JP2002311728A - Image forming device - Google Patents

Abstract

(57) Abstract: In an image forming apparatus provided with a transfer nip portion at a position where a depression angle when viewing the transfer nip portion from the center of a photosensitive drum is in a range of 25 ° or more and 30 ° or less, A winding restriction means is provided upstream so that image dust can be prevented. An elastic winding control member is provided as winding control means for causing a transfer sheet to enter a transfer nip from a direction upstream of a transfer nip so that transfer paper does not wind around a transfer roller. As a result, before the transfer paper reaches the transfer nip, the back surface of the transfer paper passes while contacting the elastic winding restricting member. When the stiffness of the transfer paper is weak, the elastic winding restricting member pushes the transfer paper from the back surface, so that the transfer paper protrudes toward the image printing surface. Due to the tension, the transfer paper can be prevented from bending immediately before entering the transfer nip, and can enter the transfer nip with a stable behavior.

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 copying machine, a facsimile, a printer and the like, and more particularly, to a transfer material passing through an image transfer section on which an image on a drum-shaped latent image carrier is transferred. The present invention relates to an image forming apparatus in which a transport path is formed in a substantially vertical direction.

[0002]

2. Description of the Related Art In recent image forming apparatuses, there is a demand for a reduction in the size of the image forming apparatus and a reduction in the first print time. As an image forming apparatus known as an image forming apparatus capable of shortening the transfer path of a transfer material, there is a type in which a registration roller pair, a photoconductor transfer unit, and a fixing unit are arranged in a substantially vertical direction to vertically transfer the transfer material. .

FIG. 4 is a schematic configuration diagram of a conventional image forming apparatus for vertically conveying a transfer material. The electrostatic latent image formed on the photosensitive drum 1 as a drum-shaped latent image carrier is developed by a developing device, and is synchronized with a transfer material supplied from a pair of registration rollers 11 below the photosensitive drum 1. The sheet is conveyed to a transfer nip, and is transferred onto a transfer material by a transfer roller 10. Thereafter, the transfer material is further separated from the photosensitive drum 1 by a separation claw (not shown) and the charge removing device 22 while being further conveyed, and is conveyed to the fixing device 16 where the toner image is fixed, and is discharged from the device by the paper discharging device 18. You.

In such an image forming apparatus that vertically conveys a transfer material, the conveyance path of the transfer material is more likely to be unstable than in the case of horizontal conveyance, and the arrangement of the registration roller pair 11 and the photoconductor transfer unit is limited. Therefore, it is easy for the transfer material to wind around the transfer roller 10 just before entering the transfer portion. When the transfer material is wrapped around the transfer roller 10, the toner on the surface of the photoconductor jumps to the transfer material shortly before the transfer material reaches the regular transfer position, which causes a problem that image dust tends to occur.

Particularly, in an apparatus having a manual sheet feeding section for manual sheet feeding in addition to a main sheet feeding section in which a transfer material is set in the apparatus in advance, the arrangement of the registration roller pair 11 with respect to the transfer roller 10 is described. It has also been found that the transfer material tends to be conveyed in the direction in which the transfer material is wound around the transfer roller 10.

[0006] First, in an image forming apparatus for vertically transporting a transfer material, the present applicant has made it possible to enhance the separability of the transfer material discharged from the transfer portion from the photoreceptor and to prevent image dust. An arrangement of a photosensitive drum and a transfer roller has been proposed (see Japanese Patent Application No. 13-77802). This proposal is to reduce the depression angle when viewing the transfer nip portion, which is the contact position between the photosensitive drum and the transfer roller, from the center of the photosensitive drum 1 by 2 degrees.
The angle is set in the range of 5 ° to 30 °.

[0007]

However, even if the depression angle when viewing the transfer nip from the center of the photosensitive drum is limited within the above range, the type of paper used as the transfer material and the humidity control condition of the paper It was found that the effect of preventing image dust was not sufficiently obtained depending on various conditions such as the gap and the like. In addition, in the case of a transfer material having a weak waist, it was found that the transfer path of the transfer material becomes unstable, so that winding around the transfer roller in front of the transfer unit may not be completely prevented, and that image dust may easily occur. .

Therefore, in an image forming apparatus in which the depression angle from the center of a drum-shaped latent image carrier including a photosensitive drum to a transfer nip is set in a range of 25 ° to 30 °,
Further, it is required to prevent the occurrence of image dust.

