JP2001092274A - Image-forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-quality image by preventing the deterioration of image quality caused by toner scattering and discharge and stably removing residual toner on an intermediate transfer body over a long term, in the case of secondarily transferring a toner image on the intermediate transfer body. SOLUTION: A cleaning belt 14, stretched and laid over two supporting rolls 23 and 24, is provided on the downstream side of a position, where the toner image on an intermediate transfer body 5 is secondarily transferred to a recording medium P, so that it comes in to contact with the transfer body 5. A cooling fan 15 is arranged inside a belt 14 and performs cooling, so that temperature at the downstream end of the contact area of the belt 14 with the transfer body 5 is equal to or under the temperature of the softening point of the toner. Thus, the toner remaining on the transfer body 5 after secondary transfer is cooled while it is moved in contact with the belt 14, whereby the mutual cohesive power of the toner is enhanced, and the toner is shifted stably to the belt 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a laser printer.
Image forming apparatus for temporarily transferring an unfixed toner image formed on an image carrier such as a photoreceptor to an intermediate transfer member, and transferring and fixing the unfixed toner image on the intermediate transfer member to a recording medium to form a recorded image About.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus such as a copying machine or a printer using an electrophotographic process, a toner image is formed on the surface of an image carrier such as a photoreceptor, and this toner image is
Transfer to a recording medium such as PC paper. Then, the recording medium on which the toner image has been transferred is guided to a fixing device, and the toner image is fixed on the recording medium to form a permanent image. Further, the apparatus for forming a color image includes a cylindrical transfer drum that adsorbs and conveys the recording medium, and transfers the toner image onto the recording medium every time a toner image is formed on the image carrier, thereby forming a multicolor image. The toner images are superimposed and fixed by a fixing device to form a color image.

However, in such an image forming apparatus, when a color image is formed, an unfixed toner image is directly transferred onto a recording medium and a plurality of color toner images are superimposed on each other. However, there is a disadvantage that the image quality of a color image is affected by many factors such as the transport characteristics of a recording medium with respect to an image carrier.

In order to solve such a defect, for example, Japanese Patent Publication No. 49-209 and Japanese Patent Application Laid-Open No. 62-206567 disclose a method in which a toner image formed on an image carrier is superimposed on an intermediate transfer member. 2. Description of the Related Art There has been proposed an image forming apparatus of a system in which a transferred and superimposed toner image is collectively transferred to a recording medium. As shown in FIG. 4, the image forming apparatus 100 includes an image carrier 101 having a surface on which a latent image is formed by irradiating image light after uniform charging.
Around the developing device 1, four developing devices 105, 106, 107, and 108 respectively storing toners of different colors, and an endless belt-shaped intermediate transfer member 102 that contacts the image carrier 101 downstream of the developing devices. A corona discharger 109 for transferring the toner image T formed on the image carrier 101 to the intermediate transfer member 102 by applying a voltage having a polarity opposite to that of the toner.
And Further, a transfer roll 111 to which a voltage having a polarity opposite to that of the toner is applied is disposed downstream of the intermediate transfer member 102 in a circumferential direction so as to be in contact with the intermediate transfer member 102. Body 10
2, the recording medium 103 is fed.

In such an image forming apparatus, the image carrier 1
01, a toner image T of a different color is formed by each developing device by one rotation.
Is primarily transferred electrostatically onto the intermediate transfer body 102 by
A plurality of color toner images are superimposed on the intermediate transfer member 102. Then, these toner images are secondarily electrostatically transferred from the intermediate transfer member 102 to the recording medium 103 by the transfer roll 111, and the toner images are fixed by a fixing device (not shown) to form a desired color image.

Since a plurality of color toner images transferred in a superimposed manner on the intermediate transfer member 102 are collectively transferred to the recording medium 103, when the toner images are superimposed on each other, the above-mentioned unstable image quality is affected. Factors can be eliminated,
There is an advantage that disturbance of an image and color shift can be effectively prevented.

However, in such an image forming apparatus, when the toner image T formed on the image carrier 101 is transferred to the intermediate transfer member 102 by the corona discharger 109, the line toner image is transferred in an overlapping manner. There is a problem that the line toner image superimposed thereon is scattered significantly. The cause is generally considered as follows. (1) A transfer electric field acts in a region of the transfer prenip portion where the image carrier and the intermediate transfer member are not in close contact with each other, and toner is scattered within minute intervals. (2) An electric discharge is generated when the image carrier and the intermediate transfer member are separated from each other, whereby the toner image is disturbed and the toner is scattered.

