JP2004359438A - Belt conveyance device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a belt conveyance device capable of letting walk rate of a belt member react to misalignment amount given to a steering roll sensitively, improving control performance related to displacement in the direction of width of the belt member, and reducing cost. <P>SOLUTION: This belt conveyance device is provided with the endless belt member stretched around a plurality of conveyance members and turning along a predetermined passage, a driving roll forming one of the plurality of conveyance members and transmitting rotation power to the belt member, and the steering roll forming one of the remaining conveyance members other than the driving roll and changing an arrangement angle for the other conveyance member arbitrarily. The conveyance member adjacent to the upstream side or the downstream side of the steering roll with respect to the direction of rotation of the belt member among the plurality of conveyance members is constituted as a non-directional conveyance member. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a belt conveying device that rotates an endless belt member while being wound around a plurality of conveying rolls, and more particularly, to a sheet conveying belt or an intermediate transfer device of an image forming apparatus such as an electrophotographic copying machine or a printer. The present invention relates to an improvement in a belt conveying device used as a belt.
[0002]
[Prior art]
[Patent Document 1] JP-A-11-295948
[0003]
2. Description of the Related Art In an image forming apparatus such as a color copying machine or a color printer that forms a full-color image, yellow, magenta, cyan, and black toner images formed on an image carrier such as a photosensitive drum are recorded in accordance with image information. It is necessary to transfer the image on a sheet. There are various methods for overlapping and fading each color toner image on a recording sheet.For example, a recording sheet is electrostatically adsorbed on an endless sheet conveying belt and conveyed with the rotation of the sheet conveying belt. Or a structure in which the toner images of each color are sequentially transferred from the image carrier to the recording sheet to be transferred, or the toner images of each color are not directly transferred from the image carrier to the recording sheet, but to an endless intermediate transfer belt. There has been known a printer which is configured to perform secondary transfer to a recording sheet after primary transfer. The latter method, in which a toner image is indirectly transferred from an image carrier to a recording sheet via an intermediate transfer belt, is capable of superimposing toner images of each color on the intermediate transfer belt. Multicolor toner images can be superimposed without being affected by fluctuations in the resistance value of the recording sheet, and the color image can be compared with the former case in which each color toner image is directly transferred to the recording sheet. In addition to easy control of the transfer conditions of the toner image during formation, conveyance of the recording sheet is also simplified, and there are advantages such as occurrence of sheet jam can be prevented as much as possible.
[0004]
When a plurality of color toner images are superimposed on the sheet conveying belt or the intermediate transfer belt in this manner, in order to form a high-quality color recording image without color shift, the sheet conveying belt or the intermediate transfer belt is used. It is important that the belt does not displace in the width direction during its rotation. However, in general, when a belt member formed into an endless shape is wound around a plurality of transport rolls including a drive roll and a driven roll and rotated, the belt member exerts a biasing force along the axial direction of the transport roll. The belt member is displaced in the axial direction of the transport roll, that is, in the width direction of the belt member, in order to obtain a stable rotation position. This is due to a molding error of the belt member, a diameter error of the transport roll, a misalignment at the time of assembling, and the like.
[0005]
Therefore, various proposals have been made to stably rotate an endless belt member along a fixed path. One of the proposals is to freely use one of the transport rolls around which the belt member is wound. 2. Description of the Related Art There is known a steering system which is configured as a steering roll that can be tilted to a predetermined angle, and suppresses displacement of a belt member in a width direction by operating the steering roll.
[0006]
The simplest configuration of this steering system is to tilt the steering roll after assembly of the image forming apparatus or at the time of installation after transport, etc. to intentionally give misalignment and suppress the widthwise displacement of the belt member. Things are known. Even if a biasing force in the width direction acts on the belt member due to a molding error of the belt member, an error of the diameter of the transport roll and a misalignment at the time of assembling, a distortion of the apparatus frame due to the installation of the image forming apparatus, etc. If a misalignment is applied to the steering roll, and a biasing force in the opposite direction that counteracts the biasing force is applied and the balance is achieved, the belt member will be displaced in the width direction unless a new biasing force is applied thereafter. It turns stably without doing.
