JP2004191790A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which prevents image deformation by moisture absorption in the image forming device in which an amorphous silicon photoreceptor is used. <P>SOLUTION: The image forming apparatus is equipped with: a photoreceptor 11; a plurality of developing means 15 to 18 which are provided around the photoreceptor 11 in order to successively develop a plurality of electrostatic latent images formed on the surface of the photoreceptor 11 with respective colors of toner; an intermediate transfer body 20 which is arranged so as to rotate while keeping in contact with the photoreceptor 11 and which carries a full color toner image by successively transferring toner images of respective colors which are successively formed on the surface of the photoreceptor for every color; and a transfer means for transferring the full color toner image existing on the surface of the intermediate transfer body 20 onto a form. A heating means 30 whose maximum heating temperature is equal to or lower than 90°C is provided under the intermediate transfer body 20. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a full-color image forming apparatus, and more particularly to an image forming apparatus in which a plurality of developing devices are arranged around a photoconductor.
[0002]
[Prior art]
2. Description of the Related Art A full-color image forming apparatus employing a method of sequentially transferring toner images of respective colors formed on a photosensitive drum to an intermediate transfer member and transferring a color image formed thereon to paper has been widely used. Devices using an amorphous silicon photoreceptor for the purpose of extending the life of the photoreceptor are also increasing. However, the amorphous silicon photoreceptor easily adsorbs moisture in the air, and when moisture adheres to the photoreceptor, so-called image deletion easily occurs. Therefore, it is necessary to always heat the photoreceptor itself to prevent the adhesion of moisture. Met.
[0003]
On the other hand, a small amount of moisture is generated from the paper transport path located below the intermediate transfer body and the fixing unit at the most downstream side thereof, and the moisture rises around the intermediate transfer body and forms around the silicon photoreceptor. Trace moisture adsorbed on the surface of the intermediate transfer body due to high humidity is transferred to the photoreceptor side at the contact point with the photoreceptor. Is stronger.
[0004]
Patent Document 1 below discloses an example in which the intermediate transfer body itself is heated to remove the influence of moisture in the image forming apparatus. The disclosed technique is an image forming apparatus having a configuration in which a heater 41 is provided on a side of an intermediate transfer drum 50 as shown in FIG. That is, the intermediate transfer drum 50 is rotatably supported by the intermediate transfer drum support member 52, and is in pressure contact with the photosensitive drum 60 at a predetermined pressure at the primary transfer nip T1. The secondary transfer belt 55 extended and suspended between the secondary transfer roller 56 and the driving roller 57 is provided so as to be freely movable toward and away from the intermediate transfer drum 50 by the rotation of a cam 59 contacting a coil spring 58. It is brought into contact with the photosensitive drum 60 at the time of the next transfer.
[0005]
Near the outer periphery of the intermediate transfer drum 50, a temperature sensor 40 for measuring the ambient temperature around the intermediate transfer drum 50 and a heater 41 for heating the outer periphery of the intermediate transfer drum 50 along the longitudinal direction are arranged. . The temperature sensor 40 is installed near the primary transfer nip T1. The heater 41 is installed close to the surface of the intermediate transfer drum 50 and parallel to the rotation shaft 51 of the intermediate transfer drum 50. Temperature information around the intermediate transfer drum 50 measured by the temperature sensor 40 is output to the control device 42, and the control device 42 performs heat control (on / off control) of the heater 41 based on the input temperature information.
[0006]
It is conceivable to use this technique in a full-color image forming apparatus using the above-described amorphous silicon photoconductor. However, in this prior art, since the heater is provided on the side of the photoreceptor which is the intermediate transfer drum, the heat generated by the heater does not spread to the opposite side of the intermediate transfer drum, and the current is repeatedly turned on and off. In this case, there is a problem that the ambient temperature fluctuates easily and the drum sensitivity is not stable.
On the other hand, a transfer roller made of rubber is used as a transfer unit for transferring the toner on the surface of the intermediate transfer drum onto a sheet. However, in a low-temperature environment, the insulating property is increased, and a transfer current value generated when a transfer voltage is applied is reduced. There is a problem that the transfer performance is not sufficient and the transfer performance is deteriorated.
[0007]
[Patent Document 1]
JP 2000-310910 A
[Problems to be solved by the invention]
Therefore, an object of the present invention is to solve the above problems, and a first object of the present invention is to prevent an image flow due to moisture adsorption in an image forming apparatus using an amorphous silicon photoreceptor. An image forming apparatus is provided.
