JPH1020685A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an image quality deterioration caused by the void of the image by reducing the pressing force applied by a transfer body onto the image carrier, in the image forming device provided with the transfer body made circulate-traveling while held in contact with the image carrier, for statically transferring the toner image formed on the image carrier to the transfer body or to a recording material held on the transfer body. SOLUTION: In this image forming device, an intermediate transfer body 16 of an endless belt type is extend and supported by plural supporting bodies such as a drive roller 18, a tension roller 19 or the like, and arranged so as to get in touch with the image carrier 11 between the rollers 18 and 19. In connection with the intermediate transfer body 16, the stretching rigidity that is the product of Young's modulus and cross sectional area is set below 3×10<5> N and the stretching force is set below 80N. Moreover, a space between the rollers 18 and 19 is set at approximately 100mm. In such a manner, contact pressure between the intermediate transfer body 16 and the image carrier 11 per 1cm in the direction at right angle to the advancing direction of the process becomes below 0.06 N, therefore the toner image is prevented from the application of excessive fore.

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 a copying machine and a printer using an electrophotographic method, and more particularly to a transfer member which rotates in contact with an image bearing member. The present invention relates to an image forming apparatus that electrostatically transfers a formed toner image to a transfer member or a recording material held on the transfer member.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus using an electrophotographic method, a toner image is formed on the surface of an image carrier such as a photosensitive drum, and the toner image is electrostatically transferred onto a recording material such as PPC paper by a transfer device. Transcription. Then, the recording material on which the toner image has been transferred is guided to a fixing device, and the toner image is fixed on the recording material to form a permanent image. Further, there is also widely used an apparatus in which a toner image formed on the surface of an image carrier is once transferred onto an endless transfer member, and then the toner image is transferred and fixed on a recording material to form a recorded image.

However, in such an image forming apparatus, when a toner image is transferred to a recording material or a transfer member, an image quality defect such as a hollow image may occur. This is a phenomenon in which the central portion of a line image or the like is dropped without being transferred, and it has been clarified in previous studies that the central portion of the image is likely to occur when a toner image is transferred under high pressure. . Accordingly, by applying a constant pressing force at the transfer section, the occurrence of hollow holes is particularly remarkable in an apparatus using a transfer roller which secures a contact width (hereinafter referred to as a nip width) between a recording material and an image carrier. Become.

As means for adjusting the pressing force of the transfer roller, Japanese Patent Application Laid-Open Nos.
63097, JP-A-5-204263, JP-A-7-20732, JP-A-7-160129, JP-A-7-261568, and JP-A-7-31
Many proposals have been made in, for example, Japanese Patent Publication No. 9302. These are intended to reduce the elastic force of the transfer roller acting when a constant contact width is secured and to reduce the load acting on the image carrier, mainly by setting the hardness of the transfer roller or drum to a certain value or less. Is what you do.

Further, as related to components other than the transfer roller, as shown in Japanese Patent Application Laid-Open No. Hei 4-13170, a pressure contact member provided for sufficiently pressing a recording material and an image carrier during transfer. A device for adjusting the pressure has been devised. As a similar technique, Japanese Patent Application Laid-Open No. 5-3467 is disclosed.
No. 42 discloses a technique in which a roller provided in a transfer unit is used to adjust a pressure acting on an image carrier in order to reduce a stress acting on a belt-shaped transfer body.

On the other hand, even if the pressing force of the transfer roller is controlled as described above, the pressing force may fluctuate due to a mechanical error of the transfer roller itself. In order to prevent this, Japanese Patent Application Laid-Open No. Hei 6-110346 discloses a proposal for improving the straightness, ellipticity, and runout of a transfer roller.

Japanese Patent Laid-Open Publication No. 6-8321 discloses a countermeasure for a case where a constant pressing force is indispensable and the occurrence of hollow holes cannot be suppressed.
No. 2, JP-A-7-31902, a technique for providing a speed difference between a recording material or a transfer roller and an image carrier has been proposed. These are intended to prevent the occurrence of voids by dispersing the pressure in the toner layer by the frictional force or facilitating the movement of the toner. As an obstacle at this time, elongation of an image, abrasion of an image carrier, and the like may occur. To solve this problem, the material hardness of the transfer roller surface is reduced as disclosed in Japanese Patent Application Laid-Open No. 7-20732. Techniques have been proposed to solve these problems by specifying and setting the pressing force within a certain value. Also, in the above-mentioned Japanese Patent Application Laid-Open No. 7-319302,
Proposals have been made to limit the friction coefficient of the contact portion for the same purpose.

In addition, Japanese Patent Application Laid-Open No. 7-44030 discloses a device for imparting vibration to either the image carrier or the recording material to improve the mobility of the toner and to prevent the occurrence of voids. I have. Japanese Patent Application Laid-Open No. Hei 7-104591 discloses a technique in which a surface of an image carrier is provided with elastic deformation so as to substantially obtain a speed difference from a recording material.

On the other hand, in a color image forming apparatus, it is necessary to stably convey a recording material such as a transfer sheet and perform a plurality of transfers, and the recording material is electrostatically or mechanically transferred onto a recording material holding member. There is widely used a recording material transporting method in which a plurality of toner images are transferred onto an intermediate transfer member and then collectively transferred to a recording material. In these systems, it is common to use a circulating belt because of the high degree of freedom of the device configuration.

According to an investigation by the inventors of the present invention, when a belt is used, a large pressing force acts according to the amount of contact with the image carrier due to the tension and rigidity of the belt. I know it will be. Less than,
The cause of the generation of the pressing force will be outlined with reference to FIG. This figure is an enlarged view showing an outline of a contact portion between the belt 206 used as an intermediate transfer member and the image carrier 201. The belt 206 is stretched around the support rollers 207 and 208 so as to be able to rotate, and is provided with a constant initial tension T0 to ensure a predetermined running property. When the image bearing member 201 comes into contact with the belt 206 and the belt 206 is bent, a component F of tension acts on the image bearing member 201 as a load. At this time, the image carrier 201 and the support roller 20
7, 208 have a mechanical error such as eccentricity, so that it is practically impossible to stabilize the load F to a small value.

