-emitting portion and a light-receiving portion. The sensor SE is positioned so that light emitted from the light-emitting portion intersects with the movement trajectories of the first detectable portion 61A and the second detectable portion 61B.

[0051] The first detectable portion 61A and the second detectable portion 61B are disposed with a distance L1 between them in the front-rear direction. When the linear cam 60 is located at the first position, the sensor SE is disposed at a position spaced forward from the second detectable portion 61B. As a result, light from the light-emitting portion of the sensor SE passes through the space in front of the second detectable portion 61B and is received by the light-receiving portion. Furthermore, when the linear cam 60 is located at the first position, the center position of the sensor SE (position of the light) is disposed at a distance L2, which is larger than the distance L1, from the front end of the second detectable portion 61B.

[0052] When the translation cam 60 is in the second position, the sensor SE is located at the same position as part of the second detected portion 61B, so that the light from the sensor SE is blocked by the second detected portion 61B.

[0053] When the linear cam 60 is in the third position, the sensor SE is located between the first detectable portion 61A and the second detectable portion 61B. As a result, light from the light-emitting portion of the sensor SE passes through the space between the first detectable portion 61A and the second detectable portion 61B and is received by the light-receiving portion.

[0054] When the translation cam 60 is in the fourth position, the sensor SE is located at the same position as part of the first detected portion 61 A. As a result, the light from the sensor SE is blocked by the first detected portion 61 A.

[0055] When the control unit 100 knows the current position of the translation cam 60, it can move the translation cam 60 to the first position, the second position, or the third position based on the current position and a signal from the sensor SE. However, when the cover 20 is opened or closed, the position of the translation cam 60 changes depending on the amount of rotation of the cover 20. Therefore, the control unit 100 executes an initialization process shown in FIG. 6 to execute a cam position determination process that determines the position of the translation cam 60 immediately after the cover 20 is closed. The cam position determination process is a process performed in the first half of the initialization process, and more specifically, the process of steps S1 to S8 and S11 to S15, which will be described later. Furthermore, if the amount of rotation of the cover 20 is equal to or greater than a predetermined amount, there is a possibility that the user has touched the cartridge 50. Therefore, the control unit 100 executes an initialization drive process in the initialization process to drive the cartridge 50 for initialization.

[0056] The driving force may be supplied to the cartridge 50 by the motor MT or by a motor separate from the motor MT. When the driving force of the motor MT is supplied to the cartridge 50, it is preferable to provide a clutch between the motor MT and the linear cam 60, and between the motor MT and the cartridge 50.

[0057] The control unit 100 stops grasping the current position of the linear cam 60 when the cover 20 is opened or when the color printer 1 is turned off. When the color printer 1 is turned off, the control unit 100 stops operating and is unable to grasp the current position of the linear cam 60. Based on a signal from the cover sensor CS, which detects whether the cover 20 is closed, the control unit 100 stops grasping the current position of the linear cam 60 if the cover 20 is not closed. The control unit 100 executes an initialization process when the cover 20 is closed or when the color printer 1 is turned on and the control unit 100 is started up.

[0058] When the control unit 100 becomes able to grasp the current position of the linear cam 60 after having stopped grasping the current position of the linear cam 60, the control unit 100 executes the initialization process shown in FIG. In the initialization process, the control unit 100 first executes a cam position identification process (S1 to S8, S11 to S15). When the cam position identification process starts, the control unit 100 determines whether or not light from the sensor SE is transmitted, that is, whether or not the light receiving portion of the sensor SE is receiving light (S1).

[0059] Here, when the light receiving portion of the sensor SE receives light at the start of the cam position identification process, the control unit 100 determines that the translational cam 60 is located at a rear position (e.g., the first position) where the second detectable portion 61B is located behind the sensor SE as shown in FIG. 5(a) or at the third position shown in FIG. 5(c). Here, the rear position includes the first position as well as a position slightly shifted forward from the first position (a position where light is not blocked by the second detectable portion 61B). When the translational cam 60 is located at the rearmost first position at the start of the cam position identification process, the translational cam 60 cannot be moved rearward.

[0060] Therefore, if it is determined in step S1 that the light from the sensor SE is transmitted (Yes), the control unit 100 rotates the motor MT forward to move the linear cam 60 forward (S2). After step S2, the control unit 100 determines whether the light from the sensor SE is blocked, that is, whether the light receiving unit of the sensor SE is not receiving light (S3). The control unit 100 repeats the process of step S3 until the light from the sensor SE is blocked (S3: No).

