Patent Grant
7555242
1. Field of the Invention
The present invention relates to an image forming apparatus utilizing an electrophotographic process, such as a printer, a copying apparatus or a facsimile apparatus, and more particularly to a drive of an image bearing member or a driven member acting on the image bearing member.
2. Description of the Related Art
As an image forming apparatus utilizing for example an electrophotographic process, there is known a color image forming apparatus of so-called in-line type including a plurality of image forming parts, each including an electrophotographic photosensitive member (hereinafter referred to as “photosensitive member”) constituting an image bearing member, and process means which acts on such photosensitive member. In the image forming apparatus of such in-line type, images on the photosensitive member are transferred in succession onto an intermediate transferring member disposed in opposition to the plurality of image forming parts or onto a transfer material on a transfer material bearing member. In general, the plurality of image forming parts are constituted of four image forming parts for respectively forming images of yellow, magenta, cyan and black colors, and a drum-shaped member is used as the photosensitive member (4-drum tandem type).
Also in the image forming apparatus of such in-line type, it is known to integrally construct the photosensitive member and the process means such as developing means, in each image forming part, as a process cartridge, that is rendered detachably mountable in a main body of the image forming apparatus. In such process cartridge system, for example when a developer is used up, the user himself can replace the process cartridge without relying on a service personnel to enable image formation again. Also other consumable parts such as the photosensitive member may also be replaced at the same time, whereby the maintenance ability can be significantly improved.
As an example, an image forming apparatus of the aforementioned 4-drum tandem system will be explained below. Currently, a “4-motor system” as shown in
Also a “1-motor system” as shown in
In the “1-motor system”, an electronic clutch or a mechanical clutch mechanism is utilized for switching over a full-color mode and a mono-color mode. The full-color mode is a multicolor mode in which all four photosensitive members 1a, 1b, 1c and 1d are driven, while the mono-color mode is a monochromatic mode in which for example a photosensitive member 1d for black color only is driven. The “1-motor system” has an advantage in cost, in comparison with the “4-motor system”.
The “4-motor system” tends to become costly, because of an increased number of motors. Also the “4-motor system” may lead to an increased installation space and an increased weight in the structure, and may hinder realizing a compact and low-cost image forming apparatus.
On the other hand, the “1-motor system” may cause an unevenness in the rotation of the photosensitive member, depending on the precision of meshing in the clutch mechanism, thereby conspicuously causing a color misalignment or a banding phenomenon (periodical unevenness in image by a fluctuation in the rotation of the photosensitive member).
Japanese Patent Application Laid-open No. 2003-43781 discloses a technology of driving photosensitive drums for yellow, magenta and cyan colors with a first motor, and driving a photosensitive drum for black color with a second motor.
However, in the technology of Japanese Patent Application Laid-open No. 2003-43781, the first motor also drives developing rollers corresponding to the photosensitive drums driven by the first motor, and the second motor also drives a developing roller corresponding to the photosensitive drum driven by the second motor, and does not pay attention to a driving load relating to the photosensitive drum and the developing roller.
An object of the present invention is to provide an image forming apparatus capable, with a reduced cost, of suppressing an image displacement on an image bearing member and equalizing drive loads for plural drive sources.
Another object of the present invention is to provide an image forming apparatus including a plurality of image bearing members on each of which a toner image is formed, said plurality of image bearing members including plural first image bearing members and a second image bearing member which is different from said plural first image bearing members, a plurality of driven members respectively each of which acts on each of said plurality of image bearing members, wherein, in a first mode, the toner image is formed on each of said plural first image bearing members and said second image bearing member, and in a second mode, the toner image is not formed on said plural first image bearing members and the toner image is formed on said second image bearing member, a first drive device which drives said plural first image bearing members, and a second drive device which drives said second image bearing member, the driven member which acts on said second image bearing member and at least one of the driven members which act on said plural first image bearing members.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Now an image forming apparatus of the present invention will be explained in detail, with reference to the accompanying drawings.
At first, an entire structure of the image forming apparatus will be explained with reference to
The image forming apparatus A is provided, as image forming means, with four image forming parts Pa, Pb, Pc and Pd. In the present embodiment, the image forming parts Pa, Pb, Pc and Pd are the same in structure and functions, except that toners used therein are different in colors thereof.
The image forming parts Pa, Pb, Pc and Pd are equipped, as image bearing members, with four drum-shaped photosensitive members or photosensitive drums 1a, 1b, 1c and 1d, which are disposed in a parallel manner, along a substantially vertical direction. The photosensitive drums are rotated, counterclockwise in
Around the photosensitive drums 1a, 1b, 1c and 1d and along the rotating direction thereof, there are provided charging members 2a, 2b, 2c and 2d, constituting charging devices for uniformly charging the surface of the photosensitive drums 1a, 1b, 1c and 1d, and a scanner unit 3 constituting an exposure device for irradiating the photosensitive drums 1a, 1b, 1c and 1d with laser beams based on image information, thereby forming electrostatic latent images on the photosensitive drums 1a, 1b, 1c and 1d. Also at a downstream side, there are provided developing devices (developing units) 4a, 4b, 4c and 4d for depositing toners of developers onto the electrostatic latent images thereby forming toner images, and an electrostatic transfer device 5 for transferring the toner images on the photosensitive drums 1a, 1b, 1c and 1d onto a transfer material S. At a further downstream side, cleaning devices (cleaning units) 6a, 6b, 6c and 6d, for removing residual toners remaining on the photosensitive drums 1a, 1b, 1c and 1d after the transfer step, are provided.
In the present embodiment, the four image forming parts Pa, Pb, Pc and Pd, including the photosensitive drums 1a, 1b, 1c and 1d, the charging members 2a, 2b, 2c and 2d, the scanner unit 3, the developing devices 4a, 4b, 4c and 4d and the cleaning devices 6a, 6b, 6c and 6d, form images of respectively different colors (yellow, magenta, cyan and black). In the following description, yellow color is represented as Y, magenta as M, cyan as C and black as Bk.
In the present embodiment, the photosensitive drum, the charging device, the developing device and the cleaning device are integrally formed as a cartridge, thus constituting process cartridges 7a, 7b, 7c and 7d. The process cartridges 7a, 7b, 7c and 7d are detachably mounted in the main body B of the apparatus, by mounting means such as guide grooves 34A1, 34A2, 34A3, 34A4, 34B1, 34B2, 34B3 and 34B4 to be explained later (cf.
