JP2918911B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus provided with a cleaning unit for cleaning a transfer body transport unit.

[Conventional technology]

A transfer device that is used in an image forming apparatus such as a copying machine, sequentially forms a plurality of images on an image carrier, and sequentially transfers and superimposes these images onto a transfer paper placed on a transfer body transporting unit to form a transfer image. The apparatus has been proposed in, for example, JP-A-62-118366 and JP-A-58-198062.

However, there is no disclosure in any of the above-mentioned publications of the cleaning means of the transfer body transport means usually provided in this type of transfer apparatus.

[Problems to be solved by the invention]

On the other hand, various proposals have been made by the present inventors for the cleaning means of this type of transfer body transporting means. In these proposals, however, the position of the cleaning means relative to the transfer body transporting means, the drive timing of the cleaning means and the transfer timing The relationship with the transfer speed of the body transport means is not taken into consideration.

For this reason, the cleaning of the surface of the transfer body conveying means may not be completely performed by the cleaning means at the next transfer operation. If the surface of the transfer body conveying means is not completely cleaned at the time of the transfer operation, an image formed by the transfer is unclearly formed, or an image in which dirt adheres to the image is formed.

An object of the present invention is to completely clean the surface of the transfer body conveying means by the cleaning means before the transfer operation,
An object of the present invention is to provide an image forming apparatus in which a clear image is always formed without contamination.

[Means for solving the problem]

In order to achieve the above object, the present invention provides an image forming unit for sequentially forming a plurality of images on an image carrier, and sequentially transferring these images on a transfer sheet conveyed by a reciprocating transfer body conveying unit at a transfer position. Transfer means for transferring in an overlapping manner;
An image forming apparatus provided with a cleaning unit for cleaning a surface of the transfer body transporting unit, wherein a transfer sheet of a maximum size used in the apparatus is transported in the forward direction by the transfer body transporting unit and the image forming unit The first transfer operation corresponding to the leading end of the image area on the transfer body conveying means when the transfer operation of the transfer body conveyance means is stopped after the transfer operation by
And after the transfer of the transfer body conveying means is stopped, the transfer body conveying means is conveyed in the backward direction, and the transfer is performed after the rear end of the transfer sheet of the maximum size passes through the transfer position of the image forming means. A second position corresponding to the rear end of the image area on the transfer body conveying means when the conveyance of the body conveyance means is stopped, and a second position corresponding to the leading end image position of the next transfer paper at the end of the final transfer of the current transfer paper. And a third position on the transfer body transporting means, which is cleaned by passing through the cleaning means when the transfer body transporting means moves forward for image transfer to the next transfer paper. The entire peripheral length of the transfer body transporting means and the arrangement position of the cleaning means are set for the transfer paper size.

[Action]

After the transfer operation of the image of the maximum size, the forward end position corresponding to the leading end of the image on the transfer body transporting unit that has been rotated forward and stopped, and on the transfer body transporting unit that has been rotated backward and stopped after the transfer operation, The rear end position corresponding to the rear end of the image is
The circumferential length of the transfer body transporting unit and the arrangement position of the cleaning unit are selected so as to be located downstream of the cleaning unit with respect to the forward rotation direction of the transfer body transporting unit.

For this reason, at the next transfer operation, the portion corresponding to the image transfer area on the surface of the transfer body conveying means is completely cleaned by the cleaning means, and a clear image without stain is formed by the transfer.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory view showing the structure of a copying machine to which the present invention is applied. 35 is a color image reading device, 7, 9, 11, and 13 are developing units (Y to BK), and 1 is an image carrier. Photoreceptor belts 1 and 5 are optical writing units, 31 is a fixing device, 17 is a transfer belt as transfer body transport means, 14 is a transfer tray, 32 is a paper discharge tray, and 25 is a transfer belt cleaner as cleaning means. .

As shown in the figure, a color image reading device 35 is disposed at the upper part of the case 36 of the copying machine, and the transfer paper tray 14T and the discharge tray 3
2 is attached to the case 36.

A transfer paper transfer path 38 is formed in the case 36 horizontally between the discharge tray 32 and the transfer paper tray 14T, and the transfer belt 17 wound around the drive roller 18 and the driven roller 19 transfers the transfer belt 17. The main part of the paper transfer path 38 is configured.