As a result of a detailed investigation of this phenomenon, it has been found that since the load generating mechanism is different from that of the transfer roller, the means for adjusting the pressing force as described above cannot be applied or even if it is applied, a sufficient improvement effect can be obtained. I found that I could not do it. That is, JP-A-2-10388, JP-A-4-13170, JP-A-4-16397, JP-A-5-204263, JP-A-7-20
732, JP-A-7-160129, JP-A-7-261568, JP-A-7-319302, JP-A-6-110346 and the like disclose a transfer roller, a drum or a pressing member. However, when applied to a belt, it has some effect, but it cannot be applied to a belt, and a direct effect cannot be obtained for the cause of hollowing out in the apparatus as shown in FIG.

Also, the above-mentioned JP-A-6-83212, JP-A-7-103591, and JP-A-7-310 are disclosed.
The technique disclosed in Japanese Patent Application Publication No. 302-302 and the like requires a method of correcting a change in image magnification, an image shift, and the like due to a speed difference, and has a problem that the apparatus becomes complicated and expensive. Further, the technique disclosed in Japanese Patent Application Laid-Open No. 7-44030 not only has a complicated and expensive vibration imparting mechanism, but also makes it very difficult to suppress image deterioration due to vibration.

Although the technique disclosed in Japanese Patent Application Laid-Open No. 5-346742 has a different purpose, it seems that some effect can be expected for the problem shown in FIG. 15, but according to the investigation by the present inventors, However, in a configuration using a belt, the load is excessive, and it is not possible to eliminate the occurrence of the hollow.

On the other hand, Japanese Patent Application Laid-Open No. 62-186286,
JP-A-63-1655, JP-A-6-228335
In Japanese Patent Application Laid-Open Publication No. H10-163, a device is disclosed that pays attention to the fact that the load from the belt depends on the elastic characteristics of the belt, and mainly aims at reducing the image position shift due to the expansion and contraction of the material.
However, such a technique is effective only under limited conditions for preventing hollowing out.

[0015]

As described above,
Although various means for adjusting the pressing force acting on the image carrier have been proposed, no satisfactory effect has been obtained with respect to the occurrence of voids. In particular, in an apparatus using a belt as shown in FIG. 15, a large pressing force acts according to the amount of contact with the image carrier due to the tension and rigidity of the belt,
Although the occurrence of voids is remarkable, no effective solution is shown. This is probably because the image carrier and the support roller have mechanical errors such as eccentricity, and it is difficult to stabilize the pressing force acting between the belt and the image carrier at a small value.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has as its object to reduce the pressing force acting on the image carrier when using a drum or belt-like transfer member that moves around. It is an object of the present invention to propose an image forming apparatus capable of reducing the image quality and preventing the image quality from deteriorating due to the dropout without complicating the apparatus configuration.

[0017]

According to a first aspect of the present invention, there is provided an image bearing member having a peripheral surface on which an electrostatic latent image is formed, and an image bearing member on the image bearing member. In the latent image,
A developing device for selectively transferring toner to form a toner image; a transfer member having a peripheral surface formed in an endless shape, the peripheral surface moving in contact with the image carrier, and moving around the image carrier; And a transfer device for electrostatically transferring the toner image on the transfer member or a recording material held on the transfer member, wherein the contact pressure between the image carrier and the transfer member is , Is set to be 0.06 N or less per 1 cm in the direction perpendicular to the process direction. In such an image forming apparatus, since the contact pressure between the image carrier and the transfer body is appropriately adjusted, excessive pressure does not act on the toner image on the image carrier at the time of transfer. No good images can be obtained.

Further, by setting the contact pressure between the image carrier and the transfer member as described above, for example, as in the image forming apparatus according to the second aspect, the transfer member is stretched on a plurality of supports. Even in the case of an apparatus in which a transfer belt is used and the transfer belt is arranged so as to be in contact with the image carrier between the supports, it is possible to eliminate the occurrence of the hollow.

In order to realize such a contact pressure between the image bearing member and the transfer belt, in the image forming apparatus according to the present invention, the pulling force is the product of the Young's modulus of the transfer belt and the cross-sectional area. It is assumed that the rigidity is 3 × 10 ⁵ N or less and that the support is stretched between the supports with a tension of 80 N or less. Thereby, even when there is a mechanical error such as eccentricity in the image carrier or the support, the pressing force acting on the image carrier from the transfer belt when the transfer belt contacts the image carrier between the supports, Exceeding 0.06 N per 1 cm in the direction perpendicular to the process direction can be avoided. For this reason, an excessive pressure does not act on the toner image on the image carrier at the time of transfer, and an image without a hollow portion can be obtained. In addition, there is little influence on belt conveyance performance, image position shift, and the like, and it is possible to avoid occurrence of image quality deterioration.

In the image forming apparatus according to the fourth aspect of the present invention, when the transfer belt contacts the image carrier between the supports, the stretch interval of the portion of the transfer belt that contacts the image carrier is 100 mm. That is all. Thereby, even when the roller or the image carrier that supports the transfer belt is eccentric, the contact pressure between the transfer belt and the image carrier is reduced to 0.06 N or less per 1 cm in the direction perpendicular to the process direction. Can be easily set. For this reason,
An excessive pressure does not act on the toner image on the image carrier at the time of transfer, and an image without a hollow portion can be obtained. Further, since the material and the like of the transfer belt are not restricted, the material of the belt can be selected so as to further improve the belt conveyance performance and the image position shift.

Further, in the image forming apparatus according to the present invention, an image carrier on which an electrostatic latent image is formed on a peripheral surface, and toner is selected for the electrostatic latent image on the image carrier. A developing device that forms a toner image by transferring the toner image, and a belt member that is stretched around a plurality of supporting rollers and moves endlessly in a circumferential direction, between positions supported by the supporting rollers,
A transfer belt whose peripheral surface is in contact with the image carrier, and a transfer device that electrostatically transfers the toner image on the image carrier onto the transfer body or a recording material held on the transfer body. The image forming apparatus includes a position regulating member that is in contact with an outer peripheral surface of the transfer belt near a contact position between the transfer belt and the image carrier, and restricts a position of the transfer belt.

