Image forming device

Abstract

To make it possible to improve the quality of an image to be printed.SOLUTION: An image forming apparatus 1 makes a positioning projection 29 of an ID unit 16 move in a direction along a groove axis X42D inclined with respect to a conveyance direction U1 in a groove part 42D of a contact and separation guide 42. In performing color printing, when the image forming apparatus 1 brings down color ID units 16CMY, it performs ID stabilization processing to rotate IDs 26, causes a conveyance belt 15 to travel at a higher speed than that of peripheral side surfaces of the IDs, and applies a force going in a conveyance direction U1 to the color ID units 16CMY to cause them to reach transfer positions. Consequently, the image forming apparatus 1 can print a high-quality image in which color shift is greatly reduced.SELECTED DRAWING: Figure 14

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus, and is suitably applied to, for example, an electrophotographic printer. [Background technology]

[0002] In recent years, there have been image forming devices that print images by, for example, using an image forming unit to generate a toner image (also called a developer image) based on image data using toner (also called a developer image), transferring it to paper (also called a medium), and then fixing the image by applying heat and pressure to the paper using a fixing unit.

[0003] In this image forming unit, a toner image is formed on the peripheral surface of a cylindrically configured rotating image drum (also called an image carrier), and the toner image is transferred from the photosensitive drum to paper. This image drum gradually wears out due to friction with the various rollers in the image forming unit and with the paper, so it is replaced every time a replacement condition is met, such as when 30,000 sheets have been printed.

[0004] In addition, in an image forming device that supports color printing, image forming units of four colors, for example black, cyan, magenta, and yellow, are arranged along the paper transport path, and toner images of each color are transferred and fixed sequentially onto the paper, thereby printing a color image on the paper.

[0005] However, even if an image forming device is capable of such color printing, there are cases where monochrome printing is performed using only black toner, such as when printing a document consisting of only characters. In this case, if the image forming device rotates the image drums of colors other than black (hereinafter referred to as each color) even though a toner image is not being formed, there is a risk of wasting the image drums.

[0006] Therefore, an image forming device has been proposed that is provided with a mechanism for abutting or separating the image forming unit for each color from the paper transport path, and by separating the image forming unit for each color from the transport path during monochrome printing and abutting it against the transport path during color printing, thereby reducing unnecessary wear (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2020-52298 A (Figs. 8-16, etc.) Summary of the Invention [Problem to be solved by the invention]

[0008] However, in an image forming apparatus with such a configuration, when the image forming unit is brought into contact with the paper transport path, a sufficient force cannot be applied to the image forming unit, and the image forming unit may not reach the appropriate position. In such a case, the image forming apparatus has a problem that the quality of the image printed on the paper may be reduced.

[0009] SUMMARY OF THE PRESENT DISCLOSURE The present invention has been made in consideration of the above points, and aims to propose an image forming apparatus capable of improving the quality of printed images. [Means for solving the problem]

[0010] In order to solve the above problem, the image forming apparatus of the present invention includes a device housing having an internal space, an image forming unit provided inside the device housing and forming a developer image on a rotating image carrier using a developer, a transport unit that comes into contact with the image carrier and transports the medium in a transport direction, a contact and separation unit that changes the position of the image forming unit relative to the device housing between a separated position where the image carrier is separated from the medium and a close position where the image carrier is closer to the medium than the separated position, a contact and separation drive unit that drives the image forming unit to the separated position or the close position, a displacement regulating unit that regulates the image forming unit to a transfer position where the developer image is transferred from the image carrier to the medium when the image forming unit is displaced toward the device housing in the transport direction, and a control unit that controls operations of the image forming unit, the transport unit and the contact and separation drive unit, and the control unit A conveying operation by the conveying unit is started, and after a predetermined time has elapsed, a rotating operation of the image carrier by the image forming unit is started; A speed difference forming process is performed in which the image carrier speed, which is the linear speed of the image carrier, is made smaller than the medium speed, which is the linear speed of the medium by the transport unit. The image forming apparatus of the present invention includes a device housing having an internal space, an image forming unit provided inside the device housing and forming a developer image on a rotating image carrier by developer, a transport unit that contacts the image carrier and transports the medium in a transport direction, a contact and separation unit that changes the position of the image forming unit relative to the device housing between a separated position where the image carrier is separated from the medium and a close position where the image carrier is closer to the medium than the separated position, a contact and separation drive unit that drives the image forming unit to the separated position or the close position, and a contact and separation drive unit that changes the position of the image forming unit in the transport direction relative to the device housing. The control unit is provided with a displacement regulating unit which regulates the image carrier to a transfer position where the developer image is transferred from the image carrier to the medium when the image carrier is positioned close to the medium, and a control unit which controls the operations of the image forming unit, the conveying unit and the separation drive unit, and when the image forming unit is displaced to the close position by the separation drive unit, the control unit performs a speed difference forming process to make the image carrier speed, which is the linear speed of the image carrier, smaller than the medium speed, which is the linear speed of the medium by the conveying unit, and then stops the conveying operation by the conveying unit and the rotation operation of the image carrier by the image forming unit, and then performs a printing process to form the developer image on the medium.

[0011] In the present invention, when the image forming unit is displaced to a close position by the separation and attachment drive unit and then a speed difference formation process is performed, the medium speed is faster than the image carrier speed, so that the image carrier can be urged in the transport direction by the transport unit, and the displacement regulating unit regulates the range of displacement of the image forming unit to allow it to reach the transfer position, and the developer image can be transferred to an appropriate position on the medium. In this case, if the rotation speed of the image carrier in the image forming section rises faster than the transport speed in the transport section, and the image carrier speed temporarily becomes faster than the medium speed, there is a risk of the image carrier being displaced in a direction away from the transfer position. However, the present invention can prevent such a phenomenon from occurring because the rotation operation of the image carrier is started only after the medium speed has sufficiently increased when starting the speed difference formation process. Effect of the Invention

[0012] According to the present invention, it is possible to realize an image forming apparatus capable of improving the quality of printed images. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus. [Diagram 2] FIG. 2 is a schematic diagram illustrating a configuration of an image drum unit. [Diagram 3] FIG. 2 is a schematic perspective view showing an internal configuration of the image forming apparatus. [Figure 4]FIG. 2 is a schematic perspective view showing a configuration of a contact and separation unit. [Diagram 5] FIG. 4 is a schematic diagram showing a configuration of a contact and separation guide. [Figure 6] 5A and 5B are schematic diagrams illustrating a separate state and a close state of the color image drum unit. [Figure 7] 3 is a schematic diagram showing a configuration of a drum coupling portion. FIG. [Figure 8] FIG. 2 is a schematic perspective view showing a configuration of a coupling slide. [Figure 9] FIG. 2 is a schematic block diagram illustrating a circuit configuration of the image forming apparatus. [Figure 10] FIG. 4 is a schematic diagram illustrating a configuration of page information. [Figure 11] 13 is a flowchart showing a PU printing process procedure according to the first embodiment. [Figure 12] 5 is a flowchart showing an image drum up-down process procedure according to the first embodiment. [Figure 13] 10 is a flowchart showing a procedure of an image drum stabilization process. [Figure 14] 4 is a schematic diagram showing the speeds of an image drum and a conveyor belt. [Figure 15] 10 is a flowchart showing a power-on processing procedure according to the second embodiment. [Figure 16] 13 is a flowchart showing an initial processing procedure according to the second embodiment. [Figure 17] 13 is a flowchart showing a PU printing process procedure according to the second embodiment. [Figure 18] 10 is a flowchart showing an image drum up-down process procedure according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

[0015] 1. First embodiment [1-1. Configuration of image forming device] 1, the image forming apparatus 1 according to the first embodiment is an electrophotographic printer that can form (i.e., print) a monochrome or color image on a medium, such as paper P. Incidentally, the image forming apparatus 1 does not have an image scanner function for reading an original document or a communication function using a telephone line, and is a single-function SFP (Single Function Printer) that has only a printer function.

[0016] In the image forming apparatus 1, an internal space 2S is formed inside an apparatus housing 2 formed in a substantially box shape, and various parts are arranged in the internal space 2S. In addition, the apparatus housing 2 has an upper cover 2C that forms an upper part and is formed so as to be openable and closable. When the upper cover 2C is opened, the internal space 2S is communicated with the external space, so that the user can easily replace each part and perform various maintenance work. In addition, the apparatus housing 2 is provided with an upper cover sensor 2CS that detects the opening and closing of the upper cover 2C. Incidentally, in the following description, the left end part in FIG. 1 is the front of the image forming apparatus 1, and the up-down direction, the left-right direction, and the front-rear direction are defined when viewed from the front.

[0017] The image forming apparatus 1 is controlled overall by a control unit 3. This control unit 3 is connected to a higher-level device (not shown) such as a computer device by wire or wirelessly. When image data representing an image to be printed is provided from the higher-level device and printing of the image data is instructed, the control unit 3 executes a printing process for forming a print image on the surface of paper P.

[0018] A touch panel 4 is provided near the front of the top surface of the device housing 2. The touch panel 4 is, for example, a combination of a liquid crystal panel and a touch sensor, and displays various information under the control of the control unit 3, and also receives operational inputs from the user and notifies the control unit 3. A temperature and humidity sensor 5 is provided near the outside of the device housing 2. This temperature and humidity sensor 5 detects the surrounding temperature and humidity and notifies the control unit 3.

[0019] A paper feed tray 6 that stores paper P is provided at the bottom inside the device housing 2. A paper feed section 7 is provided above and in front of the paper feed tray 6. The paper feed section 7 has a paper feed roller 8, a conveying roller 9, a paper feed sensor 10, a registration roller 11, and the like arranged in this order along a conveying path U, and also has a conveying guide (not shown) and the like arranged along the conveying path U.

[0020] The paper feed roller 8, the transport roller 9, and the registration roller 11 are all cylindrical with their central axes aligned in the left-right direction, and rotate appropriately when driven by a paper feed motor (not shown). The supply of driving force to the paper feed roller 8 and the registration roller 11 is controlled by a paper feed roller clutch and a registration roller clutch (described later). The paper feed sensor 10 is a so-called optical sensor, and is disposed so that detection light traveling from a light-emitting portion to a light-receiving portion intersects with the transport path U, and supplies the detection result by the light-receiving portion to the control portion 3.

[0021] When the paper feed unit 7 receives a driving force from the paper feed motor, it rotates the paper feed roller 8 as appropriate to separate and send out one of the multiple sheets of paper P stored in the paper feed tray 6. Next, the paper feed unit 7 sends out the paper P upwards using the transport roller 9, and causes it to proceed along the transport path U. When the paper feed unit 7 detects the paper P using the paper feed sensor 10, it accordingly rotates the registration rollers 11 as appropriate, corrects any skew in the paper P, and sends it out backwards.

[0022] A writing sensor 12 is provided on the rear side along the conveying path U in the paper feed unit 7 to detect the conveying state, size, etc. of the paper P. The writing sensor 12 is an optical sensor similar to the paper feed sensor 10, and supplies the detection result to the control unit 3.

[0023] Behind the writing sensor 12, the conveying path U is inclined so as to rise slightly toward the rear when viewed from the left and right direction, and the intermediate conveying section 13 is disposed below the conveying path U. The inclination angle of the conveying path U with respect to the horizontal direction is about 10°. The intermediate conveying section 13 is configured such that a conveying belt 15 made of a circular belt is stretched around a front roller 14F disposed on the front side and a rear roller 14R disposed on the rear side.

[0024] When a driving force is transmitted from a belt motor (described later) to the rear roller 14R, the intermediate conveying section 13 as a conveying section rotates the rear roller 14R in the direction of arrow R1, and causes the conveying belt 15 to move accordingly. At this time, the conveying belt 15 moves along a circular traveling path that goes around the front roller 14F and the rear roller 14R, and causes the upper part along the conveying path U, i.e., the part stretched between the front roller 14F and the rear roller 14R, to move in a rear-upward direction. Hereinafter, this direction is also referred to as a conveying direction U1. At this time, when the paper P is delivered from the paper feed section 7, the intermediate conveying section 13 applies a force toward the conveying direction U1 to the paper P with the paper P placed on the upper side of the conveying belt 15, and causes the paper P to move in a rear-upward direction, i.e., in the conveying direction U1, as the conveying belt 15 moves.

