Patent Grant
8406646
This application claims priority to Japanese Patent Application No. 2009-160668 filed on Jul. 7, 2009. The entire disclosure of Japanese Patent Application No. 2009-160668 is hereby incorporated herein by reference.
1. Technical Field
The present invention relates to an electro photographic type image forming apparatus and an image forming method to transfer a toner image onto access transfer material such as paper, and to form an image onto the transfer material using a transfer roller having an elastic member on its circumferential surface.
2. Related Art
In the related art, as an electro photographic type image forming apparatus, the image forming apparatus is suggested in which a transfer material gripping member is installed on a transfer roller, and a leading edge of the transfer material is pinched by the gripping member and transfers the toner image of the image carrier to the transfer material such as paper (for example, refer to JP-A-2000-508280). With the image forming apparatus, it is possible to reliably separate the transfer material from the image carrier after the transferring operation completed.
Additionally, another image forming apparatus is suggested in which a transfer roller having an elastic member on the surface thereof presses onto the image carrier to form a transfer nip, and a toner image of the image carrier is transferred onto the transfer material by applying a transfer bias to the transfer roller (for example, JP-A-2009-36943).
In the image forming apparatus described in JP-A-2009-36943, the transfer roller press-contacts the image carrier constantly. Therefore, the long-term pressure between the transfer roller and the image carrier causes the elastic member of the transfer roller to be deformed. When the elastic member of the transfer roller is deformed, banding or defects in the image are caused in the deformed portion, and the quality of the image is degraded.
An advantage of some aspects of the invention is to provide the image forming apparatus and the image forming method capable of performing a better image transfer and reliably separating the transfer material from the transfer roller.
According to one aspect of invention, there is provided an image forming apparatus and the image forming method. An elastic member is installed in the circumferential surface of the transfer roller having a concaved portion, along with which a transfer nip formation area is formed where the transfer roller is pressed against the image carrier when the image is transferred. In this case, the width of the concaved portion is larger than the width of the transfer nip formation area in the circumferential direction of the transfer roller. The transfer roller is stopped when the concaved portion is in the transfer nip formation area, so as not to have contact between the transfer roller and the image carrier when the image is not transferred. Thus, the transfer nip is not formed in the transfer nip formation area between the transfer roller and the image carrier when the image forming operation of the image forming apparatus is not performed. Accordingly, the elastic member of the transfer roller is not twisted, even when the image forming apparatus is not operated for a long time. Thus, the image defect and the occurrence of the banding caused by the twisting of the elastic member are suppressed effectively and a higher quality image can be obtained.
Referring now to the attached drawings which form a part of this original disclosure:
The present invention will now be described in terms of the explanatory embodiment with reference to the accompanying drawings.
The image forming apparatus 1 of the first embodiment forms an image using a liquid developer including toner particles and transfer liquid. As shown in
Each of the charging sections 3Y, 3M, 3C and 3K is installed around the photosensitive bodies 2Y, 2M, 2C and 2K, respectively. Exposure sections 4Y, 4M, 4C and 4K which are the image writing sections, developing sections 5Y, 5M, 5C and 5K, first transfer sections 6Y, 6M, 6C and 6K, and the photosensitive bodies cleaning sections 7Y, 7M, 7C and 7K are installed in this order in the rotational direction α of the photosensitive bodies 2Y, 2M, 2C and 2K from each of the charging sections 3Y, 3M, 3C and 3K.
Also, the image forming apparatus 1 includes a transfer belt, more specifically, an endless shaped intermediate transfer belt 8. The intermediate transfer belt 8 preferably constitutes an image carrier of the first embodiment. The intermediate transfer belt 8 is positioned above each of the photosensitive bodies 2Y, 2M, 2C and 2K. The intermediate transfer belt 8 is press-contacted to each of the photosensitive bodies 2Y, 2M, 2C and 2K with a first transfer section 6Y, 6M, 6C and 6K, respectively.
Although it is not shown in the drawings, the intermediate transfer belt 8 is preferably formed by 3 layered structure which is made by a relatively soft elastic belt, including a flexible substrate for example resin, an elastic layer, for example, rubber layer, formed on the surface of the substrate, and an outer layer formed on the surface of the elastic layer. As an embodiment of the intermediate transfer belt 8, for example, the intermediate transfer belt disclosed in JP-A-2009-36943 can be employed. The description of the intermediate transfer belt described in JP-A-2009-36943 is omitted because the intermediate transfer belt can be understood from the description therein. Of course, the intermediate transfer belt 8 is not limited to the belt described in JP-A-2009-36943. The intermediate transfer belt 8 is located tightly between the intermediate transfer belt driving roller 9 and the intermediate transfer belt tension roller 10. The intermediate transfer belt driving roller 9 is driven by the intermediate transfer belt driving motor (not shown). The intermediate transfer belt 8 is rotated in a rotational moving direction β, in a tensioned state.
