Pressing force adjusting device, transfer device and image forming apparatus

Abstract

To provide a biasing force adjusting device that can adjust a biasing force with less errors.SOLUTION: The present invention includes: a roller facing a mobile body; a roller holding member for holding the roller, the roller holding member being displaceable with respect to the mobile body; a first biasing member for applying a first biasing force to the roller holding member to make the roller contact with the mobile body; and a second biasing member for applying a second biasing force larger than the first biasing force to the roller holding member to make the roller contact with the mobile body.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a biasing force adjusting device, a transfer device, and an image forming apparatus. [Background technology]

[0002] Patent Document 1 discloses an image forming apparatus having at least one image carrier on which a toner image is formed, an intermediate transfer belt that is wound around a drive roller and a driven roller and driven to rotate, and a primary transfer means that presses the intermediate transfer belt and forms a nip between the image carrier and the intermediate transfer belt, whereby the primary transfer means sequentially transfers the toner images formed on each image carrier to the intermediate transfer belt, and a secondary transfer means that transfers the toner image on the intermediate transfer belt to a recording medium.The image forming apparatus is equipped with a nip pressure adjustment means that enables the pressure of the nip to be adjusted according to the thickness of the recording medium, thereby suppressing speed fluctuations of the intermediate transfer belt when cardboard enters the secondary transfer section and enabling improved image quality. Summary of the Invention [Problem to be solved by the invention]

[0003] An object of the present invention is to provide a biasing force adjusting device that can adjust the biasing force with a small error. [Means for solving the problem]

[0004] The present invention provides a roller that faces a moving body, a roller holding member that holds the roller and is displaceable relative to the moving body, a first biasing member that applies a first biasing force to the roller holding member to cause the roller to abut against the moving body at a first abutment position, and a second biasing member that applies a second biasing force greater than the first biasing force to the roller holding member to cause the roller to abut against the moving body at a second abutment position, wherein when the roller is to abut against the moving body at the first abutment position, only the first biasing force of the first biasing member is applied to the roller holding member, and when the roller is to abut against the moving body at the second abutment position, only the second biasing force of the second biasing member is applied to the roller holding member. When the roller is separated from the moving body, both the first biasing force and the second biasing force are applied to the roller holding member. It is characterized by: [Effects of the Invention]

[0005] According to the present invention, it is possible to provide a biasing force adjustment device that can adjust the biasing force with a small error. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 2 is an explanatory diagram showing the configuration of the biasing force adjuster according to the embodiment of the present invention (when the rollers are separated); [Figure 2] 1 is an explanatory diagram showing the configuration of a biasing force adjustment device according to an embodiment of the present invention (when a roller is in contact); [Figure 3] FIG. 2 is an explanatory diagram showing the configuration of the biasing force adjustment device according to the embodiment of the present invention (when roller contact is intensified). [Figure 4] 1 is a schematic diagram illustrating an example of an image forming apparatus in which a biasing force adjusting device according to the present invention is applied to a transfer device. [Figure 5] FIG. 2 is an explanatory diagram showing an example of a toner used in the image forming apparatus according to the embodiment of the present invention. [Figure 6] FIG. 6 is a flow chart showing a setting procedure for a shock jitter response mode in the image forming apparatus according to the embodiment of the present invention. [Figure 7] FIG. 6 is a flowchart showing an execution of a shock jitter response mode in the image forming apparatus according to the embodiment of the present invention. [Figure 8]FIG. 10 is an execution flow diagram of a modified example of the shock jitter handling mode in the image forming apparatus according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0007] An embodiment of the present invention will be described below with reference to the drawings.

[0008] FIG. 1 is an explanatory diagram showing the configuration of a biasing force adjustment device (when the rollers are separated) according to an embodiment of the present invention, in which FIG. 1(a) is a schematic front view of the biasing force adjustment device, and FIG. 1(b) is a schematic top view of the biasing force adjustment device.

[0009] The biasing force adjuster 50 includes a side plate 51, a slider 52, an arm member 53, and a roller 54.

[0010] The side plate 51 forms the main body frame of the biasing force adjustment device 50 and holds the locking member 51a, the shaft 51b, and the shaft 51c. Of these, the locking member 51a and the shaft 51b each have one end fixed to the side plate 51. One end of the shaft 51c penetrates the side plate 51, and a power transmission mechanism (gear G in this embodiment) that transmits power from the drive motor M is provided at the portion where the shaft 51c penetrates the side plate 51. As described above, the side plate 51 is configured to include the locking member 51a and the shaft 51b that are fixed in fixed positions, and the shaft 51c that is supported in a rotatable manner at the fixed position.

[0011] Next, the configuration of the slider 52 will be described. The slider 52 is movable in the left-right direction (the direction of arrow A and the direction of arrow B) relative to the side plate 51, and includes an elongated hole 52a, locking members 52b and 52c, an elongated hole 52d, and shafts 52e and 52f. The elongated hole 52a is a through-hole formed along the movement direction (left-right direction) of the slider 52, and is designed so that the locking member 51a provided on the side plate 51 can enter the elongated hole 52a. This prevents interference between the slider 52 and the locking member 51a when the slider 52 moves left-right.