[0025] Four image drum (ID) units 16K, 16C, 16M, and 16Y are arranged in this order from the front to the rear above the intermediate conveying section 13, across the conveying path U. The ID units 16K, 16C, 16M, and 16Y (hereinafter collectively referred to as image drum (ID) units 16) correspond to the colors black (K), cyan (C), magenta (M), and yellow (Y), respectively, but the only difference is the color, and all of them are configured similarly.

[0026] 2A, the ID unit 16 as an image forming section is configured such that a toner container 21, a supply roller 22, a developing roller 23, a developing blade 24, a charging roller 25, and an image drum 26 (hereinafter also referred to as ID 26) are provided inside an image drum (ID) housing 20. A transfer roller 27 is provided below the ID 26, i.e., on the opposite side of the conveyor belt 15.

[0027] The ID housing 20 is generally formed in a rectangular parallelepiped shape that is long in the left-right direction, and although most of the outer periphery is covered, a part of the upper side and a part of the lower side are open. The toner storage unit 21 serving as a developer storage unit forms a space therein for storing toner, and stores the toner as developer in the space. A toner remaining amount sensor 21S is provided inside the toner storage unit 21. The toner remaining amount sensor 21S serving as a remaining amount detection unit detects whether the remaining amount of toner stored in the toner storage unit 21 falls below a predetermined reference value and notifies the control unit 3.

[0028] The supply roller 22, the developing roller 23, the charging roller 25, the ID 26, and the transfer roller 27 are all configured as cylinders with their central axes aligned in the left-right direction, and are supported so as to be rotatable about the central axes. The developing blade 24 is configured as a thin plate that is long in the left-right direction, and the vicinity of the rear lower end is brought into contact with the peripheral side surface of the developing roller 23. The ID 26, which serves as an image carrier, is adapted to be charged by a charging layer provided on the outer periphery. Furthermore, a predetermined voltage is applied to the developing roller 23, the developing blade 24, the charging roller 25, and the transfer roller 27, respectively.

[0029] An LED (Light Emitting Diode) head 28 is provided above the ID 26. The LED head 28 has many light-emitting elements made of LEDs arranged in the left-right direction, which is the main scanning direction, and each light-emitting element is appropriately caused to emit light under the control of the control unit 3. Incidentally, a space is formed near the rear of the upper side of the ID housing 20 to allow the LED head 28 to be positioned directly above the ID 26.

[0030] As shown in FIG. 2B, the ID housing 20 has a developing roller connecting portion 24J and an image drum (ID) connecting portion 26J exposed on its right side for receiving a driving force from the device housing 2. A generally flat lower flat portion 20B is formed in the center of the lower surface near the right end of the ID housing 20, and a lower inclined portion 20S is formed on the front side of the lower flat portion 20B. The lower inclined portion 20S is inclined so as to rise toward the rear with respect to the lower flat portion 20B. Incidentally, the lower flat portion 20B and the lower inclined portion 20S are formed near the left end (not shown) of the ID housing 20, almost symmetrically with the lower flat portion 20B and the lower inclined portion 20S near the right end. Furthermore, a cylindrical positioning protrusion 29 is provided on the front side of the lower flat portion 20B of the ID housing 20.

[0031] The ID unit 16 is also configured to be detachable from the device housing 2. Specifically, when the upper cover 2C of the device housing 2 is opened and the internal space 2S is connected to the external space, the ID unit 16 can be taken out from the internal space 2S by a user, and can be inserted into the internal space 2S from the outside and attached. At this time, the ID unit 16 is positioned at a predetermined position in the internal space 2S using a positioning protrusion 29 (described in detail later). When the upper cover 2C is closed, the ID unit 16 is urged generally downward by an image drum (ID) unit spring 2G provided on the lower side of the upper cover 2C, thereby bringing the vicinity of the lower end of the ID 26 into contact with the conveyor belt 15.

[0032] This ID unit 16 (FIG. 2(A)) rotates each roller appropriately by being supplied with driving force from an image drum motor described later. This causes the supply roller 22 to supply toner in the toner storage section 21 to the development roller 23. The development roller 23 adheres the toner supplied from the supply roller 22 to its circumferential side surface. The development blade 24 scrapes off unnecessary toner from the surface of the development roller 23, thereby forming a toner layer of a predetermined thickness on the surface of the development roller 23. In addition, the charging roller 25 uniformly charges the surface of the image drum 26.

[0033] The LED head 28 emits light in a light emission pattern based on image data supplied from the control unit 3 (FIG. 1), sequentially exposing the peripheral side of the ID 26. This causes the ID 26 to form an electrostatic latent image on the peripheral side in response to the irradiated light. Next, the ID unit 16 forms a toner image (hereinafter also referred to as a developer image) in response to the electrostatic latent image by adhering toner (developer) to the peripheral side of the ID 26, and the rotation of the ID 26 causes the part on which the toner image is formed to reach the vicinity of the bottom end.

[0034] When paper P is being transported along the transport path U by the transport belt 15, the ID unit 16 (FIG. 1) pinches the transport belt 15 and the paper P between the ID 26 and the transfer roller 27, and transfers the toner image from the peripheral side surface of the ID 26 to the paper P. In this way, each ID unit 16 sequentially transfers and overlaps the toner images of the respective colors onto the paper P transported from the front along the transport path U, while moving the paper P diagonally upward and rearward.

[0035] The fixing unit 17 is provided near the rear end of the intermediate conveying unit 13. Fixing rollers 17A and 17B are rotatably provided in the fixing unit 17 on the upper and lower sides of the conveying path U. Fixing roller 17A also has a fixing heater 17H built in. When a driving force is supplied from a fixing motor described later, fixing unit 17 rotates fixing roller 17A in the direction of arrow R2 and fixes fixing roller 17B in the direction of arrow R1, and heats fixing heater 17H in fixing roller 17A under the control of control unit 3. As a result, fixing unit 17 applies heat and pressure to paper P conveyed along conveying path U, fixes a toner image on paper P, and then advances the paper P diagonally upward toward the rear.

[0036] A paper discharge section 18 is disposed above and rearward of the fixing section 17. The paper discharge section 18 has a transport guide and a plurality of transport rollers similar to those of the paper feed section 7, and also has a paper discharge sensor 19 that detects the paper P. The paper discharge sensor 19 is an optical sensor similar to the paper feed sensor 10, and supplies the detection result to the control section 3. By appropriately rotating each transport roller under the control of the control section 3, the paper discharge section 18 transports the paper P delivered from the fixing section 17 upward and rearward, then turns it back toward the front, and discharges it onto a discharge tray 2T formed on the top surface of the device housing 2.

[0037] [1-2. Configuration of the image drum unit and its surrounding parts] Next, a description will be given of the configuration of the peripheral parts of the ID unit 16. As shown in the schematic perspective view of Fig. 3, inside the device housing 2 of the image forming device 1, there are provided a left frame 31 located on the left side, a right frame 32 located on the right side, and a central frame 33 connecting the two, and various parts are attached to each frame.

[0038] The left frame 31 is formed as a rectangular parallelepiped that is thin in the left-right direction as a whole by, for example, cutting a predetermined steel plate into a predetermined shape and appropriately bending it. This left frame 31 is located on the left side of the paper feed tray 6, the intermediate transport section 13, the ID unit 16, the fixing section 17, etc. inside the device housing 2 (FIG. 1).

[0039] The right frame 32 is configured generally symmetrically with the left frame 31, and is formed as a rectangular parallelepiped that is thin in the left-right direction as a whole by, for example, cutting a specified steel plate into a specified shape and bending it appropriately. This right frame 32 is located on the right side of the paper feed tray 6, the intermediate transport unit 13, the ID unit 16, the fixing unit 17, etc. inside the device housing 2 (FIG. 1).

[0040] The central frame 33 is formed as a thin plate generally in the vertical direction, inclined so that the rear side is higher than the front side, and curved so that the vicinity of the rear end rises upward. The central frame 33 is provided at a position corresponding to the lower or rear side of the intermediate conveying section 13 and the fixing section 17 (FIG. 1), etc.

[0041] A right cover 34 is provided at a position slightly upward in the up-down direction on the right frame 32 and near the center in the front-rear direction, that is, at a position corresponding to the right side of the ID unit 16 inside the device housing 2 (FIG. 1). The right cover 34 is formed in a plate shape that is thin in the left-right direction. This right cover 34 has round holes penetrating in the left-right direction at eight positions in total, two at each position corresponding to each ID unit 16.

[0042] Further, a plurality of motors, such as a belt motor 35, an image drum (ID) motor 36, a paper feed motor 37, and a fixing motor 38, are attached to the left frame 31 and the right frame 32. The belt motor 35 is a stepping motor, which is provided on the left side (i.e., the outside) of the left frame 31 toward the lower rear, and supplies driving force to the rear roller 14R (FIG. 1) of the intermediate conveying section 13. The ID motor 36, which serves as an image forming driving section, is a DC (Direct Current) motor, which is provided on the right side (i.e., the outside) of the right frame 32 toward the upper front, and supplies driving force to each ID unit 16 (FIGS. 1 and 2).

[0043] The paper feed motor 37 is provided on the right side (i.e., the outside) of the right frame 32, toward the lower front, and supplies driving force to the paper feed rollers 8 of the paper feed unit 7 (FIG. 1) and the like. The fixing motor 38, which serves as a contact / separation driving unit, is provided on the right side (i.e., the outside) of the right frame 32, toward the lower rear, and supplies driving force to the fixing rollers 17A and 17B of the fixing unit 17 (FIG. 1) and the like.

[0044] The right frame 32 is provided with a right contact portion 40R near the lower left side of the right cover 34, and a drum coupling portion 50D and a development coupling portion 50E are provided on the right side (i.e., the outside) of the right cover 34. The left frame 31 is further provided with a left contact portion 40L at a position corresponding to the right contact portion 40R. Hereinafter, the right contact portion 40R and the left contact portion 40L are collectively referred to as contact portions 40, and the drum coupling portion 50D and the development coupling portion 50E are collectively referred to as coupling portions 50.

[0045] Incidentally, the image forming apparatus 1 is capable of performing both monochrome printing using only black (K) and color printing using each color. When performing monochrome printing, the image forming apparatus 1 does not use the ID units 16 for colors other than black (K), i.e., cyan (C), magenta (M) and yellow (Y) (hereinafter, these will be referred to as color image drum (ID) units 16CMY), but only uses the black ID unit 16K.

[0046] Therefore, in the image forming apparatus 1, the position of the color ID unit 16CMY with respect to the conveyor belt 15 is changed by the contact / disconnect unit 40, and the supply of driving force to the color ID unit 16CMY is switched by the coupling unit 50. Below, the configuration and operation of the right contact / disconnect unit 40R of the contact / disconnect unit 40 and the configuration and operation of the drum coupling unit 50D of the coupling unit 50 will be described.

[0047] [1-2-1. Configuration and operation of the connection / disconnection unit]

[0048] As shown in Fig. 4, the right contact / separation part 40R has a slide guide 41, a contact / separation guide 42 (Fig. 3), a lift-up slide 43, a first lift gear 44, a second lift gear 45, an image drum (ID) up-down clutch 46, and an image drum (ID) up-down sensor 48. Incidentally, in Figs. 4 and 5, some of the teeth of each gear are omitted, and the outer shape of each is shown by a simplified shape.

[0049] The slide guide 41 is generally configured in a long and narrow rectangular or rod-like shape, and is attached to the left side surface (i.e., the inner surface) of the right frame 32 (Fig. 4). Although this slide guide is disposed roughly along the front-rear direction, it is disposed in a direction along the transport path U in the vicinity of the ID unit 16 (Fig. 1), i.e., parallel to the transport direction U1, and is inclined so that the rear side is higher than the front side. The upper surface of the slide guide 41 is formed in a flat plane. Furthermore, a portion of the slide guide 41 is omitted near the rear.