In the following, each component of the image forming apparatus A will be explained in detail, making reference also to
In the following description, a front side of the image forming apparatus A means a side from which the process cartridges are inserted into the main body B of the apparatus, namely a right-hand side in
The photosensitive drum 1a, 1b, 1c or 1d is an OPC photosensitive drum, formed by coating an external periphery of an aluminum cylinder having a diameter for example of 25 mm, with an organic photoconductor layer. The photosensitive drum 1a, 1b, 1c or 1d is rotatably supported, at both ends thereof, by support members. The photosensitive drum 1a, 1b, 1c or 1d is rotated in a direction X in
The charging devices 2a, 2b, 2c and 2d may be of contact charging type, including charging members in contact with the photosensitive drums 1a, 1b, 1c and 1d. The present embodiment employs, as charging members, conductive rollers (charging rollers) 2a, 2b, 2c and 2d having a roller shape. The surfaces of the photosensitive drums 1a, 1b, 1c and 1d are uniformly charged by contacting the charging rollers 2a, 2b, 2c and 2d with the surfaces of the photosensitive drums 1a, 1b, 1c and 1d and applying a charging bias voltage to the charging rollers 2a, 2b, 2c and 2d.
The scanner unit 3 is provided at an approximately horizontal direction to the photosensitive drums 1a, 1b, 1c and 1d. In the present embodiment, for each photosensitive drum, a single laser diode (not shown) emits an image light corresponding to the image signal. The image light irradiates a polygon mirror 9, rotated at a high speed by a scanner motor (not shown). The polygon mirror is provided, for example, for every two photosensitive drums. The present embodiment has two polygon mirrors, namely a first polygon mirror 9a and a second polygon mirror 9b. The first polygon mirror 9a is used for causing a scanning motion of the light irradiating the image forming parts Pa, Pb for forming the images of Y and M colors, and the second polygon mirror 9b is used for causing a scanning motion of the light irradiating the third and fourth image forming parts Pc, Pd for forming the images of C and Bk colors. The image light reflected by the polygon mirror 9 selectively exposes the surface of the already charged photosensitive drum, through an imaging lens 10a, 10b, 10c or 10d provided respectively on the photosensitive drum 1a, 1b, 1c or 1d. In this manner, an electrostatic latent image, corresponding to the image signal, is formed on the photosensitive drum 1a, 1b, 1c and 1d. As shown in
The developing devices 4a, 4b, 4c and 4d are provided with toner containers 41, serving as developer containers for containing developers of Y, M, C and Bk colors respectively (in the present embodiment, negatively chargeable non-magnetic one-component developers (toners)). The toner container 41 includes a developing roller 40a, 40b, 40c or 40d serving as a developer carrying member, a developer carrying mechanism 42, a toner supply roller 43 serving as a developer supply member, and a developing blade 44 serving as a developer regulating member. The toner in the toner container 41 is fed by the carrying mechanism 42 to the toner supply roller 43. The toner is applied, by the toner supply roller 43 and the developing blade 44 contacted with the external periphery of the developing roller 40a, 40b, 40c or 40d, onto the external periphery of the developing roller 40a, 40b, 40c or 40d, and is given an electrostatic charge. The toner supply roller 43 rotates in a direction Z in
In the present embodiment, a transfer belt (electrostatic transfer belt) 11 is provided as a transfer material conveying member, which cyclically moves so as to be opposed to and to contact all the photosensitive drums 1a, 1b, 1c and 1d. The transfer belt 11 electrostatically sucks and conveys the transfer material S. The transfer belt 11 is constituted of a film-shaped member of a thickness of about 110 μm having a volume resistivity of 1011 to 1014 Ω·cm. The transfer belt 11 is supported in a vertical direction by rollers of 3 axes. The transfer belt 11 electrostatically sucks the transfer material S on the external periphery at the left-hand side in
Also in positions respectively opposed to the 4 photosensitive drums 1a, 1b, 1c and 1d, transfer rollers 12a, 12b, 12c and 12d are provided, in parallel, as transfer devices so as to be in contact with the inner periphery of the transfer belt 11. These transfer rollers 12a, 12b, 12c and 12d apply, across the transfer belt 11, positive charges to the transfer material S. By electric fields formed by such charges, the negatively charged toner images on the photosensitive drums 1a, 1b, 1c and 1d are transferred onto the transfer material S contacted with the photosensitive drums 1a, 1b, 1c and 1d.
In more detail, the transfer belt 11 of the present embodiment is formed by an endless belt having a peripheral length of about 560 mm and a thickness of 110 μm, which is supported by 3 rollers, including a drive roller 13, an idler roller 14 and a tension roller 15. The transfer belt 11, by a driving power transmitted to the drive roller 13 from a drive source, is cyclically moved (rotated) in a direction indicated by an arrow (clockwise) in
Also there may result a situation where the transfer material S is not supplied by an unexpected reason and the toner remains on the transfer belt 11. In the present embodiment, in such a situation, the transfer belt 11 is rotated faster with a certain peripheral speed difference between the photosensitive drums 1a, 1b, 1c and 1d and the transfer belt 11. By such operation, the toner on the transfer belt 11 can be efficiently transferred to the photosensitive drums 1a, 1b, 1c and 1d and recovered by the cleaning devices 6a, 6b, 7c and 6d in the process cartridges 7a, 7b, 7c and 7d, whereby the transfer belt 11 can be cleaned.
A feed unit 16 serves to supply and convey the transfer material S to the image forming parts Pa, Pb, Pc and Pd, and contains plural transfer materials S in a feed cassette 17. At an image forming operation, a feed roller 18 (D-shaped roller) and paired registration rollers 19 are driven in rotation in response to the image forming operation. The transfer materials S in the feed cassette 17 are separated and fed one by one by the feed roller 18, and a leading end of the transfer material S impinges on the paired registration rollers 19 to form a loop. Thereafter the transfer material S is fed, so as to be in synchronization with a predetermined image start position, by the paired registration rollers 19 to the transfer belt 11. Also in a position opposed to the idler roller 14, an electrostatic suction roller 22, for electrostatic attraction of the transfer material S onto the transfer belt 11, is contacted with the transfer belt 11.
A fixing part 20 as a fixing device fixes the unfixed toner image, transferred onto the transfer material S, onto the transfer materials. The fixing part 20 includes a pair of rotated fixing rollers (a heat roller 21a and a pressure roller 21b pressed thereto), and applies, in the contact part thereof, heat and a pressure to the transfer material S. Thus the transfer material S, having received the transfer of the toner images from the photosensitive drums 1a, 1b, 1c and 1d, is conveyed, in passing through the fixing part 20, by the paired fixing rollers 21a, 21b. In this operation, the transfer material S receives heat and a pressure by the paired fixing rollers 21a, 21b. Thus, for example in a multi-color mode to be explained later, toner images of plural colors are fixed onto the transfer material S.