A paper feed roller 15 is arranged near the exit of the transfer paper tray 14T, and the transfer paper 14 derived from the paper feed roller 15 is sent to a transfer paper transport path 38 through a registration roller 16. .

In the vicinity of the driven roller 19, a transfer belt cleaner 25 is disposed in close proximity to the transfer belt 17, and in the vicinity of the transfer belt cleaner 25, a charge removing corona 22 is disposed. Also,
In the vicinity of the drive roller 18, a paper separation charger 24 is disposed in close proximity to the transfer belt 17, and the transfer paper transport path 38 is provided with a path switching member 26 near the drive roller 18.

At the center of the transfer paper moving path 38, the photosensitive belt 1 is wrapped around the drive roller 2 and the driven roller 3 in a direction perpendicular to the transfer paper transfer path 38 so as to be movable, and a transfer paper tray in a case 36 is provided. On the 14T side, a developing unit (Y) 7, a developing unit (M) 9, a developing unit (C) 11, and a developing unit (BK) 13 are disposed in close proximity to the photosensitive belt 1. These developing units are provided with a developing roller (Y) 6, a developing roller (M) 8, a developing roller (C) 10, and a developing roller (BK) 12, respectively.

On the side of the paper ejection tray 32 in the case 36, the driven roller 3
The optical writing unit 5 is disposed in the vicinity of the photoreceptor belt 1 so as to be in close proximity to the photoreceptor belt 1. A photoreceptor belt cleaner 29 is disposed between the fixing device 31 and the photoreceptor belt 1 so as to be in close proximity to the photoreceptor belt 1, and between the photoreceptor belt cleaner 29 and the optical writing unit 5. The static eliminator 30 and the charging corona 4 are disposed in close proximity to the device.

Further, a transfer corona 21 is provided in close proximity to the drive roller 2 with the transfer belt 17 interposed therebetween, and a paper adsorption charger 23 is disposed between the drive roller 2 and the registration roller 16 in close proximity to the transfer belt 17. I have.

FIG. 3 is an explanatory view of a drive control unit according to an embodiment of the present invention, wherein 1 is a photoreceptor belt, 17 is a transfer belt, 41 is a main board, and 42 and 43 are servo control boards.

As shown in FIG. 1, a photosensitive belt 1 is movably wound between a driving roller 2 and a driven roller 3, and a transfer belt 17 is interposed between a driving roller 18 and a driven roller 19 in a direction perpendicular to the photosensitive belt 1. Are movably wound.

A PC drive motor 36 is attached to the axis of the drive roller 2,
An encoder 37 is connected to the PC drive motor.
A rotation detection sensor 55 is attached to the shaft of the drive roller 2, and the detection signal of the rotation detection sensor 55 is transmitted to the main board 41.
Is input to the servo control board 43. The output signal of the encoder 37 is input to the servo control boards 42 and 43 and the main board 41, and the control signal is input from the servo control board 42 to the PC drive motor 36.

A transfer drive motor 39 is attached to the shaft of the drive roller 18, and an encoder 40 is connected to the transfer drive motor 39. The output signal of the encoder 40 is input to the servo control board 43, and the control signal from the servo control board 43 is input to the transfer drive motor 39. And the main board 41
Is input to a transfer belt cleaner 25 disposed near the transfer belt 17.

The transfer belt cleaner 25 is a roller type that performs cleaning by rotating a conductive roller for cleaning during a cleaning operation, and a blade type that performs cleaning by contacting and pressing a cleaning blade against a transfer belt during a cleaning operation. And used.

 Hereinafter, the roller type will be mainly described.

FIG. 6 is an explanatory view of a control mechanism of a transfer belt cleaner according to one embodiment of the present invention using a roller type transfer belt cleaner, wherein 17 is a transfer belt, 25a is a conductive cleaning roller, and 45 is a cleaner drive. The motor 50 is a bias power supply.

As shown in the figure, an output terminal of a bias power supply 50 is connected to a cleaning roller 25a via a high-voltage relay contact 51, a toner removing blade 25b is attached to the cleaning roller 25a, and the cleaning roller 25a The cleaning counter electrode 44 is disposed opposite to the cleaning counter electrode 44 via the belt 17, and the cleaning counter electrode 44 is grounded.