[0050] The contact guide 42 (FIG. 3) is configured as a plate-like shape that is long in the front-rear direction and thin in the left-right direction as a whole, and is provided on the right side (outside) of the slide guide 41. As shown in FIG. 5(A), which is a partially enlarged right side view, the contact guide 42 is provided with two protrusions 42A and 42B that are slightly spaced apart in the front-rear direction at four locations corresponding to each ID unit 16. Both protrusions 42A and 42B protrude diagonally upward and forward, and a groove 42D is formed between them. The groove 42D is formed in an arc shape near the bottom end and in a straight line shape at its upper portion. The groove width of the groove 42D is slightly larger than the diameter of the positioning protrusion 29 (FIG. 3) of the ID unit 16.

[0051] As shown in FIG. 5B, which is a further enlarged view of a portion of FIG. 5A, the groove 42D is formed in a straight line inclined along an oblique direction connecting the upper front side and the lower rear side. The groove axis XD, which is a virtual center line of the groove 42D, has an inclination angle αV of about 25° with respect to a virtual vertical axis XV along the vertical direction, and accordingly, an inclination angle βH of about 65° with respect to a virtual horizontal axis XH along the horizontal direction. In the image forming apparatus 1, the virtual conveying axis XU along the conveying direction U1 is inclined by about 10° with respect to the horizontal axis XH. Therefore, the groove axis XD has an inclination angle βU of about 75° with respect to the conveying axis XU, and an inclination angle αN of about 15° with respect to a conveying normal XN, which is a virtual normal to the conveying axis XU.

[0052] The lift-up slide 43 (FIGS. 3 and 4) is configured as a rectangular parallelepiped or rod-like shape that is long in the front-rear direction as a whole, and is placed on the upper side of the slide guide 41. A rack gear 43G is formed facing downward in a portion of the lower surface of the lift-up slide 43 near the rear where the slide guide 41 is omitted. Therefore, when a force in the forward or rearward direction is applied to the rack gear 43G, the lift-up slide 43 can move, i.e., slide, along the upper surface of the slide guide 41, i.e., in the conveying direction U1 or the opposite direction. For convenience of explanation, the direction opposite to the conveying direction U1 will be referred to as the counter-conveying direction U2 below.

[0053] Furthermore, upwardly protruding portions 43P are formed at three locations corresponding to the ID units 16C, 16M, and 16Y (i.e., the color ID unit 16CMY) on the upper surface of the lift-up slide 43. Each protruding portion 43P has a nearby portion 43A near the front where the amount of upward protrusion is relatively small, an inclined portion 43B that is inclined so that the amount of upward protrusion increases toward the rear, and a distant portion 43C near the rear where the amount of upward protrusion is relatively large.

[0054] Furthermore, the three protrusions 43P of the lift-up slide 43 are positioned and abutted against the lower flat portions 20B of the ID units 16C, 16M, and 16Y, respectively. In other words, the protrusions 43P of the lift-up slide 43 support the loads of the ID units 16C, 16M, and 16Y via the lower flat portions 20B, respectively.

[0055] The first lift gear 44 is a disk-shaped gear having a plurality of teeth on its circumferential portion, and is rotatably supported by the right frame 32. The first lift gear 44 is located directly below the rack gear 43G of the lift-up slide 43, and is engaged with the rack gear 43G. The second lift gear 45, like the first lift gear 44, is a spur gear having a plurality of teeth on its circumferential portion, and is rotatably supported by the right frame 32. The second lift gear 45 is located diagonally below and in front of the first lift gear 44, and is engaged with the first lift gear 44.

[0056] The ID up-down clutch 46 has two gears arranged so as to overlap in the left-right direction, and a clutch mechanism is provided between the two gears. One gear of the ID up-down clutch 46 meshes with the second lift gear 45, and the other gear meshes with a predetermined relay gear (not shown), and the driving force from the fixing motor 38 (FIG. 3) is transmitted to the ID up-down clutch 46. Based on the control of the control unit 3, the ID up-down clutch 46 can switch between a transmission state in which the driving force is transmitted between the two gears and a non-transmission state in which the driving force is not transmitted.

[0057] On the other hand, the left contact / separation part 40L (FIG. 3) is configured so that each part is substantially symmetrical with respect to the right contact / separation part 40R (FIG. 4) except for the ID up-down clutch 46. Also, the second lift gear 45 of the left contact / separation part 40L is connected to the second lift gear 45 of the right contact / separation part 40R by a connecting shaft 47. Therefore, when the second lift gear 45 of the right contact / separation part 40R rotates, the left contact / separation part 40L can rotate the second lift gear 45 of the left contact / separation part 40L integrally therewith.

[0058] With this configuration, when the right contact section 40R drives the fixing motor 38 and switches the ID up-down clutch 46 to a transmission state under the control of the control section 3, the right contact section 40R transmits the driving force from the fixing motor 38 to the ID up-down clutch 46, the second lift gear 45, and the first lift gear 44 in that order. The right contact section 40R then transmits the driving force from the first lift gear 44 to the rack gear 43G, and moves the lift-up slide 43 together with the rack gear 43G in the transport direction U1 or the counter-transport direction U2. At this time, the left contact section 40L transmits the driving force from the right contact section 40R to the second lift gear 45 via the connecting shaft 47, and thus moves the lift-up slide 43 in the transport direction U1 or the counter-transport direction U2 in the same manner as the right contact section 40R.

[0059] When the lift-up slide 43 moves toward the transport direction U1, the proximal portion 43A of the protruding portion 43P is positioned directly below the lower flat portion 20B. At this time, as shown in FIG. 6A, the lift-up slide 43 positions the color ID unit 16CMY relatively lower and brings the vicinity of the lower end of the image drum 26 (FIG. 2) close to the transport belt 15. At this time, the positioning protrusion 29 (FIGS. 2 and 4) of the color ID unit 16CMY is positioned at the lowest end in the groove 42D of the contact guide 42 (FIG. 5). Hereinafter, this state is called the proximity state, the position of the color ID unit 16CMY at this time is called the transfer position, and the position of the positioning protrusion 29 at this time is called the protrusion transfer position Q1. That is, the groove 42D restricts the range in which the positioning protrusion 29 can be displaced with respect to the transport direction U1, and the position of the color ID unit 16CMY when the positioning protrusion 29 is displaced most toward the transport direction U1 is set as the transfer position. In the following description, the positioning protrusion 29 and the groove portion 42D are collectively referred to as a displacement restriction portion 49.

[0060] On the other hand, when the lift-up slide 43 is moved from the close state to the opposite conveying direction U2, the inclined portion 43B abuts against the lower flat portion 20B and the lower inclined portion 20S of the color ID unit 16CMY, and gradually lifts the color ID unit 16CMY. At this time, the color ID unit 16CMY moves the positioning protrusion 29 in the groove portion 42D obliquely upward and forward along the groove axis XD.

[0061] Eventually, the lift-up slide 43 positions the separation portion 43C of the protrusion 43P directly below the lower flat portion 20B and abuts it. At this time, as shown in Fig. 6(B), the lift-up slide 43 positions the color ID unit 16CMY relatively higher and separates the vicinity of the lower end of the ID 26 (Fig. 2) from the conveyor belt 15. Hereinafter, this state is referred to as the separated state, and the position of the color ID unit 16CMY at this time is referred to as the separated position or non-transfer position.

[0062] When the lift-up slide 43 is moved from the separated state toward the transport direction U1, the ID unit 16 is gradually lowered while the inclined portion 43B abuts against the lower flat portion 20B and the lower inclined portion 20S of the ID unit 16. At this time, the color ID unit 16CMY moves the positioning protrusion 29 in the groove portion 42D obliquely downward and rearward along the groove axis XD, and eventually reaches the close state (FIG. 6(A)).

[0063] The ID up-down sensor 48 (FIG. 4) is a so-called optical sensor that has a light-emitting portion that emits detection light and a light-receiving portion that receives the detection light, and generates a detection signal based on the light-receiving result by the light-receiving portion and notifies the control unit 3. The ID up-down sensor 48 is attached at a position where a part of it blocks the detection light when the lift-up slide 43 moves to the furthest side in the transport direction U1, that is, when the ID units 16 are in a close proximity state. Therefore, the control unit 3 can recognize whether the ID units 16 are in a close proximity state based on the detection signal obtained from the ID up-down sensor 48.

[0064] In this way, in the separation section 40, the lift-up slide 43 is moved in the conveying direction U1 or the counter-conveying direction U2 based on the driving force from the fixing motor 38, thereby switching the color ID unit 16CMY between a close state (Figure 6(A)) or a separated state (Figure 6(B)).

[0065] Incidentally, in the image forming device 1, when performing monochrome printing in which only a black (K) toner image is transferred to the paper P, wear of the ID26 in the color ID unit 16CMY is reduced by switching the color ID unit 16CMY to a separated state (Figure 6(B)).

[0066] Incidentally, in the contact section 40, when the color ID unit 16CMY is in the close state, as described above, a downward force acts due to the biasing force of the ID unit spring 2G (FIG. 1) and the weight of each ID unit 16. For this reason, in the contact section 40, when switching the color ID unit 16CMY from the close state to the separated state, it is necessary to use the driving force from the fixing motor 38 to apply a force greater than the biasing force of the ID unit spring 2G and the weight of each ID unit 16 in the upward direction.

[0067] At this time, in the contact / separation section 40, there is a restriction on the magnitude of the driving force supplied from the fixing motor 38 because the fixing motor 38 is originally a motor for driving the fixing section 17. Therefore, in the image forming apparatus 1, the biasing force of the ID unit spring 2G is kept relatively small so that the driving force supplied from the fixing motor 38 can be used to switch the color ID unit 16CMY from the close state to the separated state.

[0068] However, in the contact section 40, because the biasing force of the ID unit spring 2G is relatively small, when the color ID unit 16CMY is switched from the separated state to the adjacent state, the force biasing the color ID unit 16CMY downward may be insufficient. Specifically, in the contact section 40, as shown in Fig. 5(B), when the color ID unit 16CMY is switched to the adjacent state, the positioning protrusion 29 should reach the protrusion transfer position Q1 shown by the solid line in the figure, but due to the influence of friction of each part, etc., there is a possibility that it will stop at the protrusion intermediate position Q2, which is slightly above the protrusion transfer position Q1.

[0069] When the positioning protrusion 29 is located at the protrusion intermediate position Q2 in this way, the color ID unit 16CMY stops at an intermediate position diagonally above and forward of the transfer position, as shown in FIG. 6C, and is located slightly toward the opposite transport direction U2 side from the transfer position. In addition, at this time, the color ID unit 16CMY is likely to have a different amount of deviation from the transfer position for each color, rather than a constant amount. For this reason, when the color ID unit 16CMY at the intermediate position transfers a toner image onto the paper P transported along the transport path U, the position where the toner image is transferred may be slightly shifted toward the opposite transport direction U2 side from the correct position on the paper P, which may cause a misalignment with the toner images of other colors, i.e., a so-called color shift.

[0070] Thus, in the image forming apparatus 1, the color ID unit 16CMY may be in a proximity state but may remain at an intermediate position slightly shifted from the transfer position due to the separation and attachment unit 40. Therefore, in the image forming apparatus 1, an image drum (ID) stabilization process (described in detail later) is executed as a process for making the color ID unit 16CMY reach the transfer position as necessary. For convenience of explanation, the transfer position and the intermediate position where the color ID unit 16CMY may be located in the proximity state are hereinafter collectively referred to as the proximity position.

[0071] Furthermore, in the image forming apparatus 1, an "image drum (ID) stabilization request" can be set in a predetermined storage area provided in the control unit 3 as information indicating that this ID stabilization process should be executed. This ID stabilization request is set, for example, when the image forming apparatus 1 is powered on, that is, when there is a possibility that the color ID unit 16CMY has been attached or detached by the user.