In the following description, an image forming operation will be explained, by a full-color image formation as an example. The process cartridges 7a, 7b, 7c and 7d are activated in succession, according to the timings of image formation (operations of forming images to be recorded on the transfer material S), and, in response to such activations, the photosensitive drums 1a, 1b, 1c and 1d are rotated in directions indicated by arrows shown in
Thus electrostatic latent images are formed on the peripheries of the photosensitive drums 1a, 1b, 1c and 1d. The developing rollers 40a, 40b, 40c and 40d in the developing devices 4a, 4b, 4c and 4d transfer the toners to a low-potential part of the electrostatic latent images. Thus toner images are formed (developed) on the peripheries of the photosensitive drums 1a, 1b, 1c and 1d. Subsequently, a leading end of the toner image, formed on the periphery of the photosensitive drum 1a at a most upstream side in the conveying direction of the transfer material S, is brought by rotation to a position substantially opposed to the transfer belt 11. The paired registration rollers 19 feed the transfer material S to the transfer belt 11, in such a manner that, at such timing, a recording start position of the transfer material S coincides with such opposed position.
The transfer material S is, being pinched between the electrostatic suction roller 22 and the transfer belt 11, pressed to the external periphery of the transfer belt 11. Also by a voltage application between the transfer belt 11 and the electrostatic suction roller 22, charges are induced in the transfer materials, constituted of a dielectric material, and a dielectric layer of the transfer belt 11, whereby the transfer material S is electrostatically sucked onto the external periphery of the transfer belt 11. Thus the transfer material S is stably attracted to the transfer belt 11, and is conveyed to the transfer part N of the most downstream photosensitive drum 1d. In the conveying of the transfer material S, by the electric fields formed between the photosensitive drums 1a, 1b, 1c and 1d and the transfer rollers 12a, 12b, 12c and 12d, the toner images on the photosensitive drums 1a, 1b, 1c and 1d are transferred in succession onto the transfer material S. The transfer material S, having received the transfers of toner images of 4 colors, is separated by the curvature of the belt drive roller 13 (curvature separation) from the transfer belt 11, and is conveyed to the fixing part 20. The transfer material S, after being subjected to a thermal fixation of the toner image in the fixing part 20, is discharged by paired discharge rollers 23, in a state with an image bearing surface downward, onto a discharge part 24 outside the main body B of the apparatus A.
(Process Cartridge)
The process cartridge 7a will be explained below in more detail.
The process cartridge 7a is divided into a photosensitive member unit 50, containing a photosensitive drum 1a, a charging roller 2a and a cleaning device 6a, and a developing unit 4a, including for example a developing roller 40a for developing the electrostatic latent image on the photosensitive drum 1a. In the photosensitive member unit 50, the photosensitive drum 1a is rotatably supported, by bearings (left bearing 31A and right bearing 31B) (cf.
The developing unit 4a includes a developing roller 40a which is contacted with the periphery of the photosensitive drum 1a at the image formation and is rotated in a direction Y (clockwise) shown in
The developing unit 4a is supported, about supporting shafts 49 respectively provided in bearing members 47 which are mounted on both ends of the longitudinal direction of the developing roller 40a (direction of rotary axis of the developing roller 40a), in such a manner that the entire developing unit 4a is capable of a rocking motion by pins 48 with respect to the photosensitive member unit 50. Thus the developing unit 4a is formed as a structure suspended by the photosensitive member unit 50.
The developing unit 4a is constantly urged by a pressure spring 54 constituting urging means, in a state where the process cartridge 7a is left alone, in such a manner that the developing roller 40a is in contact with the photosensitive drum 1a by a rotation moment about the support shafts 49. The state where the process cartridge 7a is left alone means a state where the process cartridge 7a is not mounted in the main body B of the apparatus A. Further, the toner container 41 of the developing unit 4a is integrally provided with a rib 46a, to be contacted by separating means (to be explained later) of the main body B of the apparatus A, when the developing roller 40a is to be separated from the photosensitive drum 1a.
(Mounting/Detaching of Process Cartridge)
Now a mounting/detaching operation of a process cartridge 7d will be explained with reference to
As explained above, the process cartridge 7d in a state left alone is in a state in which the developing roller is constantly contacted with the photosensitive drum as shown in
Thus, the process cartridge 7d is mounted in the main body B of the apparatus A, by inserting, along the guide grooves 34A4 and 34B4, the bearing (left bearing 31A and right bearing 31B) which supports the photosensitive drum 1d along a direction indicated by an arrow in the illustration. At such operation, the transfer belt 11 is retracted for example together with a front door C (cf.
In the main body B of the apparatus A, the process cartridge is pressed in the following manner. As shown in
When the door C is opened, the rod 71 moves in a direction indicated by a broken-lined arrow in
Then, when the process cartridge 7d is inserted and the door C is closed, the rod 71 moves in a direction indicated by a solid-lined arrow in
As shown in
The separating cams 80a, 80b, 80c and 80d cause the developing rollers 40a, 40b, 40c and 40d to be contacted with or separated from the photosensitive drums 1a, 1b, 1c and 1d in the following manner. In the present embodiment, as shown in
The stepping motor 91 causes rotation of the separating cams 80a, 80b, 80c and 80d, and, by such rotation, the separating cams 80a, 80b, 80c and 80d cause, by means of the ribs 46a, 46b, 46c and 46d, a rocking motion in the developing units 4a, 4b, 4c and 4d of the process cartridges 7a, 7b, 7c and 7d. Thus the developing rollers 40a, 40b, 40c and 40d are contacted with or separated from the photosensitive drums 1a, 1b, 1c and 1d. Thus the positions of the developing rollers 40a, 40b, 40c and 40d with respect to the photosensitive drums 1a, 1b, 1c and 1d are switched between a contact position in contact with the photosensitive drums 1a, 1b, 1c and 1d and a separated position separated from the photosensitive drums 1a, 1b, 1c and 1d.
In the present embodiment, there can be selected three modes, which are:
(i) a standby state (standby state) in which, in the image forming parts Pa, Pb, Pc and Pd of all the Y, M, C, Bk colors, the separating cams 80a, 80b, 80c and 80d are in contact, at maximum radii thereof, with the ribs 46a, 46b, 46c and 46d, whereby all the developing rollers 40a, 40b, 40c and 40d are separated from the photosensitive drums 1a, 1b, 1c and 1d;
(ii) a full-color state (full-color mode) in which, in the image forming parts Pa, Pb, Pc and Pd of all the Y, M, C, Bk colors, the separating cams 80a, 80b, 80c and 80d assume a minimum radius position thereof and are separated from the ribs 46a, 46b, 46c and 46d, whereby all the developing rollers 40a, 40b, 40c and 40d are contacted with the photosensitive drums 1a, 1b, 1c and 1d; and
(iii) a mono-color state (mono-color mode) in which, in the image forming parts Pa, Pb and Pc, the developing rollers 40a, 40b and 40c are separated from the photosensitive drums 1a, 1b and 1c and, only in the image forming part Pd for Bk color, the developing roller 40d is in contact with the photosensitive drum 1d.