According to the investigation by the inventor of the present invention, it has been found that the phenomenon that the line toner image scatters significantly as described above becomes remarkable when a semiconductive material is used as the intermediate transfer member. This is considered to be due to the following phenomenon. If the intermediate transfer member has a low resistance, the transfer electric field easily spreads through the intermediate transfer member to the transfer prenip, and a strong transfer electric field acts in a region where the image carrier and the intermediate transfer member are not in close contact. For this reason, the scattering of the toner in the transfer prenip portion increases. In the case of a low-resistance intermediate transfer body, after a toner layer having a predetermined charge is electrostatically transferred to the intermediate transfer body,
The charge supplied from the corona discharger 109 is easily attenuated.
That is, the toner holding ability of the intermediate transfer member is low, and the toner scatters due to repulsion of the charges of the toner. Then, the effect of scattering the toner due to the attenuated charge is great.

Therefore, in order to prevent the toner from scattering on the intermediate transfer member 102, it is understood that the charge decay from the intermediate transfer member 102 should be prevented. However, the intermediate transfer member 10
When the toner image is secondarily transferred from the recording medium 2 to the recording medium 103, a high-transfer electric field is necessary because the high-density toner image transferred in a superimposed manner is transferred collectively. Therefore, when an intermediate transfer member whose charge is hardly attenuated is used, a discharge is generated between the intermediate transfer member and the recording medium, and image quality defects are likely to occur.

In order to prevent such image quality defects,
As described in JP-A-3-63758, it is desirable that the toner image is melted by heating and pressurizing means at the time of the secondary transfer, and the toner image is transferred in close contact with a recording medium. That is, by melting the toner image on the intermediate transfer body and transferring the toner image to the recording medium at a time, discharge between the intermediate transfer body and the recording medium can be prevented.

[0011]

However, such an image forming apparatus in which the toner image is melted and transferred by the heating and pressurizing means during the secondary transfer has the following problems. Generally, toner and extraneous matter remaining on the intermediate transfer member are removed by bringing a cleaning member into contact with the toner and sufficiently attaching the toner and extraneous matter. As these methods, for example, Japanese Patent Publication No. 4-4582
As described in Japanese Patent Application Publication No. 9-209, there is an image forming apparatus that utilizes a difference in adhesion between a transfer layer such as silicone rubber and a surface material of a cleaning member for a hot-melted toner. Further, as described in Japanese Patent Publication No. 4-9307, there is a method in which a resin compatible with toner is used as an adhesive layer on the surface of a cleaning member, and toner is adhered to the adhesive layer and removed.

However, according to the technique disclosed in Japanese Patent Publication No. 4-45829, as shown in FIG. 5, an image having a high toner coverage on the intermediate transfer member has a good cleaning efficiency, but an image having a low toner coverage is good. Cleaning efficiency is reduced. Therefore, there is a problem that a low-density image having a low toner coverage, such as a fog or a halftone image, cannot be cleaned. The cleaning member used here consisted of a 50 mm diameter cleaning roll in which an aluminum core was coated with an elastic layer made of silicone rubber having a hardness of 30 degrees and a thickness of 5 mm, and a small amount of silica (Si) was contained in the silicone rubber.
O ₂ ) is dispersed to enhance the toner adhesion.

The reason for such a cleaning efficiency can be considered as follows. That is, although the above technique has a weaker adhesive force between the cleaning member surface and the toner as compared with the technique described in Japanese Patent Publication No. Hei 4-9307, in a high-density image, when the toner is fused, It is considered that the adhesion between the surface of the cleaning member and the toner spreads over the entire image due to the cohesive force of the toners, and the cleaning can be performed with high efficiency. However, fogging and halftone images have a low toner particle density and a weak cohesive force between adjacent toner particles even when they are melted. Therefore, if the adhesion is not uniform, it is considered that poor cleaning is likely to occur.

On the other hand, in the technique described in Japanese Patent Publication No. 4-9307, the cleaning performance is deteriorated due to a decrease in the adhesive force and unevenness due to the deposits deposited on the surface of the adhesive layer.
For this reason, it is necessary to remove the adhered substance, but it is difficult to remove the adhered substance because the adhesive layer and the adhered substance are integrated, and the adhesive layer itself is damaged when removing.

Further, as a common problem of the above technology, FIG.
As shown in (1), there is a problem that the cleaning efficiency decreases with an increase in the number of prints. This is because if the cleaning member is used for a long period of time, the adhesion between the intermediate transfer body and the toner increases due to contamination and deterioration of the surface of the intermediate transfer body, and the adhesion strength between the toner and the toner becomes larger. It is thought to be done.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to prevent deterioration of image quality due to scattering and discharge of toner at the time of transfer. An object of the present invention is to provide an image forming apparatus capable of obtaining a high-quality image by stably removing the attached matter over a long period of time.