[0072] [1-2-2. Configuration and operation of the coupling section] Next, the configuration of the coupling portion 50 (drum coupling portion 50D and development coupling portion 50E) will be described using the drum coupling portion 50D as an example. As shown in a schematic plan view in Fig. 7(A), the drum coupling portion 50D as a transmission switching portion has a drum drive coupler 51, a spring 52, a coupling slide 53, an image drum (ID) coupling clutch 54, and an image drum (ID) coupling sensor 55. Incidentally, Fig. 7(A) mainly shows the portion related to the ID unit 16C, and omits some gears and portions related to the ID units 16M and 16Y.

[0073] The drum driving coupler 51 is located to the right of the ID connection part 26J (FIG. 2(B)) of the ID unit 16C in the close state (FIG. 6(A)). The drum driving coupler 51 is formed in a cylindrical shape with its central axis aligned in the left-right direction as a whole, and is composed of a coupler root part 51A on the right side and a coupler tip part 51B on the left side.

[0074] The coupler base portion 51A is a relatively thick cylinder with a gear (not shown) formed on its peripheral side. The coupler tip portion 51B is a cylinder thinner than the coupler base portion 51A with a fitting portion formed at its tip portion (i.e., the left end portion) that can fit with the ID connection portion 26J of the ID unit 16C. The drum drive coupler 51 is restricted in its movement in the up-down and front-rear directions by the right frame 32 and the right cover 34 (Fig. 3) and the like, while being supported so that it can move in the left-right direction with its central axis generally aligned in the left-right direction and can rotate freely. The drum drive coupler 51 is rotated by the driving force transmitted from the ID motor 36 (Fig. 3) via a transmission gear and the like (not shown).

[0075] The spring 52 is a coil spring with its central axis aligned in the left-right direction, with its right end fixed to the right frame 32 via a predetermined support member and its left end abutted against the right side surface of the drum drive coupler 51 and compressed from its natural state. Therefore, the spring 52 urges the drum drive coupler 51 leftward by the action of its restoring force.

[0076] The coupling slide 53 is disposed adjacent to the right side of the right cover 34, and has a main body 53M, a hole 53H, and a protrusion 53P, as shown in the schematic perspective view of Fig. 8. The main body 53M is configured as a thin plate in the left-right direction, and is supported so as to be movable (slidable) generally in the front-rear direction, specifically in the conveying direction U1 or the counter-conveying direction U2, while its movement in the up-down and left-right directions is restricted by a predetermined support member (not shown) provided on the right cover 34.

[0077] The hole 53H penetrates the main body 53M in the left-right direction at a position communicating with a hole formed in the right cover 34 (FIG. 3), and is an elongated hole that is longer in the front-rear direction than in the up-down direction. The length of the short axis of the hole 53H, i.e., the length in the up-down direction, is larger than the diameter of the coupler tip 51B of the drum drive coupler 51 (FIG. 7) and smaller than the diameter of the coupler base 51A. The hole 53H is provided.

[0078] The protruding portion 53P protrudes rightward from the right side surface of the main body portion 53M, and is provided in a range excluding the vicinity of the front end (hereinafter referred to as the connecting portion 53A) around the hole portion 53H. The rear half of the protruding portion 53P (hereinafter referred to as the cutting portion 53C) has a right side surface that is formed almost flat, and the amount of protrusion to the right from the main body portion 53M is equal to or greater than the length along the left-right direction of the coupler tip portion 51B of the drum driving coupler 51. The front half of the protruding portion 53P (hereinafter referred to as the inclined portion 53B) has an inclined surface that connects the connecting portion 53A and the right side surface of the cutting portion 53C. That is, the shape of the coupling slide 53 when viewed from above (FIG. 7(A)) is similar to the shape of the lift-up slide 43 (FIG. 4) of the right contact portion 40R when viewed from the left side.

[0079] With this configuration, as shown in Figure 7 (A), when the coupler tip portion 51B of the drum drive coupler 51 is inserted into the hole portion 53H, the left side surface of the coupler root portion 51A can be abutted against the connection portion 53A, the inclined portion 53B or the cutting portion 53C.

[0080] The ID coupling clutch 54 is configured similarly to the ID up-down clutch 46 (FIG. 4) of the contact unit 40, and has two gears arranged so as to overlap in the left-right direction, with a clutch mechanism provided between the two gears. One gear of the ID coupling clutch 54 meshes with each drum drive coupler 51 via a predetermined relay gear group (not shown), and the driving force is transmitted from the paper feed motor 37 (FIG. 3) to the other gear. Similarly to the ID up-down clutch 46, the ID coupling clutch 54 can be switched between a transmission state in which the driving force is transmitted between the two gears and a non-transmission state in which the driving force is not transmitted, based on the control of the control unit 3.

[0081] With this configuration, when the drum coupling unit 50D drives the paper feed motor 37 and switches the ID coupling clutch 54 to a transmission state under the control of the control unit 3, the drum coupling unit 50D transmits the driving force from the paper feed motor 37 to the coupling slide 53 via the ID up-down clutch 46. As a result, the coupling slide 53 moves in the transport direction U1 or the counter-transport direction U2.

[0082] 7(A), when the coupling slide 53 is moved toward the opposite conveying direction U2, the left side surface of the coupler root portion 51A comes into contact with the connection portion 53A. At this time, the drum drive coupler 51 makes the tip of the coupler tip portion 51B protrude sufficiently to the left beyond the right cover 34 and is engaged (i.e., connected) with the ID connection portion 26J of the ID unit 16C, and can transmit the driving force to the ID 26. Hereinafter, this state will be referred to as the engaged state or the transmitting state.

[0083] In addition, when the coupling slide 53 is moved from the engaged state toward the conveying direction U1, the inclined portion 53B abuts against the left side surface of the coupler base portion 51A, and gradually moves the drum drive coupler 51 to the right, releasing the engagement with the ID connection portion 26J and pulling them apart.

[0084] Eventually, as shown in Fig. 7(B), the coupling slide 53 brings the left side surface of the coupler root portion 51A of the drum driving coupler 51 into contact with the disconnected portion 53C. As a result, the drum driving coupler 51 is in a state where the tip of the coupler tip portion 51B is positioned to the right of the right cover 34 and is separated (i.e., disconnected) from the ID connection portion 26J of the ID unit 16C, and is unable to transmit driving force to the ID 26. Hereinafter, this state will be referred to as the disconnected state or non-transmitting state.

[0085] Incidentally, when the coupling slide 53 is moved from the disconnected state toward the opposite conveying direction U2, the left side surface of the coupler base portion 51A abuts against the inclined portion 53B, and the drum drive coupler 51 gradually moves leftward, again reaching the engaged state (Figure 7(A)).

[0086] The ID coupling sensor 55 as a transmission state detection unit is a so-called optical sensor, similar to the ID up-down sensor 48 (FIG. 4), and has a light-emitting unit that emits detection light and a light-receiving unit that receives the detection light. The ID coupling sensor 55 generates a detection signal based on the light-receiving result by the light-receiving unit and notifies the control unit 3. The ID coupling sensor 55 is attached at a position where a part of the ID coupling sensor blocks the detection light when the coupling slide 53 moves to the farthest side in the counter-conveyance direction U2, that is, when each drum drive coupler 51 is in the engaged state (FIG. 8(A)). Therefore, the control unit 3 can recognize whether the drum drive coupler 51 is in the engaged state based on the detection signal acquired from the ID coupling sensor 55.

[0087] In this way, in the drum coupling section 50D, the drum drive coupler 51 can be switched between an engaged state (Figure 7(A)) or a disconnected state (Figure 7(B)) by moving the coupling slide 53 in the anti-conveying direction U2 or in the conveying direction U1 based on the driving force from the paper feed motor 37.

[0088] Meanwhile, in the image forming apparatus 1, a configuration similar to the coupling unit 50 is also provided in a portion corresponding to the black (K) ID unit 16K, and the drum drive coupler 51 and the like can be switched between an engaged state and a disconnected state. The image forming apparatus 1 is also provided with an interlocking mechanism (not shown) that interlocks the opening and closing of the upper cover 2C (FIG. 1) with the switching operation of the coupling unit 50 and the like to the engaged state or the disconnected state. For this reason, when the upper cover 2C is opened, the image forming apparatus 1 switches the drum drive couplers 51 and the like to the disconnected state in the ID units 16 of all colors.

[0089] [1-3. Circuit configuration of image forming device] Next, the circuit configuration of the image forming apparatus 1 will be described with reference to the block diagram of Fig. 9. The control unit 3 of the image forming apparatus 1 is roughly divided into a controller unit (CU: Controller Unit) control unit 60 and a print engine unit (PU: Print engine Unit) control unit 70.

[0090] The CU control unit 60 has a CPU (Central Processing Unit) 61, a ROM (Read Only Memory) 62, a RAM (Random Access Memory) 63, and an EEPROM (Electronically Erasable and Programmable Read Only Memory) 64. The CU control unit 60 reads a predetermined program from the ROM 62, the EEPROM 64, etc. by the CPU 61, and executes the program using the RAM 63 as a working area, thereby performing various processes related to communication processing with a higher-level device (not shown), displaying information on the touch panel 4, accepting operation input, etc.

[0091] The CU control unit 60 is also connected to the touch panel 4 and a host interface (I / F) 65. The host interface 65 is an interface such as a wired LAN (Local Area Network) conforming to the IEEE (Institute of Electrical and Electronics Engineers) 802.3 (IEEE802.3u / ab / an / ae) standard, and is connected to a higher-level device (not shown).

[0092] Furthermore, the CU control unit 60 is connected to the PU control unit 70 by a video interface (I / F) 67 for transmitting image data and a communication interface (I / F) 68 for transmitting and receiving various information. For example, when the CU control unit 60 acquires print data from a higher-level device via the host interface 65, it starts a print job. Specifically, the CU control unit 60 executes a predetermined processing program, conversion program, etc. to create a print command, and converts the print data into image data by expanding it into a bitmap. Next, the CU control unit 60 transmits the print command to the PU control unit 70 via the communication interface 68, and transmits the image data to the PU control unit 70 via the video interface 67 by a method such as DMA (Direct Memory Access) transfer.

[0093] The PU control unit 70 has a configuration similar to that of the CU control unit 60, and includes a CPU 71, a ROM 72, a RAM 73, and an EEPROM 74. The PU control unit 70 reads out a predetermined program from the ROM 72, EEPROM 74, etc. by the CPU 71, and executes the program using the RAM 73 as a working area, thereby performing various processes related to each unit in the image forming apparatus 1, such as obtaining notifications from various sensors and controlling various motors. The RAM 73 is also capable of storing whether or not the above-mentioned "image drum stabilization request" has been set.

[0094] The image processing unit 75 is connected to the PU control unit 70 and the LED heads 28 of each color. The image processing unit 75 acquires image data from the PU control unit 70, adjusts the color of the image data, performs image processing such as separating the image data into four colors, and supplies the image data to the LED heads 28 of each color.

[0095] The belt motor 35, the ID motor 36, the paper feed motor 37, and the fixing motor 38 are connected to the PU control unit 70, and each operates under the control of the PU control unit 70. The fixing heater 17H generates heat under the control of the PU control unit 70, and appropriately heats the fixing roller 17A (FIG. 1). The paper feed sensor 10, the writing sensor 12, the paper discharge sensor 19, the temperature and humidity sensor 5, the ID up-down sensor 48, and the ID coupling sensor 55 notify the PU control unit 70 of their respective detection results, etc. The toner remaining amount sensor 21S detects whether the remaining amount of toner in the toner storage unit 21 falls below a predetermined reference value. The upper cover sensor 2CS detects whether the upper cover 2C has been opened or closed, and notifies the PU control unit 70 of the obtained detection result.