The present invention has been made in view of the above problems, and has as its object to vertically transfer a transfer material.
When the transfer nip is viewed from the center of the latent image carrier, the depression angle is 2
An object of the present invention is to provide an image forming apparatus in which a transfer nip portion is set at a position within a range of 5 ° or more and 30 ° or less and which can prevent image dust.

[0010]

According to a first aspect of the present invention, there is provided an image forming apparatus, comprising: a drum-shaped latent image carrier; and an electrostatic latent image on the latent image carrier is converted into a toner image. Developing means, a transfer roller for forming a predetermined transfer nip on the surface of the latent image carrier, and transferring the toner image to a transfer material conveyed to the transfer nip, and transferring the transfer material below the transfer nip. And a transfer material transporting means for transporting the transfer nip so that the transfer nip passes upward in a substantially vertical direction, and a depression angle α when the transfer nip is viewed from the center of the latent image carrier is 25 ° ≦ α ≦ 30. In the image forming apparatus in which the position of the transfer nip is set so as to be within the range represented by °, the transfer material enters the transfer nip from a direction upstream of the transfer nip and not wound around the transfer roller. Characterized in that a winding restriction means is provided for

In the image forming apparatus according to the first aspect, the transfer material enters the transfer nip by the winding restriction means so that the transfer material is wound around the transfer roller on the upstream side of the transfer nip, that is, below the transfer nip. Restrict the route so that it does not stick. This prevents occurrence of image dust due to the transfer material being wound around the transfer roller upstream of the transfer nip.

According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the wrap restriction means is provided with:
It is characterized in that the transfer material is constituted by an elastic winding restriction member which is in contact with the surface of the transfer material facing the transfer roller on the upstream side of the transfer nip in the transfer material transport direction and has elasticity.

In the image forming apparatus according to the present invention, the transfer material is brought into contact with the latent image carrier upstream of the transfer nip by the elastic winding restricting member (hereinafter referred to as an image transfer surface).
Press As a result, the transfer material having no stiffness is curved toward the image transfer surface to provide tension, and stabilizes the behavior upstream of the transfer nip. In addition, the transfer material having a stiffness is prevented from being forcedly changed in the transport direction by the elastically wound restricting member being elastically deformed.

According to a third aspect of the present invention, in the image forming apparatus of the second aspect, a charge removing function for removing charge from the transfer material is added to the elastic winding regulating member.

In the image forming apparatus according to the third aspect, the transfer material is brought into contact with the elastic winding restriction member just before entering the transfer section, and the transfer material is neutralized by the neutralizing function of the elastic winding restriction member. As a result, a transfer material made of a material that is easily charged, such as OHP paper, or a transfer material that has been unexpectedly charged enters the transfer section in a non-charged state, thereby preventing the generation of image dust caused by the charging of the transfer material. I do.

According to a fourth aspect of the present invention, in the image forming apparatus of the third aspect, the elastic winding restriction member is made conductive.

In the image forming apparatus according to the present invention, the elastic winding restricting member is made conductive so as to have a static elimination function.

According to a fifth aspect of the present invention, there is provided the image forming apparatus according to the first aspect.
The image forming apparatus according to any one of 2, 3, or 4, wherein the diameter of the drum of the latent image carrier is 35 mm or less.

In the image forming apparatus of the present invention, the diameter of the drum of the latent image carrier (hereinafter referred to as the diameter of the latent image carrier) is set to 35 mm or less. The present inventors have found that it is difficult to separate the transfer paper from the latent image carrier when the diameter of the latent image carrier is larger than 35 mm. Therefore, the diameter of the latent image carrier is set to 35 mm or less to facilitate the separation of curvature, and the transfer material that has escaped from the transfer section can be automatically separated from the latent image carrier without a separating means. Note that the lower limit of the diameter of the latent image carrier only needs to be larger than 0, and in an actual apparatus, it may be appropriately determined according to various conditions that affect the determination of the diameter of the latent image carrier.

According to a sixth aspect of the present invention, there is provided the image forming apparatus according to the first aspect.
In the image forming apparatus of any one of 2, 3, 4 and 5, the linear speed of the latent image carrier is set to 120 mm / sec or less.

