The present invention relates to an image forming apparatus of an electrophotographic image forming type or the like in which an image is formed on a recording material (medium). Particularly, the present invention relates to an image forming apparatus of a tandem type including a plurality of rotatable image bearing members which are successively arranged in a predetermined direction and on which images different in color are to be formed.
Here, the image forming apparatus forms the image on the recording material by using an electrophotographic image forming process or the like. As the image forming apparatus, there are, e.g., a copying machine, a printer (e.g., a color LED printer) a facsimile machine, and a word processor. Further, on the recording material, the image is formed by the image forming apparatus, and the recording material may include, e.g., a sheet, an OHT sheet, and the like (hereinafter referred to as the sheet).
As a conventional color image forming apparatus, an electrophotographic image forming apparatus employing the tandem type has been known. The tandem type is a type in which a plurality of electrophotographic photosensitive (member) drum (hereinafter referred to as a drum) as image bearing members provided correspondingly to develops (hereinafter referred to as toners) of respective colors are arranged in line, and in which toner images carried on the respective drums are transferred superposedly onto a transfer receiving member (material) to obtain a desired color tone. As the transfer receiving member, e.g., an intermediary transfer material such as an endless intermediary transfer belt may be used (intermediary transfer type), and a sheet which is fed by a feeding member and onto which the toner image is directly transferred from the drum may also be used (direct transfer type).
In the image forming apparatus of the tandem type, output of color images of yellow (Y), magenta (M), cyan (C) and black (Bk) is not always required but output of a monochromatic image such as a black (Bk) image is required in not a few cases. Further, also a constitution in which the monochromatic image is obtained in a state in which all of the drums are contacted to the transfer receiving member and in which rotational drive of the drums other than the drum for black is stopped has been known. However, according to this constitution, friction is generated between the fed transfer receiving member and the drums for the colors other than black, and therefore generates a problem such that the transfer receiving member and the drums are liable to deteriorate.
As a countermeasure against this problem, there is a constitution in which when the output of Bk, in order to extend lifetimes of the drums and developing devices for Y, M and C other than Bk, transfer members for Y, M and C are spaced (separated) from the corresponding drums. For example, there is a constitution, as described in Japanese Laid-Open Patent Application (JP-A) 2009-128580, in which in order to move transfer rollers for Y, M and C toward or away from the drums, the transfer rollers for Y, M and C are contacted to or spaced from the transfer receiving member by being linearly moved vertically. Further, there is a constitution, as described in U.S. Pat. No. 7,813,683, in which in order to move the transfer rollers for Y, M and C toward or away from the drums, a pushing-up roller is contacted to or spaced from the transfer receiving member.
In the image forming apparatus in JP-A 2009-128580, even when the transfer rollers for Y, M and C are spaced from the drums during the output of Bk, an attitude of the transfer receiving member is determined by the transfer roller for Bk and a member for stretching the transfer receiving member. In this case, it would be considered that a distance of the drums for Y, M and C, particularly the drum for C, adjacent to the drum for Bk, from the transfer receiving member cannot be increased sufficiently. It would be also considered that in the case where the sufficient distance cannot be ensured, e.g., in the case where the transfer receiving member is in a waved state, the transfer receiving member contacts the drums for Y, M and C and thus the transfer receiving member and the drums are liable to deteriorate.
Further, in the image forming apparatus in U.S. Pat. No. 7,813,683, when the Bk image is outputted, the transfer receiving member is spaced directly by the pushing-up roller, and therefore it is possible to expect an effect of sufficiently increase the distance of the drums for Y, M and C from the transfer receiving member. However, in the image forming apparatus in U.S. Pat. No. 7,813,683, there is a need to provide the pushing-up roller itself and a mechanism for causing the pushing-up roller to be contacted to or spaced from the transfer receiving member. Further, the pushing-up roller is contacted to the transfer receiving member during the output of the monochromatic image, and therefore a mechanism for applying a voltage (bias), of the same polarity as the polarity of the toner, to the pushing-up roller is needed. Therefore, the number of parts was increased, and the image forming apparatus was upsized for ensuring spaces for these parts.
The present invention has been accomplished in view of the above-described circumstances.
