JP3176221B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus using an electrophotographic system, for example, an image forming apparatus such as a printer, a facsimile, a copying machine, and more particularly to a multiple image forming apparatus.

[0002]

2. Description of the Related Art An apparatus which performs recording by the above-described method while transporting a recording medium such as recording paper is generally known to have the following configuration (described in an electrophotographic method).

FIG. 10 shows an example. The device is roughly divided into an image input unit 90R and an image output unit 90P. The image input unit 90R is a device for inputting image information for recording, performing various processes, and transmitting the image signal to the image output unit. The image output unit 90
In P, an image forming unit 91 such as a photoconductor for forming a recording image in accordance with the signal, a recording paper P is stacked, and
Plural paper feed units 92A and 92 for feeding out sheets one by one
B, 92C, a pre-registration conveyance section 97 including a pre-registration conveyance roller 97A for conveying the recording paper sent from the paper feeding unit to the registration roller 96, and the recording paper sent from the registration roller 96 acting as a suction section 99. The transfer drum 93 for transferring the image onto the recording paper while transferring it to the image forming section while holding it on the surface thereof, the fixing unit 94 for fixing the image recorded on the recording paper, and all the operations in these devices. Control unit 9 for controlling
And 5.

Next, the recording operation will be described in detail step by step. When the operation of the apparatus is started, first, the paper feeding unit 92A,
Recording paper P as a recording material from one of 92B and 92C
Is fed to the registration roller 96 by the pre-registration conveyance roller 97A. At this time, the roller 96 is stopped, and the leading end of the recording paper is
The conveyance roller 97 </ b> A before registration continues conveyance for a short period of time after the collision with No. 6. Then, after the recording paper forms a predetermined loop (hereinafter, referred to as a pre-registration loop), the pre-registration transport roller 97A stops. Thereafter, the registration roller 96 and the pre-registration conveyance roller 97A rotate in synchronization with the image recording start signal, and transfer the recording paper P to the transfer drum 93.
The sheet is sent upward (an image can be formed at a predetermined position on the recording paper P by this operation). On the other hand, the image input section 90R starts the operation based on the above-mentioned signal, sequentially inputs image information, and outputs the image information to the image forming section 91 while converting the image information into an image signal for recording. The image forming section 91 forms an image on the photoconductor by processes such as latent image formation and development in response to the signal.

The recording paper P is transported to the image transfer area T while being held on the transfer drum 93 by the action of the suction unit 99 such as the suction roller 99A, and the image formed by the image forming unit 91 is transferred and recorded on the surface thereof. . Here, as a method of holding the recording paper P on the transfer drum 93, it is conceivable that electrostatic adsorption onto a transport medium made of a thin dielectric film 100 or the like is mainly used. When recording on the recording paper P is performed, the transfer drum 93 conveys the recording paper P to the vicinity of the fixing unit 94, and
The paper is fed to the unit 94 while separating the leading end of the paper.
Then, heat and / or pressure is applied to fix the toner image on the recording paper P, and thereafter, the recording paper P is discharged outside the apparatus via a paper discharge unit.

Next, the structure of a general suction unit 99 will be described in detail with reference to FIG. Registration roller 9
The recording paper P sent out from the suction guides 99R, 9
It is guided between 9L and reaches the suction position. Here, it is better to make the space between the guides as narrow as possible in order to smoothly enter the suction position without the leading edge of the paper fluttering. At the suction position, a corona charger 99B is provided opposite to the suction roller 99A with the conveyance medium interposed therebetween.
9A is grounded. Then, a high voltage is applied to the charger 99B in synchronization with the timing at which the recording paper P enters the suction position, whereby charges are generated on the recording paper P and the transport medium, and the paper is electrostatically attracted to the medium.

In the case of the above-described apparatus, the peripheral speed of the registration roller 96 and the peripheral speed of the transfer drum 93 are generally set to have the following relationship. If the registration roller 96 is slower than the transfer drum 93, the recording paper P is pulled on the transfer drum 93 after the recording paper P is held on the transfer drum 93, and the speed of the transfer drum 93 fluctuates. Or, in the worst case, the recording paper P
It is also conceivable that it may come off. Therefore, in order to prevent this problem, the registration roller 96 is set to be slightly faster than the transfer drum 93 in design. (A little slower always causes a problem on the image, but there is a range that does not cause a problem in the fast direction to some extent. 3.) Even if there is a variation in component accuracy, the registration roller 96 is not slowed down more than the transfer drum 93.