[0096] The paper feed roller clutch 77 switches whether to supply driving force from the paper feed motor 37 to the paper feed roller 8 (FIG. 1) based on the control of the PU control unit 70. The registration roller clutch 78 switches whether to supply driving force from the paper feed motor 37 to the registration roller 11 (FIG. 1) based on the control of the PU control unit 70. The ID up-down clutch 46 and the ID coupling clutch 54 each switch whether to transmit driving force between two gears based on the control of the PU control unit 70.

[0097] For example, when the PU control unit 70 receives a print command and image data from the CU control unit 60, it creates page information for each page of the image data, as shown in Fig. 10. This page information has the following major items: "page ID", "parameters", and "control information". Of these, the "page ID" item contains information indicating the number of pages in the print job, expressed, for example, as a numerical value.

[0098] The "Parameter" item is information that indicates adjustment values ​​and setting values ​​related to various print setting information. This "Parameter" item has sub-items such as "Paper Size", "Paper Feed Tray", "Print DPI (dots per inch)", "Media Type", "Color / Monochrome", "Double-Sided / Single-Sided", "Paper Size Check", and "Darkness". In addition to these, the "Parameter" item has sub-items such as "Paper Length", "Paper Width", "Paper Thickness", "Stacker", "Soft 4-Level Gradation", "Left Margin Length", "Right Margin Length", "Top Margin Length", and "Bottom Margin Length".

[0099] The "control information" item is information that indicates adjustment values ​​and setting values ​​related to various print controls. This "control information" item has sub-items such as "print speed," "heater temperature," "development voltage," and "transfer voltage." The adjustment values ​​of these "control information" items are set based on the adjustment values ​​of the "parameters" and values ​​obtained from various sensors, etc.

[0100] [1-4. Processing Procedure] Next, a printing process executed by the PU control unit 70 after the image forming apparatus 1 acquires print data from a higher-level device and the CU control unit 60 creates a print command and converts the data into image data will be described.

[0101] [1-4-1. Printing process procedure] When the PU control unit 70 is notified by the CU control unit 60 that print data has been acquired from a higher-level device, it reads out a predetermined program from the EEPROM 74 and executes it to start the PU print processing procedure RT1 shown in Fig. 11, and proceeds to the first step SP1. In step SP1, the PU control unit 70 receives image data and a print command from the CU control unit 60 via the video interface 67 and communication interface 68, and proceeds to the next step SP2.

[0102] In step SP2, the PU control unit 70 stores adjustment values, etc. in each subitem of "parameter" in the page information (Fig. 10), creates adjustment values ​​for "control information" based on the adjustment values ​​of the "parameter" and values ​​obtained from various sensors, sets these in the page information, and proceeds to the next step SP3. In step SP3, the PU control unit 70 executes an ID up-down process (described in detail later) as a subroutine to raise and lower the color ID unit 16CMY, and proceeds to the next step SP4.

[0103] In step SP4, the PU control unit 70 performs a print transport process, and proceeds to the next step SP5. This print transport process is a process in which, for example, one sheet of paper P is transported along the transport path U, a toner image is generated by the ID unit 16 and transferred to the paper P, and the toner image is further fixed by the fixing unit 17, thereby printing an image on the paper P. In step SP5, the PU control unit 70 ends the PU print processing procedure RT1.

[0104] [1-4-2. Image drum up / down processing procedure] Next, an image drum (ID) up-down process executed as a subroutine in step SP3 of the PU print processing procedure RT1 (FIG. 11) will be described. When the PU control unit 70 proceeds to step SP4 in the PU print processing procedure RT1, it reads out a predetermined program from the EEPROM 74 and executes it to start the ID up-down processing procedure RT2 shown in FIG. 12, and proceeds to the first step SP21.

[0105] In step SP21, the PU control unit 70 judges whether or not color printing is to be performed by referring to the page information (FIG. 10). If a positive result is obtained here, this indicates that a color toner image needs to be generated using the color ID unit 16CMY and transferred to the paper P. In this case, the PU control unit 70 proceeds to the next step SP22.

[0106] In step SP22, the PU control unit 70 judges whether the color ID unit 16CMY is in the separated state (FIG. 6(B)) based on the detection result obtained from the ID up-down sensor 48 (FIG. 4). If a positive result is obtained here, this indicates that the color ID unit 16CMY needs to be lowered (down) to transition to the close state and moved to the transfer position. At this time, the PU control unit 70 proceeds to the next step SP23.

[0107] In step SP23, the PU control unit 70 judges whether the coupling unit 50 is in the mated state (FIG. 7(A)) based on the detection result obtained from the ID coupling sensor 55 (FIG. 7). If a positive result is obtained here, this indicates that the coupling unit 50 is in the mated state, and if the color ID unit 16CMY is shifted from the separated state to the close state in this state, there is a possibility that the drum drive coupler 51 and the like may be damaged. In this case, the PU control unit 70 proceeds to the next step SP24.

[0108] Incidentally, in the image forming apparatus 1, when the color ID unit 16CMY is in the separated state (FIG. 6B), the coupling portion 50 should be in the disconnected state (FIG. 7B), but due to some malfunction, the coupling slide 53 may be in the engaged state. For this reason, the PU control portion 70 performs a determination process such as step SP23.

[0109] In step SP24, the PU control unit 70 controls the sheet feed motor 37 (FIG. 3) and the ID coupling clutch 54 (FIG. 7) to switch the coupling unit 50 from the engaged state to the disengaged state, and then proceeds to the next step SP25.

[0110] On the other hand, if a negative result is obtained in step SP23, this indicates that the coupling unit 50 is already in the disconnected state (FIG. 7(B)) and there is no need to operate the coupling unit 50. At this time, the PU control unit 70 proceeds to the next step SP25. In step SP25, the PU control unit 70 controls the fixing motor 38 (FIG. 3) and the ID up-down clutch 46 (FIG. 4) to operate the contact unit 40, lowering the color ID unit 16CMY from the separated state to switch it to the close state, and proceeds to the next step SP27. At this time, the color ID unit 16CMY may or may not have reached the transfer position.

[0111] On the other hand, if a negative result is obtained in step SP22, this indicates that the color ID unit 16CMY is in the proximity state. In this case, the PU control unit 70 proceeds to the next step SP26, and determines whether or not the coupling unit 50 is in the mated state (FIG. 7(A)) based on the detection result obtained from the ID coupling sensor 55 (FIG. 7), as in step SP23. If a negative result is obtained here, the PU control unit 70 proceeds to the next step SP27.

[0112] In step SP27, the PU control unit 70 controls the sheet feed motor 37 (FIG. 3) and the ID coupling clutch 54 (FIG. 7) to switch the coupling unit 50 from the disconnected state to the engaged state, and then proceeds to the next step SP29.

[0113] On the other hand, if a positive result is obtained in step SP26, this indicates that the color ID unit 16CMY is in the proximity state and the coupling unit 50 is in the mated state. In this case, the PU control unit 70 proceeds to the next step SP28. In step SP28, the PU control unit 70 determines whether or not an ID stabilization request has been set by referring to the RAM 73. If a positive result is obtained here, this indicates that the color ID unit 16CMY may be in the intermediate position (FIG. 6(C)) due to the possibility that the user has attached or detached the color ID unit 16CMY, and therefore it is necessary to perform ID stabilization processing. In this case, the PU control unit 70 proceeds to the next step SP29.

[0114] In step SP29, the PU control unit 70 performs ID stabilization processing as a subroutine (described in detail later), and moves to the next step SP30 after the color ID unit 16CMY reaches the transfer position (FIG. 6(A)). In step SP30, the PU control unit 70 clears (deletes) the ID stabilization request set in the RAM 73, and moves to the next step SP35.

[0115] If a negative result is obtained in step SP28, this indicates that there is a possibility that the color ID unit 16CMY has already reached the transfer position (FIG. 6(A)), and therefore there is no need to perform ID stabilization processing. In this case, the PU control unit 70 proceeds to the next step SP35.

[0116] On the other hand, if a negative result is obtained in step SP21, this indicates that monochrome printing is required and the color ID unit 16CMY must be placed in the separated state (FIG. 6(B)). In this case, the PU control unit 70 proceeds to the next step SP31.

[0117] In step SP31, the PU control unit 70 determines whether the coupling unit 50 is in the mated state (FIG. 7(A)) based on the detection result obtained from the ID coupling sensor 55 (FIG. 7), as in step SP23. If a positive result is obtained here, this indicates that the coupling unit 50 is in the mated state, and that the coupling unit 50 needs to be transitioned to the disconnected state before transitioning the color ID unit 16CMY from the close state to the separated state. In this case, the PU control unit 70 proceeds to the next step SP32.

[0118] In step SP32, the PU control unit 70 controls the sheet feed motor 37 (FIG. 3) and the ID coupling clutch 54 (FIG. 7) to switch the coupling unit 50 from the engaged state to the disengaged state, similarly to step SP24, and then proceeds to the next step SP33.

[0119] On the other hand, if a negative result is obtained in step SP31, this means that the coupling unit 50 is already in a disconnected state. In this case, the PU control unit 70 proceeds to the next step SP33.

[0120] In step SP33, the PU control unit 70 determines whether the color ID unit 16CMY is in the separated state (FIG. 6(B)) based on the detection result obtained from the ID up-down sensor 48 (FIG. 4), as in step SP22. If a negative result is obtained here, this indicates that the color ID unit 16CMY needs to be raised (up) to transition to the separated state. In this case, the PU control unit 70 proceeds to the next step SP34.

[0121] In step SP34, the PU control unit 70 operates the separation unit 40 by controlling the fixing motor 38 (Figure 3) and the ID up-down clutch 46 (Figure 4), raises (up) the color ID unit 16CMY from the close state to switch it to the separated state, and then proceeds to the next step SP35.

[0122] On the other hand, if a positive result is obtained in step SP33, this means that the color ID unit 16CMY is already in the separated state and should be maintained in this state, In this case, the PU control unit 70 proceeds to the next step SP35.

[0123] In step SP35, the PU control unit 70 ends the ID up / down processing procedure RT2, and returns to step SP3 of the original PU print processing procedure RT1 (FIG. 11).

[0124] [1-4-3. Image drum stabilization procedure] Next, the image drum (ID) stabilization process executed as a subroutine in step SP29 of the ID up-down process procedure RT2 will be described. When the PU control unit 70 proceeds to step SP29 in the ID up-down process procedure RT2, it starts the image drum (ID) stabilization process procedure RT4 shown in Fig. 13 by reading and executing a predetermined program from the EEPROM 74, and proceeds to the first step SP41. In step SP41, the PU control unit 70 reads the first standby time T1 and the second standby time T2 from the EEPROM 74, and proceeds to the next step SP42. The first standby time T1 and the second standby time T2 are preset values.

[0125] In step SP42, the PU control unit 70 determines whether the amount of toner contained in the toner container 21 (ie, the remaining amount) is equal to or less than a reference value, ie, whether the toner container 21 is in a toner-low state, based on the detection result obtained from the remaining toner sensor 21S.

[0126] If a positive result is obtained here, this indicates that the amount of toner contained in the toner storage section 21 is relatively small, and therefore the weight of the ID unit 16 is relatively small (i.e., light). This also indicates that when the separation / attachment section 40 transitions the color ID unit 16CMY from the separated state to the adjacent state, the color ID unit 16CMY may stop at an intermediate position and the distance from the transfer position may be relatively large. In this case, the PU control section 70 proceeds to the next step SP43. In step SP43, the PU control section 70 increases the second waiting time T2 by adding a predetermined correction value to the second waiting time T2, and proceeds to the next step SP44.

[0127] On the other hand, if a negative result is obtained in step SP42, this indicates that the amount of toner contained in the toner container 21 is relatively large, and therefore the weight of the ID unit 16 is relatively large (i.e., heavy). In this case, the PU control unit 70 proceeds to the next step SP44 without correcting the second standby time T2.

