Patent Application
20080003024
Exemplary embodiments of the present invention are explained in detail below with reference to the accompanying drawings.
This color image forming apparatus includes, for example, a transfer belt unit 10 having an intermediate transfer belt 71, which is an endless belt, four image stations linearly disposed, a paper-feeding cassette (paper feeding unit) 1, and a writing device 8.
Each image station has disposed therein a relevant one of image carriers (photosensitive drums) 20Y, 20C, 20M, and 20K, a relevant one of charging devices 30Y, 30C, 30M, and 30K, a relevant one of developing devices 50Y, 50C, 50M, and 50K, a relevant one of cleaning devices 40Y, 40C, 40M, and 40K. Toner bottles 9 are disposed in the order of, from the left in the drawing, yellow (Y), cyan (C), magenta (M), and black (K) toners, supplying a predetermined supply amount to the developing devices 50Y, 50C, 50M, and 50K by a toner conveying mechanism not shown.
Upon a print signal, a transfer sheet 2 goes out from the paper feeding cassette 1 by a paper feeding roller 3, and the tip of the transfer sheet 2 is sent to resist rollers 4. The sent transfer sheet is detected by a sensor to see whether a jam has occurred. In synchronization with an image signal, the transfer sheet is then sent from the resist rollers to a transfer position.
On the other hand, on the image carrier 20, which is uniformly charged by the charging device 30 according to a print signal, an electrostatic latent image corresponding to the image signal is formed by the writing device 8. Each electrostatic latent image is developed by a relevant one of the developing devices 50Y, 50C, 50M, and 50K that accommodates a toner with a color corresponding to the electrostatic latent image to form a toner image.
The toner images formed on the image carriers 20Y, 20C, 20M, and 20K are sequentially transferred on the intermediate transfer belt 71 with a transfer voltage applied from initial transfer rollers 12Y, 12C, 12M, and 12K to form a superposed toner image.
The superposed toner image formed on the intermediate transfer belt 71 is conveyed to a position of a secondary transfer roller 5, and is then transferred on the transfer sheet 2 with a transfer electric field applied between the secondary transfer roller 5 and a facing roller 16. With this, the superposed toner image is formed on the transfer sheet.
The transfer sheet 2 having the superposed toner image formed thereon is then conveyed to a fixing device 6, where the toner image is fixed, and is then delivered by delivering rollers 7 onto a paper delivery tray.
Toners left on the image carriers 20Y, 20C, 20M, and 20K are removed from each cleaning device, and is charged by a charging device with an alternating current superposed on a direct current simultaneously with static elimination, thereby preparing for the next image formation.
The toner left on the intermediate transfer belt 71 is removed by an intermediate transfer belt cleaning device 13.
The charged intermediate transfer belt 71 is attenuated through natural discharge while rotation and the contact with a grounded intermediate transfer belt cleaning facing roller, thereby preparing for the next step.
A belt crack occurring at an edge in a width direction of the intermediate transfer belt is explained below.
The endless belt supporting mechanism relates to a structure of an end in a width direction (axial direction) when the intermediate transfer belt 71 is extended by an extending roller (for example, equivalent to a roller 16 in
A front-side reinforcing tape (front-side reinforcing member) 72 along the front surface of the belt edge, a rear-side reinforcing tape (rear-side reinforcing member) 73 along the back surface of the belt edge, and a guide member 74 for preventing meandering fixed onto the back-surface reinforcing tape are provided over an approximately entire circumference of both edges in the width direction of the intermediate transfer belt 71. An extending roller 60 has a step portion 61 in an end area in an axial direction facing to the rear-side reinforcing tap 73, the step portion 61 having a diameter smaller than a center area in the axial direction.
