JP2007212934A - Image forming apparatus - Google Patents

Abstract

An object of the present invention is to provide an image forming apparatus in which an intermediate transfer unit can be attached and detached without requiring a user to perform a special operation for separating the drive and without damaging a gear drive transmission system. To do.
A typical configuration of an image forming apparatus according to the present invention includes a secondary transfer roller 26 that contacts and separates a primary transfer roller 39 from a photosensitive drum 28 via an intermediate transfer belt 27B, and the secondary transfer roller 26. In the image forming apparatus having the transfer unit 50 that is detachable from the apparatus main body, and the gear 38G that transmits the drive from the apparatus main body to the gear 37G, the gear 38G is missing. It is a toothed gear and is characterized in that the primary transfer roller 39 is rotated away from the range of the locus 43 drawn by the gear 37G when the transfer unit is attached or detached while being separated from the photosensitive drum 28.
[Selection] Figure 1

Description

  The present invention relates to an image forming apparatus such as a color copying machine or a color printer.

  Conventionally, as a method for supplying a drive for bringing an intermediate transfer belt, which is an endless belt, into contact with a photosensitive member, there is a configuration as disclosed in Japanese Patent Application Laid-Open No. 2001-318508.

  Recently, the intermediate transfer belt is brought into contact with and separated from the color photoconductor during recording in order to prevent consumption of the color photoconductor not used when performing monochrome printing with an inline color printer or the like. Further, as the image output speeds up, the above contact / separation operation is performed in a short time.

  For the contact operation of the intermediate transfer belt, it is necessary to supply a high torque drive from the main body side. For this reason, as shown in FIG. 10, there is a case where gear transmission is used as a driving transmission method from the main body to the transfer unit.

  In the contact / separation mechanism of the intermediate transfer belt 50B of the intermediate transfer unit 50 detachable in the direction of arrow A shown in FIG. 10, the transfer roller contacts the photoreceptor via the intermediate transfer belt 50B. The primary transfer rollers 51Y, 51M, 51C, 51Bk are pressed by springs (not shown). Further, the bearings 53Y, 53M, 53C, and 53Bk of the primary transfer roller 51 partially have protrusions 53Ya, 53Ma, 53Ca, and 53Bka. The protrusions 53 </ b> Ya to 53 </ b> Bka are inserted into holes 52 </ b> Y, 52 </ b> M, 52 </ b> C, 52 </ b> Bk of the separation plate 52 that is a contact / separation mechanism of the unit 50.

  The separation plate 52 is engaged with the separation levers 54F and 54R held by the separation shaft 54, and moves linearly when the separation levers 54F and 54R rotate. The separation shaft 54 is formed integrally with the separation gear 56 and is held so as to be movable in the axial direction with respect to the separation levers 54F and 54R. Further, the separation plate 52 is urged in the direction of arrow B by a separation plate spring (not shown). Therefore, in this system, the separation gear 56 is urged in the arrow B direction.

  Further, by rotating the separation drive gear 57 on the drive main body side by a motor (not shown), the separation gear 56 rotates and the separation levers 54F and 54R rotate. As a result, the separation plate 52 moves linearly, the pressure applied by a spring (not shown) applied to the primary transfer roller 51 is released, and the primary transfer roller 51 contacts the photoconductor via the intermediate transfer belt 50B. Touch.

JP 2001-318508 A

  However, the gear drive transmission system has the following problems because the gears are always engaged with each other.

  The driven gear (separation gear 56) of the unit 50 is always urged by the separation drive gear 57 and the contact mechanism on the main body side. For this reason, when attaching and detaching the unit 50, a force stronger than the constantly applied urging force is required. Accordingly, there is a problem that the user cannot smoothly attach and detach the unit 50 unless the user operates a mechanism for separating other driving.