[0012] Locking members 52b and 52c have one end fixed to slider 52, and when slider 52 moves left or right, locking members 52b and 52c move together with slider 52. Similar to the above-described long hole 52a, elongated hole 52d is a through hole formed along the movement direction (left or right direction) of slider 52, and is designed so that shaft 51c provided on side plate 51 can enter long hole 52d. This prevents interference between slider 52 and shaft 51c when slider 52 moves left or right.

[0013] One end of shaft 52e is fixed to slider 52, and a rotating member 52g such as a ball bearing is attached to the other end of shaft 52e. Shaft 52f is attached to the side of slider 52 opposite the side on which shaft 52e is provided (the side facing side plate 51), and one end of shaft 52f is fixed to slider 52, and a rotating member 52h such as a ball bearing is attached to the other end of shaft 52f. Therefore, when slider 52 moves left or right, shafts 52e and 52f also move together with slider 52. As described above, slider 52 includes locking members 52b and 52c, shafts 52e and 52f, and elongated holes 52a and 52d, which are fixed in fixed positions, and is configured to be able to move left or right without interfering with locking member 51a and shafts 51b and 51c of side plate 51.

[0014] Next, the configuration of arm member 53 will be described. Arm member 53 is roughly L-shaped, and is supported near the bent part of the L by shaft 51b provided on side plate 51. This allows arm member 53 to rotate around shaft 51b as a fulcrum. Arm member 53 also has elongated hole 53a, locking portion 53b, and locking portion 53c.

[0015] The elongated hole 53a is a through-hole that allows the insertion of a locking member 52c provided on the slider 52. The locking member 52c comes into contact with the inner surface of the elongated hole 53a, thereby limiting the amount of rotation of the arm member 53. In this embodiment, when the roller 54 descends as shown in FIG. 1(a), the locking member 52c comes into contact with the lower left inner surface of the elongated hole 53a, thereby positioning the arm member 53.

[0016] The locking portion 53b is for locking one end of the spring 55, and in this embodiment, the locking portion 53b is formed by cutting out a part (the lower right part of the inner surface) of the elongated hole 53a to provide a step. The other end of the spring 55 is locked to a locking member 51a that protrudes from the side plate 51 through the elongated hole 52a of the slider 52. The locking portion 53c is for locking one end of the spring 56, and in this embodiment, the locking portion 53c is formed by providing a bent portion in a part (the lower end) of the arm member 53. The other end of the spring 56 is locked to a locking member 52b provided on the slider 52. The pair of arm members 53 support the roller 54 at their upper ends (tips).

[0017] As described above, arm member 53 includes elongated hole 53a and locking portions 53b and 53c. When the biasing force of spring 55, which is hooked between locking portion 53b and locking member 51a, and spring 56, which is hooked between locking portion 53c and locking member 52b, changes, arm member 53 rotates about shaft 51b as a fulcrum.

[0018] The biasing forces of springs 55 and 56 can be changed by switching the position of slider 52 using cams 57 and 58. Cams 57 and 58 are installed on shaft 51c held by side plate 51, and cam 57 has a cam surface that can come into contact with the outer peripheral surface of rotating member 52g provided on slider 52. Cam 58 has a cam surface that can come into contact with the outer peripheral surface of rotating member 52h provided on the side of slider 52 opposite the side on which rotating member 52g is provided (the side facing side plate 51).

[0019] 1, the outer peripheral surface of rotating member 52g is in contact with cam 57, restricting movement of slider 52 to the right (in the direction of arrow B). Springs 55 and 56 also pull arm member 53, urging it counterclockwise with shaft 51b as the fulcrum. However, locking member 52c abuts against the lower left inner surface of elongated hole 53a in arm member 53, preventing arm member 53 from moving further counterclockwise. This causes roller 54 to be spaced apart from moving body 200, which moves above roller 54, and from rotating body 100, which is positioned between moving body 200 and arm member 53.

[0020] In this embodiment, the biasing force of the springs 55 and 56 applied to the arm member 53 by the springs 55 and 56 is set to be greater than the biasing force of the spring 55. Furthermore, tension springs are used for the springs 55 and 56, which makes it possible to reduce error compared to compression springs.

[0021] In addition, in this embodiment, the drive motors M for driving the cams 57, 58 are provided on the front and rear sides, respectively, but this is not necessarily limited to this. For example, the shaft 51c may be long enough to straddle the front side plate 51 and the rear side plate 51, and the front cams 57, 58 and the rear cams 57, 58 may be attached to the single shaft 51c, and the front and rear cams 57, 58 may be driven by a single drive motor M.

[0022] Here, arm member 53 is an example of a "roller holding member," spring 55 is an example of a "first biasing member," and spring 56 is an example of a "second biasing member." Also, shaft 51b is an example of a "rotating shaft," slider 52 is an example of a "moving member," and cams 57 and 58 are examples of a "regulating member."