[0061] 8(a) and 8(b), when the position of the translation cam 60 is the rear position at the start of the cam position identification process, the light of the sensor SE is blocked by the second detectable portion 61B due to the forward movement of the translation cam 60. Also, when the position of the translation cam 60 is the third position at the start of the cam position identification process, the light of the sensor SE is blocked by the first detectable portion 61A due to the forward movement of the translation cam 60, as shown in FIGS.

[0062] If it is determined in step S3 that the light from the sensor SE has been blocked (Yes), the control unit 100 stops the motor MT and then rotates it in the reverse direction (S4). After step S4, the control unit 100 determines whether the light from the sensor SE has been transmitted (S5). The control unit 100 repeats the process of step S5 until the light from the sensor SE has been transmitted (S5: No).

[0063] 8(b) and 8(c), when the position of the linear cam 60 is in the rear position at the start of the cam position identification process, the reverse rotation of the motor MT causes the linear cam 60 to move rearward, causing the second detectable portion 61B to move rearward out of the light of the sensor SE and allowing the light of the sensor SE to pass through. As shown in 9(b) and 9(c), when the position of the linear cam 60 is in the third position at the start of the cam position identification process, the reverse rotation of the motor MT causes the linear cam 60 to move rearward, causing the first detectable portion 61A to move rearward out of the light of the sensor SE and allowing the light of the sensor SE to pass through.

[0064] If it is determined in step S5 that the light from the sensor SE has been transmitted (Yes), the control unit 100 determines whether the light from the sensor SE has been blocked within a predetermined time after the light from the sensor SE has been transmitted (S6). As shown in FIG. 8(c), if the position of the linear cam 60 at the start of the cam position identification process is the rear position, after the second detectable portion 61B moves rearward out of the light from the sensor SE, the light from the sensor SE is not blocked within the predetermined time because the linear cam 60 does not have anything to block the light from the sensor SE. As shown in FIG. 9(c), if the position of the linear cam 60 at the start of the cam position identification process is the third position, after the first detectable portion 61A moves rearward out of the light from the sensor SE, the light from the sensor SE is blocked by the second detectable portion 61B within the predetermined time.

[0065] If it is determined in step S6 that the light from the sensor SE has been blocked within the predetermined time (Yes), the control unit 100 determines that the position of the linear cam 60 at the start of the cam position identification process is within the specific range, specifically the third position (S7).If it is determined in step S6 that the light from the sensor SE has not been blocked even after the predetermined time has elapsed (No), the control unit 100 determines that the position of the linear cam 60 at the start of the cam position identification process is outside the specific range, specifically the rear position (for example, the first position) (S8).

[0066] If the light from the sensor SE is blocked in step S1 (No), the linear cam 60 is positioned at a front light-blocking position (e.g., the second position) where the light from the sensor SE is blocked by the second detectable portion 61B as shown in FIG. 5(b) or a rear light-blocking position (e.g., the fourth position) where the light from the sensor SE is blocked by the first detectable portion 61A as shown in FIG. 5(d). Here, the front light-blocking position includes the second position as well as a position slightly shifted forward or backward from the second position (within the range of the second detectable portion 61B in the front-to-rear direction). The rear light-blocking position includes the fourth position as well as a position slightly shifted forward or backward from the fourth position (within the range of the first detectable portion 61A in the front-to-rear direction). If the linear cam 60 is positioned at the forward-most fourth position at the start of the cam position identification process, the linear cam 60 cannot be moved forward.

[0067] Therefore, if it is determined in step S1 that the light from the sensor SE is not transmitted (No), the control unit 100 causes the motor MT to rotate in the reverse direction (S11) to move the linear cam 60 backward. After step S11, the control unit 100 determines whether the light from the sensor SE is transmitted (S12). The control unit 100 repeats the process of step S12 until the light from the sensor SE is transmitted (S12: No).

[0068] 10(a) and 10(b), when the position of the linear cam 60 is the front light-shielding position at the start of the cam position identification process, the reverse rotation of the motor MT causes the linear cam 60 to move rearward, causing the second detectable portion 61B to move rearward out of the light of the sensor SE and allowing the light of the sensor SE to pass through. As shown in 11(a) and 11(b), when the position of the linear cam 60 is the rear light-shielding position at the start of the cam position identification process, the reverse rotation of the motor MT causes the linear cam 60 to move rearward, causing the first detectable portion 61A to move rearward out of the light of the sensor SE and allowing the light of the sensor SE to pass through.

