JP4104843B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile.
[0002]
[Prior art]
In an image forming apparatus using an electrophotographic method or an electrostatic recording method, after the photosensitive drum is uniformly charged, the photosensitive drum is scanned with a laser beam to form an electrostatic latent image on the surface of the photosensitive drum, The electrostatic latent image is developed with toner to form a toner image on the surface of the photosensitive drum, and the toner image is transferred to a recording sheet and fixed.
[0003]
In such an image forming apparatus, the resolution of an image is increasing, and a resolution of 600 dpi (number of dots / inch) or 1200 dpi is realized. Also, the resolution can be switched. For example, 600 dpi and 1200 dpi can be switched appropriately.
[0004]
However, in order to keep the image process speed (recording speed in the sub-scanning direction) constant while switching the resolution, it is necessary to change the main scanning speed of the photosensitive drum. For this purpose, the laser beam scanner unit The rotation speed of the polygon mirror must be changed. For example, when the resolution is switched from 600 dpi to 1200 dpi, the rotational speed of the polygon mirror must be doubled. However, the rotational speed of the polygon mirror has already been sufficiently increased, and it is technically difficult to further increase the rotational speed, and an increase in cost is inevitable.
[0005]
For this reason, when the resolution is switched, the image process speed is changed to keep the scanning speed of the photosensitive drum constant. For example, when the resolution is switched from 600 dpi to 1200 dpi, the image process speed is reduced by half to keep the scanning speed of the photosensitive drum constant.
[0006]
On the other hand, in the image forming apparatus, the toner, the photosensitive drum, the recording paper, the transfer roller, and the like are charged to adsorb the toner. Specifically, the electrostatic latent image on the surface of the photosensitive drum is charged with a polarity opposite to that of the toner, and the toner is attached to the electrostatic latent image. Further, the recording paper is charged to a polarity opposite to that of the toner by the transfer roller, and the toner image is transferred from the photosensitive drum to the recording paper.
[0007]
Also, in order to transfer the toner image from the photosensitive drum to the recording sheet with certainty, the outer peripheral speed of the transfer roller is slightly higher than the outer peripheral speed of the photosensitive drum, that is, the peripheral speed of the transfer roller with respect to the photosensitive drum. The recording paper is rubbed against the photosensitive drum by slightly increasing the ratio. In general, the peripheral speed ratio of the transfer roller to the photosensitive drum is often set to about 102%. If the outer peripheral speed of the transfer roller is set to be the same as the outer peripheral speed of the photosensitive drum and the peripheral speed ratio is set to 100%, a phenomenon that a part of the toner image is not easily transferred onto the recording paper is likely to occur. Character omissions occur.
[0008]
For example, in Japanese Patent Laid-Open No. 6-258966, the peripheral speed ratio of the transfer roller to the photosensitive drum is changed in accordance with the thickness of the recording paper, thereby transferring the toner image to the recording paper of any thickness. The technique of performing this well is disclosed.
[0009]
Japanese Patent Application Laid-Open No. 8-160783 discloses that the peripheral speed ratio of the transfer roller to the photosensitive drum is changed in accordance with the charge amount per unit weight of the toner, whereby the toner image is always transferred satisfactorily. Technology is disclosed.
[0010]
[Problems to be solved by the invention]
By the way, the inventors of the present invention have clarified that the optimum peripheral speed ratio of the transfer roller to the photosensitive drum varies depending on the process speed of the image, the use environment condition, and the load acting on the recording paper being conveyed. did. However, conventionally, since the peripheral speed ratio of the transfer roller to the photosensitive drum is set only in accordance with the thickness of the recording paper and the charge amount of the toner, the optimal peripheral speed ratio is not necessarily set.
[0011]
Therefore, the present invention has been made in view of the above-described conventional problems, and the optimum transfer roller for the photosensitive drum is selected according to the process speed of the image, the use environment condition, and the load acting on the recording paper being conveyed. An object of the present invention is to provide an image forming apparatus capable of setting a proper peripheral speed ratio.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention develops an electrostatic latent image formed on the surface of a photoreceptor with toner, forms a toner image on the surface of the photoreceptor , contacts the transfer body with the photoreceptor , and transfers the image. while the body and the photosensitive member is rotated in the opposite directions, placed guide the recording paper between the transfer member and the photosensitive member, an image forming apparatus for transferring the toner image to the recording medium from the photosensitive member, than the peripheral speed of the photosensitive member And a control means for adjusting the peripheral speed ratio of the transfer member to the photosensitive member by slightly increasing the peripheral speed of the transfer member, and a use environment detection means for detecting the temperature and humidity of the use environment of the image forming apparatus, It said control means, while maintaining the peripheral speed peripheral speed ratio the peripheral speed of the transfer member is slightly higher than the photosensitive member, as the temperature and humidity detected by the use environment detection means is lower, the photosensitive member The peripheral speed ratio of the transfer body with respect to is greatly adjusted.