In the multi-color mode, in the image forming parts Pa, Pb, Pc and Pd of Y, M, C, Bk colors, the developing rollers 40a, 40b, 40c and 40d are contacted, in succession in this order and with a certain time interval, with the photosensitive drums 1a, 1b, 1c and 1d to execute an image formation. Also similarly in the separation of the developing rollers 40a, 40b, 40c and 40d from the photosensitive drums 1a, 1b, 1c and 1d, the developing rollers 40a, 40b, 40c and 40d are separated, in succession in this order and with a certain time interval, from the photosensitive drums 1a, 1b, 1c and 1d.
The separating cam drive apparatus 90 is controlled by a controller 200 of an engine control part, which controls the entire operations of the image forming apparatus A. The controller 200 is provided with an operation part, a control part and a memory part, and executes a sequence control of the separating cam drive apparatus 90 according to a control program for the separating means, stored in the memory part. Thus the controller 200 has a function as control means for the separating cams 80a, 80b, 80c and 80d.
(Process Cartridge Drive Apparatus)
Now there will be explained an operation mechanism, when the process cartridges 7a, 7b, 7c and 7d are mounted in the main body B of the apparatus A.
At the mounting of the process cartridges 7a, 7b, 7c and 7d in the main body B of the apparatus A, as shown in
Such separated state is maintained always while the power supply is turned off and while the developing operation is not conducted. Therefore, while the process cartridges 7a, 7b, 7c and 7d are mounted but not used for a prolonged period, the developing rollers 40a, 40b, 40c and 40d are always separated from the photosensitive drums 1a, 1b, 1c and 1d. It is thus possible to securely prevent a permanent deformation of the roller layers, resulting from a prolonged contact of the developing rollers 40a, 40b, 40c and 40d with the photosensitive drums 1a, 1b, 1c and 1d.
In the following description, there will be explained a drive structure for the photosensitive drums 1a, 1b, 1c and 1d and the developing rollers 40a, 40b, 40c and 40d, and operations thereof in each of the multi-color mode and the mono-color mode.
As explained above, the “4-motor system” involves drawbacks of a possibly higher cost, an increased weight of the apparatus and a possibly larger space occupied by the drive apparatus. Also the “1-motor system” involves a drawback resulting from an uneven rotation of the photosensitive member caused by a meshing in the clutch.
Therefore the present embodiment adopts a “2-motor system”, as illustrated in a conceptual view in
In the case of such a “2-motor system”, in the Bk mono-color mode, the photosensitive drum 1d for Bk is driven while the drive power transmission to other photosensitive drums 1a, 1b and 1c can be terminated by stopping the rotation of the motor itself, whereby a clutch part may be dispensed with. It is therefore possible to avoid drawbacks such as an aggravation in a color misalignment or a banding phenomenon, resulting from a rotation unevenness in the photosensitive drums and caused by an accumulated eccentricity of the meshing error in the clutch part or of the precision of constituent parts.
In the “2-motor system”, under a condition of a constant drive gear ratio, the load torque ratio becomes 3:1, thus resulting in a large difference in the loads. However, such unbalance in the load torques can be resolved by optimizing the torque distribution, in consideration not only of the photosensitive drums but also the developing rollers to which the drive power is transmitted from a same drive source. It is therefore rendered possible to utilize two same motors. It is therefore possible to avoid a mistake of erroneously mounting a different motor at the assembling operation, and an advantage in cost can be realized. This system will be explained below in more details.
At first, an outline of the entire drive system is shown in
In the present embodiment, as shown in
The first motor 101A drives, along a first photosensitive drum driving train (hereinafter referred to as “drum drive train”) Td1, a first idler gear 102A in a succeeding stage to the first motor 101A, first and second precedent-stage gears 103A1 and 103A2, and photosensitive drum driving gears (hereinafter called “drum drive gears”) 104a, 104b and 104c. It thus rotates the photosensitive drums 1a, 1b and 1c, respectively provided in the process cartridges 7a, 7b and 7c for the images of Y, M and C colors.
At the same time, the first motor 101A is connected, along a first developing roller drive train Tr1 and across 2 idler gears, to a clutch gear 107a corresponding to the image forming part Pa for forming a yellow image. The 2 idler gears are a first-stage idler gear 105A and a second-stage idler gear 106A. Finally it meshes with an input gear for the process cartridge 7a for Y color image, thereby driving the developing roller 40a.
The second motor 101B drives, like the first motor 101A, along a second drum drive train Td2, a second idler gear 102B in a succeeding stage to the second motor 101b, a third precedent-stage gear 103B and a fourth drum drive gear 104d. It thus rotates the photosensitive drum 1d, provided in the process cartridge 7d for the Bk image.
At the same time, the second motor 101B is connected, as in the first motor 101A, along a second developing roller drive train Tr2 and across 3 idler gears, to second, third and fourth clutch gears 107b, 107c, 107d. The 3 idler gears are a first-stage idler gear 105B, a second-stage idler gear 106B1 and a third-stage idler gear 106B2. Also the second, third and fourth clutch gears 107b, 107c, 107d correspond to the image forming parts Pb, Pc and Pd for forming the images of M, C and Bk colors. Finally it meshes with input gears for the process cartridges 7b, 7c and 7d for M, C and Bk images, thereby driving the developing rollers 40b, 40c and 40d.
Thus, among the plurality of image bearing members, plural first image bearing members 1a, 1b and 1c execute toner image formation in a first mode (multi-color mode) but do not execute toner image formation in a second mode (mono-color mode), while the second image bearing member 1d, different from the plural first image bearing members 1a, 1b and 1c among the plurality of image bearing members, executes toner image formation both in the first mode and in the second mode. In other words, in a first mode, the toner image is formed on each of said plural first image bearing members and said second image bearing member, and in a second mode, the toner image is not formed on said plural first image bearing members and the toner image is formed on said second image bearing member. The first drive device 101A drives the plural first image bearing members 1a, 1b and 1c, while the second drive device 101B drives the second image bearing member 1d, the developing roller or driven member 40d acting on the second image bearing member 1d and at least a driven member acting on the plural first image bearing members 1a, 1b and 1c. The driven member is a member to be driven by a driving source.