[0008]

However, the above-described apparatus has the following problems.

Since the registration roller 96 is faster than the transfer drum 93, the paper P gradually starts forming a loop between the roller 96 and the drum 93 (hereinafter, this is referred to as a post-registration loop). Pressing force is generated and increases. If it exceeds a certain level, the drum speed will fluctuate. This fluctuation appears as expansion and contraction of the transferred image (the direction of expansion and contraction is called the sub-scanning direction, and the resulting image shift is called the sub-scan shift). Therefore, in order to avoid the problem, it has been proposed to provide a mechanism for freeing the paper P by separating the registration roller 96 some time after the leading end of the paper P is held on the transfer drum 93. ing. This is because the post-registration loop generated by setting the peripheral speed of the registration roller 96 higher than the peripheral speed of the transfer drum 93 separates the registration roller 96 before pressing the drum 93 (hereinafter, this is referred to as registration release). ) To widen the loop space and reduce the force of the paper P due to the loop (FIG. 12). However, in this case, the following problem may occur.

The registration roller 96 has a function of correcting the paper P conveyed to the skew in a normal direction even if the paper P is skewed. More specifically, the force acting in the axial direction of the roller 96 (hereinafter referred to as the main scanning direction) due to the skew of the paper P upstream of the registration roller 96 is absorbed by the pre-registration loop and reaches the transfer drum 93. Has no effect. However, if the transport roller 97A before the cash register
If you cancel the cashier while the paper is sandwiched between
The absorbed force acts directly on the transfer drum 93. Then, the thin dielectric sheet film 100 loses its acting force, and dents and deviations are likely to occur. Thereafter, the above-described acting force gradually increases until the trailing edge of the paper passes through the pre-registration conveying roller, and accordingly, dents and deviations also increase. Then, at the moment when the paper P comes out of the pre-registration conveying roller 97A, the acting force becomes 0, so that the sheet 100 suddenly returns to the original state. Then, the image transferred during the movement of the sheet 100 is distorted (main scanning deviation). There is also a problem that the recording material P is shifted with respect to the sheet 100 while the sheet 100 fluctuates. Registration roller 96
There is no problem if skew does not occur before, but this is a very difficult problem. Particularly, in recent years, a plurality of paper feed units has become common, and the paper path to the registration roller 96 has to be lengthened or complicated. Therefore, it is becoming more difficult to suppress the skew of the paper P. Further, it is conceivable to increase the loop amount before the registration in order to reduce the use force on the transfer drum 93, but it is necessary to secure a large loop forming space, which leads to an increase in the size of the apparatus. In addition, if the transfer of the image is performed after the transfer drum 93 is rotated once more after the paper P is attracted, the above-described image shift does not occur, but the productivity of the apparatus is reduced by that much.

[0011]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an apparatus which always maintains good image quality without deteriorating the stability of paper feeding of the apparatus.

[0012]

According to the present invention, there is provided a recording material carrier for carrying and transporting a recording material, and an image formed on the recording material carried by the recording material carrier. Image forming means, suction means for electrostatically adhering the recording material to the recording material carrier at a suction position, and conveyance force applying means for applying a conveyance force to the recording material for conveying the recording material to the suction position And a guide unit provided between the recording material conveyance path and the recording material carrier and guiding the recording material conveyed by the conveyance force application unit to the suction position, and the conveyance force application unit; In an image forming apparatus in which a loop is formed on a recording material between the suction position and the suction position, the guide unit includes a first guide unit provided in proximity to the suction position, A second guide portion provided upstream of the recording material conveyance path; A third guide that projects from the second guide in the direction of the suction position to guide the recording material, wherein the first guide is provided in the moving direction of the recording material carrier at the suction position. The angle formed by the portion is smaller than the angle formed by the second guide portion with respect to the moving direction of the recording material carrier.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described with reference to FIG. Hereinafter, an electrophotographic method is used as an image forming method, and a color image output apparatus in which the present invention is considered to be particularly effective will be described.

In this embodiment, a digital color image reader section is provided at an upper portion, and a printer section is provided at a lower portion.