  Further, when the unit 50 is pulled out once and then the unit 50 is returned to the apparatus main body again, the posture of the gear 57 is changed by pulling out the unit 50. For this reason, when the phase of the gear 57 is controlled, there is a possibility that the phase is not correct. When the contact / separation drive is operated while the phase is shifted, the normal operation is not performed and the contact position is defective.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus in which an intermediate transfer unit can be attached and detached without requiring a user to perform a special operation for disconnecting driving and without damaging a gear drive transmission system. It is another object of the present invention to provide an image forming apparatus capable of suppressing a gear phase shift and suppressing a contact position defect.

  In order to solve the above-described problems, a typical configuration of the image forming apparatus according to the present invention includes a contact / separation member that contacts and separates the transfer roller from the image carrier via an intermediate transfer member, and a contact / separation member. An image forming apparatus comprising: a transfer unit that includes a first gear that transmits driving; and a transfer unit that is detachable from the apparatus main body; and a second gear that transmits driving from the apparatus main body to the first gear. The second gear is a chipped gear, and the transfer roller rotates outside the range of the locus drawn by the first gear when the transfer unit is attached or detached when the transfer roller is separated from the image carrier. It is characterized by.

  According to the present invention, the intermediate transfer unit can be attached and detached without requiring a special operation for the user to disconnect the drive and without damaging the gear drive transmission system. Moreover, the shift | offset | difference of the phase of a gear can be suppressed and a contact position defect can be suppressed.

[First embodiment]
A first embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of the image forming apparatus according to the present embodiment. FIG. 2 is a perspective view of the intermediate transfer unit in an initial state. FIG. 3 is a sectional view showing an initial state of the drive transmission system. FIG. 4 is a cross-sectional view showing the collar contact state of the drive transmission system. FIG. 5 shows the relationship between the spacing plate and the protrusions. FIG. 6 shows an infrared shielding flag pattern for controlling the apparatus main body drive system for contacting and separating the intermediate transfer belt and the primary transfer roller. FIG. 7 is a cross-sectional view showing the positional relationship between the separation drive gear and the driven gear in the comparative example.

  As shown in FIG. 1, the image forming apparatus 100 includes a feeding cassette 21, a pickup roller 22, a feed roller 23, a retard roller 24, a registration roller pair 25, a secondary transfer roller 26, an intermediate transfer unit 27, and a separation drive gear 38G. have. The image forming apparatus 100 includes a photosensitive drum 28, a laser scanner 32, a fixing device 33, a discharge roller pair 34, and a discharge tray 35.

  As shown in FIGS. 1 and 2, the intermediate transfer unit 27 includes an intermediate transfer belt 27B, a driving roller 27D, a tension roller 27T, a separation plate 36, a separation shaft 37, separation levers 37F and 37R, a separation gear 37G, and a primary transfer roller. 39. The unit 27 is detachably held in the apparatus main body by opening the open / close door 41 on the side of the main body.

  The intermediate transfer belt 27B, which is an intermediate transfer body, is an endless belt and is stretched by a driving roller 27D and a tension roller 27T. The drive roller 27D nips with the secondary transfer roller 26 via the belt 27B.

  The primary transfer rollers 39Y, 39M, 39C, 39Bk are urged by the belt 27B. The bearing 40 of the roller 39 has a protrusion 40a in part. The separation plate 36, which is a contact / separation member, has a long hole 36a and L-shaped holes 36Y, 36M, 36C, and 36Bk from the drive roller 27D side. The protrusion 40a is in the holes 36Y, 36M, 36C, and 36Bk of the spacer plate 36.

  The separation levers 37F and 37R are rotatably held together with the separation shaft 37, and have protrusions 37Fa and 37Ra in part. The protrusions 37Fa and 37Ra are engaged with the elongated hole 36a. The long hole 36a extends in the vertical direction perpendicular to the longitudinal direction of the spacer plate 36, and the protrusions 37Fa and 37Ra have play in the vertical direction of the long hole 36a.

  When the separation levers 37F and 37R rotate, the separation plate 36 moves linearly in the longitudinal direction of the separation plate 36. The separation plate 36 is urged toward the tension roller 27T by a separation plate spring 36SP.

