JP2769349B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an image forming apparatus such as a copier, a printer, a recording apparatus, and the like, which includes a manual feed table for manual paper feed and a transfer belt for conveying a transfer paper to a transfer position. The present invention relates to a forming apparatus.

[Conventional technology]

For example, in a negative-positive digital copying machine as shown in FIG. 6, each of a main scanning direction (a paper width direction orthogonal to a paper feeding direction) and a sub-scanning direction (an arrow A direction coinciding with the paper feeding direction) is used. The width of the writing area is determined by a signal from a sheet size detecting means for detecting the size of the transfer sheet P in the paper cassette 1A or 1B.

However, in the case of manual paper feeding from the manual paper feeding table 2, since a transfer paper of an arbitrary size is inserted, it is not possible to determine the writing area width using the signal from the paper size detecting means as described above. Since the width of the writing area in the main scanning direction cannot be determined, for example, the position of a slider (not shown) that moves in conjunction with the pair of side fences 3, 3 that can move in the width direction of the manual feed table 2 is detected. Has decided it.

The width of the writing area in the sub-scanning direction is determined by a light writing unit 6 when a registration sensor (which may be a paper end sensor) 7 disposed in front of the registration roller 4 detects the rear end of the transfer paper P. The writing is stopped by stopping the laser beam emitted from the photosensitive drum 5 from the above, and the writing area width is determined.

[Problems to be solved by the invention]

As described above, even if the writing area width in the main and sub scanning directions at the time of manual paper feed is determined by the position of the side fence 3 and the detection of the rear end of the transfer paper by the registration sensor 7,
The distance between the writing position Lp and the transfer position Tp is relatively short as in the copying machine of FIG.
In the case of an image forming apparatus that does not use a transfer belt, the problem does not often occur.

This is because even when the registration sensor 7 detects the trailing edge of the transfer sheet P and stops writing, the toner image (visible image) formed on the photosensitive drum 5 remains within the transfer sheet P (in the sub-scanning direction). In many cases).

In the case of the copying machine shown in FIG. 6, even if the toner image on the photosensitive drum 5 is formed outside the area of the transfer paper, this does not cause any problem. In the case where the transfer belt 8 is used as in the copying machine shown in FIG. 7 (the parts corresponding to FIG. 6 are denoted by the same reference numerals), the toner image is located outside the area of the transfer paper. Is formed, the transfer belt 8 is contaminated by the toner image, and the back transfer dirt is generated on the subsequent transfer paper, and the load on the transfer belt cleaner 9 for removing the dirt is increased. There was.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to prevent a toner image from being transferred onto a transfer belt during manual paper feeding in an image forming apparatus having a transfer belt.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a photosensitive member which is rotated by being charged by charging means, and an electrostatic member which forms an electrostatic latent image by irradiating the photosensitive member with laser light at a predetermined writing position. A latent image forming unit, a developing unit that develops the electrostatic latent image into a visible image, a transfer belt that conveys the transfer paper to a transfer position for transferring the visible image onto the transfer paper, and a manual feed of the transfer paper An image forming apparatus having a manual feed table for feeding paper in a manual feed mode, wherein a manual feed paper detection sensor for detecting the presence or absence of transfer paper set on the manual feed table is provided from the paper detection position of the sensor to the transfer position. At a position where the distance on the paper transport path and the distance along the photosensitive surface of the photoreceptor from the writing position to the transfer position are substantially equal, and after the manual paper detection sensor detects the transfer paper, it is detected. Without detection One is provided with a electrostatic latent image forming stop control means for stopping the electrostatic latent image formed by the electrostatic latent image forming unit when the.

(Operation)

According to the image forming apparatus configured as described above, the electrostatic latent image formed on the photoreceptor by irradiating the laser beam at the predetermined writing position by the electrostatic latent image forming means is visualized by the developing means. When the trailing edge of the transfer paper passes through the manual paper detection sensor and the sensor no longer detects the transfer paper, the electrostatic latent image formation stop control means controls the electrostatic latent image formation by the electrostatic latent image forming means. Stop formation.