In the reader section, the original 30 is placed on an original platen glass 31 and is exposed and scanned by an exposure lamp 32. The reflected light image from the original 30 is condensed on the full color sensor 34 by the lens 33 to obtain a color separation image signal. This signal passes through an amplifier circuit (not shown), is subjected to various processes in a video processing unit (not shown), and is sent to a printer unit.

The printer section has the following configuration. A photosensitive drum 1 as an image carrier is pivotally supported at its center, and is driven to rotate in a direction indicated by an arrow by a motor (not shown). A pre-exposure lamp 11, a primary charger 2, an exposure optical system 3 using a laser or the like, a potential sensor 12, a developing device 4, a drum light amount detecting means 13, facing the outer peripheral surface of the photosensitive drum 1 along its rotation direction. A transfer drum 5 as a material carrier and a cleaning device 6 are sequentially arranged.

In the pre-exposure lamp 11 and the primary charger 2, charges of a uniform charge amount are given to the surface of the photosensitive drum 1.
Next, the optical system 3 exposes a light beam E such as a laser beam modulated in accordance with a recording image signal onto the photosensitive drum 1 through a polygon mirror 3A, a lens 3B, and the like, thereby forming an electrostatic latent image thereon. Form. Further, the developing device 4 (in this device, yellow, cyan,
Four devices 4Y each containing a developer of four colors such as magenta and black (hereinafter referred to as toner),
4C, 4M, and 4Bk are provided side by side.
Y, 24C, 24M, and 24Bk are configured to be movable so as to be selectively approached to the photosensitive drum 1) to visualize the electrostatic latent image.

On the downstream side of the image transfer area, the cleaning device 6 cleans the surface of the photosensitive drum 1 by scraping off the toner remaining on the photosensitive drum 1 without being transferred to the recording material P. By the process described above, image formation with toner is performed.

This apparatus has a three-stage cassette paper feeder (referred to as upper, middle, and lower) and one manual paper feeder. Among them, the middle paper feed will be described (the upper and lower papers are almost the same as the middle paper, and the description is omitted).
The paper feeding unit 40 includes a cassette 41 for storing recording paper P as a recording material, a pickup roller 42 for feeding out the recording paper P one by one from the cassette 41, and a recording paper P sent from the pickup roller 42. Paper feed roller 4 for transporting to transfer / transfer unit 50
3A, 43B, transport rollers 45A, 45B, 45C and a paper guide. The manual feed section is the manual feed tray 4.
1T, paper feed roller 42M (and separation pad not shown)
Etc.

The transfer and transport unit 50 is roughly divided into a transport section 50A and a transfer drum 5. The transfer section 50A is shown in FIG.
It will be described based on. The transport unit 50A includes the sheet feeding unit 4
Guides 48A, 4 for guiding the paper inherited from 0
8B, 48C, 48D, 48E, and transport roller 4
6A, 46B, 46C, transport rollers 47A, 4 before registration
7B, a pair of registration rollers 44 as conveying force applying means for sending the recording paper P to a transfer drum 5 described later in accordance with the image forming timing of the image forming unit, and suction guides 48F and 48G for guiding the paper P at that time. Etc. Here, the transport rollers 46A, 46B, 46C have a curling function. The guides 48B and 48D have a curved shape (R in the figure) to change the traveling direction of the paper P, and are supported so as to be swingable in the direction of the arrow as shown in the figure (hereinafter, these are swing guides). ). This is to secure a loop space of the paper P generated when the leading end of the recording paper P is temporarily stopped by the registration roller 44.

A mechanism for releasing the pressure contact is added to the registration roller. FIG. 4 shows the configuration. In the figure, 44A is a metal roller and 44B is a rubber roller, both of which are pressed by a spring (not shown).
Both ends of the rubber roller 44B are held in long holes of a side plate 44C (a front side is not shown) via bearings so that the rubber roller 44B can be separated from the metal roller 44A. Further release cam 4
4D is fixed to the camshaft 44E,
A gear 44F and a spring clutch 44G for transmitting the drive from the main body to the shaft 44E are fixed to one end of 4E, and the cam 44D is selectively rotated by 180 ° by the cooperation of both (and a plunger not shown). Then you can stop. One end of the swing arm 44J is pushed by the rotation of the cam 44D, and swings about the arm center axis 44H. The other end of the arm 44J is located near both ends of the rubber roller 44B, and contacts the roller 44B by the above-mentioned swinging, displaces the roller 44B against the pressure contact spring, and operates to separate from the metal roller 44A. That is, in accordance with the phase at which the cam 44D stops,
The position where the rollers 44A and 44B are pressed against each other and the position where the rollers 44A and 44B are separated from each other are taken (the upper part in the figure represents the time of pressure contact and the lower part represents the time of separation).

