JP2705581B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to a printer or facsimile machine using an electrophotographic process for transferring a toner layer developed on an electrostatic latent image carrier to a printing medium such as paper. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus using an electrophotographic process, a transfer member in the form of a rotating roller or an endless belt in contact with an electrostatic latent image carrier (photoreceptor) has been provided. A so-called contact transfer in which a toner layer developed on the electrostatic latent image carrier is attracted to the transfer member side and transferred to the print medium by applying a voltage having a polarity opposite to that of the toner to the transfer member while passing the print medium. Image forming apparatuses are known (Japanese Patent Laid-Open Nos. 4-278977 and 2-2).
21040).

As the above-described transfer member in the form of a rotating roller, there is a member in which metal oxide or carbon powder is dispersed in a foaming roller of urethane or the like so as to have semiconductivity. There are a belt in which polyester is applied to a rubber belt and a belt in which a polyamide endless belt is supported by a plurality of rollers.

[0004]

However, in order to obtain a good transfer effect, the contact transfer type image forming apparatus requires a sufficient nip between the electrostatic latent image carrier, the print medium, and the transfer member. A width was required, and the pressing force between them had to be increased. For this reason, in the above-mentioned conventional device, the surfaces of the electrostatic latent image carrier and the transfer member are easily damaged,
In addition, there are disadvantages such as an increase in the torque of the device.

Further, in the above-described conventional apparatus, if the pressing force is large, the toner once transferred to the print medium returns to the electrostatic latent image carrier, and distortion or voids occur in characters or solid black images. There is also a problem to do.

Further, in the above conventional apparatus, when a print medium smaller than a developed toner image is used, for example, when A4 paper is fed for A3 size image data, the presence of the print medium There is a problem that the toner on the electrostatic latent image carrier is transferred to the transfer member in the non-printing area, and this causes back smearing of the next print medium. Further, in normal printing, there is also a problem that fogging toner or the like is transferred to the transfer member between pages where the electrostatic latent image carrier and the transfer member are in direct contact, and this is accumulated to cause back smear of the print medium.

[0007] The present invention has been made in view of the above points,
Even if the nip between the transfer member and the electrostatic latent image carrier is non-uniform due to each mounting error, twist, etc., an image forming apparatus capable of absorbing the error by a simple method and obtaining high transfer efficiency. The purpose is to provide.

Another object of the present invention is to provide an image forming apparatus capable of improving transfer failures caused by lack of black solid density due to missing characters or edge effects and environmental fluctuations.

Still another object of the present invention is to provide an image forming apparatus which can prevent the transfer member and the print medium from being stained and can extend the life of the transfer member.

[0010]

According to the present invention, a printing medium is passed through a nip portion between an electrostatic latent image carrier and a transfer member facing each other, and a bias voltage is applied to the transfer member. In an image forming apparatus for transferring a toner layer developed on an electrostatic latent image carrier by applying to a print medium, a rotating cylindrical elastic roller and a peripheral length longer than the peripheral length of the elastic roller, seamless membrane member provided a cylindrical so as to have an elastic roller therein, seamlessly
It is composed of a member that has cleaning properties for the thin film member.
Made which are, by pressing and supporting a portion of the seamless thin film member from the outside to the outer circumferential surface of the elastic roller, the electrostatic outer surface of the seamless thin film member to form a space between the seamless thin film member and the elastic roller A transfer member is constituted by a pair of opposing support members that are brought into contact with the latent image carrier and the print medium, or a support member concentric with the elastic roller and having a semicircular cross section.

In the present invention, the support member is constituted by a member having a cleaning property for the seamless thin film member.

[0012]

According to the present invention, the seamless thin film member is supported by the support member such that the elastic roller comes into contact with the electrostatic latent image carrier and the print medium via the space portion and the seamless thin film member. The contact pressure between the electrostatic latent image carrier and the printing medium can be set to a weaker contact pressure than when a conventional rotating roller or endless belt is used as a transfer member.

Further, since a space is formed between the seamless thin film member and the elastic roller, the electrostatic latent image carrier and the elastic roller are not uniform due to their warpage, twist, and the like. However, the error can be absorbed by the bulging portion of the seamless thin film member including the space. Further, the seamless thin film member has a feature that resistance unevenness is small, and can contact the electrostatic latent image carrier and the print medium with a sufficient nip width.

