JP5082898B2 - Rotating body contact / separation mechanism and image forming apparatus provided with the contact / separation mechanism - Google Patents

Description

  The present invention relates to a rotating body contacting / separating mechanism, and an image forming apparatus equipped with the contacting / separating mechanism used in an electrophotographic copying machine, a printer, etc. In particular, the present invention relates to an image forming apparatus characterized by a structure in which a transfer roller is brought into contact with and separated from a transfer belt.

  In general, in an image forming apparatus, when an image is not formed, the transfer roller is separated from the photosensitive drum or the transfer belt so that no contact mark of the transfer roller remains on the photosensitive drum or the transfer belt.

Conventionally, as a mechanism for moving a transfer roller from and to a photosensitive drum or a transfer belt, a mechanism using a motor and a sensor (for example, see Patent Document 1) or a mechanism using a one-way clutch (for example, see Patent Document 2). There is.
Japanese Patent Laid-Open No. 11-24442 JP 2007-264546 A

  However, in the former configuration, it is necessary to newly provide a motor and a sensor, resulting in an increase in cost.

  In the latter configuration, it is necessary to accurately set the number of rotations of the one-way clutch by rotating a plurality of gears, and there is a problem that the available motors are restricted and the cost is increased.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can separate rollers with a simple and inexpensive configuration.

As a means for solving the above problems, the present invention provides:
Rotating body contact / separation mechanism
A first rotating member;
A second rotating member provided to be movable toward and away from the first rotating member;
An actuating member for moving the second rotating member toward and away from the first rotating member;
A first drive gear having a one-way clutch reaches transfer the rotational force in the reverse rotation direction only of the first rotary member,
Said first drive gear provided to be interlocked with each other, the second drive gear with the one-way clutch you transmit the rotational force of the forward direction only of the first rotary member,
A gear meshing with the first drive gear, the gear having a first notch that is in non-contact with the first drive gear ;
A gear meshing with the second drive gear, comprising a second notch gear having a second notch that is not in contact with the second drive gear ,
When the first rotating member rotates in the reverse direction, the first driving gear transmits a rotational force to the operating member via the first intermittent gear, and the operating member comes into contact with the first rotating member. Separating the second rotating member from the first rotating member,
In a state where the second rotating member is separated from the first rotating member, the first notch portion faces the first drive gear,
In the state where the second rotating member is in contact with the first rotating member, the second notch is configured to face the second drive gear .

  With this configuration, when the first rotating member is rotated in the reverse direction while the second rotating member is in pressure contact with the first rotating member, the rotational force is applied to the second drive by the action of each one-way clutch. Although not transmitted to the gear, it is transmitted to the first drive gear. As a result, the first drive gear and the second drive gear that are linked to each other start to rotate. When the first drive gear rotates, the first toothless gear rotates to operate the operating member, and the second rotating member is separated from the first rotating member. When the second rotating member is separated from the first rotating member, the first drive gear is positioned in the notch portion of the first toothless gear. Therefore, even if the first drive gear continues to rotate, the first segmented gear does not rotate any further. Thereby, the 2nd rotation member is maintained in the state where it separated from the 1st rotation member.

  Further, when the first rotating member is rotated in the forward rotation direction in a state where the second rotating member is separated from the first rotating member, the rotational force is opposite to the above due to the action of each one-way clutch. In addition, it is not transmitted to the first drive gear, but is transmitted to the second drive gear. As a result, the first drive gear and the second drive gear that are linked to each other start to rotate. When the second drive gear rotates, the second toothless gear rotates to operate the operating member, and the second rotating member returns to the original position in pressure contact with the first rotating member. When the second rotating member is in pressure contact with the first rotating member, the second drive gear is positioned in the notch portion of the second toothless gear. Therefore, even if the second drive gear continues to rotate, the second segmented gear does not rotate any further. As a result, the second rotating member is maintained in pressure contact with the first rotating member.

Further, the present invention provides a means for solving the above-described problems,
The image forming apparatus includes the rotating body contact / separation mechanism.
The first rotating member is composed of a photosensitive drum or a supporting roller around a transfer belt,
The second rotating member may be composed of a transfer roller.

