Image forming device

Abstract

To reduce contact sound generated due to contact and separation operations of a transfer member in a configuration employing a rotary system.SOLUTION: An image forming apparatus has an intermediate transfer belt, first and second transfer members, a contact and separation mechanism, a driving member, and control means. The control means includes a first mode in which the first and second transfer members are both at a separation position, a second mode in which the first transfer member is at a contact position and the second transfer member is at the separation position, and a third mode in which the first and second transfer members are both at the contact position, and executes the first, second, and third modes in this order. The rotation speed of the driving member in a first transition operation in transition from the second mode to the third mode is smaller than the rotation speed of the driving member in a second transition operation in transition from the first mode to the second mode.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus, and more particularly to an electrophotographic image forming apparatus using an electrophotographic system. [Background technology]

[0002] Conventionally, a known image forming device for outputting color images has a configuration in which multiple photosensitive drums carrying toner images on their surfaces are arranged in a row along the direction of movement of the outer surface of an intermediate transfer belt (also known as a tandem configuration).

[0003] In a tandem image forming apparatus, toner images formed on each photosensitive drum are sequentially transferred onto an intermediate transfer belt by a primary transfer member, and then the toner images on the intermediate transfer belt are secondarily transferred onto the surface of a sheet material (recording material) by a secondary transfer member, thereby outputting a color image.

[0004] In such image forming devices, the primary transfer member is generally brought into contact with the photosensitive drum with the intermediate transfer belt interposed therebetween during "image formation." On the other hand, the primary transfer member is separated from the photosensitive drum (intermediate transfer belt) during "non-image formation" to prevent deformation of the intermediate transfer belt or suppress wear of the photosensitive drum (see Patent Document 1).

[0005] Specifically, the image forming apparatus of Patent Document 1 has a "full separation mode" in which the intermediate transfer belt is separated from the photosensitive drums in four color stations (yellow, magenta, cyan, and black) when no image is formed.

[0006] Furthermore, during full-color image formation, there is a "full-color mode" in which the photosensitive drums and intermediate transfer belt are brought into contact with each other at the four color stations by primary transfer members.

[0007] Furthermore, there is a "monochrome mode" in which, during monochrome (generally black) image formation, only the black station is in contact and the other three color stations are spaced apart.

[0008] That is, the configuration of Patent Document 1 has three "operation modes" for the primary transfer member.

[0009] On the other hand, a driving means or a contact / separation means is required to switch between the three "operation modes" related to the primary transfer member. The contact / separation means can switch the state (operation mode) of the primary transfer member by distributing the driving force at appropriate times from the driving means that drives other members (for example, the fixing roller) by providing a clutch.

[0010] In addition, in such a configuration, in order to operate the contact / separation means during image formation, the operation of switching the rotation direction of the drive means and the operation of alternately stopping and starting the drive may be restricted. For example, when switching the "operation mode" of the "primary transfer member" by the contact / separation means, a method (also called a "rotary method") is generally used in which the "operation mode" of the "primary transfer member" is switched from the "full separation mode" through the other two modes "sequentially" and then back to the "full separation mode" again.

[0011] On the other hand, in image forming devices capable of forming full-color images, since there is a large amount of output of "monochrome (black) images," the "order" of switching the "operation mode" is determined so that the operation of forming monochrome images is faster than the operation of forming full-color images.

[0012] For example, in order to shorten the time required to switch the "operation mode" of the primary transfer member during monochrome image formation, the ideal "sequence" of switching the "operation mode" is as follows: First, switch from the "full separation mode," which is a non-image forming state, to the "monochrome mode," and then switch from the "monochrome mode" to the "full color mode." Next, switch from the "full color mode" to the "full separation mode" (return), in this "rotary method." [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Patent Publication No. 2014-77860 Summary of the Invention [Problem to be solved by the invention]

[0014] However, when the state of the "primary transfer member" is changed by the contact / separation means to bring the intermediate transfer belt and the photosensitive drum into contact with each other, a "contact noise" may be generated. In particular, the contact noise may be louder when switching from the "monochrome mode" to the "color mode" than when switching from the "full separation mode" to the "monochrome mode."

[0015] That is, in a "rotary type" full-color image forming apparatus having three operating modes, it is necessary to switch between the three operating modes "sequentially." Therefore, when completing a monochrome image forming operation, it is necessary to switch the primary transfer member from "monochrome mode" to "color mode," and then switch (back) to "full separation mode" via "color mode." In this case, the contact noise generated when switching from "monochrome mode" to "color mode" may be unpleasant to the user.