[0017]

Means for Solving the Problems To solve the above problems, the invention according to claim 1 has an endless peripheral surface,
The image carrier on which the toner image is formed by the toner adhering to the peripheral surface, and the endless peripheral surface are opposed to the image carrier, and are supported such that the peripheral surface can be moved around. An intermediate transfer member, a transfer device for transferring the toner image on the image carrier to the intermediate transfer member, and heating and pressing the toner image transferred on the intermediate transfer member, from the intermediate transfer member. An image forming apparatus having a heat transfer unit for secondary transfer onto a recording medium, wherein the endless peripheral surface is arranged so as to form a contact area with the peripheral surface of the intermediate transfer body and move in the same direction; A cleaning member that transfers residual toner on the transfer member and removes the toner from the intermediate transfer member; and a surface temperature of the intermediate transfer member and the cleaning member at a downstream end of a contact area between the intermediate transfer member and the cleaning member. Is Tona And an image forming apparatus which is set to be equal to or lower than the softening point temperature of the image forming apparatus.

In such an image forming apparatus, a cleaning member is provided in which the endless peripheral surface forms a contact area with the peripheral surface of the intermediate transfer body and moves in the same direction. After the transfer, the residual toner on the intermediate transfer member is brought into contact with the cleaning member, and is moved while keeping them in close contact. At this time, the surface temperature of the intermediate transfer body and the cleaning member at the downstream end of the contact area between the intermediate transfer body and the cleaning member is set so as to be equal to or lower than the softening point temperature of the toner. As a result, the cohesive force between adjacent toners increases, and the residual toner is transferred to the cleaning member and removed from the intermediate transfer member. For this reason, a low-density residual image having a low toner coverage on the intermediate transfer body, such as a fog or a halftone image, is also stably removed from the intermediate transfer body. Further, even if the adhesion to the toner increases due to contamination or deterioration of the intermediate transfer member, the toner can be stably removed without being separated between the toner layers due to a large cohesive force between the toners. As described above, it is possible to stably remove the deposits on the intermediate transfer member over a long period of time and obtain a high-quality image.

In order to set the temperature at the downstream end of the contact area between the intermediate transfer member and the cleaning member to be equal to or lower than the softening point temperature of the toner as described above,
It is desirable to provide a cooling means for cooling at least one of the intermediate transfer member and the cleaning member in a region where the intermediate transfer member contacts the cleaning member. With such a cooling means, it is possible to easily adjust the surface temperature at the downstream end of the contact area between the intermediate transfer member and the cleaning member so as to be equal to or lower than the softening point temperature of the toner. Further, the contact area between the cleaning member and the intermediate transfer member may be set to be long. Accordingly, heat is radiated while the intermediate transfer member and the cleaning member are moving, and the surface temperature of the intermediate transfer member and the cleaning member at the downstream end of the contact area can be adjusted to the above-mentioned temperature.

According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the cooling unit transfers heat in an area where the intermediate transfer body contacts the cleaning member on an upstream side of the area. It is assumed that the heat transport body is moved to By using such a heat transport body, the surface temperature at the downstream end of the contact area between the intermediate transfer body and the cleaning member can be stably cooled to the softening point temperature of the toner or lower, and the heat taken by the cooling can be contacted. It can be moved to the upstream side of the area and used for heating the toner image on the intermediate transfer member. Since the heat taken by the cooling can be reused in this way, energy can be saved.

According to a fourth aspect of the present invention, in the image forming apparatus of the first aspect, the cleaning member comprises:
An endless belt that is stretched around at least two rolls and moves around, and has a toner removing member that comes into contact with the peripheral surface of the endless belt and removes toner adhering to the peripheral surface. . In such an image forming apparatus, the length of the contact area can be arbitrarily adjusted by adjusting the interval between the two rolls by stretching the endless belt around at least two rolls and contacting the intermediate transfer body. Can be set. For this reason, the contact area can be formed in a wide range, and the temperature at the downstream end of the contact area between the intermediate transfer member and the cleaning member can be easily adjusted. Further, since the toner adhering to the endless belt is removed by the toner removing member, the surface state of the endless belt can be kept uniform for a long time, and stable cleaning performance can be obtained.

According to a fifth aspect of the present invention, in the image forming apparatus according to the first aspect, the cleaning member comprises:
The recording medium is sandwiched between the intermediate transfer member and pressed against the intermediate transfer member, and secondary transfer of the toner image from the intermediate transfer member to the recording medium is performed by pressing the cleaning member against the intermediate transfer member. Provided is an image forming apparatus characterized by using force. In such an image forming apparatus, the toner image is set to be secondarily transferred from the intermediate transfer member to the recording medium while the recording medium is sandwiched between the cleaning member and the intermediate transfer member. The cleaning of the surface of the intermediate transfer member around and the secondary transfer of the toner image on the intermediate transfer member can be performed simultaneously. In addition, since the press-contact between the toner image and the recording medium at the time of the secondary transfer is performed by using the press-contact force of the cleaning member, a dedicated cleaning member is not required, and the number of components can be reduced.