[0007]
However, when the belt member is used for a sheet conveying belt or an intermediate transfer belt of an image forming apparatus, various members such as a transfer roll, a cleaner, and a recording sheet come into contact with the belt member during the execution of a recording image forming process. The belt member will always act in the width direction of the belt member. Adjusting the amount of misalignment of the steering roll only after the assembly of the device or at the time of installation will require the belt member. Movement in the width direction cannot be suppressed. For this reason, a so-called active steering system has been known in which a width direction of a belt member is sequentially detected and a steering roll is tilted based on the detection result. Specifically, an edge sensor for detecting the end position of the belt member in the width direction is provided. After the edge sensor detects the movement of the belt member in the width direction when a biasing force is applied, the edge sensor detects the movement. Tilting the steering roll based on this, intentionally giving misalignment to the steering roll, thereby suppressing and correcting the movement of the belt member in the width direction, and continuing the belt member at a predetermined reference position in the width direction. (See Japanese Patent Application Laid-Open No. H11-295948).
[0008]
[Problems to be solved by the invention]
In such a steering method, when a misalignment is intentionally given to the steering roll, the conveying direction of the belt member by the steering roll is inclined with respect to the original rotation direction of the belt member. As a result, A biasing force acts on the belt member. Accordingly, as the misalignment amount of the steering roll increases, the lateral force acting on the belt member in the width direction increases, and the amount of movement of the belt member in the width direction per rotation (hereinafter referred to as “walk rate”). Also gets bigger. Originally, this walk rate should constitute a substantially proportional relationship with the amount of misalignment of the steering roll as shown by the solid line in the graph of FIG.
[0009]
However, as shown in FIG. 11, when the steering roll 100 is tilted, the transport roll 102 located upstream or downstream of the steering roll 100 with respect to the rotation direction of the belt member 101 is not parallel to the steering roll 100. That is, the belt member 101 is being conveyed in a direction different from that of the steering roll 100. Therefore, when the transport roll 102 is close to the steering roll 100, the biasing force exerted on the belt member 101 by the steering roll 100 is reduced, and the relationship between the misalignment amount of the steering roll 100 and the walk rate is shown in FIG. It will be as shown by the broken line inside. That is, when the amount of misalignment given to the steering roll 100 becomes larger than a certain level, the walk rate is saturated.
[0010]
When the response characteristic of the walk rate of the belt member to the misalignment amount of the steering roll deteriorates, the following problem occurs. That is, when a deviation force in the width direction due to a molding error of the belt member, an error in the diameter of the transport roll, a misalignment at the time of assembling, or the like is large, even if a large misalignment amount is given to the steering roll, the deviation is small. The force cannot be canceled, and the movement of the belt member in the width direction cannot be suppressed.
[0011]
Further, the broken line graph in FIG. 10 is based on the assumption that the belt member is in an ideal state in which the belt member does not meander in the width direction when no misalignment is given to the steering roll. If a certain degree of misalignment has already been given to the steering roll after the assembly is completed or when the apparatus is installed, the steering roll causes a walk rate to the belt member at that time. The dashed line graph is shifted upward and downward as indicated by the dashed line (in FIG. 10, shifted downward). For this reason, even if a new misalignment amount is given to the steering roll, the belt member generates a shift force in one of the width directions, but hardly generates a shift force in the other direction. When a new biasing force acts on the belt member due to contact, etc., the biasing force to cancel this can not be applied by the steering roll, and the belt member is displaced endlessly in the width direction and eventually breaks Will be done.
[0012]
The present invention has been made in view of such a problem, and an object of the present invention is to make it possible to make a walk rate of a belt member sensitive to an amount of misalignment given to a steering roll. It is an object of the present invention to provide a belt conveying device that can improve control performance relating to displacement of a member in a width direction and can realize this at low cost.
[0013]
[Means for Solving the Problems]
That is, the present invention provides an endless belt member that is wound around a plurality of transport members and rotates along a predetermined path, and forms one of the plurality of transport members and rotates with respect to the belt member. In a belt transport device including a drive roll that transmits power, and a steering roll that forms one of the remaining transport members other than the drive roll and that can freely change an arrangement angle with respect to the other transport members. In addition, among the plurality of transport members, a transport member adjacent to an upstream side or a downstream side of the steering roll with respect to a rotation direction of the belt member is configured as a non-directional transport member.