[0128] In step SP44, the PU control unit 70 starts driving the belt motor 35 (FIG. 3), and proceeds to the next step SP45. At this time, the PU control unit 70 controls the running speed (i.e., linear speed) of the conveyor belt 15 (FIGS. 1 and 2) to a predetermined speed VB1, as shown in FIG. 14. Specifically, the PU control unit 70 controls the rotation speed of the belt motor 35 so that the speed VB1 of the conveyor belt 15 becomes 96 [mm / s], which corresponds to 16 PPM (Page Per Minute). Hereinafter, the speed VB1 is also referred to as the medium speed.

[0129] In step SP45, the PU control unit 70 waits for a predetermined first waiting time T1, and then proceeds to the next step SP46. This first waiting time T1 is set because, as described above, the ID motor 36 is a DC motor and can start driving immediately, whereas the belt motor 35 is a stepping motor and requires a certain amount of time for a stabilization process when driving starts.

[0130] In step SP46, the PU control unit 70 starts driving the ID motor 36 (FIG. 3), and proceeds to the next step SP47. At this time, the PU control unit 70 controls the running speed (i.e., linear speed) on the circumferential side of the ID 26 (FIG. 2) to be a predetermined speed VD1. Specifically, the PU control unit 70 controls the rotation speed of the ID motor 36 so that the speed VD1 on the circumferential side of the ID 26 is 72 [mm / s], which corresponds to 12 PPM. That is, the speed VD1 forms a speed difference with the speed VB1, and is a value smaller than the speed VB1. In addition, the speed ratio, which is the ratio of the speed VB1 to the speed VD1, is 1.33. In the following, the speed VD1 is also referred to as the image carrier speed. In addition, in the following, the ID stabilization process is also referred to as the speed difference forming process.

[0131] At this time, in the image forming apparatus 1, a linear velocity VD1 in the vicinity of the lower end of ID26 in the color ID unit 16CMY toward the transport direction U1 is smaller than a linear velocity VB1 in the transport direction U1 of the conveyor belt 15. Therefore, a force in the transport direction U1 is applied by the conveyor belt 15 to ID26 at the contact point with the conveyor belt 15, and the ID26 is pulled toward the transport direction U1.

[0132] Here, assume that the color ID unit 16CMY is located at the intermediate position. At this time, as shown in Fig. 5, the positioning protrusion 29 of the color ID unit 16CMY is located at the protrusion intermediate position Q2 in the groove 42D of the contact guide 42, and the color ID unit 16CMY is in a state in which it can only move in a direction along the groove axis XD. Therefore, when a force in the conveying direction U1 acts on the ID 26, the color ID unit 16CMY displaces the positioning protrusion 29 in a downward and rearward direction so as to align with the groove axis XD, and eventually reaches the protrusion transfer position Q1, where it can be located at the transfer position.

[0133] In step SP47 (FIG. 12), the PU control unit 70 waits for a predetermined second wait time T2, and then proceeds to the next step SP48. This second wait time T2 is set in advance, for example, within a range of 100 ms to 10 s. If a correction value was added to the second wait time T2 in step SP43, the PU control unit 70 waits for the corrected second wait time T2. In step SP48, the PU control unit 70 stops the belt motor 35 and the ID motor 36, and then proceeds to the next step SP49 to end the ID stabilization processing procedure RT4.

[0134] [1-5. Effects, etc.] In the above configuration, the image forming apparatus 1 according to the first embodiment switches the color ID unit 16CMY between a close state and a separated state using the contact / separation section 40, and at this time moves the positioning protrusions 29 of each ID unit 16 in a direction along the groove axis XD within the groove section 42D of the contact / separation guide 42 (Figures 5 and 6).

[0135] Then, when color printing is performed in the printing process, if certain conditions are satisfied, the image forming apparatus 1 performs ID stabilization processing, rotates the ID 26, and runs the conveyor belt 15 at a higher speed (FIGS. 13 and 14).

[0136] At this time, in the ID stabilization process, the image forming apparatus 1 can apply a force to the color ID unit 16CMY in the conveying direction U1 by intentionally providing a speed difference between the ID 26 and the conveying belt 15. Here, in the image forming apparatus 1, the groove axis XD of the separation and contact guide 42 is inclined with respect to the conveying normal XN, and is designed to descend as it proceeds in the conveying direction U1 and approach the conveying path U. Therefore, the image forming apparatus 1 can move the positioning protrusion 29 diagonally downward and rearward along the groove portion 42D, and as a result, the color ID unit 16CMY can reach the transfer position.

[0137] In this way, even if the color ID unit 16CMY is located in the intermediate position, the image forming apparatus 1 can move the color ID unit 16CMY to the transfer position by performing the ID stabilization process, thereby enabling the image forming apparatus 1 to print high-quality images with significantly reduced color shift.

[0138] However, in the image forming apparatus 1, if only the conveyor belt 15 is run during the ID stabilization process, there is a risk that the belt motor 35, which is a stepping motor, will lose synchronization. In this case, only a specific portion of the ID 26 in the image forming apparatus 1 will slide against the conveyor belt 15, causing localized wear, which may lead to deterioration in the image quality of the toner image. Therefore, in the ID stabilization process, the image forming apparatus 1 does not operate only either the ID 26 or the conveyor belt 15, but operates both and provides a predetermined speed difference between the two, thereby avoiding problems such as loss of synchronization and deterioration in image quality.

[0139] Furthermore, in step SP47 of the ID stabilization process (FIG. 13), the image forming apparatus 1 presets the second waiting time T2 to be 100 ms or more and 10 s or less. This enables the image forming apparatus 1 to reliably move the color ID unit 16CMY from the intermediate position to the transfer position, and prevents the time required to start the print transport process (FIG. 11, step SP4) from being excessively long.

[0140] From another perspective, the image forming apparatus 1 can move the color ID unit 16CMY from the intermediate position to the transfer position by utilizing the frictional force generated based on the speed difference between the ID 26 and the conveying belt 15 during the ID stabilization process, without providing a separate force-generating means such as an actuator.

[0141] From another point of view, in the image forming apparatus 1, the fixing motor 38 is made relatively small in size in order to reduce size and cost, and as a result, the driving force of the fixing motor 38 is also made relatively small. The contact section 40 (FIG. 4) uses the driving force from the fixing motor 38 to switch the color ID unit 16CMY from the close state to the separated state. For this reason, in the image forming apparatus 1, it is necessary to keep the urging force of the ID unit spring 2G relatively small. However, in the image forming apparatus 1, when the contact section 40 switches the color ID unit 16CMY from the separated state to the close state, the urging force of the ID unit spring 2G is relatively small, so that the color ID unit 16CMY cannot be urged to the transfer position and may stop at an intermediate position. Therefore, in the image forming apparatus 1, by performing ID stabilization processing using the ID 26 and the conveyor belt 15, it is possible to effectively suppress deterioration of image quality due to color shift while realizing reduction in size and cost.

[0142] Furthermore, in the ID stabilization process procedure RT4 (FIG. 13), the image forming apparatus 1 corrects the second standby time T2 in accordance with the amount of toner remaining in the toner storage unit 21. Therefore, even if the amount of toner remaining in the toner storage unit 21 is relatively small and the weight of the color ID unit 16CMY is relatively small, and therefore the image forming apparatus 1 is unable to move to the transfer position within the original second standby time T2 alone, the image forming apparatus 1 can be expected to move to the transfer position because the second standby time T2 is increased by the correction.

[0143] Furthermore, in the ID up-down processing procedure RT2 (FIG. 12), the image forming apparatus 1 is configured to perform ID stabilization processing when starting color printing, except when the color ID unit 16CMY is in the close state and the coupling portion 50 is in the engaged state. This allows the image forming apparatus 1 to reliably perform the ID stabilization processing when the color ID unit 16CMY may have been in the separated state after the ID stabilization processing was previously performed and the color ID unit 16CMY may have stopped at an intermediate position.

[0144] Furthermore, in the ID up / down processing procedure RT2 (FIG. 12), the image forming apparatus 1 sets an ID stabilization request when the power is turned on, and performs ID stabilization even when the color ID unit 16CMY is in a close proximity state and the coupling section 50 is in an engaged state. This allows the image forming apparatus 1 to reliably execute the ID stabilization process when there is a possibility that the color ID unit 16CMY has been attached or detached and each ID unit 16 is stopped in an intermediate position.

[0145] From another perspective, the image forming apparatus 1 does not necessarily perform the ID stabilization process when, for example, color printing is performed, but performs the ID stabilization process only when there is a possibility that the color ID unit 16CMY is stopped at an intermediate position, such as after the color ID unit 16CMY has transitioned from a distant state to a close state, etc. This allows the image forming apparatus 1 to avoid performing a wasteful operation, such as performing the ID stabilization process even when the color ID unit 16CMY is already at the transfer position.

[0146] According to the above configuration, the image forming apparatus 1 according to the first embodiment moves the positioning projection 29 of the ID unit 16 in the groove portion 42D of the contact guide 42 in a direction along the groove axis XD inclined with respect to the conveying direction U1. When performing color printing, the image forming apparatus 1 performs an ID stabilization process when the color ID unit 16CMY is lowered, rotates the ID 26, and runs the conveyor belt 15 at a higher speed than its peripheral side, applying a force toward the conveying direction U1 to the color ID unit 16CMY to reach the transfer position. This allows the image forming apparatus 1 to print high-quality images with significantly reduced color shift.

[0147] 2. Second embodiment Image forming apparatus 201 (FIG. 1) according to the second embodiment differs from image forming apparatus 1 according to the first embodiment in that it has control unit 203 instead of control unit 3, but is otherwise configured similarly.

[0148] The control unit 203 differs from the control unit 3 (FIG. 9) according to the first embodiment in that it has a PU control unit 270 instead of the PU control unit 70, but is otherwise configured similarly. The PU control unit 270 differs from the PU control unit 70 according to the first embodiment in that it has an EEPROM 274 instead of the EEPROM 74, but is otherwise configured similarly. This EEPROM 274 stores a program that is partially different from that of the EEPROM 74.

[0149] Next, we will explain the power-on process when the image forming device 201 is turned on, and the printing process that is executed by the PU control unit 270 after the image forming device 201 acquires printing data from a higher-level device and the CU control unit 60 creates a printing command and converts it into image data.

[0150] [2-1. Power-on procedure] When the power is turned on, the PU control unit 70 starts the power-on processing procedure RT20 shown in Fig. 15 by reading and executing a predetermined program from the EEPROM 274, and proceeds to the first step SP201. In step SP201, the PU control unit 70 performs a predetermined power-on initialization process, such as initializing various setting values, and proceeds to the next step SP202. In step SP202, the PU control unit 270 sets an ID stabilization request in the RAM 73, and proceeds to the next step SP203. This enables the PU control unit 270 to reliably perform ID stabilization processing when starting color printing processing later.

[0151] In step SP203, the PU control unit 270 judges whether or not a predetermined initial processing condition is satisfied. The initial processing condition here is a condition necessary for executing the initial processing described later. Specifically, the initial processing condition is set to be that no error has occurred, such as an error indicating that the LED head 28 (FIG. 2) is not attached, or an error indicating that the detection result by the temperature and humidity sensor 5 (FIG. 1) is outside a predetermined normal range.

[0152] If a positive result is obtained in step SP203, the PU control unit 270 proceeds to the next step SP204, executes initial processing (described in detail below) as a subroutine, and proceeds to the next step SP205. On the other hand, if a negative result is obtained in step SP203, this indicates that some kind of error has occurred, or the initial processing cannot be performed normally. In this case, the PU control unit 270 proceeds to the next step SP205 without performing the initial processing. In step SP205, the PU control unit 270 ends the power-on processing procedure RT20.

[0153] [2-2. Initial Processing Procedure] Next, the initial processing executed as a subroutine in step SP204 of the power-on processing procedure RT20 (FIG. 15) will be described. When the PU control unit 270 proceeds to step SP204 in the power-on processing procedure RT20, it starts the initial processing procedure RT21 shown in FIG. 16 by reading and executing a predetermined program from the EEPROM 274, and proceeds to the first step SP211.