According to a sixth aspect of the present invention, in the image forming apparatus according to the first or fifth aspect, the heat transfer unit is provided at an upstream end of a contact area between the intermediate transfer body and the cleaning member. An image forming apparatus including a heating device that heats the intermediate transfer body so that the temperature of the surface of the intermediate transfer body is equal to or higher than the softening point temperature of the toner. In such an image forming apparatus, since the temperature of the surface of the intermediate transfer body at the upstream end of the contact area between the intermediate transfer body and the cleaning member is heated to the softening point temperature of the toner or more, the residual toner on the intermediate transfer body is And contacts the cleaning member heated to a temperature equal to or higher than the softening point of the cleaning member and strongly adheres to the cleaning member. In this state, the sheet is conveyed to the downstream side of the contact area with the cleaning member. Therefore, it is possible to increase the adhesive force between the residual toner and the cleaning member and obtain good cleaning performance.

According to a seventh aspect of the present invention, in the image forming apparatus according to the first aspect, the cleaning member comprises:
It is assumed that the intermediate transfer member has a surface layer having lower releasability than the peripheral surface. This surface layer is desirably made of a heat-meltable adhesive layer, for example, as described in claim 8. By providing a surface layer having a lower releasability than the peripheral surface of the intermediate transfer member on the surface of the cleaning member, residual toner on the intermediate transfer member easily adheres to the surface layer of the cleaning member. Stably removed. For this reason, the cleaning efficiency can be improved.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to an embodiment of the present invention described in claim 1, claim 2, claim 4, claim 6, or claim 7. The image forming apparatus includes an endless belt-shaped intermediate transfer member 5 whose peripheral surface is rotatably supported, and forms yellow, magenta, cyan, and black toner images at a position facing the intermediate transfer member 5. Four image forming units 10B, 1
0Y, 10M, and 10C are provided. Each image forming unit has a photosensitive drum 1 on which an electrostatic latent image is formed.
A charging device 2 for uniformly charging the surface of the photosensitive drum 1 around each of the photosensitive drums 1 and an exposure for forming a latent image by irradiating the photosensitive drum surface with image light. Device 3
A developing device 4 for selectively transferring toner to a latent image formed on the photosensitive drum to form a toner image; and a corona discharger for primarily transferring the toner image on the photosensitive drum onto the intermediate transfer body 5. An electric device 6 is provided.

On the inner side of the intermediate transfer member 5, support rollers 21 and 22 and the toner image on the intermediate transfer member
And a heat transfer roll 11 for secondary transfer. Further, between the support roll 22 and the heat transfer roll 11, a heating plate 8 for heating the toner image on the intermediate transfer body 5 is provided.
Are arranged so as to be close to the back side of the intermediate transfer body 5. Further, a pressure roll 8 is disposed at a position facing the heat transfer roll 11 via the intermediate transfer body 5. Further, a tray 13 for storing the recording medium P
Between the pressure roll 8 and the intermediate transfer body 5, a feed roller 12 that feeds the recording medium P at the same time as the leading edge of the image, and a recording medium P that has passed between them.
And a conveyor belt 20 for conveying the toner. Further, a cleaning belt 14 for cleaning the surface of the intermediate transfer member 5 and a cooling surface for cooling the surface of the intermediate transfer member 5 are provided on the downstream side in the circumferential direction of the intermediate transfer member 5 at a position facing the heat transfer roll 11 and the pressure roll 8. And a cooling fan 15.

The intermediate transfer member 5 is obtained by forming a surface layer having good releasability from toner on the surface of an endless belt-shaped base material. For example, polyimide resin and aramid resin having excellent heat resistance and rigidity On the surface of such a material, a fluororesin, silicone rubber, fluororubber or the like having a good toner release property is laminated. The electrical resistivity of the intermediate transfer body is set to 10 ¹³ Ω · c to prevent charge decay after primary transfer and to prevent charge diffusion to the transfer pre-nip, and to improve scattering of toner images.
m or more, and the front and back surface resistivity are adjusted to 10 ¹² to 10 ¹⁵ Ω / □. This is because when the volume resistivity is 10 ¹³ Ω · cm or more, the time constant of charge decay becomes 10 seconds or more, and
This is because the electric charges can be sufficiently retained even when rotating. Note that 1
If it exceeds ¹⁶ Ω / □, the toner image is scattered due to the generation of electric discharge when the photosensitive drum and the intermediate transfer member are separated, and the image quality is deteriorated. Here, the electrical resistivity of the above-mentioned intermediate transfer body is determined by connecting an HR100 probe (inner electrode diameter 50 mm, ring electrode inner diameter 53 mm, Mitsubishi Oil Chemical) to a high resistivity meter (Hiresta IP, manufactured by Mitsubishi Yuka). Then, a value of 1 minute after applying a voltage of 500 V between the electrodes is shown. Also, using the same probe, under the same conditions as above, conversion may be made from the measured values of a constant voltage power supply and a microammeter.