[0016] SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an object of the present invention is to reduce contact noise that occurs in association with the contact and separation operation of a transfer member in a rotary system configuration. [Means for solving the problem]

[0017] The image forming apparatus of the present invention , medium Transfer belt and ,before a first transfer member corresponding to a first color and capable of contacting the intermediate transfer belt; ,before a second transfer member capable of contacting the intermediate transfer belt and corresponding to a second color different from the first color; ,beforea contact / separation mechanism that can move the first transfer member and the second transfer member between a contact position where at least one of the first transfer member and the second transfer member and the intermediate transfer belt are in contact with each other and a separation position where at least one of the first transfer member and the second transfer member and the intermediate transfer belt are separated from each other; ,before a driving member that rotates the contact and separation mechanism; , regulation means and , equipped An image forming apparatus, the contact / separation mechanism includes a moving member that moves the second transfer member, and a biasing member that biases the moving member from the contact position toward the separation position against the movement of the moving member, The control means ,before a first mode forming a first state in which the first transfer member and the second transfer member are both located at the separated position; ,before a second mode forming a second state in which the first transfer member is located at the contact position and the second transfer member is located at the separation position; ,before a third mode forming a third state in which the first transfer member and the second transfer member are both located at the abutting position; ,before The first mode, the second mode, and the third mode are executed in this order. ,before The control is characterized in that the rotational speed of the drive member during a first transition operation from the second mode to the third mode is controlled to be smaller than the rotational speed of the drive member during a second transition operation from the first mode to the second mode. [Effects of the Invention]

[0018] According to the present invention, it is possible to reduce contact noise that occurs with the contact and separation operations of the transfer member in a configuration that employs a rotary system. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic vertical cross-sectional view of an image forming apparatus according to a first embodiment of the present invention; [Figure 2] FIG. 1 is a conceptual perspective view of an intermediate transfer unit in an image forming apparatus according to a first embodiment of the present invention. [Figure 3] 1 is a conceptual perspective view of an intermediate transfer unit in an image forming apparatus according to a first embodiment of the present invention, with the intermediate transfer belt, the housing, and the cleaning device removed; [Figure 4]1 is a perspective conceptual view of an intermediate transfer unit in an image forming apparatus according to a first embodiment of the present invention before assembly; [Figure 5] FIG. 1 is a conceptual perspective view of a drive shaft of a contact / separation mechanism in an image forming apparatus according to a first embodiment of the present invention. [Figure 6] FIG. 1 is a conceptual diagram showing the positional relationship between a slide member and a drive cam in an image forming apparatus according to a first embodiment of the present invention. [Figure 7] FIG. 10 is a conceptual diagram illustrating a state S1 of the intermediate transfer unit in the full separation mode in the image forming apparatus according to the first embodiment of the present invention. [Figure 8] FIG. 10 is a conceptual diagram showing a monochrome mode state S2 of the intermediate transfer unit in the image forming apparatus according to the first embodiment of the present invention. [Figure 9] FIG. 10 is a conceptual diagram showing a full-color mode state S3 of the intermediate transfer unit in the image forming apparatus according to the first embodiment of the present invention. [Figure 10] FIG. 1 is a conceptual diagram showing the relationship between switching of the operation mode of the primary transfer roller and changes in the drive speed of the drive motor in an image forming apparatus according to a first embodiment of the present invention; [Figure 11] FIG. 10 is a conceptual diagram showing the relationship between switching of the operation mode of the primary transfer roller and changes in the drive speed of the drive motor in an image forming apparatus according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] The image forming apparatus of the present invention will be described below using examples.

[0021] <First Example> [Image forming device] First, with reference to FIG. 1, the configuration of an image forming apparatus capable of forming a full-color image according to a first embodiment of the present invention will be described.

[0022] FIG. 1 is a schematic vertical cross-sectional view of an image forming apparatus according to a first embodiment of the present invention.

[0023] Specifically, Figure 1 shows the overall configuration of a full-color laser beam printer P (hereinafter referred to as "printer P") equipped with image forming units that form toner images in four colors (yellow: Y, magenta: M, cyan: C, and black: B).

[0024] 1, a printer P (image forming apparatus) includes four cartridges 1 (1Y, 1M, 1C, 1B) arranged in a horizontal direction. The cartridges 1 are detachable from a main body MB of the printer P.

[0025] The cartridge 1 includes photosensitive drums 2 (2Y, 2M, 2C, 2B) and charging rollers 3 (3Y, 3M, 3C, 3B) around the photosensitive drums 2 (image carriers) that uniformly charge the surfaces of the photosensitive drums 2. The cartridge 1 also includes integrally therewith developing rollers 4 (4Y, 4M, 4C, 4B) that deposit toner on the photosensitive drums 2 and develop the toner images. The cartridge 1 contains toner of a predetermined color (not shown in the figure), which is supplied to the surface of the developing rollers 4 by the rotation of supply rollers 5 (5Y, 5M, 5C, 5B).

[0026] Next, the operation of forming an image on the recording material S (recording medium) will be described.

[0027] The printer P rotates the pick roller 6 counterclockwise while it is in contact with the recording material S stored in the cassette 7, and feeds the recording material S to the feed roller 8 and the separation roller 9. After that, the recording material S is separated into individual sheets by the separation roller 9 and then conveyed to the registration roller 10.

[0028] In addition, the recording material S is transported to a secondary transfer roller 11 that is in contact with the surface of the belt 100 in synchronization with the formation operation of a toner image that is transferred by a registration roller 10 to the surface of the belt 100 (intermediate transfer belt) of the intermediate transfer unit T described later.

[0029] Meanwhile, in synchronization with the feeding of the recording material S, the photosensitive drum 2 rotates clockwise while the surface thereof is uniformly charged by the charging roller 3. Furthermore, while rotating clockwise, the photosensitive drum 2 is exposed to light according to an image signal by a laser scanner 12 (12Y, 12M, 12C, 12B), and an electrostatic latent image is formed.