Also, the location order of the photosensitive bodies corresponding to each of the colors Y, M, C and K is not limited to
A second transfer section 11 which is a transfer apparatus, is installed on the intermediate transfer belt driving roller 9 side of the intermediate transfer belt 8. The second transfer section 11 includes a second transfer roller 12 and a second transfer cleaning section 13.
As shown in
Further, the elastic member 12b of the second transfer roller 12 is press-contacted to the intermediate transfer belt 8 by bias force of a bias member like spring, not shown in the drawings. Accordingly, the second transfer nip 11a is formed in a transfer nip formation area between the intermediate transfer belt 8 and the elastic member 12b of the second transfer roller 12, as shown in
As shown in
Further, the transfer bias is applied to the second transfer roller 12. During the image forming operation, the second transfer roller 12 is rotated in the rotational direction β, and at the same time the transfer bias is applied when the second transfer roller 12 is moved to the moving direction β of the intermediate transfer belt 8, so that the toner image which is transferred to the intermediate transfer belt 8 with the transfer nip 11a is transferred to the transfer material like paper.
The gripper 15 which is a gripping member to pinch the transfer material, the gripper support member 16 which is an access receiving member receiving the gripper and seated by the gripper 15, and a separating click 17 which is a member for separating the transfer material, are installed in the concaved portion 14. Although not shown in the drawings, the gripper 15 is installed in a predetermined number along the axial direction of the second transfer roller 12, and each gripper 15 is formed in a shape of the teeth of a comb. Also, the gripper support member 16 is installed on the corresponding position of each gripper 15 and the separating click 17 is installed between the comb teeth, and at the outside of the comb teeth, which is located at both ends of the gripper 15.
Further, the image forming apparatus 1 has a gate roller 18 which transports the transfer material toward the second transfer nip 11a. Also, the gate roller 18 supplies the transfer material 19 to the second transfer nip 11a at such a timing that the toner image which is transported by the second transfer belt 8 is secondarily transferred at the second transfer section 11.
The gripper 15 is rotated toward the gripper support member 16 just before the concaved portion 14 reaches to the second transfer nip 11a, so that the gripper 15 pinches the leading edge 19a of the transfer material 19, which is transported toward the direction of the transportation direction δ from the gate roller 18, with the gripper support member 16. In the state in which the gripper 15 pinches the leading edge 19a of the transfer material 19, the toner image which is carried on the intermediate transfer belt 8, is transferred onto the transfer material 19 at the second transfer nip 11a. Further, in the state in which the gripper 15 pinches the leading edge 19a of the transfer material 19, the transfer material 19 which is passed through the second transfer nip 11a, is reliably separated from the intermediate transfer belt 8 forming the second transfer nip 11a. Then, the leading edge 19a of the transfer material 19 is released rotating toward the separating direction from the gripper support member 16. Also, before and after the release of the transfer material 19 by the gripper 15, each separating click 17 is projected to its projection position. Accordingly, the back surface of the leading edge of the transfer material 19 (the opposite surface of the toner image transfer surface of the transfer material) is projected from each separating click 17. In this way, the transfer material 19 is separated from the transfer roller 12. Then, each separating click 17 returns within the concaved portion 14. Each operation of the gripper 15 and the separating click 17 is controlled by the gripper control cam and the separating click control cam which are not shown in the drawings, by the rotation of the second transfer roller 12.
As shown in the
As shown in
In this case, the concaved portion 14 is integrally installed to be rotatable with the second transfer roller 12, so that relative position between the rotational position of the second transfer roller 12 and the rotational position of the concaved portion 14 is not changed, and both rotational positions are determined at once. Accordingly, the second transfer roller position signal which is output by the photo sensor 23 is the signal of the position of the concaved portion 14, and the photo sensor 23 and the cam 24 constitute the position detector of the concaved portion 14 which detects the rotational position of the concaved portion 14. In this case, when the photo sensor 23 outputs one of the second transfer roller position signals (ON signal), the second transfer roller position signal maintains an OFF signal until it newly detects the position of the concaved portion 14 and outputs the next second transfer roller position signals (ON signal).
