Transfer device and image forming apparatus including photoconductors, a belt, and primary transfer rollers

A transfer device includes a plurality of photoconductors, a belt, a plurality of primary transfer rollers and control circuitry. The plurality of primary transfer rollers is disposed for the plurality of photoconductors, respectively. The plurality of primary transfer rollers brings the belt into contact with or separate the belt from the plurality of photoconductors. The control circuitry causes at least one of the plurality of primary transfer rollers to press against a corresponding at least one of the plurality of photoconductors to shift a printing mode.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2021-127759, filed on Aug. 3, 2021, in the japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.

BACKGROUND

Technical Field

Embodiments of the present disclosure relate to a transfer device and an image forming apparatus.

Related Art

In the related art, a full-color tandem-type image forming apparatus is known that performs full-color image formation. For example, the full-color tandem-type image forming, apparatus employs a method of image formation using five image forming units including four image forming units of yellow (Y), magenta (M), cyan (C), and black (K) toners, and one more image forming unit of foaming toner for braille, fluorescent toner, transparent toner for improving gloss, or ferromagnetic toner.

When the image forming apparatus switches from a full-color mode to a special monochrome mode and a large number of sheets is to be printed in the special monochrome mode after the switching, the image forming apparatus separates the image forming units of yellow (Y), magenta (M), and cyan (C) toners from an intermediate transfer unit and stops the operations of the image forming units. Thus, the image forming apparatus controls a separating operation of primary transfer rollers in accordance with the number of sheets to be printed at the time of switching, A technique in the related art is known to prevent a failure that is likely to occur at the time of switching an image mode by such control described above so that the service life and productivity of the image forming units are enhanced.

SUMMARY

Embodiments of the present disclosure described herein provide a novel transfer device including a plurality of photoconductors, a belt, a plurality of primary transfer rollers and control circuitry. The plurality of primary transfer rollers is disposed for the plurality of photoconductors, respectively. The plurality of primary transfer rollers brings the belt into contact with or separate the belt from the plurality of photoconductors. The control circuitry causes at least one of the plurality of primary transfer rollers to press against a corresponding at least one of the plurality of photoconductors to shift a printing mode.

Embodiments of the present disclosure described herein provide a novel image forming apparatus including the transfer device.

DETAILED DESCRIPTION

Descriptions are given of a transfer device and an image forming apparatus according to an embodiment of the present disclosure, with reference to the following figures. Note that the embodiments are not limited to the specific examples described below.

Example of Image Forming Apparatus

FIG.1is a schematic diagram illustrating an example of a hardware configuration of an image forming apparatus1.

The image forming apparatus1includes an operation panel201, a transfer device10, a secondary transfer roller207, a sheet feeding device209, a conveyance roller pair202, a fixing roller pair204, a sheet reverse passage206, and an output tray301.

The operation panel201is an operation display unit that enables a user to input various operations to the image forming apparatus1and displays various screens.

The transfer device10includes five photoconductors11to15and a belt16. A toner image is formed on each of the photoconductors11to15by an image forming process (a charging process, an exposing process, a developing process, a transfer process, and a cleaning process). The toner image formed on each of the photoconductors11to15is transferred onto the belt16. After the toner images of the photoconductors11to15are transferred onto the belt16while being superimposed on top of another, the belt16conveys the composite toner image (full-color toner image) to a secondary transfer position of the secondary transfer roller207.

The sheet feeding device209accommodates a plurality of recording media to be processed (a conveyed objects) in a superposed manner and feeds each recording medium of the plurality of recording media one by one. Examples of the recording medium include recording paper (transfer paper), However, the recording medium is not limited to this, and examples of the recording medium ma include media capable of recording images such as coated paper, thick paper, overhead projector (OUP) sheets, plastic films, and copper foil.

The conveyance roller pair202conveys the recording medium fed by the sheet feeding device209in a direction indicated by arrow “s” on a conveyance passage “a”.

The secondary transfer roller207collectively transfers the full-color toner image conveyed by the belt16onto the recording medium conveyed by the conveyance roller pair202at the secondary transfer position.

The fixing roller pair204fixes the full-color toner image on the recording medium by heating and pressurizing the recording medium onto which the full-color toner image is transferred.

In the case of single-sided printing, the image forming apparatus1sends a printed material, which is the recording medium on which the fill-color toner images are fixed, to the output tray301. In the case of double-sided printing, the image forming apparatus1sends the recording medium, on which the full-color toner images have been fixed, to the sheet reverse passage206.

By switching back the fed recording medium, the front and back faces of the recording medium are reversed in the sheet reverse passage206. Then, the reversed recording medium is conveyed in the direction of the arrow “t”. After the recording medium conveyed through the sheet reverse passage206is conveyed again by the conveyance roller pair202, a full-color toner image is transferred onto the back face of the recording medium opposite to the previously transferred face (front face) by the secondary transfer roller207. The transferred full-color toner image transferred on the back face of the recording medium is fixed to the back face by the fixing roller pair204, and the recording medium is sent as printing material to the output tray301. The output tray301stacks the recording medium ejected through the conveyance passage “a”.