The bias power supply 50 is provided with DC input terminals t ₁ and t ₂ and a trigger input terminal t _3, and a DC input terminal t ₁ and a trigger input terminal t ₃
A high withstand voltage relay 47 is connected between the
Is connected in parallel with a cleaner driving motor 45, and a cleaner driving motor 45 is connected to an output terminal of the control circuit 48 via a power supply 49.

The rotating shaft of the cleaner drive motor 45 is connected to the rotating shaft of the cleaning roller 25a via drive gears 46a to 46d.

In this embodiment, the ON / OFF switching of the bias power supply 50 to the cleaning roller 25a via the high withstand voltage relay contact 51 and the ON / OFF of the power supply 49 to the cleaner drive motor 45 via the control circuit 48. Is performed simultaneously and outside the transfer process period, as described later.

FIG. 4 is an explanatory view of an image position on the transfer belt and an arrangement position of the transfer belt cleaner in one embodiment of the present invention using a roller type transfer belt cleaner, where 1 is a photosensitive belt, and 17 is a transfer belt. , 25 are transfer belt cleaners.

As shown in FIG. 4, the transfer paper 33 placed on the transfer belt 17 is transferred in the forward direction (to the left in FIG. 4) and is transferred from the leading end by the transfer corona 21. After reaching the position shown in FIG. 34, the process returns and the next transfer is performed. In this case, the position of the portion corresponding to the leading end of the image on the transfer belt 17 at the time of forward rotation of the transfer paper of the maximum size is A, and the same transfer belt 17 at the time of return rotation.
Assuming that the position of the upper image corresponding to the trailing edge is B and the position corresponding to the leading image position of the next page at the end of the final transfer of the current page is C, in the embodiment, points A, B, and C are all the transfer belt 1.
Transfer belt 1 so that it is upstream with respect to the forward
A transfer belt cleaner 25 is disposed in close proximity to the transfer belt 7.

This is realized by selecting the entire circumference of the transfer belt 17 and the arrangement position of the transfer belt cleaner 25 with respect to the maximum transfer paper size so as to satisfy the above-described conditions.

FIG. 7 is an explanatory view of an image position on a transfer belt and an arrangement position of the transfer belt cleaner in another embodiment of the present invention using a blade type transfer belt cleaner. In this case, FIG. Instead of the roller type transfer belt cleaner 25, a blade type transfer belt cleaner
25 'is used.

In FIG. 7, similarly to FIG. 4, the transfer belt 17 is closely opposed to the transfer belt 17 so that points A, B, and C are all upstream with respect to the forward rotation direction of the transfer belt 17. Cleaner
25 'are provided.

The operation of the embodiment having the configuration described below will be described below.

FIG. 2 is a signal waveform diagram showing an operation of a copying machine to which the present invention is applied, and FIG. 5 is a signal waveform diagram showing a cleaning operation in an embodiment using a roller type transfer belt cleaner.

The operation of the embodiment using the roller type transfer belt cleaner will be described with reference to FIG. 2 and FIG.

When the print SW is turned ON (FIG. 2a), the PC drive roller 2 rotates the photoconductor belt 1 clockwise by the PC drive motor 36, and rotates at a linear speed of VP in the direction of the arrow.

At the same time, the transfer driving motor 39 also rotates the transfer paper transport belt 17 (hereinafter abbreviated as transfer belt) forward (g, g in FIG. 2).
h signal and the velocity diagram of j)), and rotate in the direction of the left arrow with the VF flux. It is controlled and driven to rotate under the condition of VP = VF.

Now, the photoreceptor belt 1 (hereinafter abbreviated as PC belt)
The charge is removed by the charge remover 30, and the front surface is uniformly charged by the charger 4, but is processed to satisfy the following conditions.

1. The static eliminator performs light irradiation or application of a static elimination corona to the surface of the PC belt from which the toner on the surface has been removed by a PC cleaning device in advance, so that the surface potential of the PC belt becomes approximately OV.

2. In the case of the negative-positive process, the toner adheres to an uncharged portion on the surface of the photoreceptor, so that the entire surface of the PC belt must be uniformly charged by the charger.

3. The charger performs uniform charging by corona discharge, but generates small ozone by discharge. This ozone is decomposed in a short time when the discharge is stopped, but may have an adverse effect on the PC belt surface and impair the sharpness of the image. Therefore,
Air is sent from the back of a charger (not shown) by a fan or the like, or suction is performed to eliminate the influence of ozone. By the way, PC
A rotation detection sensor 38 is provided on the shaft of the driving roller 2 so that a detection pulse is generated for each rotation of the roller (FIG. 2d).