As shown in
As shown in
As shown in
The second transfer roller cleaning section 13 removes the liquid developer which is attached on the elastic member 12b of the second transfer roller 12 with a cleaning member, such as a cleaning blade. The liquid developer which is removed by the cleaning member is returned to the liquid developer carrier.
Further, as shown in
The transfer material transporter 29 has a transfer material transport belt 29a having a plurality of holes and rotating in arrow direction in endless shape, and a suction member 29b. When the transfer material 19 is transported to the transfer material transporter 29, the transfer material 19 is drawn by air suction of the suction member 29b, and transported toward the third air flow generator 30 by the transfer material transport belt 29a. The third air flow generator 30 suctions air as indicated by the direction of the arrow. By air suction of the third air flow generator 30, the back surface of the transfer material 19 which is separated from the second transfer roller 12 is drawn toward the third air flow generator 30. Accordingly, the transfer material 19 is drawn and guided to the third air flow generator 30, and the transfer material 19 moves toward the image fixing section 31 due to the rotational force of the transfer material transport belt 29a. So, the toner image of the transfer material 19 is heated, pressed and fixed by the image fixing section 31.
As shown in
Next, the description will be made regarding the sequence control in the first embodiment which controls the rotation of the second transfer roller 12 on the basis of the image forming operation finish signal and the rotational position of the concaved portion 14 of the second transfer roller 12.
As shown in
Regarding the other constitution and other image forming operation of the image forming apparatus 1 in the first embodiment, these are the same as in the conventional related art image forming apparatus using a liquid developer, so the description thereof will be omitted.
In the image forming apparatus 1 of the first embodiment, the sheet shaped elastic member 12b is installed on the peripheral surface of the second transfer roller 12 having the concaved portion 14, and along with this, when the image forming operation is activated, the elastic member 12b is contacted and pressed to the intermediate transfer belt 8 to form the second transfer nip 11a in the transfer nip formation area. In this case, width w1 in the peripheral direction of the concaved portion 14 of the second transfer roller 12 is set to be larger than width w2 in the same direction of the transfer nip formation area where the second transfer nip 11a is formed (w1>w2). Further, when the image forming operation is not performed and the intermediate transfer belt/second transfer roller driving motor 20 is not driven, the second transfer roller 12 is stopped in a state in which the concaved portion 14 is placed in the transfer nip formation area so that the elastic member 12b is not in contact with the intermediate transfer belt 8. Thus, when the image forming apparatus 1 is not performing the image forming operation, the second transfer nip 11a is not formed between the intermediate transfer belt 8 and the second transfer roller 12. Accordingly, the twist occurrence can be suppressed in the elastic layer of the intermediate transfer belt 8 and the elastic member 12b of the second transfer roller 12, even though the second transfer belt 8 and the second transfer roller 12 is not driven for a long time. Also, the twist occurrence can be suppressed in the elastic member 12b of the second transfer roller 12, even though the second transfer belt 8 and the second transfer roller 12 are not driven for a long time. Accordingly, the image defect and/or banding which is caused by the twisting of the elastic member 12b of the second transfer roller 12 can be controlled effectively, whereby a good image quality can be obtained.
When the second transfer roller 12 is not rotated, the concaved portion 14 is positioned in the transfer nip formation area, so that the second transfer roller 12 can always stop in a constant position. Thus, when the next image forming operation is driven, the rotational position of the second transfer roller 12 can be controlled easily, so that the positioning between the rotational position of the second transfer roller 12 and the transported transfer material 19 can be accomplished easily.
Also, in the state in which the leading edge 19a of the transfer material 19 is pinched by the gripper 15, the transfer material 19 passes the second transfer nip 11a, so that the transfer material 19 can be separated easily from the intermediate transfer belt 8 after the second transfer.
Further, the intermediate transfer belt 8 has an elastic layer, so that the transfer efficiency can be raised even though the transfer material 19 has high surface roughness. The twist occurrence can be suppressed in the elastic layer of the second transfer belt 8 and the elastic member 12b of the second transfer roller 12, because the second transfer nip 11a is not formed even though the second transfer belt 8 and the second transfer roller 12 are not driven for a long time.