Example of Transfer Device

FIG.2is a diagram illustrating an example of a transfer device. For example, the transfer device10includes the five photoconductors. The five photoconductors are referred to as a first photoconductor11, a second photoconductor12, a third photoconductor13, a fourth photoconductor14, and a fifth photoconductor15in order from the right inFIG.2.

The five photoconductors are separately disposed for different colors. Specifically, the first photoconductor11is for black (K). The second photoconductor12is for cyan (C). The third photoconductor13is for magenta (M). The fourth photoconductor14is for yellow (Y).

The fifth photoconductor15is for a special (S) color. The special color is, for example, white image, clear, or a color other than C, M, Y, and K.

Note that the order of the photoconductors is not limited to the order illustrated inFIG.2. For example, the order of the first photoconductor11and the fifth photoconductor15may be switched. The photoconductors may have colors other than the colors illustrated inFIG.2.

The transfer device10includes the belt16. The belt16has an endless loop wound around multiple rollers.

The transfer device10preferably includes an optical sensor17. For example, the optical sensor17is disposed close to the belt16. In other words, the optical sensor17is disposed at a position where the optical sensor17detects marks formed on the belt16. Note that the optical sensor17may be disposed at a position other than the position illustrated inFIG.2. For example, the optical sensor17may be disposed near the fifth photoconductor15.

Preferably, the transfer device10further includes a support18. Note that the support18may be disposed at a position other than that illustrated inFIG.2. For example, the support18serves as a driven roller. However, the support18may serve as a driving roller.

The transfer device10preferably includes a driving roller19. For example, the driving roller19is an actuator such as a motor. The driving roller19rotates to convey the belt16. Note that the driving roller19may be disposed at a position other than the position illustrated inFIG.2. Further, the transfer device10may include a plurality of driving rollers including the driving roller19.

The transfer device10includes a primary transfer roller for each photoconductor. Each primary transfer roller is disposed so as to nip the belt16with a corresponding photoconductor. A first primary transfer roller21is disposed facing the first photoconductor11via the belt16. A second primary transfer roller22is disposed facing the second photoconductor12via the belt16. A third primary transfer roller23is disposed facing the third photoconductor13via the belt16. A third primary transfer roller24is disposed facing the fourth photoconductor14via the belt16. A fifth primary transfer roller25is disposed facing the fifth photoconductor15via the belt16.

The transfer device10includes a controller20. The controller20is an example of an arithmetic unit and a control unit. The transfer device10may include a plurality of arithmetic units and a plurality of control units.

The transfer device10may further include devices other than the devices illustrated inFIG.2.

Examples of States of Photoconductor, Belt, and Primary Transfer Roller

For example, the photoconductor, the belt, and the primary transfer roller of the transfer device10change the positions depending on the type of printing.

FIG.3is a diagram illustrating an example of the positions of the parts in a non-printing state. When printing is not performed, for example, the belt16is separated from each of the first photoconductor11to the fifth photoconductor15. As illustrated inFIG.3, none of the first photoconductor11to the fifth photoconductor15is in contact with the belt16in the non-printing state. This state may be referred to as a “fully separated state”.

Further, a distance between the optical sensor17and the belt16in the fully separated state is referred to as a “first distance31”.

FIG.4is a diagram illustrating an example of a first printing state. As compared to the non-printing printing state, the first printing state is different from the non-printing state in that the first photoconductor11and the belt16are in contact with each other.

In the first printing state, the belt16is lifted by the first primary transfer roller21. In this state, printing by the first photoconductor11may be performed. In other words, printing in black may be performed.

In the first printing state, the distance between the optical sensor17and the belt16is different from that in the fully separated state. The distance between the optical sensor17and the belt16in the first printing state is referred to as a “second distance32”.

FIG.5is a diagram illustrating an example of a second printing state. As compared to the first printing state, the second photoconductor12, the third photoconductor13, and the fourth photoconductor14are further in contact with the belt16in the second printing state.

In the second printing state, the belt16is lifted by the first primary transfer roller21, the second primary transfer roller22, the third primary transfer roller23, and the fourth primary transfer roller24. In this state, printing in both black and full color may be performed using the first photoconductor11to the fourth photoconductor14.

Further, the distance between the optical sensor17and the belt16in the second printing state corresponds to the second distance32as in the first printing state.

FIG.6is a diagram illustrating an example of a third printing state. As compared to the second printing state, the fun photoconductor15is further in contact with the belt16in the third printing state.

In the third printing state, the belt16is lifted by the first primary transfer roller21, the second primary transfer roller22, the third primary transfer roller23, the fourth primary transfer roller24, and the fifth primary transfer roller25. In this state, printing in each of black, full color, and special color may be performed using the first photoconductor11to the fifth photoconductor15.