[0013]
According to the present invention having such a configuration, the peripheral speed ratio of the transfer member to the image carrier is adjusted in accordance with the selected process speed. For this reason, an appropriate peripheral speed ratio of the transfer body can be set no matter what process speed is selected.
[0014]
In the present invention, the control means increases the peripheral speed ratio of the transfer member to the image carrier as the selected process speed decreases.
[0015]
As a result, it is possible to maintain good image quality.
[0016]
Next, according to the present invention, a recording sheet is introduced between the transfer member and the image carrier while the transfer member is brought into contact with the image carrier and the transfer member and the image carrier are rotated in opposite directions. The image forming apparatus for transferring the toner image from the recording medium to the recording medium is provided with control means for adjusting the peripheral speed ratio of the transfer body to the image carrier in accordance with the use environment conditions.
[0017]
According to the present invention having such a configuration, the peripheral speed ratio of the transfer member to the image carrier is adjusted according to the use environment conditions. For this reason, an appropriate peripheral speed ratio of the transfer body can be set under any use environment condition.
[0018]
In the present invention, the use environment conditions are temperature and humidity, and the control means increases the peripheral speed ratio of the transfer member to the image carrier as the temperature and humidity decrease.
[0019]
As a result, it is possible to maintain good image quality.
[0020]
Next, according to the present invention, a recording sheet is introduced between the transfer member and the image carrier while the transfer member is brought into contact with the image carrier and the transfer member and the image carrier are rotated in opposite directions. In an image forming apparatus for transferring a toner image from a recording medium to a recording medium, a plurality of paper feeding means for supplying recording paper, and a transfer body for an image carrier depending on which of the paper feeding means supplies the recording paper The control means which adjusts the peripheral speed ratio is provided.
[0021]
Alternatively, according to the present invention, a recording sheet is introduced between the transfer member and the image carrier while the transfer member is brought into contact with the image carrier and the transfer member and the image carrier are rotated in opposite directions. An image forming apparatus that transfers a toner image onto a recording medium includes a control unit that adjusts a peripheral speed ratio of the transfer body to the image carrier in accordance with a load acting on the recording paper being conveyed.
[0022]
According to the present invention having such a configuration, the circumference of the transfer body with respect to the image carrier depends on which of the paper feeding units supplies the recording paper or the load acting on the recording paper being conveyed. The speed ratio is adjusted. Which of the paper feeding units supplies the recording paper is synonymous with what load is applied to the recording paper being conveyed. In any case, an appropriate peripheral speed ratio of the transfer member can always be set.
[0023]
In the present invention, the transfer body includes either a transfer roller or a transfer belt.
[0024]
That is, the transfer body may be either a transfer roller or a transfer belt.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0026]
FIG. 1 is a side view showing an embodiment of the image forming apparatus of the present invention. In FIG. 1, a document table 1 is made of transparent glass or the like, and a document S is placed thereon. A scanner unit 2 is disposed below the document table 1. The scanner unit 2 includes a light source 3 that irradiates light on the document S on the document table 1, reflecting mirrors 4, 5, and 6 that guide reflected light from the document S along a path indicated by a dotted line, and the reflected light. A lens 7 for focusing and imaging the original S on a photoelectric conversion element (hereinafter referred to as CCD) 8 and a CCD 8 for reading the original S are provided.
[0027]
When reading the document S, the CCD 8 outputs image data indicating the document S to a laser scanning unit (hereinafter referred to as LSU) 16. The LSU 16 modulates the laser beam according to the image data and irradiates the surface of the photosensitive drum 22 with this laser beam. The photosensitive drum 22 rotates in one direction, and its surface is charged by the charging device 18 and then irradiated with laser light to form an electrostatic latent image on the surface. The developing device 23 develops the electrostatic latent image on the surface of the photosensitive drum 22 with toner to form a toner image. The transfer roller 19 transfers the toner image on the surface of the photosensitive drum 22 to the recording paper P that has been conveyed. The cleaning device 17 removes residual toner on the surface of the photosensitive drum 22.