At the primary transfer position where the toner image is transferred to the intermediate transfer member 5, a corona discharger 6 is provided which prevents discharge to the transfer pre-nip by a transfer baffle 7, and the corona discharger 6 The non-fixed toner image on the photosensitive drum 1 is electrostatically attracted to the intermediate transfer member 5 by applying a voltage having a polarity opposite to the charging polarity of the intermediate transfer member 5. The intermediate transfer member 5 is arranged so as to be in contact with the photosensitive drum 1 of each image forming unit, and the unfixed toner image formed on each photosensitive drum 1 is transferred to the intermediate transfer member at this primary transfer position. The respective colors are superimposed on the surface of No. 5 and transferred. The primary transfer means is not limited to a corona discharger as long as it utilizes electrostatic force, and may be a conductive roll or a conductive brush to which a voltage is applied. The reason for using such an electrostatic force is that if the adhesive force of the toner due to heat or pressure is used for the primary transfer, the photosensitive drum is easily damaged.

The heating plate 9 comprises a known heater, and is set so as to heat from 150 degrees to 200 degrees. While the toner image on the intermediate transfer member 5 is being conveyed, the toner image is heated to a temperature higher than the softening point of the toner.

The heating transfer roll 11 has a built-in heat source such as a ceramic heater and a halogen lamp therein.
It is set to heat from 00 degrees to 150 degrees.
The heat transfer roll 11 has a surface hardness of 50 degrees to 9 degrees.
It is set to 0 degrees.

The cleaning belt 14 is stretched around supporting rolls 23 and 24 and is disposed so as to be in contact with the intermediate transfer member 5. A part of the cleaning belt 14 is heated via the intermediate transfer member 5. 11 is in contact. The cleaning belt 14 may have the same configuration as the intermediate transfer member 5, but in order to make the toner releasability worse than that of the intermediate transfer member 5, a surface in which a small amount of silica (SiO ₂ ) is dispersed in silicone rubber, for example, is used. A layer is provided. By providing such a surface layer, the adhesion to the toner becomes larger than that of the intermediate transfer member 5, and the cleaning efficiency can be improved. In addition, since a rigidity for preventing misregistration (color misregistration) of each color at the time of primary transfer as in the case of the intermediate transfer body 5 is not required, a 3 mm thick single layer of flexible silicone rubber is used. The adhesion to the body 5 is improved.

As another example, a cleaning belt may be coated with a polyester resin (glass transition point 66 ° C., melting point 110 °) which melts by heat and generates tackiness with toner. This is one embodiment of the invention described in claim 8. By providing such an adhesive layer,
Adhesive force with toner is increased, and residual toner can be satisfactorily removed from the intermediate transfer member. These adhesive layers are selected in consideration of compatibility with the toner, but butadiene and acrylic resins can also be used.

The cleaning belt 14 is adapted to move around the intermediate transfer member 5 to move around. Adhering to the intermediate transfer member 5 increases the adhesion in the contact area. A metal blade 16 is provided downstream of the cleaning belt 14 in the circumferential direction so as to contact the cleaning belt 14. This metal blade 16
Is intended to remove the toner that has been cleaned from the intermediate transfer member 5 to the cleaning belt 14. However, since the cleaned toner does not retransfer to the intermediate transfer member 5, complete removal performance is not required. .

The cooling fan 15 keeps the surface temperature of the cleaning belt 14 below the softening point temperature of the toner, for example, 1
It is set to cool to less than 00 degrees. Here, the softening point temperature of the toner is such that the viscosity of the toner is 1 × 10 ⁴
The temperature was defined as Pa · s. The measurement conditions are as follows. Using a flow tester CFT500C manufactured by Shimadzu Corporation, starting temperature 80 ° C to maximum temperature 170 ° C, heating rate 3
° C / min, preheating time 300sec, cylinder pressure 10Kgf /
The relationship between temperature and viscosity is measured under the conditions of cm ² and a die (L1.0 mm, D1.0 mm), and the temperature at which the viscosity becomes 1 × 10 ⁴ Pa · s is determined.