Further, the distance between the optical sensor17and the belt16in the third printing state corresponds to the second distance32as in the first printing state.

FIG.7is a diagram illustrating an example of a fourth printing state. As compared to the third printing state, the fifth photoconductor15is in contact with the belt16and the rest of the photoconductors (i.e., the first photoconductor11to the fourth photoconductor14) are separated from the belt16in the fourth printing state.

In the fourth printing state, the belt16is lifted by the fifth primary transfer roller25. In this state, printing in special color may be performed using the fifth photoconductor15.

In the fourth printing state, the distance between the optical sensor17and the belt16is different from the distance in the first printing state. The distance between the optical sensor17and the belt16in the fourth printing state is referred to as a “third distance33”.

FIG.8is a diagram illustrating an example of a fifth printing state. As compared to the fourth printing state, each of the second photoconductor12to the fifth photoconductor15is in contact with the belt16and the first photoconductor11is separated from the belt16in the fifth printing state.

In the fifth printing state, the belt16is lifted by the second primary transfer roller22to the fifth primary transfer roller25. In this state, printing in both full color and special color may be performed using the second photoconductor12, the third photoconductor13, the fourth photoconductor14, and the fifth photoconductor15.

In the fifth printing state, the distance between the optical sensor17and the belt16is different from the distance in the first printing state. The distance between the optical sensor17and the belt16in the fifth printing state is referred to as a “fourth distance34”.

Changing the distance between the optical sensor17and the belt16, for example, the first distance31to the fourth distance34, may cause the following results.

FIG.9is a diagram illustrating an example of placing marks on a belt. For example, marks40are placed on the back side of the belt16, which is the lower side in the Z-axis of the belt16, as illustrated inFIG.9.

The results of the reading by the optical sensor17depend on the distance between the optical sensor17and the belt16as described below.

FIG.10is a diagram illustrating an example of the result of the reading the marks40at an appropriate distance. For example, a description is given of an example of the reading result of a mark40appropriately set with the second distance32. In other words, it is assumed that the optical sensor17is in focus at the second distance32.

In such a setting, the outline of the mark40is clearly read at the second distance32as illustrated inFIG.10, i.e., in any one of the first printing state, the second printing state, and the third printing state.

FIG.11is a diagram illustrating an example of a result of reading the marks40at an inappropriate distance. In a case where the distance is other than the second distance32, the outline of the mark40is not clearly read as illustrated inFIG.11.

For example, a conveyance speed of the belt16is calculated based on the number of marks40detected per unit time. Due to this configuration, in a case where the outline of the mark40is unclear and the detection result is unstable, the calculation result may be unstable. On the other hand, in a case where the outline of the mark40is clear as illustrated inFIG.10, the mark40may be detected with high accuracy.

Thus, it is preferable that the distance between the optical sensor17and the belt16is changed by, for example, moving the optical sensor17, as described below.

FIG.12is a diagram illustrating an example of a mechanism for operating the optical sensor17and the first primary transfer roller21. For example, the transfer device10includes a cam50and a bearing51that are moved as described below. A description is given of an example of the primary transfer roller with the first primary transfer roller21.

FIG.13is a diagram illustrating an example of the mechanism where the optical sensor17and the first primary transfer roller21are moved. As the cam50makes a half turn, the state illustrated inFIG.12is changed to the state illustrated inFIG.13. In response to this half turn, the cam50pushes the bearing51(toward the left direction inFIG.13. The bearing51is embedded in a sheet metal52. Due to this configuration, when the bearing51is pushed by the cam50, the sheet metal52slides. As the sheet metal52is slid in this manner, the first primary transfer roller21may bring the belt16into contact with or separate the belt16from the first photoconductor11.

At the same time, the optical sensor17moves in accordance with the slide of the sheet metal52. Specifically, as the first primary transfer roller21moves upward inFIG.13, the optical sensor17moves downward inFIG.13. As described above, the mechanism moves the optical sensor17and the first primary transfer roller21in vertically opposite directions.

In other words, the mechanism illustrated in theFIG.12andFIG.13includes a single driving source that operates for rotating the cam50. The single driving source may be an actuator such as a motor. As described above, it is preferable that the optical sensor17and the first primary transfer roller21share a common driving source.

Employing such a common driving source can reduce the number of parts of the driving source. Such a reduction in the number of parts of the driving source may reduce the cost of the transfer device10. Further, the reduction in the number of parts of the driving source may reduce the space in the transfer device10.