  According to the present invention, a simple and inexpensive configuration including only a pair of drive gears equipped with a one-way clutch, a pair of intermittent gears meshed with each drive gear, and an operating member, the first rotating member Thus, the second rotating member can be contacted and separated. Moreover, in this contact / separation operation, even if the drive gear continues to rotate, further power transmission can be prevented by the notch portion of the toothless gear. Therefore, drive control can be easily performed.

  Embodiments according to the present invention will be described below with reference to the accompanying drawings. In the following description, terms indicating a specific direction and position (for example, “up”, “down”, “right”, “left” and other terms including those terms) are used as necessary. These terms are used for easy understanding of the invention with reference to the drawings, and the technical scope of the present invention is not limited by the meaning of these terms.

  FIG. 1 shows a tandem color image forming apparatus to which an electrophotographic technique is applied according to this embodiment. The image forming apparatus generally includes an image forming unit 1, a transfer unit 2, an exposure unit 3, a paper feeding unit 4, and the like.

  As shown in FIG. 2, the image forming unit 1 includes a charging charger 7, a developing roller 8, a regulating blade 9, and the like around the photosensitive drum 6 in the casing 5. Further, the image forming unit 1 is disposed at four locations along the intermediate transfer belt 11 of the transfer unit 2 and forms a color image on the surface of the intermediate transfer belt 11 by forming yellow, magenta, cyan, and black images, respectively. Form.

  The transfer unit 2 spans an intermediate transfer belt 11 between a pair of support rollers 10 (first rotating members), and the intermediate transfer belt 11 is circulated and moved in the direction of an arrow by a driving unit (not shown). Part and a secondary transfer part.

  The primary transfer unit includes a primary transfer roller 12 that faces the photosensitive drum 6 of each image forming unit 1 with the intermediate transfer belt 11 sandwiched therebetween. The primary transfer roller 12 applies a positive voltage to the back surface of the intermediate transfer belt 11.

  The secondary transfer unit includes a secondary transfer roller 13 (second rotating member) that is slidably opposed to one support roller 10 (a roller located on the right side in FIG. 1), and is transferred to the intermediate transfer belt 11. The transferred toner image is transferred to a recording medium 14 (for example, paper).

  As shown in FIGS. 2 and 3, the rotation shaft 10a of one support roller 10 has a first drive gear 15 and a first drive gear 15 provided with one-way clutches 15a and 16a on the inner ring side and gear portions 15b and 16b on the outer ring side, respectively. Two drive gears 16 are provided. In the first drive gear 15, the one-way clutch 15a rotates idly when the rotating shaft 10a rotates in the forward rotation direction (indicated by an arrow a in FIG. 2), and indicates the reverse rotation direction (indicated by an arrow b in FIG. 2). ) To rotate integrally with the gear portion 15b. On the other hand, in the second drive gear 16, the one-way clutch 16a rotates idly when the rotating shaft 10a rotates in the reverse rotation direction, and rotates integrally with the gear portion 16b when rotating in the normal rotation direction.

  A first intermittent gear 17 meshes with the first drive gear 15, and a second intermittent gear 18 meshes with the second drive gear 16. The first segmented gear 17 and the second segmented gear 18 are formed with notches 17 a and 18 a that are not in contact with each other along the outer diameters of the first drive gear 15 and the second drive gear 16. . The first toothless gear 17 and the second toothless gear 18 are integrated so that the notch portions 17 a and 18 a are in a positional relationship shifted by 90 degrees in the rotation direction, and are fixed to the shaft member 19. Cams 20a and 20b (actuating members) in an eccentric state are attached to the shaft member 19 at two locations. The cams 20 a and 20 b rotate together with the shaft member 19, and can be rotated by pressing a lever 21 described later at a tip portion located on the opposite side of the shaft member 19.

  The secondary transfer roller 13 is rotatably attached to a first support shaft 22 provided at one end of the lever 21. The lever 21 is rotatable around a second support shaft 23 provided at the other end. The secondary transfer roller 13 is urged by a spring 24 that presses the lever 21 so as to be in pressure contact with the one support roller 10 via the intermediate transfer belt 11.

  The exposure unit 3 irradiates the photosensitive drum 6 with laser light to form an electrostatic latent image corresponding to image data read by a scanner (not shown).

  The paper feeding unit 4 sequentially conveys the recording medium 14 accommodated in the cassette 25 to the secondary transfer unit via a plurality of conveying rollers 26, transfers the toner image, and transfers the toner image transferred by the fixing unit 27. Is fixed, and then carried out to the discharge tray 28.