  As shown in FIG. 5, the holes 36Y to 36Bk are formed in an L shape from the vertical holes 36Y1 to 36Bk1 and the horizontal holes 36Y2 to 36Bk2 extending from the bottom of the vertical holes 36Y1 to 36Bk1 to the drive roller 27D side.

  As shown in FIG. 5C, when the protrusion 40a is on the ceiling of the vertical holes 36Y1 to 36Bk1, the roller 39 is urged by the belt 27B (color contact state). As shown in FIG. 5A, when the protrusion 40a is in the lateral holes 36Y2 to 36Bk2, the roller 39 is separated from the belt 27B (separated state).

  The width of the ceiling portion of the vertical hole 36Bk1 is formed longer than that of the other holes 36Y to 36C (in this embodiment, it is about 2 to 3 times). Therefore, depending on the position of the separation plate 36, as shown in FIG. 5B, the protrusion 40a is provided only at the ceiling portion of the vertical hole 36Y1, and the other protrusions 40a are in the horizontal holes 36Y2 to 36C2. At this time, only the roller 39Bk contacts the belt 27B, and the rollers 39Y to 39C are separated from the belt 27B (monochrome contact state).

  The separation shaft 37 and the gear 37G as the first gear are integrally formed, and are held so as to be movable with respect to the separation levers 37F and 37R. The gear 37G may be a normal all-tooth gear, but in this embodiment, the gear 37G is a chipped gear having teeth only in the range of about 1/5 of the circumference. Thereby, the rotation trajectory of the separation levers 37F and 37R is limited, and the length of the long hole 36a through which the separation levers 37F and 37R rotate can be shortened. Further, the spacing plate 36 does not travel more than necessary, and the stroke area of the spacing plate 36 can be limited. For this reason, the dimension of the unit 27 in the stroke direction (longitudinal direction) of the separation plate 36 can be reduced, and the unit 27 can be reduced in size.

  The gear 38G as the second gear is a chipped gear having teeth only in the range of about 1/5 of the circumference. The gear 38G only needs to be able to rotate and retreat to a position where it does not interfere with any position where the gear 37G rotates.

  The gear 37G receives driving from the gear 38G and rotates the separation levers 37F and 37R. On the same axis as the gear 38G, there is provided an infrared shielding flag gear 38F which is an initializing means for initializing the gear 38G and is a detecting means for detecting the rotational position of the gear 38G. The detection mark (slit 38Fs) of the flag gear 38F is read by the infrared sensor 38S, and the rotation information of the flag gear 38F (separation drive gear 38G) is fed back to the motor control board (not shown). Then, by controlling the rotation speed of a motor (not shown) by a motor control board, the gear 38G is rotated to three positions, that is, a separation position, a monochrome contact position, and a color contact position, thereby performing position control.

(Gear 37G, 38G position control)
In the initial state, the gears 37G and 38G are at the separation positions 37Ga and 38Ga shown in FIG. At this time, the gear 38G stands by outside the range of the locus 43 drawn by the gear 37G (tooth tip circle 42) when the unit is attached and detached. That is, the gear 38G rotates to a position where it does not interfere with the gear 37G when the unit 27 is attached or detached. For this reason, when the gear 38G is in the initial state (separated position 38Ga), the gear 38G does not interfere with the gear 37G when the unit 27 is attached or detached, regardless of the state of the gear 37G.

  In the initial state, the separation plate 36 is urged toward the tension roller 27T by the separation plate spring 36SP. For this reason, the protrusion 40a is positioned in the horizontal holes 36Y2 to 36Bk2, and the rollers 39Y to 39Bk are all pushed down to be separated from the photosensitive drums 28Y to 28Bk (belt 27B) as the image carrier.

  When performing monochrome recording, the gear 38G is rotated from the separation position 38Ga to the monochrome contact position. When the gear 38G rotates to the monochrome contact position, the gear 37G rotates, and the separation levers 37F and 37R slide the separation plate 36 to the intermediate position. In this state, only the protrusion 40a in the hole 36Bk moves from the horizontal hole 36Y2 to the vertical hole 36Y1 to release the pressing of the roller 39Bk, and a monochrome contact state is established.