[0023] 2A and 2B are explanatory diagrams showing the configuration of a biasing force adjustment device (when the roller is in contact) according to an embodiment of the present invention, with Fig. 2A being a schematic front view of the biasing force adjustment device and Fig. 2B being a schematic top view of the biasing force adjustment device. Since the respective members are the same as those described in Fig. 1, the same reference numerals are used and the following description will be omitted.

[0024] When cam 57 rotates counterclockwise around shaft 51c as the rotation axis, the shape of the cam surface of cam 57 shortens distance X1 from shaft 51c to the contact position of rotating member 52g compared to when the rollers are separated as shown in FIG. 1(a). Then, slider 52 moves rightward (in the direction of arrow B) by the shortened distance X2. Furthermore, as slider 52 moves rightward, contact between elongated hole 53a of arm member 53 and locking member 52c of slider 52 is also released. Then, arm member 53 rotates counterclockwise around shaft 51b as the rotation axis due to the action of springs 55 and 56. As a result, roller 54 is in contact with moving body 200 and rotating body 100. Here, the contact state shown in FIG. 2 is an example of a "first contact position."

[0025] In this case, the roller 54 contacts the moving body 200 by applying only the biasing force (tensile force) of the spring 55 to the arm member 53, and the spring 56 is set to a free length state. This makes it possible to reduce the deviation of the biasing forces on the moving body 200 and the rotating body 100. Here, the biasing force applied by the spring 55 to the arm member 53 is an example of a "first biasing force."

[0026] 3A and 3B are explanatory diagrams showing the configuration of a biasing force adjustment device (when roller contact is intensified) according to an embodiment of the present invention, in which FIG. 3A is a schematic front view of the biasing force adjustment device, and FIG. 3B is a schematic top view of the biasing force adjustment device.

[0027] When cam 57 is further rotated counterclockwise from the state shown in FIG. 2, cam 57 is no longer in contact with rotating member 52g, and slider 52 moves further to the right (in the direction of arrow B) by a distance X3 from when roller 54 is in contact with rotating member 52g as shown in FIG. 2(a). Then, arm member 53 rotates counterclockwise around shaft 51b as the pivot axis due to the action of springs 55 and 56. Cams 57 and 58 further rotate counterclockwise, and cam 58, which is provided coaxially with cam 57, comes into contact with rotating member 52h, thereby restricting the movement of slider 52 to the right (in the direction of arrow B). This causes roller 54 to be in stronger contact with moving body 200 and rotating body 100 than in FIG. 2. The contact state shown in FIG. 3 is an example of a "second contact position."

[0028] In this case, the roller 54 contacts the moving body 200 by applying only the biasing force (tensile force) of the spring 56 to the arm member 53, and the spring 55 is set to a free length state. In this embodiment, the tensile force of the spring 56 is set to twice that of the spring 55. Here, the biasing force applied by the spring 56 to the arm member 53 is an example of a "second biasing force."

[0029] As described above, this embodiment comprises a roller 54 facing the moving body 200, an arm member 53 that holds the roller 54 and is displaceable relative to the moving body 200, a spring 55 that applies a first biasing force to the arm member 53, causing the roller 54 to abut against the moving body 200, and a spring 56 that applies a second biasing force greater than the first biasing force to the arm member 53, causing the roller 54 to abut against the moving body 200.

[0030] As described above, the arm member 53 includes the shaft 51b that rotatably supports the arm member 53, and the arm member 53 rotates around the shaft 51b as a fulcrum due to at least one of the first biasing force and the second biasing force.

[0031] This makes it possible to provide a biasing force adjusting device that can adjust the biasing force with a small error.

[0032] As described above, the spring 55 applies a first biasing force to the arm member 53, causing the moving body 200 to contact the roller 54 at the first contact position.

[0033] As described above, the spring 56 applies a second biasing force to the arm member 53, causing the moving body 200 to contact the roller 54 at a second contact position that is different from the first contact position.

[0034] As described above, the contact force between the moving body 200 and the roller 54 at the second contact position is set to be greater than the contact force between the moving body 200 and the roller 54 at the first contact position.

[0036] This makes it possible to reduce the deviation of the biasing forces on the moving body 200 and the rotating body 100.

[0037] Furthermore, as described above, the arm member 53, spring 55 and spring 56 work in conjunction with the movement of the slider 52, which is movable in a predetermined direction (left and right in this embodiment), to enable switching between a state in which the movable body 200 and the roller 54 are in contact with each other at the first contact position, a state in which the movable body 200 and the roller 54 are in contact with each other at the second contact position, and a state in which the roller 54 is separated from the movable body 200.

[0038] As described above, the slider 52 is provided with cams 57 and 58 that restrict the movement of the slider 52 in a predetermined direction.

[0039] As described above, the cams 57 and 58 are provided in plurality, and the cams 57 and 58 are provided coaxially and rotatably.

[0040] As a result, by moving the arm member 53 and the springs 55 and 56 together with the movement of the slider 52, the roller 54 can be switched accurately between the contact state, the contact reinforced state, and the separated state.