[0014]
According to such a technical means, the transport member adjacent to the upstream or downstream side of the steering roll with respect to the rotation direction of the belt member is configured as an omnidirectional transport member. Does not guide the belt member in a specific conveying direction, and even if the omnidirectional conveying member is close to the steering roll, the biasing force exerted on the belt member by the steering roll is reduced. It won't. As a result, the relationship between the misalignment amount of the steering roll and the walk rate of the belt member constitutes a substantially proportional relationship, and the walk rate of the belt member reacts sensitively to the misalignment amount given to the steering roll, The control performance with respect to the displacement of the belt member in the width direction can be improved.
[0015]
Here, as the omnidirectional transport member, a belt member is hung, but it is sufficient that the belt member is not guided in a specific transport direction. For example, a plate on which the inner peripheral surface of the belt member slides is provided. Any baffle may be used. Further, a ball cage in which a large number of rotatable balls are arranged may be used as the non-directional transport member, and the balls may be rolled in contact with the inner peripheral surface of the belt member.
[0016]
This omni-directional transport member is effective when applied to the transport member adjacent to the upstream and downstream sides of the steering roll with respect to the rotation direction of the belt member, but is sufficiently applied to any one of the transport members. The desired effect can be obtained. In this case, it is preferable to apply the present invention to a conveying member closer to the steering roll.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the belt conveying device of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing the configuration of a color laser beam printer employing the belt conveying device of the present invention as an intermediate transfer belt. This laser beam printer includes four image forming engines 10Y, 10M, 10C, and 10Bk that form toner images for each of the colors of yellow, magenta, cyan, and black, and the toner images are primarily transferred from each image forming engine. The image forming apparatus includes an intermediate transfer belt 20, and is configured to secondarily transfer a toner image multiplex-transferred onto the intermediate transfer belt 20 to a recording sheet P to form a full-color image.
[0018]
The intermediate transfer belt 20 is formed in an endless shape and is wrapped around a plurality of belt transport rolls 21 to 24 including a drive roll 21 and a slip baffle 25. Each of the color image forming engines 10Y rotates while rotating in the arrow direction. , 10 M, 10 C, and 10 Bk. The intermediate transfer belt 20 is made of, for example, a polyimide resin, and is formed endless by welding both ends of a thin film film sheet having a thickness of 60 to 90 μm.
[0019]
A secondary transfer roll 30 is disposed at a position facing the belt transport roll 23 with the intermediate transfer belt 20 interposed therebetween, and the recording sheet P is inserted between the transfer roll 30 and the intermediate transfer belt 20 that are pressed against each other. Thus, the secondary transfer of the toner image is received from the intermediate transfer belt 20. That is, the belt transport roll 23 functions as a backup roll of the transfer roll 30. As shown in FIG. 2, the secondary transfer roll 30 is configured to be able to freely contact and separate from the intermediate transfer belt 20, and is located at a retracted position (a broken line position) separated from an operating position (a solid line position) that is in contact with the intermediate transfer belt 20. Is set to one of them. Usually, the secondary transfer roll 30 is set to the retracted position while the rotation of the intermediate transfer belt 20 is stopped, and is set to the operation position after the intermediate transfer belt 20 starts rotating.
[0020]
On the other hand, a belt cleaner 26 of the intermediate transfer belt 30 is disposed at a position facing the drive roll 21 so as to remove toner remaining on the intermediate transfer belt 20 from the intermediate transfer belt 20 after the secondary transfer. Have been.
[0021]
The four image forming engines 10Y, 10M, 10C, and 10Bk described above are arranged in series in the image receiving span of the intermediate transfer belt 20 along the rotation direction of the intermediate transfer belt 20. The correspondingly formed toner image is primarily transferred to the intermediate transfer belt 20. These four image forming engines are arranged in the order of yellow 10Y, magenta 10M, cyan 10C, and black 10Bk along the rotation direction of the intermediate transfer belt 20, and form the black image which will be used most frequently. The image engine 10Bk is arranged closest to the secondary transfer section. Each of the image forming engines 10Y, 10M, 10C, and 10Bk includes a raster scanning unit 12 that exposes the photosensitive drum 11 included in each image forming engine in accordance with image information. The laser light Bm modulated accordingly exposes the photosensitive drums 11 of the image forming engines 10Y, 10M, 10C and 10Bk.