Next, the operation of the image forming apparatus will be described. When the image forming operation is started, in the black image forming unit 10B, the surface of the photoconductor drum 1 is uniformly charged by the charging device 2, and then image light is irradiated from the exposure device 3, and A latent image is formed on the surface. Then, the latent image on the photosensitive drum 1 passes through a position facing the developing device 4 containing the black toner, and the charged toner is selectively transferred to the photosensitive drum 1 in the developing electric field, and the latent image is Be visualized. At this time, the image light irradiates the image portion, and the toner having the same polarity as the surface potential of the photosensitive drum 1 charged by the charging device 2 is transferred to the exposed portion of the photosensitive drum 1. Thus, a toner image is formed. This toner image is brought into contact with the peripheral surface of the intermediate transfer member 5 by the circumferential movement of the photosensitive drum 1, and the toner image is electrostatically attracted onto the intermediate transfer member 5 by the action of the corona discharger 6, and the primary transfer is performed. .

Similarly, the yellow image forming unit 10Y
, The photosensitive drum 1 is charged by the charging device 2, and image light is emitted from the exposure device 3 to form a latent image corresponding to a yellow image on the photosensitive drum 1. This latent image is developed by the developing device 4 containing yellow toner to form a yellow toner image. This toner image is
The image is transferred onto the intermediate transfer member 5 in contact with the photosensitive drum 1 so as to overlap the previously formed black toner image.

Thereafter, similarly, in the magenta image forming unit 10M, charging by the charging device 2, irradiation of image light from the exposure device 3, and formation of a toner image by the magenta developing device 4 are performed. The image is transferred onto the body 5 so as to overlap the previous toner image. Further, in the cyan image forming unit 10 </ b> C, recharging by the charging device 2, irradiation of image light from the exposure device 3, and formation of a toner image by the cyan developing device 4 are performed, and this toner image is superimposed on the intermediate transfer member 5. Is transcribed.

When the primary transfer of the toner image of the fourth color is performed, the toner image superimposed and transferred on the surface of the intermediate transfer member 5 is moved by the heating plate 9 with the intermediate transfer member 5 rotating around. Is heated from the back side. Heating plate 9 is 1
The toner image is heated to 50 to 200 degrees, and the heat melts the toner image on the intermediate transfer member 5. Next, the toner image on the intermediate transfer member 5 is transported to a secondary transfer position facing the transport path of the recording medium P. At the secondary transfer position, the temperature of the heat transfer roll 11 is set at 100 ° C. to 150 ° C., and the toner image on the intermediate transfer body 5 is pressed against the normal temperature recording medium P sent at a predetermined timing. . As a result, the temperature of the toner decreases, the cohesive force of the toner increases, and the toner integrally transfers from the intermediate transfer member 5 to the recording medium P having a large adhesive force with the toner, and penetrates into the fibers of the recording medium. I do. In this way, the multicolor toner image on the intermediate transfer body 5 is transferred onto the recording medium and is fixed at the same time.

On the other hand, the intermediate transfer body 5 after the completion of the secondary transfer is conveyed to a position facing the cleaning belt 14, and the residual toner on the surface comes into contact with the cleaning belt 14. At this time, the residual toner on the intermediate transfer member comes into contact with the cleaning belt 14 which has been heated to a temperature equal to or higher than the softening point of the toner by heat conduction from the heat fixing roll 11,
Strongly adheres to the cleaning belt. Then, the intermediate transfer member 5 and the cleaning belt 14 move while contacting with the residual toner therebetween. At the downstream end of the contact area, the surface temperature of the intermediate transfer member 5 and the cleaning belt 14 is cooled to the softening point temperature of the toner or lower, so that the residual toner is solidified, the cohesive force between adjacent toners is increased, and the residual toner is increased. The toner is removed from the intermediate transfer body 5 by the adhesive force of the cleaning belt 14. At this time, a low-density residual image having a low toner coverage on the intermediate transfer member, such as a fog or a halftone image, is easily removed.
Further, even if the adhesion to the toner increases due to contamination or deterioration of the surface of the intermediate transfer member, the cohesion between the toners is large,
The toner is stably removed without being separated between the toner layers. The intermediate transfer member 5 from which the residual toner has been removed is conveyed to a position facing the photosensitive drum 1 by orbital movement, and is subjected to the primary transfer of the next toner image.

In such an image forming apparatus, the residual toner on the intermediate transfer member 5 is transferred to the cleaning belt 14 and removed, so that the surface of the intermediate transfer member 5 can be kept in good condition for a long time, and high quality can be maintained. Image can be obtained.