Also in the present embodiment, the first drive device 101A drives at least a driven member, acting on the plural first image bearing members 1a, 1b and 1c.
In the present embodiment, the first drive device 101A and the second drive device 101B have objects of a same number, to which the driving power is supplied.
Thus, in the present embodiment, the drive apparatus 100 is equipped with 2 motors, i.e. the first motor 101A and the second motor 101B, for driving the photosensitive drums 1a, 1b, 1c and 1d of the image forming parts Pa, Pb, Pc and Pd. In particular in the present embodiment, each of the 2 motors 101A, 101B bears the loads of 4 rollers, in order to optimize the torque distribution.
In the following description, the function of the drive apparatus 100 in an image output operation will be explained in a multi-color mode and in a mono-color mode.
(Multi-Color Mode)
In the multi-color mode, as explained above, a full-color image can be obtained by forming images of Y, M, C and Bk colors in the image forming parts Pa, Pb, Pc and Pd.
In the multi-color mode, when an image output operation is initiated by a print signal, the 2 motors 101A, 101B for driving the process cartridges 7a, 7b, 7c and 7d and the drive motor for the transfer belt 11 are activated. In this state, in the first and second developing roller drive trains Tr1, Tr2, all the clutches, namely the clutch gears 107a, 107b, 107c and 107d are disconnected, so that all the developing rollers 40a, 40b, 40c and 40d do not rotate.
Then, when the stepping motor 91 of the separating cam drive apparatus 90 is rotated, as shown in
Similarly the second, third and fourth clutch gears 107b, 107c, 107d are turned on in succession, whereby the developing rollers 40b, 40c, 40d are contacted in succession with predetermined time intervals (corresponding to a time required by the separating cam 80a, 80b, 80c or 80d to rotate by a cam phase difference θ shown in
Thus, as shown in a state (c) in
In this state, as shown in
After the completion of image formation in the image forming part Pa, the stepping motor 91 rotates further, whereby the separating cams 80a, 80b, 80c and 80d further rotate counterclockwise from the state (c) shown in
In the present embodiment, after the developing rollers 40a, 40b, 40c and 40d are separated from the photosensitive drums 1a, 1b, 1c and 1d in all the image forming parts Pa, Pb, Pc and Pd, the rotation of the first motor 101A and the second motor 101B for driving the process cartridges 7a, 7b, 7c and 7d and of the drive motor for the transfer belt 11 is terminated.
(Mono-Color Mode)
In the mono-color mode, when an image output operation is initiated by a print signal, the second motor 101B for driving the process cartridge 7d and the drive motor for the transfer belt 11 are activated. In this state, in the second developing roller drive train Tr2, all the clutches, namely the clutch gears 107b, 107c and 107d are disconnected, so that the developing rollers 40b, 40c and 40d do not rotate. Also in the present embodiment, the first motor 101A is stopped, and the gear clutch 107a in the first developing roller drive train Tr1 is disconnected, so that the developing roller 40a does not rotate.
Then, as in the transition from the state (b) to (c) in
After the separating cam 80d starts to rotate, the clutch gear 107d provided in the second developing roller drive train Tr2 is turned on to rotate the developing roller 40d. Immediately thereafter, the stepping motor 91 rotates by a predetermined amount to rotate the separating cam 80d counterclockwise by a predetermined amount (corresponding to a phase θ′), whereby the rib 46d of the process cartridge 7d being released from being pushed up by the separating cam 80d. Thus, the development frame member 45 of the process cartridge 7d executes a rocking motion by the urging power of the pressure spring 54, whereby the developing roller 40d and the photosensitive drum 1d are contacted to initiate the image formation.
In this state, as shown in
After the completion of the mono-color mode, the stepping motor 91 rotates further to rotate the separating cam 80d counterclockwise to a position separated from the rib 46d of the process cartridge 7d. Thus, in all the image forming parts Pa, Pb, Pc and Pd of 4 colors, the developing rollers 40a, 40b, 40c and 40d assume a state separated from the photosensitive drums 1a, 1b, 1c and 1d. Subsequently the clutch gear 107d is turned off to terminate the rotation of the developing roller 40d. Thus the image output in the mono-color mode is terminated.
In the present embodiment, after the developing roller 40d is separated from the photosensitive drum 1d in the image forming part Pd, the rotation of the second motor 101B for driving the process cartridge 7d and of the drive motor for the transfer belt 11 is terminated.
Thus the “2-motor system” allows to adapt to the mono-color mode, when it is necessary to stop the photosensitive drums 1a, 1b and 1c therein, by simply stopping the first motor 101A. Even when the first motor 101A is stopped, the second motor 101B still functions to drive the photosensitive drum 1d and the developing roller 40d, thereby enabling the image formation in the mono-color mode.
Thus, in the present embodiment, the image forming apparatus A has a first mode (multi-color mode) and a second mode (mono-color mode), which are different in the number of image forming parts used for image formation, among the plurality of image forming parts Pa, Pb, Pc and Pd. Also the plurality of image forming parts Pa, Pb, Pc and Pd include a second image forming part Pd which forms an image in both the first mode and the second mode, and plural first image forming parts Pa, Pb and Pc which form images in the first mode but do not form images in the second mode. In the present embodiment, the second image forming part is an image forming part for Bk color, while the plural first image forming parts are image forming parts for Y, M and C colors. Also the image forming apparatus A includes a first drive source (first motor) 101A, and a second drive source (second motor) 101B. The first drive source supplies the photosensitive drums 1a, 1b and 1c of the image forming parts Pa, Pb and Pc for Y, M and C, with a driving power. The second drive source supplies the photosensitive drum 1d of the image forming part Pd for Bk color and the developing roller 40d, with a driving power.
The second drive source 101B may further supply at least one developing roller (developing rollers 40b, 40c and 40d in the present embodiment) in the image forming parts Pa, Pb and Pc for Y, M and C colors, with the driving power. Also the first drive source 101A may further supply at least one developing roller (developing roller 40a in the present embodiment) in the image forming parts Pa, Pb and Pc for Y, M and C colors, with the driving power. Preferably the first drive source 101A and the second drive source 101B respectively have a same number of objects of supply of drive power.
In this manner, it is unnecessary, in the mono-color mode, to rotate the first motor 101A which serves to drive the process cartridges 7a, 7b and 7c for Y, M and C colors. It is therefore possible to reduce the operating noises in the mono-color mode printing, thus providing an advantage in consideration of noise standards as represented by “Blue Angel”. Also a power saving is possible in the electric power consumption of the main body B of the apparatus A.