[0041] FIG. 4 is a schematic diagram showing an example of an image forming apparatus in which the biasing force adjusting device of the present invention is applied to a transfer device.

[0042] Printer 1000, which serves as an image forming apparatus according to this embodiment, includes four sets of image forming units that use toner of four colors (yellow (Y), cyan (C), magenta (M), and black (K)), for example. Below each image forming unit, an intermediate transfer belt 2 is provided as an intermediate transfer body for transferring the toner images formed by these image forming units. In other words, printer 1000 is a tandem-type image forming apparatus in which four sets of image forming units are arranged side by side along the movement direction of intermediate transfer belt 2. Note that these image forming units have the same configuration except for the color of the developer (toner), and therefore in the following explanation, the suffixes Y, C, M, and K in the reference numerals will be omitted as appropriate.

[0043] Each image forming unit includes a photosensitive drum 1 as an image carrier, and is surrounded by a charging device, an exposure device, a developing device, a photosensitive drum cleaning device, and other devices (not shown). The charging device charges the surface of each photosensitive drum 1. The exposure device exposes the charged surface of each photosensitive drum 1 to laser light based on image information read by an image scanner unit from a document transported from an ADF (Automatic Document Feeder), thereby forming a latent image on the surface of the photosensitive drum 1. Note that the image information is not limited to image information read by the image scanner unit, but may also be image information received from a PC (Personal Computer). The developing device visualizes the latent image formed on each photosensitive drum 1 as a toner image. The photosensitive drum cleaning device cleans the surface of each photosensitive drum 1.

[0044] The photosensitive drums 1 of the four image forming units are rotated in the direction of the arrows in the figure by a photosensitive drum drive device (not shown). Note that the black photosensitive drum 1K and the color photosensitive drums 1Y, 1C, and 1M may be driven to rotate independently. In this way, for example, when forming a monochrome image, only the black photosensitive drum 1K is driven to rotate, and when forming a color image, the four photosensitive drums 1Y, 1C, 1M, and 1K are driven to rotate simultaneously.

[0045] The intermediate transfer belt 2 is wound around multiple support rollers, including a secondary transfer opposing roller 5 and support rollers 3 and 7. The support roller 3 is a drive roller that is driven to rotate by a drive motor (not shown) to transport the intermediate transfer belt 2 counterclockwise in the drawing. On the other hand, the support roller 7 is a driven roller that rotates in conjunction with the movement of the intermediate transfer belt 2. Roller 6 is a tension roller that contacts the outer circumferential surface of the intermediate transfer belt 2.

[0046] At the primary transfer position where a toner image is transferred from each photosensitive drum 1 to the intermediate transfer belt 2, a primary transfer roller 24 is provided facing each photosensitive drum 1 with the intermediate transfer belt 2 sandwiched therebetween. The primary transfer roller 24 is equipped with a contact / separation mechanism so that it is separated from the color photosensitive drums 1Y, 1C, and 1M when a monochrome image is formed, and is separated from all the photosensitive drums when image formation itself is not performed.

[0047] The intermediate transfer belt 2 is pressed against the photosensitive drum 1 by the contact of the primary transfer roller 24, forming a primary transfer nip at the opposing portion with each photosensitive drum 1. A secondary transfer roller 8 is disposed below the intermediate transfer belt 2 in the drawing, and forms a secondary transfer nip by contacting the secondary transfer opposing roller 5 via the intermediate transfer belt 2. A secondary transfer unit 10 having the secondary transfer roller 8 has a rotation shaft 43 on the downstream side in the running direction of the intermediate transfer belt 2, and is configured to be rotatable around the rotation shaft 43 as a fulcrum.

[0048] The secondary transfer roller 8 is arranged to be pressed against the secondary transfer opposing roller 5 via the intermediate transfer belt 2 by the tension spring load of the secondary transfer pressure spring. Then, the image on the intermediate transfer belt 2 is transferred to the paper P by the pressure of the secondary transfer roller 8 and a transfer bias (not shown). On the downstream side of the secondary transfer unit 10 in the paper transport direction, there is provided a transport belt 11 that transports the paper P toward a fixing device 15, and further downstream therefrom there is provided a fixing device 15 that fixes the unfixed image transferred onto the paper P.

[0049] The fixing device 15 is configured by pressing a pressure roller 12 against a fixing belt stretched between a fixing roller 13 and a heating roller 14. The fixing belt is heated by an induction coil (not shown) inside the heating roller 14 to the temperature required for image fixing. Meanwhile, the pressure roller 12 also has a built-in heater (not shown) that is used for preheating during standby. Heat and pressure are applied to an unfixed image on the paper P at the nip between the fixing belt and the pressure roller 12, thereby fixing the unfixed image to the paper P. The heater of the fixing device 15 is not limited to an induction coil. For example, a system configured with a pair of heating rollers may also be used.

