JPH0815942A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to prevent the image shift by reducing the force of the recording material pushing on the recording material carrier when the recording material is adsorbed on the recording material carrier. A first guide part for guiding the recording material in the vicinity of the suction position, and a second guide part provided on the upstream side of the recording material supply path of the first guide part for guiding the recording material. The angle formed by the first guide portion with respect to the moving direction of the recording material carrier at the suction position is smaller than the angle formed by the second guide portion with respect to the moving direction of the recording material carrier.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As an apparatus for performing recording by the above method while conveying a recording medium such as a recording paper, generally, an apparatus having a configuration as described below is known (described by an electrophotographic method).

FIG. 10 shows an example thereof. The apparatus is roughly divided into an image input section 90R and an image output section 90P. The image input unit 90R is a device for inputting image information to be recorded, performing various kinds of processing, and then sending the image signal to the image output unit. The image output unit 90
P is an image forming unit 91 such as a photoconductor for forming a recording image in accordance with the above-mentioned signal, a recording sheet P is stacked, and 1
Plural sheet feeding units 92A, 92 for feeding sheets one by one
B, 92C, a pre-registration transport unit 97 including a pre-registration transport roller 97A for transporting the recording paper fed from the paper feed unit to the registration roller 96, and the function of the suction unit 99 for adhering the recording paper fed from the registration roller 96. The transfer drum 93 for transferring the image onto the recording paper while holding it on the surface by the transfer drum 93, 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
5 and.

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 either 92B or 92C
Is fed to the registration roller 96 by the pre-registration transport roller 97A. At this time, the roller 96 is stopped, and the leading edge of the recording paper is the roller 9
The pre-registration transport roller 97A continues the transport for a short period of time after it hits 6. Then, after the recording paper forms a predetermined loop (hereinafter, referred to as a pre-registration loop), the pre-registration transport roller 97A is stopped. After that, the registration roller 96 and the pre-registration transport roller 97A rotate in synchronization with the image recording start signal, and the recording paper P is transferred onto the transfer drum 93.
The image 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 unit 90R starts the operation based on the above signal, sequentially inputs the image information, converts the image information into an image signal for recording, and outputs the image signal to the image forming unit 91. Then, the image forming section 91 forms an image on the photoconductor in accordance with the signal by a process such as latent image formation and development.

The recording paper P is conveyed to the image transfer area T while being held on the transfer drum 93 by the action of the suction portion 99 such as the suction roller 99A, and the image formed by the image forming portion 91 is transferred and recorded on the surface thereof. . Here, as a method of holding the recording paper P on the transfer drum 93, electrostatic adsorption on a carrier medium made of a thin dielectric film 100 or the like is mainly considered. When recording is performed on the recording paper P, the transfer drum 93 conveys the recording paper P to the vicinity of the fixing unit 94,
The paper is fed to the unit 94 while separating the front end of the paper.
There, heat and / or pressure is applied to fix the toner image on the recording paper P, and then the recording paper P is discharged to the outside of the machine through the paper discharge unit.

Next, the structure of the general suction section 99 will be described in detail with reference to FIG. Registration roller 9
The recording paper P sent from 6 is sucked by the suction guides 99R, 9R.
It is guided between 9L and reaches the adsorption position. Here, in order to smoothly enter the suction position without fluttering the leading edge of the paper, it is better to make the distance between both guides as narrow as possible. At the suction position, a corona charger 99B is provided so as to face the suction roller 99A with the transport medium interposed therebetween.
9A is grounded. Then, a high voltage is applied to the charger 99B in synchronism with the timing when the recording paper P enters the adsorption position, whereby charges are generated on the recording paper P and the conveyance medium, and the paper is electrostatically adsorbed onto the medium.