A principal object of the present invention is to provide an image forming apparatus capable of sufficiently increasing a distance of image bearing members for Y, M and C from a transfer receiving member during output of an image of, e.g., Bk in a relatively simple constitution without upsizing the image forming apparatus.
According to an aspect of the present invention, there is provided an image forming apparatus for forming an image on a recording material, comprising: a rotatable first image bearing member; a plurality of rotatable second image bearing member; an endless belt provided rotatably opposed to the first image bearing member and the second image bearing members; a driving roller for rotating the belt member in contact with an inner peripheral surface of the belt member; a supporting roller for supporting the belt member in contact with the inner peripheral surface of the belt member; a first transfer member provided opposed to the first image bearing member via the belt member; a plurality of second transfer members provided opposed to the second image bearing members, respectively, via the belt member; and a supporting member for movably supporting the second transfer members, wherein the supporting member is movable between a first position in which the second transfer members are placed in a state in which the second transfer members are contacted to the belt member together with the second image bearing members to sandwich the belt member therebetween, and a second position in which the second transfer members are retracted from the first position to space the second image bearing members and the second transfer members from the belt member, wherein when image formation is effected in a state in which the supporting member is positioned in the first position, a nip between the first image bearing member and the belt member is positioned closer to a side where the supporting roller is positioned than a rectilinear line connecting contact positions of the belt member with the second image bearing members.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.
In
In
Embodiments of the present invention will be specifically described with reference to the drawings. However, dimensions, materials, shapes, relative arrangements and the like of constituent elements described in the following embodiments are appropriately changed depending on constitutions or various conditions of devices (apparatuses) to which the present invention is applied. Therefore, the scope of the present invention is not limited thereto unless otherwise specified.
An image forming apparatus 100 according to this embodiment will be described with reference to
The external host device 200 is a personal computer, an image reader, the facsimile machine, a network system, a work station or the like. The image forming apparatus 100 includes an operating panel portion 102.
The image forming apparatus 100 is of a cartridge type in which the image is formed on the recording material S in a state in which a plurality of cartridges P contributing to an image forming process and detachably mounted in an image forming apparatus main assembly (hereinafter referred to an apparatus main assembly) 100A. In the image forming apparatus 100 in this embodiment, four process cartridges P (PY, PM, PC, PBk) are detachably mounted. Then, on the recording material S, the full-color image (color mode) or the monochromatic image (monochromatic mode) is formed.
Here, with respect to the image forming apparatus 100, a side where an openable door (openable member) 103 is provided is a front side (front surface side), and a side opposite from the front side is a rear side (rear surface side). Further, left and right are those as seen from the front side of the image forming apparatus 100. Inside the apparatus main assembly 100A, with respect to a predetermined direction from the rear side toward the front side, i.e., the horizontal direction in this embodiment, a first cartridge PY, a second contact RM, a third cartridge PC and a fourth cartridge PBk are provided in the listed order.
Each cartridge P is a process cartridge of a so-called integral type, and the respective cartridges P have the same electrophotographic process mechanism. That is, the respective cartridges P includes electrophotographic photosensitive (member) drums (hereinafter referred to as drums) 1 (1Y, 1M, 1C, 1Bk), respectively, as rotatable image bearing members. Further, as electrophotographic process means actuable on the drums 1, chargers 2, developing units (developing devices) 3 (3Y, 3M, 3C, 3Bk) and cleaning units 4 are provided.
The charger 2 is a charging means for electrically charging the drum 1 to a predetermined polarity and a predetermined potential, and is charging roller in this embodiment. The developing unit 3 includes a developing roller 3a as a developer carrying member for developing, as a toner image, an electrostatic latent image formed on the drum surface by carrying a developer (hereinafter referred to as a toner) and then by supplying the toner to the drum 1, and a toner accommodating portion 3b where the toner to be fed to the developing roller 3a is accommodated (stored).
The colors of the toners accommodated in the toner accommodating portions 3b of the developing units 3 of the cartridges P are different from each other. In this embodiment, the toner of yellow (Y) is accommodated in the toner accommodating portion 3b of the developing unit 3Y of the first cartridge PY. The toner of magenta (M) is accommodated in the toner accommodating portion 3b of the developing unit 3M of the second cartridge PM. The toner of cyan (C) is accommodated in the toner accommodating portion 3b of the developing unit 3c of the third cartridge PC. The toner of black (Bk) is accommodated in the toner accommodating portion 3b of the developing unit 3Bk of the fourth cartridge PBk.
