JP2002202673A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an image forming device from malfunctioning and also reduce the size of the device in the image forming device which performs the primary transfer of a toner image formed on an image carrier onto an intermediate transfer belt, and then performs the secondary transfer and fixing simultaneously by pressing the toner image on a recording medium. SOLUTION: The intermediate transfer belt 20 is hung with tension over a driving roll 22, two driven rolls 23, 24, and a transfer roll 30, and the outer peripheral surface is abutted on an image carrier 10. On the upstream side of the secondary transfer part where the transfer roll 30 and a pressurizing roll 31 opposes each other, an electromagnetic inductive coil 50 opposing the inside of an intermediate transfer belt, a power source unit 46, and an output control part 47 are arranged, and the power source unit 46 and the output control part 47 are arranged so as to enclose the space behind the electromagnetic coil 50. Then, a cooling fan 48 is arranged for ventilating this space. Thus, a harness 45 from the power source unit 46 to the electromagnetic coil 50 can be shortened and a heat generation part can be effectively cooled.

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 that forms a visible image by transferring toner to a latent image due to a difference in electrostatic potential, such as an electrostatic recording method and ionography, and in particular, records the formed toner image by heating and pressing. The present invention relates to an image forming apparatus that simultaneously performs transfer and fixing on a medium.

[0002]

2. Description of the Related Art In recent years, in an image forming apparatus which transfers a toner to a latent image due to a difference in electrostatic potential to form a visible image, a toner image on an image carrier is temporarily transferred to an intermediate transfer member once. A method is adopted in which the transferred toner image is heated and melted, collectively secondarily transferred to a recording material, and simultaneously fixed. This method has an advantage that the transfer is performed in a non-electrostatic manner as compared with the conventional electrostatic transfer method, so that toner scattering does not occur and the thermal transfer efficiency can be improved. However, this type of image forming apparatus has the following problems.

[0003] For example, in this method, when the recording material is separated from the intermediate transfer member, a part of the melted toner remains on the intermediate transfer member because the toner is pressed against the recording material in a state where the toner is heated and melted. May cause offset.
Further, there is a problem that a large amount of heat energy is required for melting the toner on the intermediate transfer member, and the consumed energy is increased. In general, a heating roll or the like having a built-in heater is used, but the heating roll has a large heat capacity and requires a lot of heat energy to raise and maintain the temperature. Further, a large amount of heat is taken by the recording material. In order to solve this problem, means for reducing the consumed thermal energy has been devised.
Japanese Patent Application Publication No. 352804 discloses an image forming apparatus using a transfer fixing device for melting a toner image by electromagnetic induction heating.

In an image forming apparatus using this apparatus, a fluctuating magnetic field generated by an electromagnetic induction heating device penetrates through an electromagnetic induction heating layer of an intermediate transfer member, thereby generating an eddy current in this layer. It utilizes the heat generated by Joule heat. In such an apparatus, the intermediate transfer member is locally heated, so that the toner can be rapidly melted. For this reason, the toner can be brought into a molten state with an extremely small amount of heat, and the energy used can be reduced.

Further, since the melted toner is sufficiently heated, it adheres to the recording material when pressed against the non-heated recording material, and thereafter the heat is taken away by the recording material to lower the temperature. I do. At this time, since the amount of heat held by the toner image and the intermediate transfer member is small, the above-mentioned temperature drop occurs rapidly. Therefore, by appropriately setting the width of the transfer fixing area (hereinafter, referred to as a nip portion) where the recording material is pressed against the intermediate transfer member, the toner temperature at the exit of the nip portion can be set to a sufficiently small value. Offset can be prevented.