[0028]
On the other hand, a large number of recording sheets P are stored in the sheet feeding cassette 25. The uppermost recording paper P is pulled out by the calling roller 21 at the front end of the paper feed cassette 25, and the photosensitive drum 22 side is passed through a suction part 26 composed of a paper feed roller and a friction plate (or a paper feed roller and a reverse roller). It is conveyed to. The leading edge of the recording paper P is detected by the pre-registration detection switch 12 and is temporarily stopped immediately before each PS roller 20. The recording paper P is conveyed between the photosensitive drum 22 and the transfer roller 19 by each PS roller 20 in accordance with the transfer timing of the toner image from the photosensitive drum 22.
[0029]
When the toner image is transferred to the recording paper P, the recording paper P passes between the fixing roller 13 and the fixing roller 14 incorporating the heater 15 and is heated and pressurized. As a result, the toner image on the recording paper P is fixed. Further, the recording paper P passes through the fixing paper detection switch 11 and the paper discharge detection switch 10, passes between the paper discharge rollers 9, and is discharged to the paper discharge tray 24.
[0030]
FIG. 2 is a block diagram showing a rotation control system of the photosensitive drum 22 and the transfer roller 19. In FIG. 2, a central processing unit (hereinafter referred to as CPU) 31 controls the image forming apparatus in an integrated manner, performs data communication with an external host computer 32, and displays data from the display operation unit 33. In response to the instructions and detection outputs of the temperature sensor 34 and the humidity sensor 35, various processes are selectively performed.
[0031]
Further, the CPU 31 controls the rotation drive motor 37 of the photosensitive drum 22 and the rotation drive motor 38 of the transfer roller 19 through the rotation control unit 36. Here, each rotational drive is performed so that the outer peripheral speed of the transfer roller 19 is slightly higher than the outer peripheral speed of the photosensitive drum 22, that is, the peripheral speed ratio of the transfer roller 19 to the photosensitive drum 22 is slightly increased. The rotational speed of the motors 37 and 38 is adjusted. As a result, when the recording paper P passes between the photosensitive drum 22 and the transfer roller 19, the recording paper P is rubbed against the photosensitive drum 22, and the toner image is favorably transferred from the photosensitive drum 22 to the recording paper P. The
[0032]
Further, the CPU 31 sets an optimum peripheral speed ratio of the transfer roller 19 with respect to the photosensitive drum 22 in accordance with an image process speed, use environment conditions (temperature and humidity), and a load acting on the recording paper P being conveyed. is doing.
[0033]
For example, in the image forming apparatus, the resolution is switched between 600 dpi and 1200 dpi by an input operation of the display operation unit 33, and an image with the set resolution is formed. When the resolution is 600 dpi, the image process speed PS is set. When the resolution is 1200 dpi, the image process speed PS / 2 is set. The process speed PS / 2 when the resolution is 1200 dpi is half of the process speed PS when the resolution is 600 dpi. When the resolution of 600 dpi is set, the CPU 31 sets the peripheral speed ratio of the transfer roller 19 to the photosensitive drum 22 to 101%, and when the resolution of 1200 dpi is set, the CPU 31 sets the peripheral speed ratio to 103%. Therefore, as shown in the chart of FIG. 3, when the image process speed is high, the peripheral speed ratio of the transfer roller 19 to the photosensitive drum 22 is set to 101%, and when the image process speed is low, the peripheral speed is set. The speed ratio is set to 103%.
[0034]
FIG. 4 shows a characteristic curve A1 representing a change in image quality with respect to the peripheral speed ratio when the image process speed is high, and a characteristic curve A2 representing a change in image quality with respect to the peripheral speed ratio when the image process speed is low. It is a graph. As is apparent from this graph, both the characteristic curve A1 and the characteristic curve A2 have a peak of the peripheral speed ratio that provides the best image quality, and in order to obtain the best image quality, the image process speed is high. The peripheral speed ratio at this time is set to 101%, and the peripheral speed ratio when the image process speed is low must be set to 103%.
[0035]
If the image process speed is high, the conveyance speed of the recording paper P is high. If the peripheral speed ratio of the transfer roller 19 to the photosensitive drum 22 is not reduced at this time, the rubbing of the recording paper P against the photosensitive drum 22 is excessive. As a result, the image quality deteriorates. Accordingly, when the image process speed is high, the peripheral speed ratio that provides the best image quality is reduced.