The cleaning unit 4 is a cleaning means for cleaning the drum surface by removing the toner remaining on the drum surface after the toner image is primary-transferred from the drum 1 onto a transfer belt 11 described later. In this embodiment, as a cleaning member, a cleaning blade is used.
Each cartridge P is placed at and supported by a mounting portion corresponding to a cartridge supporting member (hereinafter referred to as a tray) 6 as a movable member described later with respect to a longitudinal direction (rotational axis direction of the drum 1) which is a left-right direction.
In
Then, in a state in which each cartridge P is positioned and fixed in the mounting position in the apparatus main assembly 100A, a driving coupling portion of the apparatus main assembly 100A is connected with a driven-coupling portion of each cartridge P. As a result, a driving force is capable of being transmitted from each of the driving portions of the apparatus main assembly 100 to the corresponding P. The drum 1 of each cartridge P is rotationally driven, by being subjected to transmission of the driving force described above, in the counter clockwise direction indicated by an arrow at a predetermined peripheral speed (process speed). Further, other rotatable members such as the developing rollers 3a of the developing units 3 are also rotationally driven in predetermined directions at predetermined speeds.
Further, to electric power receiving portions of the cartridges P, electric power supplying portions of the apparatus main assembly 100A are electrically connected, respectively. As a result, from power source portions of the apparatus main assembly 100A to the respective cartridges P, predetermined biases such as a charging bias and a developing bias are applicable. In the above, each of the driven-coupling portion, the driving coupling portion, the electric power receiving portion, the electric power supplying portion and the power source portion is omitted from illustration.
Above the four cartridges P, a laser scanner unit LB as an exposure means is provided. This unit LB outputs laser light Z modulated corresponding to the image information for the corresponding cartridge P. A constitution in which the laser light Z enters the cartridge P through an exposure window portion 5 of the cartridge P to subject the surface of the drum 1 to main scanning exposure is employed.
Further, below the four cartridges P, an intermediary transfer belt unit 7 is provided. This unit 7 includes, as a belt stretching member, a driving roller 8, a tension roller (supporting roller) 9 and an assist roller 10. Around these three rollers, a transfer belt (intermediary transfer member) 11 as a flexible endless belt is stretched. A transfer brush belt portion in an upper side between the driving roller 8 and the tension roller 9 opposes the drums 1 of the four cartridges P.
In this embodiment, the driving roller 8 is provided in a rear side than the first cartridge PY in the apparatus main assembly 100A. The tension roller 9 is provided in a front side than the fourth cartridge PBk in the apparatus main assembly 100A. The assist roller 10 is provided in the neighborhood of and below the driving roller 8.
The driving roller 8, the tension roller (supporting roller) 9 and the assist roller 10 are disposed in parallel to each other with respect to the rotational axis direction as the left-right direction. The tension roller 9 is always moved and urged, at bearing portions (not shown) of left and right end portions thereof by an urging means (not shown) such as a spring, in a direction in which a predetermined tension as a constant pressure is applied to the transfer belt 11. The transfer belt 11 is rotationally driven in the clockwise direction indicated by an arrow at the substantially same peripheral speed as the rotational peripheral speed of the drum 1 by rotational drive of the driving roller 8 in the clockwise direction indicated by an arrow. The tension roller 9 and the assist roller 10 are rotated by the rotation of the transfer belt 11.
Inside the transfer belt 11, as a transfer member (primary transfer means) opposing the lower drum surfaces of the respective cartridges P via the upper-side belt portion, four transfer brushes 12 (12Y, 12M, 12C, 12Bk) are provided in parallel with respect to the longitudinal direction as the left-right direction.
Of these transfer brushes 12Y, 12M, 12C and 12Bk, the transfer brushes 12Y, 12M and 12C corresponding to the first to third cartridges, PY, PM and PC are fixed to and supported by a common movable supporting member 105. The transfer brush 12Bk corresponding to the fourth cartridge PBk is fixed and disposed, as a specific transfer member, in a predetermined (constant) position.