[0006]

However, an image forming apparatus using such an electromagnetic induction heating device has the following problems. A high-frequency power supply is required for the power supply used as an electromagnetic induction heating device, and it is usually from 10 kHz.
A frequency of about 100 kHz will be used. For this reason, radiation noise from a high-frequency power supply and line noise from a wiring (harness) or coil running around cause a problem, which may affect other peripheral devices and cause a malfunction. This line noise increases as the wiring of the harness or the like in the apparatus becomes longer, the resistance value of the coil also increases, and the heat loss increases. Conventional solutions to this problem do not suppress the occurrence of line noise or the like, but refer to JP-A-8-63036 and
As disclosed in Japanese Patent Application Laid-Open No. 191484 and Japanese Patent Application Laid-Open No. 2000-56600, rather, noise is controlled to suppress occurrence of malfunction.

The present invention has been made in view of the above problems, and an object of the present invention is to prevent malfunction of a device by suppressing generation of noise and to reduce the size of the device.

[0008]

In order to solve the above problem, the invention according to claim 1 is directed to an image carrier on which a latent image due to a difference in electrostatic potential is formed on a surface, and an image carrier having the same. A developing device for visualizing the toner by transferring the toner to a latent image, and an endless belt that is driven to rotate, and an intermediate transfer belt on which the toner image formed on the image carrier is primarily transferred onto the peripheral surface And a heating device that heats and melts the toner image on the intermediate transfer belt, and presses the toner image melted on the intermediate transfer belt onto a recording sheet to simultaneously perform secondary transfer and fixing. The invention according to the image forming apparatus to be performed, wherein the intermediate transfer belt has a conductive layer,
The heating device has an electromagnetic induction coil provided to face the inner surface of the intermediate transfer belt, and a power supply for supplying a high-frequency current to the electromagnetic induction coil, and the power supply is on the back side of the electromagnetic induction coil. And an image forming apparatus provided in the vicinity of the image forming apparatus.

This image forming apparatus generates a high-frequency magnetic field by supplying a high-frequency current to the electromagnetic induction coil, and generates an eddy current in the conductive layer of the intermediate transfer belt. By moving the intermediate transfer belt carrying the unfixed toner image at a predetermined speed in this magnetic field, the conductive layer generates heat. Thus, the toner is melted and pressed against the recording material to obtain a transfer-fixed image.

In general, radiation noise and line noise are likely to be generated from a high-frequency power supply, an electromagnetic induction coil, and a harness, and this noise may cause a malfunction of a peripheral device. By making the power supply device close to the back side of the electromagnetic induction coil and shortening the harness as much as possible, the generation of noise can be reduced, and malfunctions of peripheral devices can be effectively prevented.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, a portion from which a conductive wire for supplying a high-frequency current to the electromagnetic induction coil of the power supply device is brought close to the electromagnetic induction coil is provided. Is arranged so as to form a space between itself and the back surface of the electromagnetic induction coil, and a fan for blowing air into the space formed thereby is provided.

By arranging the electromagnetic induction coil and the power supply of the image forming apparatus in this manner, not only can the harness be shortened as much as possible, but also the cooling of the electromagnetic induction coil and the heat generation of the power supply which have conventionally been performed separately. The cooling of the elements can be performed simultaneously by one cooling fan, and the cost of the entire apparatus can be reduced.

According to a third aspect of the present invention, in addition to the configuration of the image forming apparatus according to the second aspect, a switching cycle (ON time) when a high-frequency current is supplied from the power supply to the electromagnetic induction coil is controlled. It is assumed that an output control unit is arranged so as to surround a space formed by the electromagnetic induction coil and the power supply device.

In this image forming apparatus, an output control section including temperature control is integrated adjacent to a high-frequency power supply. With this configuration, components related to the electromagnetic induction heating device can be housed in the endless intermediate transfer belt to be compact, and the entire device can be reduced in size and cost.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first, second, or third aspect, the ferromagnetic material is provided between the electromagnetic induction coil and the power supply device. It is assumed that an electrically insulating member is interposed.