In the case of the apparatus having the above structure, the peripheral speed of the registration roller 96 and the peripheral speed of the transfer drum 93 are usually set as described below. If the registration roller 96 is slower than the transfer drum 93, the recording paper P pulls 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. Alternatively, at worst, the drum 93 to the recording paper P
It is conceivable that it will come off. Therefore, in order to prevent this problem, the registration roller 96 is set to be slightly faster than the transfer drum 93 by design (a slight delay will always cause a problem in the image, but in the fast direction, there is a range that does not cause a problem to some extent. ), The registration roller 96 is prevented from becoming slower than the transfer drum 93 even if variations occur in the component accuracy.

[0008]

However, the above-mentioned device has the following problems.

Since the registration roller 96 is faster than the transfer drum 93, the paper P gradually begins to form a loop between the roller 96 and the drum 93 (hereinafter, referred to as a post-registration loop), and the paper P is drum 93. The force to press is generated and increases. Then, when the value exceeds a certain level, the drum speed fluctuates. This variation appears as expansion / contraction of the transferred image (this expansion / contraction direction is called the sub-scanning direction, and the image deviation due to this is called the sub-scanning deviation). Therefore, in order to avoid the problem, it is proposed to provide a mechanism for separating the registration roller 96 and freeing the paper P after a while after the front end of the paper P is held on the transfer drum 93. ing. This is because the registration roller 96 is separated before the post-registration loop generated by making the peripheral speed of the registration roller 96 faster than the peripheral speed of the transfer drum 93 (hereinafter 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 problems may occur.

The registration roller 96 has a function of correcting the paper P conveyed to the skewed roller P 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. By the way
If you cancel the cash register while the paper is sandwiched between
The absorbed force directly acts on the transfer drum 93. Then, the thin dielectric sheet film 100 easily loses its acting force and is likely to be dented or displaced. After that, the acting force gradually increases until the trailing edge of the paper passes through the pre-registration transport roller, and accordingly, the dent and the deviation also increase. Then, the moment the paper P comes out of the pre-registration transport roller 97A, the acting force becomes 0, so that the sheet 100 suddenly returns to the original state. Then, the image transferred during the change of the sheet 100 is distorted (main scanning misalignment). Further, there is a problem that the recording material P is displaced with respect to the sheet 100 during the change of the sheet 100. Registration roller 96
There is no problem if skewing does not occur before, but this is a very difficult problem, and in particular, the increase in the number of paper feed units that has become common in recent years makes the paper path to the registration roller 96 longer and complicated. As a result, it is becoming more difficult to prevent skew of the paper P. Further, it is conceivable to increase the pre-registration loop amount in order to reduce the use force to the transfer drum 93, but it is necessary to secure a wide loop forming space, which leads to an increase in size of the apparatus. In addition, if the transfer drum 93 is additionally rotated once after the paper P is adsorbed and then the image transfer is performed, the above-mentioned image shift does not occur, but the productivity of the apparatus is reduced accordingly.

[0011]

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

[0012]

According to the present invention for solving the above problems, an image is formed on a recording material carrier that carries and conveys a recording material, and the recording material carried on the recording material carrier. Image forming means, suction means for electrostatically adsorbing the recording material to the recording material carrier at the adsorption position of the recording material carrier, recording material supply means for supplying the recording material to the adsorption position, and the recording In an image forming apparatus having a guide unit that guides the recording material supplied by the material supply unit to the suction position, the guide unit includes a first guide unit that guides the recording material close to the suction position. A second guide provided on the upstream side of the recording material supply path of the first guide portion for guiding the recording material
And a second guide portion with respect to the moving direction of the recording material carrier, the angle formed by the first guide portion with respect to the moving direction of the recording material carrier at the suction position. It is characterized by being smaller than the angle formed by the parts.

[0013]

EXAMPLE An example of the present invention will be specifically described with reference to FIG. Hereinafter, the image forming method will be described as an electrophotographic method, and a color image output apparatus in which the present invention is considered to be particularly effective will be described.

In this example, the digital color image reader unit is provided on the upper side and the printer unit is provided on the lower side.

