Image forming device

Abstract

To provide an image formation device in a configuration capable of suppressing deterioration in image quality of an image transferred to a recording medium.SOLUTION: An image formation device 10 includes: a transfer cylinder 46 on which an image is transferred onto a paper sheet passing on a surface on an outer side in a rotation diameter direction; and a fixing cylinder 56 on which the image transferred onto the paper sheet passing on the surface on the outer side in the rotation diameter direction is fixed on the paper sheet. Further, the image formation device 10 includes: a chain 20 that is formed in an annular shape, and stretched between at least the transfer cylinder 46 and the fixing cylinder 56 to revolve along with rotation of the transfer cylinder 46 and the fixing cylinder 56; and a gripper 18 that is supported by the chain 20 and holds the paper. Further, the image formation device 10 includes: a first drive unit 68 that rotates the transfer cylinder 46; and a second drive unit 70 that rotates the fixing cylinder 56, wherein a ratio of inertia moment of the fixing cylinder 56 with respect to output torque of the second drive unit is set larger than a ratio of inertia moment of the transfer cylinder 46 with respect to the output torque of the first drive unit 68.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] Patent Document 1 below discloses an image forming apparatus. The image forming apparatus described in this document includes a transfer section including a circular transfer belt on the outer surface of which an image is transferred, a transfer cylinder having a transfer area where a recording medium is sandwiched between the outer surface of the transfer belt and the transfer cylinder to transfer the image from the transfer belt to the recording medium, and a rotor disposed on both axial ends of the transfer cylinder. The image forming apparatus also includes a rotating member that is wrapped around the rotor and rotates with the rotation of the rotor, and a holding section that is attached to the rotating member, holds the recording medium, and conveys the recording medium by the rotation of the rotating member to pass through the transfer area. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-140062 A Summary of the Invention [Problem to be solved by the invention]

[0004] When an image is being transferred onto a recording medium, if vibrations generated on the fixing cylinder side are transmitted to the transfer cylinder side, the quality of the image transferred onto the recording medium may be impaired.

[0005] Taking into consideration the above facts, the present invention aims to obtain an image forming device that can suppress deterioration of the image quality of the image transferred to a recording medium, compared to a configuration in which the ratio of the moment of inertia of the fixing cylinder to the output torque of the second drive unit is equal to the ratio of the moment of inertia of the transfer cylinder to the output torque of the first drive unit. [Means for solving the problem]

[0006] The image forming apparatus of the first aspect includes a transfer cylinder that is rotatably supported and has a first groove portion formed in a radially outer portion thereof, where an image is transferred to a recording medium passing over its radially outer surface; a fixing cylinder that is rotatably supported and has a second groove portion formed in a radially outer portion thereof, where the image transferred to the recording medium passing over its radially outer surface is fixed to the recording medium; a rotating member that is formed in an annular shape and is stretched across at least the transfer cylinder and the fixing cylinder, and rotates as the transfer cylinder and the fixing cylinder rotate; a gripping member that is supported by the rotating member and grips the recording medium, and is disposed in the first groove portion when passing through the radially outer portion of the transfer cylinder, and is disposed in the second groove portion when passing through the radially outer portion of the fixing cylinder; a first drive unit that rotates the transfer cylinder; and a second drive unit that rotates the fixing cylinder, where a ratio of the moment of inertia of the fixing cylinder to its output torque is set to be greater than a ratio of the moment of inertia of the transfer cylinder to the output torque of the first drive unit.

[0007] In the image forming apparatus of the second aspect, in the image forming apparatus of the first aspect, the moment of inertia of the fixing cylinder is set to be larger than the moment of inertia of the transfer cylinder.

[0008] An image forming apparatus of a third aspect includes a transfer cylinder that is rotatably supported and has a first groove portion formed in its radially outer portion, where an image is transferred to a recording medium passing over its radially outer surface; a fixing cylinder that is rotatably supported and has a second groove portion formed in its radially outer portion, where the image transferred to the recording medium passing over its radially outer surface is fixed to the recording medium, and has a mass greater than that of the transfer cylinder; a rotating member that is formed in an annular shape and is stretched between at least the transfer cylinder and the fixing cylinder, and rotates as the transfer cylinder and the fixing cylinder rotate; a gripping member that is supported by the rotating member, grips the recording medium, is positioned in the first groove portion when passing over the radially outer portion of the transfer cylinder, and is positioned in the second groove portion when passing over the radially outer portion of the fixing cylinder; a first drive unit that rotates the transfer cylinder; and a second drive unit that rotates the fixing cylinder.

[0009] The image forming apparatus of a fourth aspect is the image forming apparatus of the third aspect, wherein the mass of the transfer cylinder is 30 kg or less, and the mass of the fixing cylinder is 50 kg or more.

[0010] An image forming apparatus according to a fifth aspect is the image forming apparatus according to the fourth aspect, wherein the mass of the transfer cylinder is 20 kg or less, and the mass of the fixing cylinder is 60 kg or more.