[0030] The electrostatic latent image on the surface of the photosensitive drum 2 is developed by the developing roller 4 and visualized as a toner image. The photosensitive drum 2 is in contact with the belt 100 by four primary transfer rollers 101 (101Y, 101M, 101C, 101B), and the toner image on the surface of the photosensitive drum 2 is sequentially transferred in multiple layers onto the belt by the primary transfer rollers 101.

[0031] Thereafter, the toner images developed in multiple layers on the belt 100 are moved together with the belt 100 to a secondary transfer roller 11 by a belt drive roller 102, and then secondarily transferred onto the recording material S. The toner image transferred onto the recording material S is transported to a pair of fixing rollers 13, which is a toner fixing means, and as it passes through the nip portion of the pair of fixing rollers 13, the toner image is heated and pressed onto the recording material S, thereby fixing it. The recording material S is then discharged by a pair of discharge rollers 14 onto a discharge tray 15 at the top of the printer P, with the toner image side facing downward, and the image forming operation is completed.

[0032] The above operations are controlled by the control means CU.

[0033] [Intermediate Transfer Unit T] Next, the intermediate transfer unit T in the printer P will be described with reference to Figures 1 and 2 to 5. The intermediate transfer unit T is detachable from the apparatus main body MB.

[0034] FIG. 2 is a conceptual perspective view of an intermediate transfer unit in an image forming apparatus according to a first embodiment of the present invention.

[0035] FIG. 3 is a conceptual perspective view of the intermediate transfer unit in the image forming apparatus according to the first embodiment of the present invention, with the intermediate transfer belt, the housing, and the cleaning device removed.

[0036] FIG. 4 is a perspective conceptual diagram of the intermediate transfer unit in the image forming apparatus according to the first embodiment of the present invention before assembly.

[0037] FIG. 5 is a conceptual perspective view of a drive shaft of the contact / separation mechanism in the image forming apparatus according to the first embodiment of the present invention.

[0038] As shown in FIGS. 1 to 3, the intermediate transfer unit T integrally includes the belt 100, four primary transfer rollers 101, a belt drive roller 102, a cleaning device 103, a driven roller 104, and a tension roller 105.

[0039] The primary transfer rollers 101 are disposed at positions facing the photosensitive drums 2 on the inside of the belt 100. In addition, cleaning devices 103 for removing residual toner remaining on the surface of the belt 100 are disposed on the outer circumferential surface of the belt 100.

[0040] Belt 100 is an endless belt that is stretched and entrained around belt drive roller 102, driven roller 104, and tension roller 105, and its surface is made up of an image carrier that serves as an intermediate transfer body capable of carrying a toner image. As shown in Figure 1, when belt drive roller 102 rotates counterclockwise, belt 100 also rotates in the same direction.

[0041] 2, the intermediate transfer unit T includes a driven member 106 to which drive force is transmitted to operate the four primary transfer rollers 101. On the other hand, a drive motor MT (drive member) is provided in the printer P and is drivingly connected to the printer P so as to continuously drive the pair of fixing rollers 13 of the printer P at a constant speed during image formation operation. In this embodiment, a clutch CL is used to selectively transmit the drive force distributed from the drive motor MT to the driven member 106.

[0042] 2 and 3, slide members 107 and 108 are disposed on both axial ends of the primary transfer rollers 101 (101Y, 101M, 101C, and 101B). The slide member 107 is a means for contacting and separating the primary transfer roller 101B (first transfer member), and the slide member 108 is a means for contacting and separating the primary transfer rollers 101Y, 101M, and 101C (second transfer members). In other words, the slide members 107 and 108 constitute a contact / separation mechanism AS of the present invention.

[0043] The slide members 107 and 108 are supported by a housing 111 so as to be slidable in a direction perpendicular to the axial direction of the primary transfer roller 101. The axial direction of the primary transfer roller 101 and the rotational axis direction of the belt 100 are the same.

[0044] 4 and 5, the support member 110 has a swing shaft 110a and a boss 110b, and the primary transfer roller 101 is swingably supported on a housing 111 (not shown in the figures) by the swing shaft 110a. A transfer spring 112 is attached to the support member 110, and the primary transfer roller 101 is urged in the direction of the photosensitive drum 2 (not shown in the figures) by a predetermined elastic force of the transfer spring 112.

[0045] A contact / separation drive shaft 106a is coaxially connected to the driven member 106, and drive cams 109 are connected to both ends of the contact / separation drive shaft 106a. The drive cams 109 also constitute the contact / separation mechanism AS of the present invention. That is, in this embodiment, the contact / separation mechanism AS (slide members 107, 108, drive cam 109) is provided in the intermediate transfer unit T together with the belt 100.

[0046] Drive cam 109 is integrally formed of drive cams 109a and 109b that engage with slide member 107, and drive cams 109c and 109d that engage with slide member 108. When drive cam 109 rotates, slide members 107 and 108 slide in conjunction with each other.

[0047] The slide member 107 has a lifting cam 107a at a predetermined position, and the slide member 108 has three lifting cams 108a at predetermined positions. The lifting cams 107a and 108a and bosses 110b of the support member 110 that supports the primary transfer rollers 101B, 101Y, 101M, and 101C come into sliding contact with each other due to the elastic force of the transfer spring 112 when the slide members 107 and 108 slide.

