JP2002108116A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device by which an excellently transferred image can be obtained surely by making the contact zone of an intermediate transfer body with a recording material satisfactorily large and adhering the recording material tightly to the intermediate transfer body at the position where a transfer electric field is not applied. SOLUTION: This image forming device is constituted so that a transfer unit is brought into contact with the surface of the intermediate transfer body and is provided with a transfer roller for guiding the intermediate transfer body in such a state that the contact surface is bent in a recessed shape along a part of the outer peripheral surface and a transfer member disposed on the rear side of the intermediate transfer body in the contact zone. An electric field controlling member is arranged on the upstream side of the transfer member.

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 using a transfer system using an intermediate transfer member.

[0002]

2. Description of the Related Art FIG. 4 is an explanatory view showing an example of a main part of a conventional image forming apparatus, and FIG. 5 is an explanatory view of a main part constituting the transfer apparatus of FIG. The image forming apparatus includes a drum-shaped photoreceptor 11 on which an electrostatic image is formed, a charging unit 12 for charging the photoreceptor 11, and a toner image formed by visualizing the electrostatic image formed on the photoreceptor 11. Developing unit 13 for forming an image
And an endless belt-shaped intermediate transfer member 14 on which the toner image is transferred from the photoconductor 11 to the surface, and the intermediate transfer member 14
And a transfer device 50 for transferring the upper toner image onto the recording material 30. In this figure, 15 is the photosensitive member 1
1 is a cleaning unit, 16 is a support roller for supporting the endless intermediate transfer body 14, and 17 is a recording device 30 for transferring the recording material 30 to the transfer device 50.
Is a transport mechanism that transports the recording material 30 from the transfer device 50 to a fixing device (not shown).

[0005] As shown in FIG. 5, the transfer device 50 includes a transfer roller 52 made of a conductor in contact with the surface of the intermediate transfer member 14, and a transfer roller 52 in contact with the back surface of the intermediate transfer member 14. The recording material 30 is supplied to a nip 53 formed by the conductive backup roller 51 which is rotated while pressing the intermediate transfer member 14 therebetween. A high-voltage power supply is connected to the transfer roller 52 and the backup roller 5
1 is brought to the ground potential state, so that the nip 5
3, a transfer electric field is formed, and by the action of the transfer electric field, the toner carried on the surface of the intermediate transfer body 14 is transferred to the recording material 30 superimposed on the surface, whereby the toner image is transferred.

However, the transfer device 50 having the above-described structure is used.
In this case, the nip 53 is composed of a pair of rollers, so that it is difficult to take a sufficient size. As a result, the time during which the transfer electric field works effectively is insufficient, so that the toner image There has been a problem that transfer is not sufficiently performed and transfer defects such as white spots occur. Further, the state of close contact between the recording material 30 and the intermediate transfer body before the contact start point between the secondary transfer roller and the intermediate transfer body is likely to be unstable due to conditions such as the rigidity of the recording material 30, and the above-mentioned condition is not satisfied when the close contact is insufficient. When the recording material comes near the contact start point, the toner image is disturbed and transferred due to the transfer electric field acting in the minute space,
There was a problem.

In order to solve such a problem, the intensity of the transfer electric field may be increased. In this case, however, the area outside the nip portion 53, that is, the recording material 30 is in close contact with the intermediate transfer body 14. The transfer electric field acts even in the non-printed area, causing the transfer of the toner. As a result, there is a problem that image defects such as so-called "dust" and "repelling" occur.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made based on the above circumstances, and its object is to provide:
An intermediate transfer member, and a transfer device for transferring the toner image on the intermediate transfer member to a recording material, and a contact area between the intermediate transfer member and the recording material can be made sufficiently large;
As a result, it is an object of the present invention to provide an image forming apparatus capable of reliably obtaining a transfer image without image defects. Another object of the present invention is to provide an image forming apparatus in which a transfer electric field does not act in a region where a recording material is not in close contact with an intermediate transfer body, and therefore a high quality transfer image can be reliably obtained. It is in.

[0007]

According to the present invention, there is provided an image forming apparatus including a transfer device for transferring a toner image carried on the surface of an intermediate transfer member onto a recording material.
The transfer device includes a transfer roller having an outer peripheral surface that comes into contact with the surface of the intermediate transfer body and guides the intermediate transfer body in a state where the surface is curved in a concave shape, and the intermediate transfer body and the transfer roller. And a transfer member that forms a transfer electric field between the transfer roller and a contact area where the transfer roller is in contact with or close to the back surface of the intermediate transfer body. In the above-described image forming apparatus, it is preferable that the transfer roller has a surface coating layer made of a conductive elastic body.