Referring now to
The second embodiment differs from the first embodiment in that, as shown in
In the second embodiment, a contact member of the intermediate transfer belt side includes a bearing 36 instead of the contact member 26 of the first embodiment. In this embodiment, the bearing 36 is a ball bearing having an inner lace 36a, an outer lace 36b, and balls 36c. In this case, the inner lace 36a is integrally attached to be rotatable with the rotational shaft 9a of the intermediate transfer belt driving roller 9. Accordingly, the outer lace 36b can rotate relatively with respect to the rotational shaft 9a.
As shown in
With further reference to the second embodiment, as shown in
Next, the description will be made regarding the sequence control which controls the driving of the second transfer roller 12 on the basis of the image forming operation finish signal and the rotational position of the concaved portion 14 of the second transfer roller 12 in the second embodiment.
As shown in
According to the image forming apparatus 1 of the second embodiment, each rotation of the intermediate transfer belt driving motor 34 and the second transfer roller driving motor 35 can be controlled independently, so that velocity of the intermediate transfer belt driving motor 34 and the second transfer roller driving motor 35 can be set properly, respectively.
Also, the elastic member 12b of the second transfer roller 12 is not contacted with the intermediate transfer belt 8 when the intermediate transfer belt driving motor 34 is not driven and when the second transfer roller driving motor 35 is not driven. Therefore, in the state that the elastic member 12b is not contacted with the intermediate transfer belt 8, it can control the unstable sliding between the intermediate transfer belt 8 and the elastic member 12b of the second transfer roller 12 when the intermediate transfer belt 8 starts the independent rotation or when the intermediate transfer belt 8 stops the independent rotation after the independent rotation.
Other than this, the constitution and effects of the image forming apparatus in the second embodiment are the same as those of the first embodiment.
Referring now to
The third embodiment is directed to when the intermediate transfer belt 8 is driven in the state that the second transfer roller 12 is stopped, so that the intermediate transfer belt 8 undergoes a process such as cleaning or resist matching with respect to the intermediate transfer belt 8. In this case, in the third embodiment, the intermediate transfer belt driving motor 34 and the second transfer roller driving motor 35 can use the block diagram of
The controller 32 controls the actuation of the intermediate transfer belt driving motor 34, in the other words, the rotation of the intermediate transfer belt 8 on the basis of the second transfer roller position signal (the concaved portion position signal; ON signal) from the photo sensor 23 and the intermediate transfer belt processing signal (ON signal) from the intermediate transfer belt processing signal output section. More specifically, in the third embodiment, the controller 32 stops the second transfer roller driving motor 35 when the second transfer roller position signal (ON signal) is output from the photo sensor 23 to the controller 32. Accordingly, the controller 32 controls the rotational position of the second transfer roller 12 (the rotational position of the concaved portion 14) on the basis of the position signal (ON signal) of the second transfer roller 12 and the finish signal (ON signal) of the image forming operation.
Next, the description will be made regarding the sequence control which controls the actuation of the intermediate transfer belt 8 on the basis of the intermediate transfer belt processing signal and the second transfer roller position signal in the third embodiment.
As shown in
According to the image forming apparatus of the third embodiment, in the state that the concaved portion 14 stops the rotation of the second transfer roller 12 at the transfer nip formation area, the intermediate transfer belt 8 is rotated. Thus, in the state that the elastic member 12b of the second transfer roller 12 is not contacted with the intermediate transfer belt 8, it is possible to rotate the intermediate transfer belt 8. However, in the case of the image forming apparatus, in which the second transfer roller 12 always contacts presses the intermediate transfer belt, when the cleaning or resist matching of the intermediate transfer belt 8 is processed, the distance between the rotational shaft of the second transfer roller and the rotational shaft of the intermediate transfer belt driving roller 9 is changed, so that it is necessary to separate the second transfer roller 12 from the intermediate transfer belt 8. Otherwise, in the image forming apparatus of the third embodiment, the second transfer roller 12 can be separated from the intermediate transfer belt 8 without substantially changing the distance between the rotational shaft 12c of the second transfer roller 12 and the rotational shaft 9a of the intermediate transfer belt driving roller 9. Thus, the processing with respect to the intermediate transfer belt 8 described above can be processed easily.
Other than this, the constitution and effects of the image forming apparatus in the third embodiment are the same as those of the second embodiment.