  When performing color recording, the gear 38G is further rotated to the color contact position 38Gb shown in FIG. As a result, the gear 37G rotates, and the separation levers 37F and 37R move the separation plate 36 completely. In this state, all of the holes 36Y to 36Bk of the separation plate 36 release the pressing of the rollers 39Y to 39Bk, resulting in a collar contact state as shown in FIG.

  In the color contact state or the monochrome contact state, the recording sheet fed from the feeding cassette 21 by the pickup roller 22 is separated into one sheet by the feed roller 23 and the retard roller 24 and conveyed to the registration roller pair 25. Is done. Here, the recording sheet is temporarily stopped.

  On the other hand, an image exposed on the photosensitive drums 28Y to 28Bk (only the photosensitive drum 28Bk in the case of monochrome recording) is developed by a developing device (not shown) by the laser scanner 32 as an exposure unit, and is primarily transferred to the belt 27B. The image primarily transferred onto the belt 27B proceeds to the secondary transfer roller 26, and the recording sheet stopped by the registration roller pair 25 is restarted in accordance with the image. The restarted recording sheet is transferred with the image by the secondary transfer roller 26, fixed with the image by the fixing device 23, and discharged onto the 25 discharge trays by the 24 discharge roller pairs.

  When the recording operation is completed, the gear (38G) is reversely rotated to the separation position (38Ga) by reversing the motor (not shown). As a result, the gear 37G rotates in the reverse direction, the separation levers 37F and 37R rotate in the reverse direction, and the separation plate 36 slides to the initial position shown in FIG.

  The above operation is a series of operations of the gears 37G and 38G from the start of the recording operation to the end of the recording operation. When the recording operation ends normally, the gears 37G and 38G always return to the initial positional relationship.

  As described above, when the gears 37G and 38G are in the initial positions, the gear 38G is in a position that does not interfere with any locus drawn by the gear 37G when the unit 27 is attached or detached. Thereby, it is not necessary for the user to perform a special operation for disconnecting the drive, and the unit 27 can be attached and detached without damaging the gear drive transmission system (gears 37G and 38G).

(Initialization of gears 37G and 38G)
Next, initialization of the two gears 37G and 38G performed when the positional relationship between the gear 37G and the gear 38G is not known will be described. Examples of the case where the positional relationship between the gear 37G and the gear 38G is not known include immediately after the main body is turned on or when a recording sheet JAM occurs during conveyance within the main body.

  In order to initialize the gears 37G and 38G, first, the gear 38G is rotated, and the gear 37G is rotated in a direction to release the pressing of the roller 39 (clockwise in FIGS. 2 and 3). The gear 38G and the flag gear 38F rotate in the direction of arrow C in FIG. In FIG. 6, the flag position corresponding to the separation position 38Ga (position in FIG. 3) of the gear 38G is 38Fa, and the flag position corresponding to the collar contact position Gb (position in FIG. 4) of the gear 38G is 38Fb. And

  When the infrared ray (incident line SS) emitted from the sensor 38S continues to rotate in the same direction and is transmitted through the slit 38Fs in the flag of the flag gear 38F, the sensor output PI is H (light shielding) → L (transmission). It becomes. By stopping the motor after a predetermined amount of rotation in the rotational direction C from when the sensor output PI = L (transmission), the gear 38G is returned to the separation position 38Ga and the gear 38G is initialized.

  On the other hand, in the state where the gear 38G is initialized (separated state), the meshing between the gear 37G and the gear 38G is released. In this state, the separation plate 36 is urged so as to return to the initial position by the separation spring 36SP. For this reason, the long hole 36a of the separation plate 36 rotates the separation levers 37F and 37R, and in conjunction with this, the gear 37G returns to the separation position 37Ga (initial position) and is initialized.