Therefore, by adjusting the timing so that the leading edge of the visible image on the photoconductor and the leading edge of the transfer paper coincide with each other at the transfer position, the paper feed path from the paper detection position of the manual paper detection sensor to the transfer position can be adjusted. Since the distance and the distance along the photosensitive surface of the photoreceptor from the writing position to the transfer position are almost equal, it is necessary to transfer all of the image to the rear end of the visible image on the photoreceptor within the area of the transfer paper. it can.

〔Example〕

Hereinafter, a specific description will be given based on an embodiment of the present invention.

FIG. 1 is a schematic configuration diagram showing a main part of a color recording device as an image forming apparatus according to the present invention and its periphery, and FIG. 2 is an overall configuration diagram showing the entire color recording device of FIG.

As shown in FIG. 2, the color recording apparatus includes a printer unit 10 having various units for executing various image forming processes therein, and a document D provided on the printer unit 10 and placed on a contact glass 11. And an image reading unit 20 that reads the image of the image.

The printer unit 10 includes a PC driven roller 12 and a PC that are rotatably disposed at a substantially
A photoreceptor belt 14 that is charged by a charger 19 and rotates is stretched between the transfer roller 13 and a transfer roller 15 and a transfer driven roller 16 under the PC drive roller 13. Transfer paper in the transfer position to transfer the visual image to
The transfer belt 17 to be conveyed to Tp is arranged in the horizontal direction.

Further, on the upper left side of the photoreceptor belt 14, a laser beam is irradiated on the photoreceptor belt 14 at a predetermined writing position Lp based on image data (an image is formed where the light hits) to form an electrostatic latent image. Optical writing unit 18 serving as an electrostatic latent image forming means for forming an image
A charger 19, a static eliminator 21, and a photoreceptor belt cleaner 22 are provided at the lower portion, and an electrostatic latent image on the photoreceptor belt 14 is developed to the right of the photoreceptor belt 14. Each developing device 24Y, 24M, 24C, 24B having developing rollers 23Y (yellow), 23M (magenta), 23C (cyan), and 23B (black) to be visualized is used for each of the four colors used. Each is provided correspondingly.

Then, the transfer corona 26 is transferred to the transfer portion 25 of the transfer belt 17,
At the top of the transfer belt 17, a paper adsorption charger 27 and a paper separation charger 28 are provided, and at the bottom, a static eliminator is provided.
A transfer belt cleaner 31 and a transfer belt cleaner 31 are provided, respectively.
17 is brought into contact with the photoreceptor belt 14 in the transfer section 25,
A contact / separation switching roller 32 that can be moved up and down to separate them is provided.

A paper trailing end guide plate 33 is disposed on the right side of the transfer belt 17, and a paper feed cassette 34 that can be inserted into and removed from the main body 30 is provided above the transfer belt 17. Accordingly, a manual feed table 36 for manually feeding a transfer paper having a manual paper detection sensor 35 which can enter as shown by a solid line on the transfer paper P in the paper feed cassette 34 is provided.
Is fed in the direction of arrow C by the feed roller 37, the transfer paper P is skew-corrected by the registration roller 38, and is fed onto the transfer belt 17 at a predetermined timing.

Further, a switching claw 39 for switching the transfer path of the transfer paper P on the transfer belt 17 is provided on the downstream side of the transfer belt 17 so that the transfer paper P is transferred to the paper leading end guide plate 41 and the fixing device.
The transport path is switched to 43. And
The transfer paper P that has passed through the fixing device 43 is discharged onto a paper discharge tray 45 attached to the outside of the main body 30.

As shown in FIG. 3, a PC drive motor 53 and an encoder 54 for driving the PC drive roller 13 are provided on an axis of the PC drive roller 13, and a transfer drive motor 55 and an encoder 56 for driving the drive are provided on an axis of the transfer drive roller 15. Attached and PC driven roller
A rotation detection sensor 59 is installed on the 13 side and its PC drive roller
The detection pulse is output every time the motor 13 rotates once in the direction indicated by the arrow.

On the other hand, the image reading section 20 has a lamp 46 which is, for example, a fluorescent lamp for scanning and illuminating the original D on the contact glass 11 as shown in FIG. Is incident on the image forming lens 57 via the mirrors 47, 48, and 49, for example, red R, green G, and blue B.
The color-separated light is read by the image reading device 58, and image processing is performed based on the intensity level of each color light to obtain Y (yellow), M (magenta), C (cyan), and B (black). Each color is written image data.