In this image forming apparatus, a ferromagnetic material is provided on the side opposite to the intermediate transfer belt facing the induction coil of the electromagnetic induction heating means, that is, the side on which the power supply device and the output control section are arranged. In addition, a member having electrical insulation is arranged, and a shielding magnetic path is formed around the coil so that a high-frequency magnetic field generated from the electromagnetic induction heating means does not affect peripheral members. With this configuration, malfunction due to a high-frequency magnetic field can be prevented, and at the same time, electrical insulation is ensured so that leakage current from the winding of the electromagnetic induction coil does not flow into the power supply device or the output control unit. It can also play a role.

According to a fifth aspect of the present invention, there is provided the image forming apparatus according to the second or third aspect, wherein the electromagnetic induction coil comprises:
It is an object of the present invention to provide an image forming apparatus characterized in that an insulating film is provided so as to surround a power supply device and a space formed therebetween.

In the image forming apparatus having such a configuration, electric leakage from the electromagnetic induction coil to peripheral devices and the intermediate transfer belt can be prevented. As a result, insulation between the intermediate transfer belt and the conductive layer of the intermediate transfer belt can be maintained, and damage to the conductive layer of the intermediate transfer belt can be effectively prevented.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. This image forming apparatus is provided with a cylindrical image carrier 10 on which a latent image is formed by irradiating image light and then uniformly charged while rotating itself. A charging roll 11 that uniformly charges the surface of the image carrier 10 along the rotation direction is provided around the carrier 10.
An exposure device 12 for irradiating the image carrier 10 with image light to form a latent image on the surface thereof; and a developing unit 13 for selectively transferring toner to the latent image on the image carrier to form a toner image. ,
A cleaning device 14 for removing the toner remaining on the image carrier 10 after the transfer of the toner image, and a charge removing exposure device 15 for removing the charge on the surface of the image carrier 10 are provided.

Further, immediately downstream of the developing unit 13,
An endless intermediate transfer belt 20 that is opposed to and contacts the surface of the image carrier 10 and whose periphery is movably supported is provided.
A primary transfer roll 16 is provided at a position facing the image carrier 10 so as to contact the inner peripheral surface of the intermediate transfer belt. By applying a bias voltage between the primary transfer roll and the image carrier, the developed toner image on the image carrier is primarily transferred onto the intermediate transfer belt 20.

A drive roll 22 driven by a motor 21 is provided inside the endless intermediate transfer belt 20.
And two driven rolls 23 and 24, and a transfer roll 30 for performing secondary transfer, and the intermediate transfer belt 20 is stretched around them by these. A pressure roll 31 is provided at a position facing the transfer roll 30 with the intermediate transfer belt 20 interposed therebetween. At a position along the intermediate transfer belt 20, an electromagnetic induction heating device 40 faces the inner surface of the belt. Is provided.

Next, the configuration of the image forming apparatus will be described in detail. The image carrier 10 has a photoreceptor layer on the surface of an electrically grounded cylindrical substrate, and is driven to rotate in the direction of arrow A shown in the figure. An organic photosensitive material, an amorphous selenium-based photosensitive material, an amorphous silicon-based photosensitive material, and the like are used for the photosensitive layer.

The developing unit 13 stores four toners of cyan, magenta, yellow, and black, respectively.
There are provided developing units 13C, 13M, 13Y and 13K, and each developing unit is rotatably supported so as to face the image carrier 10. Each of the developing units 13C, 13M, 13Y,
13K, a toner layer is formed on the surface of the image carrier 10K.
And a developing roll for transporting the developing roll to a position facing the developing roller.

The intermediate transfer belt 20 has three layers: a base layer made of a sheet member having high heat resistance, a conductive layer (electromagnetic induction heating layer) laminated thereon, and a surface release layer which is the uppermost layer. Alternatively, it is composed of four layers: a base layer, a conductive layer laminated thereon, an elastic layer, and a surface release layer which is the uppermost layer. The base layer is preferably a semiconductive member having a thickness of 10 μm to 100 μm, for example, polyester, polyethylene terephthalate, polyether sulfone,
A resin in which a conductive material such as carbon black is dispersed in a resin having high heat resistance represented by polyamide or the like is suitably used. The reason why the conductive material is dispersed in the base layer is to take into account the electrostatic transferability when the toner image is primarily transferred.