  After the above initialization is performed, the gears 38G and 37G always return to the separation positions 38Ga and 37Ga. That is, the gear 38G is in a position where it does not interfere with any locus drawn by the gear 37G when the unit 27 is attached or detached. Thereby, it is not necessary for the user to perform a special operation for disconnecting the drive, and the unit 27 can be attached and detached without damaging the gear drive transmission system (gears 37G and 38G). Moreover, the shift | offset | difference of the phase of a gear can be suppressed and a contact position defect can be suppressed.

  Further, in the image forming apparatus 100 of the present embodiment, as shown in FIG. 3, the line segment L1 connecting the rotation centers of the gear 38G and the gear 37G is not parallel to the attaching / detaching direction L2 of the unit 27 (almost right angle). . On the other hand, as shown in FIG. 7, when the line segment L1 and the attaching / detaching direction L2 are parallel, the gear 37G is set to the gear when the unit 27 is mounted when the posture of the gear 37G cannot be specified, such as immediately after assembly of the apparatus main body. There is a possibility that the tooth 27 collides with 38G and the unit 27 cannot be stored in the apparatus main body.

  Therefore, in the image forming apparatus 100 according to the present embodiment, as shown in FIG. 3, the line segment L1 and the attachment / detachment direction L2 are not in a parallel relationship. Thereby, even when the gear 37G collides with the gear 38G when the unit 27 is mounted on the main body, the gear 37G is rotated by the collision force, and the unit 27 can be stored in the apparatus main body.

[Second Embodiment]
Next, a second embodiment of the image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 8 shows an infrared shielding flag pattern for controlling an apparatus main body drive system for contacting and separating the intermediate transfer belt and the primary transfer roller according to this embodiment. FIG. 9 is an initialization flowchart of the apparatus main body drive system. About the part which overlaps with said 1st embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The image forming apparatus according to the present embodiment is obtained by changing the initialization method performed when the positional relationship between the gear 38G and the gear 37G is not known in the image forming apparatus 100 according to the first embodiment. Hereinafter, initialization of the gears 37G and 38G in the present embodiment will be described.

  As shown in FIGS. 8A and 8B, the slit 38Fs is provided between the initial position 38Fa and the collar contact position 38Fb. That is, the slit 38Fs is provided between the rotation angles from the initial state of the gear 38G until the drive cannot be transmitted.

  The initialization of the gears 37G and 38G in the present embodiment is performed according to the flowchart shown in FIG. As shown in FIG. 9, the gear 38 </ b> G is rotated by a motor (not shown), and the gear 37 </ b> G is rotated in a direction to release the pressing of the roller 39 (clockwise in FIGS. 2 and 3). The gear 38G and the flag gear 38F rotate in conjunction with each other and rotate in the direction of arrow C in FIG. 8A (S901). At this time, a variable R indicating the rotation speed of a motor (not shown) is counted according to the rotation from R = 0 (S902).

  While the output PI of the sensor 38S is PI = H (light-shielding), the motor rotation number (variable R) is continuously counted (S903, S904). When the output PI of the sensor 38S is changed from PI = H (light shielding) to L (transmission) by the slit 38Fs in FIGS. 8A and 8B (S904), R = 0 is set again and the variable R is set again. Is started (S905). Next, when R = X, the motor (not shown) is stopped (S906).

  Thereafter, the motor is rotated in the opposite direction to the previous rotation, and R is recounted from 0 (S907). In FIG. 8, when R = Y, the rotation of the motor is stopped (S908). As a result, the gear 38G is returned to the separation position 38Ga to initialize the gear 38G. On the other hand, the gear 37G receives the reverse rotation of the gear 38G, returns to the separation position 37Ga (initial position), and is initialized.

  The initialization method described above can reduce the number of noise generations during initialization and extend the life of the gear. That is, as described in the first embodiment, when the gear 37G is initialized by the biasing force of the separation spring 36SP, the moment when the biasing force acting on the gear 37G is released at once and the contact mechanism returns to the initial state. A large impact sound is generated.