Further, since the supporting member is formed of a member having a cleaning property for the seamless thin film member, the seamless thin film member contaminated with fog toner or jam can be cleaned.

Also, in the present invention, the respective surface roughnesses are set so that the dynamic friction coefficient between the elastic roller and the seamless thin film member is larger than the dynamic friction coefficient between the seamless thin film member and the support member. The roller and the seamless thin film member can rotate without causing a slip.

[0016]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration diagram of an embodiment of the apparatus of the present invention.
In this embodiment, the toner hopper 1, the supply member 4, the toner carrier 5, the thin layer forming member 6, the drum-shaped electrostatic latent image carrier 7,
The transfer member 8 includes a transfer member 8 disposed opposite to the electrostatic latent image carrier 7, a charging member 9 disposed opposite to the electrostatic latent image carrier 7, and a cleaner unit 10. There is a feature in the configuration.

The toner hopper 1 is arranged to face the electrostatic latent image carrier 7, stores the toner 2, and agitates the toner 2 by the agitating member 3. Supply member 4 and toner carrier 5
Are rollers that rotate counterclockwise, respectively. The toner carrier 5 is composed of a metal roller made of, for example, stainless steel or aluminum, and an elastic portion provided on the outer periphery of the roller, which is provided with conductivity, such as silicone, nitrile-butadiene copolymer, and urethane rubber.

The elastic portion of the toner carrier 5 has a rubber hardness of 30 ° to 40 ° according to a JIS A hardness meter in consideration of the contact pressure between the thin layer forming member 6 and the electrostatic latent image carrier 7. Further, in consideration of leakage to the electrostatic latent image carrier 7 due to low resistance of the toner carrier 5 and fogging due to high resistance, etc., the resistance value between the metal roller surface and the shaft is 10 ⁵ Ω or more.
Desirably, it is 10 ⁶ Ω.

The negatively chargeable polyester toner used in the present embodiment has a particle size of about 10 μm,
In order to uniformly charge the toner carrier 5, the ten-point average surface roughness Rz of the toner carrier 5 is preferably 10 μm.

The thin layer forming member 6 is a member for forming the toner 2 supplied to the toner carrier 5 into a uniform thin layer.
It is made of a spring material made of a thin metal plate such as phosphor bronze or a material in which silicon rubber is applied to a contact portion with the toner carrier 5. The electrostatic latent image carrier 7 is a drum-shaped photoreceptor, which is driven to rotate clockwise in the figure, uniformly charged by the charging member 9, and exposes image data with light such as a laser to form an electrostatic latent image. To form

The transfer member 8 is a member constituting a main part of the present embodiment. As will be described later, an elastic roller, a tubular seamless thin film member provided with the elastic roller therein, and a supporting member. And a support member. The transfer member 8 has a structure in which a voltage from a power supply (not shown) is applied to the shaft of the elastic roller, and the applied voltage has a polarity opposite to that of the toner at the time of transfer to the print medium 11. At the time of non-transfer from the end of transfer until the next print medium passes, cleaning of the toner on the transfer member 8 and transfer of the toner on the electrostatic latent image carrier 7 to prevent transfer of the toner on the transfer member 8 to the transfer member 8 are performed. (Ie, the same polarity as the toner).

In this embodiment, since a non-magnetic toner having a negative charge is used, a positive voltage is supplied to the transfer member 8 as a bias voltage during transfer and a negative voltage as a bias voltage during non-transfer. The charging member 9 charges the electrostatic latent image carrier 7 uniformly. The cleaner unit 10 removes the residual adhesion of the toner on the electrostatic latent image carrier 7.

Next, the operation of this embodiment will be described.
The charge is uniformly applied to the surface of the electrostatic latent image carrier 7 rotating clockwise by the charging member 9. When the charged portion of the electrostatic latent image carrier 7 moves to a position between the charging member 9 and the toner carrier 5, light modulated by image data from a light source (not shown) is incident. To form an electrostatic latent image.

