CN100552557C - The coloured image forming device - Google Patents

Abstract

A kind of coloured image forming device comprises: a plurality of drum type photoreceptors be used on each circumferential surface forming the image of different colours, and these photoreceptors have at least two kinds of different diameters; A plurality of drive divisions are used for making each photoreceptor rotate with predetermined circle speed to drive each photoreceptor with diameter corresponding driving speed; The correction signal efferent is used for the output speed correction signal, to proofread and correct the periodic spacings change that comprises in each established image; And drive control part, be used for controlling and driving portion, with the actuating speed of proofreading and correct each photoreceptor by the velocity correction signal, wherein the velocity correction signal is the signal with cycle identical with the swing circle of each photoreceptor.

Description

The coloured image forming device

Technical field

The present invention relates to a kind of coloured image forming device.

Background technology

Known have a kind of coloured image forming device (so-called cascade connection type coloured image forming device) with a plurality of drum type photoreceptors.In the coloured image forming device, it is important that the position deviation (color misalignment) of every kind of color is suppressed to the degree that is difficult for discovering.When color misalignment degree is big, may assess image quality by deterioration.The biggest factor of color misalignment is the periodic crude density on the output image that causes of the off-centre by each photoreceptor.Desirable countermeasure is to reduce the offset of each photoreceptor fully, but cost must enter into consideration and mass productivity between compromise.

In view of this, provide multiple idea, even so that under the identical situation of offset, also can make the color misalignment be difficult for discovering.For example, proposed a kind of equipment, it is arranged to have the ratio (for example, Japanese patent unexamined is looked into and disclosed 7-261499 number) of integer with the girth of each photosensitive drums and the girth of transfer belt.

During mismatch, it is remarkable that the color misalignment becomes on output image for the phase place of the spacing change that causes when the off-centre by each photoreceptor.This point has come into one's own, and has provided a plurality of ideas, is used to mate the eccentric phase place of each photoreceptor on the output image, is difficult for discovering thereby the color misalignment is become.In this case,, be formed on the first-class spaced apart toner pattern (toner image) that has with the lines of the rotating shaft parallel of photoreceptor of sense of rotation, and detect deviation from desired location in order to detect the rotatable phase of each photoreceptor.

Alternatively, known have a kind of photoreceptor, and its storage pulse pattern is used to eliminate the speed fluctuation of one Zhou Xuanzhuan, thus the spacing change that drive stepping motor and reducing is caused by off-centre (for example, look into disclose 63-75759 number) referring to Japanese patent unexamined.

In addition, known have a kind of photoreceptor, and it is by the information about the vibration component of Periodic Rotating change, comes individually the rotational speed of rotor to be used meticulous adjustment so that eliminate its change (for example, look into referring to Japanese patent unexamined disclose 10-78734 number).

Usually, the coloured image forming device comes carries out image to form by three kinds of primary colors and the black that uses yellow, cyan and magenta.The cascade connection type image forming apparatus comprises four photoreceptors corresponding to every kind of color.Under the situation that monochrome image forms, only use the black photosensitive body.

In such image forming apparatus, when forming, monochrome image accounts for whole ratio when high, have only the black photosensitive body by deterioration fast.In this case, on the maintenance time of monochrome and each photoreceptor of other color (yellow, cyan and magenta), produced imbalance.Therefore, when design, the standard proportional that monochrome image forms and coloured image forms is estimated in advance, and, be provided with the serviceable life of photoreceptor according to the ratio of estimating.

In addition, have a kind of image forming apparatus, it prevents that other photoreceptor is driven when monochrome image forms.By doing like this, this image forming apparatus can prevent that formation does not have the photoreceptor of contribution and the deterioration of developer to image.In addition, the translational speed when this image forming apparatus can be arranged to the translational speed (processing speed) of photosensitive surface when monochrome image forms form than coloured image is fast, thereby also is arranged to its print speed faster.

From serviceable life of prolonging the black photosensitive body and with processing speed be provided with viewpoint faster, preferably increase the diameter of photoreceptor.Yet, if only the diameter of black photosensitive body is greater than the diameter of other photoreceptor, will the multiple problem that coloured image forms appear relating to.

Representational one is problem about the color misalignment.Because the swing circle of black photosensitive body is different with the swing circle of other photoreceptor, so can't adopt the technology that is used to mate eccentric direction and makes the color misalignment be difficult for discovering.Simultaneously, so that eliminate under the situation of the speed fluctuation that rotates a circle of photoreceptor, configuration is complicated and cost is in most of the cases increased unfriendly at the correcting pattern of the number that generates photoreceptor.

Even wishing to have is a kind ofly using polytype photoreceptor, every type photoreceptor has under the situation of different-diameter, also can adopt simple configuration and the technology that makes the color misalignment be difficult for discovering.

Summary of the invention

In view of the foregoing, finished the present invention, and the invention provides a kind of technology, using polytype photoreceptor even be used for, every type photoreceptor has under the situation of different-diameter, also can adopt simple configuration to suppress variation with the corresponding image pitch of swing circle of each photoreceptor, make the color misalignment be difficult for discovering whereby.

The invention provides a kind of coloured image forming device, comprise: a plurality of drum type photoreceptors, a plurality of drive division, correction signal efferent and drive control part, wherein a plurality of drum type photoreceptors are used for forming the image of different colours on each circumferential surface, and these photoreceptors have at least two kinds of different diameters; A plurality of drive divisions are used for making each photoreceptor rotate with predetermined circle speed to drive each photoreceptor with diameter corresponding driving speed; The correction signal efferent is used for the output speed correction signal, to proofread and correct the periodic spacing change that comprises in each established image; And drive control part is used for controlling and driving portion, and with the actuating speed of proofreading and correct each photoreceptor by the velocity correction signal, wherein the velocity correction signal is the signal with cycle identical with the swing circle of each photoreceptor.

Because image forming apparatus of the present invention comprises correction signal efferent and drive control part, wherein the correction signal efferent is used for the output speed correction signal, to proofread and correct the periodic spacing change that comprises in each established image, and drive control part is used for controlling and driving portion, to proofread and correct the actuating speed of each photoreceptor by the velocity correction signal, wherein the velocity correction signal is the signal with cycle identical with the swing circle of each photoreceptor, spacing change with cycle identical with the swing circle of each photoreceptor is corrected, thereby can obtain spacing and change repressed image.The spacing change is included in respectively in each image of every kind of color, and is identified as the color misalignment.Therefore, adopt image forming apparatus of the present invention, can obtain to have the image of very little color misalignment.

Description of drawings

Fig. 1 is a key diagram of representing to be used in the present embodiment to proofread and correct the chunk configuration of spacing variance components;

Fig. 2 is the cut-open view of expression according to the configuration of image forming apparatus of the present invention;

Fig. 3 is the key diagram that calculates the part of relevant color alignment from the image forming apparatus shown in Fig. 2;

Fig. 4 A to 4C is the key diagram of an example of the expression toner pattern that is used for color alignment in the present embodiment;

Fig. 5 A and 5B are the key diagrams of the driving mechanism of the photosensitive drums 3 in the image forming apparatus shown in the presentation graphs 3 and the being used to photoreceptor drive motor 45 that drives this photosensitive drums 3;

Fig. 6 represents in the present embodiment, the key diagram of the state that color alignment toner pattern is formed and is measured by color alignment sensor 41;

Fig. 7 be expression be provided with projection 44 and phase detector 43 in case with the key diagram of each the photosensitive drums 3 corresponding state shown in Fig. 3;

Fig. 8 is illustrated in the key diagram that forms the state of aiming at the toner pattern on the photosensitive drums 3 shown in Fig. 3;

Fig. 9 A and 9B are the key diagrams that is used to illustrate about the benchmark anglec of rotation and the relation between the reference phase of Fig. 8;

Figure 10 A to 10E is used for explanation in the present embodiment, because the off-centre of photosensitive drums, and the key diagram that image pitch changes with respect to the benchmark spacing of exposure position and transfer position;

Figure 11 represents in the present embodiment, under the state of the rotatable phase of adjusting photoreceptor, and the key diagram of the peripheral speed variance components of photoreceptor;

Figure 12 represents in the present embodiment, under the state of the rotatable phase of adjusting photoreceptor, and the key diagram of the example of the position of each projection 44;

Figure 13 represents in the present embodiment, under the state that the rotatable phase of each photosensitive drums mates mutually, and the key diagram of the peripheral speed variance components of photoreceptor;

Figure 14 represents that in the present embodiment each Drive and Control Circuit 53 is eliminated the key diagram of the state of peripheral speed variance components;

Figure 15 represents in the present embodiment, under the state that the rotatable phase of each photoreceptor mates mutually, and the key diagram of the example of the position of each projection;

Figure 16 represents in the present embodiment, is used to proofread and correct the key diagram of the different chunk configuration of spacing variance components;

Figure 17 is the key diagram of state of the peripheral speed variance components of each photosensitive drums 3 among the embodiment of expression shown in Figure 16;

Figure 18 represents in the present embodiment, the key diagram of the example of the aligning toner pattern that is provided with for the vision adjustment;

Figure 19 represents in the present embodiment, when the common modulation signal application during to controlled each photoreceptor of rotatable phase, is suppressed the key diagram of the effect of peripheral speed variance components;

Figure 20 represents in the present embodiment, at the rotatable phase of adjusting each photoreceptor, makes the phase place of spacing variance components on the image mutually under the state of coupling, the key diagram of peripheral speed variance components;

Figure 21 represents in the present embodiment, is used to suppress the key diagram of state of modulation signal of the peripheral speed variance components of K photoreceptor;

Figure 22 represents in the present embodiment, is used to proofread and correct the key diagram of the another kind of different chunk configuration of spacing variance components;

Figure 23 represents in the present embodiment, is used to proofread and correct the key diagram of the another kind of different chunk configuration of spacing variance components;

Figure 24 represents that in the present embodiment control part 40a adjusts the key diagram of the state of rotatable phase;

Figure 25 is the key diagram that expression control part 40a adjusts the M and the state of the stop position of C photosensitive drums as follows: these photosensitive drums are stopped and become to make each of rotatable phase of these photosensitive drums to mate with the rotatable phase of Y photosensitive drums;

Figure 26 represents in the present embodiment, and control part 40a measures the spacing variance components of the photosensitive drums of every kind of color, and the process flow diagram of the process of the amplitude of modulation signal and phase place is set based on measurement result;

Figure 27 represents in the present embodiment, the process flow diagram of the details of the process of the spacing variance components of the photosensitive drums of every kind of color of control part 40a measurement;

Figure 28 represents in the present embodiment, first key diagram of the effect of the method for eliminating fine pitch variance components from calibration object;

Figure 29 A and 29B represent in the present embodiment, second key diagram of the effect of the method for eliminating fine pitch variance components from calibration object;

Figure 30 represents in the present embodiment, the 3rd key diagram of the effect of the method for eliminating fine pitch variance components from calibration object;

Figure 31 A and 31B represent in the present embodiment, the 4th key diagram of the effect of the method for eliminating fine pitch variance components from calibration object;

Figure 32 represents in the present embodiment, the process flow diagram of the process different with process shown in Figure 26, and wherein control part 40a measures the spacing variance components of the photosensitive drums of every kind of color, and the amplitude and the phase place of modulation signal are set based on measurement result;

Figure 33 represents in the present embodiment, the process flow diagram of the other process different with process shown in Figure 26, and wherein control part 40a measures the spacing variance components of the photosensitive drums of every kind of color, and the amplitude and the phase place of modulation signal are set based on measurement result;

Figure 34 A and 34B represent in the present embodiment, the peripheral speed variance components of photoreceptor and the oscillogram of spacing variance components;

Figure 35 represents in the present embodiment, is used for driving by each Drive and Control Circuit 53 oscillogram of waveform of the signal of each photoreceptor drive motor 45;

Figure 36 A and 36B represent in the present embodiment, and the amplitude of the range value α of spacing variance components and the velocity correction signal that is used to proofread and correct its circumference change is than the oscillogram of the relation of Av; And

Figure 37 is shown schematically in the present embodiment, and the relational expression of the range value α of spacing variance components and amplitude are than the key diagram of the relation between the Av.