[0036]
On the other hand, as shown in the chart of FIG. 3, the peripheral speed ratio has been set to a constant 102%, for example, regardless of changes in the process speed of the image. In the same way, the best image quality could not be obtained.
[0037]
The CPU 31 also receives detection outputs from the temperature sensor 34 and the humidity sensor 35 and adjusts the peripheral speed ratio of the transfer roller 19 to the photosensitive drum 22 in accordance with the temperature and humidity indicated by these detection outputs. For example, as shown in the chart of FIG. 5, in the case of low temperature and low humidity, the peripheral speed ratio when the image process speed is high is set to 101.2%, and the peripheral speed ratio when the image process speed is low is 103. Set to 2%. In the case of normal temperature and humidity, the peripheral speed ratio when the image process speed is high is set to 101%, and the peripheral speed ratio when the image process speed is low is set to 103%. Further, in the case of high temperature and high humidity, the peripheral speed ratio when the image process speed is high is set to 100.8%, and the peripheral speed ratio when the image process speed is low is set to 102.8%.
[0038]
The adhesion of the toner becomes better as the temperature and humidity become higher. For this reason, when the temperature and humidity are high, the peripheral speed ratio that provides the best image quality is small. Conversely, when the temperature is low and the humidity is low, the peripheral speed ratio that provides the best image quality increases.
[0039]
FIG. 6 is a graph showing a characteristic curve B1 representing a change in image quality with respect to use environment conditions in the present embodiment and a characteristic curve B2 showing a change in image quality with respect to conventional use environment conditions. According to the characteristic curve B1 of the present embodiment, the image quality is well maintained regardless of changes in the use environment conditions. Further, according to the conventional characteristic curve B2, the image quality is changed due to the change of the use environment condition, and the image quality is remarkably deteriorated at low temperature and low humidity.
[0040]
Further, in the image forming apparatus, an input operation of the display operation unit 33 instructs one of paper feeding from the paper feeding cassette 25 and paper feeding from a manual feed tray (not shown), and feeding from the paper feeding cassette 25 is performed. When paper is instructed, the recording paper P is supplied from the paper feed cassette 25, and when paper supply from the manual feed tray is instructed, the recording paper P is supplied from the manual feed tray. The CPU 31 adjusts the peripheral speed ratio of the transfer roller 19 with respect to the photosensitive drum 22 depending on whether paper feeding from the paper feeding cassette 25 or paper feeding from the manual feed tray is performed. For example, as shown in the chart of FIG. 7, in the case of paper feed from the paper feed cassette 25, the peripheral speed ratio when the image process speed is high is set to 101%, and the peripheral speed when the image process speed is low is set. The speed ratio is set to 103%. In the case of paper feeding from the manual feed tray, the peripheral speed ratio when the image process speed is high is set to 100.8%, and the peripheral speed ratio when the image process speed is low is set to 102.8%. To do.
[0041]
In the case of paper feeding from the manual feed tray, the load acting on the recording paper P being conveyed is small. If the peripheral speed ratio of the transfer roller 19 to the photosensitive drum 22 is not reduced at this time, recording on the photosensitive drum 22 is performed. The rubbing of the paper P becomes excessive and the image quality deteriorates. Therefore, in the case of paper feeding from the manual feed tray, the peripheral speed ratio that provides the best image quality is reduced.
[0042]
FIG. 8 is a graph showing a characteristic curve C1 representing a change in image quality with respect to the paper feeding method in this embodiment and a characteristic curve C2 representing a change in image quality with respect to the conventional paper feeding method. According to the characteristic curve C1 of this embodiment, the image quality is kept good regardless of the paper feeding method. Further, according to the conventional characteristic curve C2, the image quality changes depending on the paper feeding method, and the image quality is significantly deteriorated when paper is fed from the paper feeding cassette 25.
[0043]
As described above, in the image forming apparatus of the present embodiment, the transfer roller 19 with respect to the photosensitive drum 22 depends on the process speed of the image, the use environment conditions (temperature and humidity), and the load acting on the recording paper P being conveyed. Since the optimum peripheral speed ratio is set, the toner image is always transferred satisfactorily from the photosensitive drum 22 to the recording paper P, and the image quality can be kept good.