In a case where the first primary transfer roller21is at the fixed position, the optical sensor17is also at the fixed position. As described above, if the distance between the optical sensor17and the belt16is not changed, the initial position of the optical sensor17is set to an appropriate distance for detecting the mark40. Then, the optical sensor17senses a target such as the marks through a lens and acquires an image of the target. In the fully separated state, the distance between the belt16and the optical sensor17is changed from the initial position. Then, the target in the correct focus at the initial position becomes out of focus. As a result, the outline of the mark40becomes unclear, which makes it difficult to clearly read the mark40. Thus, in the fully separated state, the outline of the mark40may be difficult to be clearly read. To address this inconvenience, it is preferable to avoid the fully separated state.

Example of Mode Shift

The mode refers to, for example, a method of performing image formation in color, monochrome, special color, or a combination of the colors. Descriptions are given of an example of the shift from a mode for printing with the first photoconductor11to a mode for priming with the second photoconductor12, the third photoconductor13, the fourth photoconductor14, and the fifth photoconductor15. In other words, when the mode is shifted from the first printing state to the fifth printing state, the primary transfer roller is controlled so as to perform a first sequence as described below.

Example of First Sequence

FIG.14is a diagram illustrating an example of the first sequence (part 1). First, the first printing state is a state as illustrated inFIG.4. Next, the transfer device10brings each of the first photoconductor11to the fifth photoconductor15into contact with the belt16as described below. Broken lines inFIGS.14to57indicate whether the photoconductors are separated from the belt16or are in contact with the belt16.

FIG.15is a diagram illustrating an example of the first sequence (part 2). Next, the transfer device10separates the first photoconductor11from the belt16as described below.

FIG.16is a diagram illustrating an example of the first sequence (part 3).

With the first sequence as illustrated inFIGS.14and15, the transfer device10may shift the mode from the first printing state to the fifth printing state.

As illustrated inFIGS.14to16, the transfer device10causes at least one of the five primary transfer rollers to press against the photoconductor, to shift the mode even in any state in the first sequence. In other words, the transfer device10shifts the mode to avoid the fully separated state illustrated inFIG.3in the first sequence.

Since the image forming system is turned off in the fully separated state, continuous printing is often stopped. As a result, if the first sequence includes the fully separated state, continuous printing may not be performed, resulting in a reduced productivity.

On the other hand, in a case where at least one of the five primary transfer rollers is pressed against the photoconductor to shift the mode, the productivity of the transfer device10may be enhanced.

In a case where the mode is shifted from the first printing state through the fifth printing state, the transfer device10may perform control in any one of a second sequence to a fifth sequence described below.

Example of Second Sequence

FIG.17is a diagram illustrating an example of the second sequence (part 1). First, the first printing state is a state as illustrated inFIG.14. Next, the transfer device10brings the fifth photoconductor15into contact with the belt16as described below.

FIG.18is a diagram illustrating an example of the second sequence (part 2). Next, the transfer device10brings each of the second photoconductor12to the fourth photoconductor14into contact with the belt16as described below.

FIG.19is a diagram illustrating an example of the second sequence (part 3). Next, the transfer device10separates the first photoconductor11from the belt16as described below.

FIG.20is a diagram illustrating an example of the second sequence (part 4).

With the second sequence as illustrated inFIGS.17,18and19, the transfer device10may shift the mode from the first printing state to the fifth printing state.

As illustrated inFIGS.17to20, the transfer device10causes at least one of the five primary transfer rollers to press against the photoconductor to shift the mode even in any state in the second sequence. In other words, the transfer device10shifts the mode to avoid the fully separated state illustrated inFIG.3in the second sequence.

When the mode is shifted by the second sequence, the productivity of the transfer device10may be enhanced.

Example of Third Sequence

FIG.21is a diagram illustrating an example of a third sequence (part 1). First, the first printing state is a state as illustrated inFIG.14. Next, the transfer device10brings each of the second photoconductor12to the fourth photoconductor14into contact with the belt16as described below.

FIG.22is a diagram illustrating an example of the third sequence (part 2). Next, the transfer device10brings the fifth photoconductor15into contact with the belt16as described below.

FIG.23is a diagram illustrating an example of the third sequence (part 3). Next, the transfer device10separates the first photoconductor11from the belt16as described below.

FIG.24is a diagram illustrating an example of the third sequence (part 4).

With the third sequence as illustrated inFIGS.21,22and23, the transfer device10may shift the mode from the first printing state to the fifth printing state.

As illustrated inFIGS.21to24, the transfer device10causes at least one of the five primary transfer rollers to press against the photoconductor to shift the mode even in any state in the third sequence. In other words, the transfer device10shifts the mode to avoid the fully separated state illustrated inFIG.3in the third sequence.

When the mode is shifted by the third sequence, the productivity of the transfer device10may be enhanced.

Example of Fourth Sequence

FIG.25is a diagram illustrating an example of a fourth sequence (part 1). First, the first printing state is a state as illustrated inFIG.14. Next, the transfer device10brings the fifth photoconductor15into contact with the belt16as described below.

FIG.26is a diagram illustrating an example of the fourth sequence (part 2). Next, the transfer device10separates the first photoconductor11from the belt16as described below.