In such an image forming apparatus, the contact pressure between the transfer belt and the image carrier can be easily adjusted by the position regulating member irrespective of conditions such as the rigidity of the transfer belt and the eccentricity of the image carrier and the supporting roller. It becomes possible to do. That is, the contact pressure between the image carrier and the transfer belt can be reduced by 1 cm in the direction perpendicular to the process progress direction by appropriately setting the installation position of the position regulating member and the pressing force acting on the transfer belt.
It is possible to easily control the pressure to be 0.06 N or less. For this reason, an excessive pressure does not act on the toner image on the image carrier at the time of transfer, and an image without a hollow portion can be obtained. Further, there is no restriction on the transfer belt or the support roller for transporting the transfer belt, and the degree of freedom in setting is extremely high.

According to a sixth aspect of the present invention, in the image forming apparatus, an image carrier having an electrostatic latent image formed on a peripheral surface thereof, and toner is selectively applied to the electrostatic latent image on the image carrier. A developing device that transfers to form a toner image, and a belt member that is stretched around a plurality of support rollers and moves endlessly in a circumferential direction,
A transfer belt having a peripheral surface in contact with the image carrier between positions supported by the support roller; and a recording material holding the toner image on the image carrier on the transfer body or on the transfer body. An image forming apparatus having a transfer device that electrostatically transfers the image onto the transfer belt, a sensor for detecting a contact pressure between the transfer belt and the image carrier, and a contact pressure between the transfer belt and the image carrier. It is provided with a contact pressure adjusting means for adjusting, and a control means for controlling an adjustment amount of the contact pressure adjusting means based on an output of the sensor.

In such an image forming apparatus, the contact pressure between the transfer belt and the image carrier is detected by a sensor, and the contact pressure between the transfer belt and the image carrier is adjusted by control means based on the output of the sensor. Since the adjustment amount of the contact pressure adjusting means is controlled, the contact pressure can be controlled to a preferable contact pressure by the contact pressure adjusting means. As the sensor, for example, a sensor that detects the position of the belt near the contact portion between the transfer belt and the image carrier and converts the detected position into the contact pressure between the transfer belt and the image carrier can be used. Further, the pressing force acting from the transfer belt may be directly measured by a sensor, and the adjustment amount of the contact pressure adjusting means may be controlled based on the measured pressure. As a result, the contact pressure between the transfer belt and the image carrier can be accurately controlled, and the contact pressure can be set to the above-described preferable value regardless of conditions such as belt rigidity and roller eccentricity. it can. For this reason, an excessive pressure does not act on the toner image on the image carrier at the time of transfer, and an image without a hollow portion can be obtained.

As the contact pressure adjusting means, for example, a means for changing the center position of a support roller which stretches an image carrier or a transfer belt is used. That is, by controlling the adjustment amount of the center position of the support roller based on the output of the sensor, the contact pressure between the transfer belt and the image carrier can be controlled to a preferable value. For this reason, there are few restrictions on the transfer belt and the support roller, and the degree of freedom in design is very high. Further, since the center position of the support roller is changed so that the tension of the transfer belt is kept substantially constant, the deterioration of the image quality such as the displacement of the image position due to the expansion and contraction of the transfer belt does not occur.

Further, as another example of the contact pressure adjusting means, a means for adjusting the tension of the transfer belt can be used as in the invention of the eighth aspect. That is, by adjusting the tension of the transfer belt based on the output of the sensor, the contact pressure between the transfer belt and the image carrier can be controlled to a preferable value. For this reason, there are few restrictions on the transfer belt and the support roller, the degree of freedom in design is extremely high, and the tension of the transfer belt can be controlled without moving the position of the support roller. Can be

In the image forming apparatus according to the ninth aspect of the present invention, the control means determines the adjustment amount according to information of an image formed on the image carrier. This makes it possible to discriminate an image in which a hollow image is likely to occur and control the adjustment amount of the contact pressure adjusting means, so that the transfer belt and the image carrier are not affected by conditions such as belt rigidity and roller eccentricity. The contact pressure with the contact can be adjusted. Further, the load acting on the toner layer for forming an image can be kept constant according to the image characteristics such as the area of the image portion and the height of the toner layer, so that the deterioration of the image quality can be prevented.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] FIG. 1 is a schematic configuration diagram showing a color copying machine according to an embodiment of the present invention as set forth in claim 1, claim 2, claim 3, or claim 4. The color copying machine includes an image reading unit 2 that reads an image of a document 4 above an image forming unit 1. This image reading unit 2
A platen glass 3 on which an original 4 is placed, a light source 5 for exposing and scanning the original 4, and a reflected light image from the original 4 to a predetermined position via first and second scanning mirrors 6 and 7. An image forming lens 8 for forming an image and a color CCD sensor 9 for reading an image of the document 4 as RGB image signals are provided.
Further, the image processing apparatus 10 includes an image processing device 10 that converts RGB image signals read by the color CCD sensor 9 into yellow, magenta, cyan, and black image signals. It is temporarily stored in a memory provided inside.

Further, inside the image forming section 1, an image forming unit 30 and an intermediate transfer belt unit 31 installed facing the image forming unit 30 are arranged. The image forming unit 30 includes a drum-shaped image carrier 11 having a photoreceptor layer formed on its surface, and a charging device that uniformly charges the surface of the image carrier 11 around the image carrier 11. 1
2, a laser beam scanning device 13 for irradiating a laser beam based on a signal from the image processing device 10 to form a latent image on the surface of the image carrier, and a latent image on the image carrier that contains toners of different colors. Four developing devices 14a, 14b, 1 for selectively transferring toner to an image to form a toner image
4c and 14d, and a cleaning device 15 for removing toner remaining on the image carrier 11 after the transfer of the toner image.