[0069] If it is determined in step S12 that the light from the sensor SE has been transmitted (Yes), the control unit 100 determines whether the light from the sensor SE has been blocked within a predetermined time after the light from the sensor SE has been transmitted (S13). As shown in FIG. 10(b), if the position of the linear cam 60 at the start of the cam position identification process is the front light-blocking position, the light from the sensor SE will not be blocked within the predetermined time after the second detectable portion 61B moves rearward from the light from the sensor SE because the linear cam 60 does not have anything to block the light from the sensor SE. As shown in FIGS. 11(b) and 11(c), if the position of the linear cam 60 at the start of the cam position identification process is the rear light-blocking position, the light from the sensor SE will be blocked by the second detectable portion 61B within the predetermined time after the first detectable portion 61A moves rearward from the light from the sensor SE.

[0070] If it is determined in step S13 that the light from the sensor SE has been blocked within the predetermined time (Yes), the control unit 100 determines that the position of the linear cam 60 at the start of the cam position identification process is within the specific range, specifically the rear light-blocking position (e.g., the fourth position) (S14). If it is determined in step S13 that the light from the sensor SE has not been blocked even after the predetermined time has elapsed (No), the control unit 100 determines that the position of the linear cam 60 at the start of the cam position identification process is outside the specific range, specifically the front light-blocking position (e.g., the second position) (S15).

[0071] When it is determined that the position of the linear cam 60 at the start of the cam position identification process is within the specific range (S7 or S14), the control unit 100 moves the linear cam 60 to the third position (S21) and then executes the initialization drive process (S22), as shown in Fig. 7. After step S22, the control unit 100 moves the linear cam 60 to the first position (S23) and ends this process.

[0072] If it is determined that the position of the linear cam 60 at the start of the cam position identification process is outside the specified range (S8 or S15), the control unit 100 determines whether the previous initialization process was interrupted (S24). The control unit 100 determines that the initialization process was interrupted if the color printer 1 is turned off or the cover 20 is moved from the closed position before the previous initialization process is completed. If it is determined in step S24 that the previous initialization process was interrupted (Yes), the control unit 100 proceeds to the process of step S21. If it is determined in step S24 that the previous initialization process was not interrupted (No), the control unit 100 proceeds to the process of step S23.

[0073] The operation of the control unit 100 during the initialization process is briefly described below. The control unit 100 determines the rotation direction of the motor MT corresponding to the movement direction of the linear cam 60 based on the detection result of the sensor SE when the cam position identification process is started (S1, S2 or S11).

[0074] When the cam position identification process is started, the control unit 100 moves the linear cam 60 (S2, S4 or S11), and identifies the position of the linear cam 60 at the start of the cam position identification process based on a change in the signal of the sensor SE (S3, S5, S6 or S12, S13) (S7, S8 or S14, S15). Specifically, as shown in Fig. 8(d), if the sensor SE is in an ON state (a state in which light is transmitted) at the start of the cam position identification process and the signal of the sensor SE changes from OFF to ON as the linear cam 60 moves thereafter, the control unit 100 identifies the position of the linear cam 60 at the start of the cam position identification process as a rear position including the first position.

[0075] As shown in Fig. 9(e), if the sensor SE is ON at the start of the cam position identification process and the signal from the sensor SE changes from OFF to ON and then OFF as the linear cam 60 moves, the control unit 100 identifies the position of the linear cam 60 at the start of the cam position identification process as the third position. As shown in Fig. 10(c), if the sensor SE is OFF (light-shielded) at the start of the cam position identification process and the signal from the sensor SE changes to ON as the linear cam 60 moves, the control unit 100 identifies the position of the linear cam 60 at the start of the cam position identification process as the front light-shielded position, which includes the second position. As shown in Fig. 11(d), if the sensor SE is OFF at the start of the cam position identification process and the signal from the sensor SE changes from ON to OFF as the linear cam 60 moves, the control unit 100 identifies the position of the linear cam 60 at the start of the cam position identification process as the rear light-shielded position, which includes the fourth position.

[0076] The control unit 100 determines whether the identified position of the linear cam 60 is within a specific range (S7, S8 or S14, S15). If the control unit 100 determines that the identified position of the linear cam 60 is within the specific range, it executes an initialization drive process (S22). If the control unit 100 determines that the identified position of the linear cam 60 is not within the specific range, it does not execute the initialization drive process unless the previous initialization process has been interrupted (S24: No).