Embodiment

In image forming apparatus of the present invention, image pitch is meant the interval of the point (pixel) of composing images, and in this manual, specifically finger is along the interval of the pixel of the moving direction of the circumference of each photosensitive drums.Although each pixel must be arranged with predetermined space (benchmark spacing), the image of preparing on image forming apparatus comprises local different image pitch, promptly comprises periodic variance components (spacing variance components).Can think that the change of image pitch mainly is that off-centre by photosensitive drums or its driven wheel produces.That is, the peripheral speed of photosensitive drums changes owing to eccentric, and this change is expressed as the change of image pitch.

For example, can be by realize all or part of of correction signal efferent, drive control part and correction signal generating unit by the microcomputer executive control program.Therefore, the entity of velocity correction signal can not be the electric signal of physics, but as the data of the process object of microcomputer.

Here, provide be used for the most general color (such as black, yellow, cyan and magenta) photoreceptor as an example, yet value volume and range of product is not limited thereto.

The velocity correction signal can be the shared signal with photoreceptor of same diameter.Like this, by using shared velocity correction signal, but the configuration of simplified image forming device.

In addition, image forming apparatus of the present invention also can comprise: alignment image formation portion, measurement section and variance components calculating part, and wherein alignment image formation portion is used for forming the alignment image that comprises a plurality of patterns on each photoreceptor; Measurement section is used to measure the position of each pattern of formed alignment image; And the variance components calculating part is used for the measurement result based on each pattern, the amplitude and the phase place of the corresponding spacing variance components of swing circle of calculating and photoreceptor, wherein the correction signal efferent can comprise the correction signal generating unit, is used for generating the velocity correction signal that is used for every kind of diameter based on amplitude and the phase place calculated.

Every kind of photoreceptor can form photoreceptor and a plurality of coloured image by black image and form photoreceptor and form, and wherein black image forms the diameter that photoreceptor has first size, and coloured image forms the diameter that photoreceptor has second size.

In addition, coloured image forms photoreceptor and can form photoreceptor, cyan image by yellow image and form photoreceptor and magenta color image and form photoreceptor and form.

The diameter dimension of black image formation photoreceptor can form the diameter dimension of photoreceptor greater than coloured image.

The velocity correction signal can be the shared signal of the photoreceptor that diameter is identical each other, and the correction signal generating unit can be calculated the amplitude peak of amplitude of spacing change of each photoreceptor that will be employed the velocity correction signal and the mean value of minimum radius, and can be by using the amplitude calculated the formation speed correction signal.Like this, image forming apparatus of the present invention can determine to be applied to the amplitude of the velocity correction signal of a plurality of photoreceptors, is suitable for suppressing the spacing variance components of each photoreceptor.

In addition, at least a portion of correction signal efferent also can comprise switching part and switch control portion, and wherein the switching part velocity correction signal that is used to switch generation is output to or is not output to the state of the drive control part of each photoreceptor; And switch control portion is used for the size according to the amplitude of the spacing variance components of each photoreceptor, switches and the corresponding switching part of photoreceptor.Like this, in the photoreceptor of amplitude less than predetermined amplitude of spacing variance components,, the velocity correction signal is not output by switching switching part.Therefore, can prevent excessive correction.

Image forming apparatus of the present invention also can comprise: the transfer member that is used for the image that transfer printing forms by each photoreceptor, rotatable phase adjustment part with the rotatable phase that is used to adjust photoreceptor, wherein each photoreceptor can be formed photoreceptor and a plurality of coloured image with diameter of second size by the black image of the diameter with first size and forms photoreceptor and form, and each photoreceptor can be with predetermined space along the transfer member setting; The rotatable phase adjustment part can be calculated by each coloured image and be formed the relative misalignment amount that photoreceptor formed and be transferred to the phase place of spacing variance components included in the image on the transfer member, and can adjust rotatable phase, the periodic phase that makes each coloured image form the speed fluctuation of photoreceptor is mated based on the misalignment amount of the phase place of being calculated.

Like this, owing to proofread and correct each coloured image formation photoreceptor of the phase place of cyclical velocity change by shared velocity correction signal, arrive each photoreceptor so will eliminate the velocity correction signal application of eccentric opposite phase with mutual coupling.Therefore, suppressed the spacing change of every kind of color efficiently.

The phase place of cyclical velocity change is the rotatable phase of the reference phase of hereinafter description as the photoreceptor of benchmark.The adjustment of rotatable phase is meant the adjustment to the relative rotatable phase of each identical photoreceptor of diameter dimension.

Notice that transfer member can be banded intermediate transfer element, the toner image that is formed by each photoreceptor is transferred to the surface of this transfer member, yet transfer member is not limited thereto, and can be the transfer member that supports and transmit the paper that is transferred image on it.

Alternatively, image forming apparatus of the present invention also can comprise: the transfer member that is used for the image that transfer printing forms by each photoreceptor; Rotatable phase adjustment part with the rotatable phase that is used to adjust each photoreceptor, wherein each photoreceptor a plurality of coloured images that can be formed photoreceptor by the black image of the diameter with first size and have a diameter of second size form photoreceptor and form, and each photoreceptor can be with predetermined space along the transfer member setting; At least a portion of correction signal efferent also can comprise delay portion, is used to the velocity correction signal of each photoreceptor delay from the correction signal efferent; The rotatable phase that each coloured image forms photoreceptor can be adjusted based on the phase place of calculating in the rotatable phase adjustment part, makes that forming the phase place that photoreceptor formed and be transferred to spacing variance components included in the image of transfer member by each coloured image is mated; And delay portion can be according to based at interval and predefined angle postpones each velocity correction signal, so that have the phase place of eliminating the spacing variance components.

Like this, the color misalignment that the off-centre of photoreceptor is caused is difficult for discovering, because adjusted the rotatable phase that each coloured image forms photoreceptor, makes the phase place of the spacing variance components that comprises in the image mate mutually.In addition, suppressed the spacing variance components of every kind of color efficiently, because with the phase place of each velocity correction signal delay to elimination spacing variance components.

Each photoreceptor can comprise: be used for detecting the reference value used in the control of rotatable phase and the phase detector of output reference signal, wherein at least a portion of correction signal efferent also can comprise the retardation adjustment part of the retardation that is used to adjust delay portion; The retardation adjustment part can be in forming the process of image the phase place of velocity correction signal of benchmark signal and generation, and can result based on the comparison adjust retardation, with the phase place that suppresses the velocity correction signal sequence change with respect to reference signal.Like this, comprise in formation during the image of multipage, can prevent to produce of in time the change of the phase place of velocity correction signal with respect to the rotatable phase of each photoreceptor.

Here, even when shared velocity correction signal is applied to the photoreceptor with mutually the same diameter, still it can be configured to make the phase place of the velocity correction signal that generates in the correction signal generating unit and pre-definedly be the photoreceptor of benchmark (benchmark photoreceptor) coupling, and adjust the phase place of other photoreceptor with respect to the benchmark photoreceptor by delay portion.Can be chosen in the benchmark photoreceptor that has maximum leading phase in the process that photoreceptor is set.

At least a portion of correction signal efferent also can comprise the amplitude adjustment part, is used to be adjusted into the amplitude of the velocity correction signal that each photoreceptor generates.Like this, even with shared velocity correction signal application during to the photoreceptor of diameter with mutually the same size, the velocity correction signal of the corresponding amplitude of amplitude of the spacing variance components of still exportable and each photoreceptor.

In addition, in image forming apparatus of the present invention, each photoreceptor can comprise phase detector and mark addition portion, and wherein phase detector is used for detecting reference position and the output reference signal in that the control of rotatable phase is used; And the mark addition portion is used for to add mark to alignment image according to the output of reference signal.Like this, when print registration image and the adjustment of the amplitude of execution speed correction signal and phase place visually, mark can be used as the benchmark of phase place.

The correction signal generating unit can generate and the opposite velocity correction signal of the cyclical velocity of benchmark photoreceptor change phase place, and the photoreceptor with the amplitude peak that calculates is used as the benchmark photoreceptor.Like this, can guarantee to suppress the spacing variance components of maximum.Therefore, can suppress the color misalignment efficiently.

Each rotatable phase can be determined in the rotatable phase adjustment part, makes other coloured image form the rotatable phase coupling of the rotatable phase and the benchmark photoreceptor of photoreceptor.

In image forming apparatus of the present invention, at interval can be that the adjacent coloured image that contact with transfer member respectively forms the interval between the position of photoreceptor, and can be the different distance of integral multiple with the circumferential length of coloured image formation photoreceptor at interval.

Alternatively, in image forming apparatus of the present invention, the pattern of alignment image can comprise many straight lines that extend perpendicular to the sense of rotation of photoreceptor, and can be calculated the amplitude and the phase place of spacing variance components by measurement section far from the deviation of reference position by the position of measuring every straight line.

It should be noted that stepper motor can be used as the photoreceptor drive motor, however the photoreceptor drive motor be not limited thereto, and can use for example servocontrol DC motor.

In addition, each photoreceptor is a cydariform, yet photoreceptor also can be banded.In this case, the off-centre that is used to drive the driven roller of banded photoreceptor shows as the main variance components of image pitch.Therefore, the present invention is applicable to the driven roller of photoreceptor.

To describe the present invention with reference to the accompanying drawings in detail.From explanation hereinafter, the present invention may be better understood.Especially, hereinafter should to be considered to only be exemplary in the explanation of Miao Shuing, rather than to the restriction of all aspects.

(summary of image forming apparatus)

In the present embodiment, will the summary of the mechanical mechanism of coloured image forming device according to an embodiment of the invention be described.

Fig. 2 is the cut-open view of expression according to the configuration of image forming apparatus of the present invention.The view data that image forming apparatus 50 transmits according to the outside forms multicolor image or monochrome image on predetermined paper.As shown in FIG., image forming apparatus 50 is electrophotographic image-forming apparatus, is made up of exposing unit 1, developing cell 2, photosensitive drums 3, charger 5, cleaning unit 4, intermediate transfer belt unit 8, fixation unit 12, paper transport path S, paper feeding tray 10, discharge tray 15 etc.

The handled view data of image forming apparatus is corresponding with every kind the coloured image that uses black (K or BK), cyan (C), magenta (M) and yellow (Y).Therefore, correspondingly be provided with four developing cells 2 (2a, 2b, 2c, 2d), four photosensitive drums 3 (3a, 3b, 3c, 3d), four chargers 5 (5a, 5b, 5c, 5d) and four cleaning units 4 (4a, 4b, 4c, 4d) with every kind of color.Be attached to the letter representation color after each numeral, make a corresponding to black, b is corresponding to cyan, c corresponding to magenta and d corresponding to yellow.On the circumferential surface of each photosensitive drums 3, form four types electrostatic latent image.Particularly, corresponding to every kind of color, be provided with four image stations.

With the configuration of explanation as one of them image station of the representative of four image stations.Other image station has identical configuration.Therefore, ignore the letter that is attached to after each numeral.Charger 5 is to be used to adopt predetermined potential the surface of photosensitive drums 3 to be carried out the charging device of uniform charging.Except the contact forming roll shown in Fig. 2, the example of charging device comprises the charger of brush type charger and charging type.

Exposing unit 1 is the exposure device that is used for the surface of photoreceptor of charging is carried out the selectivity exposure.As exposure device, can use such as the light emitting devices of EL or LED with the write head that array format is provided with, come the laser scan unit shown in the alternate figures 2 (LSU).LSU 1 has laser irradiating part and mirror polygon.LSU 1 will reflex to the mirror polygon of rotation from the laser beam L of laser irradiating part, so that deflection laser bundle L, thereby the surface of scanning photoreceptor.According to coming modulating lasering beam L by reading the view data that view data that original copy generates or outer computer generate.