Further, a second object of the present invention is to provide an image forming apparatus using an amorphous silicon photoreceptor, wherein the image forming apparatus is configured to prevent an image flow due to moisture adsorption propagating through an intermediate transfer member.
Still another object of the present invention is to provide an image forming apparatus using a transfer roller, in which transfer performance does not decrease even in a low temperature environment.
Further, a fourth object of the present invention is to provide an image forming apparatus capable of saving the number of parts by providing a heater for keeping the temperature of the transfer roller and a heater for preventing the image from flowing.
[0009]
[Means for Solving the Problems]
The above object of the present invention can be achieved by the following inventions.
According to an aspect of the present invention, there is provided a photoconductor, a plurality of developing units provided around the photoconductor for sequentially developing a plurality of electrostatic latent images formed on the photoconductor surface with toners of respective colors, and a photoconductor. And an intermediate transfer body that is arranged so as to be in contact with and circulates, and that carries a color toner image by sequentially transferring toner images of each color sequentially formed on the surface of the photoreceptor, and a color toner on the surface of the intermediate transfer body. An image forming apparatus comprising: a transfer unit for transferring an image onto a sheet; and a separation unit provided downstream of the transfer unit in the sheet conveyance direction with respect to the transfer unit for separating the sheet from the surface of the intermediate transfer body. A heater having a power consumption of 4 to 20 W is provided below the intermediate transfer member.
[0010]
According to the invention of claim 1, since the heater is located below the intermediate transfer body, the surface of the intermediate transfer body and the surface of the photoconductor in contact with the intermediate transfer body are heated by convection of warm air from the heater. To prevent image absorption by preventing moisture adsorption. Moreover, since the heater means has a low output and a surface temperature of 90 ° C. at the maximum, soft heating can be performed, and on / off control is not required.
[0011]
Further, according to a second aspect of the present invention, in the image forming apparatus according to the first aspect,
The transfer unit is a transfer roller located below the intermediate transfer member, and the heater unit is located below the separation unit.
According to the second aspect of the present invention, since the heater is located below the transfer roller, the transfer roller is heated, so that transfer failure due to increased insulation of the roller rubber in a low temperature environment can be prevented. In addition, since the heater means is located below the separating means adjacent to the transfer roller and not directly below the transfer roller, overheating of the transfer roller is avoided.
[0012]
Further, according to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the heater unit is always turned on during non-image formation.
According to the third aspect, since the heating control is not repeated but on and off control of the heater means and is always on, it is not necessary to form a complicated control circuit.
[0013]
Further, according to a fourth aspect of the present invention, in the image forming apparatus according to the first to third aspects, the heater is a plate-shaped heater extending in a longitudinal direction of a rotation axis of the intermediate transfer body. And
According to the fourth aspect of the present invention, the rising airflow from the heater comes into contact uniformly over the entire length of the intermediate transfer member and the photosensitive member in the axial direction, so that the temperature is kept uniform and soft.
[0014]
Further, according to a fifth aspect of the present invention, in the image forming apparatus of the first to fourth aspects, the photosensitive member is a photosensitive drum made of amorphous silicon.
According to the fifth aspect of the present invention, the amorphous silicon photoreceptor positioned above the intermediate transfer member is also exposed to a heated updraft from the lower heater means to adsorb moisture to the surface of the amorphous silicon photoreceptor. To prevent
[0015]
Further, according to a sixth aspect of the present invention, there is provided a photoreceptor, a plurality of developing means provided around the photoreceptor for sequentially developing a plurality of electrostatic latent images formed on the photoreceptor surface with respective color toners, An intermediate transfer member that is arranged so as to abut against the body and rotates, and that sequentially transfers toner images of each color formed sequentially for each color to the surface of the photoreceptor to carry as a full-color toner image; and a color on the surface of the intermediate transfer member. An image forming apparatus comprising: a transfer unit configured to transfer a toner image onto a sheet; and a separation unit provided downstream of the transfer unit in a sheet conveying direction with respect to the transfer unit to separate the sheet from the surface of the intermediate transfer body. Wherein a heater having a maximum surface temperature of 40 to 90 ° C. or lower is provided below the intermediate transfer member.
According to the sixth aspect of the present invention, the surface temperature of the heater means located below the intermediate transfer member is set to 40 ° C. or higher, so that moisture adsorption on the surface of the intermediate transfer member or the photosensitive member is suppressed, and Effectively prevent flow.