On the other hand, the toner 2 in the toner hopper 1 is supplied to the toner carrier 5 which is rotated counterclockwise by the toner supply member 4 which is stirred by the stirring member 3 and driven to rotate counterclockwise. The toner 2 supplied to the toner carrier 5 is triboelectrically charged and regulated by the thin-layer forming member 6, and is made into a more or less uniform thin layer. In this way,
The charged toner formed as a thin layer on the toner carrier 5 is carried to a portion where the toner carrier 5 and the electrostatic latent image carrier 7 face each other as the toner carrier 5 rotates.

When the portion of the electrostatic latent image carrier 7 on which the above-described electrostatic latent image is formed reaches a position facing the toner carrier 5, the surface potential of the electrostatic latent image carrier 7 and the toner carrier The charged toner on the toner carrier 5 is changed to an electrostatic latent image carrier 7 by an electric field based on a potential difference from a bias voltage applied to the electrostatic latent image carrier 7.
It moves to the electrostatic latent image on the surface to form a toner image.

The toner image developed on the electrostatic latent image carrier 7 as described above is carried to a position facing the transfer member 8 as the electrostatic latent image carrier 7 rotates clockwise. At this time,
A print medium 11 such as paper is conveyed and passed through a nip portion between the electrostatic latent image carrier 7 and the transfer member 8. The transfer member 8 applies a bias voltage having a polarity opposite to that of the toner from the back of the print medium 11 to transfer and transfer the developed toner layer on the electrostatic latent image carrier 7 side to the front of the print medium 11.

The portion of the transferred electrostatic latent image carrier 7 moves to a position facing the cleaner unit 10 according to the clockwise rotation of the electrostatic latent image carrier 7, and is cleaned there. Hereinafter, the same operation as described above is repeated.

Next, each embodiment of the transfer member 8 which is a main part of the present invention will be described. FIG. 2 shows a cross-sectional view of the first embodiment of the transfer member 8. In the figure, a transfer member 81 has a cylindrical elastic roller 13, a peripheral length longer than the peripheral length of the elastic roller 13, and a seamless thin film member 14 wrapped around the elastic roller 13 and an elastic thin film member 14. By pressing against the outer peripheral surface of the roller 13, the seamless thin film member 14 is
And a pair of rod-shaped support members 15 provided to face each other.

The elastic roller 13 comprises a metal shaft 13a made of stainless steel, aluminum, or the like, and an outer periphery provided with a foaming material or rubber material such as silicone, urethane, nitrile, ethylene-propylene copolymer, etc., provided with conductivity. Have been. A voltage is applied to the metal shaft 13a from a power source (not shown).

The seamless thin film member 14 is made of a sheet-like member obtained by adding carbon or metal oxide to a fluororesin such as PFA or polyamide, or a seamless electroformed sleeve of nickel or stainless steel .

The support member 15 has the same length in the width direction as the seamless thin film member 14 and has a cleaning property, and has elasticity such as felt made of a fine polyester fiber or a binder of polyester and polyurethane. Consists of pads. Further, when the kinetic friction coefficient between the elastic roller 13 and the seamless thin film member 14 is μ ₁ and the kinetic friction coefficient between the seamless thin film member 14 and the support member 15 is μ ₂ , the elastic roller 13 is set such that μ ₁ > μ _2. The surface roughness of the seamless thin film member 14 and the support member 15 is adjusted. As described later, this is for rotating the elastic roller 13 and the seamless thin film member 14 without causing a slip.

According to the present embodiment, the seamless thin film member 14 is formed by the elastic roller 13 by the pair of support members 15 facing each other.
Is pressed and supported on the outer peripheral surface of. At this time, a seamless thin film member 14 is provided on the outer peripheral portion of the elastic roller 13 on the side opposite to the print medium 11.
Keep close together.

As a result, the seamless thin film member 14 has a circumference longer than the circumference of the elastic roller 13, and there is no support member outside the seamless thin film member 14 on the side in contact with the print medium 11. Further, the seamless thin film member 14
2 has a rigidity such that it does not contact the outer peripheral portion of the elastic roller 13 on the print medium 11 due to its own weight. Therefore, as shown in FIG. Gather to form a space 16 between the elastic roller 13 and the seamless thin film member 14.