[0022]
Each of the image forming engines 10Y, 10M, 10C, and 10Bk includes a photosensitive drum 11, a charger 13 that charges the photosensitive drum 11 to a uniform background potential, and a photosensitive drum 11 that is exposed by the laser beam Bm. A developing unit 14 for developing the electrostatic latent image formed on the body drum 11 to form a toner image, and residual toner and paper dust from the surface of the photosensitive drum 11 after transferring the toner image to the intermediate transfer belt 20. And a pre-cleaning neutralizer 16 for neutralizing residual toner prior to cleaning by the cleaner so that a toner image corresponding to image information of each color can be formed on the photosensitive drum 11. Is configured.
[0023]
Primary transfer rolls 17Y, 17M, 17C, and 17Bk are disposed at positions facing the photosensitive drums 11 of the image forming engines 10Y, 10M, 10C, and 10Bk so as to sandwich the intermediate transfer belt 20. By applying a predetermined transfer bias voltage to the photosensitive drums 17Y, 17M, 17C, and 17Bk, the charged toner image on the photosensitive drum 11 is transferred to the intermediate transfer belt 20.
[0024]
As shown in FIG. 3, among these primary transfer rolls 17Y, 17M, 17C, and 17Bk, primary transfer rolls 17Y provided for image forming engines 10Y, 10M, and 10C of three colors of yellow, magenta, and cyan. , 17M, and 17C are configured so as to be able to freely contact and separate from the intermediate transfer belt 20, and are operating positions (solid line positions) where the intermediate transfer belt 20 is sandwiched between the photosensitive drums 11 of the image forming engines 10Y, 10M, and 10C. And the retracted position (broken line position) for separating the intermediate transfer belt 20 from the photosensitive drum 11. On the other hand, the primary transfer roll 17Bk corresponding to the black image forming engine 10Bk is always in contact with the intermediate transfer belt 20. The primary transfer rolls 17Y, 17M, and 17C are configured to be retracted from the intermediate transfer belt 20 in a monochrome mode print job that forms only a black-and-white image. This is for protecting 10Y, 10M, and 10C. In a standby state in which the main power of the printer is turned on and waiting for the start of a print job, the primary transfer rolls 17Y, 17M, and 17C are set to the retracted positions, and only the primary transfer roll 17Bk is in contact with the intermediate transfer belt 20. The print job in the monochrome mode can be started immediately. When a print job in the color mode for forming a full-color image is started, the primary transfer rolls 17Y, 17M, and 17C are changed from the retracted position to the operating position. The reason why the primary transfer rolls 17Y, 17M, and 17C are set in the standby mode in correspondence with the monochrome mode is that it takes more time to process image information at the start of the full-color mode than at the start of the monochrome mode. Therefore, if the set positions of the primary transfer rolls 17Y, 17M, and 17C are changed using that time, the start of the print job is not particularly delayed.
[0025]
In the case of the monochrome mode among the print jobs of the color laser beam printer configured as described above, first, the rotation of the intermediate transfer belt 20 is started, and then the secondary transfer roll 30 set at the retracted position is moved to the retracted position. Set to the operating position. While the rotation of the intermediate transfer belt 20 is stopped, the primary transfer rolls 17Y, 17M, and 17C are set to the retracted positions. In the case of the monochrome mode, the print job is executed with the primary transfer rolls set to the retracted positions. . That is, as shown in FIG. 4, only the black image forming engine 10Bk is in a state where the toner image can be primarily transferred to the intermediate transfer belt 20.
[0026]
When the intermediate transfer belt 20 starts rotating in this manner, the raster scanning unit 12 exposes the photosensitive drum 11 of the image forming engine 10Bk at a predetermined timing in accordance with the image information, and thereby the photosensitive member of the image forming engine 10Bk is exposed. A toner image corresponding to the image information is formed on the drum 11, and the black toner image is transferred to the rotating intermediate transfer belt 20.
[0027]
After the recording sheet P is pulled out one by one from the paper feed cassette 40 by the paper feed roll 41, the intermediate transfer belt 20 and the secondary transfer roll 30 come into contact with each other via a predetermined sheet feeding path 46 shown by a broken line in the drawing. The sheet is fed to the secondary transfer section. A registration roll 42 is provided in front of the secondary transfer unit. The entry timing of the recording sheet P into the secondary transfer unit is controlled by the registration roll 42, and the recording sheet P is primarily transferred onto the intermediate transfer belt 20. Alignment with the toner image is performed. A predetermined transfer bias voltage is applied to the backup roll 24 facing the secondary transfer roll 30 with the intermediate transfer belt 20 interposed therebetween, and the toner image held on the intermediate transfer belt 20 is It is electrostatically transferred to the recording sheet P by a transfer electric field formed between the recording sheet P and the backup roll 24.