The conductive layer is, for example, a layer of iron or cobalt or a metal layer of nickel, copper, chromium or the like formed by plating to a thickness of 1 μm to 50 μm. The elastic layer is formed of silicone rubber with a thickness of 30 μm to 500 μm. The surface release layer has a thickness of 0.1 μm
It is preferably a sheet or coat layer having a high releasability of 30 μm, for example, a tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, a polytetrafluoroethylene-silicone copolymer, or the like is used.

The electromagnetic induction heating device 40 includes a transfer roll 3
The intermediate transfer belt 20 is heated upstream of the position where the pressure roller 31 and the pressure roller 31 are provided to heat the intermediate transfer belt 20 to heat and fuse the toner image carried on the intermediate transfer belt. As shown in FIGS. 1 and 2, the electromagnetic induction heating device 40 includes an electromagnetic induction coil 50 and a power supply unit 46 for applying a high-frequency alternating current to the electromagnetic induction coil.
The main part is composed of an output control unit 47 for controlling a switching cycle when supplying a high-frequency current to the electromagnetic induction coil, and an insulating film 49 surrounding these devices and the space formed by them.

As shown in FIG. 2A, the electromagnetic induction coil 50 is supported by a pedestal 41 having a rectangular plate shape having a long side substantially in the width direction of the intermediate transfer belt. Pedestal 41
Is made of heat-resistant polycarbonate, etc.
A ferrite core 42 also extending in the width direction of the belt is attached to the center of the lower surface of the base 1.
A large number of coil windings 43 are wound along the lower surface of 1 to form an exciting coil.

A plurality of ferrite plates 44 are arranged on the upper surface of the pedestal 41 at predetermined intervals in a direction intersecting with the belt width direction. Ferrite is a ferromagnetic material, and the plate 44 serves as a path for magnetic flux generated by the coil, and reduces the influence on peripheral devices due to the divergence of the strong magnetic field. Further, it also serves as an insulator that blocks leakage current from the electromagnetic induction coil so as not to flow to peripheral devices of the power supply unit 46 and the output control unit 47.

A schematic diagram of the entire electromagnetic induction heating device 40 is as shown in FIG. 1, in which a power supply unit 46 is arranged so as to be close to one side end of the electromagnetic induction coil 50. The harness 45 is made as short as possible. In addition, an output control unit 47 is arranged close to the other side end and faces the power supply unit 46,
As a whole, the electromagnetic induction coil is arranged so as to form a space surrounded on three sides by the back surface of the pedestal 41, the power supply unit 46, and the output control unit 47.

As shown in FIG. 3, each of the power supply unit 46 and the output control unit 47 has a shape that is long in the width direction of the intermediate transfer belt 20, and a cooling fan 48 is provided near one end. The power supply unit 46, the output control unit 47, and the electromagnetic induction coil 50
A flow of air is formed in the space surrounded by, and the heat trapped in the basket is forcibly discharged. The electromagnetic induction heating device 40 includes a power supply unit 46 and an output control unit 47.
And the periphery thereof are covered with an insulating film 49 to prevent electrical leakage to the intermediate transfer belt 20.
As the insulating film 49, polyimide having a thickness of 50 μm to 400 μm can be used.

From the power supply unit 46 to the electromagnetic induction coil 50
When a high-frequency AC voltage is applied to the
A magnetic field indicated by an arrow H repeats annihilation generation.
The electromagnetic induction coils 50 are arranged at intervals of about 1 mm to 3 mm so as to surely cross the conductive layer of the intermediate transfer belt 20 so that the magnetic field H faces the surface of the intermediate transfer belt 20.