[0048] Slider springs 113 and 114 are respectively provided on slide members 107 and 108, and elastic forces are applied to slide members 107 and 108 in opposition to the sliding movements of slide members 107 and 108, which will be described later.

[0049] With this configuration, when the driven member 106 and the drive cam 109 rotate, the slide members 107 and 108 slide and the support member 110 swings, causing the four primary transfer rollers 101 in the intermediate transfer unit T to come into contact with and separate from the belt 100.

[0050] Thus, in this embodiment, the printer P includes the belt 100, the primary transfer roller 101B, the primary transfer rollers 101Y, 101M, and 101C, the contact / separation mechanism AS, and the drive motor MT that rotates and drives the contact / separation mechanism.

[0051] The primary transfer roller 101B can come into contact with the belt 100 and corresponds to a first color (B). On the other hand, the primary transfer rollers 101Y, 101M, and 101C can come into contact with the belt 100 and correspond to second colors (Y, M, and C) different from the first color (B).

[0052] In addition, the contact / separation mechanism AS can move the primary transfer roller 101 between a contact position P1 where the belt 100 contacts at least one of the four primary transfer rollers 101, and a separation position P2 where the belt 100 is separated from at least one of the four primary transfer rollers 101.

[0053] [Operation mode of primary transfer roller 101] Next, the three operation modes (states) of the primary transfer roller 101 in the intermediate transfer unit T and the switching of the operation modes (states) will be described with reference to FIGS. 2, 6, and 7 to 9. FIG.

[0054] FIG. 6 is a conceptual diagram showing the positional relationship between the slide member and the drive cam in the image forming apparatus according to the first embodiment of the present invention.

[0055] Specifically, Fig. 6(a) shows the positional relationship between the ride member 107, slide member 108, and drive cam 109 in state S1 of the full separation mode of the primary transfer roller 101. Fig. 6(b) shows the positional relationship in state S2 of the monochrome mode. And Fig. 6(c) shows the positional relationship in state S3 of the full color mode.

[0056] FIG. 7 is a conceptual diagram showing a state S1 of the intermediate transfer unit in the full separation mode in the image forming apparatus according to the first embodiment of the present invention.

[0057] FIG. 8 is a conceptual diagram showing the state S2 of the intermediate transfer unit in the monochrome mode in the image forming apparatus according to the first embodiment of the present invention.

[0058] FIG. 9 is a conceptual diagram showing a full-color mode state S3 of the intermediate transfer unit in the image forming apparatus according to the first embodiment of the present invention.

[0059] The direction of rotation and movement of each member in FIGS. 7 to 9 is as indicated by the arrows shown near each member.

[0060] 7 to 9, in this embodiment, the control unit CU has three modes. Therefore, the control unit CU can cause the primary transfer roller 101 to operate in one of three operation modes, "full separation mode M1 (first mode)," "monochrome mode M2 ​​(second mode)," and "full color mode M3 (third mode)," depending on the image forming operation.

[0061] In the all-separated mode M1, a first state S1 can be formed in which all primary transfer rollers 101 are positioned in the separated position. In the monochrome mode M2, a second state S2 can be formed in which the primary transfer roller 101K is positioned in the contact position and the primary transfer rollers 101Y, 101M, and 101C are positioned in the separated state. And in the full-color mode M3, a third state S3 can be formed in which all primary transfer rollers 101 are positioned in the contact position.

[0062] More specifically, the three operating modes of the primary transfer roller 101 in this embodiment are switched from the full separation mode via the monochrome mode to the full color mode so that the monochrome image forming operation is faster than the full color image forming operation. Then, the full color mode is subsequently switched to the full separation mode (configured in a rotary order). That is, the control unit CU can execute these modes for the primary transfer roller 101 in the order of the full separation mode M1, monochrome mode M2, and full color mode M3.

[0063] 6(a) and 7, the slide member 107 is positioned at a separated position to the right in the drawing by the drive cam 109a. In this state, the boss 110b of the support member 110 of the primary transfer roller 101B is in contact with the lifting cam 107a of the slide member 107 by the elastic force of the transfer spring 112, and the primary transfer roller 101B is at a separated position above the belt 100.

[0064] The slide member 108 is also positioned in a separated position to the right in the drawing by the drive cam 109d. In this state, the bosses 110b of the support members 110 of the primary transfer rollers 101Y, 101M, and 101C are in contact with the three lifting cams 108a of the slide member 108 by the elastic force of the transfer spring 112. The bosses 110b of the support members 110 of the primary transfer rollers 101Y, 101M, and 101C are also in a separated position above the belt 100.

[0065] In this way, all four primary transfer rollers 101 (101Y, 101M, 101C, 101B) are in the upper separated position relative to the belt 100. This is called the full separation mode. In this state, the intermediate transfer unit T is not forming images.

[0066] As shown in FIGS. 6B and 8, the slide member 108 is in the separation position to the right in the drawing, as in the full separation mode, and the primary transfer rollers 101Y, 101M, and 101C are in the separation position above the belt 100.

[0067] The slide member 107 is located at the contact position on the left side of the drawing. In this state, the support member 110 of the primary transfer roller 101B swings toward the belt 100, and the boss 110b separates from the lifting cam 107a of the slide member 107. As a result, the primary transfer roller 101B contacts the belt 100, and the belt 100 is pressed against the photosensitive drum 2B by the elastic force of the transfer spring 112.