Also a clutch mechanism is provided in a drive train, which transmits the drive power to at least one developing roller (all in the present embodiment), among the developing rollers of the plurality of image forming parts provided in the image forming apparatus A. Therefore, in such an image forming part, the developing roller may be driven at a timing different from the drive timing of the photosensitive drum. It is thus possible to elongate the service life of the developing roller, by driving the developing roller according to the contact/separation timings of the developing roller to/from the photosensitive drum.
Even in the image output in the mono-color mode, in case of employing a transfer material S of a high basis weight, the contact between the photosensitive drum in the single image forming part and the transfer belt 11 may be unable to provide a sufficient conveying power for the transfer material S depending on the temperature/humidity conditions, thereby resulting in a deteriorated precision of the image output. The transfer material S of a high basis weight means a cardboard or a small-sized paper such as a postcard.
However, a sufficient conveying power for the transfer material S can be secured, also in the mono-color mode, by contacting the photosensitive drum and the transfer belt 11 not only in one image forming part Pd but in a plurality of image forming parts. In such case, in order to prevent a frictional contact between the photosensitive drum and the transfer belt 11, the photosensitive drums to be contacted with the transfer belt 11 are rotated. In the present embodiment, because of the presence of the aforementioned clutch mechanisms (clutch gears 107a, 107b, 107c) for the developing rollers, the rotation of the first motor 101A does not necessarily rotate the developing roller 40a in synchronization. It is therefore possible, in the case of contacting a plurality of photosensitive drums with the transfer belt 11 in the mono-color mode, to avoid a waste of the service life of the developing roller.
Also in the “2-motor system”, a following structure, different from the present embodiment, is conceivable in consideration of the load balance in driving the photosensitive drums. More specifically it is conceivable that the first motor 101A drives the photosensitive drums 1a and 1b for Y and M colors and the second motor 101B drives the photosensitive drums 1c and 1d for C and Bk colors. In such case, it is necessary, in order to interrupt the transmission of drive power to the photosensitive drum 1c in the Bk mono-color mode, to provide a clutch mechanism between the second motor 101B and the drum drive gear 104c.
However, such clutch mechanism, when present, increases for example an eccentricity because of its structure, thereby increasing a variation in the rotation speed in the clutch output. As a result, drawbacks such as an aggravation in a color misalignment or a banding phenomenon may be encountered as in the “1-motor system” in which four photosensitive drums 1a, 1b, 1c and 1d are driven by a single motor. Also when the precision of components is improved excessively in order to avoid these drawbacks, a problem in cost may be arise. Therefore, the “2-motor system” of the present embodiment is superior to a structure in which 4 photosensitive drums are divided into 2 and 2.
In the “2-motor system” of the present embodiment, the first motor 101A drives the photosensitive drums 1a, 1b and 1c for 3 colors of Y, M and C, while the second motor 101B drives the photosensitive drum 1d for Bk color, and the second motor 101B also drives developing rollers for colors different from Bk. As the drive sources have approximately equalized loads, it is rendered possible to achieve a simpler structure and a lower cost by the use of same drive sources and an optimized load balance for the drive sources.
The drive apparatus 100 is controlled by the controller 200 of the engine control part, which controls the entire operations of the image forming apparatus A. As described above, the controller 200 is provided with an operation part, a control part and a memory part, and executes a sequence control of the drive apparatus 100 according to a control program for the drive apparatus 100, stored in the memory part. Thus the controller 200 has a function as control means for the drive apparatus 100. The controller 200 is capable of independently controlling the drive of the first motor 101A and of the second motor 101B.
(Gear Structure in Drum Drive Train)
In the following description, detailed structures of the first and second drum drive trains Td1, Td2 will be explained.
In the first drum drive train Td1 in the present embodiment, a gear (motor gear) provided on the drive shaft of the first motor 101A meshes with a larger-diameter gear of a first idler gear 102A. A smaller-diameter gear of the first idler gear 102A meshes with larger-diameter gears of first and second precedent-stage gears 103A1, 103A2. Then a smaller-diameter gear of the first precedent-stage gear 103A1 meshes with drum drive gears 104a, 104b, and a smaller-diameter gear of the second precedent-stage gear 103A2 meshes with a drum drive gear 104c.
On the other hand, in the second drum drive train Td2, a gear (motor gear) provided on the drive shaft of the second motor 101B meshes with a larger-diameter gear of a second idler gear 102B. A smaller-diameter gear of the second idler gear 102B meshes with a larger-diameter gear of a third precedent-stage gear 103B. Then a smaller-diameter gear of the third precedent-stage gear 103B meshes with a drum drive gear 104d.
In the present embodiment, the first and second drum drive trains Td1, Td2 have certain tooth number ratios among the mutually meshing gears. More specifically, from the gears (motor gears) provided on the drive shafts of the first and second motors 101A, 101B constituting the drive sources to the precedent-stage gears 103A1, 103A2 and 103B, the mutually meshing gears are connected with a tooth number ratio of 1/N1. N1 indicates a natural number and N1 may be different for each meshing. The precedent-stage gears 103A1, 103A2 and 103B respectively mesh directly with the drum drive gears 104a, 104b, 104c and 104d. The drum drive gears 104a, 104b, 104c and 104d are provided on the shafts of the photosensitive drums 1a, 1b, 1c and 1d, and rotate with same periods as the photosensitive drums 1a, 1b, 1c and 1d.
In the present embodiment, the first motor 101A and the second motor 101B have a same structure, and the first idler gear 102A and the second idler gear 102B have a same structure. Also the first to third precedent-stage gears 103A1, 103A2 and 103B, and the drum drive gears 104a, 104b, 104c and 104d respectively have a same structure. In the following description, therefore, motors or gears of a same structure will be represented by a symbol without an appendix unless a particular distinction is necessary, and will be explained collectively.
In the present embodiment, the gears in the drum drive train have the following tooth numbers:
Thus, the present embodiment adopts a tooth number ratio of 1/4 between (i) and (ii), and a tooth number ratio of 1/2 between (ii) and (iii).
Now, for the purpose of ease of understanding, let us consider a case of a 2-stage reduction of a gear on the shaft of motor 101→an idler gear 102→a precedent-stage gear 103, with a reducing ratio of ½ between each pair of meshing gears. A speed variation in one rotation of the precedent-stage gear 103 is schematically shown in
As will be apparent from a synthesized waveform shown in
Also as shown in
Z1/Z2=1/(N2×N3) (N3 being natural number)
This relation allows to obtain a same rotation speed in the photosensitive drum 1, at an exposure (
More specifically, the present embodiment adopts conditions of N2=2, Z1=30 and Z2=120. Therefore, in the present embodiment, there stands Z1/Z2=30/120=1/4=1/(2×N3) and N3 becomes 2.