FIG.27is a diagram illustrating an example of the fourth sequence (part 3). Next, the transfer device10brings each of the second photoconductor12to the fourth photoconductor14into contact with the belt16as described below.

FIG.28is a diagram illustrating an example of the fourth sequence (part 4).

With the fourth sequence as illustrated inFIGS.25,26and27, the transfer device10may shift the mode from the first printing state to the fifth printing state.

As illustrated inFIGS.25to28, the transfer device10causes at least one of the five primary transfer rollers to press against the photoconductor to shift the mode even in any state in the fourth sequence. In other words, the transfer device10shills the mode to avoid the fully separated state illustrated inFIG.3in the fourth sequence.

When the mode is shifted by the fourth sequence, the productivity of the transfer device10may be enhanced.

Example of Fifth Sequence

FIG.29is a diagram illustrating an example of the fifth sequence (part 1). First, the first printing state is a state as illustrated inFIG.14. Next, the trans r device10brings each of the second photoconductor12to the fourth photoconductor14into contact with the belt16as described below.

FIG.30is a diagram illustrating an example of the fifth sequence (part 2). Next, the transfer device10separates the first photoconductor11from the belt16as described below.

FIG.31is a diagram illustrating an example of the fifth sequence (part 3). Next, the transfer device10brings the fifth photoconductor15into contact with the belt16as described below.

FIG.32is a diagram illustrating an example of the fifth sequence (part 4).

With the fifth sequence as illustrated inFIGS.29,30and31, the transfer device10may shift the mode from the first printing state to the filth priming state.

As illustrated inFIGS.29to32, the transfer device10causes at least one of the five primary transfer rollers to press against the photoconductor to shift the mode even in any state in the fifth sequence. In other words, the transfer device10shifts the mode to avoid the fully separated state illustrated inFIG.3in the fifth sequence.

When the mode is shifted by the fifth sequence, the productivity of the transfer device10may be enhanced.

The mode shift is not limited to the shift from the first printing state to the fifth printing state. For example, the mode shift may be the shift from the fifth priming state to the first printing state. Specifically, the transfer device10may shift the mode with a sixth sequence to a ninth sequence as described below.

Example of Sixth Sequence

FIG.33is a diagram illustrating an example of the sixth sequence (part 1). First, the fifth printing state is a state as illustrated inFIG.8. Next, the transfer device10brings the first photoconductor11into contact with the belt16as described below.

FIG.34is a diagram illustrating an example of the sixth sequence (part 2). Next, the transfer device10separates each of the second photoconductor12to the fourth photoconductor14from the belt16as described below.

FIG.35is a diagram illustrating an example of the sixth sequence (part 3). Next, the transfer device10separates the fifth photoconductor15from the belt16as described below.

FIG.36is a diagram illustrating an example of the sixth sequence (part 4).

With the sixth sequence as illustrated inFIGS.33,34and35, the transfer device10may shift the mode from the fifth printing state to the first printing state.

As illustrated inFIGS.33to36, the transfer device10causes at least one of the five primary transfer rollers to press against the photoconductor to shift the mode even in any state in the sixth sequence. In other words, the transfer device10shifts the mode to avoid the fully separated state illustrated inFIG.3in the sixth sequence.

When the mode is shifted by the sixth sequence, the productivity of the transfer device10may be enhanced.

Example of Seventh Sequence

FIG.37is a diagram illustrating an example of a seventh sequence (part 1). First, the fifth printing state is a state as illustrated inFIG.8. Next, the transfer device10brings the first photoconductor11into contact with the belt16as described below.

FIG.38is a diagram illustrating an example of the seventh sequence (part 2). Next, the transfer device10separates the fifth photoconductor15from the belt16as described below.

FIG.39is a diagram illustrating an example of the seventh sequence (part 3). Next, the transfer device10separates each of the second photoconductor12to the fourth photoconductor14from the belt16as described below.

FIG.40is a diagram illustrating an example of the seventh sequence (part 4).

With the seventh sequence as illustrated inFIGS.37,38and39, the transfer device10may shift the mode from the fifth printing state to the first printing state.

As illustrated inFIGS.37to40, the transfer device10causes at least one of the five primary transfer rollers to press against the photoconductor to shift the mode even in an state in the seventh sequence. In other words, the transfer device10shifts the mode to avoid the fully separated state illustrated inFIG.3in the seventh sequence.

When the mode is shifted by the seventh sequence, the productivity of the transfer device10may be enhanced.

Example of Eighth Sequence

FIG.41is a diagram illustrating an example of an eighth sequence (part 1). First, the fifth printing state is a state as illustrated inFIG.8. Next, the transfer device10separates each of the second photoconductor12to the fourth photoconductor14from the belt16as described below.

FIG.42is a diagram illustrating an example of the eighth sequence (part 2). Next, the to device10brings the first photoconductor11into contact with the belt16as described below.