[0068] In this way, the three primary transfer rollers 101Y, 101M, and 101C are located above the belt 100, and the primary transfer roller 101B is located in contact with the belt 100. This is called the monochrome mode. In this state, the intermediate transfer unit T is in a state for forming a monochrome image.

[0069] Switching from the full separation mode to the monochrome mode is performed by transmitting the driving force of the drive motor MT to the driven member 106 by the clutch CL described in Figure 2, and rotating the drive cam 109 clockwise by 120 degrees. When the drive cam 109 rotates, the slide member 107 is slid to the abutment position by the drive cam 109b, and the boss 110b of the support member 110 of the primary transfer roller 101B is separated from the lifting cam 107a of the slide member 107.

[0070] As the slide member 107 slides, the boss 110b comes into sliding contact with the lifting cam 107a. At this time, the elastic force of the transfer spring 112 of the primary transfer roller 101B is released, and a reverse input torque is likely to be generated in the drive cam 109 via the slide member 107. For this reason, the slider spring 113 is disposed so that an elastic force is charged in a manner opposing the sliding movement of the slide member 107.

[0071] The slide member 108 does not slide even when the drive cam 109 rotates 120 degrees, and is positioned at the separated position by the drive cam 109d.

[0072] As shown in Figures 6(c) and 9, the slide member 107 is located at the contact position on the left side of the figure, the same as in the monochrome mode, and the primary transfer roller 101B contacts the belt 100, and the belt 100 is pressed against the photosensitive drum 2B by the elastic force of the transfer spring 112.

[0073] The slide member 108 is also positioned at the contact position to the left in the drawing. In this state, the support members 110 for the three primary transfer rollers 101Y, 101M, and 101C swing toward the belt 100, and the bosses 110b are separated from the three lifting cams 108a of the slide member 108. As a result, the three primary transfer rollers 101Y, 101M, and 101C come into contact with the belt 100, and the belt 100 is pressed against the photosensitive drums 2Y, 2M, and 2C by the elastic force of the transfer springs 112.

[0074] In this way, all four primary transfer rollers 101 (101Y, 101M, 101C, 101B) are in contact with the belt 100. This is called the full-color mode. In this state, the intermediate transfer unit T is in a state for forming a full-color image.

[0075] Switching from monochrome mode to full color mode is performed by rotating the drive cam 109 clockwise by 120 degrees using the clutch CL in Fig. 2, just like the full separation mode. When the drive cam 109 rotates, the slide member 108 is slid to the contact position by the drive cam 109c, and the boss 110b of the support member 110 for the three primary transfer rollers 101Y, 101M, and 101C is separated from the lifting cam 108a of the slide member 108.

[0076] As the slide member 108 slides, the boss 110b comes into sliding contact with the lifting cam 107a. At this time, the elastic forces of the transfer springs 112 of the three primary transfer rollers 101Y, 101M, and 101C are released, and a reverse input torque is likely to be generated in the drive cam 109 via the slide member 108. For this reason, the slider spring 114 is disposed so that an elastic force is charged in a manner opposing the sliding movement of the slide member 108.

[0077] The slide member 107 does not slide even when the drive cam 109a rotates 120 degrees, and is positioned at the abutting position by the drive cam 109b.

[0078] Switching from full color mode to full separation mode is performed by rotating drive cam 109 clockwise by 120 degrees using clutch CL in Fig. 2, just like other mode switches. When drive cam 109 rotates, slide members 107 and 108 are slid by drive cams 109a and 109d to the separation position to the right in the figure, thereby returning to the full separation mode in Fig. 7 again.

[0079] As the slide members 107 and 108 slide from the contact position to the separated position, the boss 110b of the support member 110 of the primary transfer roller 101B comes into contact with the lifting cam 107a of the slide member 107. In addition, the bosses 110b of the support members 110 of the three primary transfer rollers 101Y, 101M, and 101C also come into contact with the three lifting cams 108a of the slide member 108.

[0080] At this time, in order to push up the primary transfer roller 101 from the belt 100, the four transfer springs 112 are charged with elastic force, and the slider springs 113 and 114 are released from their elastic force.

[0081] In this way, the driving cam 109 rotates by 120 degrees, and the slide members 107 and 108 slide between the separated position and the abutting position, thereby switching the operation mode of the primary transfer roller 101.

[0082] [Relationship between the operation mode of the primary transfer roller and the drive speed of the drive motor] The driving speed of the driving motor MT in the first embodiment will be described with reference to FIG.

[0083] FIG. 10 is a conceptual diagram showing the relationship between switching of the operation mode of the primary transfer roller and changes in the drive speed of the drive motor in the image forming apparatus according to the first embodiment of the present invention.

[0084] That is, FIG. 10 shows the relationship between the three operation modes of the primary transfer roller 101 in the printer P shown in FIG. 1, the drive speed of the drive motor MT, and the elapsed time.

[0085] 10, the drive motor MT is stopped when the printer P is not forming images, such as when it is on standby. In this state, the operation mode of the primary transfer roller 101 is in the full separation mode.

[0086] The drive motor MT is controlled by the control unit CU so as to switch between two steady speeds, drive speed SP1 (rotation speed) and drive speed SP2 (rotation speed), while the printer P is forming an image. In this embodiment, the drive speeds are SP1>SP2.