The transfer drum 5 will be described with reference to FIG. Transfer sheet film 55S is attached to frame 55F in which annular members 55A at both ends are connected by connecting member 55B.
(For example, PET (polyethylene terephthalate) or PVdF (polyvinylidene fluoride) is used as the material), and the transfer drum 5 is formed by winding the material in a cylindrical shape.

A suction roller 5G is supported at a position where the recording paper P sent from the registration roller 44 enters the transfer drum 5 so as to be able to be separated from and contacted with the transfer drum 5, and the suction roller 5G is reversed with the transfer sheet 55S interposed therebetween. A backup member for opposing the pressing force of the roller 5G and a suction charger 5C are disposed on the side. In the image transfer area where the photosensitive drum 1 and the transfer drum 5 face each other, a transfer charger 5B is arranged on the back of the transfer sheet 55S. On the downstream side, a separating member for separating the recording paper P, specifically, a charge removing charger 5H, a separation claw 8A, a transfer sheet pushing roller 8B, and the like are provided, followed by a transfer sheet charge removing charger 5D. 5E is arranged with the sheet 55S interposed therebetween. Further downstream, the sheet 55
A brush roller 14 and a corona discharger or a brush type static eliminator 15 for cleaning toner and paper dust adhered to the recording paper holding surface of S, and oil used in the fixing unit 9 is recorded at the time of double-side recording (described later). The transfer sheet 55S may adhere to the surface of the transfer sheet 55S through the paper P, and is provided with an oil removal roller 16 and a backup brush 17 for cleaning the transfer sheet.

Here, the transfer drum 5 is configured to be detachable from the photosensitive drum 1, and is separated from the photosensitive drum 1 except during normal operation. This is to prevent the transfer drum 5 from contacting the photosensitive drum 1 for an excessively long time, and to prevent the recording paper P or the like from contacting the photosensitive drum 1 and damaging the surface thereof during jam processing. . The transfer drum 5 and the photosensitive drum 1 have a gear flange at one end thereof,
When the two drums come into contact with each other, this gear meshes with the photosensitive drum 1
Is transmitted to the transfer drum 5 side. Further, in the present apparatus, the transfer / conveying unit 50 includes the sliders 62A, 62A.
2B is configured to be able to be pulled out from the main body to the near side. This is to make jam clearing or maintenance more reliable and easier.

The fixing unit 9 includes a fixing roller 9A provided with a heat source such as a halogen heater therein, a pressing roller 9B pressed against the roller (the roller 9B may also be provided with a heat source), and the above-mentioned roller. A conveyance belt 9C and an entrance guide 9D for guiding the recording paper P to the nip portion of the pair, and a discharge roller 9 for further guiding the recording paper P discharged from the roller pair to the outside of the apparatus.
E, etc.

Here, the present apparatus has a mechanism for automatically recording images on both sides of the recording paper P. This is described below. A conveyance path switching guide 19 is provided immediately downstream of the fixing unit 9 so that, after fixing, one of a paper path discharged outside the apparatus and a paper path for double-sided recording is automatically selected. . The double-sided recording paper path includes a transport vertical path 20, a reverse path 21A, and a reverse roller 21.
B, the intermediate sheet 22 and the like, and the recording paper P once guided to the reversing path 21A is retreated by the reverse rotation of the reversing roller 21B, with the rear end at the time of being fed in the opposite direction to the fed direction, It is stored in the intermediate tray 22. Thereafter, paper is fed from the intermediate tray 22 again, and an image is formed on the other surface of the recording paper P by the above-described image forming process. Here, the guide portion 23 above the intermediate tray 22
Is designed such that a plurality of guides selectively move up and down according to the size of the recording paper to be stored. Thus, paper of any size can be stored and stacked at the top of the intermediate tray 22.

The control unit includes a control board, a motor drive board, and the like for controlling the operation of the mechanism in each unit.

Next, a description will be given in accordance with the operation of the apparatus (a case where paper is fed from a middle paper feeder will be described as an example).