[0028]
After the recording sheet P on which the secondary transfer of the toner image has been performed is separated from the intermediate transfer belt 20, the recording sheet P is conveyed to a fixing device 44 by two sheet conveying belts 43 arranged in series. Then, the recording sheet is discharged to the discharge tray 45 after the toner image is heated and fixed.
[0029]
On the other hand, in the case of the color mode, as in the case of the monochrome mode, first, the rotation of the intermediate transfer belt 20 is started, and then the secondary transfer roll 30 set at the retracted position is set at the operating position. After the rotation of the intermediate transfer belt 20 is started, the primary transfer rolls 17Y, 17M, and 17C set at the retracted position are set at the operation positions, and as shown in FIG. 1, the total transfer including the black primary transfer roll 17Bk is performed. All the primary transfer rolls are in a state where the intermediate transfer belt is sandwiched between the primary transfer roll and the photosensitive drum.
[0030]
When the intermediate transfer belt 20 starts rotating in this way, the raster scanning unit 12 exposes the photosensitive drums 11 of the image forming engines 10Y, 10M, 10C, and 10Bk at a predetermined timing in accordance with the image information of each color. As a result, a toner image corresponding to the image information is formed on the photosensitive drum 11 of each of the image forming engines 10Y, 10M, 10C, and 10Bk. The toner images formed by the respective image forming engines 10Y, 10M, 10C, and 10Bk are sequentially transferred to the rotating intermediate transfer belt 20, and on the intermediate transfer belt 20, a multi-toner image in which toner images of respective colors overlap. Is formed. The recording sheet P is fed to the secondary transfer unit in the same manner as in the monochrome mode, and the multi-toner image held on the intermediate transfer belt 20 is secondarily transferred to the recording sheet P by the secondary transfer roll 30. Is done. Thereafter, the recording sheet P is heated and fixed to the toner image via the fixing device 44 and is discharged to the discharge tray 45.
[0031]
In the thus configured color printer of the present embodiment, the intermediate transfer belt 20 meanders (moves in the width direction) by a so-called active steering method in order to superimpose the toner images of the respective colors on the intermediate transfer belt 20 with high accuracy. Has been prevented. As shown in FIG. 5, in the active steering system, after the position in the width direction of the rotating intermediate transfer belt 20 is detected by the edge sensor 1, the width direction of the intermediate transfer belt 20 is determined with respect to the intermediate transfer belt 20 based on the detection result. A correction external force acting in the (lateral direction) is applied to correct the position of the intermediate transfer belt 20 in the width direction to a predetermined reference position. The corrected external force is applied to the intermediate transfer belt 20 as a lateral biasing force by tilting the steering roll (belt transport roll) 22. As the tilting amount of the steering roll 22, that is, the misalignment amount increases, the intermediate transfer belt 20 Large deviation force acts on the intermediate transfer belt 20, and the lateral movement of the intermediate transfer belt 20 is suppressed by the deviation force, or the intermediate transfer belt 20 can be moved to a predetermined position in the width direction.
[0032]
The amount of misalignment given to the steering roll 22 is calculated by the correction controller 2 composed of a microcomputer system, and given to a steering motor described later. The correction control unit 2 takes in the detection result of the edge sensor 1, compares the detection result, that is, the actual position in the width direction of the intermediate transfer belt 20 with a predetermined reference position, and sets the misalignment amount to be given to the steering roll 22. Is calculated.