[0011] An image forming apparatus of a sixth aspect is an image forming apparatus of any one of the first to fifth aspects, further comprising a photosensitive member that is rotatably supported and on whose radially outer surface a toner image is formed, and a transfer belt that is annular and rotates in one direction, the toner image being transferred onto the transfer belt as the photosensitive member rotates on its outer peripheral surface, and the mass of the photosensitive member is set to be smaller than the mass of the fixing drum.

[0012] The image forming apparatus of a seventh aspect is the image forming apparatus of the sixth aspect, wherein the mass of the photoconductor is smaller than the mass of the transfer cylinder.

[0013] An image forming apparatus of an eighth aspect is an image forming apparatus of any one of the first to seventh aspects, wherein the rated output of the first drive unit and the rated output of the second drive unit are the same rated output.

[0014] An image forming apparatus of a ninth aspect is an image forming apparatus of any one of the first to eighth aspects, in which the ratio of the mass of the fixing cylinder to the output torque of the second drive unit is set to be greater than the ratio of the mass of the transfer cylinder to the output torque of the first drive unit. Effect of the Invention

[0015] In the image forming apparatus of the first aspect, degradation of the image quality of the image transferred to the recording medium can be suppressed compared to a configuration in which the ratio of the moment of inertia of the fixing cylinder to the output torque of the second drive unit is equal to the ratio of the moment of inertia of the transfer cylinder to the output torque of the first drive unit.

[0016] In the image forming apparatus of the second aspect, degradation of the image quality of the image transferred to the recording medium can be suppressed compared to a configuration in which the moment of inertia of the fixing cylinder and the moment of inertia of the transfer cylinder are set to be the same or a configuration in which the moment of inertia of the fixing cylinder is set to be smaller than the moment of inertia of the transfer cylinder.

[0017] In the image forming apparatus of the third aspect, degradation of the image quality of the image transferred to the recording medium can be suppressed compared to a configuration in which the mass of the transfer cylinder and the mass of the fixing cylinder are set to the same mass.

[0018] In the image forming apparatus of the fourth aspect, it is possible to suppress degradation of the image quality of the image transferred to the recording medium, compared to a configuration in which the mass of the transfer cylinder and the mass of the fixing cylinder are set outside the above range.

[0019] In the image forming apparatus of the fifth aspect, it is possible to suppress degradation of the image quality of the image transferred to the recording medium, compared to a configuration in which the mass of the transfer cylinder and the mass of the fixing cylinder are set outside the above range.

[0020] In the image forming apparatus of the sixth aspect, misalignment of the toner image transferred to the transfer belt can be suppressed compared to a configuration in which the mass of the photosensitive body is set to the same mass as or greater than the mass of the fixing cylinder.

[0021] In the image forming apparatus of the seventh aspect, misalignment of the toner image transferred to the transfer belt can be suppressed compared to a configuration in which the mass of the photosensitive body is set to the same mass as or greater than the mass of the transfer cylinder.

[0022] In the image forming apparatus of the eighth aspect, the first and second driving sections having the same rated output can be used.

[0023] In the image forming apparatus of the ninth aspect, degradation of the image quality of the image transferred to the recording medium can be suppressed compared to a configuration in which the ratio of the mass of the fixing cylinder to the output torque of the second drive unit is set to be the same as the ratio of the mass of the transfer cylinder to the output torque of the first drive unit, or a configuration in which the ratio of the mass of the fixing cylinder to the output torque of the second drive unit is set to be smaller than the ratio of the mass of the transfer cylinder to the output torque of the first drive unit. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a front view showing a schematic configuration of an image forming apparatus; [Diagram 2] 2 is an enlarged front view showing a part of the image forming apparatus shown in FIG. 1. [Diagram 3] 11 is a graph showing the speed fluctuation of a fixing cylinder when the fixing cylinder is lighter than the transfer cylinder. [Figure 4] 11 is a graph showing torque fluctuations of a transfer cylinder when a fixing cylinder is lighter than a transfer cylinder. [Diagram 5] 11 is a graph showing the speed fluctuation of the fixing cylinder when the fixing cylinder is heavy relative to the transfer cylinder. [Figure 6] 11 is a graph showing torque fluctuations of a transfer cylinder when a fixing cylinder is heavy relative to the transfer cylinder. [Figure 7] 11 is a graph showing the speed fluctuation of the transfer cylinder when the fixing cylinder is lighter than the transfer cylinder. [Figure 8] 11 is a graph showing the speed fluctuation of the transfer cylinder when the fixing cylinder is heavy relative to the transfer cylinder. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.

[0026] (Image forming apparatus 10) First, the configuration of the image forming apparatus 10 will be described. FIG. 1 is a front view showing a schematic configuration of the image forming apparatus 10 according to the present embodiment. The arrow UP shown in each figure indicates the vertical upper side, that is, the upper side of the apparatus. The arrow RH, as shown in FIG. 1, indicates one side in the horizontal direction, that is, the right side when facing the apparatus. In the following description, when the up-down direction is specified without any premise, it means the up-down direction of the apparatus shown in FIG. 1. In the following description, when the left-right direction is specified without any premise, it means the left-right direction when facing the apparatus shown in FIG. 1. In addition, in the following description, when the front-rear direction is specified without any premise, it means the front-rear direction when facing the apparatus shown in FIG. 1 (i.e., the direction toward the front and rear of the paper).