It is thus possible, for each photosensitive drum 1, to cancel a rotation unevenness in the photosensitive drum 1 or an unevenness in the image pitch, caused by gear speed variation components in the drive train from the motor 101 as the drive source to the drum drive gear 104.
In the following, there will be explained a method for reducing a color misalignment among plural color images in the drum drive train Td.
For reducing a color misalignment among plural color images, following two points are important for the drum drive train Td:
(I) For all the plurality of image forming parts, the drum drive gear should have a same speed variation history (profile) per 1 rotation;
(II) In addition to (I), in all the plurality of image forming parts, the transfer should be executed at a same speed within the speed variation of the drum drive gear per 1 rotation.
With respect to (I), in case a plurality of image forming parts, for example two image forming parts Pa, Pb, have different speed variation profiles in the drum drive gears 104a, 104b, a speed difference is generated between the drum drive gears 104a and 104b of the two image forming parts Pa and Pb as shown in
With respect to (II), it is preferable, as shown in
More specifically, in the two adjacent drum drive gears 104a, 104b, maximum distances in the eccentric directions are preferably not the same at least in an image forming operation. Also a maximum phase difference in the eccentric directions is preferably such that, with respect to meshing positions of the drum drive gears 104a, 104b with the precedent-stage gear 103A1, the phase relationship is advanced by an angle θ for the drum drive gear 104b corresponding to the photosensitive drum 1b which is later in the sequence of transfers. Such angle θ preferably satisfies, for a diameter d of the photosensitive drum and a distance Lp between the rotary centers of the adjacent photosensitive drums, a relation:
θ=(πd−Lp)/πd×360[°]
It is thus rendered possible, between the adjacent image forming parts, to execute transfer operations with a same rotation speed of the drum drive gears, or with a same peripheral speed of the photosensitive drums. Based on such concept, the present embodiment is constructed with θ=16.2°, for conditions of d=25 mm and Lp=75 mm.
By matching the speed variation histories of plural gears and also forming a phase difference θ as described above, it is possible, as shown in
More specifically, in the present embodiment, a phase difference of an angle θ is realized in the following manner, between the drum drive gears of the adjacent image forming parts. At the side of the first motor 101A where the drive train is connected directly, the drum drive gears are assembled with a phase difference of an angle θ as described above. The side of the first motor 101A where the drive train is connected directly means the relationship between the drum drive gear 104a and the drum drive gear 104b, and the relationship between the drum drive gear 104b and the drum drive gear 104c.
However, because of the drive structure of the present embodiment described above, the phase difference of angle θ cannot be maintained, by such assembling with a phase difference, between the drum drive gear 104c and the drum drive gear 104d which are not directly connected. Therefore, the present embodiment adopts a phase matching by an electrical control, on the drum drive gear 104c and the drum drive gear 104d.
The drum drive gears 104c, 104d are respectively provided with slits 104cs, 104ds as detection parts for phase detection. Also in the vicinity of these slits 104cs, 104ds, photointerruptors (photosensors) 109c, 109d are provided as phase detection means. Outputs of the photointerruptors 109c, 109d are connected to the controller 200 of the engine control part, which controls the entire operations of the image forming apparatus A. Thus the controller 200 can recognize, during the rotation of the drum drive gears 104c and 104d, the timings of passing of the slits 104cs, 104ds through the photointerruptors 109c, 109d. Based on such timings, the controller 200 can know the phase difference between the drum drive gears 104c, 104d.
The controller 200 executes, through a motor control part, an electrical feedback control on the first and second motors 101A, 101B so as to obtain a desired phase difference between the drum drive gears 104c and 104d. In the present embodiment, the controller 200 checks such phase difference prior to an image forming operation, for example in an initializing operation of the apparatus, and executes the feedback control on the first and second motors 101A, 101B. Thus, in the present embodiment, the controller 200 has a function as phase matching control means for the drum drive gears 104c and 104d.
It is thus possible to form a phase difference of a predetermined angle θ between the plural drum drive gear, even in a drum drive train where the drive train is not directly connected and an assembling with a phase difference is not usable.
It is also preferable, in addition to the optimization of the conditions for rotation speed variation in the photosensitive drums, to also optimize conditions for rotation speed variation in the transfer belt 11.
More specifically, in order to reduce the color misalignment among the images of plural colors on the transfer material S, it is necessary that the conveying speed for the transfer material S, or the speed of the transfer belt 11, is the same at the transfer positions for the images of respective colors. For this purpose, a diameter D of the drive roller 13 for the transfer belt 11 (a shaft driving the transfer belt 11), a thickness t of the transfer belt 11, and a distance Lp between the rotary centers of the adjacent photosensitive drums preferably satisfy a relation:
Lp=π(D+t).
More specifically, in the present embodiment, the drive roller 13 has a diameter D of 23.8 mm, the transfer belt 11 has a thickness t of 110 μm, and the adjacent photosensitive drums have a distance Lp of 75 mm between the rotary centers.
It is thus rendered possible to maintain the transfer belt 11 at a same speed at the transfers of the images of respective colors, within a speed variation of the transfer belt 11 caused by a vibration of the drive roller 13.
Also in order to reduce the color misalignment, it is preferable to adopt a following condition, in addition to or in place for the aforementioned optimization of the speed variation conditions of the transfer belt 11.
More specifically, a distance between the transfer positions, of the toner image from the photosensitive drum to the transfer material S, between the two image forming parts adjacent in the conveying direction of the transfer material S, is preferably approximately an integral multiple of the external peripheral length of the drive roller 13 for the transfer belt 11 (shaft for driving the transfer belt 11).
More specifically, in the present embodiment, the distance between the transfer positions is the same as the distance between the rotary centers of the adjacent photosensitive drums, and is 75 mm. Also the drive roller 13 has a diameter of 23.8 mm. Therefore, the distance between the transfer positions is approximately 1 time of the external peripheral length of the drive roller 13.
As explained in the foregoing, the present embodiment adopts a “2-motor system” in the structure of drive power transmission relating to the image formation, to prevent the drawbacks in the “4-motor system” of a possibly higher cost, an increased weight of the apparatus and a possibly larger space occupied by the drive apparatus, and to prevent the drawbacks of an aggravation in the color misalignment and in the banding phenomenon, resulting from an uneven rotation of the photosensitive member caused by a meshing in the clutch, which is required in the drum drive train in the “1-motor system”, thereby allowing to provide an image forming apparatus, capable of achieving a low cost and a high image quality.