[0033]
FIG. 6 is a schematic diagram showing a specific configuration of the edge sensor 1. The edge sensor 1 includes an actuator 4 supported swingably around a rotation axis 3 and a transmission type photosensor 5 whose output voltage changes according to the movement of the actuator 4. One end of the actuator 4 is a contact portion 6 which comes into contact with an end portion of the intermediate transfer belt 20 in the width direction. The contact portion 6 is separated from the intermediate transfer belt 20 by a spring 7 so as not to be separated from the intermediate transfer belt 20. Is being urged toward. The other end of the actuator 4 is configured as a light shielding plate 8 inserted between the light emitting unit and the light receiving unit of the photo sensor 5. Is configured to change the insertion amount with respect to. Therefore, when the intermediate transfer belt 20 moves (walks) in the lateral direction (the direction of the arrow), the actuator 4 swings around the rotation shaft 3 and the output voltage of the photosensor 5 changes with this. By checking the output voltage, the amount of movement of the intermediate transfer belt 20 in the lateral direction can be ascertained.
[0034]
FIG. 7 is a schematic diagram showing a specific configuration for tilting the steering roll 22. As shown in FIG. One end of the rotation shaft of the steering roll 22 is rotatably supported by a fixedly provided device frame 50, while the other end is supported by one end of a swing arm 51. The swing arm 51 is swingably provided around a rotation shaft 52, and the other end opposite to the steering roll 22 is in pressure contact with an eccentric cam 53. The eccentric cam 53 is connected to a steering motor 54. When the steering motor 54 is rotated, the eccentric cam 53 rotates, whereby one end of the swing arm 51 that supports the steering roll 22 swings up and down. Is configured. As the steering motor 54, a stepping motor capable of controlling the rotation angle with high accuracy is used.
[0035]
The principle of the meandering correction of the intermediate transfer belt 20 by the tilting of the steering roll 22 will be described. First, as shown in FIG. 7A, the eccentric cam 53 stops at a predetermined angle, and the steering is performed in accordance with the stop angle. It is assumed that the running intermediate transfer belt 20 does not move (meander) in the width direction y while the roll 22 is held substantially horizontally (the inclination is substantially zero). From this state, as shown in FIG. 7B, when the eccentric cam 53 is rotated counterclockwise in the figure by driving the steering motor 54, the swing arm 51 moves in the θ1 direction according to the amount of eccentricity of the eccentric cam 53. Rocks. As a result, one end of the steering roll 22 is lifted by the swing arm 51, so that the steering roll 22 is inclined according to the amount of lifting. At this time, the intermediate transfer belt 20 wound around the steering roll 22 moves to the roll end lifted by the swing arm 51. On the other hand, as shown in FIG. 7C, when the eccentric cam 53 is rotated clockwise in the figure by driving the steering motor 54, the swing arm 51 moves in the θ2 direction according to the amount of eccentricity of the eccentric cam 53. Rocks. As a result, one end of the steering roll 22 is pushed down by the swing arm 51, so that the steering roll 22 is inclined according to the amount of pushing down. At this time, the intermediate transfer belt 20 wound around the steering roll 22 moves to the side opposite to the roll end pushed down by the swing arm 51.
[0036]
For this reason, the position fluctuation of the intermediate transfer belt 20 in the width direction y is detected by the edge sensor 1 described above, and based on the detection result, the steering motor 54 is driven to give an appropriate misalignment amount to the steering roll 22. By doing so, the movement of the intermediate transfer belt 20 in the width direction can be suppressed, and the position in the width direction on the steering roll 22 can be corrected. As a result, the intermediate transfer belt 20 can be stabilized on a certain path without walking. It can be turned around.
[0037]
As described above, the intermediate transfer belt 20 is wrapped around the belt transport rolls 21 to 24 including the drive roll 21 and the steering roll 22, and is wrapped around the slip baffle 25, and rotates along a predetermined path. . The intermediate transfer belt 20 is stretched between the drive roll 21 and the slip baffle 25 to form an image receiving span of the toner image. The image forming engines 10Y, 10M, 10C, and 10Bk are arranged along the image receiving span. The toner image is transferred from each photosensitive drum 11 to the intermediate transfer belt 20 within the image receiving span.
[0038]
The steering roll 22 may be provided at any position in the circumferential direction of the intermediate transfer belt 20. However, if the winding angle of the intermediate transfer belt 20 with respect to the rotation center of the steering roll 22 is set to be large, the steering roll 22 In this embodiment, the steering roll 22 is disposed at the end opposite to the drive roll 21 because the width of the intermediate transfer belt 20 is significantly moved by the tilt of the intermediate transfer belt 20. The slip baffle 25 is provided at a position separating the steering roll 22 from the image receiving span, so that the image receiving span is not twisted even when the steering roll 22 is tilted.