By with the laser beam L of view data modulation the photosensitive drums 3 of charging being scanned and exposing, on the surface of photosensitive drums 3, form the image (electrostatic latent image) that has with the corresponding current potential of view data whereby.Any toner that developing cell 2 adopts color K, C, M and Y develop to being formed on electrostatic latent image on the photosensitive drums 3 (make the electrostatic latent image that forms on the photosensitive drums 3 visual).Cleaning unit 4 as hereinafter described in image developing and transfer printing after, remove and also to collect the lip-deep toner that remains in photosensitive drums 3.

Intermediate transfer belt unit 8 is arranged on the top of photosensitive drums 3.Intermediate transfer belt unit 8 comprises intermediate transfer belt 7, intermediate transfer belt driven roller 8-1, intermediate transfer belt tensioning mechanism 8-3, intermediate transfer belt driven roller 8-2, intermediate transfer rollers 6 (6a, 6b, 6c, 6d) and intermediate transfer belt cleaning unit 9.

Intermediate transfer belt driven roller 8-1, intermediate transfer belt tensioning mechanism 8-3, intermediate transfer rollers 6, intermediate transfer belt driven roller 8-2 etc. stretch and drive intermediate transfer belt 7, so that it is rotated along the direction shown in the arrow B.

Intermediate transfer rollers 6 rotatably is supported on the intermediate transfer rollers installation portion of intermediate transfer belt tensioning mechanism 8-3 of intermediate transfer belt unit 8.Be used for to be formed on the transfer bias that toner image on the photosensitive drums 3 is transferred to intermediate transfer belt 7 and be applied in intermediate transfer rollers 6.

Intermediate transfer belt 7 is configured to contact with the corresponding photosensitive drums 3 of every kind of color.The toner image that is formed in lip-deep every kind of color of photosensitive drums 3 is transferred on the intermediate transfer belt 7 in proper order by being applied to the transfer bias on the intermediate transfer rollers 6.Therefore, color toner image (multi-color toner image) is transferred on the intermediate transfer belt 7 in the mode of multilayer.Intermediate transfer belt 7 forms ring-type by the film with about 100 μ m to the 150 μ m of thickness and makes.

As mentioned above, intermediate transfer rollers 6 contacts with the back side of intermediate transfer belt 7, and it is to be used for toner image is transferred to transfer device on the intermediate transfer belt 7 from photosensitive drums 3.The transfer bias (voltage with polarity (+) opposite with the charging polarity (-) of toner) that is used for about several hectovolts of transfer printing toner image is applied to intermediate transfer rollers 6.

Intermediate transfer belt 6 is that 8 to 10mm metal (for example, stainless) axle is as pedestal with diameter.Be coated with conductive elastic component (for example, EPDM, polyurethane foam plastics) in its surface.Conductive elastic component makes and can apply basic voltage uniformly to intermediate transfer belt.In this embodiment, manually transfer roll is used as transfer device.Yet except that this configuration, brush type transfer printing electrode (transfer printing brush) can contact with the back side of intermediate transfer belt 7, to be used as transfer device.

By the rotation of intermediate transfer belt 7, the toner image that is transferred on the intermediate transfer belt 7 moves to the transfer printing portion 11 that is provided with transfer roll 11e.

Intermediate transfer belt 7 pushes each other with predetermined nip width (nip width) with transfer roll 11e and contacts.In addition, the bias voltage (high voltage with polarity (+) opposite with the charging polarity (-) of toner) that is used for toner image is transferred on the paper of hereinafter describing is applied to transfer roll 11e.Among transfer roll 11e and the intermediate transfer belt driven roller 8-1 any one made by hard material (metal etc.), and another is resilient roller, wherein covers soft material (elastic caoutchouc roller, foaminess resin roll etc.) on the surface of core metal.This can provide the extruding of preset width consistently.

By with the contacting of photosensitive drums 3, toner attached in the intermediate transfer belt 7 with transfer images to paper on regional different zones on.In addition, existence is not transferred to the toner that remains on the paper on the intermediate transfer belt 7 by transfer roll 11e.These toners may cause that to make the toner color in subsequent treatment mixed.Therefore, be provided with intermediate transfer belt cleaning unit 9, so that remove and collect the toner on the intermediate transfer belt 7.Intermediate transfer belt cleaning unit 9 is provided with the cleaning balde as cleaning member, and the end of cleaning balde contacts with intermediate transfer belt 7, is used to remove toner.The part of the intermediate transfer belt 7 in intermediate transfer belt cleaning unit 9 and intermediate transfer belt 7 contact portions, by intermediate transfer belt driven roller 8-2 from back support.

On paper feeding tray 10, be stacked with the paper that is used for image formation.Paper feeding tray 10 is arranged on the below of the exposing unit 1 of image forming apparatus 50.On the other hand, discharge tray 15 is arranged on the top of image forming apparatus 50.On discharge tray 15, the paper of printing is discharged from and stacks into printing surface down.

In addition, image forming apparatus 50 setting has paper transport path S, and this paper transport path S has the shape of approximate vertical, and the paper on the paper feeding tray 10 is by paper transport path S, is sent to discharge tray 15 via transfer printing portion 11 and fixation unit 12.Near the paper transport path S between paper feeding tray 10 and the discharge tray 15, be provided with the delivery roll 25 (25-1 to 25-8) of for example picking up roller 16, alignment roller 14, transfer printing portion 11, fixation unit 12 and being used to transmit paper.

A plurality of delivery roll 25-1 to 25-4 are the pony rolls that promotes and support the transmission of paper, and are provided with along paper transport path S.Pick up roller 16 and be arranged on the end of paper feeding tray 10, and transmit paper page by page from paper feeding tray 10 to paper transport path S.

The paper that alignment roller 14 will transmit by paper transport path S temporarily is held in a predetermined position.Alignment roller 14 has the function that paper is sent to transfer printing portion 11 in the synchronous timing of the front end of front end that is formed on the toner image on the intermediate transfer belt 7 and paper.

Fixation unit 12 is provided with for example warm-up mill 31 and pressure roll 32.Warm-up mill 31 and pressure roll 32 rotations are to be clipped in the middle paper.

Warm-up mill 31 is by the control of the control part of control basal plate 40, makes to be arranged on well heater (not shown) in the warm-up mill 31 based on having predetermined fixing temperature from temperature detecting unit (not shown) signal.The paper that 32 pairs of warm-up mill 31 and pressure rolls pass between warm-up mill 31 and the pressure roll 32 applies heat and pressure, makes the toner image that is transferred on the paper be melted, mix and compacting.As a result, the color toner image by hot photographic fixing on paper.

Paper with fixing multi-color toner image is transferred to reverse row's paper path of paper transport path S by delivery roll 25-5 and 25-6.Then, being reversed upward, ventricumbent paper (the multi-color toner image surface down) is discharged to discharge tray 15.

Next, will describe paper transport path in detail.The carton 10 of giving that is used for holding in advance paper is arranged on image forming apparatus.

Paper feeding tray 10 is provided with in its end and picks up roller 16 accordingly, picks up roller 16 paper is fed to paper transport path page by page.

Be sent to alignment roller 14 from the paper of transmitting for carton 10 by the delivery roll 25-1 to 25-4 that is arranged on the paper transport path, and then stop.The timing that alignment roller 14 is joined at the front end of the front end of paper and the toner image on the intermediate transfer belt 7 is sent to transfer printing portion 11 with paper.At transfer printing portion 11 places, the toner image on the intermediate transfer belt 7 is transferred on the paper of transmission.After this, toner image passes fixation unit 12.At this moment, the toner of the not photographic fixing on the paper is melted by heat, is passing fixation unit 12 back natural cooling, and photographic fixing is on paper then.Then, paper is sent to delivery roll 25-5, then is sent to exit roller 25-6, and in the end is discharged to discharge tray 15.

Control basal plate 40 is arranged on the below of discharge tray 15.Control basal plate 40 has microcomputer, ROM and RAM, wherein microcomputer is used to control the operation of each part of image forming apparatus 50, the control program that ROM storage is carried out by microcomputer, and RAM is provided for the perform region of processing of microcomputer and the storage area of view data.Microcomputer executive control program and as control part.Above-mentioned image formation, the transfer printing of toner image, the transmission of paper, the temperature control of fixation unit etc., all the function by control part is implemented.

Control basal plate 40 has input circuit and output circuit.What be input to input circuit is that microcomputer can be carried out processing by the signal that uses input whereby from the signal of the sensor of each the part place setting in the image forming apparatus 50.Output circuit is the circuit that output is used to drive the signal of the load that is arranged on each part place.

As mentioned above, can think that the maximum reason of color misalignment is the off-centre between photosensitive drums 3 and the driven wheel 17.The eccentric caused spacing variance components of each photoreceptor is included in the formed image of each photoreceptor of every kind of color.When mismatch occurring in this spacing change, this mismatch is identified as the color misalignment of image.

Fig. 5 A and 5B are the key diagrams of representing the driving mechanism of photosensitive drums 3 and being used to drive its photoreceptor drive motor 45.Fig. 5 A is the side view from observed photosensitive drums 3 of the direction vertical with the turning axle of photosensitive drums 3 and photoreceptor drive motor 45.At an end of photosensitive drums 3, be provided with the flange of photosensitive drums 3, and driven wheel 47 is wholely set with flange.

Each photosensitive drums 5 is driven by corresponding photosensitive body drive motor 45.The rotation of drive motor 45 is controlled by control part.Driven wheel 46 is mounted on the output shaft of photoreceptor drive motor 45.Driven wheel 46 and driven wheel 47 engagements.

As shown in Fig. 5 A, be provided with accordingly with each photosensitive drums 3 and be used to produce the phase detector 43 of reference signal with the control rotatable phase.Projection 44 is arranged on the side of photosensitive drums 3.Each projection 44 rotates a circle when passing through its test section by photosensitive drums 3, phase detector 43 output reference signals.For example, optical chopper can be used as phase detector.Each reference signal is imported into the input circuit of control basal plate 40.Control part is adjusted the phase place of each photoreceptor by the reference signal of using input, and controls the driving of each photoreceptor drive motor 45.

Fig. 5 B is a key diagram of conceptually representing the eccentric state between photosensitive drums 3 and the driven wheel 47.Fig. 5 B represents to be used to assemble turning axle (axle center) the P1 off-centre of the axle center P2 of driven wheel 47 from photosensitive drums 3, and axle center P3 is present in the state between these axle center.Exist the region S 2 that translational speed related in the rotation (peripheral speed) becomes region S 1 faster and becomes slower on the circumferential surface of photosensitive drums 3.That is, when point that is engaged with each other when driven wheel 46 and driven wheel 47 and the distance between the above-mentioned turning axle, it is slower that peripheral speed becomes.On the contrary, point that is engaged with each other when driven wheel 46 and driven wheel 47 and the distance between the above-mentioned turning axle in short-term, it is faster that peripheral speed becomes.Therefore, peripheral speed is along with the eccentric direction of driven wheel 47, i.e. the rotatable phase of photosensitive drums 3 and change together.

Figure 10 A to 10E is used for explanation in the present embodiment, because the image pitch that the off-centre of photoreceptor causes is with respect to the key diagram of the variation of the benchmark spacing at exposure position and transfer position place.

Shown in Figure 10 A, in the roughly minimum point of photosensitive drums 3 circumferential surface of photosensitive drums 3 is carried out scan exposure by laser beam, form electrostatic latent image whereby.Formed electrostatic latent image is developed by toner.When circumferential surface arrives the transfer position of highest position roughly (being that photosensitive drums 3 is behind rotation half cycle behind the scan exposure at this moment), the toner image of development is transferred on the intermediate transfer belt 7.