When the image forming operation start signal is issued, first, the cam 71 rotates half a turn, whereby the transfer drum 5 swings and moves to the operating position. Rotate. At the same time, the recording paper P is removed from the cassette 41 by the pickup roller 42.
Are sent out one by one. And the paper feed roller 43A,
The paper P is guided between the paper feed guides by 43B and the transport rollers 45B and 45C, and is transported to the transport unit 50A. In the transport unit 50A, the paper P is first curled by a predetermined amount in the direction in which the paper P winds around the transfer drum 5 when passing through the curling rollers 46A, 46B, and 46C. Thereafter, the sheet is conveyed to the registration roller 44 while changing the conveyance direction by the action of the pre-registration conveyance rollers 47A, 47B and the paper guides 48A, 48B, 48C, 48D, 48E. At that time, the registration roller 44 is stopped, and the leading end of the paper P hits the nip portion of the registration roller 44. Then, after a certain period of time, the driving of the transport rollers 47A and 47B is stopped. Then, a loop is generated in the paper P during that time, but a space required for the loop is formed by the swing of the swing guides 48B and 48D (the sheet is automatically pushed out by the waist of the paper [FIG. 2R]). Here, in the present apparatus, the pre-registration loop amount is set to 8 mm (this value represents the amount of paper P that is further fed after the leading edge of the paper hits the registration roller 44). This is resist 44
This is necessary in order to secure the paper feeding stability from the lower sheet feeding where the timing of the paper reaching the copy unit may vary most. Thereafter, the registration roller 44 and the pre-registration transport rollers 47A and 47B start rotating after a certain period of time based on the timing at which the image forming unit starts forming an image. The rotation timing is set such that the paper P and the toner image on the photosensitive drum 1 exactly coincide in the image transfer area.

When the paper P enters and comes into contact with the transfer drum 5,
Corona discharge from suction charger 5C and suction roller 5
By the action of G, the transfer roller 5G is electrostatically attracted onto the transfer sheet film 55S (the suction roller 5G is normally separated from the transfer drum 5 to reduce the load, and is pressed against the transfer drum 5 only when the paper enters). The transfer drum 5 rotates in synchronization with the photosensitive drum 1, and the paper P is transported to the image transfer area while being held thereon. Then, after the toner image formed on the photosensitive drum 1 by the above-described process is transferred to the surface by the transfer charger 5B, the paper P is conveyed to the separation unit. Here, since one color image is transferred at one time, the paper P is separated by a later-described operation in the case of a single color image, but in the case of forming a multicolor image, the separation operation is not performed without performing the separation operation. The sheet is conveyed again to the transfer area after making one round while being held on the upper side. Then, the next toner image is further transferred onto the previous image, and this process is repeated a required number of times (the brush roller 14 and the like are supported so as to be able to be separated from and brought into contact with the surface of the transfer drum 5, and at least They are separated in the transfer process).

When the operation is completed, the paper P and the transfer sheet film 55S
The adsorbing force is reduced, and the paper P is separated from the transfer drum 5 by the subsequent operation of the separation claw or the like.

The paper P separated from the transfer drum 5 is transported to a fixing roller portion by a transport belt 9C, and is guided on an entrance guide 9D accurately to the nip portion. Then, the toner image is fixed on the paper surface by the heat of the roller 9A. Thereafter, the sheet P is conveyed by the sheet discharging roller 9E, and the sheet P is discharged outside the apparatus. Finally, the transfer drum 5 is separated from the photosensitive drum 1 (retreat position), and the apparatus stops.

Here, the case of double-sided recording will be described. When the switching guide 19 operates, the recording paper on which one side has been recorded and fixed is guided to the transport vertical path 20, and thereafter, the recording paper P is reversed by the reversing roller 21 B via the reversing path 21 A and stored in the intermediate tray 22. . Then, after the required number of sheets are stacked, the single-sided recording paper P 'is sent out one by one from the intermediate tray 22 by the pickup roller 25, and the sheet feeding roller 26A,
The sheet is conveyed to the conveying section 50A by 26B or the like. Thereafter, an image is recorded on the other surface of the recording paper P by performing the same steps as described above. Finally, the paper P is discharged out of the apparatus without operating the switching guide 19.

Next, the configuration of the resist section and the suction section will be described in more detail. FIG. 5 shows the configuration, and FIG. 6 shows how the actual recording paper is supplied.