[0039]
By providing a normal belt transport roll, that is, an idler roll that rotates with the rotation of the intermediate transfer belt 20, at the position where the slip baffle 25 is provided, the stability of the image receiving span can be similarly secured. . However, if the belt transport roll is provided close to the steering roll 22, when the steering roll 22 is tilted, the transport direction of the intermediate transfer belt 20 by the belt transport roll and the transport direction of the intermediate transfer belt 20 by the steering roll 22 will be described. Does not coincide with each other, and the approaching belt conveyance roll reduces the lateral bias generated on the intermediate transfer belt 20 due to the tilting of the steering roll 22. For this reason, in the present embodiment, a slip baffle 25 that does not exhibit directionality with respect to the conveyance of the intermediate transfer belt 20 is used as a conveyance member that loops the intermediate transfer belt at a position close to the steering roll 22. That is, the slip baffle 25 corresponds to the omnidirectional transport member of the present invention.
[0040]
As shown in FIG. 8, the slip baffle 25 is formed of a conductive plate member 25a, and has a circular cross section so that the intermediate transfer belt 20 can be smoothly guided from the image receiving span to the steering roll 22. . Further, if electric charges are accumulated in the slip baffle 25, the toner primarily transferred on the surface of the intermediate transfer belt 20 may be scattered on the slip baffle 25. Have been. Further, the surface of the plate member 25a is covered with a resin coating layer 25b having a low friction coefficient in order to reduce a friction force acting between the intermediate transfer belt 20 and the intermediate transfer belt 20.
[0041]
The slip baffle 25 only supports the intermediate transfer belt 20 from the inner peripheral surface side, and does not guide the intermediate transfer belt 20 with any directionality. For this reason, when the steering roll 22 is tilted to exert a biasing force on the intermediate transfer belt 20, the slip baffle 25 does not exert any force to reduce the biasing force. Accordingly, as shown by the solid line in the graph of FIG. 10, the walk rate of the intermediate transfer belt 20 caused by the tilting of the steering roll 22 is exerted in a substantially proportional relationship with the misalignment amount of the steering roll 22. The larger the amount of misalignment is given to the steering roll 22, the larger the walk rate can be given to the intermediate transfer belt 20.
[0042]
As a result, in the printer of the present embodiment, the control performance of the displacement of the intermediate transfer belt 20 in the width direction using the steering roll 22 can be remarkably improved as compared with the related art. Even if the error in the diameter and the mounting angle of the belt transport rollers 21 to 24, the distortion of the main body frame, and the like are large, the misalignment of the steering roll 22 is merely adjusted to displace the intermediate transfer belt 20 in the width direction. Thus, the intermediate transfer belt 20 can be smoothly circulated along a fixed path without meandering.
[0043]
FIG. 9 shows another embodiment of the omnidirectional transport member according to the present invention. In the above-described embodiment, the slip baffle 25 shown in FIG. 8 is used as the non-directional transport member, and the intermediate transfer belt 20 is configured to slide on the slip baffle 25. However, in the example shown in FIG. The ball cage 27 is used in place of the baffle 25. In this ball cage 27, a large number of balls 27a are arranged on the surface of a plate-like member 27b, and each ball 27a is rotatably held by the plate-like member 27b. The ball 27a is in contact with the inner peripheral surface of the intermediate transfer belt 20. When the intermediate transfer belt 20 rotates, the ball 27a is rotated by the belt 20 and rotates.
[0044]
Even when the ball cage 27 shown in FIG. 9 is used instead of the slip baffle 25, the ball 27a in contact with the intermediate transfer belt 20 has some directionality unlike a roll having a rotation axis. When the steering roll 22 is tilted to apply a biasing force to the intermediate transfer belt 20, the ball cage 27 does not exert any force to reduce the biasing force. Therefore, similarly to the embodiment using the slip baffle, the controllability of the widthwise displacement of the intermediate transfer belt 20 using the steering roll 22 can be remarkably improved as compared with the related art. Even if the error, the error of the diameter of the belt transport rolls 21 to 24, the error of the mounting angle, the distortion of the main body frame, and the like are large, the misalignment amount of the steering roll 22 is only adjusted and the intermediate transfer belt 20 can be moved in the width direction. And meandering can be prevented.