[0087] Next, the printer P starts rotating the drive motor MT at SP1 to start the monochrome image forming operation. This drive speed is the rotation speed required for steady rotation of the fixing roller pair 13 as described with reference to FIG.

[0088] Then, at a predetermined timing when the drive motor MT is rotating steadily at SP1, the clutch CL in Fig. 2 distributes and transmits the drive force of the drive motor MT to the driven member 106 for a predetermined time. Then, first, the slide member 107 (not shown in the figure), which is the contact / separation means, slides from the separated position to the contact position over time T12 (the period of the second transition operation), and the monochrome mode is entered. The second transition operation (T12) is an operation for transitioning from the full separation mode M1 (state S1) to the monochrome mode M2 ​​(state S2).

[0089] In a state where the printer has switched from the full separation mode to the monochrome mode, the drive speed of the drive motor MT is reduced to SP2 after the sheet material S (not shown) on which a monochrome image has been formed by a series of image forming operations is discharged from the printer P. This drive speed does not affect the monochrome image forming operation, so it can be made as slow as possible compared to SP1, which is the drive speed when the printer has switched from the full separation mode to the monochrome mode.

[0090] Then, at a predetermined timing when the drive motor MT is rotating steadily at the speed SP2, the clutch CL again distributes and transmits the drive force of the drive motor MT to the driven member 106 for a predetermined time. Then, the slide member 108 (not shown in the figure), which is the contact / separation means, slides from the separated position to the contact position over a time T23 (the period of the first transition operation), and the full-color mode is entered. The first transition operation (T23) is an operation for transitioning from the monochrome mode M2 ​​(state S2) to the full-color mode M3 (state S3).

[0091] When operating from the monochrome mode to the full color mode, the driving speed of the driving motor MT is slower than when operating from the full separation mode to the monochrome mode. Therefore, the time (length of the period) required to switch the operating mode of the primary transfer roller 101 is T12. <T23となる。

[0092] In monochrome image formation, the transition from full-color mode to full-separation mode is swiftly performed by transmitting the driving force of the drive motor MT to the driven member 106 via the clutch CL in FIG. 2. Then, the slide member 107 (not shown) and the ride member 108 (not shown) slide from the contact position to the separation position over a period of time (period T31 of the third transition operation), and the printer P enters full-separation mode. After the printer P enters full-separation mode, the drive motor MT stops driving, and the printer P enters a non-image-forming state, such as standby mode. The third transition operation (T31) is the operation of transitioning from full-color mode M3 (state S3) to full-separation mode M1 (state S1).

[0093] In other words, in this embodiment, the control means CU controls the rotational speed (SP2) of the drive motor MT during the first transition operation T23, which transitions from monochrome mode M2 ​​to full color mode M3, to be smaller than the rotational speed (SP1) of the drive motor MT during the second transition operation T12, which transitions from full separation mode M1 to monochrome mode M2.

[0094] That is, conventionally, the contact noise generated by the movement of the primary transfer roller is affected by the operating speed of the contact / separation roller. The faster the operating speed, the more likely it is that a louder contact noise will be generated. On the other hand, there is a limit to how slow the operating speed can be in order to start the image formation operation early.

[0095] To address this issue, in this embodiment, during monochrome image formation in the intermediate transfer unit T of the printer P, the operating speed of the contact / separation means can be slower in full-color mode than in monochrome mode. This allows the operating time for the multiple primary transfer rollers 101 to contact the belt 100 to be longer, thereby slowing the operating speed and reducing the contact noise generated when the primary transfer rollers 101 contact the belt 100. That is, this configuration of the present embodiment can reduce the contact noise generated when the intermediate transfer belt contacts the photosensitive drum due to the contact / separation operation of the primary transfer member in a rotary system configuration. In particular, by reducing (bringing closer) the contact noise generated when switching from monochrome mode to full-color mode to the contact noise generated when switching from full-separation mode to monochrome mode, the level of the contact noise generated when switching between modes can be made more constant (stable). This softens the user's impression of the contact noise. Therefore, this invention allows for quick start of monochrome mode and suppresses the contact noise generated when switching modes.

[0096] Furthermore, since the drive speed of the drive motor MT, which must rotate at a steady speed during image formation, is reduced at a timing that does not affect monochrome image formation, there is no need to increase costs by installing dedicated components such as soundproofing materials. Furthermore, contact noise can be reduced without causing performance degradation such as a longer first printout time in monochrome image output.

[0097] In this embodiment, the timing for decelerating the driving speed of the driving motor MT may be the timing when the sheet material S is discharged from the pair of fixing rollers 13.

[0098] The drive motor MT is not limited to driving the pair of fixing rollers 13, but may also be a motor that rotates at a steady speed during image formation operations, such as driving a roller for conveying the sheet material S, driving the belt drive roller 102 in the intermediate transfer unit T, or driving the photosensitive drum 2. In this case, the timing for slowing down the drive speed of the motor may be the timing when it is no longer necessary to rotate at the steady speed.

[0099] <Second Example> Next, the driving speed of the driving motor MT in the second embodiment of the present invention will be described with reference to FIG.