[0050] The image formation (printing) operation of the printer 1000 configured as described above will now be briefly described. When forming a color image, each photosensitive drum 1 rotates in the direction of the arrow in the figure, and at this time, a charging device charges the surface of each photosensitive drum 1 to a predetermined polarity, for example, a negative polarity. Next, an optically modulated laser beam emitted from an exposure device is irradiated onto the charged surface of each photosensitive drum 1, thereby forming an electrostatic latent image on the surface of each photosensitive drum 1. That is, the portions of the photosensitive surface irradiated with the laser beam and having a lower absolute value of potential become the electrostatic latent image (image area), while the portions not irradiated with the laser beam and having a higher absolute value of potential become the background area. Next, the electrostatic latent image is developed into a toner image using toner charged to a predetermined polarity contained in a developing device.

[0051] The toner images formed on the photosensitive drums 1 are transferred onto the intermediate transfer belt 2 in a sequentially overlapping manner due to the action of a transfer electric field formed on the primary transfer roller 24 and the nipping pressure between the primary transfer roller 24 and the photosensitive drums 1 via the intermediate transfer belt 2. In this way, a full-color toner image consisting of four color toner images is formed on the intermediate transfer belt 2. Residual toner remaining on the photosensitive drums 1 without being transferred to the intermediate transfer belt 2 is removed by a photosensitive cleaning device, which cleans the surfaces of each photosensitive drum 1. The toner removed from the photosensitive drums 1 may be transported to a developing device using a toner recycling device (not shown) for toner recycling.

[0052] Meanwhile, paper feed rollers 18 rotate, and separation rollers 17 separate the paper sheets P fed out from paper feed cassette 20 one by one. Then, transport rollers 16 transport the separated paper sheets P between intermediate transfer belt 2 and secondary transfer rollers 8 at a predetermined timing. The paper sheets P transported by transport rollers 16 hit registration rollers (alignment rollers) 9 and stop. Alternatively, paper sheets P transported from a manual feed tray (manual feed section) (not shown) via a manual feed path also hit registration rollers 9 and stop. The registration rollers 9 rotate in synchronization with the full-color toner image on intermediate transfer belt 2, and feed the paper sheets P into a secondary transfer nip formed between secondary transfer roller 8 and secondary transfer opposing roller 5. The full-color toner image is then transferred to the paper sheets P at the secondary transfer nip.

[0053] The fixing device 15 applies heat and pressure to the paper P carrying the full-color toner image, fixing the toner image to the paper, and then discharges the paper P to a paper output tray (not shown). Alternatively, a double-sided reversing mechanism (not shown) guides the paper P back to the transfer position again, records an image on the back side, and discharges the paper to the paper output tray after fixing.

[0054] 1 to 3 is mounted in this image forming apparatus as a transfer device 50 including a primary transfer roller 24. That is, the roller 54 shown in FIGS. 1 to 3 is replaced with the primary transfer roller 24, the moving body 200 with the intermediate transfer belt 2, and the rotating body 100 with the photosensitive drum 1.

[0055] In this embodiment, the transfer device 50A for black has a configuration equivalent to the biasing force adjustment device 50 described with reference to Figures 1 to 3, and is provided independently from the transfer devices 50B for the other colors. On the other hand, the transfer devices 50B for the colors other than black are configured such that a single slider 52B holds three primary transfer rollers 24Y, 24C, and 24M. In other words, the primary transfer rollers 24Y, 24C, and 24M are simultaneously moved toward and away from the photosensitive drums 1Y, 1C, and 1M by moving the slider 52B left and right.

[0056] As a result, when forming a monochrome image, for example, it is possible to contact the primary transfer roller 24K only with the photosensitive drum 1K via the intermediate transfer belt 2. Furthermore, in the color transfer device 50B, the number of parts such as the slider 52B and the cams 57B and 58B is reduced, simplifying the configuration and reducing the installation space for the color transfer device, thereby enabling the image forming apparatus to be made more compact. Note that the color transfer device 50B is not limited to the configuration of this embodiment. For example, similar to the black transfer device 50A, it may be mounted as separate transfer devices for yellow, magenta, and cyan.

[0057] In the image forming apparatus of this embodiment, the three states (roller separation, roller contact, and roller contact intensification) described with reference to FIGS. 1 to 3 are used as the following modes.

[0058] The state in which the primary transfer roller 24 is separated from the intermediate transfer belt 2 is the state in the "separation mode." For example, the separation mode occurs when no image is being formed, when no toner image is being transferred from the photosensitive drum 1 to the intermediate transfer belt 2, when the image forming apparatus is turned off, and during a power-off period. The separation mode also occurs, for example, after the image forming apparatus is turned on from an off state and before image formation.

[0059] The state in which the primary transfer roller 24 is in contact with the intermediate transfer belt 2 is the state in the "contact mode," and for example, the contact mode occurs when the primary transfer roller 24 presses against the intermediate transfer belt 2 to form an image.

[0060] The state in which the contact of the primary transfer roller 24 with the intermediate transfer belt 2 is strengthened is the state in the "shock jitter countermeasure mode." For example, the shock jitter countermeasure mode is used when it is desired to suppress shock jitter that occurs when a highly rigid sheet of paper P enters the nip position of the secondary transfer roller 8.