  Further, at the moment when the gears 37G and 38G are disengaged, the biasing force of the separation spring 36SP is concentrated on the tooth tips of the gears 37G and 38G. For this reason, by repeating the number of impacts, the tooth tips of the gears 37G and 38G are deformed and worn, and the life of the gears is reduced.

  On the other hand, by performing the initialization of the present embodiment, the number of times that the gears 37G and 38G are disengaged is reduced as compared with the initialization method described in the first embodiment. Thereby, the frequency | count that an harsh impact sound is generated can be reduced. Further, the life of the gears 37G and 38G can be extended.

1 is a cross-sectional view of an image forming apparatus according to a first embodiment. FIG. 3 is a perspective view of the intermediate transfer unit according to the first embodiment in an initial state. It is sectional drawing which shows the initial state of the drive transmission system which concerns on 1st embodiment. It is sectional drawing which shows the color contact state of the drive transmission system which concerns on 1st embodiment. (A) It is a figure which shows the relationship between the separation plate and protrusion of a separation state. (B) It is a figure which shows the relationship between the separation plate and protrusion of a monochrome contact state. (C) It is a figure which shows the relationship between the separation plate and protrusion of a color contact state. 4 is an infrared light shielding flag pattern for controlling an apparatus main body drive system for contacting and separating the intermediate transfer belt and the primary transfer roller according to the first embodiment. It is sectional drawing which shows the positional relationship of the separation drive gear and driven gear in a comparative example. It is a pattern of an infrared shielding flag for controlling an apparatus main body drive system for contacting and separating the intermediate transfer belt and the primary transfer roller according to the second embodiment. It is an initialization flowchart of the apparatus main body drive system which concerns on 2nd embodiment. FIG. 10 is a perspective view of a conventional intermediate transfer unit in an initial state.

Explanation of symbols

21 ... feed cassette, 22 ... pickup roller, 23 ... feed roller, 24 ... retard roller, 25 ... registration roller pair, 26 ... secondary transfer roller, 27 ... intermediate transfer unit, 27B ... intermediate transfer belt, 27D ... drive roller , 27T ... tension roller, 28 ... photosensitive drum, 32 ... laser scanner, 33 ... fixing device, 34 ... discharge roller pair, 35 ... discharge tray, 36 ... separation plate (contact / separation member), 36 ... vertical hole, 36SP ... separation Leaf spring, 36Y to Bk ... hole, 36Y1 to Bk1 ... vertical hole, 36Y2 to Bk2 ... horizontal hole, 36a ... long hole, 37 ... separation shaft, 37F, 37R ... separation lever, 37G ... separation gear (first gear), 37Ga , 38Ga ... spaced position, 37Ra ... projection, 38F ... infrared light shielding flag gear (detection means), 38Fa ... initial position, 38Fs ... slip (Detection mark), 38G ... separation drive gear (second gear), 38Gb ... collar contact position, 38S ... infrared sensor, 39 ... primary transfer roller, 40 ... bearing, 40a ... projection, 41 ... opening / closing member, 42 ... Tip circle, 43 ... locus, 100 ... image forming apparatus

Claims (4)

A transfer having a contact / separation member for contacting and separating the transfer roller to and from the image carrier via an intermediate transfer member, and a first gear for transmitting drive to the contact / separation member, and detachable from the apparatus main body In an image forming apparatus comprising: a unit; and a second gear that transmits driving from the apparatus main body to the first gear.
The second gear is a chipped gear, and the transfer roller rotates away from the range of the locus drawn by the first gear when the transfer unit is attached or detached when the transfer roller is separated from the image carrier. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the first gear is a chipped gear. Having detection means for detecting the rotational position of the second gear;
This detection means has a detection mark that detects the rotational position of the second gear by reading with a sensor,
3. The image forming apparatus according to claim 1, wherein the detection mark is provided between rotation angles from the initial state of the second gear until the drive cannot be transmitted. 4.   4. The line segment connecting the rotation center of the first gear and the rotation center of the second gear is not parallel to the attaching / detaching direction of the transfer unit. 5. Image forming apparatus.

Images