In the image forming apparatus of the present invention, the linear velocity of the drum surface of the latent image carrier (hereinafter, referred to as the linear velocity of the latent image carrier) is set to 120 mm / sec or less. According to the study of the present inventors, the linear velocity of the latent image carrier is 120 mm / s.
When it is larger than ec, it has been found that the transfer material may not be easily separated from the surface of the latent image carrier depending on the use environment of the apparatus and each condition of the transfer material. Therefore, the linear velocity of the latent image carrier is set to 120 mm / sec or less so that the transfer material that has escaped from the transfer section can be separated from the latent image carrier without being affected by the use environment of the apparatus or each condition of the transfer material. I do. still,
The lower limit of the linear velocity of the latent image carrier only needs to be larger than 0, and in an actual apparatus, the linear velocity of the latent image carrier may be appropriately determined according to various conditions that affect the determination of the linear velocity.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic laser printer (hereinafter simply referred to as a printer) as an image forming apparatus will be described below. The basic configuration of the printer will be described. FIG. 1 is a schematic configuration diagram showing the printer. In the figure, a printer 200 includes an image forming unit 100 including a photosensitive drum 1 as a latent image carrier, a charging roller 2, a developing unit 3 as a developing unit, a cleaning unit 4 for cleaning the photosensitive drum, and the like. I have.

On the side of the image forming unit 100,
An optical writing unit 6 for writing an electrostatic latent image on the photosensitive drum 1 is provided. For example, the optical writing unit 6 emits an optical signal corresponding to image information read by a scanner or the like from a semiconductor laser, scans the laser light with a polygon mirror that is driven to rotate, and scans the laser light. A device for writing an optical signal 6a corresponding to color-separated image information on a photosensitive drum through a lens for converging and correcting a surface tilt of a polygon mirror, a mirror for deflecting a laser beam, or the like provided in an optical path. Can be used.

Further, below the image forming unit 100, a paper feed roller 9 for separating and feeding the transfer paper 8 as a transfer material stored in the paper feed cassette 7 one by one, and this paper feed roller After the transfer paper 8 fed by the printer 9 is temporarily stopped before the photosensitive drum 1, the leading end of the image formed on the photosensitive drum 1 and the leading end of the transfer paper 8 are A registration roller pair 11 is provided as transfer material transporting means for re-feeding the transfer paper 8 in synchronization with the rotation of the photosensitive drum 1 at a timing when the nip reaches the nip portion with the transfer roller 10 almost simultaneously. .

Further, above the image forming unit 100, there are provided a fixing roller 14 and a press roller 15 having a built-in heater 13 rotatably disposed so as to be pressed against each other with a transfer path 12 for the transfer paper 8 therebetween. A fixing device 16 is provided as a fixing unit having the following. Downstream of the fixing device 16 in the transfer paper transport direction, the transfer paper 8 that has passed through the fixing nip of the fixing roller 14 and the press roller 15
A paper discharge roller 18 is provided for discharging the paper to a stacker 17 serving as a paper discharge tray formed on an upper part of a main body case 200a of the printer 200.

In the main body case 200a of the printer 200, there is provided an electrical unit 20 for controlling image forming means, print information and the like relating to the image forming process of the printer 200. The electrical unit 20 includes a control board (not shown) and various adjustment switches and control units mounted on the control board, and is arranged from the side of the optical writing unit 6 to below. It is housed in a metal electrical case 21.

In the printer 200 having such a configuration, first, the photosensitive drum 1 is uniformly charged by the charge from the charging roller 2 during rotation. Next, the optical writing unit 6 is driven based on image information read from the outside, whereby an electrostatic latent image is formed on the charged area (image forming area) of the photosensitive drum 1. This electrostatic latent image is
The toner image is developed by a developer (toner) supplied from the developing roller 3a of the developing unit 3 to be a visible image.

On the other hand, while the toner image is being formed on the photosensitive drum 1, the transfer paper 8 is pulled out of the paper feed cassette 7 by the paper feed roller 9, and the leading end thereof is nipped by the registration roller 11. Waiting in a state of contact with the part. The transfer paper 8 is sent out to a transfer nip T formed by the photosensitive drum 1 and the transfer roller 10 by the rotation of the registration roller 11 at the timing of being superimposed on the toner image on the photosensitive drum 1. It is. Then, after the toner image on the photosensitive drum 1 is transferred at the transfer nip T, the charge is removed by contact with the charge removing brush 22.

The separation claw 203 is in contact with the surface of the photosensitive drum 1 at a position slightly downstream of the transfer nip T in the transfer paper transport direction. After being mechanically separated from the photosensitive drum 1 by contacting the separation claw 203, the sheet is sent to the fixing device 16.

The fixing device 16 heats and pressurizes the transfer sheet 8 by sandwiching the transfer sheet 8 between the fixing roller 14 and the press roller 15, thereby forming a toner image on the transfer sheet 8.
Let it settle on top. The transfer paper 8 on which the toner image has been fixed in this way is discharged onto the stacker 17 by the discharge rollers 18.