Further, by setting the surface temperature of the heater means to 90 ° C. or lower, soft heating is possible, and spot-like stains on a printed image due to toner adhering to the surface of a photoreceptor or an intermediate transfer body in a spot-like manner are prevented. . Moreover, on / off control is not required.
As described above, each configuration of the present invention described in claims 1 to 6 is applied to an image forming apparatus having a photosensitive drum having a photosensitive member made of amorphous silicon to prevent image flow due to moisture adsorption. It is suitable.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be illustratively described in detail with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention, but are merely illustrative examples. It's just
[0017]
FIG. 1 is a schematic sectional view of an image forming apparatus showing an embodiment of the present invention. In FIG. 1, an image forming apparatus 1 includes a photoconductor 11, an exposure unit 13, a charger 12, a cleaning unit 19, developing units 15 to 18 disposed around the photoconductor 11, and a drum-shaped intermediate transfer body 20 (hereinafter referred to as intermediate transfer). And a transfer roller 24, a separation unit 22, a cleaning unit 23, a sheet cassette 3, a pair of registration rollers 4, a conveyance belt 5, a vertical conveyance path 7, a discharge tray 8, and the like. The paper transport system to be fixed, the fixing device 6 disposed between the transport belt 5 and the vertical transport path 7, and the plate-shaped heater 30 disposed below the transfer roller 24 and the separation unit 22 have a predetermined positional relationship. It is arranged in the housing 2.
[0018]
The photoconductor 11 is a drum-shaped photoconductor having a photoconductor made of amorphous silicon (a-Si) (hereinafter, referred to as a photoconductor drum). A unit 13, developing units 15, 16, 17, and 18 having developing sleeves 15a, 16a, 17a, and 18a, an intermediate transfer drum 20, and a cleaning unit 19 are arranged. The developing sleeves 15a, 16a, 17a, and 18a include a carrier and Is a mixture of 5 parts by weight of black, yellow, magenta, and cyan toners having a positive triboelectric charge polarity and a volume average particle diameter of 8 μm and 100 parts by weight of a ferrite carrier having a weight average particle diameter of 70 μm. And the developing sleeves 15a, 16a, 17a, and 18a, the intermediate transfer drum 20, and the photosensitive drum 11. Each of them rotates in the direction of arrow A in the figure to form an image.
[0019]
The charging unit 12 uniformly charges the amorphous silicon (a-Si) photosensitive member of the photosensitive drum 11 to about +400 [V], and irradiates the exposure unit 13 with light 14 corresponding to image data. 11 is performed to form an electrostatic latent image. At this time, the surface potential of the a-Si photosensitive member after exposure is about +10 [V].
[0020]
An alternating electric field (Vdc = 160 [V], Vpp = 1.0 [kV], f = 3.6 [kHz]) acts between the photoconductor drum 11 and the developing device sleeve 15a, and the The exposed portion is developed with a toner image. Here, the toner image by the developing device 15 is transferred to the intermediate transfer drum 20 by a potential difference of about −100 to −800 [V], and then the toner image by the developing device 16 is transferred to the intermediate transfer drum 20. 17, after the image is repeatedly transferred to the intermediate transfer drum 20 by the developing device 18 and then transferred onto the paper P, a color toner image is formed. Each time the transfer of the toner of each color to the intermediate transfer drum 20 is completed, the unremoved residual toner on the surface of the photosensitive drum 11 is removed by the cleaning unit 19 and the photosensitive drum 11 returns to a clean state.
[0021]
As described above, as the toner image is formed on the surface of the intermediate transfer drum 20, and the leading end thereof approaches the transfer position, the paper P stored in the paper feed cassette 3 is moved to the arrow B in the drawing. And passes through the transfer area between the transfer roller 24 and the intermediate transfer drum 20 with the timing adjusted by the registration roller pair 4. At this time, the paper P is transferred the toner image on the surface of the intermediate transfer drum 20, is separated by AC in the separation unit 22, is conveyed on the conveyance belt 5, and reaches the fixing unit 6. The sheet P on which the toner image has been fixed by passing through the fixing unit 6 is discharged to a sheet discharge tray 8 via a vertical conveyance path 7. After the toner image is transferred to the sheet P, the transfer toner is removed from the intermediate transfer drum 20 by the cleaning unit 23, and the intermediate transfer drum 20 returns to a clean state. The cleaning units 19 and 23 are composed of a cleaning blade or a fur brush or the like.