[0077] Next, an example of the operation of the control unit 100 will be described. If the cover 20 is opened by more than a predetermined amount during the time period from when the control unit 100 stops determining the current position of the translation cam 60 to when it becomes able to determine the current position of the translation cam 60, the position of the translation cam 60 at the start of the cam position identification process will be the third position or a rear light-blocking position including the fourth position. The control unit 100 moves the translation cam 60 based on the detection result of the sensor SE at the start of the cam position identification process, and by referring to the change in the signal from the sensor SE, identifies the position of the translation cam 60 at the start of the cam position identification process as the third position or the rear light-blocking position, and then executes the initialization drive process. Therefore, even if the cover 20 is opened by more than a predetermined amount and the user touches the cartridge 50, causing the cartridge 50 to be misaligned, the initialization drive process can correct the misalignment of the cartridge 50.

[0078] Furthermore, if the cover 20 is not opened by a predetermined amount or more during the time from when the control unit 100 stops determining the current position of the linear cam 60 until when it is able to determine the current position of the linear cam 60, the position of the linear cam 60 at the start of the cam position identification process will be the rear position (including the first position) or the front light-blocking position (including the second position). The control unit 100 moves the linear cam 60 based on the detection result of the sensor SE at the start of the cam position identification process, and by referring to the change in the sensor SE signal, determines that the position of the linear cam 60 at the start of the cam position identification process is the rear position or the rear light-blocking position. Unless the previous initialization process was interrupted, the initialization drive process will not be executed. Therefore, if the cover 20 is not opened by a predetermined amount or more, the initialization drive process will not be executed, allowing the subsequent printing process to be executed more quickly.

[0079] As described above, the following effects can be obtained in this embodiment. Even if the user touches the cartridge 50 with the cover 20 opened to a predetermined extent and the cartridge 50 is displaced, the control unit 100 determines that the linear cam 60 is within a specific range and executes an initialization drive process, thereby correcting the displacement of the cartridge 50.

[0080] Since the control unit 100 identifies the position of the linear cam 60 based on a change in the signal of the sensor SE, there is no need to provide a sensor for detecting the absolute position of the linear cam, for example, and an increase in costs can be suppressed.

[0081] When the linear cam 60 is located at the third or fourth position, the developing roller 53 comes into contact with the photosensitive drum 51, so that when the cover 20 is opened by a predetermined amount or more and the cartridge 50 is removed, the developing roller 53 can be brought into contact with the photosensitive drum 51.

[0082] The single linear cam 60 can displace each of the developing rollers 53 of the multiple cartridges 50 .

[0083] The present invention is not limited to the above-described embodiment, but can be used in various forms as exemplified below.

[0084] In the above embodiment, the position of the linear cam 60 at the start of the cam position identification process is identified based on a change in the signal from the sensor SE, but the present invention is not limited to this. For example, if the sensor is a sensor that can detect the absolute position of the linear cam, the control unit may identify the position of the linear cam at the start of the cam position identification process based on the signal from the sensor at the start of the cam position identification process.

[0085] In the above embodiment, the range from the third position to the fourth position is set as the specific range, but the present invention is not limited to this. For example, only the fourth position may be set as the specific range.

[0086] In the above embodiment, a color printer 1 is used as an example of an image forming apparatus, but the present invention is not limited to this, and the image forming apparatus may be, for example, a monochrome printer, a copier, a multifunction machine, or the like.

[0087] In the above embodiment, the photosensitive drum 51 is used as an example of the photosensitive member, but the present invention is not limited to this, and may be, for example, a belt-shaped photosensitive member.

[0088] The mechanism for linking the cover and the cam is not limited to the structure of the above embodiment, and the cover and the cam may be linked by transmitting force from the cover to the cam using a transmission mechanism having a gear or a clutch. Also, the cam may be a cam that is rotatable relative to the housing.

[0089] The sensor is not limited to an optical sensor, and may be, for example, a switch-type sensor that turns on when it comes into contact with a detected part and turns off when the detected part moves away.

[0090] The locking members that lock the multiple photosensitive drums are not limited to the structure described in the above embodiment. For example, multiple locking members that can rotate between a drum lock position that locks the photosensitive drum and an unlock position that unlocks the photosensitive drum may be provided for each photosensitive drum. In this case, a spring that biases the locking member from the unlock position to the drum lock position may be provided for each of the multiple locking members. In this case, a locking translation cam that can move in the forward / backward direction and that switches the positions of the multiple locking members may be linked to the aforementioned translation cam 60 via the linking member R3.