Residual toner remaining on the surface of the photosensitive drum 1 after passing through the transfer nip T is removed from above the photosensitive drum 1 by the cleaning blade 4a of the cleaning unit 4 and collected in the cleaning container 4b. .

The main body case 200a of the printer 200 includes an opening / closing cover 201 serving as an opening / closing door forming a side surface of the transfer paper 8 on the side of the transport path 12, and a manual feed unit 23 for feeding the transfer paper 8 by manual feeding. Same spindle 202
Each is supported.

The transfer paper 8 supplied to the transport path by the manual feed unit 23 is transported to the registration roller 11 by rotation of a manual paper feed roller 24 provided on the printer main body 200 side. In this printer, a transfer paper transport path passing through a nip, a transfer nip T, and a fixing nip formed by the registration roller pair 11 is transported in a substantially vertical direction from below to above.
By vertically transporting the transfer paper 8 in this manner, downsizing and shortening of the first print time can be realized.

By the way, transfer paper 8 like this printer is used.
, The transport path of the transfer paper 8 tends to be unstable. In addition to this, manual feed unit 2
The registration roller pair 11 and the transfer nip T
Is limited, and the transfer paper 8 tends to wind around the transfer roller 10 just before entering the transfer section. For this reason, there is a problem that image dust easily occurs. In addition, since the present embodiment is effective for preventing image dust, the depression angle when the transfer nip T is viewed from the center of the photosensitive drum 1 is 25 in this embodiment as conventionally proposed.
The position of the transfer nip T, which is the nip portion between the transfer roller 10 and the photosensitive drum, is set at a position within the range of not less than 30 ° and not more than 30 °.

FIG. 2 is a partially enlarged view of a printer showing a characteristic portion of the present embodiment. Even if the depression angle α is set in the range of 25 ° or more and 30 ° or less, image dust may occur depending on the conditions of the apparatus. In order to prevent such image dust, the printer is provided with a mechanism for causing the transfer paper 8 to enter the transfer nip T from a direction such that the transfer paper 8 does not wind around the transfer roller 10 upstream of the transfer nip T in the transfer paper transport direction. A member is provided as wrap restriction means. This member is an elastic member provided on the upstream side of the transfer nip T in the transfer paper transport direction and in contact with the back side of the image printing surface (hereinafter referred to as the back surface) which is the surface of the transfer paper 8 facing the transfer roller 10. It is an elastic winding restriction member 300 having the following. As the material, for example, PET (polyethylene terephthalate) can be used.

FIG. 3 is a diagram showing the transfer path P of the transfer sheet in the area A of FIG. For image transfer,
The registration roller 11 starts rotating at the timing of being superimposed on the toner image on the photosensitive drum 1, and a transfer nip T formed by the photosensitive drum 1 and the transfer roller 10 is formed.
The transfer paper 8 is sent out. Before the transfer paper 8 reaches the transfer nip T, the back surface passes through a position where the back surface contacts the elastic winding regulating member 300. At this time, if the stiffness of the transfer paper 8 is weak, the transfer paper 8 is pushed from the back surface by the elastic wrapping restricting member 300, protrudes toward the image printing surface side, and enters the transfer nip T. As a result, the transfer paper 8 enters the transfer nip T with a stable behavior without being bent immediately before entering the transfer nip T. Therefore, it is possible to prevent image unevenness caused by the transfer paper 8 wrapping around the transfer roller 10.

If the transfer paper 8 originally conveyed is made of thick paper and has a strong stiffness, the elastic winding restriction member 30 may be used.
Since 0 is elastically deformed, the transfer paper 8 is not pushed up from the back surface more than necessary. Accordingly, the transfer path of the transfer paper 8 is shifted too much to the left in the figure, and the leading end of the transfer paper directly collides with the guide portion for guiding the transfer paper 8 to the predetermined transfer path, and cannot be conveyed. Nothing to do. When the winding restriction member 300 is made of a non-elastic member such as a sheet metal, such a problem may occur.

The elastic winding restriction member 300 is made of a conductive material. Thereby, it has a static elimination function for eliminating static electricity from the contacting member. Even when a transfer material made of a material that is easily charged such as OHP paper is used, the charge can be removed by bringing the transfer material into contact with the elastic winding regulating member 300 just before entering the transfer portion. As a result, even a transfer material made of a material that is easily charged can enter the transfer portion in a state where the charge is removed, and it is possible to prevent generation of image dust caused by charging of the transfer material.

In the present embodiment, the elastic winding restricting member 300 is formed of a conductive member so that a static elimination function can be exhibited. This eliminates the need to newly add a power supply, thereby preventing an increase in the size of the device.