FIG.43is a diagram illustrating an example of the eighth sequence (part 3). Next, the transfer device10separates the fifth photoconductor15from the belt16as described below.

FIG.44is a diagram illustrating an example of the eighth sequence (part 4).

With the eighth sequence as illustrated inFIGS.41,42and43, the transfer device10may shift the mode from the fifth printing state to the first printing state.

As illustrated inFIGS.41to44, the transfer device10causes at least one of the five primary transfer rollers to press against the photoconductor to shift the mode even in any state in the eighth sequence. In other words, the transfer device10shifts the mode to avoid the fully separated state illustrated inFIG.3in the eighth sequence.

When the mode is shifted by the eighth sequence, the productivity of the transfer device10may be enhanced.

Example of Ninth Sequence

FIG.45is a diagram illustrating an example of the ninth sequence (part 1). First, the fifth printing state is a state as illustrated inFIG.8. Next, the transfer device10separates the fifth photoconductor15from the belt16as described below.

FIG.46is a diagram illustrating an example of the ninth sequence (part 2). Next, the transfer device10brings the first photoconductor11into contact with the belt16as described below.

FIG.47is a diagram illustrating an example of the ninth sequence (part 3). Next, the transfer device10separates each of the second photoconductor12to the fourth photoconductor14from the belt16as described below.

FIG.48is a diagram illustrating an example of the ninth sequence (part 4).

With the ninth sequence as illustrated inFIGS.45,46and47, the transfer device10may shift the mode from the fifth printing state to the first printing state.

As illustrated inFIGS.45to48, the transfer device10causes at least one of the five primary transfer rollers to press against the photoconductor to shift the mode even in any state in the ninth sequence. In other words, the transfer device10shifts the mode to avoid the fully separated state illustrated inFIG.3in the ninth sequence.

When the mode is shifted by the ninth sequence, the productivity of the transfer device10may be enhanced.

Example of Tenth Sequence

Descriptions are given of an example of the shill from a mode for priming with the first photoconductor11to a mode for printing with the fifth photoconductor15. In other words, while the mode is shifted from the first printing state to the fourth printing state, the primary transfer roller is controlled so as to perform a tenth sequence as described below.

FIG.49is a diagram illustrating an example of the tenth sequence (part 1). First, the first printing state is a state as illustrated inFIG.4. Next, the transfer device10brings the fifth photoconductor15into contact with the belt16as described below.

FIG.50is a diagram illustrating an example of the tenth sequence (part 2). Next, the transfer device10separates the first photoconductor11from the belt16as described below.

FIG.51is a diagram illustrating an example of the tenth sequence (part 3).

With the tenth sequence as illustrated inFIGS.49and50, the transfer device10may shill the mode from the first printing state to the fourth printing state.

As illustrated inFIGS.49to51, the transfer device10causes at least one of the five primary transfer rollers to press against the photoconductor to shift the mode even in any state in the tenth sequence. In other words, the transfer device10shifts the mode to avoid the fully separated state illustrated inFIG.3in the tenth sequence.

When the mode is shifted by the tenth sequence, the productivity of the transfer device10may be enhanced.

Example of Eleventh Sequence

Descriptions are given of an example of the shift from a mode for printing with the fifth photoconductor15to a mode for printing with the first photoconductor11. In other words, while the mode is shifted from the fourth printing state to the first printing state, the primary transfer roller is controlled so as to perform an eleventh sequence as described below.

FIG.52is a diagram illustrating an example of the eleventh sequence (part 1). First, the fourth printing state is a state as illustrated inFIG.7. Next, the transfer device10brings the first photoconductor11into contact with the belt16as described below.

FIG.53is a diagram illustrating an example of the eleventh sequence (part 2). Next, the transfer device10separates the fifth photoconductor15from the belt16as described below.

FIG.54is a diagram illustrating an example of the eleventh sequence (part 3).

With the eleventh sequence as illustrated inFIGS.52and53, the transfer device10may shift the mode from the fourth printing state to the first printing state.

As illustrated inFIGS.52to54, the transfer device10causes at least one of the five primary transfer rollers to press against the photoconductor to shift the mode even in any state in the eleventh sequence. In other words, the transfer device10shifts the mode to avoid the fully separated state illustrated inFIG.3in the eleventh sequence.

When the mode is shifted by the eleventh sequence, the productivity of the transfer device10may be enhanced.

Control Sample

Descriptions are given of a sequence of a control sample where the mode is shifted from the first printing state to the fifth printing state.

FIG.55is a diagram illustrating a sequence (part 1) of the control sample. First, the first printing state is a state as illustrated inFIG.4. Next, the transfer device10separates the first photoconductor11from the belt16. As a result, each of the photoconductors is separated, as described below.

FIG.56is a diagram illustrating the sequence (part 2) of the control sample. As illustrated inFIG.56, the transfer device10turns off the image forming system in the fully separated state, it is difficult to perform a printing in this state.