The recording paper sent from the registration roller 44 is guided to a contact portion Q (that is, a suction position) between the suction roller 5G and the transfer drum 5 by a suction guide 48F and a suction guide 48G.

At this time, the recording paper sent from the registration roller 44 is the second recording paper which is a part of the suction guide 48G.
The guide 48J as a guide portion of the suction position Q at an angle β = 30 ° with respect to the moving direction b of the transfer drum 5 at the suction position (the common tangential direction b between the transfer drum 5 and the suction roller 5G at the suction position). Guided to.

Here, the reason for setting β = 30 ° is as follows. If this angle is small, the force of the paper in the post-registration loop pressing the transfer sheet 55S acts in the rotation direction of the transfer drum 5 almost as it is, so that the speed fluctuation of the transfer drum 5 tends to occur. On the other hand, as the angle increases, the above-described loop force moves in the radial direction of the transfer drum 5, so that the influence on the rotation of the transfer drum 5 decreases,
On the other hand, the transfer sheet 55S is pushed into the inside of the drum 5, whereby the suction roller 5G and the suction charger 5 are pressed.
The pressing force between C is reduced. As a result, the suction force of the paper is not sufficiently generated in the suction nip, and a problem such as floating of the paper occurs. Therefore, as a result of examining the range in which both problems do not occur by changing the angle, even if the recording material is thick paper having a basis weight of about 105 g / m ² , there is no practical problem in the range of 20 ° to 40 °,
It was found that a better operation was performed in the range of 25 ° to 35 °. Based on the above, this angle was set to 30 ° in the present apparatus.

Next, considering the state of the paper after the leading edge of the paper is adsorbed,
It curves at an angle of 30 ° before and after the suction position Q. Then, for example, the higher the rigidity of the paper, the more rapidly it cannot be curved. Therefore, a space for gently curving the paper must be secured upstream of the suction position.

For this reason, in the present embodiment, a step is provided in the suction guide 48G, and a flexible member 48H (for example, a thin polyester sheet) as a first guide portion is provided at the end thereof.
Was pasted. The angle of the guide 48H is set to α = 5 ° with respect to the moving direction b of the transfer drum 5 at the suction position.

Here, in order to secure a space, the angle α is ideally 0 °, but if this angle α is too small, the transfer sheet 55S
It is thought that it may come in contact with, which is not preferable.

Conversely, if it is within 10 °, 105 g /
Even with a thick paper of m ² , it was confirmed that a sufficient force to prevent the curling of the paper was not generated at the sabo, and good paper transportability could be realized.

Further, in this embodiment, a flexible member 48I (for example, a thin polyester sheet) as a third guide portion for projecting from the guide 48J in the suction position Q direction and guiding the recording paper is attached to the suction guide L48G. I have. The guide 481 is for guiding the recording paper conveyed from the registration roller 44 so that the leading end does not flutter.

Here, the guide 48I must guide the recording paper without bending when the recording paper enters, and should be easy to bend so as not to prevent the recording paper from gently bending after the leading end of the recording paper is attracted. Therefore, in the present apparatus, the thickness of the guide 48H is 0.2 mm, and the thickness of the guide 48I is 0.1 m.
m, and the rigidity of the guide 48I is lower than that of the guide 48H. In addition, guide 48I
The rigidity of the guide 48I may be reduced by providing an interval instead of providing the entire surface in the rotation axis direction of the suction roller 5G.

[0044] In this embodiment although the guide 48H and flexible, but it may also be used highly rigid member.

Further, in this embodiment, the tip of the guide 48H extends to a position where it comes into contact with the suction roller 5G or not, and is located about 5 mm upstream from the suction position Q in the moving direction of the transfer drum 5.

The reason why the guide 48H is extended to the vicinity of the suction position Q is to correct even if the paper tip is wavy or curled and to lead the paper to the suction nip in a uniform state. Naturally, it is ideal to extend the sheet to the nip. However, if the sheet is brought too close to the transfer sheet 55S, the surface of the guide 48H will be stained by the scattered toner, and the stain will adhere to the paper surface. Therefore, in the present apparatus,
It is as close as possible within the range where no contamination occurs. However, it was confirmed that when the thickness was 8 mm or less, the paper could be guided to the nip in a state where the fluttering was sufficiently suppressed.