[0154] In step SP211, the PU control unit 270 judges whether or not color shift correction processing is necessary. Specifically, the PU control unit 270 makes this judgment based on, for example, the values ​​of various variables stored in the RAM 73 and information stored in the EEPROM 274. If a positive result is obtained here, this indicates that color shift correction processing is necessary, that ID up / down processing is necessary before the color shift correction processing, and in some cases, that ID stabilization processing is necessary. In this case, the PU control unit 270 proceeds to the next step, SP212.

[0155] In step SP212, the PU control unit 270 performs an image drum (ID) up-down process (described in detail later) as a subroutine, and proceeds to the next step SP213. As a result, the PU control unit 270 puts the color ID unit 16CMY in the proximity state and puts the drum drive coupler 51 and the like in the engaged state, but there is a possibility that the color ID unit 16CMY will stop at an intermediate position.

[0156] In step SP213, the PU control unit 270 judges whether or not an ID stabilization request has been set by referring to the RAM 73. If a positive result is obtained here, the PU control unit 270 proceeds to the next step SP214, performs ID stabilization processing as in the first embodiment, and proceeds to the next step SP215. Specifically, the PU control unit 270 positions the color ID unit 16CMY at the transfer position (FIG. 6(B)) by performing an ID stabilization processing procedure RT4 (FIG. 13) as a subroutine. In step SP215, the PU control unit 270 clears (deletes) the ID stabilization request set in the RAM 73, and proceeds to the next step SP216.

[0157] On the other hand, if a negative result is obtained in step SP213, this indicates that there is a possibility that the color ID unit 16CMY is already positioned at the transfer position (FIG. 6(B)) and therefore no need to perform ID stabilization processing. In this case, the PU control unit 270 proceeds to the next step SP216. In step SP216, the PU control unit 270 executes color shift correction processing to appropriately correct position shifts in the toner images of each color transferred to the paper P, and proceeds to the next step SP217.

[0158] If a negative result is obtained in step SP211, the PU control unit 270 proceeds to step SP217. In step SP217, the PU control unit 270 ends the initial processing procedure RT21, and returns to the original power-on processing procedure RT20 (FIG. 15).

[0159] [2-3. PU printing process procedure] Next, a printing process executed by the PU control unit 270 after the image forming apparatus 201 acquires print data from a higher-level device and the CU control unit 60 creates a print command and converts the data into image data will be described.

[0160] When the PU control unit 270 is notified by the CU control unit 60 that print data has been acquired from a higher-level device, it reads out a predetermined program from the EEPROM 274 and executes it to start a PU print processing procedure RT22 shown in Fig. 17, and proceeds to the first step SP221. Incidentally, the PU print processing procedure RT22 (Fig. 17) is partially similar to the PU print processing procedure RT1 (Fig. 11) in the first embodiment.

[0161] In steps SP221 to SP223, the PU control unit 270 performs the same processes as steps SP1 to SP3 of the PU print processing procedure RT1 (FIG. 11) in the first embodiment, thereby performing ID up / down processing, and then proceeds to the next step SP224.

[0162] In step SP224, the PU control unit 270 judges whether the color ID unit 16CMY is in the separated state (FIG. 6B) based on the detection result obtained from the ID up-down sensor 48 (FIG. 4). If a negative result is obtained here, this indicates that the color ID unit 16CMY has been lowered (down) to be in the close state in order to perform color printing, but has not necessarily reached the transfer position and may be in an intermediate position. In this case, the PU control unit 270 proceeds to the next step SP225.

[0163] In step SP225, the PU control unit 270 determines whether or not an ID stabilization request has been set by referring to the RAM 73. If a positive result is obtained here, the PU control unit 270 proceeds to the next step SP226.

[0164] In step SP226, the PU control unit 270 performs the ID stabilization processing procedure RT4 (FIG. 13) as a subroutine to position the color ID unit 16CMY at the transfer position (FIG. 7(B)), and proceeds to the next step SP227. In step SP227, the PU control unit 270 clears (deletes) the ID stabilization request set in the RAM 73, and proceeds to the next step SP228.

[0165] On the other hand, if a positive result is obtained in step SP224, this means that the color ID unit 16CMY is in the separated state for monochrome printing and there is no need to perform ID stabilization processing. In this case, the PU control unit 270 proceeds to the next step SP228.

[0166] If a negative result is obtained in step SP225, this indicates that the ID stabilization request has not been set because it has been determined that ID stabilization processing is unnecessary since the color ID unit 16CMY is already positioned at the transfer position, etc. In this case, the PU control unit 270 proceeds to the next step SP228.

[0167] In step SP228, the PU control unit 270 performs the same print transport process as in step SP4 of the PU printing processing procedure RT1 (FIG. 12) in the first embodiment, and then proceeds to the next step SP229 to end the PU printing processing procedure RT22.

[0168] [2-4. Image drum up / down processing procedure] Next, the image drum (ID) up-down processing executed as a subroutine in step SP212 of the initial processing procedure RT21 (FIG. 16) and in step SP223 of the PU print processing procedure RT22 will be described. When the PU control unit 270 proceeds to step SP212 or step SP223, it reads out a predetermined program from the EEPROM 274 and executes it to start the ID up-down processing procedure RT23 shown in FIG. 18, and proceeds to the first step SP231. Incidentally, the ID up-down processing procedure RT23 (FIG. 17) is a processing procedure that is partially similar to the ID up-down processing procedure RT2 (FIG. 12) in the first embodiment.

[0169] In step SP231, the PU control unit 270 determines whether there is a request to switch the color ID unit 16CMY to the proximity state, for example, when performing color shift correction in the initial process or when performing color printing in the PU print process. If a positive result is obtained here, the PU control unit 270 proceeds to the next step SP232.

[0170] In steps SP232 to SP237, the PU control unit 270 performs the same processing as steps SP22 to SP27 of the ID up / down processing procedure RT2 (FIG. 12) in the first embodiment. Then, when the PU control unit 270 switches the coupling unit 50 to the coupled state in step SP237, it proceeds to the next step SP238. In step SP238, the PU control unit 270 sets an ID stabilization request in the RAM 73, and proceeds to the next step SP243. This enables the PU control unit 270 to reliably execute ID stabilization processing in the subsequent processing.

[0171] If a positive result is obtained in step SP236, this means that the color ID unit 16CMY is in the proximity state and the coupling unit 50 is in the engaged state, so that the color ID unit 16CMY should have already reached the transfer position, and there is no need to perform ID stabilization processing. In this case, the PU control unit 270 proceeds to the next step SP243.

[0172] On the other hand, if a negative result is obtained in step SP231, this indicates that the color ID unit 16CMY needs to be switched to the separated state, for example, when performing monochrome printing. In this case, the PU control unit 270 proceeds to the next step SP239. In steps SP239 to SP242, the PU control unit 270 performs the same processes as steps SP31 to SP34 of the ID up / down processing procedure RT2 (FIG. 12) in the first embodiment, and then proceeds to the next step SP243.

[0173] In step SP243, the PU control unit 270 ends the ID up / down processing procedure RT23, and returns to the original processing procedure (the initial processing procedure RT21 or the PU print processing procedure RT22).

[0174] [2-5. Effects, etc.] In the above configuration, the image forming apparatus 201 according to the second embodiment, like the first embodiment, switches the color ID unit 16CMY between a close state and a separated state using the contact section 40, and at this time moves the positioning protrusion 29 of each ID unit 16 in a direction along the groove axis XD within the groove section 42D of the contact guide 42 (Figures 5 and 6).

[0175] Then, when color printing is performed in the printing process, the image forming apparatus 201 performs ID stabilization processing if certain conditions are met, rotates the ID 26, and runs the conveyor belt 15 at a higher speed (FIGS. 13 and 14). As a result, the image forming apparatus 201 moves the positioning protrusion 29 diagonally downward and rearward along the groove 42D, as in the first embodiment, and as a result, the color ID unit 16CMY reaches the transfer position, making it possible to print a high-quality image with significantly reduced color shift.

[0176] Furthermore, the image forming apparatus 201 is adapted to perform ID stabilization processing not only when color printing is performed according to the PU print processing procedure RT22 (FIG. 17) but also when color shift correction processing is performed in the initial processing procedure RT21 (FIG. 16). This allows the image forming apparatus 201 to perform color shift correction processing with the color ID unit 16CMY reliably positioned at the transfer position, thereby significantly improving the accuracy, and as a result, it is possible to print high-quality images with significantly reduced color shift.

[0177] In other respects, image forming apparatus 201 can achieve the same effects as image forming apparatus 1 according to the first embodiment.

[0178] According to the above configuration, the image forming apparatus 201 according to the second embodiment moves the positioning projection 29 of the ID unit 16 in the groove 42D of the contact guide 42 in the direction along the groove axis XD inclined with respect to the transport direction U1. The image forming apparatus 201 performs ID stabilization processing before performing printing processing and color shift correction processing, rotates the ID 26, and runs the transport belt 15 at a higher speed than its peripheral surface, applying a force toward the transport direction U1 to the color ID unit 16CMY to reach the transfer position. This allows the image forming apparatus 201 to print high-quality images with significantly reduced color shift.

[0179] 3. Other embodiments In the above embodiment, in the ID stabilization process procedure RT4 (FIG. 13), the speed VB1, which is the running speed of the conveyor belt 15, is set to 96 [mm / s], the speed VD1 on the circumferential side of the ID 26 is set to 72 [mm / s], and the speed ratio, which is the ratio of the speed VB1 to the speed VD1, is set to 1.33. However, the present invention is not limited to this, and the speed ratio may be set to various other values, such as 1.25 or 1.60. In this case, by setting the speed ratio within a range of 1.2 to 2.0, it is expected that an appropriate force will be applied to the color ID unit 16CMY in the conveying direction U1. The same applies to the second embodiment.

[0180] In the above-mentioned first embodiment, the lift-up slide 43 is moved in the conveying direction U1 or the opposite conveying direction U2 in the contact section 40 (FIG. 4) to bring the proximal section 43A or the distal section 43C into contact with the lower flat section 20B of the color ID unit 16CMY, thereby lifting or lowering the color ID unit 16CMY. However, the present invention is not limited to this, and for example, a support section for supporting the color ID unit 16CMY may be provided in the device housing 2, and the support section may be moved in the vertical direction by an actuator or the like to lift or lower the color ID unit 16CMY. In addition, the present invention is not limited to a configuration in which the three color color ID units 16CMY are lifted or lowered together, and may be a configuration in which the ID units 16 of each color are lifted or lowered individually. In short, the color ID unit 16CMY can be lifted or lowered by using various well-known methods. The same applies to the second embodiment.

[0181] Furthermore, in the above-mentioned first embodiment, the inclination angle αN of the groove axis XD with respect to the conveyance normal XN in the groove portion 42D provided in the contact guide 42 (FIG. 5) of the contact portion 40 is about 15°. However, the present invention is not limited to this, and the inclination angle αN may be various other angles such as about 30° or about 10°. In this case, the inclination angle αN should at least satisfy 0<αN<90°. The same applies to the second embodiment.

[0182] Furthermore, in the above-mentioned first embodiment, the groove portion 42D provided in the contact guide 42 (FIG. 5) of the contact portion 40 is formed in a straight line along the groove axis XD. However, the present invention is not limited to this, and the groove portion 42D may have various shapes, such as a curved shape or a shape in which a straight line and a curved line are joined. In these cases, it is sufficient that the groove portion 42D has at least a part that is inclined so as to proceed in the conveying direction U1 as it approaches the conveying path U (i.e., descends). The same applies to the second embodiment.