Shown in Figure 10 B, when the peripheral speed at exposure position place during faster than datum velocity, the spacing of the electrostatic latent image that forms by exposure is compared with the benchmark spacing and has been increased.Shown in Figure 10 C, when the circumferential surface of exposure arrived transfer position, the rotatable phase of photosensitive drums 3 had increased about 180 degree, makes peripheral speed be lower than datum velocity.Therefore, the spacing that is transferred to the toner image on the intermediate transfer belt 7 is increased to the spacing greater than the toner image before the transfer printing.

On the contrary, when as shown in Figure 10 D, when the peripheral speed at exposure position place was lower than datum velocity, the peripheral speed at transfer position place accelerated, and made that the image pitch of the toner image of transfer printing reduces as shown in Figure 10 E.

In Fig. 5 B,, shown offset with oversize for easy understanding.The actual eccentricity of each photosensitive drums 3 is the small amounts that only can't understand by the rotation status of visually observing photosensitive drums 3.Therefore,, measure its spacing variance components then, and calculate its amplitude and phase place, carry out the control that is used to suppress the color misalignment by preparing to be used for the toner pattern of color alignment.

In addition, the eccentric direction of each photosensitive drums do not know in advance, but find by the measurement of aiming at the toner pattern.Yet,, need set in advance projection 44 in order to control the rotatable phase of each photoreceptor.Control part is by using the rotatable phase of controlling each photosensitive drums 3 from the reference phase of the reference signal of each phase detector 43 and each storage.

(measurement of the explanation 1-misalignment amount of color alignment)

Fig. 3 is the key diagram that calculates the part of the explanation that relates to color alignment according to image forming apparatus shown in Figure 2.As mentioned above, the centre is with 7 by transfer belt driven roller 8-1 driving, to move in the direction of arrow B.In the present embodiment, the diameter of transfer belt driven roller 8-1 is 31.8mm.Y photosensitive drums 3d, M photosensitive drums 3c, C photosensitive drums 3b and K photosensitive drums 3a are along the moving direction setting of intermediate transfer belt 7.Each of Y, M and C photosensitive drums all has the transfer position that contacts with intermediate transfer belt 7.

The diameter of each of Y, M and C photosensitive drums is 30mm, and the diameter of K photosensitive drums 3a is 80mm.Difference between the diameter depends on design conditions, such as serviceable life of photosensitive drums, processing speed (translational speed on the surface of photoreceptor and intermediate transfer belt 7 when image forms) etc.Processing speed when the coloured image that the color misalignment becomes prominent question forms is 173mm/sec.Distance between the transfer printing point of the transfer printing point of Y photosensitive drums 3d and M photosensitive drums 3c, and the distance between the transfer printing point of the transfer printing point of Y photosensitive drums 3d and C photosensitive drums 3b is respectively 100mm.Distance between the transfer printing point of the transfer printing point of C photosensitive drums 3b and K photosensitive drums 3a is 200mm.

The color alignment sensor 41 that is used to measure the color misalignment is arranged on the 280mm place, downstream of the transfer position of K photosensitive drums 3a.Color alignment sensor 41 is color ccd sensors.Yet such sensor is not limited thereto, and can use the catoptrical optical sensor that is used to detect from the surface of intermediate transfer belt 7.The color alignment toner pattern that is transferred on the intermediate transfer belt 7 is read.The signal that is read is imported into the input circuit of control basal plate, and is handled by control part.

(the explanation 2-of color alignment suppresses the misalignment amount by velocity correction)

Fig. 1 is the key diagram that expression is used to proofread and correct the chunk configuration of spacing variance components in the present embodiment.Image forming apparatus is proofreaied and correct the actuating speed of each photoreceptor based on the measurement result of misalignment amount, and suppresses the influence of its off-centre.As shown in Figure 1, each photoreceptor drive motor 45 is by Drive and Control Circuit 53 controls that are provided with in each drive motor 45.Each Drive and Control Circuit 53 is to drive each photoreceptor drive motor 45 with the corresponding actuating speed of the diameter of each photoreceptor.In addition, in order to suppress the change with the corresponding peripheral speed of swing circle of each photoreceptor, be transfused to from the modulation signal of modulation generating circuit 51.Each Drive and Control Circuit 53 is corresponding to the drive control part of appointment in the claim.Each modulation generating circuit 51 is corresponding to the correction signal generating unit of appointment in the claim.In addition, in the configuration of Fig. 1, the correction signal efferent of appointment is made up of the correction signal generating unit in the claims.Each modulation signal is corresponding to the velocity correction signal of appointment in the claim.

In addition, Figure 35 shows such state: each Drive and Control Circuit 53 generates the drive signal that obtains by the drive signal based on modulation signal modulation constant speed, and uses each the photoreceptor drive motor 45 of drive after the modulation.Each photoreceptor drive motor 45 is stepper motors.Drive signal represents to switch with the phase place of stepper motor the waveform of corresponding driving pulse.

Control part 40a is main by realized the chunk of its function by the microcomputer executive control program of being installed on the control basal plate shown in Figure 2 40.Moving of each part of control part 40a control image forming apparatus.For example, control part 40a drives the ON/OFF control signals to Drive and Control Circuit 53 output of each photoreceptor, is used to indicate the startup of photoreceptor/stop.In addition, control part 40a control is by the phase place and the amplitude of the modulation signal of each modulation generating circuit 51 output.Be input to control part 40a from the signal of color alignment sensor 41 with from the signal of the phase detector 43 of each photoreceptor.Based on the information that obtains from these signals, control part 40a obtains the spacing variance components of each photoreceptor and phase place is revolved in the commentaries on classics of each photoreceptor, and the phase place and the amplitude of control modulation signal.

(the explanation 3-of color alignment obtains the phase place and the amplitude of main variance components)

Fig. 4 A to 4C is the key diagram of an example of the expression toner pattern that is used for color alignment in the present embodiment.Fig. 4 A is used to illustrate a kind of toner pattern of color and the key diagram of the notion that this pattern of use is measured.Fig. 4 B be time for reading with color alignment sensor 41 as abscissa axis, expression constitutes the diagrammatic sketch of the misalignment amount of every straight line of toner pattern and reference position.Fig. 4 C represents that two kinds of colors are the pattern of C and Y.Mutual spacing variance components on the toner pattern of every kind of color has the identical cycle, and their phase place is when mating mutually, and the color misalignment is difficult for discovering.That is, when they have identical photoreceptor diameter, can make the color misalignment be difficult for discovering by the rotatable phase of adjusting each photoreceptor.Yet, under the situation of the mutual different color of the diameter of photoreceptor, can not use by adjusting the method that rotatable phase makes the color misalignment be difficult for discovering.

Actual many (among Fig. 4 A being 17) parallel lines that are illustrated as " aiming at the toner pattern " that are formed with on the intermediate transfer belt 7 of Fig. 4 A.Every straight line extends along the direction vertical with the moving direction of intermediate transfer belt 7.Preferably, from the distance of the straight line straight line to the end of the beginning that is in 17 straight lines circumferential length, promptly corresponding to the distance in week of photosensitive drums 3 corresponding to photosensitive drums 3.

When the pattern shown in Fig. 4 A during by the reading of color alignment sensor 41, control part is sampled when reading every straight line.Then, control part is in the misalignment amount of the moment of the straight line that reads every sampling acquisition with reference clock.Reference clock is and the corresponding clock in reference position shown in Fig. 4 A.Reference clock has equal spacing (hereinafter will describe the generation timing of reference clock.) as mentioned above, Fig. 4 B shows abscissa axis and represents that time for reading and axis of ordinates represent the diagrammatic sketch of misalignment amount.

Control part obtains and the corresponding cyclical movement phase place of circumferential length and the amplitude that form the photosensitive drums 3 of toner pattern thereon from being the misalignment amount of every straight line acquisition.

Fig. 4 B is the diagrammatic sketch that axis of ordinates is represented the misalignment amount of every straight line.In Fig. 4 B, positive maximum misalignment amount is d _Max+, and negative maximum misalignment amount is d _Max-Control part never obtains amplitude and the phase place with the corresponding cyclical movement of circumferential length of photosensitive drums 3 in the variation of amount of alignment.The example of acquisition amplitude and phase place is as described below.For the acquisition amplitude, at first obtain the maximal value d of each misalignment amount _Max+With minimum value d _Max-The positive maximum misalignment amount d that is obtained _Max+With negative maximum misalignment amount d _Max-Between difference become range value α.With positive maximum misalignment amount d _Max+With negative maximum misalignment amount d _Max-The centre position be defined as reference phase and obtain phase place.Reference phase be defined in the misalignment amount from negative become positive during, the point of difference vanishing.In Fig. 4 B, the 9th straight line that obtains to count from the beginning of test pattern is as reference phase.

Should notice that in the present embodiment " misalignment amount " is meant the corresponding numerical value of measurement result with every straight line of toner pattern.That is, each misalignment amount is the value of expression from the misalignment of reference position." spacing variance components " is corresponding to the sequential collection of misalignment amount.Although each misalignment amount is a simple numerical value, has periodic variation as the spacing variance components of its sequential collection.Therefore, the spacing variance components has phase place and amplitude.

With the quantitative relationship of explaining between spacing change and the misalignment amount.Shown in Figure 10 A to 10E,, produce the misalignment amount on the positive dirction in Fig. 4 B, as the spacing variance components when the peripheral speed at exposure position place during faster than datum velocity.After this, peripheral speed drops to datum velocity.Yet the misalignment amount that produces on positive dirction does not descend, and is lower than datum velocity unless peripheral speed drops to.Therefore, when peripheral speed dropped to datum velocity, positive misalignment amount still continued.After this, when photoreceptor speed drops to when being lower than datum velocity, produce the misalignment amount of negative direction.Then, the misalignment amount of positive dirction is cancelled.

The waveform of Figure 34 A and 34B there is shown this relation.The phase place of the peripheral speed variance components of photoreceptor is registered as image between exposure period.For being detected, this peripheral speed variance components is the misalignment amount, exist the mistiming of traveling time, such as from the exposure position to the transfer position, arrive the traveling time of color alignment sensor 41 then, promptly corresponding to time of (distance of the 1/2+ of the circumferential length of photoreceptor) ÷ processing speed from transfer position to the color alignment sensor.When adopting the BK photoreceptor as an example, (80 * pi/2+280) ÷ 173=2.34 (second) have been set up.Notice that as shown in Figure 2, this mistiming is different in each photoreceptor.In Figure 34 A and 34B, the figure of spacing variance components is chased after north by the above-mentioned mistiming and is moved, and overlaps on the figure of peripheral speed variance components.The abscissa axis express time " t " of Figure 34 A and 34B.The change of the peripheral speed variance components of each time and the misalignment amount that produced by this peripheral speed variance components is present on the axis of ordinates.

Figure 34 A represents that photoreceptor speed writes the increase zero hour from image, and situation about after this reducing.Figure 34 B represents that photoreceptor speed writes from image and reduces the zero hour, and in situation about after this increasing.

By every kind of color is carried out above-mentioned measurement, control part obtains the amplitude and the phase place of the spacing variance components of each photosensitive drums 3 when forming the toner pattern of every kind of color.

Figure 36 A and 36B are that the above-mentioned range value α of expression (it is when when being used to proofread and correct drive signal that modulation signal that circumference changes modulates and driving, the amplitude composition in the peripheral speed of photoreceptor) compares A with the speed amplitude _v(it is and datum velocity V ₀Ratio) the oscillogram of relation.Figure 36 A and 36B are corresponding to Figure 34 A.Range value α compares A with amplitude _vBetween relation as mentioned below.