[0100] FIG. 11 is a conceptual diagram showing the relationship between switching of the operation mode of the primary transfer roller and changes in the drive speed of the drive motor in an image forming apparatus according to a second embodiment of the present invention.

[0101] That is, FIG. 11 shows the relationship between the three operation modes of the primary transfer roller 101 in the printer P, the drive speed of the drive motor MT, and the elapsed time.

[0102] The only difference from the first embodiment is the control for changing the drive speed of the drive motor MT, so a description of the configuration of the second embodiment will be omitted.

[0103] 11, the drive motor MT is stopped when the printer P is not forming images, such as when it is on standby. In this state, the operation mode of the primary transfer roller 101 is in the full separation mode.

[0104] As in the first embodiment, the drive motor MT is controlled to switch between two steady speeds, drive speed SP1 and drive speed SP2, while the printer P is forming an image. The drive speeds SP1>SP2.

[0105] The relationship between the driving speed of the driving motor MT and the elapsed time when the operation changes from the full separation mode through the monochrome mode to the full color mode is the same as that described above in the first embodiment.

[0106] Next, when switching from full-color mode to all-separation mode, the drive speed of drive motor MT is increased from SP2 to SP1. Then, slide member 107 (not shown) and slide member 108 (not shown) slide from the contact position to the separation position over time T310 (period of the third transition operation), entering all-separation mode. The third transition operation (T310) is an operation for switching from full-color mode M3 (state S3) to all-separation mode M1 (state S1).

[0107] The drive speed of the drive motor MT when switching from full color mode to all separation mode is faster than in the first embodiment, so the time (length of the period) required to switch from full color mode to all separation mode is T31>T310. After switching to all separation mode, the drive motor MT stops driving and the printer P enters a non-image forming state, such as standby, as in the first embodiment.

[0108] As described above, according to this embodiment, in monochrome image formation operation, the operating speed of the contact / separation means in full color mode can be made slower than in monochrome mode, thereby reducing the contact noise generated when the multiple primary transfer rollers 101 contact the belt 100. In particular, in the second embodiment, the time required to switch from full color mode to full separation mode can be made shorter than in the first embodiment, thereby shortening the time from the start of image formation to returning to the standby state.

[0109] In this embodiment, the speed at which the drive speed of the drive motor MT is increased from SP2 when operating from the color mode to the full separation mode is not limited to SP1, but may be any speed faster than SP2.

[0110] According to the present invention, during monochrome image formation operations in a color image forming device, the contact noise generated when the intermediate transfer belt contacts the photosensitive drum due to the operation of multiple primary transfer members by the contact / separation mechanism can be reduced.

[0111] Furthermore, there is no need to increase costs by providing special components to reduce the contact noise, and the contact noise can be reduced without causing performance degradation such as a longer first printout time in monochrome image output.

[0112] The present invention can be summarized as follows. (1) The image forming apparatus (P) of the present invention has an intermediate transfer belt (100), a first transfer member (101B), a second transfer member (101Y, 101M, 101C), a contact / separation mechanism (AS), a drive member (MT) that rotationally drives the contact / separation mechanism, and a control means (CU).

[0113] The first transfer member is capable of contacting the intermediate transfer belt and corresponds to a first color (B).

[0114] The second transfer member is capable of contacting the intermediate transfer belt and corresponds to a second color (Y, M, C) different from the first color.

[0115] The contact / separation mechanism is capable of moving the first transfer member and the second transfer member between a contact position (P1) where at least one of the first transfer member and the second transfer member contacts the intermediate transfer belt, and a separation position (P2) where at least one of the first transfer member and the second transfer member is separated from the intermediate transfer belt.

[0116] The control means a first mode (M1) that forms a first state (S1) in which the first transfer member and the second transfer member are both positioned at a separated position; a second mode (M2) that forms a second state (S2) in which the first transfer member is located at the contact position and the second transfer member is located at the separation position; and a third mode (M3) that forms a third state (S3) in which the first transfer member and the second transfer member are both positioned at the contact position, and the first mode, second mode, and third mode are executed in this order.