[0061] In this embodiment, the cams 57A, 58A (57B, 58B) come into contact with (or separate from) the rotating members 52gA, 52hA (52gB, 52hB), causing the slider 52A (52B) to move left and right. As the slider 52A (52B) moves, the springs 55A, 56A (55B, 56B) engaged with the slider 52A (52B) expand and contract. The tension of the springs 55A, 56A (55B, 56B) can be varied by the rotation angle of the cams 57A, 58A (57B, 58B), allowing multiple mode settings.

[0062] In this embodiment, the cams 57A, 58A (57B, 58B) are configured so that in the contact mode, tension is applied only to the spring 55A (55B), and the spring 56A (56B) is at its free length. This contact mode state is set as the default value for the tension of the intermediate transfer belt 2. This makes it possible to reduce deviations in the tension of the intermediate transfer belt 2 in the normally used contact mode.

[0063] Furthermore, if shock jitter occurs in the default value (contact mode), the cams 57A, 58A (57B, 58B) are rotated to move the slider 52A (52B) to the right. The spring 56A (56B) linked to the slider 52A (52B) is then pulled, causing the arm member 53A (53B) to rotate counterclockwise, and the primary transfer roller 24 contacts the intermediate transfer belt 2 with greater force. This reduces the impact on the intermediate transfer belt 2 of the shock that occurs when a highly rigid sheet of paper P enters the nip position of the secondary transfer roller 8. Furthermore, tension springs are used for the springs 55A, 56A (55B, 56B), which reduces error compared to compression springs.

[0064] FIG. 5 is an explanatory diagram showing an example of a toner used in an image forming apparatus according to an embodiment of the present invention, where FIG. 5(a) is an explanatory diagram of the shape factor SF1, and FIG. 5(b) is an explanatory diagram showing a schematic representation of the shape of the toner to explain the shape factor SF2.

[0065] The shape factor SF1 of the toner used in this embodiment is preferably in the range of 100 to 180, and the shape factor SF2 is preferably in the range of 100 to 180. The shape factor SF1 indicates the roundness of the toner shape, and can be expressed by formula (1). The shape factor SF1 is the square of the maximum length MXLNG of the shape formed when the toner is projected onto a two-dimensional plane, divided by the geometric area AREA, and multiplied by 100π / 4. SF1=((MXLNG)2 / AREA)×(π / 4)×100...Equation (1) When the value of SF1 is 100, the toner particle has a spherical shape, and as the value of SF1 increases, the toner particle becomes more irregular in shape.

[0066] The shape factor SF2 indicates the proportion of unevenness in the toner shape, and can be expressed by formula (2): The shape factor SF2 is the square of the perimeter PERI of the shape created by projecting the toner onto a two-dimensional plane, divided by the area AREA of the shape, and multiplied by 100π / 4. SF2=((PERI)2 / AREA)×(1 / 4π)×100...Equation (2) When the value of SF2 is 100, there are no irregularities on the toner surface, and as the value of SF2 increases, the irregularities on the toner surface become more pronounced.

[0067] Specifically, the shape factor was measured by taking a photograph of the toner with a scanning electron microscope (S-800, manufactured by Hitachi), which was then input into an image analyzer (LUSEX3, manufactured by Nireco Corporation) for analysis and calculation. When the shape of the toner becomes closer to a sphere, the contact state between the toner particles or between the toner and the photosensitive drum becomes point contact, weakening the adhesive force between the toner particles and increasing fluidity, which also weakens the adhesive force between the toner and the photosensitive drum and increasing the transfer rate. If either of the shape factors SF1 or SF2 exceeds 180, the transfer rate decreases and cleaning ability in the event of adhesion to the transfer means also decreases, which is undesirable.

[0068] Furthermore, the toner particle size is preferably in the range of 4 to 10 μm in terms of volume average particle size. If the particle size is smaller than this, background smearing occurs during development, and the fluidity deteriorates, making it more likely to aggregate, resulting in hollow areas. Conversely, if the particle size is larger than this, the toner scatters, and resolution deteriorates, making it impossible to obtain high-definition images. Taking these factors into consideration, toner with a volume average particle size of 6.5 μm was used in this embodiment.

[0069] FIG. 6 is a setting flow diagram for the shock jitter handling mode in the image forming apparatus according to the embodiment of the present invention.

[0070] When setting the shock jitter response mode, first, a test print is made for each thickness of paper used in the printer 1000 (step S1). In the test print, it is checked whether horizontal stripes appear in the image formed on the paper P. If horizontal stripes appear in the image, this means that shock jitter has occurred due to the highly rigid paper P entering the nip position of the secondary transfer roller 8 of the printer 1000.

[0071] If horizontal stripes appear in the test print image, the user sets the transfer device 50 mode to "shock jitter compatible mode" when using the paper P on which the horizontal stripes appear, using the operation panel of the printer 1000 or the like (step S2). The compatible mode setting for each paper thickness is stored in a memory or the like provided in the printer 1000.

[0072] FIG. 7 is an execution flow diagram of the shock jitter handling mode in the image forming apparatus according to the embodiment of the present invention.