About the time, comprise that the peripheral speed (mm/sec) of the photosensitive drums of circumference change is expressed as follows:

(formula 1)

v＝V ₀+(A _v·V ₀)sinωt

V ₀: datum velocity (processing speed) is (mm/sec)

A _v: the speed amplitude is than (amplitude and the V of peripheral speed change ₀Ratio)

ω: the angular velocity of photosensitive drums (rad/sec)

T: time (sec)

At this moment, as the half period of peripheral speed change, formula is set up as follows:

(formula 2)

${\&Integral;}_0^{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="C20071009637600541.png"\; state="\{\{state\}\}">t</figure-callout>}1}\mathrm{vdt}-{\mathrm{<figure-callout\; id="0"\; label="v"\; filenames="C20071009637600711.png,C20071009637600771.png"\; state="\{\{state\}\}">v</figure-callout>}}_0\&CenterDot;{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="C20071009637600541.png"\; state="\{\{state\}\}">t</figure-callout>}}_1=\mathrm{\&alpha;}$

T1: photosensitive drums is carried out time π/ω (sec) that the half cycle rotation needs

α is defined as 1/2, the reasons are as follows.Shown in Figure 10 A to 10E, in the process that laser writes, produce the spacing change, and in will aiming at the process of toner pattern transfer on the transfer belt, produce spacing once more and change by the change of the peripheral speed of photoreceptor.This is because spacing change is corrected, and is range value α because the color alignment sensor detects the twice of the value of actual pitch change.Figure 37 is furnished with the waveform of part of oblique line and the key diagram of the relation between the above-mentioned formula among schematically illustrated Figure 36 B.

(formula 3)

${\&Integral;}_0^{t1}{V}_0(1+A_v\&CenterDot;\sin \mathrm{\&omega;t})\mathrm{dt}-{\mathrm{<figure-callout\; id="0"\; label="V"\; filenames="C20071009637600711.png,C20071009637600771.png"\; state="\{\{state\}\}">V</figure-callout>}}_0\&CenterDot;{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="C20071009637600541.png"\; state="\{\{state\}\}">T</figure-callout>}}_1=\mathrm{\&alpha;}/2$

That is, work as A _vWhen following formula obtains, set up

(formula 4)

A _v＝ω·α/4V ₀

For example, as the diameter D of photosensitive drums _pBe arranged to 30 (mm), and processing speed V ₀When being arranged to 173 (mm/sec), the angular velocity omega of photosensitive drums is expressed as follows:

(formula 5)

ω＝2π/π·D _p/V ₀＝2V ₀/D _p＝3.7π(rad/sec)

When the range value α of the misalignment amount that obtains is expressed as α=2 (point)=84 (μ m), set up

A _v＝0.0014＝0.14(％)

Fig. 6 is and the corresponding key diagram of Fig. 3, and expression color alignment toner pattern corresponds respectively to every kind of color and is formed on the photoreceptor, and aims at the state that the spacing of toner pattern is measured by color alignment sensor 41.Shown in Fig. 4 A to 4C, each aims at the toner pattern by 17 rectilinear(-al)s.

(rotatable phase of photosensitive drums is adjusted in the explanation 4 one of color alignment)

As mentioned above, have at photoreceptor under the situation of same diameter, even eccentric absolute value does not change, the phase place of spacing variance components that also can be by every kind on matching image color makes the color misalignment be difficult for discovering.Fig. 4 C shows this notion.Toner pattern C (C pattern) and toner pattern Y (Y pattern) are equal to each other with respect to the misalignment amount of reference position.Yet, if their phase matching can reduce the relative misalignment amount between every kind of color.From experience as can be known, compare with the absolute variation of pel spacing, human eye is responsive more to the misalignment between every kind of color.Therefore, have the color of same diameter,, the color misalignment is become be difficult for discovering by adjusting the rotatable phase of each photosensitive drums for photosensitive drums 3.

Here must be noted that overlappedly to be formed on the position at the some place of every kind of color on each photoreceptor to have different angles with respect to the reference phase of each photoreceptor as output image.This is because the required traveling time of processing of each photoreceptor such as from the exposure position to the transfer position, then to the time of color alignment sensor, is different.Have only when the interval of each transfer position equals the integral multiple of circumferential length of photosensitive drums, the point of every kind of color just is formed on such position, and its reference phase for every kind of color has the angle of coupling.Therefore, in measured and this image during the phase matching of included spacing variance components, the rotatable phase of each photoreceptor not necessarily mates when alignment image.Yet, in the present embodiment, use shared modulation signal for each photoreceptor Y, M and C.Therefore, carry out correction to mate the rotatable phase of each photoreceptor.

Before the adjustment of explanation rotatable phase, at first, the benchmark anglec of rotation will be described.Fig. 8 is illustrated in the key diagram that is formed with the state of aiming at the toner pattern on the photosensitive drums 3.In photosensitive drums 3, form electrostatic latent image with the position that photoreceptor is exposed in laser beam L scanning.Here suppose that in Fig. 8 photosensitive drums 3 is the reference phase that obtains by the measurement of carrying out later in this position that is exposed constantly.In this case, the angle that is produced by projection 44 and phase detector 43 is called as " the benchmark anglec of rotation ".The anglec of rotation of photosensitive drums 3 is the angles after projection 44 is passed phase detector 43.The benchmark anglec of rotation corresponding to from just before phase detector 43 output reference signals the time be carved into the anglec of rotation in the moment that the toner pattern as reference phase is exposed.

Fig. 9 A and 9B are used to illustrate the benchmark anglec of rotation that is associated with Fig. 8 and the key diagram of the relation between the reference phase.In Fig. 9, laterally represent elapsed time.The Laser emission signal is to be used for driving laser irradiation portion so that emission is used for writing the signal of the laser beam L that aims at the toner pattern on photoreceptor.The said reference clock from the generation of each Laser emission signal constantly, to through being generated after (from the exposure position to the transfer position, then to the color alignment sensor) traveling time.Shown in Fig. 9 A, at time t1, projection 44 is passed phase detector 43, and the output reference signal.After this, at time t2, be exposed, and form the electrostatic latent image of aiming at the toner pattern in this position as the position of reference phase.Time from time t1 to time t2 is defined by Δ t.Be developed along with the rotation of photosensitive drums 3 with the pattern of the corresponding part of reference phase, and arrive transfer position after this.The toner pattern is transferred on the intermediate transfer belt 7 in transfer position.The toner image of transfer printing is read by color alignment sensor 41 at time t3.As mentioned above, control part obtains reference phase from the misalignment amount of the toner pattern that read.As a result, by the color alignment sensor the pattern that time t3 reads be set at the corresponding position of reference phase on.The following acquisition of Δ t.Δ t=(time of t1 to t3)-(from the exposure position to the transfer position) then to the traveling time of color alignment sensor.

As mentioned above, have phase differential between the phase place of the phase place of spacing variance components and peripheral speed variance components, it is corresponding to 90 ° the photoreceptor anglec of rotation.Therefore, as shown in Fig. 9 B, when having prepared synchronizing signal, the correction of Δ t is added in the reference signal, and (sec) is deducted with rotational time corresponding correction time of the dt (90 °) of 90 ° of the anglecs of rotation of photoreceptor.Alternatively, add with rotational time corresponding correction time of the dt (90 °) of 270 ° of the anglecs of rotation of photoreceptor (sec).Here, the following calculating of dt (x).

dt(x)＝R×π÷V ₀×x÷360(°)

R: photoreceptor diameter

V0: photoreceptor peripheral speed

As mentioned above, control part is determined the benchmark anglec of rotation of each photosensitive drums based on the reference phase of measured toner pattern.

In addition, control part is adjusted the rotatable phase of photosensitive drums Y, M and C, thereby mates mutual reference phase according to the misalignment amount of the reference phase of measured toner pattern.

Then, for example, necessary is to begin exposure, makes based on by reading view data that original copy generates or when being formed by the image that the view data that outer computer generates prints image, the leading section of print image is exposed at the benchmark anglec of rotation place of each photosensitive drums.Alternatively, the leading section of image can be postponed predetermined angular and exposes from reference phase.Retardation is identical to Y, M and C.Like this, because the phase matching of each image of Y, M and C, so the color misalignment is difficult for discovering.

For example, be moved to end and each photosensitive drums when being stopped in the formation of toner pattern, control part is carried out the adjustment of the rotatable phase of each photosensitive drums.In the time that stops, controlling the rotation of each photoreceptor drive motor 45, make the anglec of rotation of each photosensitive drums 3 when stopping to have predetermined relation.That is, the anglec of rotation of photoreceptor when stopping to be controlled so as to, and makes the synchronizing signal of Y, M and C have predetermined phase relation, as shown in figure 11.

Figure 11 represents that in the present embodiment the key diagram of the peripheral speed variance components under following state: the rotatable phase of each photoreceptor is adjusted, so that the phase place of the spacing variance components on the matching image.Black round indication among Figure 11 should be transferred to each position of Y, the M of the same position on the recording medium and C image.In this case, the reference phase of each of Y, M and C photosensitive drums 3 departs from.Distance is 100mm between the transfer position of the transfer position of Y photosensitive drums 3d and M photosensitive drums 3c.On the other hand, the circumferential length of photoreceptor 3 is 92.25mm.Therefore, departing from aspect distance of occurring between them is 5.75mm, and is being 21.96 ° aspect the anglec of rotation of photoreceptor.This sets up too to the relation between M photosensitive drums 3c and the C photosensitive drums 3b, and departing from aspect distance that wherein they occur between the two is 5.75mm, is being 21.96 ° aspect the anglec of rotation of photoreceptor.

Therefore, in adjusted state, the rotatable phase of M photosensitive drums 3c postpones 21.96 ° from the rotatable phase of Y photosensitive drums 3d.Similarly, the rotatable phase of C photosensitive drums 3b postpones 21.96 ° from the rotatable phase of M photosensitive drums 3c.Particularly, the rotatable phase of C photosensitive drums 3b postpones 43.92 ° from the rotatable phase of Y photosensitive drums 3d.

If the distance between each transfer position is consistent with the circumferential length of photoreceptor, then the rotatable phase of each photoreceptor matches each other.Yet this has applied restriction to the arrangement space around each photoreceptor or the size of image forming apparatus.

In view of this, any one of Y, M and C is defined as benchmark and controls the phase place of color modulation signal.In the embodiment shown in fig. 11, Y is defined as benchmark.In this case, based in the Y synchronizing signal of behind the Δ t of Y phase detector 43d output reference signal, exporting, control the phase place of (color) modulation signal.Under the situation of Figure 11, the phase place of the modulation signal of control color makes that the reference phase and the Y synchronizing signal of (color) modulation signal are synchronous.Particularly, the phase place of modulation signal is controlled so as to, and makes when the Y synchronizing signal is output, and exports on negative direction from zero (color) modulation signal that increases.

Figure 12 is illustrated under the controlled state of rotatable phase of each photoreceptor the example of the position of each projection 44 in the present embodiment.Owing between the direction of each projection of photoreceptor and eccentric direction, do not have correlativity, so the direction of the projection 44 of each photoreceptor is at random.Figure 12 is used to show the corresponding relation with the Figure 15 that hereinafter describes.

Under each the controlled state of rotatable phase in Y, M and C photosensitive drums 3, when being imported into each Drive and Control Circuit 51b, 51c and 51d, between the phase place of the peripheral speed variance components of photoreceptor and modulation signal, having produced and departed from from the modulation signal of modulation generating circuit 51b.

For example, suppose the amplitude maximum of the peripheral speed variance components of C photosensitive drums 3b, and modulation generating circuit 51b generates the modulation signal that has with its opposite phases.In this case, adjust signal and also be imported into Y and M Drive and Control Circuit 51d and 51c from modulation generating circuit 51b.For C photosensitive drums 3b, phase place is corrected, and makes that the peripheral speed variance components is suppressed well, yet for Y and M photosensitive drums 3d and 3c, the phase place of modulation signal has taken place to depart from respect to the peripheral speed variance components.

Therefore, control part is proofreaied and correct the rotatable phase of each photoreceptor from the controlled state of rotatable phase of each Y, M and C photosensitive drums 3, so that the phase place of the spacing variance components on the image is matched each other.This makes the rotatable phase can adjust each Y, M and C photoreceptor, and the phase matching that can make the peripheral speed variance components is in the common modulation signal.Particularly, the rotatable phase of M photosensitive drums 3c shifts to an earlier date 21.96 ° on its sense of rotation.In addition, the rotatable phase of C photosensitive drums 3b shifts to an earlier date 43.92 ° on its sense of rotation.Particularly, the rotatable phase of the photoreceptor that control is stopped is so that make M and C synchronizing signal and Y synchronizing signal coupling under the situation of Y synchronizing signal as benchmark.