Referring now to
As shown in
As shown in
Further, the controller 32 controls the actuation of the second transfer roller driving motor 35, and controls the rotational position (the rotational position of the concaved portion 14) of the second transfer roller 12, on the basis of the second transfer roller position signal (the concaved portion position signal; ON signal) from the photo sensor 23 and the transfer material presence/absence signal (ON signal) from the transfer material presence/absence detector 38. In other words, the transfer material presence/absence signal (ON signal) is input to the controller 32 from the transfer material presence/absence detector 38, and it is determined that the transfer material 19 is jammed, then the second transfer roller position signal (ON signal) is input to stop the actuation of the second transfer roller driving motor 35. In this way, when the jam of the transfer material 19 has occurred in front of the transfer material presence/absence detector 38 in the material transporting direction, the concaved portion 14 of the second transfer roller 12 is stopped at the transfer nip formation area. Thus, when the second transfer roller 12 is stopped due to the occurrence of the jam in the transfer material 19, the elastic member 12b of the second transfer roller 12 is not contacted with the intermediate transfer belt 8.
Next, the description regarding the sequence control of the fourth embodiment will be made wherein the sequence control controls the rotation of the second transfer roller 12 on the basis of the transfer material presence/absence signal and the second transfer roller position signal.
As shown in
At this time, the transfer material presence/absence detector 38 does not detect the transfer material 19, and outputs the transfer material presence/absence signal (ON signal; signal that the transfer material is absent) until the transfer material 19 which is transported from the gate roller 18 reaches the detection timing position of the transfer material presence/absence detector 38. When the transfer material 19 reaches the detection timing position of the transfer material presence/absence detector 38, so that the transfer material presence/absence detector 38 detects the transfer material 19, the transfer material presence/absence detector 38 outputs the transfer material presence/absence signal (OFF signal; signal that the transfer material is present). In other words, the jam of the transfer material 19 does not occur (when the jam does not occur). Moreover, when the transfer material presence/absence detector 38 does not detect the transfer material 19 at the detection timing position, regardless of whether the jam of the transfer material occurs or does not occur, the transfer material presence/absence detector 38 outputs ON signal, so that any of ON signals is indicated as the transfer material presence/absence signal (ON signal) for convenience of the description in
If the transfer material 19 which is transported from the gate roller 18 is jammed, so that the transfer material 19 does not reach the detection timing position of the transfer material presence/absence detector 38, the transfer material presence/absence detector 38 does not detect the transfer material 19 at the detection timing position. Because of this, the transfer material presence/absence signal from the transfer material presence/absence detector 38 does not become OFF, and the transfer material presence/absence detector 38 outputs the transfer material presence/absence signal (ON signal) to the controller 32 continuously (detection that the transfer material is absent). In other words, the jam of the transfer material 19 occurs (when the jam occurs). Then, the controller 32 determines that the jam of the transfer material 19 has occurred, and when the second transfer roller position signal (ON signal) is input subsequently, the actuation of the second transfer roller driving motor 35 is stopped. Accordingly, when the jam of the transfer material 19 occurs, the second transfer roller 12 is stopped in the state that the elastic member 12b is not contacted to the intermediate transfer belt 8. Then, the controller 32 stops the actuation of the intermediate transfer belt driving motor 34, and the intermediate transfer belt 8 is stopped.
Thus, when the jam of the transfer material 19 is detected, the second transfer roller 12 rotates until the concaved portion 14 reaches the position of the second transfer nip 11a, and when the concaved portion 14 reaches the position of the second transfer nip 11a, the second transfer roller 12 is stopped. At this time, when the second transfer roller 12 rotates after the jam of the transfer material 19 is detected, the intermediate transfer belt 8 rotates too. Also, when the second transfer roller 12 rotates after the jam of the transfer material 19 is detected, the intermediate transfer belt 8 does not necessarily have to rotate. However, it is preferable to rotate the intermediate transfer belt 8 when the second transfer roller 12 rotates after the jam of the transfer material 19 is detected to decrease the friction between the second transfer roller 12 and the intermediate transfer belt 8.
According to the image forming apparatus of the fourth embodiment, when the jam of the transfer material 19 which is transported from gate roller 18 has occurred, the controller 32 stops the rotation of the second transfer roller 12 so that the concaved portion 14 is located to the position of the second transfer nip 11a on the basis of the second transfer roller position signal (ON signal) and the transfer material presence/absence signal (ON signal) from the transfer material presence/absence detector 38. Thus, it can be suppressed that the toner of the image transported on the intermediate transfer belt 8 may be attached on the second transfer roller 12. In particular, as shown in
In other respects, the constitution and effects of the image forming apparatus 1 in the fourth embodiment are the same as those in the second embodiment.