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

The printer unit has the following structure. A photosensitive drum 1 as an image carrier is axially supported at its center and is rotationally driven in the arrow direction by a motor (not shown). A pre-exposure lamp 11, a primary charger 2, an exposure optical system 3 such as a laser, a potential sensor 12, a developing device 4, a drum light amount detection means 13, and a recording unit that face the outer peripheral surface of the photosensitive drum 1 along the rotation direction thereof. A transfer drum 5 as a material carrier and a cleaning device 6 are sequentially arranged.

The pre-exposure lamp 11 and the primary charger 2 apply a uniform amount of charge to the surface of the photosensitive drum 1.
Then, the optical system 3 exposes a light beam E, such as a laser beam, which is modulated according to the recorded image signal, onto the photosensitive drum 1 via the polygon mirror 3A, the lens 3B, etc., thereby forming an electrostatic latent image there. Form. Further, the developing device 4 (in this device, yellow, cyan,
Four devices 4Y respectively accommodating four color developers such as magenta and black (hereinafter referred to as toner),
4C, 4M, and 4Bk are arranged side by side, and these are eccentric cams 24.
The electrostatic latent image is visualized by the operations of Y, 24C, 24M, and 24Bk so that the electrostatic latent image can be moved so as to selectively come close to the photosensitive drum 1.

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 left on the photosensitive drum 1 without being transferred to the recording material P. An image is formed with toner by the process described above.

The present apparatus has a three-stage cassette sheet feeding device (referred to as an upper stage, a middle stage, and a lower stage) and one manual sheet feeding device. Among these, the middle-stage paper feeding will be described (the upper and lower stages are almost the same as the middle stage, and the description thereof will be omitted).
The paper feeding unit 40 includes a cassette 41 for storing the recording paper P as a recording material, a pickup roller 42 for feeding the recording paper P one by one from the cassette 41, and a recording paper P fed from the pickup roller 42. Paper feed roller 4 for transporting to the transfer transport unit 50
3A, 43B, conveyance rollers 45A, 45B, 45C, and paper guides. The bypass tray is the bypass tray 4.
1T, paper feed roller 42M (and separation pad not shown)
And so on.

The transfer / conveyance unit 50 is roughly divided into a conveyance section 50A and the transfer drum 5. The transport unit 50A is shown in FIG.
It will be described based on. Guides 48A, 48B, 48C, 4 for inheriting the paper from the paper feeding unit 40 and guiding the paper
8D, 48E, and transport rollers 46A, 46B, 4
6C, pre-registration transport rollers 47A and 47B, and a pair of registration rollers 44 as recording material supply means for sending the recording paper P to the transfer drum 5 described later at the image forming timing of the image forming unit, and the paper at that time. It comprises suction guides 48F, 48G and the like as guide means for guiding P. Here, the transport rollers 46A, 46B, 46C have a curling function. The guides 48B and 48D have a curved shape (R in the drawing) for changing the traveling direction of the paper P, and are supported so as to be rockable in the arrow direction as shown in the drawing (hereinafter, these are rocking guides). Called). This is to secure the loop space of the paper P that occurs 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, which are pressed against each other by a spring (not shown).
Both ends of the rubber roller 44B are held in the elongated holes of the side plate 44C (front side is not shown) via bearings so as to be separated from the metal roller 44A. Further release cam 4
4D is fixed to the camshaft 44E, and the shaft 4
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 selectively rotates by 180 ° in cooperation with both (and a plunger (not shown)). You can then stop. Due to the rotation of the cam 44D, one end of the swing arm 44J is pushed and swings about the arm center shaft 44H. The other end of the arm 44J is located in the vicinity of both ends of the rubber roller 44B, and contacts the roller 44B by the above swing, displaces it against the pressure contact spring, and operates to separate from the metal roller 44A. In other words, according to the phase at which the cam 44D stops,
The rollers 44A and 44B are arranged so as to have a position where they are pressed against each other and a position where they are separated from each other (the upper part in the drawing represents the pressed contact and the lower part represents the separated position).