The transfer roll 30 and the pressure roll 31 are pressed against each other with the intermediate transfer belt 20 interposed therebetween, and the recording paper 60 supplied from a paper tray (not shown) is transferred to the intermediate transfer belt 20 and the pressure roll 31. And press between them. Thereby, the intermediate transfer belt 2
The toner image melted on the sheet 0 is pressed against the recording paper 60, and the secondary transfer and the fixing are simultaneously performed. The pressure roll 31 can be retracted backward while the toner images of the respective colors are superimposed on the intermediate transfer belt 20.

Next, the operation of the image forming apparatus will be described. First, the surface of the image carrier 10 is negatively and substantially uniformly charged by the charging roll 11, and then image light is emitted from the exposure device 12 to form a latent image on the surface of the image carrier 10. Thereafter, when the latent image on the image carrier 10 passes through a position facing the developing device 13Y containing yellow toner,
The toner having a negative charge is selectively transferred to the image carrier 10 in the developing electric field, and the latent image is visualized. The image light irradiates the image area, and the charging roll 1
The toner having the same polarity as the surface potential (minus) of the image carrier 10 charged in step 1 is transferred to the exposed portion of the image carrier 10 to form a toner image.

This toner image is conveyed to a position facing the intermediate transfer belt 20 by the orbital movement of the image carrier 10. In the primary transfer section where the intermediate transfer belt 20 is in contact with the image carrier 10, an electric field is formed between the two, whereby the toner image on the image carrier 10 is electrostatically attracted onto the intermediate transfer belt 20. Then, the primary transfer of the toner image is performed. This toner image is conveyed by the orbital movement of the intermediate transfer belt 20.

On the other hand, the toner remaining on the image carrier 10 after the primary transfer is removed by the cleaning device 14, the surface of the image carrier 10 is electrically initialized by the charge removing exposure device 15, Move to the opposing position. Thereafter, similarly, magenta, cyan, and black toner images are sequentially formed and transferred onto the intermediate transfer belt 20 in a superimposed manner.

The toner image superimposed on the intermediate transfer belt 20 is conveyed to a position facing the electromagnetic induction heating device 40 by the orbital movement of the intermediate transfer belt 20. Then, the toner is heated and melted by the driving of the electromagnetic induction heating device 40, and is conveyed to a nip portion including the transfer roll 30 and the pressure roll 31. The recording paper 60 is conveyed from a paper tray (not shown) and sent between the intermediate transfer belt 20 and the pressure roll 31 in synchronization with the conveyance timing. Thus, the fused toner image is pressed against the recording paper 60, and the secondary transfer and the fixing are performed simultaneously.

The electromagnetic induction heating device 40 generates a fluctuating magnetic field H so as to cross the conductive layer of the intermediate transfer belt 20. As a result, the conductive layer has a fluctuating magnetic field H so as to prevent the magnetic field from changing. An eddy current is generated. Most of this eddy current flows concentratedly on the side of the conductive layer on the side of the exciting coil due to the skin effect, and generates heat in proportion to the resistance value of the conductive layer. As a result, the toner image carried on the intermediate transfer belt 20 is heated and melted.

At this time, since the entire electromagnetic induction heating device 40 integrally formed is covered with the insulating film 49, the insulation resistance between the coil winding 43 and the intermediate transfer belt 20 is maintained, and the coil winding 43 is maintained. Leakage of current from the line 43 to the intermediate transfer belt 20 is prevented. Thereby, damage and deterioration of the conductive layer of the intermediate transfer belt 20 are avoided.
In addition, the durability of the device is increased, and long, stable, and efficient heating is performed without generating uneven heat generation.

[0039]

As described above, in the image forming apparatus according to the present invention, since the power supply device is brought close to the back side of the electromagnetic induction coil and the harness is shortened, the generation of noise can be reduced. . Further, the components related to the electromagnetic induction heating are housed inside the endless intermediate transfer belt, so that the size of the entire apparatus can be reduced.