The transfer belt unit 31 is disposed downstream of the developing device 14 in the rotation direction of the image carrier 11, and is an endless belt that is in contact with the image carrier 11 and whose peripheral surface is supported so as to be able to rotate. The intermediate transfer body 16 includes a transfer charger 17 that transfers a toner image on the image carrier 11 to the intermediate transfer body 16. The intermediate transfer body 17 is stretched by a drive roller 18, a tension roller 19, idler rollers 20, 21 and a secondary transfer backup roller 22, and is driven by the rotation of the drive roller 18 in the direction of arrow A shown in the drawing. It is designed to move around.

Around the intermediate transfer member 16, a secondary transfer roller 23 located at a position facing the backup roller 22 to transfer the toner image on the intermediate transfer member onto a sheet 25, and a sheet tray 24. A feed roller 26 that feeds the paper 25 stored in the inside to the pressure contact position between the secondary transfer roller 23 and the intermediate transfer body 16, and a cleaner 27 that cleans the peripheral surface of the intermediate transfer body 16 after the transfer of the toner image. ing. Further, a paper transport unit 28 that transports the paper 25 onto which the toner image has been transferred, and a fixing device 29 that fixes the toner image on the paper are provided.

The intermediate transfer member 16 is a belt made of a polyimide resin or a polycarbonate resin having a volume resistivity of 10 ¹² Ω · cm set to a width of 350 mm, a thickness of 0.075 mm, and a Young's modulus of 6000 N / mm ^2. It is arranged between the roller 18 and the tension roller 19 so as to be in contact with the image carrier 11. The distance between the drive roller 18 and the tension roller 19 is set to 100 mm, and the tension of the intermediate transfer member is set to 50N.

The transfer charger 17 applies a charge having a polarity opposite to the charge polarity (negative polarity) of the toner from the back side of the intermediate transfer body 16 to a position facing the image carrier 11. The toner image on the carrier 11 is electrostatically attracted to the intermediate transfer body 16.

The secondary transfer roller 23 is used for the intermediate transfer member 1
At the position facing the sheet 6, a charge having a polarity opposite to that of the toner is applied to the sheet 25, so that the toner image on the intermediate transfer member is transferred onto the sheet.

Next, the operation of the above color copying machine will be described. In the image reading device 2, a document 4 placed on a platen glass 3 is irradiated by a light source 5,
Is reflected by a color CCD sensor 9 via first and second scanning mirrors 6 and 7 and an imaging lens 8, and the image of the original 4 is read as an RGB image signal by the color CCD sensor 9. . The RGB image signals read by the color CCD sensor 9 are converted into yellow, magenta, cyan, and black image signals by the image signal processing device 10 and temporarily stored in the memory of the image processing device 10 as necessary. You.

In the image forming section 1, the surface of the image carrier 11 is uniformly charged by the charging device 12, and then the laser beam scanning device 1 is operated based on a signal from the image processing device 10.
3 irradiates a laser beam to form a latent image on the surface of the image carrier 11. Thereafter, the latent image on the image carrier 11 passes through a position facing the developing device 14a containing the yellow toner, and the charged toner is selectively transferred to the image carrier 11 in the developing electric field, and the latent image is transferred. 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 image carrier 11 charged by the charging device 12 is transferred to the exposed portion of the image carrier 11. Thus, a toner image is formed.

This toner image is brought into contact with the peripheral surface of the intermediate transfer member 16 by the orbital movement of the image carrier 11, and is transferred to the transfer charger 17.
The toner image is electrostatically attracted onto the intermediate transfer body 16 by the action of the above, and the primary transfer of the toner image is performed. The toner remaining on the image carrier 11 after the primary transfer is removed by the cleaning device 15, and is conveyed again to a position facing the charging device 12.

On the other hand, even after the yellow toner image is transferred, the intermediate transfer body 16 is driven to rotate, and the transferred image is again conveyed to a position facing the image carrier 11. During such primary transfer, the secondary transfer roller 23 and the cleaner 27 are retracted backward so as not to contact the intermediate transfer body 16.

During the rotation of the intermediate transfer member 16, the image carrier 11 is recharged by the charging device 12 and irradiated with a laser beam from the laser beam scanning device 13 to form a magenta image on the image carrier 11. A corresponding latent image is formed. This latent image is developed by the developing device 14b containing magenta toner, and a magenta toner image is formed. This toner image is transferred on the intermediate transfer body 16 that is driven to rotate so as to overlap the previously formed yellow toner image.

Thereafter, similarly, as the third cycle, the recharging by the charging device 12 and the laser beam scanning device 13
And the toner image is formed by the cyan developing device 14c, and this toner image is transferred by being superimposed on the previous toner image by driving the intermediate transfer body 16 to rotate. Further, as a fourth cycle, recharging by the charging device 12,
Irradiation of image light from the laser beam scanning device 13 and formation of a toner image by the black developing device 14d are performed, and this toner image is transferred onto the intermediate transfer body 16 in an overlapping manner.

When the primary transfer of the fourth color is performed, the secondary transfer roller 23 and the cleaner 27 advance to a position where the secondary transfer roller 23 and the cleaner 27 come into contact with each other, and the toner image superimposed on the intermediate transfer member 16 is subjected to the secondary transfer. The sheet is conveyed to a position facing the roller 23. Then, the paper 25 is fed between the intermediate transfer body 16 and the secondary transfer roller 23 in accordance with the transport timing. The toner image on the intermediate transfer body 16 comes into contact with the paper 25, and a charge having a polarity opposite to that of the toner is applied from the back surface by the secondary transfer roller 23, and the toner image is transferred onto the paper. The paper 25 to which the toner image has been secondarily transferred is transported through the paper transport unit 28, and the toner image is melted and fixed on the paper 25 by the fixing device 29. Further, the intermediate transfer body 16 on which the secondary transfer of the toner image has been completed has the residual toner removed by the cleaner 27, and is conveyed again to a position facing the image carrier 11 to prepare for the next image forming step.