[0183] Furthermore, in the above-mentioned first embodiment, a case has been described in which the positioning protrusion 29 is provided on the ID housing 20 side of the ID unit 16 and the groove 42D is formed in the contact guide 42 on the device housing 2 side (FIGS. 2, 3, and 5). However, the present invention is not limited to this, and for example, a groove may be formed on the ID housing 20 side of the ID unit 16 and a positioning protrusion may be provided on the contact guide 42 on the device housing 2 side. The point is that it is sufficient to be able to move the ID 26 closer to or farther away from the transport path U while regulating the position of the ID unit 16 in the device housing 2 in the transport direction U1. The same is true for the second embodiment.

[0184] Furthermore, in the above-described first embodiment, a correction value is added to the second waiting time T2 in accordance with the remaining amount of toner in the toner storage section 21 in the ID unit 16 in the ID stabilization process procedure RT4 (FIG. 13). However, the present invention is not limited to this, and for example, the second waiting time T2 may be used as is without correction regardless of the remaining amount of toner. The same applies to the second embodiment.

[0185] Furthermore, in the above-described first embodiment, a case has been described in which the ID stabilization process is not performed if the coupling unit 50 is in a mated state and the ID stabilization request has not been set in steps SP26 and SP28 of the ID up-down processing procedure RT2 (FIG. 12). However, the present invention is not limited to this, and for example, the ID stabilization process may be performed even when the coupling unit 50 is in a mated state and the ID stabilization request has not been set.

[0186] Furthermore, in the above-mentioned second embodiment, a case has been described in which if the coupling unit 50 is in the mated state in step SP236 of the ID up / down processing procedure RT23 (FIG. 18), the ID stabilization request is not set and the ID stabilization processing is not performed. However, the present invention is not limited to this, and for example, even if the coupling unit 50 is in the mated state, the ID stabilization request may be set and the ID stabilization processing may be performed.

[0187] Furthermore, in the above-mentioned first embodiment, various programs are stored in advance in the EEPROM 74 of the PU control unit 70 in the control unit 3 (FIG. 9), and the programs are read out and executed. However, the present invention is not limited to this, and for example, a program obtained from a server device (not shown) via the CU control unit 60 and the host interface 65 may be executed. The same applies to the second embodiment.

[0188] Furthermore, in the above-mentioned first embodiment, the case where the ID units 16 for four colors are provided in the image forming apparatus 1 (FIG. 1) has been described. However, the present invention is not limited to this, and for example, one or more ID units 16 that form toner images of colors called spot colors, such as white, transparent (clear), gold, silver, etc., may be further provided, for a total of five or more ID units 16. In this case, when performing printing processing using spot colors, the ID unit 16 of the spot color can be placed in a proximity state together with the color ID unit 16CMY to perform ID stabilization processing. The same applies to the second embodiment.

[0189] Furthermore, in the above-mentioned first embodiment, the image drum 26 is exposed by the LED head 28 (FIG. 2) having LED elements. However, the present invention is not limited to this, and the image drum 26 may be exposed by, for example, a laser head that emits laser light. The same applies to the second embodiment.

[0190] Furthermore, in the above-mentioned first embodiment, the upper portion of the conveyor belt 15 in the intermediate conveyor section 13, i.e., a portion of the conveyor path U, is inclined at about 10° with respect to the horizontal direction (FIG. 1). However, the present invention is not limited to this, and the upper portion of the conveyor belt 15 in the intermediate conveyor section 13 may be inclined at another angle, or may be horizontal without being inclined. The same applies to the second embodiment.

[0191] Furthermore, in the above-mentioned first embodiment, the present invention has been described as being applied to a so-called direct transfer type image forming apparatus 1 in which the ID unit 16 is disposed at a position where it abuts against the transport path U, and a toner image is directly transferred from the ID 26 of the ID unit 16 to the paper P on the transport path U (FIG. 1). However, the present invention is not limited to this, and the present invention may also be applied to, for example, an intermediate transfer type image forming apparatus in which each toner image is sequentially transferred and superimposed from each ID unit 16 to an intermediate transfer belt, and the superimposed toner images are transferred from the intermediate transfer belt to the paper P. The same applies to the second embodiment.

[0192] Furthermore, in the above-mentioned first embodiment, the case has been described where the contact guide 42 of the contact portion 40, the lift-up slide 43, etc. are provided on the left frame 31 and the right frame 32, etc. (FIG. 3) in the image forming apparatus 1, and the ID unit 16 is attached. However, the present invention is not limited to this, and for example, as in Patent Document 1, a basket that can slide relative to the apparatus housing 2 may be provided, and the contact guide 42 of the contact portion 40, the lift-up slide 43, etc. may be provided on the basket. The same applies to the second embodiment.

[0193] Furthermore, the present invention is not limited to the above-described embodiments and other embodiments. That is, the scope of application of the present invention extends to embodiments in which the above-described embodiments and the other embodiments are combined in part or in whole in any manner, or to embodiments in which parts are extracted.

[0194] Furthermore, in the above-mentioned embodiment, the present invention has been described as being applied to the image forming apparatus 1, which is a single-function printer (i.e., SFP). However, the present invention is not limited to this, and may be applied to, for example, a multifunction machine that has an image scanner function and a communication function in addition to a printer function and can also operate as a copier (copy machine) or a facsimile machine, that is, a so-called MFP (Multi Function Peripheral / Printer). The present invention may also be applied to various devices having an electrophotographic printing function, such as a facsimile machine or a copier. The same applies to the second embodiment.

[0195] Furthermore, in the above-mentioned embodiment, a case has been described in which the image forming apparatus is configured with the apparatus housing 2 as the apparatus housing, the image drum 26 as the image forming section, the intermediate conveying section 13 as the conveying section, the contact section 40 as the contact section, the fixing motor 38 as the contact drive section, the displacement regulating section 49 as the displacement regulating section, and the control section 3 as the control section. However, the present invention is not limited to this, and the image forming apparatus may be configured with an apparatus housing having various other configurations, an image forming section, a conveying section, a contact section, a contact drive section, a displacement regulating section, and a control section. [Industrial Applicability]

[0196] The present invention can be used in an image forming apparatus capable of performing color printing and monochrome printing by electrophotography, for example. [Explanation of symbols]

[0197] 1, 201...image forming apparatus, 2...apparatus housing, 2S...internal space, 3, 203...control section, 13...middle conveying section, 15...conveyor belt, 16...ID unit, 16CMY...color ID unit, 20...ID housing, 21...toner storage section, 21S...toner remaining amount sensor, 26...image drum, 26J...ID connection section, 29...positioning protrusion, 37...paper feed motor, 38...fixing motor, 40...contact section, 42...contact guide, 42D...groove section, 48 ......ID up / down sensor, 49......displacement control unit, 50......coupling unit, 51......drum drive coupler, 55......ID coupling sensor, 70, 270......PU control unit, T1......first waiting time, T2......second waiting time, U......conveyor path, U1......conveyor direction, U2......opposite conveyor direction, VB1......speed, VD1......speed, XD......groove axis, XH......horizontal axis, XN......conveyor normal, XU......conveyor axis, XV......vertical axis, αN, αV, βH, βU......tilt angle.

Claims

1. An apparatus housing having an internal space; an image forming unit provided inside the device housing and forming a developer image on a rotating image carrier using a developer; a conveying section that contacts the image carrier and conveys the medium in a conveying direction; a separation unit that displaces a position of the image forming unit with respect to the device housing between a distant position where the image carrier is distant from the medium and a close position where the image carrier is closer to the medium than the distant position; a separation / communication driving unit that drives the image forming unit to the separated position or the adjacent position; a displacement regulating portion that regulates the image forming portion to a transfer position where the developer image is transferred from the image carrier to the medium when the image forming portion is displaced in the transport direction with respect to the device housing; a control unit that controls operations of the image forming unit, the conveying unit, and the contact / separation drive unit; Equipped with When the image forming unit is displaced to the approaching position by the separation drive unit, the control unit starts a conveying operation by the conveying unit, and after a predetermined time has elapsed, starts a rotation operation of the image carrier by the image forming unit, and performs a speed difference forming process of making the image carrier speed, which is the linear velocity of the image carrier, smaller than the medium speed, which is the linear velocity of the medium by the conveying unit.

1. An image forming apparatus comprising:

2. After performing the speed difference forming process, the control unit stops the conveying operation by the conveying unit and the rotating operation of the image carrier by the image forming unit, and then performs a printing process to form the developer image on the medium.

2. The image forming apparatus according to claim 1,

3. The displacement regulating section regulates the displacement of the image forming section in the transport direction as the image carrier approaches the medium when the image forming section is displaced relative to the device housing.

2. The image forming apparatus according to claim 1,

4. The displacement regulating portion is a positioning protrusion provided on one of the image forming unit and the device housing; a groove portion provided on the other of the image forming unit and the device housing, the groove portion being configured to guide a position of the positioning protrusion; 4. The image forming apparatus according to claim 1, further comprising:

5. The conveying unit is configured to convey a sheet of paper, which is a medium, to a circular belt that runs along a circular path, or a sheet of paper conveyed by the circular belt.

5. The image forming apparatus according to claim 1, wherein the image forming apparatus further comprises: a first fixing unit;

6. The control unit sets a speed ratio, which is a ratio of the medium speed to the image carrier speed when performing the speed difference forming process, to 1.2 or more and 2.0 or less.

6. The image forming apparatus according to claim 1, wherein the image forming apparatus further comprises:

7. The control unit sets the period for performing the speed difference forming process to be not less than 100 [ms] and not more than 10 [s].

7. The image forming apparatus according to claim 1, wherein the image forming apparatus further comprises:

8. The image forming unit includes: a developer container that contains the developer; a remaining amount detection unit that detects a remaining amount of the developer; Equipped with When the remaining amount of the developer is less than a predetermined reference value, the control unit extends a period for performing the speed difference forming process more than when the remaining amount is equal to or greater than the reference value.

8. The image forming apparatus according to claim 1, wherein the image forming apparatus further comprises:

9. The control unit controls the speed difference forming process to be performed if the speed difference forming process has not been performed after the separation / advance driving unit displaces the image forming unit from the separated position to the close position.

9. The image forming apparatus according to claim 1, wherein the image forming apparatus further comprises:

10. an image forming driving unit provided in the device housing and generating a driving force for driving the image forming unit; a transmission switching unit provided in the apparatus housing, the transmission switching unit switching between a transmission state in which the driving force is transmitted to the image forming unit and a non-transmission state in which the driving force is not transmitted to the image forming unit; a transmission state detection unit that detects whether the transmission switching unit is in the transmission state or the non-transmission state; Equipped with When the control unit detects that the transmission switching unit is in the non-transmitted state in a state in which the image forming unit is displaced to the close position by the separation and contact drive unit, the control unit controls the transmission switching unit to switch to the transmitted state and to perform the speed difference formation process.

10. The image forming apparatus according to claim 1, wherein the image forming apparatus further comprises:

11. The control unit controls not to perform the speed difference forming process when the transmission switching unit detects that the transmission state is in the transmission state and the image forming unit is located at the adjacent position.

11. The image forming apparatus according to claim 10.

12. An apparatus housing having an internal space; an image forming unit provided inside the device housing and forming a developer image on a rotating image carrier using a developer; a conveying section that contacts the image carrier and conveys the medium in a conveying direction; a separation unit that displaces a position of the image forming unit with respect to the device housing between a distant position where the image carrier is distant from the medium and a close position where the image carrier is closer to the medium than the distant position; a separation / communication driving unit that drives the image forming unit to the separated position or the adjacent position; a displacement regulating portion that regulates the image forming portion to a transfer position where the developer image is transferred from the image carrier to the medium when the image forming portion is displaced in the transport direction with respect to the device housing; a control unit that controls operations of the image forming unit, the conveying unit, and the contact / separation drive unit; Equipped with When the image forming unit is displaced to the approaching position by the separation driving unit, the control unit performs a speed difference forming process of making an image carrier speed, which is a linear velocity of the image carrier, smaller than a medium speed, which is a linear velocity of the medium by the transport unit, and then stops a transport operation by the transport unit and a rotation operation of the image carrier by the image forming unit, and then performs a printing process of forming the developer image on the medium.

1. An image forming apparatus comprising:

Images