Referring now to
In the image forming apparatus of the fifth embodiment, in addition to the transfer material presence/absence detector 38 (herein after the first transfer material presence/absence detector 38, in the fifth embodiment) of the fourth embodiment, the second air flow generator 28 has the second transfer material presence/absence detector 39. The second transfer material presence/absence detector 39 detects the jam of the transfer material 19 which is already detected by the first transfer material presence/absence detector 38. The second transfer material presence/absence detector 39 may be the same as the first transfer material presence/absence detector 38, for example, a photo sensor may be used as described above.
As shown in
Further, the controller 32 controls the actuation of the second transfer roller driving motor 35, and controls the rotational position (rotational position of the concaved portion 14) of the second transfer roller 12 (rotational position of the concaved portion 14), on the basis of the second transfer roller position signal (the concaved portion position signal; ON signal) from the photo sensor 23, the first transfer material presence/absence signal (ON signal) from the first transfer material presence/absence detector 38 and the second transfer material presence/absence signal (ON signal) from the second transfer material presence/absence detector 39. In other words, the first transfer material presence/absence signal (ON signal) from the first transfer material presence/absence detector 38 is input in the controller 32 in the state that the second transfer roller 12 rotates in the direction γ (forward rotational direction). If the determination is that the jam of the transfer material 19 has occurred, then the actuation of the second transfer roller driving motor 35 is stopped when the second transfer roller position signal (ON signal) is input initially in the same manner as described above in the fourth embodiment. Thus, the concaved portion 14 of the second transfer roller 12 is stopped on the position of the transfer nip formation area when the jam of the transfer material 19 has occurred ahead of the first transfer material presence/absence detector 38 in the moving direction of the transfer material. Accordingly, if the second transfer roller 12 is stopped, when a jam of the transfer material 19 occurs, the elastic member 12b of the second transfer roller 12 is not contacted to the intermediate transfer belt 8.
Furthermore, if the controller 32 determines there is no jam occurrence of the transfer material 19 because the first transfer material presence/absence signal (OFF signal) is input from the first transfer material presence/absence detector 38, and the controller 32 determines there is a jam occurrence of the transfer material 19 because the second transfer material presence/absence signal (ON signal) is input from the second transfer material presence/absence detector 39, the concaved portion 14 passes through the transfer nip formation area, so that the second transfer roller driving motor 35 rotates in reverse. Thus, the second transfer roller 12 is controlled to rotate in reverse (reverse to the direction γ). After that, when the second transfer rotational position signal (ON signal) is input, the actuation of the second transfer roller driving motor 35 is stopped. Thus, after the first transfer material presence/absence detector 38 detects the transfer material 19 and when the second transfer material presence/absence detector 39 does not detect the transfer material 19, the second transfer roller 12 rotates in reverse so that the concaved portion 14 is stopped at the position of the second transfer nip 11a. Thus, after the second transfer material presence/absence detector 39 detects the jam occurrence of the transfer material 19, the elastic member 12b of the second transfer roller 12 is not contacted to the intermediate transfer belt 8 when the second transfer roller 12 is stopped.
Next, the description regarding sequence control in the fifth embodiment will be made wherein the sequence control controls the actuation of the intermediate transfer belt 8 on the basis of the first transfer material presence/absence signal, the second transfer material presence/absence signal and the second transfer roller position signal in the fifth embodiment.
As shown in
At this time, the first transfer material presence/absence detector 38 does not detect the transfer material 19, and outputs the first transfer material presence/absence signal (ON signal) until the transfer material 19 which is transported from the gate roller 18 reaches the detection timing position of the first transfer material presence/absence detector 38. When the first transfer material presence/absence detector 38 detects the transfer material 19 as the transfer material 19 reaches the detection timing position of the first transfer material presence/absence detector 38, the first transfer material presence/absence signal from the first transfer material presence/absence detector 38 becomes OFF. In other words, the transfer material 19 does not jam (when the jam does not occur). Further, the second transfer material presence/absence detector 39 does not detect the transfer material 19 and outputs the second transfer material presence/absence signal (ON signal), until the transfer material 19 reaches the detection timing position of the second transfer material presence/absence detector 39. When the transfer material 19 reaches the detection timing position of the second transfer material presence/absence detector 39, so that the second transfer material presence/absence detector 39 detects the transfer material 19, the second transfer material presence/absence signal from the second transfer presence/absence detector 39 becomes OFF. That is to say, the jam of the transfer material 19 does not occur (when the jam does not occur).