[Experiment on the Color Copier of the First Embodiment] According to the investigation by the present inventors, the contact pressure between the intermediate transfer body 16 and the image carrier 11 in the above-described image forming apparatus is equal to the contact pressure of the belt member. It is known that it depends on the rigidity and tension, the amount of deflection d shown in FIG. 2, and the span of the intermediate transfer member forming the contact surface (the distance between the driving roller 18 and the tension roller 19). At this time, the amount other than the amount of deflection d is substantially determined at the time of design, but the amount of deflection d fluctuates due to a mechanical error such as an error at the time of installation of the image carrier 11 and the rollers 18 and 19 and an eccentric amount. In consideration of the fact that the contact pressure between the image carrier and the intermediate transfer member fluctuates due to the change in the amount of deflection d, image dropout occurs, an experiment was conducted on the contact pressure and the degree of image dropout. The results will be described below.

(Experiment 1: Experiment on Relationship between Contact Pressure of Intermediate Transfer Body and Image Carrier and Missing Image) Intermediate Transfer Body 16
An experiment was carried out in which the contact pressure between the image bearing member 11 and the image bearing member 11 was changed by changing the position of the tension roller 19, and the state of occurrence of image dropout was confirmed. FIG. 3 shows the result. In this experiment, the intermediate transfer body 16 used a belt made of the above-described polyimide resin, collected a single-color print sample under the above-described conditions, and comprehensively evaluated the occurrence degree, frequency, and the like of voids at each contact pressure. Was graded. In the figure, 0 indicates a state in which no hollow is seen, 1 indicates a state in which the hollow is slightly generated (approximately 1 to 2 places per 10 cm), and 2 indicates a state in which some hollows are generated. (Approximately 3-5 per 10cm
(Approximately several places), 3 indicates a state occurring in almost all areas.

As shown in this figure, when the contact pressure between the image carrier 11 and the intermediate transfer member 16 was set to 2 N or less, it was confirmed that the state of the occurrence of the hollow portion could be maintained well. When this is converted into about 1 cm in the direction perpendicular to the process progress direction, the width of the intermediate transfer member is 35 cm, so
It is understood that it is preferable to set the value to 06N or less.

(Experiment 2: Experiment on Relationship between Stiffness and Tension of Intermediate Transfer Body and Contact Pressure) Next, the contact pressure acting on the image carrier 11 was evaluated by changing the stiffness and tension of the intermediate transfer body 16. The results obtained are shown in FIG. Here, as the worst state expected in the image forming apparatus, the deflection d of the intermediate transfer member caused by a mechanical error of the image carrier 11 and each of the rollers 18 and 19 is set to 0.3 mm, and the driving roller 18 and the tension are set. The experiment was performed with the distance to the roller 19 being 50 mm.
As a result, as shown in FIG.
N or less, when the tensile stiffness calculated by the product of the Young's modulus of the intermediate transfer member and the cross-sectional area is set to 3 × 10 ⁵ N or less,
It can be seen that the contact pressure between the intermediate transfer member and the image carrier can be set to 2N or less.

This result is a result under the worst condition assumed in the image forming apparatus, and it is considered that a good contact pressure can be maintained in any state when used in a normal design state. In addition, the rigidity and the tension can be set in any combination within this range, and the values can be set in consideration of belt conveyance performance, deterioration, and the like.

(Experiment 3: Experiment on Relationship between Stretch Interval of Intermediate Transfer Body and Contact Pressure) Next, in the above color copying machine, as shown in FIG. 5, the distance between the drive roller 18 and the tension roller 19 FIG. 5 shows the result of evaluating the contact pressure between the intermediate transfer member 16 and the image carrier 11 by changing the value of. Here, as worst-case conditions normally assumed, the rigidity of the intermediate transfer body is set to 5.25 × 10 ⁵ N, the tension is set to 150 N, and the deflection of the belt caused by a mechanical error of the image carrier 41 and each of the rollers 48 and 49. The experiment was performed with the amount d set to 0.3 mm.

As shown in FIG. 5, when the distance between the driving roller and the tension roller is 100 mm or more, even if the tension and rigidity of the intermediate transfer member are large, the contact pressure between the image carrier and the intermediate transfer member can be easily increased. It turns out that it can be set to 2N or less. Note that this result is a result under the assumed worst conditions, and it is considered that a good contact pressure can be maintained in any state when used in a normal design state. In addition, any numerical value can be set within this range, and the value can be appropriately set in consideration of the configuration of the belt unit.

(Experiment 4: Experiment on Relationship between Amount of Eccentricity of Drive Roller and Contact Pressure) FIG. 6 shows the relationship between the image carrier and the intermediate transfer member by using the above color copier and changing the amount of eccentricity of the drive roller. FIG. 5 is a view showing the result of evaluating the contact pressure of the sample. Here, in order to make the assumed worst conditions, an experiment was conducted with the rigidity of the intermediate transfer member set to 5.25 × 10 ⁵ N, the tension set to 150 N, and the distance between the drive roller and the tension roller set to 50 mm.

As a result, as shown in FIG. 6, by setting the eccentricity of the roller to 0.1 mm or less, the contact pressure between the image carrier and the intermediate transfer member can be reduced to 2N or less. In this experiment, it is understood that there is no problem if the distance is 0.15 mm or less. However, since the drive roller, the tension roller, and the image carrier all have eccentricity, it is preferable to set the distance to 0.1 mm or less. Note that this result is a result under the worst condition assumed, and it is considered that a good contact pressure can be maintained in any state in normal use. In addition, any value can be set within this range, and the value can be set in consideration of the manufacturability and price of the roller.

[Second Embodiment] FIG. 7 is a partial structural view showing an outline of the vicinity of an image carrier and an intermediate transfer member used in an image forming apparatus according to an embodiment of the present invention. . In the image forming apparatus, in addition to the image forming apparatus shown in FIG. Position regulating member 60 for restricting the position of the body
Is provided. The position regulating member 60 is formed of a cylindrical member that does not rotate, and is installed such that the lowermost portion that comes into contact with the intermediate transfer body 56 is located substantially on a horizontal line with the image carrier 51. The other configuration of the image forming apparatus is the same as that of the image forming apparatus shown in FIG.