[0027] The image forming apparatus 10 is an electrophotographic image forming apparatus that forms a toner image on paper. Note that paper is an example of a recording medium, and a toner image is an example of an image. Specifically, the image forming apparatus 10 includes a conveying unit 12, an image forming unit 14, and a fixing unit 16.

[0028] (Transport section 12) The transport section 12 has a function of transporting paper. Specifically, the transport section 12 has a gripper 18 that grips the leading end of the paper in the transport direction, and a pair of chains 20. The gripper 18 is an example of a gripping member. The pair of chains 20 is an example of a circulating member, and is formed in a ring shape. The pair of chains 20 are arranged with a gap in the front-rear direction. Note that FIG. 1 illustrates the chain 20 of the pair of chains 20 that is arranged on the front side. Also, FIG. 1 illustrates the chain 20 and the gripper 18 in a simplified manner.

[0029] Each of the pair of chains 20 is stretched between the transfer cylinder 46, the fixing cylinder 56, the first intermediate shaft portion 60, and the second intermediate shaft portion 63, which will be described later. More specifically, each of the pair of chains 20 is wound around a pair of sprockets (not shown) that are respectively disposed on one and the other axial ends of the transfer cylinder 46, the fixing cylinder 56, the first intermediate shaft portion 60, and the second intermediate shaft portion 63, which will be described later. This allows the transfer cylinder 46, the fixing cylinder 56, the first intermediate shaft portion 60, and the second intermediate shaft portion 63 to rotate synchronously with one another.

[0030] In the transport section 12, a gripper 18 grips the leading edge of the paper sent from a storage section (not shown). In the transport section 12, while the gripper 18 grips the leading edge of the paper, the chain 20 rotates in the direction of arrow G to transport the paper and pass an opposing position 54 (i.e., the secondary transfer position) described below. In the transport section 12, the gripper 18 transports the paper to the fixing section 16 after passing the opposing position 54 (i.e., the secondary transfer position).

[0031] (Image forming unit 14) The image forming unit 14 has a function of forming an image on a sheet of paper. Specifically, the image forming unit 14 has a toner image forming unit 28 that forms a toner image by an electrophotographic method, and a transfer unit 30 that transfers the toner image formed by the toner image forming unit 28 onto a sheet of paper.

[0032] (Toner image forming unit 28) A plurality of toner image forming units 28 are provided so as to form toner images for each color. In this embodiment, toner image forming units 28 are provided for a total of four colors: yellow (Y), magenta (M), cyan (C), and black (K). The reference characters (Y), (M), (C), and (K) shown in FIG. 1 indicate components corresponding to the above-mentioned respective colors. Moreover, the toner image forming units 28 for each color are configured in the same manner except for the toner used, and therefore, in FIG. 1, reference characters are given to the respective elements constituting the toner image forming unit 28(Y) as a representative of the toner image forming units 28 for each color.

[0033] The toner image forming unit 28 for each color includes a rotating cylindrical photoconductor 32 and a charger 34 for charging the photoconductor 32. The toner image forming unit 28 further includes an exposure unit 36 ​​for irradiating the charged photoconductor 32 with light for exposure to form an electrostatic latent image, and a development unit 38 for developing the electrostatic latent image into an image formed by a toner layer using a developer containing toner. The toner image forming unit 28 further includes a cleaner 40 for removing toner remaining on the surface of the photoconductor 32 after the toner is transferred from the photoconductor 32 to a transfer belt 42.

[0034] (Transfer unit 30) The transfer unit 30 has a function of primarily transferring the toner images of the photoconductors 32 of each color onto the transfer belt 42 in a superimposed manner as the photoconductors 32 rotate on the transfer belt 42, and then secondarily transferring the superimposed toner images onto paper. Specifically, the transfer unit 30 includes the transfer belt 42 as an intermediate transfer body, a primary transfer roll 44, a transfer cylinder 46, and a secondary transfer roll 48 (an example of a transfer roll).

[0035] The primary transfer roll 44 has the function of transferring the toner image formed on the photoreceptor 32 onto the outer peripheral surface of the transfer belt 42 at a primary transfer position 50 between the photoreceptor 32 and the primary transfer roll 44.

[0036] The transfer belt 42 is endless (i.e., circular), and is supported and its posture is determined by being wound around the secondary transfer roll 48 and the multiple rolls 52. When at least one of the multiple rolls 52 is driven to rotate, the transfer belt 42 rotates in the direction of the arrow X, and conveys the primarily transferred image to the opposing position 54.