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

At the position where the recording paper P sent from the registration roller 44 enters the transfer drum 5, the suction roller 5G is supported so as to be separable from and in contact with the transfer drum 5, and is reversed with the transfer sheet 55S of the suction roller 5G sandwiched therebetween. A backup member and an electrostatic charger 5C for adsorbing against the pressing force of the roller 5G are arranged on the side. In the image transfer area where the photosensitive drum 1 and the transfer drum 5 face each other, the transfer charger 5B is arranged on the back side of the transfer sheet 55S. A separating member for separating the recording paper P, specifically, a discharging charger 5H, a separating claw 8A, a transfer sheet pushing roller 8B, and the like are provided downstream thereof, and subsequently, a transferring sheet discharging charger 5D, 5E are arranged so as to sandwich the sheet 55S. On the further downstream side, the seat 55
The brush roller 14 and the corona discharger or brush type static eliminator 15 for cleaning the toner and paper dust adhered to the recording paper holding surface of S, and the oil used in the fixing unit 9 are recorded during double-sided recording (described later). The transfer sheet 55S may be attached to the surface of the transfer sheet 55S through the paper P, and an oil removing roller 16 and a backup brush 17 for cleaning the transfer sheet 55S are provided.

Here, the transfer drum 5 is constructed so as to be capable of being brought into contact with and separated 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 and the photosensitive drum 1 from coming into contact with each other for a long time, and to prevent the recording paper P or the like from coming into contact with the photosensitive drum 1 and damaging the surface during the jam processing. . The transfer drum 5 and the photosensitive drum 1 have gear flanges 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 / conveyance unit 50 includes sliders 62A and 6A.
2B allows the main body to be pulled out to the front side. This is to make jam clearance or maintenance easier and more reliable.

The fixing unit 9 includes a fixing roller 9A internally provided with a heat source such as a halogen heater, a pressure roller 9B which is pressurized by the roller (this roller 9B may also have a heat source), and the above roller. A conveying belt 9C and an entrance guide 9D for guiding the recording paper P to the pair of nip portions, and a paper discharge roller 9 for further guiding the recording paper P discharged from the roller pair to the outside of the apparatus.
It consists of E and so on.

The present apparatus has a mechanism for automatically recording images on both sides of the recording paper P. It will be described next. A conveyance path switching guide 19 is provided immediately downstream of the fixing unit 9 so that, after fixing, either the paper path discharged outside the machine or the paper path for double-sided recording is automatically selected. . The double-sided recording paper path includes a conveyance vertical path 20, a reverse path 21A, and a reverse roller 21.
The recording paper P, which is composed of B, the intermediate tray 22 and the like, and which is once guided to the reversing path 21A, is retreated by the reversing of the reversing roller 21B, with the trailing end at the beginning when fed, and retreating in a direction opposite to the feeding direction. It is stored in the intermediate tray 22. After that, the 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 image forming process described above. Here, the guide portion 23 above the intermediate tray 22
The plurality of guides selectively move up and down according to the size of the recording paper to be stored. As a result, sheets of any size can be stored and stacked at the top of the intermediate tray 22.

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

Next, a description will be given according to the operation of the apparatus (a case where the sheet is fed from the middle sheet feeder will be described as an example).