The manual paper detection sensor 35 is for detecting the presence or absence of the transfer paper set on the manual paper table 36. For example, it is a reflection type photo sensor and is attached to the back of the manual paper table 36 as shown in FIG. Detection hole 36a
The presence or absence of the transfer sheet P at the sheet detection position Sp is detected by projecting light into the inside.

Then, the laser beam emitted from the optical writing unit 18 is moved from the writing position Lp on the photoreceptor belt 14 to the transfer unit 25.
The distance l _LT along the photosensitive surface of the photoreceptor belt 14 in the transport direction (the direction indicated by the arrow E) to the transfer position Tp, and the paper transport path from the transfer position Tp to the paper detection position Sp of the manual paper detection sensor 35. The manual paper detection sensor 35 is installed so that the distance l _TS is substantially equal.

Further, the manual paper detection sensor 35 is connected via a detection circuit 60 to an input port of a control device 50 for controlling each part of the color recording apparatus.

As the detection circuit 60, for example, a circuit as shown in FIG. 4 is used, and if a DC voltage Vcc is applied, a light emitting unit (LED)
35a is always on and emits light. When the light is reflected on the back surface of the transfer paper and enters the light receiving section (phototransistor) 35b, the current flowing there increases, so the voltage drop due to the resistance Rs increases, and the output decreases. The voltage Vs decreases.

Then, when the transfer paper is fed and the light from the light emitting unit 35a does not hit the transfer paper, the amount of light reflected on the light receiving unit 35b is greatly reduced, so that the current I flowing there is reduced, and the output voltage Vs is reduced. To rise.

This voltage Vs is compared with the reference voltage Vr by the comparator 62 to be binarized.

Therefore, the output signal Vo of this detection circuit becomes “H” when the manual paper detection sensor 35 detects the transfer paper, and becomes “L” when it does not detect the transfer paper.

The control device 50 includes a central processing unit (CPU) having various determination and processing functions, a ROM that is a program memory that stores various programs and fixed data, a RAM that is a data memory that stores processing data, and an input / output circuit. (I / O).

The control device 50 controls the manual paper detection sensor 35.
And a control circuit for inputting a paper detection signal via the detection circuit 60, and stopping the writing signal (signal for emitting laser light) to be output to the optical writing unit 18 when the signal is no longer input. Detection sensor 59 and encoder
Signals from various sensors such as 54 and 56 are input to control the drive and stop of various drive systems including the PC drive motor 53 and the transfer drive motor 55.

In this embodiment, the control device 50 corresponds to an electrostatic latent image formation stop control unit.

Next, the operation of this embodiment configured as described above will be described with reference to the timing chart of FIG.

First, when the paper is automatically fed from the paper cassette 34, the manual feed table 36 is closed and retracted to the position indicated by the phantom line in FIG. 2, and when the paper is fed manually, the manual feed table 36 is closed. And set it to the position shown by the solid line.
The transfer paper P is inserted from above to the paper feed roller 37, and the print switch (not shown) is turned on.

Then, the PC drive motor 54 shown in FIG.
The driving roller 13 rotates clockwise, and the photosensitive belt 14
Starts driving at a predetermined linear velocity Vp (a in FIG. 5) in the direction of arrow E in FIG.

At the same time, the transfer drive motor 56 is rotated in the forward direction transfer driving roller 15 is rotated in the counterclockwise direction, arrow F ₁ direction the linear velocity Vp equal linear velocity Vf of the transfer belt 17 FIG. 2 (5 The driving is started in e) of FIG.

In addition, the contact / separation switching roller 32 is raised to a position shown by a solid line in FIG. 2 by moving means (not shown), and the transfer belt 17 contacts the photosensitive belt 14 at the transfer section 25 (m in FIG. 5).
I do.

Further, the toner on the surface of the photoreceptor belt 14 is removed by the photoreceptor belt cleaner 22, the surface potential of the photoreceptor belt 14 is reduced to approximately 0 V by the charge eliminator 21, and the entire surface is charged by corona discharge by the charger 19. Charges uniformly.