FIG. 2 is a block diagram showing a configuration of the first, second, third, and fourth embodiments.
FIG. 7 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the invention described in claim 4, claim 5, claim 6, or claim 7. In this image forming apparatus, in order to achieve 100% transfer at the time of secondary transfer, a cleaning device having a measure for improving transfer efficiency is arranged at the secondary transfer portion. Since the configuration before the secondary transfer is almost the same as that of the image forming apparatus shown in FIG. 1, the configuration near the secondary transfer section will be described here.

In this image forming apparatus, the intermediate transfer body 35
It is rotatably supported by the support rolls 51, 52, 53, and 54 and the heating transfer roll 41. In the secondary transfer portion, the recording medium holding belt 48 stretched between the pressure roll 38 and the tension roller 49 is intermediate. It is arranged so as to be in contact with the transfer body 35. A cooling device 45 is provided on the back side of the intermediate transfer body 35 in the contact area. In the present embodiment, the cooling device is provided on the back side of the intermediate transfer body 35, but may be provided on the back side of the recording medium holding belt. Although a fan is generally used as the cooling device 45, in the present embodiment, a heat transporter that transfers heat recovered by cooling to the intermediate transfer member 35 upstream of the secondary transfer position. You are using

FIG. 3 is a schematic configuration diagram of a cooling device 45 including such a heat transport body. (A) is a top view, (b)
Shows a front view, and (c) shows a side view. This cooling device 45
Is composed of a heat transporter having a heating-side contact member 61, a cooling-side contact member 62, and an annular heat pipe 63 penetrating both contact members, and four sets of these are arranged in the moving direction. . Pure water is used for each heat pipe 63 as a refrigerant. The heat pipe is in contact with two portions of the intermediate transfer member having a temperature difference, that is, a portion facing the secondary transfer position and a portion downstream of the primary transfer position. Then, the pure water in the heat pipe is vaporized in the high temperature portion (secondary transfer position) and travels upward, and is cooled and liquefied in the low temperature portion (downstream of the primary transfer position). By repeating this, it has a function of transferring thermal energy from a high-temperature object to a low-temperature object. In such a heat transporter, heat taken by cooling is reused, so that power can be saved.

In the image forming apparatus, the cooling device 4
5, the surface temperature of the intermediate transfer body and the recording medium holding belt at the downstream end of the contact area between the intermediate transfer body 35 and the recording medium holding belt 48 is lower than the softening point temperature of the toner, for example, about 1
It is set so that it is cooled below 00 ° C. As a result, the toner image can be uniformly transferred from the intermediate transfer body 35 to the recording medium P without being separated.

What needs to be cleaned are the fogging toner in the non-sheet passing portion that is not transferred to the recording medium and the untransferred toner generated due to a paper jam or the like. The paper passing portion on the intermediate transfer body where the toner image is transferred from the intermediate transfer body 35 to the recording medium P at the secondary transfer position does not require cleaning because the transfer efficiency is 100%. The untransferred toner may be cleaned at least before returning to the image forming process. Therefore, by using the recording medium holding belt 48 also as a cleaning belt for the intermediate transfer member 35, a cleaning function of the intermediate transfer member 2 can be achieved.

At the secondary transfer position, the intermediate transfer member 35 and the recording medium holding belt 48 are in close contact with each other with the residual toner on the intermediate transfer member 35 melted by the heat transfer roll 41 or the like sandwiched therebetween. At this time, the residual toner on the intermediate transfer body 35, which has been melted by heat, comes into contact with the recording medium holding belt 48 heated to a temperature equal to or higher than the softening point of the toner due to heat conduction from the heat transfer roll 41 or the like. Strongly adheres to the holding belt 48. Then, the intermediate transfer member 35 and the recording medium holding belt 48 move with the residual toner therebetween. At the downstream end of the contact area, the surface temperature of the intermediate transfer body 35 and the recording medium holding belt 48 is cooled so as to be lower than the softening point temperature of the toner, for example, 100 degrees or lower. The cohesive force between the adjacent toners is increased, and the residual toner is removed from the intermediate transfer member 35 by the adhesive force of the recording medium holding belt 48. Therefore, a low-density residual image having a low toner coverage on the intermediate transfer member, such as a fog or a halftone image, can be easily removed. Further, even if the adhesion to the toner increases due to contamination or deterioration of the surface of the intermediate transfer member, the toner can be stably removed without being separated between the toner layers due to a large cohesive force between the toners.

Although the image forming apparatus shown in the above-described embodiment has been described as having a plurality of photosensitive drums,
The present invention can be similarly applied to an image forming apparatus which has one photosensitive drum and a plurality of developing devices, transfers one color to an intermediate transfer body every one cycle, and forms a color image in a plurality of cycles.