That is, the drum (first image bearing member) 1Bk corresponding to the transfer brush 12Bk as the specific transfer member (first transfer member) is disposed downstream of the drums 1Y, 1M and 1C, as second image bearing members, corresponding to other transfer brushes (second transfer members) 12Y, 12M and 12C, respectively, with respect to a movement direction of the transfer belt 11.
The supporting member 105 is moved in an up-down direction while being kept in a horizontal state in an inside of the transfer belt 11 by a shift mechanism 107 (
The supporting member 105 is driven by the shift mechanism 107, so that the transfer brushes 12Y, 12M and 12C are moved between a contact position A with the upper-side belt portion toward the lower surfaces of the drums 1Y, 1M and 1C and a spaced position B from the drums 1Y, 1M and 1C. In this embodiment, the supporting member 105 and the shift mechanism 107 constitute a moving means for moving the transfer brushes 12Y, 12M and 12C, relative to the corresponding drums 1Y, 1M and 1C, between the contact position A and the spaced position B.
That is, as shown in (a) of
That is, the spaced position B of the transfer brushes 12Y, 12M and 12C is a position in which the transfer brushes 12Y, 12M and 12C are moved in the spaced direction from the corresponding positions 1Y, 1M and 1C by a predetermined amount to be placed in an eliminated state of formation of the primary transfer nips.
On the other hand, with respect to the transfer brush 12Bk fixed and disposed in the constant position, a state in which the transfer brush 12Bk is urged against and contacted to the upper-side belt portion toward the lower surface of the drum 1Bk of the fourth cartridge PBk is maintained. As a result, with respect to the fourth cartridge PBk, a state in which the transfer belt 11 contacts the drum 1Bk therefor to form the primary transfer nip at the contact position NBk is created.
In this state, in both of the color mode and the monochromatic mode, a winding amount of the tension 9 around the tension roller 9 is increased compared with that in a state in which the primary transfer nip is not formed. Accordingly, in both of the color mode and the monochromatic mode, stability of the drive of the transfer belt 11 is stabilized.
As described above, the transfer brush 12Bk as the specific transfer member is maintained in an urged state toward the drum 1Bk via the transfer belt 11 irrespective of the movement of the transfer brushes 12Y, 12M and 12C as other transfer members to the contact position A or the spaced position B.
Further, at a belt contact portion of the driving roller 8 of the unit 7, a secondary transfer roller 13 is urged against and contacted to the transfer belt toward the predetermined 8 at a predetermined urging force to form a secondary transfer nip (secondary transfer position).
Below the unit 7, a feeding tray (feeding cassette) 14 in which sheets of the recording material S on which the image is to be formed are stacked and accommodated, a pick-up roller 15, a single-sheet separating and feeding roller 16, a registration roller 17 and the like are provided. The recording material S is a sheet-like member on which the image is formable and includes plain paper, resin-coated paper, an OHP sheet, an envelope, a postcard, and the like (hereinafter referred to as a sheet) of various types including a regular (standard) size and an irregular (non-standard) size.
The feeding tray 14 is freely inserted (mounted) into and pulled out (demounted) from the front side of the apparatus main assembly 100A (front loading). The pick-up roller 15, the single-sheet feeding roller 16 and the registration roller 17 are disposed inside and in the rear side of the apparatus main assembly 100A. Further, in the inside and the rear side of the apparatus main assembly 100A, an upward sheet feeding path (vertical feeding path) 18 from the feeding roller 16 toward an upper discharge opening 21 of the apparatus main assembly 100A is provided. Along this feeding path 18, from a lower side to an upper side, the single-sheet feeding roller 16, the registration roller 17, the secondary transfer roller 13, a fixing device 19, a discharging roller pair 20 and the discharge opening 21 are provided successively in the listed order.
An upper surface portion of the apparatus main assembly 100A constitutes a discharge tray 22. The fixing device 19 fixes an unfixed toner image, as a fixed image, formed on the sheet S. In this embodiment, the fixing device 19 includes a pressing roller and a heating unit including a fixing film to be heated by a heating means, and fixes the toner image on the sheet S at a fixing nip formed between the pressing roller and the heating unit. The discharging roller pair 20 includes discharging rollers. The feeding path 18 includes a guide plate for guiding the sheet and the like but the guide plate and the like are omitted from
The color mode is an image forming mode in which a four-color based full-color image is formed on the sheet S by using all of the drums 1Y, 1M, 1C and 1Bk of the first to fourth cartridges PY, PM, PC and PBk.