[0037] The transfer cylinder 46 has a function of transferring the toner image transferred onto the transfer belt 42 to a sheet in cooperation with the transfer roll 48. The transfer cylinder 46 is disposed on the lower left side of the transfer belt 42 so as to face the transfer belt 42. The transfer cylinder 46 is formed in a cylindrical shape with the axial direction being the front-to-rear direction. The transfer cylinder 46 rotates together with a sprocket (not shown) around which the chain 20 is wound. A groove 46A (an example of a first groove portion) for suppressing interference with the gripper 18 is formed on the outer periphery, which is the outer portion in the radial direction of rotation of the transfer cylinder 46. When the gripper 18 passes between the transfer cylinder 46 and the secondary transfer roll 48, the gripper 18 passes while being disposed in the groove 46A.

[0038] The secondary transfer roll 48 faces the transfer cylinder 46 at a predetermined facing position 54, with the transfer belt 42 disposed between the secondary transfer roll 48 and the transfer cylinder 46. More specifically, the secondary transfer roll 48 is disposed on the upper right side relative to the transfer cylinder 46.

[0039] In the transfer section 30, the paper conveyed by the gripper 18 and the chain 20 is sandwiched between the transfer belt 42 and the transfer cylinder 46 at the facing position 54, and the toner image transferred to the outer circumferential surface of the transfer belt 42 is transferred to the paper at the facing position 54 by electrostatic force generated by applying a secondary transfer bias between the transfer cylinder 46 and the secondary transfer roll 48. Therefore, the facing position 54 can be said to be a secondary transfer position where an image is secondarily transferred. Furthermore, the facing position 54 can be said to be an image forming position where an image is formed on the paper. The facing position 54 can be said to be a sandwiching position (i.e., a sandwiching area) where the paper is sandwiched between the transfer belt 42 (i.e., the secondary transfer roll 48) and the transfer cylinder 46. Furthermore, the facing position 54 can be said to be a position (i.e., a contact area) where the secondary transfer roll 48 and the transfer belt 42 come into contact with each other.

[0040] (Fixing unit 16) The fixing unit 16 shown in Fig. 1 has a function of fixing an image on a sheet of paper to the sheet of paper. Specifically, the fixing unit 16 has a fixing cylinder 56 and a pressure roll 58. The pressure roll 58 is an example of a pressure unit. In the fixing unit 16, the image transferred to the sheet of paper is fixed to the sheet of paper by heating and the pressure between the pressure roll 58 and the fixing cylinder 56.

[0041] The fixing cylinder 56 is formed in a cylindrical shape with the front-rear direction as the axial direction. The outer diameter of the fixing cylinder 56 is set to the same dimension as the outer diameter of the transfer cylinder 46 within the range of the tolerance that is determined. The fixing cylinder 56 is disposed on the left side of the transfer cylinder 46 and is disposed at the same position in the up-down direction as the transfer cylinder 46 within the range of the tolerance that is determined. The fixing cylinder 56 rotates together with a sprocket (not shown) around which the chain 20 is wound. The number of teeth of this sprocket is set to the same number of teeth as the sprocket that rotates together with the transfer cylinder 46. A groove 56A (an example of a second groove portion) for suppressing interference with the gripper 18 is formed on the outer peripheral portion, which is the outer portion in the rotational radial direction of the fixing cylinder 56. In this embodiment, the dimensions of each portion of the groove 56A are set to the same dimension as the dimensions of each portion of the groove 46A of the transfer cylinder 46 within the range of the tolerance that is determined. When the gripper 18 passes between the fixing cylinder 56 and the pressure roll 58, it passes while being disposed in the groove 56A.

[0042] In this embodiment, a mechanism is provided for moving the pressure roll 58 away from the fixing cylinder 56 when the pressure roll 58 passes over the concave groove 56A of the fixing cylinder 56, and for moving the pressure roll 58 closer to the fixing cylinder 56 (returning it to its original position) when the pressure roll 58 has completed passing over the concave groove 56A of the fixing cylinder 56. Note that this mechanism may not be provided.

[0043] Then, in the fixing section 16, the paper conveyed by the gripper 18 and the chain 20 is sandwiched between the fixing cylinder 56 and the pressure roll 58, and the image transferred to the paper is fixed to the paper. Therefore, the position where the paper is sandwiched between the fixing cylinder 56 and the pressure roll 58 can also be called the fixing position where the image is fixed. Furthermore, this position can also be called the sandwich position (i.e., sandwich area) where the paper is sandwiched between the pressure roll 58 and the fixing cylinder 56. Furthermore, this position can also be called the position (i.e., contact area) where the pressure roll 58 and the fixing cylinder 56 come into contact with each other.

[0044] In this embodiment, a first intermediate shaft portion 60 and a second intermediate shaft portion 63 are provided around which the chain 20 is wound on the upstream side in the rotational direction of the transfer cylinder 46 and the downstream side in the rotational direction of the fixing cylinder 56. The first intermediate shaft portion 60 and the second intermediate shaft portion 63 are examples of inner intermediate shaft portions.

[0045] The first intermediate shaft portion 60 and the second intermediate shaft portion 63 are supported so as to be rotatable with the front-rear direction as the axial direction. The first intermediate shaft portion 60 and the second intermediate shaft portion 63 are configured to include a pair of sprockets around which the pair of chains 20 are respectively wound, a shaft member that axially connects the pair of sprockets, and a flywheel fixed to the shaft member.