The present embodiment adopts a “2-motor system”, in which a single motor 101A drives at least the photosensitive drums 1a, 1b and 1c for Y, M and C colors, and another motor 101B drives the photosensitive drum 1d for Bk color and the developing roller 40d. It is thus made possible to flexibly achieve a multi-color/mono-color mode switching involving contact/separation of transfer belt and photosensitive drums, and to control the image forming operation in each mode. It is thus made possible to reduce the operating noises in a mono-color image output and to avoid wasting the service lives of the transfer belt and the process cartridge, thus providing images of a high image quality until the end of the service life of the image forming apparatus.
Also since one motor 101A drives 3 photosensitive drums and 1 developing roller while the other motor 101B drives 1 photosensitive drum and 3 developing rollers, the motors have approximately equalized loads, so that same motors may be employed to improve the cost and the assembling property.
In the following description, another embodiment of the present invention will be explained. As the image forming apparatus of the present embodiment has a basic structure similar to that of the embodiment 1. Therefore, components of function or structure the same or similar to those in embodiment 1 will be represented by the same symbols and will not be explained in detail, and description will be made on different parts.
In embodiment 1, the developing roller 40a for yellow color is driven by the first motor 101A, while the developing rollers 40b, 40c and 40d for M, C and Bk colors are driven by the second motor 101B. Also in consideration of the service life of the developing units, during the image output in the multi-color mode, the developing rollers 40b and 40c for M and C colors are separated from the photosensitive drums 1b and 1c, and are interrupted from the drive power transmission. In such case, a load change may be generated in the second motor 101B, eventually leading to a local speed variation in the photosensitive drum 1b or a shock to the entire image forming apparatus A. Therefore, an image defect may be induced in an extreme case.
In case the transmission of drive power to the developing rollers 40b and 40c for M and C colors is not interrupted until the completion of the transfer step of the photosensitive drum 1d in order to avoid such phenomenon, there results a waste of service life particularly in the process cartridges 7b and 7c for M and C colors.
This, in the embodiment, as shown in
In the present embodiment, the first motor 101A is connected, along a first developing roller drive train Tr1 and through a first-stage idler gear 105A and a second-stage idler gear 106A, to clutch gears 107a, 107b for Y and M colors. Finally it meshes with input gears of the process cartridges 7a, 7b for Y and M color images, thereby driving the developing rollers 40a and 40b. On the other hand, the second motor 101B is connected, along a second developing roller drive train Tr2 and through a first-stage idler gear 105B and a second-stage idler gear 106B, to clutch gears 107c, 107d for C and Bk colors. Finally it meshes with input gears of the process cartridges 7c, 7d for C and Bk color images, thereby driving the developing rollers 40c and 40d.
In order to avoid a shock, the drive of each developing roller is not stopped until the completion of a transfer step of an image from a photosensitive drum, driven by the first or second motor 101A or 101B which transmits the drive power to such developing roller.
In the present embodiment of such structure, it is only necessary, in the image forming parts Pc and Pd for C and Bk color images, to delay the separation of the developing roller for C color until the completion of the transfer step in the image forming part for Bk color. It is thus possible to suppress a waste in the service life of the process cartridge.
In the following description, still another embodiment of the present invention will be explained. As the image forming apparatus of the present embodiment has a basic structure similar to that of the embodiment 1. Therefore, components of function or structure the same or similar to those in embodiment 1 will be represented by the same symbols and will not be explained in detail, and description will be made on different parts.
A drive structure other than those in embodiments 1 and 2 may be employed for the developing rollers 40a, 40b and 40c for Y, M and C colors, if a certain margin is available in a motor output or in a service life of the process cartridge including the developing roller and the like. For example, all the developing rollers 40a, 40b and 40c for Y, M and C colors may be driven by the second motor 101B.
Thus, the present invention is applicable by driving the developing rollers 40a, 40b and 40c for Y, M and C colors either by the first motor 101A or by the second motor 101B. Also in such case, as in the aforementioned embodiments 1 and 2, the drum drive train does not require a clutch mechanism for switching the mono-color/multi-color mode, and the drawbacks of aggravation in banding or color misalignment can be avoided.
Also in certain cases, there may be employed a structure having a clutch mechanism each in a drive train for the developing roller 40d for Bk color and in the developing rollers 40a, 40b and 40c for Y, M and C colors. It is thus possible to dispense with 2 clutches among 3 colors of Y, M and C, thereby achieving a cost reduction. Also a flexible control is possible for an image output mode in which, in a mono-color mode, the photosensitive drums are contacted with the transfer belt 11 in plural positions and are rotated, in order to improve the conveying property for the transfer material S.
While the present invention has been described with reference to specific embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. For example, embodiments 1-3 assume an image forming apparatus of a direct transfer type, in which toner images are transferred in succession from a plurality of photosensitive drums onto a transfer material, conveyed by a transfer belt, thereby forming a recorded image.
However, the present invention is not limited to an image forming apparatus utilizing a transfer belt. For example,
Also the order of toner images to be transferred from the plurality of image forming parts to the transfer-receiving member is not limited to those in the foregoing embodiments. More specifically, in the image forming apparatus of the foregoing embodiments, the image forming parts for forming the images of Y, M, C and Bk colors may be arranged in an arbitrary order along the conveying direction of transfer-receiving member.
Also the aforementioned embodiments assume presence of 4 image forming parts corresponding to Y, M, C and Bk colors, but the present invention is applicable when at least 3 image forming parts are present, and the effects of the present invention can be attained by driving 2 photosensitive drums by a first motor and driving 1 photosensitive drum and at least 2 developing rollers with a second motor.
Also the foregoing embodiments have been explained with the developing rollers as an example of driven members, but the driven members may be any driven members acting on the photosensitive drums, such as charging rollers or cleaning members.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2005-226044, filed Aug. 3, 2005 and Japanese Patent Application No. 2006-206710, filed Jul. 28, 2006 which are hereby incorporated by reference herein in their entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-226044 | Aug 2005 | JP | national |
| 2006-206710 | Jul 2006 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 6795671 | Matsuoka | Sep 2004 | B2 |
| 6889022 | Ehara et al. | May 2005 | B2 |
| 7031642 | Abe | Apr 2006 | B2 |
| 7239829 | Tanaka | Jul 2007 | B2 |
| Number | Date | Country |
|---|---|---|
| 2003-43781 | Feb 2003 | JP |
| 2003-208024 | Jul 2003 | JP |
| 2004-205688 | Jul 2004 | JP |
| 2005-265951 | Sep 2005 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20070031166 A1 | Feb 2007 | US |