When this color mode is selected and designated, the control circuit portion 101 operates, in the case where the supporting member 105 is not positioned in a predetermined raised position A, the shift mechanism 107 to move upward the supporting member 105 to the predetermined raised position A. As a result, as shown in
The drum 1 of each cartridge P is rotationally driven at a predetermined control speed. Also the transfer brush belt 11 is rotationally driven in the same direction as a rotational direction of the drum 1. The laser scanner unit LB is also driven. In synchronization with the driving of the laser scanner unit LB, the charging roller 2 in each cartridge P uniformly electrically charges the surface of the drum 1 to predetermined polarity and potential. The laser scanner unit LB scans (exposes) the surface of each drum 1 with the laser light 8 depending on the image signal for a corresponding color. As a result, an electrostatic latent image corresponding to the image signal for the corresponding color is formed on the surface of the drum 1. The electrostatic latent image is developed by the developing roller of the developing unit 3 into a toner image.
By the above-described electrophotographic image forming process operation, a yellow (Y) toner image which corresponds to the yellow (Y) component of a full-color image is formed on the drum 1Y of the first cartridge PY, and the toner image is primary-transferred onto the transfer belt 11. On the drum 1M of the second cartridge PM, a magenta (M) toner image which corresponds to the magenta (M) component of the full-color image is formed, and the toner image is primary-transferred onto the transfer belt 11 so that it is superposed on the Y toner image which has already been transferred on the transfer belt 11.
Further, on the drum 1C of the third cartridge PC, a cyan (C) toner image which corresponds to the cyan (C) component of the full-color image is formed, and the toner image is primary-transferred onto the transfer belt 11 so that it is superposed on the Y and M toner images which have already been transferred the transfer belt 11. On the drum 1Bk of the fourth cartridge PK, a black (Bk) toner image which corresponds to the black (Bk) component of the full-color image is formed, and the toner image is primary-transferred onto the transfer belt 11 so that it is superposed on the Y, M and C toner images which have already been transferred on the transfer belt 11.
To the transfer brushes 12Y, 12M, 12C and 12Bk, a primary transfer bias may also be applied as desired. In this way, an unfixed full-color superposed transfer toner image is formed on the transfer belt 11 by the toner images of the four colors of Y, M, C and Bk.
On the other hand, from the feeding tray 14, at predetermined control timing, sheets S are separated and fed one by one. The sheet S is introduced into the secondary transfer nip, as a contact portion between the secondary transfer roller 13 and the transfer belt 11, at predetermined control timing by the registration roller 17. As a result, in a process in which the sheet S is nipped and fed through the secondary transfer nip, the superposed four color toner images on the transfer belt 11 are successively secondary-transferred collectively onto the surface of the sheet S. To the secondary transfer roller 13, a secondary transfer bias may also be applied as desired.
Then, the sheet S on which the toner images are secondary-transferred is introduced into the fixing device 19 to be subjected to fixing, and thereafter is discharged by the discharging roller pair 20, as a full-color image-formed product, onto the discharge tray 22 through the discharge opening 21.
The monochromatic mode (reduced color mode) is an image forming mode in which a monochromatic image is formed on the sheet S by using only the drum 1Bk of the fourth cartridge PBk, for forming the Bk toner image, of the first to fourth cartridges PY, PM, PC and PBk.
When this monochromatic mode is selected and designated, the control circuit portion 101 operates, in the case where the supporting member 105 is not positioned in a predetermined lowered position B, the shift mechanism 107 to move downward the supporting member 105 to the predetermined lowered position B. As a result, as shown in
For that reason, the upper-side belt portion of the transfer belt 11 is spaced from the lower surfaces of the drums 1Y, 1M and 1C of the first to third cartridges PY, PM and PC and is held in a state in which the formation of the primary transfer nips is eliminated. That is, the transfer brushes 12Y, 12M and 12C are held in the spaced state from the opposing drums 1Y, 1M and 1C.