A height dimension (a difference in diameter dimension) of the step portion 61 is set larger than the thickness of the rear-side reinforcing tape 73. If the height of the step portion is lower than the thickness of the rear-side reinforcing tape, a belt portion where the rear-side reinforcing tape is provided can be considered as that the circumferential length is partially shortened. With this, a decrease in speed and a degradation in belt running ability occur at that portion, and the belt tends to be wavy. On the other hand, if the height dimension of the step portion 61 is excessively larger than the thickness of the rear-side reinforcing tape, a belt portion facing the step portion 61 falls in to an extending roller side to break. This causes a local load, and therefore a belt crack tends to occur.
A characteristic structure of the present invention is that a width dimension W1 of the front-side reinforcing tape 72 is wider than a width W2 of the rear-side reinforcing tape 73. In this manner, with the width W1 of the front-side reinforcing tape being wider than the width W2 of the rear-side reinforcing tape, a lift of the intermediate transfer belt 71 can be prevented to eliminate the occurrence of a belt wrinkle at the time of conveyance. Also, with the provision of the front-side reinforcing tape 72, the occurrence of a crack at the time of conveyance can be prevented.
With the provision of the front-side reinforcing tape 72, a reinforcing effect can be increased on the load on the guide member 74, and therefore a crack tends not to occur.
Furthermore, the width W1 of the front-side reinforcing tape 72 is wider than a width W3 of the step portion 61 having a small diameter provided at the end in the axial direction of the extending roller 60. With this, the occurrence of a belt crack due to the load on the belt at the end of the extending roller can be prevented.
In particular, the inner edge of the front-side reinforcing tape 72 is positioned to project to an inner side from a corner 61a of the step portion 61 by a distance equal to or greater than one millimeter. With this, the occurrence of a belt crack at the end of the roller can be more effectively prevented.
By adopting the structure depicted in
That is, an endless belt supporting mechanism has a feature in which a position of a joint portion 72a in a circumferential direction where both ends of the front-side reinforcing tape 72 in the circumferential direction are adjacent to each other is shifted from a position of a joint portion 73a in the circumferential direction where both ends of the rear-side reinforcing tape 73 in the circumferential direction are adjacent to each other, and has a feature in which each of the joint portions 72a and 73a is shifted in circumferential position from (is disposed to be separated from) a joint portion 74a where both ends of the guide member 74 in the circumferential direction are adjacent to each other.
Each of the reinforcing tapes 72 and 73 and the guide member 74 is attached by being bonded along the circumferential length of the mounting surface on a belt side. Therefore, both ends of each tape and the guide member are generally fixed onto the belt surface to be adjacent to each other. Since a belt portion corresponding to each of the joint portions 72a, 73a, and 74a has a decreased supporting strength, a crack tends to occur.
According to the present invention, both ends of the front-side reinforcing tape 72 in the circumferential direction not interfering the extending roller 60 are superposed (overlapped) each other for joint. Also, as for both ends of the rear-side reinforcing tape 73 in contact (interfering) with the extending roller 60 and the guide member 74, their both ends in the circumferential direction are disposed to be adjacent to each other without being superposed.
In this manner, the position of the joint portion 72a of the front-side reinforcing tape 72 in the circumferential direction is shifted from the position of the joint portion 73a of the rear-side reinforcing tape 73 in the circumferential direction, or the positions of the joint portions 72a and 73a of the reinforcing tapes 72 and 73 are shifted from the position of the joint portion 74a of the guide member 74 in the circumferential direction. With this, the occurrence of a crack due to insufficient strength of the belt surface where each joint is positioned can be prevented. Furthermore, at the same time, a long-life endless belt with a belt speed being unchanged can be provided.
In particular, as for the front-side reinforcing tape 72 in which an inconvenience can be prevented by superposing both of their ends in the circumferential direction, one end is superposed on the other end, thereby supplementing a decrease in belt strength.
When both ends of the front-side reinforcing tape 72 are superposed each other for joint and a running direction of the intermediate transfer belt 71 is assumed to be a rightward direction in
Furthermore, according to the present invention, any of polyimide, polyamid-imide, polycarbonate and others with high strength is selected as a material of the intermediate transfer belt 71, thereby preventing the occurrence of a crack and achieving a long life.