An image forming apparatus according to the present invention is an image forming apparatus including a transfer device for transferring a toner image transferred on the surface of an intermediate transfer member to a recording material, wherein the transfer device is provided on the surface of the intermediate transfer member. A transfer roller having an outer peripheral surface that is in contact with and guides the intermediate transfer body in a state where the surface thereof is curved in a concave shape, and a contact area where the intermediate transfer body and the transfer roller are in contact with each other. A transfer member that forms a transfer electric field between the transfer roller and the transfer member that is disposed in contact with or close to the back surface, and is disposed at a position upstream of the transfer member in the path of the intermediate transfer body in the contact region. And a transfer electric field regulating member.

[0009]

According to the image forming apparatus of the present invention, in the transfer device, the intermediate transfer member is guided by the transfer roller with the surface carrying the toner image curved in a concave shape. The contact area where the outer peripheral surface of the roller contacts can be made sufficiently large. Therefore, the area where the recording material is in close contact with the intermediate transfer member can be made large, and therefore, a sufficiently large transfer electric field can be applied for a sufficiently long time. A good transfer image without any defect can be surely formed.

Further, by providing the transfer electric field regulating member, the boundary of the area where the transfer electric field is applied can be strictly regulated. Therefore, the transfer electric field is limited only at a place where the recording material and the intermediate transfer member are in close contact. Therefore, a high-quality image free from toner image disturbance can be reliably obtained.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory diagram showing a configuration of a main part in an example of the image forming apparatus of the present invention, and FIG. 2 is an explanatory diagram showing a configuration of a transfer device. The image forming apparatus includes a drum-shaped photoreceptor 11 on which an electrostatic image is formed, a charging unit 12 for charging the photoreceptor 11, and a toner image formed by visualizing the electrostatic image formed on the photoreceptor 11. A developing unit 13 for forming an image, and a belt-like intermediate transfer body 14 moving along an endless path through which the toner image is transferred from the photoreceptor 11 to the surface
And a transfer device 20 for transferring the toner image on the intermediate transfer body 14 to the recording material 30, and a fixing device 40 for fixing the toner image to the recording material 30. In this figure,
Reference numeral 15 denotes a cleaning unit for the photoconductor 11, reference numeral 16 denotes a supporting roller for supporting the intermediate transfer member 14, reference numeral 17 denotes a guide plate for supplying the recording material 30 to the transfer device 20, and reference numeral 18 denotes a fixing device for applying the recording material 30 from the transfer device 20. A transport mechanism for transporting the paper to the paper 40.

The fixing device 40 includes a heating roller 41 having a heating source therein, which is disposed in contact with the surface of the recording material 30 onto which the toner image has been transferred, and a pressing roller 42 provided so as to be pressed against the heating roller 41. And the heating roller 4
A fixing nip (not shown) is formed by the fixing roller 1 and the pressure roller 42, and the toner image is thermally fixed to the recording material 30 at the fixing nip.

In the transfer device 20, a transfer roller 21 is in contact with the surface of an intermediate transfer member 14 carrying a toner image on its outer peripheral surface, and is held by a holding member 26 in a contact area 25 where the two are in contact. Transfer member 2
2 is disposed so as to be in contact with the back surface of the intermediate transfer body 14.

More specifically, as shown in FIG. 2, the transfer roller 21 has an upstream support roller 16A and a downstream support roller 16B which support the intermediate transfer member 14 on the upstream and downstream sides thereof. Are arranged in such a manner that the surface of the intermediate transfer member 14 is pressed so that a part of the outer peripheral surface (the upper end portion in FIG. 2) protrudes inward from the common tangent line L of the intermediate transfer member 14. The surface of the transfer roller 21 is guided in a state of being in contact with the outer peripheral surface of the transfer roller 21 along a concavely curved path along a part of the outer peripheral surface of the transfer roller 21.
Are formed. Then, the transfer roller 21 is set to the ground potential, and a high voltage power supply is connected to the transfer member 22, so that a transfer electric field is formed in the contact area 25.