Further, by arranging the electromagnetic induction coil, the power supply unit and the control unit as in the present invention, the cooling of the electromagnetic induction coil and the cooling of the heating element of the power supply unit, which are conventionally performed separately, can be performed by one cooling fan. At the same time, and the cost of the entire apparatus can be reduced. Also, since a ferromagnetic and electrically insulating member is disposed between the back of the electromagnetic induction coil, that is, the power supply device, etc., a shielding magnetic path is formed around the coil. In addition, malfunction of peripheral devices due to a high-frequency magnetic field can be effectively prevented.

In the electromagnetic induction heating apparatus according to the most preferred embodiment of the present invention, the insulating film is formed so as to surround the electromagnetic induction coil and the power supply unit which are compactly formed and the space formed therebetween. Since it is provided, it is possible to prevent electrical leakage from the electromagnetic induction coil to peripheral devices and the intermediate transfer belt, and as a result, insulation between the intermediate transfer belt and the conductive layer of the intermediate transfer belt can be maintained. Can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention.

2 is a schematic perspective view and a schematic sectional view of an electromagnetic induction coil used in the image forming apparatus shown in FIG.

FIG. 3 is a side view of an electromagnetic induction heating device used in the image forming apparatus shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Image carrier 11 Charge roll 12 Exposure device 13 Developing unit 14 Cleaning device 15 Static elimination exposure device 16 Primary transfer roll 20 Intermediate transfer belt 21 Motor 22 Driving roll 23, 24 Follower roll 30 Transfer roll 31 Pressure roll 40 Electromagnetic induction heating device 41 Base 42 Core 43 Coil winding 44 Ferrite plate 45 Harness 46 Power supply unit 47 Output control unit 48 Cooling fan 49 Insulating film 50 Electromagnetic induction coil 60 Recording paper

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 2H032 AA05 AA15 BA09 BA21 BA23 CA02 CA13 2H033 AA32 AA35 BA11 BA29 BB28 BE03 BE06 BE09 CA20 CA37 2H078 AA21 CC06 DD51 DD53 DD56 EE27 3K059 AA08 AA10 AB10 AD20 AD24 AD32 AD32 AD32

Claims (5)

[Claims] An image carrier on which a latent image due to a difference in electrostatic potential is formed on a surface; a developing device for visualizing the latent image on the image carrier by transferring toner to the latent image; An endless belt, comprising: an intermediate transfer belt on which a toner image formed on the image carrier is primarily transferred onto a peripheral surface; and a heating device for heating and melting the toner image on the intermediate transfer belt. An image forming apparatus for simultaneously performing secondary transfer and fixing by pressing a toner image melted on the intermediate transfer belt onto a recording sheet, wherein the intermediate transfer belt has a conductive layer. The heating device includes: an electromagnetic induction coil provided to face an inner surface of the intermediate transfer belt; and a power supply device for supplying a high-frequency current to the electromagnetic induction coil. Provided close to the side An image forming apparatus. 2. The power supply device according to claim 1, wherein a portion from which a conductive wire for supplying a high-frequency current to the electromagnetic induction coil is drawn,
The fan is arranged near the electromagnetic induction coil, another portion is arranged so as to form a space between the electromagnetic induction coil and the back surface of the electromagnetic induction coil, and a fan for blowing air into the space is provided. 2. The image forming apparatus according to 1. 3. A control unit for controlling a switching cycle (ON time) when supplying a high-frequency current from the power supply device to the electromagnetic induction coil is arranged to surround the space. 3. The image forming apparatus according to 2. 4. The device according to claim 1, wherein a member made of a ferromagnetic material and electrically insulating is interposed between the electromagnetic induction coil and the power supply device. The image forming apparatus according to claim 2 or 3. 5. An insulating film is provided so as to surround the electromagnetic induction coil, the power supply device, and a space formed therebetween.
Alternatively, the image forming apparatus according to claim 3.