When an image forming operation start signal is issued, the cam 71 first makes a half rotation, and accordingly the transfer drum 5 swings to move to the operating position, and the gears of the flange mesh with each other to synchronize with the photosensitive drum 1. Rotate. At the same time, the recording paper P is transferred 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 is wound around the transfer drum 5 when passing through the curling rollers 46A, 46B, and 46C. After that, the pre-registration transport rollers 47A and 47B and the paper guides 48A, 48B, 48C, 48D, and 48E are transported to the registration rollers 44 while changing the transport direction. 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 fixed time, the driving of the transport rollers 47A and 47B is stopped. Then, a loop is generated in the paper P in the meantime, but the space required for it is formed by the rocking of the rocking guides 48B and 48D (the paper is automatically spread by the waist of the paper [FIG. 2R]). In this apparatus, the pre-registration loop amount is set to 8 mm (this value represents the amount by which the paper P is further fed after the leading edge of the paper hits the registration roller 44). This is the resist 44
It is necessary to secure the paper feeding stability from the lower paper feeding, which has the possibility that the paper arrival timing to the set may vary most. After that, the registration roller 44 and the pre-registration transport rollers 47A and 47B start to rotate after a predetermined time based on the timing when the image forming unit starts forming an image. The rotation timing is set so that the paper P and the toner image on the photosensitive drum 1 are exactly coincident with each other in the image transfer area.

When the paper P plunges into and contacts the transfer drum 5,
Corona discharge from the adsorption charger 5C and the adsorption roller 5
It is electrostatically adsorbed on the transfer sheet film 55S by the action of G (the adsorption roller 5G is normally separated from the transfer drum 5 to reduce the load, and is brought into pressure contact with 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 conveyed to the image transfer area while being held on the paper P. Therefore, the toner image formed on the photosensitive drum 1 by the above-described process is transferred onto the surface thereof by the transfer charger 5B, and then the paper P is conveyed to the separation section. Here, since the image of one color is transferred at one time, the paper P is separated by the operation described later in the case of a monochromatic image, but in the case of forming a multicolor image, the separating operation is not performed and the transfer drum 5 is performed. While being held above, it makes one round and is conveyed again to the transfer area. Then, the next toner image is further transferred onto the previous image, and this process is repeated a necessary number of times (the brush roller 14 and the like are supported so as to be separable from and in contact with the surface of the transfer drum 5, and at least the above-mentioned large amount is used. They are separated during the transfer process).

When this is completed, the paper P and the transfer sheet film 55S are separated by the action of the discharging charger 5H in the separating section.
The suction force between them 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 conveyed to the fixing roller portion by the conveying belt 9C and accurately guided to the nip portion on the entrance guide 9D. Then, the heat of the roller 9A fixes the toner image on the surface of the paper. After that, the paper P is conveyed by the paper ejection roller 9E, and the paper P is ejected to the outside of the machine. Finally, the transfer drum 5 separates from the photosensitive drum 1 (withdrawal 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 is recorded and fixed is guided to the conveyance vertical path 20, and then the recording paper P is reversed by the reversing roller 21B via the reversing path 21A and is stored in the intermediate tray 22. . After stacking the required number of sheets, the single-sided recording paper P ′ is sent out from the intermediate tray 22 one by one by the pickup roller 25, and the paper feed roller 26A,
It is transported to the transport unit 50A by 26B or the like. After that, the image is recorded on the other surface of the recording paper P by going through the same process as described above. Finally, the switching guide 19 is not operated and the paper P is discharged to the outside of the machine.

Next, the structures of the resist portion and the suction portion will be described in more detail. FIG. 5 shows the configuration, and FIG. 6 shows an actual supply of recording paper.

The recording paper sent from the registration roller 44 is guided to the contact portion Q (that is, the suction position) between the suction roller 5G and the transfer drum 5 by the suction guide R48F and the suction guide L48G.

At this time, the recording paper sent from the registration roller 44 is a guide 48 as a second guide portion which is a part of the suction guide R48F and the suction guide L48G.
J is guided to 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).