On the other hand, the transfer brush 12Bk fixed and disposed in the constant position is maintained in a surface in which the transfer brush 12Bk is urged against and contacted to the upper-side belt portion of the transfer belt 11 toward the lower surface of the drum 1Bk of the corresponding fourth cartridge PBk at a predetermined urging force. As a result, the fourth cartridge PBk is placed in a state in which formation of the contact position NBk, i.e., the primary transfer nip is maintained.
Then, the drum 1Bk of the fourth cartridge PBk is rotationally driven at a predetermined speed. Incidentally, with respect to the first to third cartridges PY, PM and PC, drive of the drums 1Y, 1M and 1C is not made, so that the image forming operation is not performed. The transfer belt 11 is rotationally driven in the same direction as the rotational direction of the drum 1Bk at a speed corresponding to the rotational speed of the drum 1Bk. The laser scanner unit LB is driven. In this state, image formation by only the fourth cartridge PBk is executed, so that the Bk toner image is formed on the drum 1Bk. Then, the Bk toner image is successively primary-transferred onto the transfer belt 11.
Thereafter, similarly as in the case of the color mode, from the feeding tray 14, one of sheets S is separated and fed. At the secondary transfer nip, the Bk toner image in the transfer belt 11 side is secondary-transferred onto the sheet S. The sheet S is introduced into the fixing device 19 to be subjected to image fixing, and thereafter is discharged by the discharging roller pair 20, as a monochromatic image-formed product, onto the discharge tray 22 through the discharge opening 21.
With use of each of the cartridges P for image formation, the toner accommodated in the toner accommodating portion 3b of the developing unit 3 is consumed. Then, when the toner is consumed to such an extent that an image of a quality satisfactory to a user who has purchased the cartridge P cannot be formed, commercial value of the cartridge P is lost.
Therefore, e.g., the image forming apparatus is provided with means 108Y, 108M, 108C and 108Bk (
In the image forming apparatus 100 in this embodiment, the exchange (replacement) of the cartridge P is performed through a method (type) in which the cartridge P is placed on a contact tray 6 as a movable member of a pulling-out type from the apparatus main assembly 100A, and then is replaced in a front-access manner in order to improve usability.
That is, in the front side of the apparatus main assembly 100A, an opening 104 through which the cartridge P passes in order that the cartridge P is inserted into the cartridge accommodating portion inside the apparatus main assembly 100A, and on the other hand, is taken out from the cartridge accommodating portion is provided. Further, the openable door 103 movable between a closed position C where the opening 104 is closed (covered) as shown in
In this embodiment, the door 103 can be opened and closed and can be rotationally moved relative to the apparatus main assembly 100A about a hinge shaft portion 103a provided in a lower side of the door 103. That is, the door 103 is rotated about the hinge portion 103 in an erection direction, so that the door 103 can be placed in the closed state relative to the apparatus main assembly 100A as shown in
Incidentally,
The tray 6 is, in the state in which the door 103 is positioned in the closed position C as shown in
In this state, as described above, each cartridge P is urged against the positioning portion of the apparatus main assembly 100A at the positioned portion thereof by the urging operation of the urging means of the apparatus main assembly 100A, thus being positioned and fixed in the predetermined mounting position. Then, the driving coupling portion of the apparatus main assembly 100A is mechanically connected to the driven-coupling portion of each cartridge P. Further, the electric power supply portion of the apparatus main assembly 100A is electrically connected to the electric power receiving portion of each cartridge P.
When the door 103 is opened from the closed position C of
Then, by the upward movement of the tray 6 from the accommodating position to the movable position, also each cartridge P is raised from the mounting position, so that all of the drums 1 are held in the spaced state from the transfer belt 11. Further, the connection of the electric power supplying portion of the apparatus main assembly 100A with the electric power receiving portion of each cartridge P is also eliminated. In
In (a) of
In (b) of
Then, the tray 6 is pulled out from the movable position of
The tray 6 is movable along the rail member 106 in a direction perpendicular to (crossing) the longitudinal direction (rotational axis direction of the drum 1) of each cartridge P while supporting the four cartridges P. The tray 6 is capable of arranging and mounting thereon the four cartridges P with respect to the movement direction between the movable position of
As described above, the transfer 11 and the drum 1 of each cartridge P are spaced from each other during the movement of the tray 6, and therefore the tray 6 is moved from the movable position of
The tray 6 supports each cartridge P in the mounting and demounting position E so as to be detachably movable upward. Further, the tray 6 supports each cartridge P by moving each carriage P downward. Therefore, the old (used-up) cartridge P to be replaced is raised and removed upward from the tray 6. Then, the new cartridge P is engaged in and placed on the tray 6 from above.