The transfer roller 21 has a configuration in which a drum-shaped core is covered with a surface coating layer (not shown), and the surface coating layer is formed of, for example, semiconductive rubber or resin. , The rotation axis of which extends in the width direction of the recording material 30. This transfer roller 21
Has a diameter of 15 to 35 mm and an axial length of 210 to 350 mm, for example. Aluminum, stainless steel, or the like can be used as a material of the core metal, and urethane rubber, silicone rubber, EPD
A, It is preferable to use a fluorine resin. Further, the transfer roller 21 may be provided with an intermediate layer made of an elastic body such as urethane foam having semiconductivity between the cored bar and the surface coating layer. According to the transfer roller 21 provided with the intermediate layer and the surface coating layer made of such an elastic body, the degree of close contact between the intermediate transfer body 14 in the contact area 25 or the recording material 30 is large, and It will be sure.

The transfer member 22 has a configuration in which, for example, an elongated rectangular sheet-like conductor is held by a holding member 26 such as a sheet metal. The transfer member 22 rotates around one of the long sides parallel to the axis of the transfer roller 21 as an axis. The spring 2 is supported freely, and the other of the long sides is inclined toward the downstream side in the conveyance direction of the intermediate transfer body 14.
3 is elastically pressed. As a material forming the transfer member 22, for example, a conductive rubber such as urethane rubber mixed with conductive particles such as carbon, a conductive brush, and the like can be used.

The size of the contact area 25 formed on the outer peripheral surface of the transfer roller 21 is, for example, 4 to 10 m.
m is preferable.

In such a transfer device 20, the toner image held on the surface of the intermediate transfer member 14 is transferred to the contact area 25.
The recording material 30 is supplied to the transfer device 20 by a recording material supply mechanism (not shown) in synchronization with the recording material, and is further conveyed to the contact area 25 at a timing corresponding to the toner image. Then, in the contact area 25, the surface of the intermediate transfer member 14 is brought into contact with the surface of the intermediate transfer member 14 by the action of the transfer electric field formed between the transfer roller 21 at the ground potential state and the transfer member 22 maintained at the high potential state. The carried toner moves to the surface of the recording material 30, and thereby the toner image is transferred. The magnitude of the transfer electric field is usually 1-2 k.
V is preferable, and is adjusted within an optimal range according to the environment at the time of image formation, the type of toner used, and various other conditions.

According to the transfer device 20 described above, the surface of the intermediate transfer member 14 is guided by the outer peripheral surface of the transfer roller 21 in a state where the surface is curved in a concave shape. The size of the contact area 25 where the roller 21 and the intermediate transfer member 14 contact each other can be made sufficiently large. Therefore, the area where the recording material 30 is in close contact with the intermediate transfer member 14 can be made large, and thus the transfer electric field can be applied for a sufficiently long time, and as a result, a good transferred image can be stably formed. , And can be reliably obtained. Therefore, the area where the recording material 30 is in close contact with the intermediate transfer body 14 does not change depending on the degree of rigidity of the recording material 30. Therefore, since the contact area 25 has a sufficient size, there is no possibility that image defects such as “dust” and “repelling” will occur, and thus sufficient transfer can always be achieved. Therefore, the recording material 30 to be used is not particularly limited, and even if any material is used, sufficient transfer without image defects can be achieved.

According to the image forming apparatus of the present invention provided with the above-described transfer device 20, the toner image carried on the intermediate transfer member 14 can be transferred onto one surface of the recording material 30 in an excellent manner. Therefore, it is possible to reliably form a good image without image defects.

FIG. 3 is an explanatory view showing another embodiment of the present invention. In this example, in the above-described configuration, further, in the contact region 25, on the upstream side of the transfer member 22 in the passage of the intermediate transfer body 14, and downstream of the contact start point between the intermediate transfer body 14 and the transfer roller 21. At the position
A transfer electric field regulating member 24 maintained at the ground potential is disposed, and the transfer electric field regulating member 24 is configured to be elastically pressed against the back surface of the intermediate transfer body 14 by means such as a spring (not shown). Have been.

The transfer electric field regulating member 24 can be made of a conductor having the same form and material as the transfer member 22, for example, and can be arranged in the same manner as the transfer member 22.