The reason why β = 30 ° is as follows. If this angle is small, the force by which the paper after the registration loop presses the transfer sheet 55S acts almost as it is in the rotational direction of the transfer drum 5, so that the speed variation of the transfer drum 5 easily occurs. On the other hand, the larger the angle, the more the loop force is directed in the radial direction of the transfer drum 5, so that the influence on the rotation of the transfer drum 5 is reduced.
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 pushed.
The pressure contact 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 paper floating occurs. Therefore, as a result of investigating a range in which both problems do not occur by changing the angle, even if the recording material is a 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 has been found that a better operation is performed in the range of 25 ° to 35 °. Based on the above, this angle is set to 30 ° in this device.

Next, considering the state of the paper after the paper front end is absorbed,
It is bent at an angle of 30 ° before and after the suction position Q. Then, for example, the more rigid the paper, the more it cannot be bent sharply. Therefore, a space for gently bending the paper must be secured on the upstream side of the suction position.

Therefore, in this embodiment, the suction guide L48G is provided with a step, and the flexible member 48H (for example, a thin polyester sheet) as the first guide portion is attached to the tip thereof. Then, the guide 48H forms an angle α = 5 ° with respect to the moving direction b of the transfer drum 5 at the suction position.
It was made to become.

Here, in order to secure a space, the angle α is ideally 0 °, but if the angle α is too small, the transfer sheet 55S is bent due to the bending of the guide 48H.
It is not preferable because it may come into contact with.

On the contrary, within 10 °, 105 g /
It has been confirmed that even with a thick paper of m ² , a force enough to prevent the bending of the paper is not generated by the saho, and good paper transportability can be realized.

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

Here, the guide 48I should guide the recording paper without bending when the recording paper enters, and should be bent easily so as not to prevent the recording paper from being gently curved after adsorbing the leading end of the recording paper. Therefore, in this device, the guide 48H has a thickness of 0.2 mm and the guide 48I has a thickness of 0.1 m.
The film of m is used, 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 lowered by not providing the entire surface with respect to the direction of the rotation axis of the suction roller 5G but by providing a space.

Although the guide 48H is flexible in this embodiment, a member having high rigidity may be used.
It is not always necessary to provide I.

Further, in this embodiment, the tip of the guide 48H extends to a position where it contacts the suction roller 5G or not, and is located at a position of 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 the wavy or curled front end of the paper and guide it to the suction nip in a uniform state. Of course, it is ideal to extend to the nip, but if it is brought too close to the transfer sheet 55S, the surface of the guide 48H may be contaminated by scattered toner, and the contamination may adhere to the surface of the paper. So, in this device, the above configuration is
They are as close to each other as possible without causing stains. However, it was confirmed that if the thickness is 8 mm or less, it is possible to guide the paper to the nip while the fluttering of the paper is sufficiently suppressed.

In this embodiment, the flexible guide 48H and the suction roller 5G have a gap of 0 to 0.5 mm. However, the present invention is not limited to this, and there is no problem in positively contacting the sheet as long as it does not adversely affect the paper conveyance.
As a result, the paper is further flattened, and more uniform suction is possible. At this time, if the guide 48H is composed of a member having high rigidity, a problem such as abrasion due to friction of the suction roller 5G occurs, so that the suction roller 5G
When the guide 48H is brought into contact with the guide 48H, the guide 48H is preferably flexible.

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

Since the paper can be guided in a plane until just before the suction nip, good suction without wrinkling or curling of the paper on the transfer sheet 55S can be realized, resulting in transfer. Good image transfer without omission is performed.

Further, since the loop after registration is formed gently, the force of the paper pressing the transfer drum 5 is also reduced, and as a result,
A high-quality image with almost no sub-scan misalignment can be obtained. If you cancel the registration to improve the sub-scan misalignment,
The main scanning misalignment, which is considered to be the adverse effect, is suppressed as much as possible due to the expansion of the post-registration loop space.

In addition, it is possible to avoid image shift without enlarging the pre-registration loop space, and as a result, it is possible to prevent the apparatus from becoming large. Further, since it is not necessary to rotate the transfer drum 5 extra to prevent the deviation, the device speed is not reduced.