In the example shown in FIG. 2, the semiconductor laser (hereinafter abbreviated as LD) of the optical writing unit is controlled and started to be driven at the timing of the third pulse of the first rotation detection sensor.
However, other types of lasers or other optical writing units such as LED arrays, LCD arrays, etc. may be used.)
First, optical writing based on the Y image data is started to form an electrostatic latent image.

This image data is supplied to a color image reading device 35 installed at the top of FIG.
Each color separation light is read, and image processing is performed based on the sensitivity level of each color light to obtain Y, M, C, Bk
(Black) image data for each color.

Alternatively, image data output from another color image processing system (for example, a color facsimile, a word processor, a personal computer, etc.) may be used. The connection interface for that may be individually handled.

By the way, developing devices 7, 9, 11, 13 for visualizing the electrostatic latent image
Is located at a position where the developing rollers 6, 8, 10, and 12 do not normally contact the PC belt surface.

Then, only during a period from immediately before the latent image surface of the corresponding color reaches the position of the developing roller of each color to immediately after the passage, the developing device of the corresponding color is pressed to the left in FIG. The roller is set to a position where a predetermined amount of contact occurs.

At the same time, in order to provide only the developing device with the developing function, the driving of the developing roller and the portion contributing to the development is started (m to p in FIG. 2).

First, since the latent image of the Y image is formed, the Y developing unit 7 is brought into contact with and driven (m in FIG. 2) the surface of the Y developing unit 7 at a time to display the Y image. Image.

Next, in the transfer process, the transfer belt 17 is moved by the roller 20 so that the transfer portion (PC drive roller portion) contacts the PC belt surface.
The vertical position is switched.

Entering the cleaning process with the start of the transfer process,
The bias power supply 50 is applied to the cleaning roller 25a in FIG. 6, and at the same time, the cleaning roller 25a is rotated by the driving of the drive motor 45, and the cleaning operation of the transfer belt 17 is performed.

Then, when the printing operation starts, the transfer belt 17 is driven in the direction of the left arrow as described above, and then the transfer belt contact / separation switching roller 20 is pressed to the upper position to bring the transfer belt 17 into contact with the PC belt 1. Let it. (T in FIG. 2) At a predetermined timing, the transfer paper 14 is
Then, the sheet is conveyed by the registration roller 16 in a timely manner so as to match the image position formed on the PC belt surface.

The conveyed transfer paper 14 is subjected to corona charge of a predetermined polarity by a paper adsorption charger 23 (x in FIG. 2), and is brought into close contact with the transfer belt so that the paper position does not shift during transfer. The transfer belt contact / separation switching roller 20 is also used as a counter electrode of the paper adsorption charger 23 to simplify the apparatus.

Note that the transfer belt is neutralized by uniformly removing the entire surface of the transfer belt with the charge removing corona 22 prior to the first color transfer process (w in FIG. 2). At this time, the cleaning process is also performed by the transfer belt cleaner 25 as described above.

By the way, when the front end of the visualized Y image reaches the TS point which is a predetermined distance from the transfer position T, the transfer drive motor forward rotation start signal S ₁ (h in FIG. 2) is controlled to drive the transfer drive motor 39. Input to the circuit 43.

However, in the S ₁ point, is already forward rotation in to continue the forward operation as it is. Timing of S ₁ (j of FIG. 2) is substantially the leading edge of the transfer sheet is RT point, i.e. shall apply when it reaches the position of the front direction l ₁ of the transfer position T, Y image leading edge of the PC belt together is , the front direction l ₁ of the T-point
It is when it reaches the position T ₃ points.

Which in the example of FIG. 2, the Y image data writing start timing, a PC drive roller 4 rotations, further comprising a time of the rotating encoder pulse number P ₀ equivalent of PC drive motor. (D, e, f, h in FIG. 2) During this time, the PC belt has moved by the distance from point E (image writing position) to point T _S.

After a time t ₁ has elapsed from S ₁ point, Y image top, and the transfer sheet tip both move the distance l _1, and reaches the transfer position T point, thereafter, the Y image is transferred by a transfer corona charger 21 Done.