[0046] In this embodiment, the first intermediate shaft portion 60 is disposed below the fixing cylinder 56. The chain 20 is wound around the first intermediate shaft portion 60 from the inside thereof. The second intermediate shaft portion 63 is disposed to the right of the first intermediate shaft portion 60 and to the left of the transfer cylinder 46. The chain 20 is wound around the second intermediate shaft portion 63 from the inside thereof.

[0047] (Configuration for suppressing deterioration of image quality of transferred image) Next, the essential configuration of this embodiment will be described.

[0048] As shown in FIG. 2, when the end of the groove 56A of the fixing cylinder 56 in the rotation direction comes into contact with the pressure roll 58, the speed fluctuation (rotational speed fluctuation) of the fixing cylinder 56 occurs. In particular, when the upstream end 56B of the groove 56A of the fixing cylinder 56 in the rotation direction comes into contact with the pressure roll 58, the speed fluctuation (rotational speed fluctuation) of the fixing cylinder 56 occurs. In addition, when the speed fluctuation (rotational speed fluctuation) of the fixing cylinder 56 occurs, the speed fluctuation (rotational speed fluctuation) of the transfer cylinder 46 and the photoconductor 32 also occurs. Therefore, in this embodiment, the speed fluctuation of the transfer cylinder 46 and the photoconductor 32 is suppressed, thereby suppressing the deterioration of the image quality of the image transferred to the paper and the toner image transferred to the transfer belt 42. Hereinafter, a configuration for suppressing the speed fluctuation of the transfer cylinder 46 and the photoconductor 32 will be described.

[0049] As shown in FIG. 2, in this embodiment, a first motor 64 that rotates the transfer cylinder 46 and a second motor 66 that rotates the fixing cylinder 56 are provided. The first motor 64 and the second motor 66 are, for example, AC servo motors. The rotation of the first motor 64 is reduced by a first reducer 65 and transmitted to the transfer cylinder 46. The rotation of the second motor 66 is reduced by a second reducer 67 and transmitted to the fixing cylinder 56. Here, the first motor 64 and the first reducer 65 that reduces the rotation of the first motor 64 and transmits it to the transfer cylinder 46 constitute a first drive unit 68 that rotates the transfer cylinder 46. The second motor 66 and the second reducer 67 that reduces the rotation of the second motor 66 and transmits it to the fixing cylinder 56 constitute a second drive unit 70 that rotates the fixing cylinder 56.

[0050] In this embodiment, the rated output of the first motor 64 constituting the first driving section 68 and the rated output of the second motor 66 constituting the second driving section 70 are, for example, the same rated output of 1500 W. In addition, the reduction ratio of the first reducer 65 constituting the first driving section 68 and the reduction ratio of the second reducer 67 constituting the second driving section 70 are, for example, the same reduction ratio of 40. As a result, the speed (rotational speed) of the first motor 64 is reduced to 1 / 40 by the first reducer 65 and transmitted to the transfer cylinder 46, and the speed (rotational speed) of the second motor 66 is reduced to 1 / 40 by the second reducer 67 and transmitted to the fixing cylinder 56.

[0051] Furthermore, the rotation of the first motor 64 and the rotation of the second motor 66 are controlled independently. The rotation of the first motor 64 is detected by an encoder (not shown). Then, the rotation of the first motor 64 is controlled so that the rotation detected by this encoder approaches a target value. Similarly, the rotation of the second motor 66 is detected by an encoder (not shown). Then, the rotation of the second motor 66 is controlled so that the rotation detected by this encoder approaches a target value.

[0052] In this embodiment, the volume of the hollowed-out portion of the fixing cylinder 56, the mass of the flywheel, etc., and the volume of the hollowed-out portion of the transfer cylinder 46, the mass of the flywheel, etc. are adjusted, so that the moment of inertia of the fixing cylinder 56 is set to be larger than the moment of inertia of the transfer cylinder 46. As a result, the ratio of the moment of inertia of the fixing cylinder 56 to the output torque of the second drive unit 70 is larger than the ratio of the moment of inertia of the transfer cylinder 46 to the output torque of the first drive unit 68. In other words, when the output torque (rated torque) of the second drive unit 70 is T2, the moment of inertia about the rotation axis of the fixing cylinder 56 is I2, the output torque (rated torque) of the first drive unit 68 is T1, and the moment of inertia about the rotation axis of the transfer cylinder 46 is I1, the following formula 1 is satisfied. (I2 / T2)>(I1 / T1)...Equation 1 The rated torque refers to the drive torque when the rated output is generated after the rotation is stabilized at the rated voltage and rated frequency. Therefore, when the second drive unit 70 is driven at the rated voltage and rated frequency, the output torque of the second drive unit 70 is the rated torque. In contrast, when the second drive unit 70 is driven at a voltage and frequency different from the rated voltage and rated frequency, the output torque after the rotation is stabilized at the voltage and rated frequency becomes the output torque of the second drive unit 70.