In this embodiment, as shown in FIG. 5C, at the timing of the third pulse of the rotation detecting sensor 59, the laser light from the optical writing unit 18 is applied to the writing position on the photosensitive belt 14.
By irradiating Lp (FIG. 1), optical writing based on yellow image (hereinafter referred to as Y image) data is first started, and a negative electrostatic latent image is formed on the belt.

Each developing unit of the developing units 24Y, 24M, 24C, and 24B is located at a position where the developing rollers 23Y, 23M, 23C, and 23B do not contact the photosensitive surface of the photosensitive belt 14, respectively, in a normal state. The developing rollers 23Y, 23M, 23C, and 23B of the developing units of the respective colors correspond to the latent image surfaces of the colors corresponding to the developing rollers 23Y, 23M, 23C, and 23B in FIG. It is pressed to the left and contacts the surface of the photoreceptor belt 14.

Accordingly, since the latent image of the Y image is formed on the photosensitive belt 14 first, the developing roller 23Y is first brought into contact with the photosensitive belt 14 at a predetermined timing shown in FIG. The Y image is visualized (positive toner image).

On the other hand, the transfer paper P is faster than the linear velocity Vp of the photoreceptor belt 14 in the direction of arrow C in FIG. 2 by the paper feed roller 37 which starts rotating at a predetermined timing shown in FIG. The paper is fed at a feeding speed (for example, 1.5 times the speed of Vp), and once stopped by a registration roller 38 (conveyance speed substantially the same as or slightly earlier than the linear speed Vp), the image is transferred to the image on the photosensitive belt 14. The sheet is conveyed at the same timing (k in FIG. 5), and before the transfer process, the entire surface is uniformly discharged by a charge eliminator 29, and is conveyed onto the transfer belt 17 that has been cleaned by a transfer belt cleaner 31. Is done.

The transfer paper P is conveyed at the same linear velocity Vf as the linear velocity Vp while being in close contact with the transfer belt 17 by the corona charge by the paper adsorption charger 27, and the leading end thereof is transferred at the transfer position Tp shown in FIG.
When the point reaches the point _RT that is a predetermined distance l ₁ earlier than the point R, the tip of the Y image visualized by the developing device 24Y is moved to the transfer position T.
A point Ts that is a predetermined distance l ₂ equal to the predetermined distance l ₁ before p
, A forward rotation start signal S ₁ (d in FIG. 5) of the transfer drive motor is output. At this time, the transfer drive motor 44 is already rotating forward (see e in FIG. 5). Therefore, the normal rotation is continued as it is.

Incidentally, when the forward start signals S ₁ of the transfer drive motor is output, as in this embodiment is shown in d of FIG. 5, PC driven roller 13 from the write start timing based on the Y image data is 4 rotates (The rotation detection sensor 59 outputs four pulses), and after the PC drive motor 13 makes four rotations, the pulse from the encoder 54 becomes a predetermined pulse number P ₀ (the pulse waveform is not shown in FIG. 5). It is when the rotation position is reached.

When the time t ₁ elapses from the output of the forward rotation start signal S _{1, the} leading end of the Y image on the photosensitive belt 14 and the transfer paper P
Are moved by the predetermined distances l ₂ and l ₁ (FIG. 1) to reach the transfer position Tp, where the transfer of the Y image has already started when the normal rotation start signal S ₁ has been output. corona
26, the Y image is transferred to the transfer paper P.

The transfer paper P on which the Y image has been transferred is transferred to a paper separating charger 28.
, And is separated from the transfer belt 17 and advances on the paper leading end guide plate 41 through the switching claw 39 at the rotation position shown by the solid line in FIG.

Then, when the time t ₁ + t ₂ elapses after the forward rotation start signal S _{1 of} the transfer drive motor is output, the rear end of the transfer paper P passes the transfer position Tp by the distance l ₃ as shown in FIG. (The transfer paper moves by a distance of l ₁ + lp “lp is the length of the transfer paper P in the transport direction” + l ₂ from the time when the signal S ₁ is output), and the transfer paper P indicated by a virtual line in FIG. reached _one of the positions where the transfer drive motor 44 to reverse direction and click worship returns at (e of FIG. 5) higher linear speed Vr than the linear velocity Vf of normal rotation of the arrow F ₂ direction.