PC drive motor encoder (PC) 37 at time t ₁
The number of pulses P _1, the number of pulses of the transfer drive motor encoder (T) 40 is PT _1. (E, k in FIG. 2) Here, as the resolution of both encoders, if the belt movement dimensions per pulse are the same, then P ₁ = PT ₁ and the ratio between the two is if a, P ₁ and PT ₁ becomes a value corresponding to the coefficient a.

In this example, a description will be given below on the assumption that P ₁ = PT ₁ .

When the Y image transfer process proceeds, the leading edge of the transfer paper separates from the transfer belt, passes over the solid line position of the transfer paper path switching member 26, and advances toward the paper leading edge guide plate 27.

Then proceeding further Y image transfer process, the transfer sheet trailing edge, when the T point has passed through the distance l ₂ min, i.e., the transfer sheet from the S ₁ point, l ₂ + lp (transfer sheet size) + l ₂ When the distance is moved (time t ₁ + t ₂ ), the transfer drive motor is rotated in reverse by the transfer drive motor reverse rotation signal. (I in FIG. 2) At this time,
The transfer paper 14 is at a position indicated by a two-dot chain line indicated by 34.

At the time of or immediately before the reverse rotation operation of the transfer drive motor, the bias power supply 5 to the cleaning roller 25a is supplied.
The application of 0 and the application of the power supply 49 to the cleaner drive motor 45 for driving the cleaning roller 25a are simultaneously turned off,
The rotation of the cleaning roller 25a is stopped, and the cleaning roller 25a is set in a floating state.

Prior to this reverse rotation, the transfer belt contact / separation switching roller
20 is lowered to the lower position, and the transfer belt is separated from the PC belt surface.

The transfer belt and transfer paper are rotated in the right direction VR by the reverse rotation.
Make a quick return at (> VF) speed. Then t ₂
A short return times of the distance equal to the distance moved to the left in t ₁ + t _2, to return to the position control in the right direction.

At the time of this return, the rear end of the transfer paper separates from the transfer belt and advances toward the paper rear end guide plate 28. Then, the transfer paper 14 accurately returns by a predetermined distance, stops at the position indicated by the two-dot chain line 33 (the paper leading end position is the RT point position), and waits for the transfer of the M image of the second color (time t ₄ ).

On the other hand, in the case of the PC belt 1, during the transfer of the Y image of the first color, the M image of the second color has already been formed. That is, based on the M image data, the formation of the electrostatic latent image of the optical writing by controlling and driving the LD starts from the start of the Y image writing.
It starts when the PC drive roller has rotated an integer number of times, in the case of FIG. 2 of the present example, four times.

The developing device is in contact with the Y image device only in the Y image region.
Before the second color M image area arrives, the Y developing device 7 is separated from the PC belt surface and the driving is stopped.

Instead, after the Y image area passes, the M developing device 8
Before the end of the M image area arrives, it is brought into contact with and driven on the PC belt surface (n in FIG. 2), and only the M image latent image area is visualized as an M image.

Then when the M image tip reaches the T _s point, i.e. 1 as in the case of color of Y image, the M image data writing start timing, pulse number P ₀ equivalent PC drive roller 4 rotations and PC drive motor encoder the time was multiple-rotational movement, to enter the transfer driving motor forward rotation start signal S ₂ to the control drive circuit 43.

At the same time or slightly later, the transfer belt contact / separation switching roller 20 starts the pressing operation in the upper position direction and contacts at least until the leading end of the transfer paper reaches the point T.

Now, PC belt 1 at time t ₁ from the timing of S _2, as in the case of previous Y image, PC drive motor encoder (P
The number of pulses in C) is P ₁ , and the PC belt surface travel distance l ₁ .

So even people of the transfer paper during the t _1, from the state of zero speed
Start up to VF (= VP) and during this time S ₁ of the first color
To be the same PT ₁ as the number of pulses in the t ₁ hour from, performs the position control such Again is P ₁ = PT ₁ and both coincide.

Thus, again, will be the leading edge of the transfer sheet by T ₁ has moved l _1, 1-color Y image and the second color M image is aligned with the transfer paper.

Thereafter, the same process as described above is repeated. That is, M image transfer, transfer paper quick return, C image data writing, C development, C image transfer, transfer paper quick return,
Then, the process proceeds to Bk image data writing, Bk development, and Bk image transfer.

 Next, a description will be given of the steps after the Bk image transfer.