Adjustment amount is the value that obtains in advance the difference between the circumferential length of transfer position and each photoreceptor.

Aim at the adjustment that the toner pattern obtains this rotatable phase by measuring.In other words, the rotatable phase of each photoreceptor in advance and do not know.Yet the state that the phase place of the spacing variance components from the image is mated can be known the adjustment amount (predetermined misalignment amount) of the phase place of the cyclical velocity change that is used to mate each photosensitive drums in advance.Control part is also adjusted the rotatable phase of each photosensitive drums 3 after the phase place of the spacing variance components on the matching image by the measurement of toner pattern.Therefore, obtain the adjustment amount of the rotatable phase of each photosensitive drums 3 by two stages.

It should be noted that can be in the stage that obtains final adjustment amount, once carries out the processing that the rotatable phase generation physics that is used to make each photosensitive drums departs from.Alternatively,, the rotatable phase of each photoreceptor can be adjusted to, make the misalignment amount that is obtained move to above-mentioned predetermined misalignment amount by measuring the toner pattern and calculating the relative misalignment amount of the rotatable phase of each photoreceptor.

Figure 13 is the key diagram of the state of the peripheral speed variance components under the state that matches each other of rotatable phase of each photosensitive drums 3 of expression.Adopt this state, modulation generating circuit 51b generate have with Y, M and C photosensitive drums 3d, 3c and 3b in each the modulation signal of phase place opposite phases.Among Y, M and C Drive and Control Circuit 53d, 53c and the 53b each adopts this modulation signal to proofread and correct actuating speed.Therefore, the peripheral speed variance components of each photoreceptor has obtained correction.

Black circle indication Y, M among Figure 13 and each in the C image should be transferred to the position of the same position on the recording medium.Suppose the leading section of the image that black round position is defined as printing, the position of the leading section of the image of the printing of Y, M and C and the coupling of the synchronizing signal among Figure 11.On the other hand, under the state after rotatable phase is adjusted, the position of the leading section of Y print image and Y synchronizing signal coupling, but the position of the leading section of M print image is from 21.96 ° of M sync signal delay, and the leading section of C print image is from 43.92 ° of C sync signal delay, as shown in figure 13.Control part is controlled the phototiming when the leading section of each print image of the previous synchronizing signal of preamble shown in 13.

Here, the amplitude of each modulation signal is adjustable.As the amplitude of color modulation signal, the amplitude of the spacing variance components of every kind of color photosensitive drums is detected, and selects amplitude peak and minimum radius from the amplitude that the spacing variance components according to each photosensitive drums of Y, M and C calculates.Then, based on the intermediate value of amplitude peak and minimum radius, determine the amplitude of (color) modulation signal.

Figure 14 is that each Drive and Control Circuit 53 of expression is eliminated the key diagram of the state of peripheral speed variance components by using modulation signal.Suppose the velocity variations amplitude of the C photoreceptor of rotational speed variable quantity maximum is defined as Ac, the velocity variations amplitude of the M photoreceptor of rotational speed variable quantity minimum is defined as Am.In this case, control part adopts the intermediate value of Ac and Am, and promptly (Ac+Am)/2 are as the amplitude of modulation signal.The reasons are as follows.If the amplitude of (color) modulation signal is specified to the spacing variance components of the photosensitive drums of eliminating the amplitude maximum fully, then correcting value is too big for the photosensitive drums of amplitude minimum.When from the spacing variance components of each photoreceptor of Y, M and C, taking out the average amplitude of amplitude peak and minimum radius, can be that every kind of color of Y, M and C obtains suitable correcting value.

Yet,, can come the application of modulation signal by getting rid of this color when the spacing variance components of any color is little during to the degree that need not to proofread and correct.In this case, as will be described later shown in Figure 22, can construct like this, promptly, image forming apparatus has switching part 57 and switches the control part 40a of the state of switching part 57, is input to Drive and Control Circuit so that prevent the modulation signal beyond the calibration object.For example, when the spacing variance components of Y is little during to the degree that do not need to proofread and correct, the switch of switching part Y57d is configured to OFF.Switching part C57b and switching part M57d are configured to ON.The amplitude of modulation signal that is applied to every kind of color of M and C is configured to be employed the amplitude peak of every kind of color of modulation signal and the mean value of minimum radius, and in this example, it can be arranged to the average amplitude of the spacing variance components of M and C.Switching part 57 is corresponding to the switching part of appointment in the claim.In the configuration of Figure 22, the correction signal efferent of appointment in the claim is made up of modulation generating circuit 51 and switching part 57.

Figure 28 to 31 is key diagrams of expression advantage of the method for eliminating fine pitch variance components from calibration object.Figure 28 is illustrated in before the correction, i.e. the example of the spacing variance components of the photosensitive drums of every kind of color of the Y when not having the application of modulation signal, M and C.The amplitude of spacing variance components is that unit is presented on the longitudinal axis with pixel (point).Notice that a pixel (1 point) is 42 μ m.Time is present on the abscissa axis.The cycle of spacing variance components is corresponding to the swing circle of photosensitive drums.In example shown in Figure 28, the amplitude of the spacing of Y change is two pixels.In addition, the amplitude of M is six pixels, and the amplitude of C is four pixels.

Figure 29 A is illustrated in by the spacing variance components of Figure 28 being used the spacing variance components after Y, M and C common modulation signal are proofreaied and correct and being used for the modulation signal of whole colors.The applied correcting value A of Figure 29 A calculates according to the minimum radius of Y, M and C and the mean value of amplitude peak.Minimum radius is two pixels of Y, and amplitude peak is six pixels of M.Therefore, the mean value that calculates is four pixels.The result who correcting value A is applied to every kind of color Y, M and C is shown as the waveform of " proofreading and correct the back ".Y demonstrates exaggerated correction, and amplitude is two pixels.The amplitude of M is two pixels.C is 0 pixel.The breadth extreme of the relative color misalignment among Y, M and the C is two mutual anti-phase pixels of Y and M.

Figure 29 B represent the modulation signal when from calibration object, getting rid of the fine pitch variance components and proofread and correct after the spacing variance components.Be used for determine getting rid of the threshold value of the spacing variance components of object, can suitably set based on the image of reality output by the deviser.In this example, threshold value is converted into pel spacing, and two pixels are taken as threshold value.Therefore, the Y that the spacing composition is equaled two pixels gets rid of from calibration object.Applied correcting value B is calculated as the mean value of M and C, and its result is five pixels.The modulation signal that is calculated is applied to M and C, and is not applied to Y.The result who obtains is shown as the waveform of " proofreading and correct the back ".The amplitude of Y is and proofreaies and correct preceding two identical pixels.The amplitude of M is a pixel.C becomes exaggerated correction, and its amplitude is a pixel.The breadth extreme of the relative color misalignment among Y, M and the C is 1.5 mutual anti-phase pixels of Y and C.When comparing with Figure 29 A, the spacing variance components has reduced by 0.5 pixel.By from calibration object, getting rid of the fine pitch variance components, can obtain better result.

Figure 30 represents the example of spacing variance components of photosensitive drums of every kind of color of the Y different with Figure 28, M and C.In example shown in Figure 30, the amplitude of Y is 0 pixel (0.5 pixel is following), and the amplitude of M is six pixels, and the amplitude of C is four pixels.Figure 31 A represent Y, M that the spacing variance components of Figure 30 is used and C common modulation signal and proofread and correct by the modulation signal that use is used for whole colors after spacing modulation composition.The applied correcting value C of Figure 31 A calculates according to the minimum radius of Y, M and C and the mean value of amplitude peak.Minimum radius is 0 pixel of Y, and amplitude peak is six pixels of M.Therefore, the mean value that calculates is three pixels.The result who correcting value A is applied to every kind of color of Y, M and C, illustrate with the waveform of " proofread and correct back ".Y is an exaggerated correction, and its amplitude is three pixels.The amplitude of M is three pixels.The amplitude of C is a pixel.The breadth extreme of the relative color misalignment among Y, M and the C is two mutual anti-phase pixels of Y and M.

Figure 31 B represent when from calibration object, get rid of the spacing variance components be two pixels or the modulation signal during less than two color of pixel and proofread and correct after the spacing variance components.In this example, from calibration object, get rid of Y.Applied correcting value D is calculated as the mean value of M and C, and the result is five pixels.The modulation signal that calculates is applied to M and C, and is not applied to Y, and the result who is obtained is shown in the waveform of " proofreading and correct the back ".The amplitude of Y is and proofreaies and correct preceding 0 identical pixel.The amplitude of M is a pixel.C becomes exaggerated correction, and its amplitude is a pixel.The breadth extreme of the relative color misalignment among Y, M and the C is the mutual anti-phase pixel of M and C.When comparing with Figure 29 A, the spacing variance components has reduced by two pixels.By from calibration object, getting rid of the fine pitch variance components, can obtain better result.

Figure 15 is corresponding to Figure 12, and is the key diagram of example of the position of each projection 44 under the state of the expression rotatable phase that is in each photoreceptor of coupling.

Figure 26 and Figure 27 are the process flow diagrams of the spacing variance components of the control part 40a photosensitive drums of measuring every kind of color, and show the process that the amplitude and the phase place of modulation signal is provided with based on measurement result.To describe this process in conjunction with process flow diagram.

At first, as shown in Figure 26, control part 40a measures the phase place and the amplitude (step S11) of the spacing variance components of Y photoreceptor 3d.There is shown the detailed process of measurement in the flow process of Figure 27.Here, go on to say Figure 26.Then, control part 40a measures the phase place and the amplitude (step S13) of the spacing variance components of M photoreceptor 3c.In addition, control part 40a measures the phase place and the amplitude (step S15) of the spacing variance components of C photoreceptor 3b.

After this, control part 40a obtains amplitude peak and minimum radius (step S17) from the spacing variance components of every kind of color of Y, M and C.This is handled corresponding to Figure 14.That is, control part 40a is defined as the intermediate value (Ac+Am)/2 of maximal rate amplitude of variation Ac and minimum speed amplitude of variation Am the amplitude of modulation signal.Then, its mean value is set to be used for the amplitude of the modulation signal of color signal.In addition, be set to be used for the phase place (step S19) of the modulation signal of color signal with the phase place opposite phases of the cyclical velocity of predefined benchmark color Y change.

In addition, control part 40a obtains the phase place and the amplitude (step S21) of the spacing variance components of K.Then, control part 40a is provided for the phase place and the amplitude of the modulation signal of K, so that eliminate the spacing variance components (step S21) of the K that is obtained.Here, the processing of the K shown in step S19 and S21 is not to carry out after the processing of every kind of color of the Y shown in the step S11 to S19, M and C.The processing of K can be carried out before the processing of every kind of color of Y, M and C.

Figure 27 is the process flow diagram of the process of the phase place of the expression spacing variance components that obtains designated color and amplitude.This routine can be cited in above-mentioned steps S11, S13, S15 and S39.As shown in figure 27, the operation of each part of control part 40a control image forming apparatus is so that form 17 bar chart cases (step S51) shown in Fig. 4 A to Fig. 4 C on the photosensitive drums of designated color.Then, color alignment sensor 41 sequentially detects the position (step S53) of the formed pattern that is used to adjust.In addition, control part 40a compares the position and the reference position of each detected pattern, and calculates misalignment amount (step S55).Carry out the calculating (step S57) of the misalignment amount of whole line patterns.After this, control part 40a calculates (step S59) to the phase place and the amplitude of the misalignment amount that calculates.