The tray 6 pulled out to the mounting and demounting position E is reversely capable of being pushed in and moved to the movable position as the inside position in the apparatus main assembly 100A through the opening 104. An arrow G represents a pushing-in movement direction of the tray 6. Also during this movement, the drum 1 of each cartridge P is held in the spaced state from the transfer belt 11, and the tray 6 is moved from the mounting and demounting position E to the movable position without contact between the drum 1 and the transfer belt 11.
Further, in a state in which the tray 6 is pushed into the movable position in a predetermined manner (
By a subsequent operation interrelated with the closing operation of the door 103, a connecting and engaging operation of the driving coupling portion of the apparatus main assembly 100A with the driven-coupling portion of each cartridge P is performed. Similarly, the urging means performs the urging operation to urge the positioned portion of each cartridge P against the positioning portion of the apparatus main assembly 100A, so that each cartridge P is held in a positioned state in a predetermined mounting position. Further, a state in which the electric power supplying portion of the apparatus main assembly 100A is electrically connected to the electric power receiving portion of each cartridge P is created. Thus, each cartridge P is restored to a state in which each cartridge P is capable of performing the image forming operation (
In (a) of
In this embodiment, in a state in which all of the cartridges P are positioned and fixed in the mounting positions, respectively, the drum 1Bk of the cartridge PBk is constituted to be positioned in a side closer to the transfer belt 11 than the drums 1Y, 1M and 1C of other cartridges PY, PM and PC.
Further, the contact position NBk between the drum 1Bk and the transfer belt 11 in this embodiment is disposed by being spaced downward from the rectilinear line L by a distance X in (a) of
Further, as shown in (b) of
As described above, during execution of the monochromatic mode, the contact position NBk of the transfer belt 11 with the drum 1Bk on which the Bk image is to be formed is disposed in a direction in which other drums 1Y, 1M and 1C which are not be subjected to the image formation are spaced from the transfer belt 11. For that reason, it is possible to sufficiently space other drums 1Y, 1M and 1C, which are not subjected to the image formation, from the transfer belt 11. As a result, in a relatively simple constitution, without upsizing the image forming apparatus 100, a degree of deterioration due to the contact of the transfer belt 11 with other drums 1Y, 1M and 1C which are not subjected to the image formation during output of the Bk image can be reduced.
Further, as shown in (b) of
Further, as described above, in the case where the contact position NBk of the transfer belt 11 with the drum 1Bk for forming the Bk image is disposed in a direction in which other drums 1Y, 1M and 1C are spaced from the transfer belt 11, the cartridge PBk can be disposed in a direction in which the cartridge PBk is lower than other cartridges. As a result, even when the toner accommodating portion 3b of the cartridge PBk is set to have a larger size than those of other cartridges by the distance X with respect to the up-down direction as indicated by a broken line in
In this embodiment, the cartridge PBk is disposed in the downstreammost position of the tray 6 with respect to the pulling-out direction of the tray 6 when the cartridges PY, PM, PC and PBk are exchanged (replaced). When the cartridge PBk is disposed in this position, there is no influence on an exchanging property of the cartridges PY, PM, PC and PBk even when the cartridge PBk is set to have the size larger than those of other cartridges by the distance X. As a result, in the image forming apparatus 100 in this embodiment, without changing the size of the apparatus main assembly 100A and impairing the cartridge exchanging property, the cartridge PBk having a high frequency of use can be replaced with a high-volume cartridge with respect to an accommodated toner amount.