During the Bk image transfer process, the paper path switching guide plate 26
However, the transfer paper is switched to the dashed line position, and the transfer paper during the transfer process advances toward the fixing device 31 from the leading end while being discharged by the paper separating charger, and remains at the rear end of the transfer paper even after the transfer is completed. It is carried out. (J, u, v, y in FIG. 2) At this time, the transfer belt 17 is uniformly charged by applying a charge removing corona from the rear end of the first image area at a timing when the transfer belt 17 passes through the charge remover 22. . (W in FIG. 2) When the final transfer step of the Bk image transfer is completed, at the same time or at a predetermined timing thereafter, the application of the bias power supply 50 to the cleaning roller 25a and the cleaning roller 2
The application of the power supply 49 to the cleaning drive motor 45 for driving 5a is performed at the same time, and the cleaning of the surface of the transfer belt 17 serving as the second image area is restarted.

In this case, as already described with reference to FIG. 4, the position A of the leading end of the image on the transfer belt 17 at the time of the forward rotation of the transfer paper of the maximum size, the position B of the trailing end of the image at the time of the backward rotation, All of the positions C corresponding to the leading edge image positions are located upstream of the transfer belt cleaner 25 with respect to the forward rotation direction of the transfer belt 17. Therefore, before the next transfer, the portion corresponding to the image area on the transfer belt 17 is completely cleaned by the transfer belt cleaner 25, and a clear transfer image without contamination is formed.

When performing a repeat operation as in the case of FIG.
After writing the Bk image data for the first sheet, as shown in FIG. 2, the process proceeds to write the Y image data for the second sheet, and the operation control of the transfer paper and the transfer belt also performs the same operation as that from the beginning of the first sheet. Do.

After the transfer, the residual toner is removed from the PC belt 1 by the cleaner 29, the residual charge is removed by the charge remover 30, and the PC belt 1 moves toward the charger 4.

Eventually, the operation is stopped after the last color print is carried out to the tray 32 and the PC belt 1 and the transfer belt 17 are cleaned and neutralized, and the operation returns to the initial state.

At the time of copying the last page, the cleaning operation is continued as it is from the end of the final transfer until the transfer motor stops.

FIG. 8 is a signal waveform diagram showing a cleaning operation in the embodiment of the present invention using a blade type transfer belt cleaner. In this case, ON-OFF switching between contact and separation of the transfer belt cleaner is performed in the process of the transfer belt. It takes place outside of the period.

In the above description, the order of image formation is Y, M, C, and Bk, and the arrangement of the developing devices is Y, M, C, and Bk from the top. However, the present invention is not limited to this.

Also, the formation of the electrostatic latent image of each color has been described by a method of optically writing with an LD or the like using each color image data subjected to digital image processing, but an analog optical image of a normal electrophotographic copying machine is placed at a point E at a predetermined position. The same color printing can also be performed by performing the timing position control described above to form an image.

Up to this point, the description has been given of the four-color superimposition recording of Y, M, C, and Bk. However, in the case of these two-color or three-color superimposition recording, the image formation and transfer of the necessary colors are performed successively. Three or three times
The operation of each unit is controlled so that this is completed.

In the case of single-color recording, the developing device for that color is contacted and driven until the predetermined number of sheets is completed, and the transfer belt is
The paper path switching guide plate 26 is kept in contact with the PC belt, and is held at the position where the transfer paper is guided in the direction of the fixing device 31 to perform the recording operation.

Therefore, in the repeat recording, the print creation speed is 4/3 times for the three colors, twice as much for the two colors, and four times for the single color as compared with the four colors.

Developed colors are not limited to the above four colors, but any desired colors such as Blue, Green, Red, etc.
It is also possible to use a combination.

As described above, according to the present embodiment, the position A corresponding to the leading edge of the image when the transfer paper of the maximum size is rotated with respect to the transfer belt 17, the position B corresponding to the rear end of the image when the paper is rotated backward, and the final transfer is completed Since the position C corresponding to the leading edge image position of the next page at the time point is located on the upstream side of the transfer belt cleaner, an accurate and efficient cleaning operation is performed.

In addition, since the ON / OFF switching of the operation of the transfer belt cleaner is performed outside the transfer process period, no sudden load fluctuation occurs on the transfer belt 17 by controlling the cleaning operation.
Also, there is no leakage of electric charge from the transfer belt 17, and a high-quality image without displacement, jitter or image unevenness is formed.