If the transfer material 19 from the gate roller 18 is jammed, so that the transfer material 19 does not reach the detection timing position of the first transfer material presence/absence detector 38, the first transfer material presence/absence detector 38 does not detect the transfer material 19 at the detection timing. At this time, the rotation of the second transfer roller 12 is stopped in the state that the elastic member 12b does not contact the intermediate transfer belt 8 in the same manner as the fourth embodiment described above.
Further, after the first transfer material presence/absence detector 38 detects the transfer material 19 at the detection timing position, so that the first transfer material presence/absence signal from the first transfer material presence/absence detector 38 becomes OFF, when the jam of the transfer material 19 occurs and the transfer material 19 does not reach the detection timing position of the second transfer material presence/absence detector 39, the second transfer material presence/absence detector 39 does not detect the transfer material 19 at the detection timing position. Therefore, the second transfer material presence/absence signal from the second transfer material presence/absence detector 39 does not become OFF, and the second transfer material presence/absence detector 39 outputs the second transfer material presence/absence signal (ON signal) to the controller 32 continuously (the second transfer material jam occurs). In other words, the jam of the transfer material 19 occurs (when the jam occurs). Then, the controller 32 determines that the second transfer material jam of the transfer material is occurring, and the second transfer roller driving motor 35 rotates in reverse. Namely, if the jam is detected after the second transfer roller 12 rotates forward; the roller 12 is stopped instantly and is then rotated in reverse. Also, at this time, the controller 32 rotates the intermediate transfer belt driving motor 34 in reverse, so that the intermediate transfer belt 8 is also rotated in reverse. After that, each actuation of the second transfer roller driving motor 35 and the intermediate transfer belt driving motor 34 is stopped respectively when the second transfer roller position signal (ON signal) is input initially. Accordingly, the second transfer roller 12 is stopped in the state in which the elastic member 12b is not contacted to the intermediate transfer belt 8, when the second transfer material jam of the transfer material 19 occurs.
As described above, when the second transfer material jam of the transfer material 19 occurs, the second transfer roller 12 rotates in reverse until the concaved portion 14 reaches the transfer nip formation area, and it is stopped when the concaved portion 14 reaches the transfer nip formation area. At this time, when the second transfer roller 12 rotates in reverse after the second transfer material jam of the transfer material 19 occurred, the intermediate transfer belt 8 also rotates in reverse. Also, the intermediate transfer belt 8 does not necessarily need to rotate in reverse when the second transfer roller 12 rotates in reverse after the second jam of the transfer material 19 occurs. However, it is preferable to rotate the intermediate transfer belt 8 when the second transfer roller 12 rotates in reverse after the jam of the transfer material 19 is detected to decrease the friction between the second transfer roller 12 and the intermediate transfer belt 8.
According to the image forming apparatus in the fifth embodiment, after the transfer material 19 is detected at the first transfer material presence/absence detector 38, and when the second transfer material jam of the transfer material 19 occurs, the controller 32 controls the second transfer roller 12 so as to rotate in reverse, on the basis of the second transfer roller position signal (ON signal) and the second transfer material presence/absence signal (ON signal) from the second transfer material presence/absence detector 39. Then, the reverse rotation of the second transfer roller 12 is stopped when the concaved portion 14 is located at the transfer nip formation area. Thus, it can suppress the toner which is transported by the intermediate transfer belt 8 that may attach the second transfer roller 12.
In other respects, the constitution and effects of the image forming apparatus in the fifth embodiment are the same as those of the fourth embodiment. In this case, the second transfer material presence/absence detector 39 can be located at any one of the inner side of the endless shaped transfer material transport belt 29a of the transfer material transporter 29, the third air flow generator 30, the front side of the image fixing section 31, and the rear side of the image fixing section 31.
Moreover, the image forming apparatus and the image forming method of the invention are not limited to the above described preferred embodiments. For example, in the above described embodiments, the intermediate transfer belt 8 is used as the image carrier, however, the intermediate transfer drum or photo sensor can be used as the image carrier. In the case where a photosensitive body is applied as the image carrier, the toner image of the photosensitive body is directly transferred to the transfer material. Also, the image forming apparatus has 4 colors; however the image forming apparatus may have a single color.