In such an image forming apparatus, even when an excessive pressure acts on the image carrier 51 from the intermediate transfer member 56 due to the eccentricity of the drive roller 58, the tension roller 59, and the image carrier 51, the position of the image carrier 51 can be reduced. The pressure acting by the regulating member 60 is shared. For this reason, the image carrier 5
The contact pressure between the image carrier 51 and the intermediate transfer member 56 is prevented from becoming excessive, and the contact pressure between the image carrier 51 and the intermediate transfer member 56 can be easily set to an appropriate value of 2N or less.

In this image forming apparatus, when a single-color print sample was collected in the same manner as described above, it was confirmed that a good image free from voids could be obtained. In the image forming apparatus, a cylindrical member is used as the position regulating member 60, but a plate-shaped member may be used instead.

[Third Embodiment] FIG. 8 is a schematic configuration diagram showing an image forming apparatus according to a third embodiment of the present invention. In this figure, the same parts as those of the image forming apparatus shown in FIG.
This image forming apparatus includes, in addition to the image forming apparatus shown in FIG. 1, a sensor 70 for detecting the position of the intermediate transfer member 16 near the contact position between the intermediate transfer member 16 and the image carrier 11, and an intermediate transfer member A contact pressure adjusting means 74 for changing the center position of a tension roller 69 on which the tension member 16 is stretched, an amplifier 71 for amplifying an output from the sensor 70, and an arithmetic unit for calculating an adjustment amount of the contact pressure adjusting means 74 based on the output 72, and a storage device 73 that stores information necessary for calculating the adjustment amount by the arithmetic device 72.

The sensor 70 is a non-contact type optical displacement meter installed at a position facing the outer peripheral surface of the intermediate transfer body 16, and a contact type displacement meter and a load for directly measuring the contact pressure. A converter or the like can be used.

As shown in FIG. 9, the contact pressure adjusting means 74 includes an eccentric cam 75 for changing the center position of the tension roller 69 and a motor 7 for applying a rotational force to the cam 75.
6 and a drive transmission gear 77 for transmitting the driving force of the motor. The tension roller 69 is supported at both ends so that the shaft 69a can move in parallel in the direction of arrow B shown in the drawing, that is, in a direction substantially perpendicular to the contact surface between the image carrier 11 and the intermediate transfer member 16. Support 6
The eccentric cam 75 is in contact with 9b. The other configuration of the image forming apparatus is the same as that of the image forming apparatus shown in FIG.

In such an image forming apparatus, the position of the intermediate transfer body 16 is detected by the sensor 70, and the output from the sensor 70 is sent to the arithmetic unit 72 via the amplifier 71. The arithmetic unit 72 calculates a necessary adjustment amount of the contact pressure adjusting unit 74 based on the information stored in the storage device 73. The driving device 76 is driven based on this adjustment amount, the cam 75 is driven to rotate via the drive transmission member 77, and the center position of the tension roller 69 is adjusted in the direction of arrow B shown in the drawing. That is, the tension roller 69
Of the intermediate transfer member 16 can be changed by changing the center position of the intermediate transfer member 1.
6 and the image bearing member 11 are appropriately adjusted in contact pressure. Accordingly, an excessive pressure does not act on the image carrier 11 at the transfer portion, and a good image without a hollow portion can be obtained.

In the above image forming apparatus, the contact pressure between the intermediate transfer member and the image carrier is adjusted by adjusting the center position of the tension roller 69, but the position of the drive roller 18 is adjusted by the same mechanism. It may be varied. Further, a configuration in which a ball screw and a motor are combined instead of the eccentric cam 75 as described above may be used.

[Fourth Embodiment] FIG. 10 is a schematic configuration diagram showing an image forming apparatus according to a sixth embodiment of the present invention. In this figure, the same parts as those of the image forming apparatus shown in FIG. This image forming apparatus has a sensor 80 for detecting the position of the intermediate transfer body 16 as in the image forming apparatus shown in FIG.
, An amplifier 81, an arithmetic unit 82 for calculating an adjustment amount of the contact pressure adjusting unit 84, and a storage device 83,
The configurations of the tension roller 79 and the contact pressure adjusting means 84 are different. The tension roller 79 is provided with a spring 88 for applying tension by being connected to shafts 79a at both ends, and a pressing plate 88a supporting the spring 88 is provided between the image carrier 11 and the intermediate transfer body 16. Are supported so as to be movable substantially in parallel with the contact surface.

Further, the contact pressure adjusting means 84 is provided as shown in FIG.
As shown in FIG. 5, the eccentric cam 85 is provided so as to be in contact with the pressing plate 88a, a motor 86 for applying a driving force to the cam 85, and a drive transmitting member 87 for transmitting the driving force of the motor. By rotating the eccentric cam 85 by a predetermined amount, the position of the pressing plate 88a can be changed. That is, by changing the position of the pressing plate 88a and changing the amount of compression of the spring 88, the pressing force of the tension roller 79 is adjusted and the tension of the intermediate transfer body 16 is changed. In addition,
Other configurations of this image forming apparatus are the same as those of the image forming apparatus shown in FIG.

In such an image forming apparatus, the position of the intermediate transfer body 16 is detected by the sensor 80, and the output from the sensor 80 is sent to the arithmetic unit 82 via the amplifier 81. The arithmetic unit 82 calculates a necessary adjustment amount of the contact pressure adjusting unit 84 based on the information stored in the recording device 83. The motor 86 is driven based on this adjustment amount,
The cam 85 is driven to rotate to a predetermined position via the drive transmission member 87. By the rotation of the cam 85, the pressing plate 88a
Is changed, the amount of compression of the spring 88 changes, and the pressing force of the tension roller 79 is adjusted. Thereby, the tension of the intermediate transfer member 16 is appropriately adjusted, and the contact pressure between the intermediate transfer member 16 and the image carrier 11 is adjusted to a preferable value. For this reason, the occurrence of image dropout is prevented, and a good image without image quality degradation can be obtained.