[Other Embodiments] When corrugation occurs on the recording paper in a high humidity environment, transfer omission may occur. Therefore, the present invention was developed and a device was devised to solve the problem. This will be described below.

First, the cause of occurrence of the above-mentioned transfer omission will be described. Rippling of paper under normal high humidity occurs when the circumference of the paper stretches as compared with the central portion. This is because it absorbs moisture from the edges of the paper (Fig. 9a). When the paper is attracted to such a paper while the tip of the paper is stretched linearly as in the previous embodiment, since the central portion is not as stretched as the tip, the adsorption proceeds in a fan shape. After that, since the paper stretches again near the trailing edge of the paper, a paper surplus occurs, and the paper floats from the transfer sheet 55S around the central portion of the recording paper in the direction orthogonal to the feeding direction of the recording material, resulting in transfer omission. (Fig. 9b). Considering the above points, the following configuration was implemented.

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 R48F, and one end of the guide is flexible guide 48.
The guide 48H is bent in the direction of the transfer drum 5 by about 1 to 1.5 mm in contact with the vicinity of the front end of H. Others are the same as in the previous embodiment.

The operation will be described. Registration roller 4
The center of the paper P sent from 4 is a guide 48H, 4
In order to follow 8K, it enters the suction nip in the shape of the chain double-dashed line in FIG. Then, the approach path length is longer in the center part than the end part (because the end part follows the shortest course, the center part wraps around).
The center reaches the nip later than the end. Then, the front end of the paper is attracted in the shape of a bow as shown in FIG. Then, the paper is stretched even in the stretched portion near the rear end, and the suction is performed with almost no paper remainder. That is, it is possible to obtain a good transferred image as a result, without causing the paper floating to the extent that occurs due to transfer omission. Further, even paper without waviness can be adsorbed without any problem.

In the present embodiment, the guide 48K is configured to bend the planar guide 48H, but the basis weight is 6
It was confirmed that even thin paper of about 4 g / m ² could be conveyed between them without any problem. However, when paper with lower rigidity is used, the pressure contact force of both may affect the paper transport (it acts as the paper transport load, and the paper may skew or stop. Etc.). Therefore, if you need to avoid this problem, Guide 4
The central portion of 8H may be bent in advance.
Specifically, it can be easily realized by denting the central portion of the surface of the guide 48G to which 48H is attached.

Up to now, the laser has been described as the light source of the exposure apparatus, but the present invention is not limited to the halogen lamp and the L lamp.
The same effect can be obtained with anything such as an ED. Further, the recording material carrier is not limited to the drum-shaped one, and a belt-shaped structure wound around a plurality of rollers is also applicable.
Further, the image forming means is not limited to the electrophotography, but may be any device such as a thermal transfer system, as long as it requires a recording paper transport mechanism.

[0058]

As described above, in the present invention, the guide means for guiding the recording material supplied by the recording material supply means to the suction position is the first guide for guiding the recording material in the vicinity of the suction position. And a second guide portion provided on the upstream side of the recording material supply path of the first guide portion and guiding the recording material, and the first guide with respect to the moving direction of the recording material carrier at the suction position. Since 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, a space where the recording material forms a loop is formed between the recording material supply means and the suction position. It became possible to provide. Therefore, it is possible to reduce the pressing force of the recording material on the recording material carrier, and it is possible to form a high-quality image on the recording material without image shift.

[Brief description of drawings]

FIG. 1 is a structural cross-sectional view of an apparatus embodying the present invention.

FIG. 2 is a configuration cross-sectional view showing a transport unit of the present invention.

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

FIG. 4 is a perspective view showing a registration roller releasing 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 cross-sectional view showing a suction guide shape in the second embodiment.

FIG. 8 is a perspective view showing a suction guide shape in the second embodiment.

FIG. 9 is an explanatory diagram showing a state of suction of paper under high humidity.

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

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

FIG. 12 is an explanatory diagram showing a state of recording paper when register release is performed in the conventional apparatus.