[0022]
Below the separation unit 22 and the transfer roller 24, a planar heater 30 is mounted in the axial direction of the photoconductor 11 so as to have a length substantially equal to the length of the photoconductor. Therefore, the plate heater 30 heats them from below the intermediate transfer drum 20 and the transfer roller 24.
The plate heater 30 is made by Kurabe Co., Ltd., and its rated power is 10W. The plate heater 30 is controlled to be turned on and off by a control circuit (not shown). In the embodiment of the present invention, the plate heater 30 is controlled to be turned on during non-image formation, including when the power switch of the image forming apparatus main body is turned off. Is what it is.
[0023]
Next, the configuration of the plate heater 30 will be described with reference to FIGS. FIG. 2 is a plan view of the plate heater 30 as viewed from above, FIG. 3 is a configuration diagram of a die gel heater 01 which is a heater wire provided inside the plate heater 30, and FIG. It is sectional drawing which looked at 30 in the direction of AA. The unit of the numbers in FIG. 2 is mm.
[0024]
The plate-shaped heater 30 is formed by bending the central portion of the die gel heater 01 into a U-shape and extending the portions reaching both ends in parallel at an interval of 10 mm to each other, and connecting both ends thereof to the connector 03 having a length of 50 mm (Nippon Terminal 29082- 1) and the lead wire 02 is connected to the terminal terminal 07 covered with the housing 08 except for the connection opening. The outer periphery of the connector 03 is covered with an insulating tube 04 made of a silicone rubber tube.
The lead wire 02 is composed of a silicon rubber-coated glass braided electric wire. The die gel heater 01 and the 45 mm long portion of the connector 03 connected to both ends thereof, except for the 5 mm end portion, are sandwiched between an aluminum foil 05 having a thickness of 0.04 mm and a double-sided tape 06. The aluminum foil 05 side is opposed to the intermediate transfer drum side, and the double-sided tape 06 side is affixed to the base portion of the apparatus main body (not shown). The aluminum foil 05 has a total length of 210 mm and a width of 30 mm, and the total length direction matches the axial direction of the intermediate transfer drum. Due to the good heat transfer characteristics of the aluminum foil 05, the heat generated by the current flowing from the resistance wire b of the die gel heater 01 is propagated in the surface direction so that uniform and soft heating is performed.
[0025]
The power switch of the image forming apparatus 1 is turned off under an environment of 20 ° C. and 50%, and the plate heater 30 is left energized for 10 hours, and the central portion is sandwiched between the die gel heaters provided inside the plate heater. When the surface temperature of the aluminum was measured by defining it as the surface temperature of the plate-like heater, it was 70 ° C., and the surface temperature of the photoconductor around the nip portion between the intermediate transfer drum and the photoconductor was 40 ° C.
The surface temperature of the plate heater was 40 ° C. in the case of the same configuration as in the above embodiment except that the rated output of the die gel heater 01 was 4 watts, and the surface temperature of the photoconductor around the nip portion between the intermediate transfer drum and the photoconductor Was 30 ° C.
Further, the surface temperature of the plate-shaped heater in the case of the same configuration as in the above embodiment except that the rated output of the die gel heater 01 was 20 watts was 90 ° C., and the surface temperature of the photosensitive member around the nip portion between the intermediate transfer drum and the photosensitive member Was 50 ° C.
[0026]
When using a plate heater having a rated output of 4 to 20 watts of the die gel heater 01, the image forming apparatus 1 is left for 10 hours in a high-temperature and high-humidity environment of 30 ° C. and 90% with the power switch turned off. Even when the power switch was turned on and an image was output, no image deletion phenomenon occurred and good image quality was obtained.
[0027]
The surface temperature of the plate-shaped heater was 30 ° C. in the same manner as in the above embodiment except that the rated output of the die gel heater 01 was 2 watts, and the surface temperature of the photosensitive member around the nip portion between the intermediate transfer drum and the photosensitive member was 25 ° C. ° C. After leaving the image forming apparatus 1 in a high-temperature and high-humidity environment of 30 ° C. and 90% for 10 hours with the power switch turned off, when the power switch was turned on to output an image, an image deletion phenomenon occurred.