In this embodiment, a gap of 0 to 0.5 mm is provided between the flexible guide 48H and the suction roller 5G. However, the present invention is not limited to this. For example, if there is no adverse effect on the paper conveyance, there is no problem even if the contact is positive.
As a result, the paper is further flattened, so that a more uniform suction can be achieved. At this time, if the guide 48H is made of a member having high rigidity, a problem such as scraping of the suction roller 5G due to friction occurs.
When the guide 48H is brought into contact with the guide 48H, the guide 48H is preferably flexible.

The above-described embodiment of the present invention has the following effects.

Since the paper can be planarly guided until immediately before the suction nip, even if the paper is wavy or curled, it is possible to realize good suction without floating the paper on the transfer sheet 55S. Good image transfer without omission is performed.

Further, since the loop is formed gently after the registration, the force with which the paper presses the transfer drum 5 is reduced, and as a result,
A high-quality image with almost no sub-scanning deviation can be obtained. When the registration is released to further improve the sub-scanning deviation,
The occurrence of the main scanning shift which is considered as an adverse effect is suppressed as much as possible because of the expansion of the loop space after the registration.

In addition, it is possible to avoid an image shift without enlarging the loop space before the register, and as a result, it is possible to prevent an increase in the size of the apparatus. Further, since it is not necessary to rotate the transfer drum 5 excessively to prevent the displacement, the speed of the apparatus is not reduced.

[Other Embodiments] When a recording paper is wavy in a high humidity environment, transfer omission may occur. Therefore, the present invention was developed, and a device that improved the problem was devised. This will be described below.

First, the cause of the occurrence of the transfer omission will be described. Normally, paper waving under high humidity occurs when the periphery of the paper stretches more than the center. This is to absorb moisture from the edge of the paper (FIG. 9a). When such paper is adsorbed while its leading end is straightened as in the previous embodiment, the adsorbing proceeds in a fan-like manner because the central portion is not as elongated as the leading end. Thereafter, the paper is stretched again in the vicinity of the rear end of the paper, so that excess paper is generated, and the paper floats from the transfer sheet 55S around the central portion of the recording paper in a direction orthogonal to the recording material supply direction, and as a result, transfer loss occurs. (FIG. 9b). The following configuration was implemented in consideration of the above points.

FIGS. 7 and 8 show changes from the previous embodiment. In the figure, a guide 48K as a pressing means having a small width is newly added. This guide is attached to the center of the suction guide 48F, and one end of the guide is attached to the flexible guide 48H.
, The guide 48H is bent by about 1 to 1.5 mm in the direction of the transfer drum 5. Others are the same as the previous embodiment.

The operation will be described. Registration roller 4
The center of the paper P sent out from No. 4 is a guide 48H,
In order to follow 8K, it enters the suction nip in the form as shown by the two-dot chain line in FIG. Then, the central part is slightly smaller than the end part, but the approach path length is longer (the end part follows the shortest course, but the center part is rounded),
The center reaches the nip later than the end. Then, the leading end of the paper is sucked in a bow shape as shown in FIG. 9C, and thereafter, the suction proceeds in the direction in which the paper spreads. Then, the paper is stretched even in the stretched portion near the rear end, and suction is performed with almost no excess paper. That is, a good transfer image can be obtained as a result, without causing the paper floating to occur due to the transfer omission. Further, even paper having no undulation is adsorbed without any problem.

In this embodiment, the guide 48K bends the planar guide 48H.
It was confirmed that even thin paper of about 4 g / m ² was conveyed without any problem. However, when using paper with even lower rigidity, it is conceivable that the press-contact force between the two influences the paper transport (this acts as a paper transport load and causes the paper to skew or stop. And so on). So if you need to avoid this problem,
The central portion of 8H may be bent in advance.
More specifically, the guide 48G can be easily realized by denting the center of the surface of the guide 48G to which the guide 48H is attached.

Although a laser has been described as the light source of the exposure apparatus, the present invention is not limited to this.
The effect is the same for any object such as ED. Further, the recording material carrier is not limited to the drum-shaped one, and may be applied to a belt-shaped configuration wound around a plurality of rollers.
Further, the image forming means is not limited to the electrophotography, and may be any device such as a thermal transfer system which requires a mechanism for conveying the recording paper.

[0058]

As described above, according to the present invention,
Since a space for forming a loop of the recording material gently can be provided between the conveying force applying means and the suction position, the force of the recording material pushing the recording material carrier can be reduced, and image displacement can be reduced. A high quality image can be formed on the recording material.