[0073] When the printer 1000 starts a printing operation, the printer 1000 acquires printing information (image information, paper type information, etc.) from a controller (not shown) (step S71). Next, it is determined based on the printing information acquired in step S71 whether the paper P to be used is paper for which the shock jitter responsive mode has been set in the setting flow described above (step S72). If it is determined in step S72 that the shock jitter responsive mode has not been set, the primary transfer roller 24 of the transfer device 50 abuts against the intermediate transfer belt 2 in the "contact mode" (step S73).

[0074] On the other hand, if it is determined in step S72 that the shock jitter responsive mode is set, the primary transfer roller 24 of the transfer device 50 contacts the intermediate transfer belt 2 in the "shock jitter responsive mode" (step S74). Image formation is performed in the contact mode or the shock jitter responsive mode, and once the paper P passes the nip position between the intermediate transfer belt 2 and the secondary transfer roller 8 (step S75), it is determined whether or not there is a subsequent paper (step S76). If it is determined in step S76 that there is no subsequent paper after the paper P, the primary transfer roller 24 of the transfer device 50 enters the "separation mode" with respect to the intermediate transfer belt 2 (step S77), and the printing operation ends. If it is determined in step S76 that there is a subsequent paper, the current mode (contact mode or shock jitter responsive mode) is maintained and printing on the subsequent paper continues until there is no subsequent paper (step S78).

[0075] In this way, by not changing the mode when there is a subsequent sheet of paper, it is possible to prevent image distortion, for example, during the primary transfer of an image from the photosensitive drum 1 to the intermediate transfer belt 2 to be transferred to the next subsequent sheet of paper. Even if the "shock jitter responsive mode" is determined in step S72, if, for example, there is only one sheet of paper to be printed, the printing operation may be performed in the "contact mode" rather than the "shock jitter responsive mode." Shock jitter is a phenomenon in which the impact (vibration) caused by a highly rigid sheet of paper P entering the nip position of the secondary transfer roller 8 is transmitted to the intermediate transfer belt 2, resulting in horizontal stripes on the image to be transferred to the next subsequent sheet of paper. Therefore, when there is only one sheet of paper to be printed, there is no need to consider the transferability to the subsequent sheet of paper.

[0076] 8 is an execution flow diagram of a modified example of the shock jitter response mode in the image forming apparatus according to the embodiment of the present invention. Steps S81 to S87 of this modified example are equivalent to steps S71 to S77 of the execution flow shown in FIG. 7, so a description of each step will be omitted.

[0077] This modified example differs from the execution flow in FIG. 7 in that if it is determined in step S86 that a subsequent sheet is present, the flow returns to step S82 (determining the setting status of the shock jitter response mode). That is, in this modified example, it is determined each time whether the subsequent sheet is in shock jitter response mode, and after the determination, formation of an image to be transferred to the subsequent sheet begins. In shock jitter response mode, the state in which the primary transfer roller 24 is in strong contact with the intermediate transfer belt 2 results in less favorable transferability than in contact mode, so for sheets that do not produce horizontal stripes, it is desirable to use contact mode. By determining whether the shock jitter response mode is in effect for each sheet as in this modified example, it becomes possible to transfer an image that is appropriate for each sheet.

[0078] In this embodiment, the biasing force adjustment device has been described as being applied to a transfer device of an image forming apparatus, but the application is not limited to this. For example, the biasing force adjustment device can be applied to devices that have rollers that come into contact with an endless belt-like or long moving body, such as a conveying device that has a conveying belt that conveys recording media such as paper, or a fixing device that has a fixing belt.

[0079] The above description is merely an example, and the present invention provides unique effects for each of the following aspects.

[0080] The first aspect is characterized by comprising a roller (e.g., roller 54) facing a moving body (e.g., moving body 200), a roller holding member (e.g., arm member 53) that holds the roller and is displaceable relative to the moving body, a first biasing member (e.g., spring 55) that applies a first biasing force to the roller holding member to bring the roller into contact with the moving body, and a second biasing member (e.g., spring 56) that applies a second biasing force greater than the first biasing force to the roller holding member to bring the roller into contact with the moving body.

[0081] The second aspect is characterized in that, in the first aspect, the roller holding member (e.g., arm member 53) is provided with a rotating shaft (e.g., shaft 51b) that rotatably supports the roller holding member, and the roller holding member rotates around the rotating shaft as a fulcrum due to at least one of the first spring force and the second spring force.

[0082] According to the first and second aspects, it is possible to provide a biasing force adjustment device that is capable of adjusting the biasing force with a small error.

[0083] The third aspect is characterized in that, in the first or second aspect, the first biasing member (e.g., spring 55) applies the first biasing force to the roller holding member (e.g., arm member 53), thereby forming a contact between the moving body (e.g., moving body 200) and the roller (e.g., roller 54) at a first contact position.

[0084] The fourth aspect is characterized in that, in any of the first to third aspects, the second biasing member (e.g., spring 56) applies the second biasing force to the roller holding member (e.g., arm member 53), thereby forming a contact between the movable body (e.g., movable body 200) and the roller (e.g., roller 54) at a second contact position different from the first contact position.