An image forming apparatus 100 according to Embodiment 2 will be described with reference to
With this disposition of the tray 6, also the intermediary transfer belt unit 7 is disposed in the inclined state so as to be in parallel to the inclined tray 6. The pulling-out movement direction F of the tray 6 from the apparatus main assembly 100A and the pushing-in movement direction G of the tray 6 into the apparatus main assembly 100A are set so as to be in parallel to a rectilinear line connecting the contacts 1Y, 1M and 1C of the first to third cartridges PY, PM and PC.
Constitutions of the image forming apparatus 100 other than the above-described constitution are the same as those in the image forming apparatus 100 in Embodiment 1. In this embodiment, the first to fourth cartridges PY, PM, PC and PBk are disposed in the listed order in the direction directed toward the lower-right position in the inclined state. For that reason, in a spacing relationship with the unit LB, even when the toner accommodating portions 3b of the first to fourth cartridges PY, PM, PC and PBk are set to have larger sizes in the listed order with respect to the up-down direction, the cartridges can be disposed in the apparatus main assembly 100A without changing a size of the apparatus main assembly 100A. In
In this case, also in Embodiment 2, similarly as in Embodiment 1, the contact between position the drum 1Bk and the belt 11 is disposed in the spaced direction of the belt 11 from the drums 1Y, 1M and 1C. For that reason, the size of the toner accommodating portion 3b of the contact PBk can be set at a further large value by the distance X described above.
Further, also in this embodiment, similarly as in Embodiment 1, the cartridge PBk is disposed in the downstreammost position of the tray 6 with respect to the pulling-out direction of the tray 6 when the cartridges PY, PM, PC and PBk are exchanged (replaced). When the cartridge PBk is disposed in this position, there is no influence on an exchanging property of the cartridges PY, PM, PC and PBk even when the toner accommodating portion 3b of the cartridge PBk is set to have the size larger than those of other cartridges by the sum of a distance corresponding to the above-described inclination disposition and the distance X. As a result, in the image forming apparatus 100 in this embodiment, without changing the size of the apparatus main assembly 100A and impairing the cartridge exchanging property, the cartridges can be replaced with cartridges having volumes, with respect to an accommodated developer amount, larger than those in Embodiment 1.
(1) In Embodiments 1 and 2 described above, although the transfer brushes 12Y, 12M, 12C and 12Bk are used as the transfer member, the transfer member may also be a pad member or a roller member (transfer roller).
(2) The plurality of the image bearing members may also have a device constitution such that the image bearing members are assembled with the apparatus main assembly 100A or the tray 6 and are disposed in a tandem manner. Further, it is also possible to employ an image forming apparatus constitution in which the plurality of image bearing members are disposed in a tandem manner with respect to the up-down direction. It is also possible to employ an image forming apparatus constitution in which the number of the plurality of image bearing members is not limited to 4 in Embodiments 1 and 2 but may also be 2, 3 and 5 or more. The type of the rotatable image bearing members is not limited to the drum type but may also be an endless belt type.
(3) The rotatable and flexible endless belt member disposed opposed to the drums 1Y, 1M, 1C and 1Bk is not limited to the intermediary transfer member onto which the toner images are transferred from the drums 1 as in Embodiments 1 and 2, but may also be a recording material feeding member for feeding the recording material onto which the images are transferred from the drums 1.
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(4) The image forming type of each of the image forming portions is not limited to the electrophotographic type in Embodiments 1 and 2, but may also be an electrostatic recording image forming type using an electrostatic recording dielectric member as the image bearing member, a magnetic recording image forming type using a magnetic recording (magnetic) member as the image bearing member, and other image forming types.
According to the present invention, when the image-formed product using only the image bearing member corresponding to the specific transfer member is outputted, the contact position between the image bearing member and the belt member is disposed in the direction in which other image bearing members are spaced from the belt member. For that reason, it is possible to sufficiently increase the distance of the belt member from other image bearing members. As a result, in the relatively simple constitution, without upsizing the image forming apparatus, a degree of deterioration of other image bearing members and the belt member when the image-formed product using only the image bearing member corresponding to the specific transfer member is outputted.
While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purpose of the improvements or the scope of the following claims.
This application claims priority from Japanese Patent Application No. 031841/2013 filed Feb. 21, 2013, which is hereby incorporated by reference.
Number | Date | Country | Kind |
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2013-031841 | Feb 2013 | JP | national |