  Next, the operation of the image forming apparatus having the above configuration, particularly the operation in the transfer unit 2 will be described. The “image formation” described below means a time for transferring the toner image on the photosensitive drum 6 to the intermediate transfer belt 11 (or the recording medium 14) to form an image. "Means a time other than" at the time of image formation ", that is, before and after the image formation, and between the time of image formation and the time of image formation. “When toner is forcibly consumed” means the time during which “reversely charged toner on the developing roller 8 is ejected by flying toward the photoreceptor” during “non-image formation”.

  At the time of image formation, color print data obtained by reading an image with an image reading unit (not shown) or image data output from a personal computer or the like is subjected to predetermined signal processing by a control unit (not shown) and then yellow ( Y), magenta (M), cyan (C), and black (K) are supplied to each image forming unit 1 as image signals of respective colors. In each image forming unit 1, a laser beam modulated by an image signal is projected onto each photosensitive drum 6 to form an image latent image. A yellow, magenta, cyan, and black toner image is formed on each photosensitive drum 6. The formed yellow, magenta, cyan, and black toner images are primarily transferred onto the moving intermediate transfer belt 11 in sequence by the action of the primary transfer roller 12. The superimposed toner image formed on the intermediate transfer belt 11 in this way moves to the secondary transfer portion according to the movement of the intermediate transfer belt 11.

  In the secondary transfer portion, the support roller 10 rotates in the forward rotation direction, the first drive gear 15 provided on the rotation shaft rotates idly by the one-way clutch 15a, and the second drive gear 16 rotates in the forward rotation direction. ing. Since the gear portion 15 b of the first drive gear 15 is not rotating, no power is transmitted to the first segmented gear 17. Further, the second drive gear 16 is positioned in the notch 18 a of the second segmented gear 18, and no power is transmitted to the second segmented gear 18. Therefore, the shaft member 19 does not rotate, and the lever 21 is not rotated by the cam 20. That is, the color toner images that are conveyed and superimposed while the recording medium 14 supplied from the paper feeding unit 4 is sandwiched between the intermediate transfer belt 11 and the secondary transfer roller 13 that are stretched around the support roller 10, Secondary transfer is performed collectively on the paper. The recording medium 14 on which the toner image is secondarily transferred is fixed by the fixing unit 27 and discharged to the discharge tray 28.

  By the way, immediately after turning on the power of the image forming apparatus, immediately after returning from the sleep state, or when the number of printed sheets reaches a predetermined value, image formation is stopped (during non-image formation), and developer recovery processing is performed. Run.

  At the time of non-image formation, the photosensitive drum 6 is stopped. Then, the rotation direction of the developing roller 8 (sleeve) is reversed from that during image formation. Further, a negative low voltage is applied to the developing roller 8, and an AC voltage composed of a developing phase and a recovery phase is applied when the toner is forcibly consumed during non-image formation. Thereby, the developer D adhering to the surface of the developing roller 8 is sequentially peeled off by the peeling portion 29 and dropped.

  At this time, the intermediate transfer belt 11 is moved in the reverse direction by a driving means (not shown), and the support roller 10 is rotated in the reverse direction. Accordingly, the first drive gear 15 also rotates in the reverse direction, and the first partial gear 17 that meshes with the gear portion 15b rotates. When the first partial gear 17 rotates, the shaft member 19 rotates, and the cam 20 provided there rotates, so that the lever 21 is pressed and starts rotating. The secondary transfer roller 13 is separated from the intermediate transfer belt 11 by the rotation of the lever 21. As a result, the secondary transfer roller 13 does not press the support roller 10 via the intermediate transfer belt 11 for a long time. Further, it is possible to prevent deformation (the shape does not return even when the load is removed), and it is possible to appropriately transfer the toner image by the secondary transfer roller 13 over a long period of time.

  Even if the support roller 10 continues to rotate in the reverse direction, the first drive gear 15 is positioned in the notch 17a of the first toothless gear 17 if the first drive gear 15 rotates by a predetermined angle. Therefore, the first partial gear 17 does not continue to rotate any further. As a result, the cam 20 presses the lever 21 and the secondary transfer roller 13 is accurately positioned at an appropriate position farthest from the intermediate transfer belt 11. That is, even if the rotation of the support roller 10 is not accurately controlled, simple control such as rotation for a certain time may be used.