A table in
An intermediate transfer belt, a guide member, and a reinforcing tape have the following configuration.
Modulus of elasticity: 4500 megapascals
Gap between ends in a circumferential direction: 2 millimeters
Gap between ends of a rear-side reinforcing tape in a circumferential direction: 2 millimeters
Ends of a front-side reinforcing tape in a circumferential direction: laminated with superposition of 10 millimeters in the forward direction
The width of the rear-side reinforcing tape is ensured to be 8 millimeters, and a distance between the step portion and the rear-side reinforcing tape with the guide member being bumped against the roller end is ensured to be 0.5 millimeters, thereby preventing a mount of the roller on the rear-side reinforcing tape.
The width of the front-side reinforcing tape is 9.5 millimeters, and the width to cover the corner of the step portion is 1.0 millimeter. As the amount of shifting in the belt width direction is larger, the load on the guide member is larger, and therefore a belt crack tends to occur. Therefore, the amount of belt shifting is set at 30 μm/mm. This amount of shifting is 1.5 times as much as a target amount of shifting.
Under the conditions mentioned above, durability evaluation was performed in an intermittent paper through mode with an image formation mode of 1 to 5. With intermediate transfer belt durable specifications and 200K sheets, no crack occurred.
An A portion indicates an end of the guide member, whilst a B portion indicates a step portion. By taking these portions as starting points, whether a crack has occurred was evaluated.
Modulus of elasticity: 4800 megapascals
Modulus of elasticity: 3200 megapascals
Modulus of elasticity: 4500 megapascals
Modulus of elasticity: 4800 megapascals
Modulus of elasticity: 4800 megapascals
Modulus of elasticity: 4500 megapascals
Although the intermediate transfer belt has been mainly explained as an endless belt in the present embodiment, the present invention can also be applied to a transfer belt that absorbs a transfer sheet at a transferring position for conveyance and other endless belts.
According to one aspect of the present invention, the endless belt is provided with reinforcing members and a guide member for preventing meandering over an entire circumference at both ends in a width direction. Each extending rollers is provided with a step portion provided in an end area facing to reinforcing members having a diameter smaller than a center area. The reinforcing members are provided on front and back surfaces of the endless belt. The front-side reinforcing member has a width wider than a width of the rear-side reinforcing member. With this, a lift of the belt can be eliminated to avoid the occurrence of a belt wrinkle due to conveyance. Also, with the provision of the front and back reinforcing tapes, a belt crack can be prevented.
Furthermore, according to another aspect of the present invention, the front-side reinforcing member has a width wider than that of the step portion with a small diameter provided to an end of each of the extending rollers. With this, a belt crack due to a load on the belt at the roller end can be prevented from occurring.
Moreover, according to still another aspect of the present invention, the step portion is covered for a distance equal to or greater than one millimeter by the front-side reinforcing member. With this, a belt crack due to the end of the rollers can be prevented from occurring.
Furthermore, according to still another aspect of the present invention, joint portions of the guide member and the front and back reinforcing tapes are shifted from one another, both ends of the rear-side reinforcing member are not superposed each other, and both ends of the front-side reinforcing member are superposed each other. With this, a belt crack can be prevented from occurring at a portion where the strength of the joint portion is insufficient, and the need for superposing the ends of the rear-side reinforcing tape is eliminated. With this, a long-life endless belt with a belt speed being unchanged can be provided.
Moreover, according to still another aspect of the present invention, even a seal at an end of the cleaning blade or the like rubs in a sliding manner, a scarfing of an end of the reinforcing member can be prevented from occurring, thereby achieving a long life.
Furthermore, according to still another aspect of the present invention, polyimide, polyamide-imide, or polycarbonate with high strength is applied to the endless belt. With this, a crack can be prevented from occurring, thereby achieving a long life.
Although the invention has been described with respect to a specific embodiment for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-160211 | Jun 2006 | JP | national |