[0117] The control means controls so that the rotational speed (SP2) of the driving member during the first transition operation (T23) of transitioning from the second mode to the third mode is smaller than the rotational speed (SP1) of the driving member during the second transition operation (T12) of transitioning from the first mode to the second mode. (2) In the image forming apparatus of the present invention, the control means (CU) can control the rotational speed (SP2) of the driving member during the third transition operation (T31) for transitioning from the third mode to the first mode so that it is the same as the rotational speed (SP2) of the driving member at the end of the third mode. (3) In the image forming apparatus of the present invention, the control means (CU) can control the rotational speed (SP1) of the driving member during the third transition operation (T310) for transitioning from the third mode to the first mode so that it is greater than the rotational speed (SP2) of the driving member at the end of the third mode. (4) In the image forming apparatus of the present invention, the driving member (MT) may be configured to rotate any one of the conveying device (6, 8, 10, 11) that conveys the recording medium (S), the fixing device (13), the image carrier (2), or the intermediate transfer belt (100). (5) In the image forming apparatus of the present invention, the rotation speed (SP1) of the driving member (MT) during the second transition operation (T12) can be set to the same as the rotation speed of the driving member during image formation. (6) In the image forming apparatus of the present invention, the first color (B) can be black, and the first transfer member (101B) can be a transfer member corresponding to black. (7) In the image forming apparatus of the present invention, the second color (Y, M, C) can be a color other than black, and the second transfer member (101Y, 101M, 101C) can be a transfer member corresponding to a color other than black. (8) In the image forming apparatus of the present invention, the second transfer members (101Y, 101M, 101C) may include two or more transfer members corresponding to two or more different second colors (Y, M, C). (9) In the image forming apparatus of the present invention, the contact / separation mechanism (AS) may include a first moving member (107) that moves the first transfer member, a second moving member (108) that moves the second transfer member, and a cam member (109) that moves the first moving member and the second moving member, The drive member (MT) is capable of driving the cam member (109) to rotate. (10) In the image forming apparatus of the present invention, when the cam member (109) rotates once in a predetermined rotation direction (R1), the first mode (M1), the second mode (M2), and the third mode (M3) can be switched in this order. (11) In the image forming apparatus of the present invention, the control means (CU) can repeatedly switch between the first mode (M1), the second mode (M2), and the third mode (M3) by rotating the cam member (109) one or more times. (12) In the image forming apparatus of the present invention, the contact / separation mechanism (AS) and the intermediate transfer belt (100) may be configured to be provided in the intermediate transfer unit (T), and the intermediate transfer unit may be configured to be detachable from the apparatus main body (MB). [Explanation of symbols]

[0118] 100 Belt (Intermediate Transfer Belt) 101B Primary transfer roller (first transfer member) 101C Primary transfer roller (second transfer member) 101M Primary transfer roller (secondary transfer member) 101Y Primary transfer roller (second transfer member) AS contact / separation mechanism CU control means MT drive motor (drive member) M1 Full separation mode (first mode M2 Monochrome mode (second mode) M3 Full Color Mode (3rd Mode) P Printer (image forming device) P1 contact position P2 Separate position SP1 Drive speed (rotation speed) SP2 Drive speed (rotation speed) S1 First state S2 Second state S3 Third state T12 Second transition operation T23 First transition action

Claims

1. An intermediate transfer belt; a first transfer member that corresponds to a first color and that is capable of contacting the intermediate transfer belt; a second transfer member capable of contacting the intermediate transfer belt and corresponding to a second color different from the first color; a contact / separation mechanism that can move the first transfer member and the second transfer member between a contact position where at least one of the first transfer member and the second transfer member and the intermediate transfer belt are in contact with each other and a separation position where at least one of the first transfer member and the second transfer member and the intermediate transfer belt are separated from each other; a driving member that rotates the contact / separation mechanism; a control means; An image forming apparatus comprising: The contact and separation mechanism includes: a moving member that moves the second transfer member; a biasing member that biases the moving member from the contact position toward the separated position against the movement of the moving member; and The control means a first mode forming a first state in which the first transfer member and the second transfer member are both located at the spaced position; a second mode forming a second state in which the first transfer member is located at the contact position and the second transfer member is located at the separation position; a third mode that forms a third state in which the first transfer member and the second transfer member are both located at the contact position; Executing the first mode, the second mode, and the third mode in this order; an image forming apparatus characterized in that control is performed so that the rotational speed of the drive member during a first transition operation from the second mode to the third mode is smaller than the rotational speed of the drive member during a second transition operation from the first mode to the second mode.

2. The control means 2. The image forming apparatus according to claim 1, wherein control is performed so that the rotational speed of the driving member during a third transition operation for transitioning from the third mode to the first mode is the same as the rotational speed of the driving member at the end of the third mode.

3. The control means 2. The image forming apparatus according to claim 1, wherein control is performed so that the rotational speed of the driving member during a third transition operation from the third mode to the first mode is greater than the rotational speed of the driving member at the end of the third mode.

4. The image forming apparatus according to any one of claims 1 to 3, characterized in that the driving member is configured to rotate and drive any one of a conveying device that conveys a recording medium, a fixing device, an image carrier, or the intermediate transfer belt.

5. 5. The image forming apparatus according to claim 4, wherein the rotation speed of the driving member during the second transition operation is the same as the rotation speed of the driving member during image formation.

6. the first color is black; 6. The image forming apparatus according to claim 1, wherein the first transfer member is a transfer member corresponding to the color black.

7. the second color is a color other than black, 7. The image forming apparatus according to claim 6, wherein the second transfer member is a transfer member corresponding to a color other than black.

8. 8. The image forming apparatus according to claim 7, wherein the second transfer member includes two or more transfer members corresponding to two or more different second colors.

9. When the moving member is a second moving member, The contact and separation mechanism includes: a first moving member that moves the first transfer member; The second moving member; a cam member that moves the first moving member and the second moving member, 9. The image forming apparatus according to claim 1, wherein the driving member rotates the cam member.

10. 10. The image forming apparatus according to claim 9, wherein the first mode, the second mode, and the third mode are switched in this order when the cam member rotates once in a predetermined rotation direction.

11. 11. The image forming apparatus according to claim 10, wherein the control unit repeatedly switches between the first mode, the second mode, and the third mode by rotating the cam member one or more times.

12. the contact / separation mechanism and the intermediate transfer belt are provided in an intermediate transfer unit, 12. The image forming apparatus according to claim 1, wherein the intermediate transfer unit is detachable from the main body of the apparatus.

Images