〔The invention's effect〕

As described above in detail, according to the present invention, during the transfer operation, the surface of the transfer body conveying means corresponding to the transfer area of the maximum image is completely cleaned by the cleaning means, so that clear transfer without stains can be achieved. An image can be formed.

[Brief description of the drawings]

1 to 8 are views for explaining an embodiment of the present invention. FIG. 1 is an explanatory view of a copying machine to which the present invention is applied, and FIG.
FIG. 3 is a signal waveform diagram showing the operation of a copying machine to which the present invention is applied, FIG. 3 is an explanatory diagram of a drive control unit, and FIG. 4 is an image on a transfer belt of an embodiment using a roller type transfer belt cleaner. Explanatory drawing of the position and the arrangement position of the transfer belt cleaner,
FIG. 5 is a signal waveform diagram of a cleaning operation of an embodiment using a roller type transfer belt cleaner, FIG. 6 is an explanatory diagram of a control mechanism of the roller type transfer belt cleaner, and FIG. 7 is a blade type transfer belt cleaner. FIG. 8 is an explanatory diagram of an image position on a transfer belt and an arrangement position of a transfer belt cleaner of the embodiment using the transfer belt cleaner. FIG. 8 is a signal waveform diagram of a cleaning operation of an embodiment using a transfer belt cleaner of a blade system. DESCRIPTION OF SYMBOLS 1 ... Photoreceptor belt, 2 ... Driving roller, 3 ... Driving roller, 4 ... Charging corona, 5 ... Light writing unit, 6
Developing roller (Y), 7 Developing device (Y), 8 Developing roller (M), 9 Developing device (M), 10 Developing roller (C), 11 Developing device ( C), 12: Developing roller (B
k), 13: Developing unit (Bk), 14: Transfer paper, 14T: Transfer paper tray, 15: Feed roller, 16: Registration roller, 17
…… Transfer belt, 18… Drive roller, 19 …… Follower roller, 20… Contact / separation switching roller, 21 …… Transfer corona, 22 ……
Static elimination corona, 23: Paper adsorption charger, 24: Paper separation charger, 25: Transfer belt cleaner, 25a: Cleaning roller, 25b ... Toner removal blade, 26: Path switching member, 29 ... Photoreceptor belt cleaner, 30: Static eliminator, 31: Fixer, 32: Discharge tray, 35: Color image reader, 36: PC drive motor, 37, 40 ... Encoder, 39: Transfer Drive motor, 41 ... Main board,
42, 43 ... servo control board, 45 ... cleaner drive motor, 49 ... power supply, 50 ... bias power supply.

──────────────────────────────────────────────────続 き Continued on the front page (72) Kazushige Taguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Noriyuki Kimura 1-3-6 Nakamagome, Ota-ku, Tokyo No. Ricoh Co., Ltd. (56) References JP-A-58-113951 (JP, A) JP-A-62-136680 (JP, A) JP-A-63-97981 (JP, A) (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) G03G 21/10-21/12 G03G 15/14-15/18

Claims (1)

(57) [Claims] An image forming means for sequentially forming a plurality of images on an image carrier, and a transfer means for sequentially transferring the images at a transfer position on a transfer paper conveyed by a reciprocating transfer body conveying means. And a cleaning unit that cleans the surface of the transfer body transport unit, wherein the transfer paper of the maximum size used in the apparatus is transported in the forward direction by the transfer body transport unit and the image is transferred to the transfer paper transport unit in the forward direction. The first position corresponding to the leading end of the image area on the transfer body transport unit when the transfer operation by the forming unit is completed and the transfer of the transfer body transport unit is stopped, and the transfer of the transfer body transport unit is stopped. Later, the transfer body conveying unit is conveyed in the backward direction, and the conveyance of the transfer body conveying unit is stopped after the rear end of the transfer sheet of the maximum size passes through the transfer position of the image forming unit. The second position corresponding to the rear end of the image area on the transfer body transporting unit at the time and the position on the transfer body transporting unit corresponding to the leading end image position of the next transfer paper at the end of the final transfer of the current transfer paper The third position corresponds to the maximum transfer paper size so that the transfer member may be cleaned by passing through the cleaning means when the transfer body transport means moves forward to transfer an image to the next transfer paper. An image forming apparatus, wherein an entire circumference of a body conveying unit and an arrangement position of the cleaning unit are set.