[0048]

As described above, according to the image forming apparatus of the present invention, the contact area between the intermediate transfer body and the cleaning member is formed, and the temperature of the intermediate transfer body and the cleaning member at the downstream end of the contact area is formed. Is cooled below the softening point temperature of the toner, so that the residual toner on the intermediate transfer member solidifies,
The cohesive force between the adjacent toners is increased, and the residual toner can be transferred to the cleaning member and removed from the intermediate transfer member. For this reason, a low-density residual image having a low toner coverage on the intermediate transfer member, such as a fog or a halftone image, can be easily removed. Further, even if the adhesion between the intermediate transfer member and the toner increases due to contamination or deterioration of the surface of the intermediate transfer member, the toner is stably removed without being separated between the toner layers because the toner has a large cohesive force. Can be. This makes it possible to stably remove the deposits on the intermediate transfer member for a long period of time, thereby achieving an image forming apparatus capable of obtaining a high-quality image without image quality deterioration. In addition, by using the recording medium holding means also as a cleaning member at the time of the secondary transfer, a dedicated cleaning means is not required, and the cost can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a schematic configuration diagram illustrating an image forming apparatus according to a second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram illustrating a cooling device used in the image forming apparatus illustrated in FIG. 2;

FIG. 4 is a schematic configuration diagram illustrating a conventional image forming apparatus.

FIG. 5 is a graph showing a relationship between toner coverage and cleaning efficiency in a conventional image forming apparatus.

FIG. 6 is a graph showing the relationship between the number of prints and the cleaning efficiency in a conventional image forming apparatus.

[Explanation of symbols]

 1, 31 Photoconductor drum 2, 32 Charging device 3, 33 Exposure device 4, 34 Developing device 5, 35 Intermediate transfer member 6, 36 Corona discharger 7, 37 Transfer baffle 8 Pressure roll 9, 39 Heating plate 11, 41 Thermal transfer roll 12, 42 Feed roller 13, 43 Tray 14 Cleaning belt 15 Cooling fan 16, 46 Metal blade 20, 50 Conveying belt 21, 22, 23, 24 Support roll 38 Pressure roll 45 Cooling device 48 Recording medium holding belt 49 Tension roller 51, 52, 53, 54 Support roll

Claims (8)

[Claims] An image carrier having an endless peripheral surface on which a toner image is formed by attaching toner to the peripheral surface, and an endless peripheral surface facing the image carrier, and An intermediate transfer member supported so as to be able to move around the surface, a transfer device for transferring a toner image on the image carrier to the intermediate transfer member, and a toner image transferred on the intermediate transfer member. In an image forming apparatus having a heat transfer unit for performing a secondary transfer from the intermediate transfer body to a recording medium by heating and pressing, the endless peripheral surface forms a contact area with the peripheral surface of the intermediate transfer body. A cleaning member that is disposed so as to move in the same direction as above, and that transfers residual toner on the intermediate transfer body and removes it from the intermediate transfer body, downstream of a contact area between the intermediate transfer body and the cleaning member. The intermediate transfer member at the edge and the Image forming apparatus, wherein a surface temperature of the cleaning member is set to be less than the softening point temperature of the toner. 2. The image forming apparatus according to claim 1, further comprising a cooling unit that cools at least one of the intermediate transfer body and the cleaning member in an area where the intermediate transfer body contacts the cleaning member. 3. The cooling device according to claim 2, wherein the cooling unit is a heat transporter that moves heat in a region where the intermediate transfer member contacts the cleaning member to an upstream side of the region. Image forming apparatus. 4. The cleaning member is an endless belt that is stretched around at least two rolls and moves around. The cleaning member contacts a peripheral surface of the endless belt and removes toner adhering to the peripheral surface. The image forming apparatus according to claim 1, further comprising a toner removing member that removes the toner. 5. The cleaning member holds the recording medium between the intermediate transfer member and the recording medium and presses the recording medium against the intermediate transfer member, and forms a toner image on the recording medium from the intermediate transfer member. The image forming apparatus according to claim 1, wherein the secondary transfer uses a pressing force of the cleaning member. 6. The intermediate transfer member such that a temperature of the surface of the intermediate transfer member at an upstream end of a contact region between the intermediate transfer member and the cleaning member is equal to or higher than a softening point temperature of the toner. The image forming apparatus according to claim 1, further comprising a heating device configured to heat the image forming apparatus. 7. The image forming apparatus according to claim 1, wherein the cleaning member has a surface layer having a lower releasability than a peripheral surface of the intermediate transfer body. 8. The image forming apparatus according to claim 7, wherein the surface layer is formed of a heat-meltable adhesive layer.