With the image forming apparatus according to the illustrated embodiments, there is provided an image forming apparatus and the image forming method. An elastic member is installed in the circumferential surface of the transfer roller having a concaved portion, along with which a transfer nip formation area is formed where the transfer roller is pressed against the image carrier when the image is transferred. In this case, the width of the concaved portion is larger than the width of the transfer nip formation area in the circumferential direction of the transfer roller. The transfer roller is stopped when the concaved portion is in the transfer nip formation area, so as not to have contact between the transfer roller and the image carrier when the image is not transferred. Thus, the transfer nip is not formed in the transfer nip formation area between the transfer roller and the image carrier when the image forming operation of the image forming apparatus is not performed. Accordingly, the elastic member of the transfer roller is not twisted, even when the image forming apparatus is not operated for a long time. Thus, the image defect and the occurrence of the banding caused by the twisting of the elastic member are suppressed effectively and a higher quality image can be obtained.
In addition, when the rotation of the transfer roller is stopped, the concaved portion is reliably positioned on the transfer nip formation area so that the transfer roller can be reliably stopped in a constant position. Accordingly, the rotational position of the transfer roller can be controlled when the next image forming operation is performed, and the positional alignment between the rotational position of the transfer roller and the transfer material which is transported to the apparatus is easily accomplished.
Additionally, each rotation of the image carrier driver driving the image carrier and the transfer roller driver driving the transfer roller may be controlled independently, so that the rotation velocity of the image carrier driver and the transfer roller driver can be controlled properly and individually.
Also, the elastic member of the transfer roller is not in contact with the image carrier when the image carrier is driven and the transfer roller driver is stopped. In the state in which the elastic member is not in contact with the image carrier, unstable sliding between the elastic member of the transfer roller and the image carrier can be suppressed when the image carrier starts to rotate independently or when the image carrier is stopped after rotating independently.
Also, in the state in which the rotation of the transfer roller is stopped, the image carrier can be rotated in the state that the elastic member of the transfer roller is not in contact with the image carrier by placing the concaved portion in the transfer nip formation area. However, in the case that the transfer roller of the image forming apparatus is always in press-contact with the image carrier, it is necessary for the transfer roller to be separated from the image carrier to change the distance between the rotational axis of the transfer roller and the rotational axis of the image carrier, when the image carrier is cleaned or registration alignment thereof is performed. Meanwhile, the image transfer apparatus of the illustrated embodiments has a transfer roller separating from the image carrier without substantially changing the distance between the rotational axis of the transfer roller and the rotational axis of the image carrier. Thus, the operation as described above can be accomplished with easily and quickly.
In addition, when a jam of the transfer material occurs, the controller stops the rotation of the transfer roller so that the concaved portion is located in the transfer nip formation area, on the basis of the transfer roller position signal and the transfer presence/absence signal from the transfer presence/absence detecting section. Accordingly, it can be suppressed that the toner of the image being carried by the image carrier is attached on the transfer roller. In particular, by setting the location of the transfer material detecting timing position of the transfer material presence/absence detecting section to immediately upstream of the concaved portion detecting position (the position of the concaved portion when the concaved portion is placed in the transfer nip formation area) on the front of the transfer roller position, the toner of the image being carried by the image carrier can be more effectively suppressed from being attached on the transfer roller.
Also, when a jam of the transfer material passing through the transfer nip at the transfer presence/absence detecting section is detected, the controller stops the reverse rotation of the transfer roller when the concaved portion is located on the transfer nip position after reverse rotation of the transfer roller, on the basis of the transfer roller position signals and the transfer material presence/absence signals of the transfer presence/absence detecting section. Accordingly, it can be more effectively suppressed that the toner of the image being carried by the image carrier is attached on the transfer roller.
Also, in the state in which the transfer material is pinched by the transfer material gripper, the transfer material passes through the transfer nip, so that separation of the transfer material from the image carrier can be reliably accomplish after the image is transferred.
Also, the image carrier has an elastic layer, so that the transfer efficiency can be enhanced even though the transfer material has high surface roughness. Even if this image carrier has the elastic layer, the transfer nip is not formed in the case that the image carrier and the transfer roller is stopped for a long time, so that it is possible to suppress the occurrence of twisting occurrence between the elastic layer of the image carrier and the elastic layer of the transfer roller.
In understanding the scope of the present invention, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts. Finally, terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. For example, these terms can be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies.
While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. Furthermore, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
| Number | Date | Country | Kind |
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| 2009-160668 | Jul 2009 | JP | national |
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| Number | Date | Country | |
|---|---|---|---|
| 20110008079 A1 | Jan 2011 | US |