After the image forming system is started up, the transfer device10brings each of the second photoconductor12to the fifth photoconductor15into contact with the belt16as described below.

FIG.57is a diagram illustrating the sequence (part 3) of the control sample.

If the fully separated state illustrated inFIG.3occurs in the sequence illustrated inFIGS.55to57, the transfer device10is likely to reduce the productivity due to the turning off of the image forming system.

Control Example

FIG.58is a diagram illustrating a control example based on the conveyance speed. For example, as illustrated inFIG.58, it is preferable that the transfer device10is configured to perform feedback control of the conveyance speed.

Specifically, the transfer device10causes the optical sensor17to detect the marks40provided on the belt16. Next, the transfer device10calculates a speed at which the belt16is conveyed, i.e., the conveyance speed of the belt16, based on the detection result. Then, the calculation result is fed back and a conveyance speed controller41controls the conveyance speed to bring the conveyance speed closer to a target conveyance speed. Due to such a configuration, the transfer device10controls the conveyance speed to maintain a constant speed.

Further, it is preferable that the transfer device10controls the conveyance speed in real time. The constant conveyance speed can reduce color shift or positional deviation. As a result, a high-quality image may be formed.

Installation Example of Optical Sensor

FIG.59is a diagram illustrating an installation example of the optical sensors. Optical sensors17may be installed, for example, at respective positions as illustrated inFIG.59. A plurality of optical sensors17may be installed.

It is preferable that each of the optical sensors17is installed near the primary transfer roller or a support that supports the belt16. Specifically, it is preferable that each of the optical sensors17is installed at a position within 10 centimeters (cm) from the primary transfer, roller or the support that supports the belt16.

Due to the above-described configuration, in a case where the optical sensor17is installed near the primary transfer roller or the support that supports the belt16, erroneous detection of the marks40due to fluctuation caused by the belt16may be reduced.

Example of Configuration for Changing Distance

FIG.60is a diagram illustrating an example of a configuration of changing the distance between the optical sensor17and the belt16. It is preferable that the transfer device10is configured to change the distance between the optical sensor17and the belt16. Specifically, it is preferable that the transfer device10includes an actuator that moves the optical sensor17in the Z-axis direction inFIG.60.

The distance between the optical sensor17and the belt16is changed by switching between contact and separation of the photoconductors and the belt16by the primary transfer rollers. Due to this configuration, it is preferable that the transfer device10is configured to adjust the distance between the optical sensor17and the belt16to an appropriate distance. Note that the appropriate distance is, for example, a distance at which the optical sensor17is in focus. Therefore, the appropriate distance is determined by optical condition of each optical sensor17.

Example of Control by Rotational Speed

FIG.61is a diagram illustrating an example of a mechanism of measuring the rotational speed. The belt16rotates as a driving motor60serving as a driving source rotates the driving roller19. For example, an encoder61is disposed on the shaft of the driving roller19. Based on the rotational speed measured in this manner, for example, the control may be performed as described below.

FIG.62is a diagram illustrating an example of the control based on the rotational speed of the driving roller19. As illustrated inFIG.62, providing the encoder61on the shaft of the driving roller19allows measurement of the rotational speed of the driving roller19. When the measurement result by the encoder61is fed back, a rotation speed controller42performs the control based on the rotational speed of the driving roller19.

The rotation speed controller42may further perform the control based an a differential system of the rotational speed of the driving roller19.

Further, as illustrated inFIG.62, the transfer device10may provide feedback on both the conveyance speed of the belt16and the rotational speed of the driving roller19using the conveyance speed controller41and the rotation speed controller42. Providing feedback on both the conveyance speed of the belt16and the rotational speed of the driving roller19allows highly accurate control.

Note that the transfer device10may further include a switcher62. For example, when the switcher62sets the output to zero (0), the transfer device10switches to provide the feedback on the rotational speed of the driving roller19without providing, the feedback on the conveyance speed of the belt16. The switching of the feedback is performed, for example, by the process described below.

Example of Switching

FIG.63is a flowchart of a first example of switching feedback.

The transfer device10controls the primary transfer roller (step S6201). Specifically, the transfer device10controls the plurality of primary transfer rollers so that the primary transfer rollers are separated from the belt16or are brought into contact with the belt16in accordance with the mode.

The transfer device10determines whether the state is the fully separated state (step S6202). Next, when the transfer device10determines that the state is the fully separated state (YES in step S6202), the transfer device10proceeds to step S6203. When the transfer device10determines that the state is not the fully separated state (NO in step S6202), the transfer device10ends the process.

The transfer device10switches to provide the feedback on the rotational speed alone (step S6203).

For example, it is difficult to detect the marks40in the fully separated state. In such a case, the transfer device10controls by providing the feedback on the rotational speed without providing the feedback on the conveyance speed of the belt16.