[0053] In this embodiment, the mass of the fixing cylinder 56 is greater than the mass of the transfer cylinder 46. As a result, the ratio of the mass of the fixing cylinder 56 to the output torque of the second drive unit 70 is greater than the ratio of the mass of the transfer cylinder 46 to the output torque of the first drive unit 68. In other words, when the mass of the transfer cylinder 46 is M2 and the mass of the transfer cylinder 46 is M1, the following formula 2 is satisfied. Note that in a configuration in which the dimensions of each part of the fixing cylinder 56 and the dimensions of each part of the transfer cylinder 46 are set to the same dimensions within a specified tolerance range, if formula 1 is satisfied, then formula 2 is also satisfied. Similarly, if formula 2 is satisfied, then formula 1 is also satisfied. (M2 / T2)>(M1 / T1)...Formula 2

[0054] Here, as an example, the mass M1 of the transfer cylinder 46 can be set to 30 kg or less, and the mass M2 of the fixing cylinder 56 can be set to 50 kg or more. More preferably, the mass M1 of the transfer cylinder 46 can be set to 20 kg or less, and the mass M2 of the fixing cylinder 56 can be set to 60 kg or more.

[0055] 1, in this embodiment, the mass M3 of the photoconductor 32 is set to be smaller than the mass M2 of the fixing cylinder 56. In addition, in this embodiment, the mass M3 of the photoconductor 32 is set to be smaller than the mass M1 of the transfer cylinder 46. That is, in this embodiment, the following formula 3 is satisfied. M2>M1>M3...Formula 3

[0056] (Actions and Effects of the Present Embodiment) Next, the operation and effects of this embodiment will be described.

[0057] In the image forming apparatus 10 of the present embodiment described above, the moment of inertia I2 of the fixing cylinder 56 is set to be larger than the moment of inertia I1 of the transfer cylinder 46, so that the ratio of the moment of inertia I2 of the fixing cylinder 56 to the output torque T2 of the second drive unit 70 is larger than the ratio of the moment of inertia I1 of the transfer cylinder 46 to the output torque T1 of the first drive unit 68. That is, the above formula 1 is satisfied. As a result, even if the speed fluctuation of the transfer cylinder 46 occurs due to the vibration generated on the fixing cylinder 56 side being transmitted to the transfer cylinder 46 side via the chain 20, the speed of the transfer cylinder 46 can be quickly returned to a predetermined speed by the second drive unit 70 compared to a configuration in which the moment of inertia I2 of the fixing cylinder 56 and the moment of inertia I1 of the transfer cylinder 46 are set to be equal. That is, the speed fluctuation of the transfer cylinder 46 can be suppressed. As a result, it is possible to suppress deterioration of the image quality of the image transferred to the paper at the opposing position 54, which is the secondary transfer position.

[0058] The ratio of the moment of inertia of the fixing cylinder 56 to the output torque of the second drive unit 70 may be made larger than the ratio of the moment of inertia of the transfer cylinder 46 to the output torque of the first drive unit 68 by setting the rated output of the first motor 64 higher than the rated output of the second motor 66 or by setting the reduction ratio of the first reducer 65 higher than the reduction ratio of the second reducer 67. In this case, even if there is no difference between the moment of inertia of the fixing cylinder 56 and the moment of inertia of the transfer cylinder 46 or even if the moment of inertia of the fixing cylinder 56 is smaller than the moment of inertia of the transfer cylinder 46, the rotation speed of the transfer cylinder 46 can be quickly restored to a predetermined rotation speed. That is, the speed fluctuation of the transfer cylinder 46 can be suppressed. Even if the mass of the fixing cylinder 56 is lighter than the mass of the transfer cylinder 46, the moment of inertia of the fixing cylinder 56 can be made larger than the moment of inertia of the transfer cylinder 46 by providing mass concentration parts on the outer periphery and inner periphery of the fixing cylinder 56 and the transfer cylinder 46.

[0059] 3 and 4 show graphs of a configuration including a fixing cylinder 56 according to a comparative example set to a mass M2' lighter than the mass M2 of the fixing cylinder 56 of the present embodiment, and a transfer cylinder 46 according to a comparative example set to a mass M1' greater than the mass M1 of the transfer cylinder 46 of the present embodiment and equal to the mass M2'. FIG. 3 shows a graph with the speed V2 of the fixing cylinder 56 according to the comparative example set to the mass M2' as the vertical axis and time t as the horizontal axis. Note that time t0 coincides with the time when the upstream end 56B of the groove 56A of the fixing cylinder 56 in the rotation direction comes into contact with the pressure roll 58. As shown in this figure, the speed V2 of the fixing cylinder 56 fluctuates after time t0.

[0060] 4 shows a graph with the torque U1 of the transfer cylinder 46 set to the mass M1' according to the comparative example on the vertical axis and time t on the horizontal axis. As shown in this graph, after time t0, the torque U1 of the transfer cylinder 46 fluctuates.

[0061] As can be seen from FIGS. 3 and 4, when the upstream end 56B in the rotation direction of the groove 56A of the fixing cylinder 56 comes into contact with the pressure roll 58, the torque T1 of the transfer cylinder 46 changes almost simultaneously.