Prior to the reverse rotation of the transfer drive motor 44, the contact / separation switching roller 32 is moved downward to separate the transfer belt 17 from the surface of the photosensitive belt 14 in advance.

Then, during a short return time t ₃ by fast linear velocity Vr, the distance equal to the distance traveled to the left between the transfer sheet P of time t ₁ + t ₂ described above, back to the right in Figure 2.

At the time of this return, the transfer paper P has its right end (the leading end in the advancing direction) separated from the transfer belt 17 and travels above the paper rear end guide plate 33, and the left end of the transfer paper has a point R _T (first
It stopped at a position of the transfer sheet P ₂ shown in phantom in FIG. 2 to reach the drawing), and waits in preparation for transfer of the second color magenta image (hereinafter referred to as M image).

On the photoreceptor belt 14, the formation (writing) of the M image of the second color has already been performed during the transfer of the Y image of the first color, as shown by c and l in FIG. That is, the formation of the electrostatic latent image by writing on the photoreceptor belt 14 by irradiating the laser beam based on the M image data starts from the start of writing the Y image.
The process starts when the PC drive roller 13 has rotated an integer (in this example, the fourth rotation).

The developing roller 23M of the developing device 24M is a photosensitive belt.
Before the end of the M image area reaches after the Y image area formed on the image sensor 14 reaches the front end of the M image area, the latent image area of the M image is visualized by contacting the photoreceptor belt 14 and the cyan of the next third color is formed. Before the image (C image) area arrives, it is separated from the photosensitive belt 14.

When the leading end of the M image reaches the Ts point, the PC drive roller 13 rotates four times from the start of writing the M image data as in the case of the Y image of the first color, and the encoder after the PC drive motor 13 has further rotated four times. The number of pulses from 54 is the prescribed number of pulses
When the rotational position reaches P ₀ ′ (the pulse waveform is not shown in FIG. 5), a forward rotation start signal S ₂ of the transfer drive motor is output.

Simultaneously or slightly later, the contact / separation switching roller 32 is raised to bring the transfer belt 17 into contact with the photosensitive belt 14 at least until the leading end of the transfer paper P reaches the transfer position Tp.

Then, the time from the output timing of the signal S ₂ t ₁ '(Time
t ₁ and the photosensitive belt 14 by the same), when similarly to the transfer position M image tip moved by a predetermined distance l ₂ of the aforementioned Y image
Reach Tp.

Also, during the time t ₁ ′, the transfer paper P falls from the speed 0 state to Vf (= Vp) as shown in FIG. 5E, and the time t ₁ ′ elapses. Next, the control device 50 controls the position via a motor drive circuit (not shown) so that the number of pulses of the encoder 56 shown in FIG.

As a result, the leading end of the transfer paper P moves by ₁ during the time t ₁ ′, and the Y image of the first color and the M image of the second color are accurately aligned on the transfer paper P.

Thereafter, the same process as above is repeated, and the third color cyan image (C image) and the fourth color black image (B image)
Are sequentially transferred.

When the transfer process of the last B image comes, the switching claw 39
2 is switched to the position indicated by the imaginary line in FIG. 2, and the transfer paper P during the transfer process is conveyed to the fixing device 43 while being discharged by the paper separating charger 28, and is discharged onto the tray 45. .

By the way, in this embodiment, as described above, the manual paper detection sensor 35 detects the photosensitive belt 14 in the transport direction from the writing position Lp on the photosensitive belt 14 to the transfer position Tp of the transfer unit 25.
The distance l _LT along the photosensitive surface is substantially equal to the distance l _TS on the paper transport path from the transfer position Tp to the paper detection position Sp of the manual paper detection sensor 35.

Then, the rear end of the transfer paper P fed from the manual feed table 36 at the time of manual feed is moved to the paper detection position Sp shown in FIG.
, The control device 50 stops inputting the paper detection signal from the manual paper detection sensor 35 (the output from the sensor changes from “H” to “L”) as shown in FIG.
As a result, control is performed so that the writing by the laser light emission of the optical writing unit 18 is stopped (see c in FIG. 5).