[Fifth Embodiment] FIG. 12 is a schematic diagram showing an image forming apparatus according to an embodiment of the present invention. In this figure, the same parts as those of the image forming apparatus shown in FIG. This image forming apparatus includes a sensor 90 for detecting the position of the intermediate transfer body 16, an amplifier 91, and a contact pressure adjusting unit 94.
And an arithmetic unit 92 for calculating an adjustment amount of the contact pressure adjusting means 94 based on an image signal from the image processing apparatus 100 and a signal from the sensor 90, and an image signal from the image processing apparatus 100. And a storage device 93 in which information for calculating an adjustment amount based on a signal from the sensor 90 is stored.

The arithmetic unit 92 calculates the necessary adjustment amount of the contact pressure adjusting means 94 in accordance with the image information formed on the image carrier 11. In the case of an image or the like, an appropriate adjustment amount of the contact pressure adjusting means 94 is calculated according to the width and direction of the image. The contact pressure adjusting unit 94 is the same as the adjusting unit 84 shown in FIG. 11, and adjusts the contact pressure between the intermediate transfer body 16 and the image carrier 11 based on the adjustment amount calculated according to the image information. It has become. The other configuration of the image forming apparatus is the same as that of the image forming apparatus shown in FIG.

FIG. 13 shows the result of forming an isolated line image as an image sample and examining the relationship between the width of the line image and the load acting on the toner layer in such an image forming apparatus. This figure shows that the load acting on the toner layer changes depending on the thickness (height), width, and direction of the toner layer. Therefore, in order to prevent the occurrence of the hollow portion, it is understood that it is necessary to control not only the contact pressure between the image carrier and the intermediate transfer member but also the load acting on the toner layer precisely. In the image forming apparatus of the present embodiment, the image processing apparatus 1
Since the contact pressure between the intermediate transfer body 16 and the image carrier 11 is controlled according to the image information input from 00, the load acting on the toner layer can be controlled with high accuracy. For this reason, it is possible to form a good image without the occurrence of hollow.

[0065]

As described above, in the image forming apparatus according to the first aspect of the present invention, the contact pressure between the image bearing member and the transfer member is set to be 0.1 mm per 1 cm in the direction perpendicular to the direction of the process. Since the pressure is set to be equal to or less than 06 N, an excessive pressure does not act on the toner image on the image carrier at the time of transfer, and a good image without a hollow portion can be obtained. Further, by setting the contact pressure between the image carrier and the transfer member as described above, the image forming apparatus according to the second aspect of the present invention is stretched over a plurality of supports as a transfer member. Even in a device having a transfer belt and arranged so that the transfer belt is in contact with the image carrier between the supports, it is possible to appropriately prevent the occurrence of hollowing out.

In the image forming apparatus according to the third aspect of the present invention, since the tensile rigidity and the tension of the transfer belt, which are the product of the Young's modulus of the transfer belt and the cross-sectional area, are set appropriately, The contact pressure between the transfer belt and the image carrier can be easily adjusted even when the support has a mechanical error such as eccentricity or when the transfer belt is stretched at small intervals. For this reason, an excessive pressure does not act on the toner image on the image carrier at the time of transfer, and an image without a hollow portion can be obtained. Furthermore, the influence on the belt conveyance performance and the shift of the image position is small, and the occurrence of image quality deterioration can be prevented.

In the image forming apparatus according to the fourth aspect of the present invention, even when there is a mechanical error such as eccentricity in the image carrier or the support, or when the rigidity and tension of the transfer belt are set arbitrarily, The contact pressure between the belt and the image carrier can be set appropriately. For this reason, an excessive pressure does not act on the toner image on the image carrier at the time of transfer, and it is possible to obtain an image without hollowing even when there is a mechanical error such as eccentricity on the image carrier or the support. it can.

In the image forming apparatus according to the fifth aspect of the present invention, the transfer member and the image carrier can be easily controlled by the position regulating member regardless of the conditions such as the rigidity of the transfer belt and the eccentricity of the image carrier and the support roller. The contact pressure with the contact can be adjusted. For this reason, it is possible to prevent an excessive pressure from acting on the toner image on the image carrier at the time of transfer, and it is possible to obtain an image without a hollow portion. Further, there is no restriction on the transfer belt or the support roller for transporting the transfer belt, and the degree of freedom in setting is very high.

In the image forming apparatus according to the present invention, the contact pressure between the transfer belt and the image carrier is detected by a sensor, and the control means determines the contact pressure between the transfer belt and the image carrier based on the output of the sensor. Since the contact pressure is adjusted, the contact pressure between the transfer belt and the image bearing member can be controlled without being affected by the structural conditions such as the rigidity of the belt and the eccentricity of the roller. For this reason, an excessive pressure does not act on the toner image on the image carrier at the time of transfer, and an image without a hollow portion can be obtained.

In the image forming apparatus according to the present invention, since the adjustment amount of the center position of the support roller is controlled based on the output of the sensor, the contact pressure between the transfer belt and the image carrier can be reduced with a simple configuration. Can be adjusted. For this reason, a good image without a hollow portion can be obtained, and there are few restrictions on the transfer belt and the support roller, and the degree of freedom in design becomes very high. Further, since the center position of the support roller is moved so as to keep the belt tension substantially constant, there is no possibility of image quality deterioration such as displacement of an image position due to expansion and contraction of the transfer belt.

In the image forming apparatus according to the present invention, since the tension of the transfer belt is controlled based on the output of the sensor, the contact pressure between the transfer belt and the image carrier can be appropriately adjusted. Therefore, it is possible to obtain a good image without a hollow portion. In addition, there are few restrictions on the transfer belt and the support roller, the configuration can be simplified, and the degree of freedom in design is very high.