  The second segment gear 18 is also rotated by the rotation of the shaft member 19. The second drive gear 16 meshing with the second segment gear 18 is idled by the one-way clutch 16a, and the second segment gear 18 is rotated. Following this, only the gear portion 16b rotates.

  Further, in the above-described embodiment, the case where the mechanism for moving the roller in and out of the transfer unit 2 has been described. However, the mechanism can also be used for the fixing unit 27.

  In the above embodiment, the present invention has been described by taking as an example an apparatus of a type in which a toner image is primarily transferred onto the intermediate transfer belt 11 and then further transferred onto the recording medium 14. The invention is not limited to this, and a toner image is directly transferred onto a recording medium 14 that is conveyed on a sheet conveying belt having the same configuration as that of the intermediate transfer belt 11 or an apparatus of a type that directly transfers to the recording medium 14 from the photosensitive drum 6. The present invention can also be applied to a type of apparatus.

1 is a schematic view of an image forming apparatus according to an embodiment. It is a schematic perspective view which shows the 2nd transcription | transfer part of FIG. It is a schematic front view which shows the 2nd transcription | transfer part of FIG. The state in the 2nd transcription | transfer part of FIG. 1 at the time of image formation is shown, (a) is a front view of the 1st drive gear and 1st part-tooth gear of FIG. 3, (b) is the 2nd drive gear. And (c) is a front view of a support roller and a secondary transfer roller. It is a figure which shows the state which rotated the support roller in the reverse rotation direction from the state shown in FIG. FIG. 6 is a diagram showing a state where the support roller is further rotated in the reverse rotation direction from the state shown in FIG. 5 and the first drive gear is positioned at the notch portion of the second intermittent gear.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image formation unit 2 ... Transfer unit 3 ... Exposure unit 4 ... Paper feed unit 5 ... Casing 6 ... Photoconductor drum 7 ... Charger charger 8 ... Developing roller 9 ... Restriction blade 10 ... Support roller (1st rotation member)
10a ... Rotating shaft 11 ... Intermediate transfer belt 12 ... Primary transfer roller 13 ... Secondary transfer roller (second rotating member)
DESCRIPTION OF SYMBOLS 14 ... Recording medium 15 ... 1st drive gear 15a ... One-way clutch 15b ... Gear part 16 ... 2nd drive gear 16a ... One-way clutch 16b ... Gear part 17 ... 1st missing gear 17a ... Notch 18 ... 2nd missing gear 18a ... Notch 19 ... Shaft member 20a, 20b ... Cam (operating member)
DESCRIPTION OF SYMBOLS 21 ... Lever 22 ... 1st spindle 23 ... 2nd spindle 24 ... Spring 25 ... Cassette 26 ... Conveyance roller 27 ... Fixing unit 28 ... Discharge tray

Claims (3)

A first rotating member;
A second rotating member provided to be movable toward and away from the first rotating member;
An actuating member for moving the second rotating member toward and away from the first rotating member;
A first drive gear having a one-way clutch reaches transfer the rotational force in the reverse rotation direction only of the first rotary member,
Said first drive gear provided to be interlocked with each other, the second drive gear with the one-way clutch you transmit the rotational force of the forward direction only of the first rotary member,
A gear meshing with the first drive gear, the gear having a first notch that is in non-contact with the first drive gear ;
A gear meshing with the second drive gear, comprising a second notch gear having a second notch that is not in contact with the second drive gear ,
When the first rotating member rotates in the reverse direction, the first driving gear transmits a rotational force to the operating member via the first intermittent gear, and the operating member comes into contact with the first rotating member. Separating the second rotating member from the first rotating member,
In a state where the second rotating member is separated from the first rotating member, the first notch portion faces the first drive gear,
The rotating body contacting / separating mechanism , wherein the second notch portion faces the second drive gear in a state where the second rotating member is in contact with the first rotating member.   An image forming apparatus comprising the rotating body contacting / separating mechanism according to claim 1. The first rotating member is a photosensitive drum or a support roller around a transfer belt,
The image forming apparatus according to claim 2, wherein the second rotating member is a transfer roller.

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