Figure 32 is the process flow diagram of the expression process different with Figure 26.In Figure 26, be Y with the benchmark definitions of color in advance.Yet, in the process flow diagram of Figure 32, select any of Y, M and C color as the benchmark color according to the measurement result of spacing variance components.In Figure 32, identical symbol and digital distribution are given and the corresponding processing of Figure 26.That is, the processing of step S11 to S17, S21 and S23 is corresponding to the processing of same-sign and the numeral of Figure 26.The processing of step S31 and S33 is different with the processing of Figure 26.Therefore, each step of the processing different with Figure 26 will be explained.At step S31, control part 40a is defined as the benchmark color with the color of the amplitude maximum of spacing variance components, and will be defined as being used for the phase place (step S33) of the modulation signal of color signal with the phase place opposite phases of the cyclical velocity of determined benchmark color change.

Figure 33 is the process flow diagram of the expression other process different with the processing of Figure 26.In the process flow diagram of Figure 33, carry out to handle so that from calibration object, get rid of and have predetermined amplitude or less than the color of the spacing variance components of the amplitude of predetermined amplitude.In Figure 33, identical symbol and digital distribution are given and the corresponding processing of Figure 26.The processing of step S41 to S57 is different with the processing of Figure 26.Each step of the processing that explanation is different with Figure 26.

Control part 40a determines whether the amplitude of measurement result of the spacing variance components of Y equals threshold value or less than threshold value (step S41).As the result who determines, when amplitude surpasses threshold value, the Y switching part is arranged to ON (step S43), and when amplitude is equal to or less than threshold value, the Y switching part is arranged to OFF (step S45).Subsequently, control part 40a determines whether the amplitude of the spacing variance components of M is equal to or less than threshold value (step S47).When amplitude surpasses threshold value, the M switching part is arranged to ON (step S49), and when amplitude is equal to or less than threshold value, the M switching part is arranged to OFF (step S51).In addition, control part 40a determines whether the amplitude of the spacing variance components of C is equal to or less than threshold value (step S53).When amplitude surpasses threshold value, the C switching part is arranged to ON (step S55), and when amplitude is equal to or less than threshold value, the C switching part is arranged to OFF (step S57).

Should notice that in said process the order of the processing of Y, M and C not necessarily will be as shown in process flow diagram, and is interchangeable.In addition, for every kind of color, can after Measurement Phase and amplitude, carry out determining of threshold value at once.

(adjustment of the rotatable phase of photosensitive drums)

The technology of the rotatable phase be used to adjust each photosensitive drums will be explained in detail.

As mentioned above,, make the eccentric direction of each photosensitive drums 3 after stopping to become the control of predetermined direction, adjust rotatable phase by being used for realization when control part 40a stops each photosensitive drums 3.Control part 40a obtains the spacing variance components that the off-centre by each photosensitive drums 3 causes by measure aiming at the toner pattern, and when expose by laser beam L in the position of the reference phase of the spacing variance components that is obtained, exports synchronizing signal.As shown in figure 13, under the controlled state of rotatable phase of each Y, M and C photoreceptor, the output of each of Y, M and C synchronizing signal is regularly mated mutually.Hereinafter, this state is called as the state of the rotatable phase coupling of photosensitive drums.

Figure 25 is the key diagram that is expressed as follows state: the stop position of M photosensitive drums 3c and C photosensitive drums 3b is adjusted, and to stop M photosensitive drums 3c and C photosensitive drums 3b, makes their rotatable phase and the rotatable phase of Y photosensitive drums 3d mate.In Figure 25, the output of M synchronizing signal is in advance in the Y synchronizing signal as benchmark, and the output delay of C synchronizing signal is in the Y synchronizing signal.Control part 40a monitors M and C synchronizing signal shifting to an earlier date and delay with respect to the Y synchronizing signal before stopping.Particularly, control part 40a obtains the lead M Δ dr of M synchronizing signal and the retardation C Δ dr of C synchronizing signal.

After this, control part 40a will stop at the precalculated position as the Y photosensitive drums 3d of benchmark.At Figure 25, control part 40a adopts as the Y synchronizing signal that triggers and stops Y photosensitive drums 3d.In advance in M photosensitive drums 3c, than stopping at the Zao M Δ of the M synchronizing signal dr of output afterwards as the Y synchronizing signal of the benchmark that is used to stop.That is,, export next synchronizing signal rotating a circle the required time after (photoreceptor circumferential length ÷ peripheral speed) through photoreceptor from detecting synchronizing signal.Therefore, can { (photoreceptor rotates a circle the required time)-M Δ dr} stops photoreceptor after detecting synchronizing signal.Like this, proofreaied and correct with respect to the phase place of Y photosensitive drums 3d in advance.On the other hand, C photosensitive drums 3b is stopped than C sync signal delay C Δ dr, and the Y sync signal delay C Δ dr that this C synchronizing signal likens to the benchmark that is used to stop to be output.Like this, proofreaied and correct delay with respect to the phase place of Y photosensitive drums 3d.

When the output of M synchronizing signal during with respect to the Y sync signal delay, M photosensitive drums 3c can be stopped from the retardation of M sync signal delay M Δ dr, and this M sync signal delay is in being output as the Y synchronizing signal of the benchmark that is used to stop.Figure 24 is illustrated in the M synchronizing signal in advance or postpone under the situation of reference signal tref (corresponding to the Y synchronizing signal among Figure 25), and control part 40a adjusts the key diagram of the state of rotatable phase.Can carry out and the identical adjustment of M synchronizing signal shown in Figure 24 the C synchronizing signal.

Preferably, when being stopped, each each photosensitive drums 3 carries out the adjustment of rotatable phase.May exist such situation, that is, print in the process of many pages or leaves continuously, the rotatable phase of each photoreceptor by mistake departs from gradually.This is considered to because the slight error of the diameter of each photosensitive drums, or the disturbing factor of driving control system causes.Can keep inhibition effect by matching rotation phase place when photosensitive drums 3 is stopped to the color misalignment.

(being used to adjust the different bearing calibration of color misalignment)

Figure 16 is the key diagram that expression is used to proofread and correct the different chunk configuration of spacing variance components in the present embodiment.In image forming apparatus shown in Figure 16, in the processing before the modulation signal from modulation generating circuit 51b is imported into M Drive and Control Circuit 53c, M delay circuit 55c is set.In addition, in the processing before the modulation signal from modulation generating circuit 51b is imported into C Drive and Control Circuit 53b, C delay circuit 55b is set.Delay circuit 55 is corresponding to the retardation adjustment part of appointment in the claim.For example, each delay circuit can be realized by using the FIFO memory component.In the configuration of Figure 16, the correction signal efferent of appointment in the claim is made up of modulation generating circuit 51 and delay circuit 55.

Each delay circuit 55 is with the modulation signal delay scheduled time.Like this, the modulation signal with out of phase is imported into each Y, M and C Drive and Control Circuit 53d, 53c and 53b respectively.

Figure 17 is corresponding to Figure 13, and is the key diagram of state of the peripheral speed variance components of each photosensitive drums 3 among the embodiment of expression Figure 16.

In the image forming apparatus of Figure 16, control part is adjusted the rotatable phase of each Y, M and C photoreceptor 3, so that the phase place of the spacing variance components that comprises in each image is mated.Yet, different with the image forming apparatus of Fig. 1, do not carry out the further rotatable phase adjustment of the rotatable phase that is used to mate each photoreceptor.On the contrary, the anti-phase modulation signal of peripheral speed variance components of each delay circuit 55 output and each photosensitive drums 3.At first, modulation generating circuit 51b generates and the anti-phase modulation signal of peripheral speed variance components as the Y photosensitive drums 3d of benchmark.The modulation signal that is generated is directly inputted to Y Drive and Control Circuit 53d, and is imported into M delay circuit 55c and C delay circuit 55b.

M delay circuit 55c postpones 21.96 ° of corresponding times of the anglec of rotation with M photosensitive drums 3c with the modulation signal imported, and is entered into M Drive and Control Circuit 53c.Like this, be imported into M Drive and Control Circuit 53c with the anti-phase modulation signal of the peripheral speed variance components of M photosensitive drums 3c.

C delay circuit 55b postpones 43.92 ° of corresponding times of the anglec of rotation with C photosensitive drums 3b with the modulation signal imported, and is entered into C Drive and Control Circuit 53b.Therefore, be imported into C Drive and Control Circuit 53b with the anti-phase modulation signal of the peripheral speed variance components of C photosensitive drums 3b.

In addition, Figure 22 is the key diagram that expression is used to proofread and correct the other different chunk configuration of spacing variance components.In image forming apparatus shown in Figure 22, switching part 57b, 57c and 57b are separately positioned on the modulation signal from the modulation generating circuit 51b of color output are input to during Drive and Control Circuit 53b, 53c and the 53d each handle.Switching part 57b, 57c and 57b serve as the modulation signal that is used for to whether modulation generating circuit 51b being generated and are input to the switch that each Drive and Control Circuit 53b, 53c and 53d switch.

Control part 40a switches the ON/OFF of each switch.Switching part 57b, 57c and 57b are the switching parts of appointment in the claim, and control part 40a comprises the function as the switch control portion of appointment in the claim.When the spacing of each photoreceptor Y, M and C modulation composition during less than predefined amplitude, control part 40 is arranged to OFF with switch.If switch is configured to OFF like this, then can prevent such situation, that is, although the spacing variance components is fully little, the driving of drum is by the modulation signal exaggerated correction from modulation generating circuit 51b.

Figure 23 is the key diagram that expression is used to proofread and correct the other different chunk configuration of spacing variance components.The image forming apparatus of Figure 23 is such image forming apparatus: above-mentioned switching part 57 is applied in the configuration of Figure 16, and has increased the amplitude adjusting circuit that is used to adjust from the amplitude of the modulation signal of each delay circuit 55 outputs.

The amplitude adjusting circuit 59b of Figure 23 and 59c come the amplitude of modulation signal is adjusted by the instruction from control part 40a.Amplitude adjusting circuit 59 can for example be realized by multiplier.Control part 40a is provided with the modulation signal that is generated by modulation generating circuit 51b, to suppress the spacing change of Y, and, change with the spacing that suppresses every kind of color by the amplitude adjusting circuit 59b of C and the amplitude of adjusting modulation signal respectively by the amplitude adjusting circuit 59c of M.Therefore, amplitude and phase place according to the spacing variance components of every kind of color are imported in each Drive and Control Circuit 53.Amplitude adjusting circuit 59 is corresponding to the amplitude adjustment part of appointment in the claim.In the configuration of Figure 23, the correction signal efferent of appointment in the claim is made up of modulation generating circuit 51, amplitude adjusting circuit 59, delay circuit 55 and switching part 57.

Can realize similar function by in Y, M and C, having independently modulation generating circuit respectively.Yet, in M in Figure 23 and the delay circuit of C 55 and the amplitude adjusting circuit 59, only can fine be adjusted into the phase place and the amplitude of the modulation signal of Y setting.Consider cost that circuit is required etc., the deviser can select any in the above-mentioned configuration.

(manually color alignment method)

Can have the function that print registration toner pattern is also visually adjusted the variance components of image pitch according to image forming apparatus of the present invention.For example, when color alignment sensor 41 breaks down, and by being read by color alignment sensor 41 when aiming at adjustment result that the toner pattern carries out and having demonstrated fault, manual adjustment is effective.In this case, for example, service engineering teacher has the autodiagnosis program of the rotatable phase that is used for visually adjusting photoreceptor.The autodiagnosis program provides by the functional unit (not shown) that uses image forming apparatus 50 and has imported adjusted value, and the function of adjusting the rotatable phase of each photoreceptor.

Figure 18 is the key diagram that is expressed as the print example of the aligning toner pattern that the vision adjustment provides.In Figure 18, be the equally spaced pattern that the photosensitive drums 3a by K forms as the pattern of reference position.Here, in K photosensitive drums 3a, actuating speed is corrected by suitable modulation signal, and the variance components of image pitch is suppressed.Therefore, the change of image pitch is suppressed to the degree that can be used as the reference position.Reference pattern is any pattern of Y, M and C color.In the bottom of reference pattern, exist the reference mark that the laser beam by emission and the LSU 1 of corresponding this color of reference signal of phase detector 43 obtains, wherein phase detector 43 is corresponding to the color of reference pattern.For example, can realize the printing of reference mark by the specialized hardware that is provided for launching LSU 1 accordingly with reference signal.Alternatively, the microcomputer of control part can be realized above-mentioned functions by carrying out Interrupt Process.