[0028]
The surface temperature of the plate-shaped heater in the same manner as in the above embodiment except that the rated output of the die gel heater 01 was 30 watts was 110 ° C., and the surface temperature of the photosensitive member around the nip portion between the intermediate transfer drum and the photosensitive member was 60 °. ° C. When the image forming apparatus 1 is left in a high-temperature and high-humidity environment of 30 ° C. and 90% for 10 hours with the power switch turned off, and then the power switch is turned on to output an image, the toner spots on the photoconductor and the intermediate transfer drum. Image deterioration due to fusion in a shape was observed.
[0029]
【The invention's effect】
As described above, according to the image forming apparatus of the present invention, since the diegel heater 30 serving as a heater is disposed below the intermediate transfer drum 20, the intermediate transfer is performed by convection of warm air from the diegel heater 30. The surface of the drum 20 and the surface of the photosensitive drum 11 that is in contact with the intermediate transfer drum 20 can be heated to prevent the adsorption of moisture, and the image flow due to the adsorption of moisture can be effectively prevented.
[0030]
In addition, since the surface temperature of the plate heater 30 is 90 ° C. at the maximum, soft heating is possible, and there is no need to perform fine on / off control with a temperature sensor or the like. ON control is sufficient, and the control circuit can be simplified without requiring a complicated control circuit.
[0093]
Further, since the die gel heater 30 is disposed below the intermediate transfer drum 20 and below the separating means adjacent to the transfer roller 24, the transfer roller 24 can also be softly heated from obliquely below. This has the effect of preventing transfer failure due to increased insulating properties of the roller rubber in a low-temperature environment, does not require a separate heater for heating the transfer roller, and does not increase the number of parts.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to the present invention.
FIG. 2 is a plan view of the plate heater 30 as viewed from above. FIG. 3 is a configuration diagram of a die gel heater 01 which is a heater wire provided inside the plate heater 30.
FIG. 4 is a cross-sectional view of the plate-shaped heater 30 viewed in the direction of AA.
FIG. 5 is a diagram illustrating a configuration of a conventional image forming apparatus.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 image forming apparatus 2 housing 3 paper feed cassette 4 registration roller pair 5 transport belt 6 fixing unit 7 vertical transport path 8 Paper discharge tray 11 Photoconductor 12 Charger 13 Exposure unit 14 Exposure light 15, 16, 17, 18 Developing devices 15a, 16a, 17a, 18a Developing Sleeve 19: Cleaning unit 20: Intermediate transfer member 22: Separation unit 23: Cleaning unit 24: Transfer roller 30: Digel heater

Claims (6)

A photoreceptor,
A plurality of developing means provided around the photoreceptor for sequentially developing a plurality of electrostatic latent images formed on the photoreceptor surface with each color toner;
An intermediate transfer body that is in contact with the photoconductor and is arranged as it rotates, and that carries a color toner image by sequentially transferring toner images of each color sequentially formed for each color on the photoconductor surface,
Transfer means for transferring the color toner image on the surface of the intermediate transfer member onto paper,
An image forming apparatus, comprising: a separating unit provided on the downstream side in the sheet conveying direction with respect to the transfer unit to separate the sheet from the intermediate transfer body surface;
An image forming apparatus comprising a heater having a power consumption of 4 to 20 W provided below an intermediate transfer member. 2. The image forming apparatus according to claim 1, wherein the transfer unit is a transfer roller located below the intermediate transfer body, and the heater unit is located below the separation unit. 3. The image forming apparatus according to claim 1, wherein the heater unit is always turned on during non-image formation. The image forming apparatus according to claim 1, wherein the heater is a plate-shaped heater extending in a longitudinal direction of a rotation axis of the intermediate transfer body. 5. The image forming apparatus according to claim 1, wherein the photosensitive member is a photosensitive drum made of amorphous silicon. A photoreceptor,
A plurality of developing means provided around the photoreceptor for sequentially developing a plurality of electrostatic latent images formed on the photoreceptor surface with each color toner;
An intermediate transfer body that is in contact with the photoconductor and is arranged as it rotates, and that carries a color toner image by sequentially transferring toner images of each color sequentially formed for each color on the photoconductor surface,
Transfer means for transferring the color toner image on the surface of the intermediate transfer member onto paper,
A separating unit provided downstream of the transfer unit in the sheet conveying direction with respect to the transfer unit to separate the sheet from the surface of the intermediate transfer body,
An image forming apparatus comprising: a heater having a maximum surface temperature of 40 to 90 ° C. below an intermediate transfer member.

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