[0062] 5 and 6 show graphs of a configuration with the fixing cylinder 56 of this embodiment set to mass M2 and the transfer cylinder 46 of this embodiment set to mass M1. FIG. 5 shows a graph with the speed V2 of the fixing cylinder 56 of this embodiment set to mass M2 on the vertical axis and time t on the horizontal axis. As shown in this figure, after time t0, the speed V2 of the fixing cylinder 56 fluctuates, but the range of fluctuation is smaller than that of the condition in FIG. 3. This effect is due to changing the mass of the fixing cylinder from M2' to M2.

[0063] 6 shows a graph with the torque U1 of the transfer cylinder 46 of this embodiment set to mass M1 on the vertical axis and time t on the horizontal axis. As shown in this figure, after time t0, the torque U1 of the transfer cylinder 46 fluctuates, but the fluctuation range is smaller than that of the conditions in FIG. 3. This effect is due to changing the mass of the fixing cylinder from M2' to M2.

[0064] As can be seen from Figures 5 and 6 above, by setting the mass of the fixing cylinder 56 to be greater than that under the conditions of Figure 3 and by setting the mass of the fixing cylinder 56 to be greater than the mass of the transfer cylinder 46, the fluctuation range of the torque U1 of the transfer cylinder 46 can be reduced compared to the conditions of Figure 3.

[0065] 7 shows a graph in which the vertical axis indicates the speed V1 of the transfer cylinder 46 in a configuration with the fixing cylinder 56 of the present embodiment set to mass M2 and the transfer cylinder 46 of the present embodiment set to mass M1, and the horizontal axis indicates time t. FIG. 8 shows a graph in which the vertical axis indicates the speed V1 of the transfer cylinder 46 in a configuration with the fixing cylinder 56 of the present embodiment set to mass M2 and the transfer cylinder 46 of the comparative example set to mass M1', and the horizontal axis indicates time t. From this figure, the fluctuation of the transfer cylinder 46 from the predetermined speed v1 and the return to the predetermined speed v1 can be read. As shown in these figures, under the conditions of FIG. 7, the amount of fluctuation of the transfer cylinder 46 from the predetermined speed v1 after time t0 can be reduced and the speed can be returned to v1 quickly, compared to the conditions of FIG. 8.

[0066] As shown in FIG. 1, in this embodiment, the mass M3 of the photoconductor 32 is set to be smaller than the mass M2 of the fixing cylinder 56. This makes it possible to reduce the speed fluctuation of the photoconductor 32 caused by the speed fluctuation of the fixing cylinder 56, compared to a configuration in which the mass M3 of the photoconductor 32 is set to be equal to or larger than the mass M2 of the fixing cylinder 56. In addition, in this embodiment, the mass M3 of the photoconductor 32 is set to be smaller than the mass M1 of the transfer cylinder 46. This makes it possible to reduce the speed fluctuation of the photoconductor 32 caused by the speed fluctuation of the transfer cylinder 46, compared to a configuration in which the mass M3 of the photoconductor 32 is set to be equal to or larger than the mass M1 of the transfer cylinder 46. As a result, it is possible to suppress deterioration of the image quality of the toner image transferred to the transfer belt 42 at the primary transfer position 50.

[0067] The above-described configurations can be appropriately selected and combined. Also, each member constituting the image forming apparatus 10 can be replaced with another member having a similar function.

[0068] As described above, in the image forming apparatus 10, the ratio of the moment of inertia I1 of the fixing cylinder 56 to the output torque T2 of the second drive unit 70 is equal to the ratio of the moment of inertia I1 of the transfer cylinder 46 to the output torque T1 of the first drive unit 68, and thus the image quality of the image transferred to the paper can be prevented from being impaired.

[0069] In the image forming device 10, degradation of the image quality of the image transferred to the paper can be suppressed compared to a configuration in which the moment of inertia I2 of the fixing cylinder 56 and the moment of inertia I1 of the transfer cylinder 46 are set to be the same or a configuration in which the moment of inertia I2 of the fixing cylinder 56 is set to be smaller than the moment of inertia I1 of the transfer cylinder 46.

[0070] In the image forming apparatus 10, degradation of the image quality of the image transferred to the paper can be suppressed compared to a configuration in which the mass M1 of the transfer cylinder 46 and the mass M2 of the fixing cylinder 56 are set to the same mass.

[0071] In the image forming apparatus 10, degradation of the image quality of the image transferred to the recording medium can be suppressed compared to a configuration in which the mass M1 of the transfer cylinder 46 and the mass M2 of the fixing cylinder 56 are set outside the above-mentioned range (mass M1 is 30 kg or less and mass M2 is 50 kg or more).

[0072] In the image forming apparatus 10, degradation of the image quality of the image transferred to the recording medium can be suppressed compared to a configuration in which the mass M1 of the transfer cylinder 46 and the mass M2 of the fixing cylinder 56 are set outside the above-mentioned range (mass M1 is 20 kg or less and mass M2 is 60 kg or more).