Due to the above-described configuration, the control based on the result of erroneous detection is prevented, and the transfer device10may perform control based on the rotational speed. By so doing, the transfer device10may prevent quality deterioration in in formation.

FIG.64is a flowchart of a second example of switching feedback.

The transfer device10determines whether the feedback is provided on both the conveyance speed of the belt16and the rotational speed of the driving roller19(step S6301). Next, when the transfer device10determines that the feedback is provided on both the conveyance speed of the belt16and the rotational speed of the driving roller19(YES in step S6301), the transfer device10proceeds to step S6302. When the transfer device10determines that the feedback is not provided on both the conveyance speed of the belt16and the rotational speed of the driving roller19(NO in step S6301), the transfer device10ends the process.

The transfer device10determines whether the output of the sensor is less than or equal to a certain value (step S6302). Next, when the transfer device10determines that the output of the sensor is less than or equal to the certain value (YES in step S6302), the transfer device10proceeds to step S6303. When the transfer device10determines that the output of the sensor is greater than the certain value (NO in step S6302), the transfer device10ends the process.

For example, the output of the optical sensor17decreases if a scattering of toner or a failure occurs. In other words, in a case where the output of the sensor is relatively weak, the transfer device10determines that the scattering of toner or the failure occurs.

Note that the certain value serving as a criterion for determination i.e., the threshold is set in advance.

The transfer device10switches to provide the feedback on the rotational speed alone (step S6303).

When the output of the sensor is decreased, it is difficult to detect the mark40due to occurrence of the scattering of toner or the failure. In such a case, erroneous detection of the marks40is likely to occur. To address this inconvenience, the feedback based on the detection result by the optical sensor17is stopped. Due to the above-described configuration, the control based on the result of erroneous detection is prevented, and the transfer device10may perform control based on the rotational speed of the driving roller19. As a result, the transfer device10may prevent quality deterioration in image formation.

Example of Functional Configuration

FIG.65is a diagram illustrating an example of a functional configuration of the transfer device10. For example, the transfer device10includes a plurality of photoconductors101, the belt16, primary transfer rollers102, and a control unit103. It is preferable that the transfer device10further includes a detector104, a calculator105, and a conveyance speed controller106. It is more preferable that the transfer device10further includes a distance changer107. Furthermore, it is more preferable that the transfer device10further includes a driving unit108, a rotational speed measurement unit109, and a rotational speed controller110.

The control unit103causes at least one of the primary transfer rollers102to press against the photoconductor101to execute a process to shill the mode. For example, the control unit103is implemented by the controller20.

The detector104executes a process to detect the mark40. For example, the detector104is implemented by the optical sensor17.

The calculator105executes a process to calculate the conveyance speed of the belt16based on the results of detection by the detector104. For example, the calculator105is implemented by the by the controller20.

The conveyance speed controller106performs a conveyance speed control procedure to control the conveyance speed of the belt16based on the results of calculation by the calculator105. For example, the conveyance speed controller106is implemented by the controller20.

The distance changer107performs a distance changing procedure to change the distance between the detector104and the belt16. For example, the distance changer107is implemented by the controller20.

The driving unit108performs a driving procedure for rotating the driving roller19to rotate the belt16. For example, the driving unit108is implemented by the driving motor60.

The rotational speed measurement unit109performs a rotational speed measurement procedure to measure the rotational speed of the driving roller19. For example, the rotational speed measurement unit109is implemented by the encoder61.

The rotational speed controller110performs a rotational speed control procedure to control the rotational speed of the driving roller19based on the measurement result of the rotational speed measurement unit109. For example, the rotational speed controller110is implemented by the controller20.

Due to the above-described configuration, the transfer device10may shift the mode without shilling to the state such as the fully separated state.

In a state such as the fully separated state, it may be difficult to control the conveyance speed of the belt16. For this reason, downtime may occur in the fully separated state. As a result, the productivity of the image forming apparatus decreases due to the occurrence of the downtime. Further, printing may not be continuously performed in the downtime.

On the other hand, the transfer device10enhances the productivity of the image forming apparatus by performing control so that the fully separated state does not occur.

Other Embodiment

The transfer device and the image forming apparatus may be a plurality of devices or apparatuses. In other words, the transfer device and the image forming apparatus may be configured such that a plurality of devices or apparatuses perform processing in a distributed manner, in a redundant manner, or in parallel.

The image forming apparatus may include a device other than the transfer device. For example, the image forming apparatus may include a device that performs image formation or information processing in addition to the transfer device.

The transfer device executes the control method by a program. The control method is implemented by causing an arithmetic unit, a control unit, and a storage unit included in the transfer device to cooperate with each other to execute processing.

It is therefore to be understood that the disclosure of the present specification may be practiced otherwise by those skilled in the art than as specifically described herein. Such embodiments and variations thereof are included in the scope and gist of the embodiments of the present disclosure and are included in the embodiments described in claims and the equivalent scope thereof.