[0044]
In addition, this invention is not limited to the said embodiment, It can deform | transform variously. For example, instead of adjusting the peripheral speed ratio, the load acting on the recording paper P being conveyed is directly measured according to whether the paper is fed from the paper feed cassette 25 or the manual feed tray. The peripheral speed ratio may be adjusted according to the above. This is because it is synonymous with whether the paper is fed from the paper feed cassette 25 or the manual feed tray and what is the load acting on the recording paper P being conveyed. Further, even if a transfer belt is employed instead of the transfer roller, similar effects can be achieved by applying the present invention.
[0045]
【The invention's effect】
As described above, according to the present invention, the peripheral speed ratio of the transfer member to the image carrier is adjusted according to the selected process speed. For this reason, an appropriate peripheral speed ratio of the transfer body can be set no matter what process speed is selected.
[0046]
According to the present invention, the peripheral speed ratio of the transfer member to the image carrier is adjusted in accordance with the use environment conditions. For this reason, an appropriate peripheral speed ratio of the transfer body can be set under any use environment condition.
[0047]
Further, according to the present invention, the peripheral speed ratio of the transfer body to the image carrier is set according to which of the paper feeding units supplies the recording paper or according to the load acting on the recording paper being conveyed. It is adjusting. Which of the paper feeding units supplies the recording paper is synonymous with what load is applied to the recording paper being conveyed. In any case, an appropriate peripheral speed ratio of the transfer member can always be set.
[Brief description of the drawings]
FIG. 1 is a side view showing an embodiment of an image forming apparatus of the present invention.
2 is a block diagram showing a rotation control system of a photosensitive drum and a transfer roller in the apparatus of FIG.
3 is a chart showing a peripheral speed ratio of a transfer roller to a photosensitive drum and a conventional peripheral speed ratio in the apparatus of FIG. 1;
4 is a graph showing a relationship between a peripheral speed ratio of a transfer roller to a photosensitive drum and image quality in the apparatus of FIG.
5 is a table showing a relationship between a peripheral speed ratio of a transfer roller to a photosensitive drum and use environment conditions in the apparatus of FIG.
FIG. 6 is a graph showing changes in image quality with respect to use environment conditions.
7 is a table showing a relationship between a peripheral speed ratio of a transfer roller to a photosensitive drum and a paper feeding method in the apparatus of FIG. 1;
FIG. 8 is a graph illustrating a change in image quality with respect to a paper feeding method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Document stand 2 Scanner part 3 Light source 4, 5, 6 Reflector 7 Lens 8 CCD
9 Paper discharge rollers 13, 14 Fixing roller 16 LSU
17 Cleaning Device 18 Charging Device 19 Transfer Roller 20 PS Roller 22 Photosensitive Drum 23 Developing Device 25 Paper Feed Cassette 31 Central Processing Unit (CPU)
32 External host computer 33 Display operation unit 34 Temperature sensor 35 Humidity sensor 36 Rotation control units 37 and 38 Rotation drive motor

Claims (4)

The electrostatic latent image formed on the surface of the photosensitive member is developed with toner, a toner image is formed on the surface of the photosensitive member, the transfer member is brought into contact with the photosensitive member , and the transfer member and the photosensitive member are rotated in opposite directions. Meanwhile, in an image forming apparatus for introducing a recording sheet between a transfer member and a photosensitive member and transferring a toner image from the photosensitive member to a recording medium,
Slightly higher peripheral speed of the transfer member than the peripheral speed of the photosensitive member, and control means for adjusting the peripheral speed ratio of the transfer member to the photosensitive member,
Use environment detection means for detecting the temperature and humidity of the use environment of the image forming apparatus,
It said control means, while maintaining the peripheral speed peripheral speed ratio the peripheral speed of the transfer member is slightly higher than the photosensitive member, as the temperature and humidity detected by the use environment detection means is lower, the photosensitive member An image forming apparatus characterized by largely adjusting a peripheral speed ratio of a transfer body to the above. The control means sets a peripheral speed ratio so that the toner image transferred to the recording medium has the best image quality while maintaining the image process speed set by the image forming apparatus. 2. The peripheral speed ratio is a peripheral speed ratio at which the peripheral speed of the transfer member is slightly higher than the peripheral speed of the photosensitive member , and the peripheral speed ratio is adjusted according to temperature and humidity. The image forming apparatus described. A plurality of paper feeding means for supplying recording paper;
The image forming apparatus according to claim 1, wherein the control unit adjusts a peripheral speed ratio of the transfer member to the photosensitive member according to which of the sheet feeding units supplies the recording paper.   The image forming apparatus according to claim 1, wherein the transfer body includes one of a transfer roller and a transfer belt.

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