[0073] In the image forming device 10, the occurrence of misalignment in the toner image transferred to the transfer belt 42 can be suppressed compared to a configuration in which the mass M3 of the photosensitive drum 32 is set to the same mass as or larger than the mass M2 of the fixing drum 56.

[0074] In the image forming device 10, the occurrence of misalignment in the toner image transferred to the transfer belt 42 can be suppressed compared to a configuration in which the mass M3 of the photosensitive body 32 is set to the same mass as or larger than the mass M1 of the transfer cylinder 46.

[0075] In the image forming apparatus 10, the first drive section 68 and the second drive section 70 having the same rated output can be used.

[0076] In the image forming device 10, the loss of image quality of the image transferred to the paper can be suppressed compared to a configuration in which the ratio of the mass M2 of the fixing cylinder 56 to the output torque T2 of the second drive unit 70 is set to be the same as the ratio of the mass M1 of the transfer cylinder 46 to the output torque T1 of the first drive unit 68, or a configuration in which the ratio of the mass M2 of the fixing cylinder 56 to the output torque T2 of the second drive unit 70 is set to be smaller than the ratio of the mass M1 of the transfer cylinder 46 to the output torque T1 of the first drive unit 68.

[0077] Although one embodiment of the present invention has been described above, the present invention is not limited to the above, and it is of course possible to implement the present invention in various other modified forms without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0078] 10 Image forming device. 18 Gripper (gripping part) 20 Chain (circulating member) 32 Photoreceptor 42 Transfer belt 46 Transfer cylinder 46A Groove (First Groove) 56 Fixed body 56A Groove (Second Groove) 68 First Drive Unit 70 Second Drive Unit

Claims

1. a transfer cylinder that is rotatably supported and has a first groove formed in a radially outer portion thereof, and an image is transferred onto a recording medium that passes over a surface of the transfer cylinder that is radially outer; a fixing cylinder that is rotatably supported and has a second groove portion formed in a radially outer portion thereof, and that fixes the image transferred to the recording medium passing over a surface on the radially outer side of the fixing cylinder, onto the recording medium; a rotating member that is formed in an annular shape, stretches across at least the transfer cylinder and the fixing cylinder, and rotates in accordance with the rotation of the transfer cylinder and the fixing cylinder; a gripping member supported by the rotating member, gripping the recording medium, and disposed in the first groove when passing through a radially outer portion of the transfer cylinder, and disposed in the second groove when passing through a radially outer portion of the fixing cylinder; A first drive unit that rotates the transfer cylinder; a second drive unit that rotates the fixing cylinder and has a ratio of a moment of inertia of the fixing cylinder to an output torque of the second drive unit set to be larger than a ratio of a moment of inertia of the transfer cylinder to an output torque of the first drive unit; An image forming apparatus comprising:

2. 2. The image forming apparatus according to claim 1, wherein the moment of inertia of the fixing cylinder is set to be larger than the moment of inertia of the transfer cylinder.

3. a transfer cylinder that is rotatably supported and has a first groove formed in a radially outer portion thereof, and an image is transferred onto a recording medium that passes over a surface of the transfer cylinder that is radially outer; a fixing cylinder that is rotatably supported and has a second groove portion formed in a radially outer portion thereof, the image transferred to the recording medium passing on the radially outer surface thereof is fixed to the recording medium, and the fixing cylinder has a mass larger than that of the transfer cylinder; a rotating member that is formed in an annular shape, stretches across at least the transfer cylinder and the fixing cylinder, and rotates in accordance with the rotation of the transfer cylinder and the fixing cylinder; a gripping member supported by the rotating member, gripping the recording medium, and disposed in the first groove when passing through a radially outer portion of the transfer cylinder, and disposed in the second groove when passing through a radially outer portion of the fixing cylinder; A first drive unit that rotates the transfer cylinder; A second drive unit that rotates the fixing cylinder; An image forming apparatus comprising:

4. 4. The image forming apparatus according to claim 3, wherein the mass of the transfer cylinder is 30 kg or less, and the mass of the fixing cylinder is 50 kg or more.

5. 5. The image forming apparatus according to claim 4, wherein the mass of the transfer cylinder is 20 kg or less, and the mass of the fixing cylinder is 60 kg or more.

6. a photoconductor that is rotatably supported and has a toner image formed on its radially outer surface; a transfer belt formed in an annular shape and rotating in one direction, the toner image being transferred onto the transfer belt by the rotation of the photoconductor on an outer peripheral surface of the transfer belt; Further equipped with 6. The image forming apparatus according to claim 1, wherein the mass of the photoconductor is set to be smaller than the mass of the fixing cylinder.

7. 7. The image forming apparatus according to claim 6, wherein the mass of the photoconductor is smaller than the mass of the transfer cylinder.

8. 8. The image forming apparatus according to claim 1, wherein the first drive section and the second drive section have the same rated output.

9. An image forming apparatus according to any one of claims 1 to 8, wherein the ratio of the mass of the fixing cylinder to the output torque of the second drive unit is set to be greater than the ratio of the mass of the transfer cylinder to the output torque of the first drive unit.

Images