Service engineering is an apprentice of the amplitude that obtains in the aligning toner pattern of printing with respect to the spacing variance components of every kind of color of Y, the M of reference position and C, and obtains the phase place with respect to the spacing variance components of reference mark in addition.The autodiagnosis program provides by the functional unit (not shown) that uses image forming apparatus 50 and has imported the amplitude of acquisition visually and the function of phase place.In addition, the autodiagnosis program provides according to the amplitude of every kind of color of the Y that is imported, M and C and phase place and has determined the amplitude of each modulation signal that will export and the function of phase place.

(the other different bearing calibrations of color alignment)

Above-mentioned method of adjustment is adjusted the rotatable phase of each photoreceptor, with the rotatable phase of the photosensitive drums of every kind of color of coupling Y, M and C.Here, for example, always under the situation as benchmark, can make the rotatable phase coupling of rotatable phase and the Y photosensitive drums 3d of other M and C photosensitive drums 3c and 3b in the phase place of Y photosensitive drums 3d.

Yet, in the present embodiment, show diverse ways.In diverse ways, with the corresponding photosensitive drums of the color of the amplitude maximum of spacing variance components 3 as benchmark, the rotatable phase of other photosensitive drums is matched.Phase place according to the photosensitive drums with maximum spacing variance components is exported modulation signal.The common modulation signal is imported into each Drive and Control Circuit 53 of Y, M and C, and therefore modulation signal becomes anti-phase fully with the color with maximum spacing variance components.About other color,, between spacing variance components and modulation signal, exist phase deviation along with the correction of rotatable phase.Yet, in modulation signal, suppressed the maximum spacing variance components effectively, and therefore can obtain remarkable on the whole correction result.

Figure 19 represents in the present embodiment, when with the common modulation signal application during to controlled each photoreceptor of rotatable phase, and the key diagram of the inhibition effect of peripheral speed variance components.In Figure 19, the peripheral speed variance components of the photoreceptor of every kind of color is present on the axis of ordinates, and the time is present on the abscissa axis.The variance components maximum of C.The phase place of the peripheral speed variance components of every kind of color of Y, M and C departs from mutually.This demonstrates the state (state of Figure 15) that each photoreceptor is in the matching rotation phase place.That is, it is in such state: the rotatable phase Be Controlled of photosensitive drums when stopping, and under the situation of synchronizing signal of the C that makes in the amplitude maximum of peripheral speed variance components as benchmark, the synchronizing signal of Y and M and the synchronizing signal of C coupling.Export such modulation signal, it has the phase place and the amplitude of the peripheral speed variance components that can eliminate C.Dotted line demonstrates the peripheral speed variance components of the every kind of color that obtains as the result who proofreaies and correct by modulation signal.C still comprises small change, and this is owing to measuring error etc. causes.Yet, to compare with the variance components of other Y and M, its peripheral speed variance components becomes minimum.Therefore, by determining the phase place of modulation signal, can suppress the peripheral speed variance components effectively.

Figure 20 is and the corresponding diagrammatic sketch of Figure 11, and is the key diagram of peripheral speed variance components that is expressed as follows the photosensitive drums of every kind of color under the state: the rotatable phase of each photoreceptor is adjusted to and makes the phase place of spacing variance components mate on image.In Figure 11,3d exports modulation signal as benchmark with the Y photosensitive drums.Simultaneously, in Figure 20, export modulation signal as benchmark with C photosensitive drums 3b with largest circumference speed fluctuation composition.

Black round indication among Figure 20 should be transferred to each position of Y, M on the same position on the recording medium and C image.Suppose the leading section of the image that black round position is defined as printing, the position of the leading section of the print image of Y, M and C and the coupling of the synchronizing signal among Figure 11.On the other hand, under the state after rotatable phase is adjusted, the position of the leading section of C print image and C synchronizing signal coupling, but the position of the leading section of Y print image is than 21.96 ° in advance of Y synchronizing signals, and leading 43.92 ° of the leading sections of C print image than C synchronizing signal, as shown in figure 20.Control part is controlled the phototiming of leading section of each print image of the previous synchronizing signal of this synchronizing signal as shown in figure 20.

The control method of phase place of the modulation signal of black (K) next, will be described.

Figure 21 is the key diagram of state of the modulation signal of the expression peripheral speed variance components that is used to suppress the K photoreceptor.Modulation generating circuit 51a gives the correction that adds Δ t from the reference signal of the phase detector 43a output of K, and deduct with photoreceptor and carry out the required dt corresponding correction time of time (90 °) of the rotation of 90 ° of the anglecs of rotation (sec), perhaps based on by adding that carrying out required dt corresponding correction time of time (270 °) the K synchronizing signal that (sec) obtains of the rotation of 270 ° of the anglecs of rotation with photoreceptor controls the phase place of (K's) modulation signal.Under the situation of Figure 21, control, make that the reference phase and the K synchronizing signal of (K's) modulation signal are synchronous.That is, control, make and in output K synchronizing signal, export on negative direction from 0 (K's) modulation signal that increases.

At last, it is evident that in addition to the implementation, have the various deformation example within the scope of the invention.These variation should not be considered to not belong to feature of the present invention and scope.Scope of the present invention should comprise and the implication of claim equivalence and the whole variation in the scope.

Claims (16)

1. coloured image forming device comprises:

A plurality of drum type photoreceptors be used on each circumferential surface forming the image of different colours, and described photoreceptor have at least two kinds of different diameters;

A plurality of drive divisions are used for making each photoreceptor rotate with predetermined circle speed to drive each photoreceptor with described diameter corresponding driving speed;

The correction signal efferent is used for the output speed correction signal, to proofread and correct periodic spacings change included in each established image;

Drive control part is used to control described drive division, to proofread and correct the described actuating speed of each photoreceptor by described velocity correction signal;

Alignment image formation portion is used for forming the alignment image that comprises a plurality of patterns on each photoreceptor;

Measurement section is used to measure the position of each pattern of formed alignment image; With

The variance components calculating part is used for the measurement result based on each pattern, the amplitude and the phase place of the corresponding spacing variance components of described swing circle of calculating and described photoreceptor,

Wherein, described correction signal efferent comprises the correction signal generating unit, and described correction signal generating unit is used for generating the described velocity correction signal that is used for every kind of diameter based on amplitude of being calculated and phase place,

Described velocity correction signal is the signal with cycle identical with the swing circle of each photoreceptor.

2. image forming apparatus as claimed in claim 1, wherein, described velocity correction signal is the shared signal with photoreceptor of same diameter.

3. image forming apparatus as claimed in claim 1, wherein, a plurality of coloured images that each photoreceptor forms photoreceptor by the black image of the diameter with first size and has a diameter of second size form photoreceptor and form.

4. image forming apparatus as claimed in claim 3, wherein, described coloured image forms photoreceptor and forms photoreceptor, magenta color image by yellow image and form photoreceptor and cyan image and form photoreceptor and form.

5. image forming apparatus as claimed in claim 3, wherein, described black image forms the diameter dimension of the diameter dimension of photoreceptor greater than described coloured image formation photoreceptor.

6. image forming apparatus as claimed in claim 1, wherein, described velocity correction signal is the shared signal of the mutually the same photoreceptor of diameter, and

The amplitude peak of the amplitude that the described spacing that described correction signal generating unit calculating will be employed each photoreceptor of described velocity correction signal changes and the mean value of minimum radius.

7. image forming apparatus as claimed in claim 1, wherein, at least a portion of described correction signal efferent also comprises:

Switching part is used to switch the state that the velocity correction signal that is generated was output to or was not output to the described drive control part of each photoreceptor; With

Switch control portion is used for the size according to the amplitude of the described spacing variance components of each photoreceptor, switches and the corresponding described switching part of described photoreceptor.

8. image forming apparatus as claimed in claim 1 also comprises:

Transfer member is used for the image that transfer printing is formed by each photoreceptor; With

The rotatable phase adjustment part is used to adjust the rotatable phase of described photoreceptor,

Wherein, a plurality of coloured images that each photoreceptor forms photoreceptor by the black image of the diameter with first size and has a diameter of second size form photoreceptor to be formed, and each photoreceptor with predetermined space along described transfer member setting;

Described rotatable phase adjustment part is calculated by each coloured image and is formed the relative misalignment amount that photoreceptor formed and be transferred to the phase place of described spacing variance components included in the image on the described transfer member, and adjust described rotatable phase, the periodic phase that makes each coloured image form the speed fluctuation of photoreceptor is mated based on the described misalignment amount of the phase place of being calculated.

9. image forming apparatus as claimed in claim 1 also comprises:

Transfer member is used for the image that transfer printing is formed by each photoreceptor; With

The rotatable phase adjustment part is used to adjust the rotatable phase of each photoreceptor, wherein

A plurality of coloured images that each photoreceptor forms photoreceptor by the black image of the diameter with first size and has a diameter of second size form photoreceptor to be formed, and each photoreceptor with predetermined space along described transfer member setting;

At least a portion of described correction signal efferent also comprises delay portion, and described delay portion is used to each photoreceptor to postpone described velocity correction signal from described correction signal efferent;

The described rotatable phase that each coloured image forms photoreceptor is adjusted based on the phase place of being calculated in described rotatable phase adjustment part, makes that forming the phase place that photoreceptor formed and be transferred to described spacing variance components included in the image on the described transfer member by each coloured image is mated; And

Described delay portion is according to based on described interval and predefined angle postpones each velocity correction signal, so that have the phase place of eliminating described spacing variance components.

10. image forming apparatus as claimed in claim 9, wherein, each photoreceptor also comprises:

Phase detector is used for detecting the reference value and the output reference signal that use in the control of described rotatable phase, wherein

At least a portion of described correction signal efferent also comprises the retardation adjustment part of the retardation that is used to adjust described delay portion;

The phase place of described retardation adjustment part more described reference signal and velocity correction signal of being generated in forming the process of image, and the result adjusts described retardation based on the comparison, with the phase place that the suppresses described velocity correction signal sequence change with respect to described reference signal.

11. image forming apparatus as claimed in claim 9, wherein, at least a portion of described correction signal efferent also comprises the amplitude adjustment part, and described amplitude adjustment part is used to be adjusted into the amplitude of the velocity correction signal that each photoreceptor generates.

12. image forming apparatus as claimed in claim 1, wherein, each photoreceptor also comprises:

Phase detector is used for detecting reference position and output reference signal in that the control of described rotatable phase is used; With

The mark addition portion is used for to add mark to described alignment image according to the output of described reference signal.

13. coloured image forming device as claimed in claim 8, wherein, described correction signal generating unit generates the velocity correction signal that has with the phase place opposite phases of the cyclical velocity change of benchmark photoreceptor, and the photoreceptor with the amplitude peak that calculates is used as the benchmark photoreceptor.

14. image forming apparatus as claimed in claim 13, wherein, each rotatable phase is determined in described rotatable phase adjustment part, makes other coloured image form the described rotatable phase coupling of the rotatable phase and the described benchmark photoreceptor of photoreceptor.

15. image forming apparatus as claimed in claim 13, wherein, described interval is that the adjacent coloured image that contacts with described transfer member respectively forms the interval between the position of photoreceptor, and described interval is the different distance of integral multiple that forms the circumferential length of photoreceptor with described coloured image.

16. image forming apparatus as claimed in claim 1, wherein, the described pattern of described alignment image comprises many straight lines that extend perpendicular to the sense of rotation of described photoreceptor, and is calculated the amplitude and the phase place of described spacing variance components far from the deviation of reference position by the position of measuring every straight line by described measurement section.

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