[0085] The fifth aspect is characterized in that, in the third or fourth aspect, the contact force between the moving body (e.g., moving body 200) and the roller (e.g., roller 54) at the second contact position is specified to be greater than the contact force between the moving body and the roller at the first contact position.

[0086] The sixth aspect is characterized in that, in any of the first to fifth aspects, when the first and second spring forces are not applied to the roller holding member (e.g., arm member 53), the roller (e.g., roller 54) is spaced apart from the moving body (e.g., moving body 200).

[0087] According to the third to sixth aspects, it is possible to reduce the deviation of the biasing force on the moving body.

[0088] The seventh aspect is characterized in that, in any of the first to sixth aspects, the roller holding member (e.g., arm member 53), the first biasing member (e.g., spring 55), and the second biasing member (e.g., spring 56) work in conjunction with the movement of a movable member (e.g., slider 52) that is movable in a predetermined direction, to enable switching between a state in which the movable body (e.g., movable body 200) and the roller (e.g., roller 54) are in contact at the first contact position, a state in which the movable body and the roller are in contact at the second contact position, and a state in which the roller is separated from the movable body.

[0089] The eighth aspect is characterized in that in the seventh aspect, the moving member (for example, slider 52) includes a regulating member (for example, cams 57, 58) that regulates the movement of the moving member in the predetermined direction.

[0090] The ninth aspect is characterized in that in the eighth aspect, a plurality of the regulating members (for example, cams 57, 58) are provided, and the plurality of regulating members are provided rotatably on the same axis (for example, shaft 51c).

[0091] According to the seventh to ninth aspects, by moving the roller holding member, the first biasing member and the second biasing member together with the movement of the movable member, the roller can be switched accurately between a contact state, a contact-intensified state and a separated state. [Explanation of symbols]

[0092] 50 Force adjustment device 51 Side panel 51a Locking member 51b axis (an example of a rotating axis) 51c axis 52 Slider (an example of a moving part) 52a long hole 52b Locking member 52c Locking member 52d long hole 52e axis 52f axis 52g rotating member 52h Rotating member 53 Arm member (an example of a roller holding member) 53a long hole 53b Locking part 53c Locking part 54 Laura 55 spring (an example of a first biasing member) 56 Spring (an example of a second biasing member) 57 Cam (an example of a regulating member) 58 Cam (an example of a regulating member) 100 Rotating Body 200 Mobile M drive motor G Gear [Prior art documents] [Patent documents]

[0093] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-060030

Claims

1. a roller facing the moving body; a roller holding member that holds the roller and is displaceable relative to the moving body; a first biasing member that applies a first biasing force to the roller holding member to cause the roller to contact the moving body at a first contact position; a second biasing member that applies a second biasing force greater than the first biasing force to the roller holding member to cause the roller to contact the moving body at a second contact position; Equipped with when the roller is brought into contact with the moving body at the first contact position, only the first biasing force of the first biasing member is applied to the roller holding member; when the roller is brought into contact with the movable body at the second contact position, only the second biasing force of the second biasing member is applied to the roller holding member; a biasing force adjusting device that applies both the first biasing force and the second biasing force to the roller holding member when the roller is separated from the moving body;

2. 2. The biasing force adjusting device according to claim 1, wherein the roller holding member is supported by a pivot shaft that allows the roller holding member to rotate, and the roller holding member rotates around the pivot shaft as a fulcrum due to at least one of the first biasing force and the second biasing force.

3. 3. The biasing force adjusting device according to claim 1, wherein the contact force between the movable body and the roller at the second contact position is set to be greater than the contact force between the movable body and the roller at the first contact position.

4. A roller facing a moving body; a roller holding member that holds the roller and is displaceable relative to the moving body; a first biasing member that applies a first biasing force to the roller holding member to cause the roller to contact the moving body at a first contact position; a second biasing member that applies a second biasing force greater than the first biasing force to the roller holding member to cause the roller to contact the moving body at a second contact position; Equipped with when the roller is brought into contact with the moving body at the first contact position, only the first biasing force of the first biasing member is applied to the roller holding member; when the roller is brought into contact with the movable body at the second contact position, only the second biasing force of the second biasing member is applied to the roller holding member; The roller holding member, the first biasing member, and the second biasing member are interlocked with the movement of a movable member that is movable in a predetermined direction, a state in which the movable body and the roller are in contact with each other at the first contact position; a state in which the movable body and the roller are in contact with each other at the second contact position; and The roller is separated from the moving body. A biasing force adjusting device characterized by being capable of switching between the above.

5. A force adjustment device as described in claim 4, characterized in that the movement of the moving member in the specified direction is restricted by a restricting member.

6. A force adjusting device as described in claim 5, characterized in that it is provided with a plurality of regulating members, and the plurality of regulating members are arranged to be rotatable coaxially.

7. A transfer device characterized in that the moving body is a transfer belt and is equipped with a force adjustment device described in any one of claims 1 to 6.

8. An image forming apparatus characterized by comprising the transfer device described in claim 7.

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