Next, the operation of this embodiment will be described.
The elastic roller 13 rotates in a counterclockwise direction in the figure substantially in synchronization with the rotation of the electrostatic latent image carrier 7 by a driving mechanism (not shown). As a result, the seamless thin film member 14 rotates following the rotation of the elastic roller 13 and the seamless thin film member 14 having the space 16 is formed on the electrostatic latent image carrier 7 and the print medium 11 with an appropriate nip width. On the other hand, the contact is made with a weaker contact pressure than when a conventional rotating roller or endless belt is used as a transfer member.

Thus, the surface of the electrostatic latent image carrier 7 is not damaged, and the torque of the apparatus does not increase. Further, a voltage applied to the metal shaft 13a of the elastic roller 13 is uniformly applied as a transfer bias voltage on the print medium 11 via the elastic roller 13 and the seamless thin film member 14, and as a result, the electrostatic latent image carrier As the toner image transferred from the printing medium 7 to the printing medium 11, an image without characters missing or distortion can be obtained, and the electrostatic latent image carrier 7 is not damaged.

When a foaming roller is used as a direct transfer unit, it is technically difficult to manufacture a foaming roller by uniformly adding a conductive material such as carbon powder to a foaming material such as urethane. Resistance unevenness in the width direction of A
Environments such as when printing on narrow paper where a portion where the electrostatic latent image carrier 7 and the transfer member (foaming roller) are in direct contact with each other, such as when performing postcard printing with a three-size compatible machine, or at low temperature, low humidity, and high temperature and high humidity Although but a transfer failure is observed by the transfer current shortage and the transfer bias insufficient with respect to the print medium when varied, seamless thin film member 14 used in this embodiment, fluororesin and Po
Uses lamide and is not a foam, so carbon etc.
Unevenness due to uniform dispersion of conductive additives
Use an electroformed sleeve that does not have
Therefore, the above problem can be solved .

Further, in this embodiment, since the support member 15 has a cleaning property, the surface of the seamless thin film member 14 contaminated with fog toner or jam can be cleaned. Polar bias (cleaning bias) could not prevent,
It is possible to prevent back contamination of the printing medium due to jamming and printing running. Further, since the surface of the seamless thin film member 14 can be cleaned, the life of the seamless thin film member 14 can be extended.

FIG. 3 is a sectional view of a second embodiment of the transfer member 8 as a main part of the present invention. 2, the same components as those in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted. The second shown in FIG.
The transfer member 82 of the embodiment is characterized in that a pair of roller-shaped support members 17 are used as support members.

The roller-shaped support member 17 is
The seamless thin film member 14 is pressed and supported on the outer peripheral surface of the elastic roller 13 at the same height position as the metal shaft 13a, and is rotated clockwise in the figure in synchronization with the rotation of the elastic roller 13. ing.

The roller-shaped support member 17 is made of a foam such as urethane or ethylene / propylene copolymer and has a cleaning property. The transfer member 82 of this embodiment is also similar to the transfer member 81 shown in FIG.
Having a space portion 16 and the printing medium 11 and the electrostatic latent image carrier 7
Since the contact can be made with a weak contact pressure, the same effect as in the first embodiment can be obtained. Further, in this embodiment, since the support member 17 rotates together with the elastic roller 14, there is a feature that the cleaning property is less deteriorated than in the first embodiment.

Next, a third embodiment of the main part of the present invention will be described. FIG. 4 is a sectional view of a third embodiment of the transfer member 8 as a main part of the present invention. 2, the same components as those in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted.

The transfer member 83 of the third embodiment shown in FIG.
The present invention is characterized in that a seamless thin-film member 14 is pressed against the elastic roller 13 from above the elastic roller 13 upward from below the elastic roller 13 as a supporting member, and a supporting member 18 concentric with the elastic roller 13 and having a semicircular cross section is used.

The support member 18 is made of slidable polyester fiber or the like, and has a cleaning property. Similarly to the transfer members 81 and 82 shown in FIGS. 2 and 3, the transfer member 83 of this embodiment has the space portion 16 of the seamless thin film member 14 and is weak against the print medium 11 and the electrostatic latent image carrier 7. Since the contact can be made with the contact pressure, the same effect as in the first embodiment can be obtained.