[Explanation of symbols]

 1 Photosensitive Drum 5 Transfer Drum 5C Adsorption Charger 5G Adsorption Roller 44, 44A, 44B Registration Roller 47A, 48B Pre-Registration Conveying Roller 48A-48E Paper Guide 48F-48K Adsorption Guide 50 Transfer Conveying Unit P Recording Paper Q Adsorption Position T Transfer Part

Claims (17)

[Claims] 1. A recording material carrier for carrying and conveying a recording material,
Image forming means for forming an image on the recording material carried on the recording material carrier, and adsorption means for electrostatically adsorbing the recording material on the recording material carrier at the adsorption position of the recording material carrier,
An image forming apparatus comprising: a recording material supply unit that supplies a recording material to the suction position; and a guide unit that guides the recording material supplied by the recording material supply unit to the suction position. A first guide portion that guides the recording material in the vicinity of the suction position; and a second guide portion that is provided on the upstream side of the recording material supply path of the first guide portion and that guides the recording material, The angle formed by the first guide portion with respect to the moving direction of the recording material carrier at the suction position is smaller than the angle formed by the second guide portion with respect to the moving direction of the recording material carrier. An image forming apparatus characterized by. 2. 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 image forming apparatus according to claim 1, wherein the angle is 10 ° or less. 3. The image according to claim 1, wherein the first guide portion is close to the suction position within 8 mm upstream from the suction position in the moving direction of the recording material carrier. Forming equipment. 4. The suction means comprises a suction rotating body on the recording material carrying side of the recording material carrying body, and the recording material is passed between the suction rotating body and the recording material carrying body. The image forming apparatus according to claim 1. 5. The image forming apparatus according to claim 4, wherein the first guide portion is in contact with the suction rotating body. 6. The image forming apparatus according to claim 1, wherein the first guide portion has a flexible sheet. 7. The angle formed by the second guide portion with respect to the moving direction of the recording material carrier at the suction position is:
The image forming apparatus according to claim 1, wherein the image forming apparatus has an angle of 20 ° to 40 °. 8. The third guiding means projects from the second guiding portion toward the suction position to guide the recording material.
The image forming apparatus according to claim 1, further comprising: 9. The first guide portion includes a flexible sheet, and the third guide portion is formed of a flexible sheet having a rigidity lower than that of the flexible sheet included in the first guide portion. The image forming apparatus according to claim 8, wherein: 10. The recording material supply means supplies the recording material so that the recording material is adsorbed to the recording material carrier while forming a loop between the adsorption position and the recording material supply means. The image forming apparatus according to any one of claims 1 to 9, wherein 11. The recording material supply unit includes a rotating body that nips and conveys the recording material, and after the recording material carrying body holds at least the leading end of the recording material, the nipping of the recording material by the rotating body is released. The image forming apparatus according to claim 1, wherein: 12. The image according to claim 1, wherein the first guide portion and the second guide portion are provided between a recording material supply path and the recording material carrier. Forming equipment. 13. The guide member guides the recording material so that the end portion of the recording material in the direction orthogonal to the recording material supply direction reaches the suction position earlier than the center. The image forming apparatus according to claim 12. 14. The image forming apparatus according to claim 14, wherein the guide unit includes a pressing unit that presses a central portion of the recording material in a direction orthogonal to the recording material supply direction. 15. The image forming means transfers an image of the image carrier onto a recording material carried on the recording material carrier in an image carrier carrying an image and a transfer portion of the image carrier. 15. The image forming apparatus according to claim 1, further comprising a transfer unit. 16. The image forming apparatus according to claim 15, wherein the recording material carried on the recording material carrier is transferred by the transfer means so that the images on the image carrier are sequentially superposed. 17. The image forming apparatus according to claim 1, wherein the image forming unit sequentially forms images of a plurality of colors on the recording material carried by the recording material carrying body in an overlapping manner. .