[0045]
【The invention's effect】
As described above, according to the belt transport device of the present invention, the omnidirectional transport member adjacent to the upstream or downstream side of the steering roll with respect to the rotation direction of the belt member guides the belt member in the specific transport direction. Even if the omnidirectional conveying member is close to the steering roll, the biasing force exerted on the belt member by the steering roll is not diminished. The walk rate of the belt member can be made to react sensitively to the given amount of misalignment, thereby improving the control performance with respect to the displacement of the belt member in the width direction, and realizing this at low cost. Becomes possible.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a full-color laser beam printer in which a belt conveyance device of the present invention is applied to an intermediate transfer belt.
FIG. 2 is a diagram illustrating a configuration in which a secondary transfer roll retracts with respect to an intermediate transfer belt.
FIG. 3 is a diagram illustrating a configuration in which a primary transfer roll retracts with respect to an intermediate transfer belt.
FIG. 4 illustrates a print job in a monochrome mode.
FIG. 5 is a diagram illustrating a configuration of an active steering system for controlling a position of an intermediate transfer belt in a width direction.
FIG. 6 is a diagram showing a configuration of an edge sensor.
FIG. 7 is a diagram illustrating a relationship between tilting of a swaging roll and movement of an intermediate transfer belt in a width direction.
FIG. 8 is a sectional view showing an embodiment using a slip baffle as one of the conveying members of the intermediate transfer belt.
FIG. 9 is a sectional view showing an embodiment using a ball cage as one of the conveying members of the intermediate transfer belt.
FIG. 10 is a graph illustrating a relationship between a misalignment amount of a steering roll and a walk rate of a belt member.
FIG. 11 is a diagram illustrating a problem in which a belt conveyance roll adjacent to the steering roll reduces the biasing force exerted by the steering roll.
[Explanation of symbols]
Reference numeral 20: intermediate transfer belt, 21: drive roll, 22: steering roll, 25: slip baffle, 27: ball cage

Claims (8)

An endless belt member that is wound around a plurality of transport members and rotates along a predetermined path; and a drive roll that forms one of the plurality of transport members and transmits rotational power to the belt members. And, while forming one of the remaining transport members other than the drive roll, in a belt transport device including a steering roll capable of arbitrarily changing the arrangement angle with respect to the other transport members,
A belt transport device, wherein, among the plurality of transport members, a transport member adjacent to an upstream side or a downstream side of the steering roll with respect to a rotation direction of the belt member is configured as a non-directional transport member. The transport member adjacent to the steering roll among the transport members adjacent to the upstream side or the downstream side of the steering roll is configured as the non-directional transport member. Belt transport device. The belt conveyance device according to claim 1, wherein the omnidirectional conveyance member is formed of a conductive plate member, and the belt member is in sliding contact with the plate member. The belt conveyance device according to claim 1, wherein the omnidirectional conveyance member is a ball cage in which a large number of balls that are in contact with the belt member and are rotatable are arranged. After a toner image corresponding to image information is formed on an image carrier, the toner image is primarily transferred from the image carrier to an endless intermediate transfer belt, and further secondary-transferred from the intermediate transfer belt to a recording sheet. In the image forming apparatus configured in
While the intermediate transfer belt is wound around a plurality of transport members and rotates along a predetermined path,
The plurality of transport members are configured to include a drive roll that transmits rotational power to the intermediate transfer belt, and a steering roll that can arbitrarily change an arrangement angle with respect to other transport members,
An image forming apparatus, wherein a conveying member adjacent to an upstream side or a downstream side of the steering roll with respect to a rotation direction of the intermediate transfer belt is configured as a non-directional conveying member. The intermediate transfer belt contacts the image carrier at an image receiving span stretched between a pair of transport members other than the steering roll,
Among the pair of transport members located at both ends of the image receiving span, one of the transport members is configured as the omnidirectional transport member, and the steering roll is provided adjacent to the omnidirectional transport member. The image forming apparatus according to claim 1, wherein: 7. The image forming apparatus according to claim 5, wherein the omnidirectional transport member is formed of a conductive plate member, and the intermediate transfer belt is in sliding contact with the plate member. 7. The image forming apparatus according to claim 5, wherein the omnidirectional conveying member is a ball cage in which a large number of rotatable balls are arranged while being in contact with the endless belt.

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