[0044]

As described above, according to the present invention,
The contact pressure between the transfer member and the electrostatic latent image carrier and the print medium,
By using a seamless thin film member, the contact pressure is made weaker than when a conventional rotating roller or endless belt is used as a transfer member, so that the surface of the electrostatic latent image carrier is damaged or the torque of the device is reduced. It can be prevented from increasing.

According to the present invention, even if the electrostatic latent image carrier and the elastic roller are non-uniform due to their warpage, twist, etc., the error is reduced by the bulging portion of the seamless thin film member including the space. Since the transfer bias voltage can be uniformly applied to the print medium because it can be absorbed, good transfer efficiency can be obtained by a simple method, and the seamless thin film member can be sufficiently applied to the electrostatic latent image carrier and the print medium. Since the contact is made with an appropriate nip width, it is possible to improve image quality degradation such as missing characters, image distortion, and uneven density.

Further, according to the present invention, since the seamless thin film member has a feature that resistance unevenness is small, it is possible to improve transfer failure caused by insufficient transfer current or insufficient transfer bias caused by environmental fluctuation or the like.

Further, according to the present invention, the support member is
By forming the seamless thin film member from a member having a cleaning property, the seamless thin film member contaminated with fog toner or jam is cleaned, so that it is prevented by a bias (cleaning bias) of the same polarity as the toner when paper is not passed. It is possible to prevent the backing of the printing medium due to the jam or the printing running, which could not be performed.

Further, since the surface of the seamless thin film member can be cleaned, the life of the seamless thin film member can be extended.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a sectional view of a first embodiment of a main part of the present invention.

FIG. 3 is a sectional view of a second embodiment of a main part of the present invention.

FIG. 4 is a sectional view of a third embodiment of a main part of the present invention.

[Explanation of symbols]

 Reference Signs List 1 toner hopper 2 toner 4 supply member 5 toner carrier 6 thin layer forming member 7 electrostatic latent image carrier 8 transfer member 9 charging member 11 printing medium 13 elastic roller 13a shaft 14 seamless thin film member 15, 17, 18 support member 16 space Unit 81 Transfer Member of First Embodiment 82 Transfer Member of Second Embodiment 83 Transfer Member of Third Embodiment

Claims (2)

(57) [Claims] 1. A printing medium is passed through a nip portion between an electrostatic latent image carrier and a transfer member which are opposed to each other, and a bias voltage is applied to the transfer member to develop the image on the electrostatic latent image carrier. An image forming apparatus for transferring the toner layer to the printing medium, wherein the rotating roller has a cylindrical elastic roller, a peripheral length longer than the peripheral length of the elastic roller, and the elastic roller is provided inside. Cylindrical seamless thin film member, and has a cleaning property for the seamless thin film member
It is constituted by a member, by pressing and supporting a portion of the seamless thin film member from the outside to the outer peripheral surface of said elastic roller, the seamless form a space between the elastic roller and the seamless thin film member An image forming apparatus, wherein the transfer member is constituted by a pair of opposing support members that bring an outer surface of a thin film member into contact with the electrostatic latent image carrier and the print medium. 2. A printing medium is passed through a nip portion between an electrostatic latent image carrier and a transfer member opposed to each other, and a bias voltage is applied to the transfer member to develop the image on the electrostatic latent image carrier. An image forming apparatus for transferring the toner layer to the printing medium, wherein the rotating roller has a cylindrical elastic roller, a peripheral length longer than the peripheral length of the elastic roller, and the elastic roller is provided inside. Cylindrical seamless thin film member, and has a cleaning property for the seamless thin film member
A part of the seamless thin film member is supported on the outer peripheral surface of the elastic roller from the outside by a light pressure contact with the outer peripheral surface of the elastic roller in the direction of the printing medium , thereby forming a space between the seamless thin film member and the elastic roller. Forming the transfer member by a support member concentric with the elastic roller and having a semicircular cross section, wherein the outer surface of the seamless thin film member is brought into contact with the electrostatic latent image carrier and the print medium. Characteristic image forming apparatus.