[0091] The elements described in the above-described embodiment and modified examples may be implemented in any combination. [Explanation of symbols]

[0092] 1 color printer 10. Cabinet 10A aperture 20 Cover 50 cartridges 51 Photosensitive drum 53 Developing roller 60 Linear Cam 61 Detected part 100 control section MT motor SE Sensor

Claims

1. a housing having an opening; a cover that moves between a closed position that closes the opening of the housing and an open position that opens the opening; a cartridge having a photosensitive member and a developing roller and being detachable from the housing through the opening; a cam that moves the developing roller between a contact position where the developing roller contacts the photosensitive member and a spaced position where the developing roller is spaced from the photosensitive member, the cam being moved in one direction by the cover when the cover moves in a direction from the closed position toward the open position, and not being moved by the cover when the cover moves in a direction from the open position toward the closed position, the cam being positioned in a specific range when the cover is opened by a predetermined amount or more; a motor for moving the cam; a sensor for detecting a detected portion provided on the cam, the sensor having a light emitting portion and a light receiving portion; a control unit, The detected part is A first detected part; a second detected portion spaced apart from the first detected portion in the one direction, light from the light-emitting portion of the sensor can be received by the light-receiving portion after passing between the first detectable portion and the second detectable portion, The control unit Executing a cam position identification process to identify the position of the cam based on the signal from the sensor; When it is determined that the position of the cam is within the specific range, an initialization drive process is executed to drive the cartridge for initialization; If it is determined that the position of the cam is not within the specific range, the initialization drive process is not executed, The cover is a first intermediate position between the closed position and the open position; a second intermediate position closer to the open position than the first intermediate position; The cam is The cover is movable from a first position to a second position when the cover moves from the closed position to the first intermediate position, When the cover moves from the first intermediate position to the second intermediate position, the cover is movable from the second position to the third position; When the cover moves from the second intermediate position to the open position, the cover is movable from the third position to the fourth position; The control unit When the cam position specifying process is started and the cam is located at the third position or the fourth position, the initialization drive process is executed; The image forming apparatus is characterized in that, if the cam is located at the first position or the second position when the cam position specifying process is started, the initialization drive process is not executed.

2. a cover sensor that detects whether the cover is in the closed position; The control unit 2. The image forming apparatus according to claim 1, wherein the cam position specifying process is executed when the cover is in the closed position based on a signal from the cover sensor.

3. 2. The image forming apparatus according to claim 1, wherein the control unit executes the cam position specifying process when the control unit is started.

4. The control unit In the cam position identification process, determining whether the light receiving unit of the sensor receives light; When it is determined that the light receiving unit receives light, the motor is rotated forward to move the cam in the one direction; Thereafter, when the light receiving unit no longer receives light, the motor is rotated in reverse to move the cam in a direction opposite to the one direction, Thereafter, when the light receiving unit receives light, it is determined whether or not the light receiving unit has become in a state where it is not receiving light within a predetermined time from when the light receiving unit receives light, If it is determined that the light receiving unit has not received light within the predetermined time, the position of the cam at the start of the cam position identification process is identified to be within the specific range; An image forming apparatus according to any one of claims 1 to 3, characterized in that if it is determined that the light receiving unit has not reached a state where it is not receiving light within the specified time, the position of the cam at the start of the cam position identification process is identified as being outside the specified range.

5. The control unit In the cam position identification process, determining whether the light receiving unit of the sensor receives light; When it is determined that the light receiving unit does not receive light, the motor is rotated in a reverse direction to move the cam in a direction opposite to the one direction; Thereafter, when the light receiving unit receives light, it is determined whether or not the light receiving unit has become in a state where it is not receiving light within a predetermined time from when the light receiving unit receives light, If it is determined that the light receiving unit has not received light within the predetermined time, the position of the cam at the start of the cam position identification process is identified to be within the specific range; The image forming apparatus according to claim 4, characterized in that if it is determined that the light receiving unit has not reached a state where it is not receiving light within the specified time, the position of the cam at the start of the cam position identification process is identified as being outside the specified range.

6. The control unit 6. The image forming apparatus according to claim 1, wherein in a standby state in which no printing is performed, the cam is positioned at the first position to separate the developing roller from the photosensitive member.

7. 7. The image forming apparatus according to claim 1, wherein the developing roller contacts the photosensitive member when the cam is located at the third position or the fourth position.

8. A plurality of the cartridges are provided, The cam is 8. The image forming apparatus according to claim 1, further comprising a linear cam extending in the direction of arrangement of the cartridges, the linear cam displacing the developing roller in each of the cartridges to the contact position or the separated position.

Images