[Brief description of the drawings]

FIG. 1 is a configuration sectional view of an apparatus embodying the present invention.

FIG. 2 is a sectional view illustrating a configuration of a transport unit according to the present invention.

FIG. 3 is a configuration diagram illustrating a transfer drum of the present invention.

FIG. 4 is a perspective view showing a registration roller release mechanism according to the present invention.

FIG. 5 is an explanatory diagram showing a configuration of a suction unit in the first embodiment.

FIG. 6 is an explanatory diagram showing a state of recording paper in the first embodiment.

FIG. 7 is a sectional view illustrating a suction guide shape according to a second embodiment.

FIG. 8 is a perspective view illustrating a suction guide shape according to a second embodiment.

FIG. 9 is an explanatory diagram showing the state of adsorption of paper under high humidity.

FIG. 10 is a cross-sectional view illustrating a configuration of a conventional device.

FIG. 11 is an explanatory diagram illustrating a configuration of a suction unit of a conventional device.

FIG. 12 is an explanatory diagram showing a state of recording paper when registration is canceled in a conventional apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum 5 Transfer drum 5C Suction charger 5G Suction roller 44, 44A, 44B Registration roller 47A, 48B Pre-registration conveyance roller 48A-48E Paper guide 48F-48K Suction guide 50 Transfer conveyance unit P Recording paper Q Suction position T Transfer part

Claims (12)

(57) [Claims] A recording material carrier that carries and conveys the recording material;
Image forming means for forming an image on a recording material carried by the recording material carrier; suction means for electrostatically attracting the recording material to the recording material carrier at a suction position; and placing the recording material at the suction position. Conveying force applying means for applying a conveying force to the recording material for conveying, and a recording material provided between the recording material conveying path and the recording material carrier and conveyed by the conveying force applying means to the suction position. A guide unit for guiding, wherein a loop is formed on the recording material between the conveyance force applying unit and the suction position, wherein the guide unit is provided near the suction position. A first guide portion, a second guide portion provided upstream of the first guide portion on the recording material conveyance path, and the second guide portion.
Guides the recording material by projecting from
A third guide portion, wherein the angle formed by the first guide portion with respect to the moving direction of the recording material carrier at the suction position is the second angle with respect to the moving direction of the recording material carrier.
An image forming apparatus that is smaller than the angle formed by the guide section. 2. An angle formed by the first guide portion with respect to a moving direction of the recording material carrier at the suction position is 1
The image forming apparatus according to claim 1, wherein the angle is 0 ° or less. 3. The image forming apparatus according to claim 1, wherein the first guide portion is provided within 8 mm upstream of the suction position in the moving direction of the recording material carrier. 4. The suction means includes a suction rotating body on the recording material supporting side of the recording material carrier, and holds a recording material between the suction rotating body and the recording material carrier during suction. The image forming apparatus according to claim 1, wherein: 5. The image forming apparatus according to claim 4, wherein said first guide portion is in contact with said suction rotating body. 6. The image forming apparatus according to claim 1, wherein the first guide includes a flexible sheet. 7. An angle formed by the second guide portion with respect to a moving direction of the recording material carrier at the suction position is 2
The image forming apparatus according to claim 1, wherein the angle is 0 ° to 40 °. 8. The apparatus according to claim 1, wherein the first guide section includes a flexible sheet, and the third guide section is formed of a flexible sheet having lower rigidity than the flexible sheet. Item 8. The image forming apparatus according to any one of Items 1 to 7. 9. The recording medium according to claim 1, wherein the conveying force applying unit includes a rotating body for nipping and conveying the recording material, and releasing the recording material from being nipped by the rotating body after at least a leading end of the recording material is held by the recording material carrier. the image forming apparatus according to claim 1 to 8, characterized in. 10. The recording medium according to claim 1, wherein the guide unit guides the recording material such that an end portion of the recording material in the direction orthogonal to the recording material supply direction reaches the suction position earlier than a center portion. An image forming apparatus according to any one of 1 to 9 . 11. An image forming apparatus according to claim 10 , wherein said guide means has a pressing means for pressing said central portion. 12. The image forming unit, any of the image forming apparatus according to claim 1 to 11, characterized in that the successively overlaid form an image of the plurality of colors on the recording material carried on said recording material carrying member .