In the image forming apparatus according to the ninth aspect of the present invention, since the adjustment amount of the contact pressure adjusting means is determined in accordance with the information of the image formed on the image carrier, the image in which the hollow is likely to occur is formed. When forming the image, the contact pressure between the transfer belt and the image carrier can be appropriately controlled. For this reason, the contact pressure can be controlled without being affected by the structural conditions such as the rigidity of the belt and the eccentricity of the roller, and the occurrence of hollowing can be more reliably prevented.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a color copying machine according to an embodiment of the present invention described in claim 1, 2, 3, or 4;

FIG. 2 is a partial configuration diagram showing an intermediate transfer member and an image carrier used in the color copying machine.

FIG. 3 is a diagram showing a relationship between a load acting on an image carrier of the color copying machine and an amount of occurrence of hollow holes.

FIG. 4 is a diagram showing a relationship between rigidity of a transfer body of the color copying machine and a load acting on an image carrier.

FIG. 5 is a diagram showing a relationship between a distance between rollers of the color copying machine and a load acting on an image carrier.

FIG. 6 is a diagram showing a relationship between the amount of eccentricity of a roller of the color copying machine and a load acting on an image carrier.

FIG. 7 is a partial configuration diagram showing a transfer body and a position regulating member used in the image forming apparatus according to an embodiment of the present invention.

FIG. 8 is a schematic configuration diagram showing an image forming apparatus according to an embodiment of the invention described in claim 6 or 7;

FIG. 9 is a partial configuration diagram illustrating an intermediate transfer member and a contact pressure adjusting unit used in the image forming apparatus.

FIG. 10 is a schematic configuration diagram showing an image forming apparatus according to an embodiment of the present invention.

FIG. 11 is a partial configuration diagram illustrating an intermediate transfer member and a contact pressure adjusting unit used in the image forming apparatus.

FIG. 12 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention.

FIG. 13 is a diagram illustrating a relationship between a width of a line image and a load acting on toner in the image forming apparatus.

FIG. 14 is a diagram illustrating a deflection amount of a transfer belt used in a conventional image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus main body 2 Image reading device 11 Image carrier 12 Charging device 13 Laser beam scanning device 14 Developing device 15 Cleaning device 16 Intermediate transfer body 17 Transfer charger 18 Drive roller 19 Tension rollers 20, 21 Idler roller 22 Backup roller 23 Charging roller 24 Paper tray 25 Paper 26 Feed roller 27 Cleaner 28 Paper transport unit 29 Fixing device 30 Image forming unit 31 Intermediate transfer belt unit 56 Intermediate transfer member 58 Drive roller 59 Tension roller 60 Position regulating member 69, 79, 89 Tension roller 70 , 80, 90 Sensors 71, 81, 91 Amplifiers 72, 82, 92 Computing devices 73, 83, 93 Storage devices 74, 84, 94 Contact pressure adjusting means 75, 85 Eccentric cams 76, 86 Motors 77, 87 Drive transmission member 88 Spring 100 Image processing device

Claims (9)

[Claims] An image carrier on which an electrostatic latent image is formed on a peripheral surface; a developing device for selectively transferring toner to the electrostatic latent image on the image carrier to form a toner image; A transfer member having a peripheral surface formed in an endless shape, the peripheral surface moving in contact with the image carrier, and a toner image on the image carrier being held on the transfer member or the transfer member; An image forming apparatus having a transfer device for electrostatically transferring to a recording material, wherein a contact pressure between the image carrier and the transfer body is 0.06 N or less per 1 cm in a direction perpendicular to a process direction. An image forming apparatus characterized by being set as follows. 2. The image forming apparatus according to claim 1, wherein the transfer member is a transfer belt stretched over a plurality of supports, and the transfer belt contacts the image carrier between the supports. An image forming apparatus characterized by being arranged as follows. 3. The image forming apparatus according to claim 2, wherein a tensile stiffness, which is a product of a Young's modulus of the transfer belt and a cross-sectional area, is 3 × 10 ⁵ N or less, and the tension between the supports is 80 N or less. An image forming apparatus, wherein the image forming apparatus is stretched over the image forming apparatus. 4. The image forming apparatus according to claim 2, wherein a stretch interval of a portion of the transfer belt that contacts the image carrier is 100 mm or more. 5. An image carrier on which an electrostatic latent image is formed on a peripheral surface; a developing device for selectively transferring toner to the electrostatic latent image on the image carrier to form a toner image; A transfer member that is stretched around a plurality of support rollers and moves endlessly in a circumferential direction, wherein a transfer belt having a peripheral surface in contact with the image carrier between positions supported by the support roller; A transfer device for electrostatically transferring the upper toner image onto the transfer member or onto a recording material held on the transfer member; and a contact position between the transfer belt and the image carrier. An image forming apparatus comprising: a position regulating member which is in contact with an outer peripheral surface of the transfer belt and restricts a position of the transfer belt. 6. An image carrier on which an electrostatic latent image is formed on a peripheral surface; a developing device for selectively transferring toner to the electrostatic latent image on the image carrier to form a toner image; A belt member stretched around a plurality of support rollers and moving endlessly in a circumferential direction, wherein a transfer belt having a peripheral surface in contact with the image carrier between positions supported by the support roller; and the image carrier. A transfer device for electrostatically transferring the upper toner image onto the transfer member or onto a recording material held on the transfer member; and a contact pressure between the transfer belt and the image carrier. A contact pressure adjusting unit that adjusts a contact pressure between the transfer belt and the image carrier, and a control unit that controls an adjustment amount of the contact pressure adjusting unit based on an output of the sensor. An image forming apparatus comprising: 7. The image forming apparatus according to claim 6, wherein the adjusting unit changes a center position of a support roller that stretches the image carrier or the transfer belt. Forming equipment. 8. The image forming apparatus according to claim 6, wherein the adjusting unit adjusts a tension of the transfer belt. 9. The image forming apparatus according to claim 6, wherein the control unit determines an adjustment amount according to information of an image formed on the image carrier. Forming equipment.