Accordingly, the leading end of the image (visible image) written on the photoreceptor belt 14 and the leading end of the transfer paper P are positioned at the transfer position as described above.
Since the photosensitive belt 14 and the transfer belt 17 are conveyed at the same linear velocity Vp and Vf, the position of the image at the end of the image reaches the transfer position TP. Since there is always a transfer sheet P at the transfer position Tp, the visible image of the toner on the photoreceptor belt 14 is always transferred to the area of the transfer sheet (sub-scanning side), There is no transfer on 17

When forming a multi-color (overlap) image, the time from the start to the stop of writing is determined by the internal timer of the CPU of the control device 50, If the one-line synchronization detection output of the writing system is counted and stored, and the writing sub-scanning width for the second and subsequent colors is controlled by the count value, a multi-color image can be formed.

In addition, transfer paper of the minimum size used for manual feed
When the transfer paper is set on the manual feed table 36, the transfer paper is detected by the manual paper detection sensor 35, and when the position of the rear end of the transfer paper is Psen, the transfer paper on the transport path from the Psen to the transfer position Tp is set. The distance l _T sen needs to be set to be longer than the distance l _LT .

As described above, in this embodiment, the case has been described where optical writing is performed by irradiating (scanning) laser light with each color image data on which the formation of an electrostatic latent image of each color is digitally processed. Even if an analog optical image of a normal electrophotographic copying machine is formed at a predetermined timing in (FIG. 1), color recording can be similarly performed.

In the color recording apparatus according to this embodiment, if a connection interface with other devices such as a color facsimile, a word processor, and a personal computer is provided in advance, the image data output from each device can be used. Color recording can be performed.

〔The invention's effect〕

As described above, according to the present invention, the distance on the paper transport path from the manual paper detection sensor to the transfer position is substantially equal to the distance from the writing position to the transfer position on the photoreceptor. Even if the length of the transfer paper is fed, the image (visible image) on the photoreceptor is always transferred only in the transfer paper and not on the transfer belt. Disappears.

Accordingly, the load on the transfer belt cleaner is reduced, so that there is no cleaner failure, and there is no suction failure, so that the color shift of the superimposed image (at the time of color recording) can be reduced, and the back stain on the transfer paper is almost eliminated.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a main part of a color recording device as an image forming apparatus according to the present invention and its periphery, FIG. 2 is an overall configuration diagram showing the entire color recording device of FIG. 1, and FIG. FIG. 4 is a perspective view showing a drive system of the body belt 14 and the transfer belt 17, and FIG. 4 is a detection circuit to which a manual paper detection sensor 35 is connected.
FIG. 5 is a timing diagram showing the operation timing of only the main part of the color recording apparatus shown in FIG. 2, and FIGS. 6 and 7 are diagrams each using a conventional digital copying machine and a transfer belt. 1 is a schematic configuration diagram illustrating an example of a copying machine in which the present invention is applied. 14 photoreceptor belt, 17 transfer belt 18 optical writing unit (electrostatic latent image forming means) 19 charger (charging means) 24Y, 24M, 24C, 24B developing device (developing means) 25 transfer section, 35 manual feed paper detection sensor 36 manual feed table 50 control device (electrostatic latent image formation stop control means) P transfer paper

Claims (1)

(57) [Claims] A photoreceptor that is rotated by being charged by a charging means; an electrostatic latent image forming means for irradiating the photoreceptor with laser light at a predetermined writing position to form an electrostatic latent image; Developing means for developing the electrostatic latent image to make it visible, a transfer belt for conveying the transfer paper to a transfer position for transferring the visible image to transfer paper, and a paper feeder for manually feeding the transfer paper An image forming apparatus having a manual feed table, wherein a manual feed paper detection sensor for detecting the presence or absence of transfer paper set on the manual feed table is provided on a paper transport path from the paper detection position of the sensor to the transfer position. And when the distance from the writing position to the transfer position along the photosensitive surface of the photoreceptor is substantially equal, and the transfer paper is not detected after the manual paper detection sensor detects the transfer paper. The electrostatic latent image type An image forming apparatus characterized in that a latent electrostatic image formation stop control means for stopping the electrostatic latent image formed by the means.