As described above, in the present embodiment, the conductive elastic winding restricting member 3 is used in order to exhibit the charge removing function.
Although 00 is used, a configuration may also be adopted in which a bias for removing electricity is applied to the winding regulating member to remove electricity from the transfer material.

The photosensitive drum 1 of this embodiment has a diameter of 30 mm and a linear velocity of 120 mm / s.
ec. Thus, by setting the diameter of the photosensitive drum 1 to 35 mm or less, the separability of the transfer paper 8 having passed through the transfer nip T from the photosensitive drum 1 can be improved. Further, the linear velocity of the photosensitive drum 1 is set to 1
By setting the speed to 20 mm / sec or less, the separation property of the transfer material from the photosensitive drum 1 is not affected by various conditions such as the use environment of the apparatus, the type of the transfer material, the humidity control condition of the paper, and the gap. Can be secured. by this,
The separation claw can be omitted.

[0042]

According to the image forming apparatus of the present invention, when the transfer material is transported vertically and the transfer nip is viewed from the center of the latent image carrier, the depression angle is in the range of 25 ° to 30 °. In an image forming apparatus in which a transfer nip is set at a proper position,
There is an excellent effect that image dust can be prevented.

According to the image forming apparatus of the present invention, for a transfer material having no rigidity, the transfer material can be provided with tension to prevent image dust, and for a transfer material having a rigidity. There is an excellent effect that there is no problem that the transport direction of the material is changed in an unexpected direction.

According to the image forming apparatus of the third aspect, there is an excellent effect that generation of image dust caused by charging of the transfer material can be prevented.

According to the image forming apparatus of the fourth aspect, there is an excellent effect that the static electricity elimination function can be easily provided by making the elastic winding regulating member conductive.

According to the image forming apparatus of the fifth aspect, there is an excellent effect that the transfer material can be separated from the latent image carrier without providing the separating means.

According to the image forming apparatus of the sixth aspect, there is an excellent effect that the transfer material can be separated from the latent image bearing member without being affected by the use environment of the apparatus and each condition of the transfer material.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a printer according to an embodiment.

FIG. 2 is a partially enlarged view of a printer showing a characteristic portion of the invention.

FIG. 3 is an explanatory diagram of a transfer paper transport path in an area A in FIG. 2;

FIG. 4 is an explanatory diagram of a conventional image forming apparatus that vertically conveys a transfer material.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 2 charging roller 3 developing unit 4 cleaning unit 8 transfer paper 10 transfer roller 11 registration roller pair 12 transfer paper transport path 14 fixing roller 15 press roller 16 fixing device 22 static elimination brush 100 process cartridge 200 printer 201 Door) T transfer nip

Continued on the front page F term (reference) 2H035 CA07 CB01 CD13 CG01 2H200 FA08 FA17 FA19 GA06 GA23 GA29 GA44 HA02 HB07 HB12 HB14 HB22 JA02 JB12 JB17 JB20 JB41 JB46 JB47 KA02 KA07 LA12 MB01 MC01 PA11

Claims (6)

[Claims] A latent image carrier having a drum shape; developing means for forming an electrostatic latent image on the latent image carrier into a toner image; and a predetermined transfer nip formed on the surface of the latent image carrier. A transfer roller for transferring the toner image to a transfer material conveyed to the transfer nip; and a transfer material conveying means for conveying the transfer material so that the transfer material passes in a substantially vertical direction from below to above the transfer nip. An image forming apparatus in which the position of the transfer nip is set such that the depression angle α when viewing the transfer nip from the center of the latent image carrier is within a range represented by the following equation: 25 ° ≦ α ≦ 30 ° An image forming apparatus, comprising: a winding restriction means for causing the transfer material to enter the transfer nip from a direction in which the transfer material does not wind around the transfer roller at an upstream side of the transfer nip. 2. The image forming apparatus according to claim 1, wherein the winding restriction means contacts the surface of the transfer material facing the transfer roller on the upstream side of the transfer nip in the transfer material transport direction, and has elasticity. An image forming apparatus comprising an elastic winding restricting member having the same. 3. The image forming apparatus according to claim 2, wherein a charge removing function for removing charge from said transfer material is added to said elastic winding restriction member. 4. The image forming apparatus according to claim 3, wherein said elastic winding restricting member is made conductive. 5. The image forming apparatus according to claim 1, wherein the diameter of the drum of the latent image carrier is 35 mm or less. 6. The image forming apparatus according to claim 1, wherein the linear speed of the latent image carrier is set to 120 mm / sec or less.