According to the structure provided with the transfer electric field regulating member 24, the boundary of the region where the transfer electric field formed by the transfer member 22 acts is regulated. Since the formation of the electric field is prohibited, it is possible to prevent the toner from starting to transfer before the recording material 30 comes into close contact with the intermediate transfer body 14, and therefore, it is possible to increase the transfer electric field in the contact region 25 without any adverse effect. Therefore, a good transferred image can be reliably formed.

According to the image forming apparatus provided with the transfer device 20 having the transfer electric field regulating member 24 as described above, the recording material 30 and the intermediate transfer member 14 are brought into close contact with each other in a place where the transfer electric field does not act. Therefore, it is possible to more reliably form a good image having no image defects.

The transfer device 20 described above is not limited to the above-described configuration, but can be variously modified as needed. For example, the disposition position of the transfer roller 21 can be changed to an arbitrary position in the up, down, left, and right directions, whereby the size and location of the contact area 25 formed with the intermediate transfer body 14 can be changed as necessary. It is possible to Further, the upstream support roller 16A and / or the downstream support roller 16B may be provided close to the transfer roller 21 so as to narrow the intermediate transfer member 14, and in this case, the intermediate transfer in the contact area 25 is performed. The degree of close contact between the body 14 and the transfer roller 21 can be increased. Further, the shape of the transfer member 22 and the manner of disposition thereof are not limited to the examples described above.

[0026]

According to the image forming apparatus of the present invention, in the transfer device, the intermediate transfer member is guided by the transfer roller in a state where the surface carrying the toner image is curved in a concave shape. The contact area where the outer peripheral surface of the transfer roller contacts can be made sufficiently large. Therefore,
The recording material and the intermediate transfer body are closely contacted in a large area, and a sufficiently large transfer electric field can be applied in a sufficiently large area in the conveyance direction of the intermediate transfer body. A good transfer image can be formed without fail.

Further, by providing the transfer electric field regulating member, the boundary of the area where the transfer electric field is applied can be strictly regulated, so that the recording material and the intermediate transfer member can be securely connected before the transfer electric field is applied. A good quality image can be obtained because of close contact.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a main part in an example of an image forming apparatus of the present invention.

FIG. 2 is an explanatory diagram illustrating a configuration of a transfer device.

FIG. 3 is an explanatory view showing a transfer device provided with a transfer electric field regulating member.

FIG. 4 is an explanatory diagram illustrating an example of a main part of a conventional image forming apparatus.

FIG. 5 is an explanatory diagram of a main part of the transfer device of FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Photoreceptor 12 Charging part 13 Developing device 14 Intermediate transfer member 15 Cleaning part 16 Support roller 16A Upstream support roller 16B Downstream support roller 17 Guide plate 18 Transport mechanism 20 Transfer device 21 Transfer roller 22 Transfer member 23 Spring 24 Transfer electric field Regulating member 25 contact area 26 holding member 30 recording material 40 fixing device 41 heating roller 42 pressure roller 50 transfer device 51 backup roller 52 transfer roller 53 nip L common tangential line

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masashi Saito 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation F-term (reference) 2H032 AA05 BA07 BA19 BA23 BA28

Claims (3)

[Claims] 1. An image forming apparatus comprising: a transfer device for transferring a toner image carried on a surface of an intermediate transfer member onto a recording material, wherein the transfer device is in contact with the surface of the intermediate transfer member and performs the intermediate transfer. A transfer roller having an outer peripheral surface that guides the body in a state where the surface is concavely curved; and a contact area where the intermediate transfer body and the transfer roller are in contact with or approaching the back surface of the intermediate transfer body. And a transfer member for forming a transfer electric field between the transfer roller and the transfer roller. 2. The image forming apparatus according to claim 1, wherein the transfer roller has a surface coating layer made of a conductive elastic body. 3. An image forming apparatus comprising a transfer device for transferring a toner image transferred on a surface of an intermediate transfer member to a recording material, wherein the transfer device contacts the surface of the intermediate transfer member and performs the intermediate transfer. A transfer roller having an outer peripheral surface for guiding the body in a state in which the surface is curved in a concave shape, and contacting or approaching the back surface of the intermediate transfer body in a contact area where the intermediate transfer body and the transfer roller contact. A transfer member that forms a transfer electric field between the transfer roller and the transfer roller; and a transfer electric field regulating member that is disposed at a position upstream of the transfer member in the path of the intermediate transfer body in the contact area. An image forming apparatus comprising: