JP2002202691A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of forming a favorable image of a stable image length being a sub-scanning directional image forming magnification irrespective of an image ratio being a toner quantity on a photoreceptor. SOLUTION: When a paper form size is detected and the detected paper form size and image data are inputted to a main control part, the image data are developed into an image and the number of the pixels are counted by the main control part. In the main control part, a rotating speed of a polygon motor is previously set according to the image ratio, and the main control part calculates the image ratio based on the number of the counted pixels and the paper form size, and then controls a polygon motor driving circuit at the rotating speed of the polygon motor according to the preset image ratio.

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, a facsimile machine, and a printer, in which the rotation speed of a polygon motor or a scanner motor is variable.

[0002]

2. Description of the Related Art In recent years, facsimile machines, copiers, and the like that form images using a contact transfer method using a transfer roller or the like have been developed.
Image forming apparatuses such as printing apparatuses are used. In these image forming apparatuses, a part of the toner that forms the character image may not be transferred, resulting in missing characters. As a measure to prevent such missing characters during image formation,
There has been proposed a method in which a peripheral speed difference is provided between a photosensitive member and a transfer roller, and a transfer sheet is fed at a transfer portion by slipping the transfer sheet with respect to the photosensitive member.

[0003]

However, in the method in which the transfer paper is slipped with respect to the photoreceptor and fed, the friction coefficient between the transfer paper and the photoreceptor changes depending on the image rate which is the amount of toner on the photoreceptor. Therefore, the transfer speed of the transfer paper in the transfer unit is not stable, and the image length, which is the image forming magnification in the sub-scanning direction, may vary. Further, when a difference occurs between the sheet conveyance speed of the registration roller set above the sheet conveyance portion with respect to the photoconductor of the image forming apparatus and the sheet conveyance speed of the transfer unit, the difference in the sheet conveyance speed causes the difference between the registration roller and the sheet conveyance speed. There is a case where a loop occurs on the sheet between the transfer units or the sheet is pulled, so that the image length varies. Variations in the image length due to the difference between the paper transport speed of the registration roller and the paper transport speed of the transfer unit can be suppressed by using the same transfer unit and the registration roller. It has been proposed to reduce it to the limit that can be processed.

However, two or more paper feeding means are provided,
When the back tension, which is the load applied to the registration rollers by the plurality of paper feeding units, differs depending on the registration rollers of each paper feeding unit, the paper conveyance rate and image length of the paper feeding unit differ because the paper slip ratio at the registration rollers differs. A magnification error occurs. That is, when a sheet is conveyed from a sheet feeding unit having a small sheet feeding load, the sheet is conveyed from the sheet feeding unit having a large sheet feeding load because the sheet conveying speed is high and the image length is long because the slip ratio at the registration roller is small. In this case, the slip ratio at the registration roller is large,
The paper transport speed becomes slow and the image length becomes short.

In an image forming apparatus, an electrostatic latent image on a photosensitive member is transferred to a transfer sheet by pushing a sheet into a transfer roller section by a registration roller. However, the force of pushing the transfer paper into the transfer portion by the registration roller differs depending on the rigidity due to the thickness of the transfer paper. For example, when the stiffness of the transfer paper is large, that is, when the transfer paper is thick and the flexibility is low, the paper transport speed at the transfer unit is high. On the other hand, when the stiffness of the transfer paper is small, that is, when the transfer paper is thin and has high flexibility, the paper transport speed at the transfer unit is slow. As a result, when the transfer paper has a thickness such as a postcard, the image length becomes longer, and when the transfer paper is thin, the image length becomes shorter.

Accordingly, a first object of the present invention is to perform good image formation in which the image length, which is the image formation magnification in the sub-scanning direction, is stable regardless of the image ratio, which is the amount of toner on the photosensitive member. It is an object of the present invention to provide an image forming apparatus capable of performing the above. A second object of the present invention is to provide an image forming apparatus capable of performing stable image formation with a stable image length, which is the image formation magnification in the sub-scanning direction, regardless of the sheet conveyance speed of each sheet feeding unit. That is. A third object of the present invention is to provide an image forming apparatus capable of performing stable and good image formation regardless of the thickness of a transfer sheet.

[0007]

According to the first aspect of the present invention, an image signal receiving means for receiving an image signal of a document and a polygon motor driven at a predetermined number of rotations to receive the image signal by the image signal receiving means. Image forming means for forming an image signal as an electrostatic latent image on a photoreceptor, sheet feeding means for feeding a sheet for forming an image of the image signal received by the image signal receiving means, and image forming means Image forming means for forming an image of the electrostatic latent image on the photoreceptor formed on the sheet fed by the sheet feeding means, wherein the image forming means receives the image by the image signal receiving means. The first object is achieved by switching the number of revolutions of the polygon motor in accordance with the image signal and the size of the paper fed by the paper feeding means.

According to the second aspect of the present invention, the image signal received by the image signal receiving means is driven by the image signal receiving means for receiving an image signal of the original and the polygon motor by driving the polygon motor at a predetermined rotation speed. An image forming unit for forming an image as an electrostatic latent image thereon, a sheet feeding unit for feeding a sheet on which an image signal received by the image signal receiving unit is formed, and a plurality of sheet feeding units. Selection means for selecting which paper supply means to feed paper from among the paper supply means, and the electrostatic latent image formed on the photoreceptor formed by the image formation means is supplied by the paper supply means. An image forming unit for forming an image on a sheet, wherein the image forming unit switches the number of rotations of the polygon motor in accordance with the sheet feeding unit selected by the selecting unit, thereby forming the second image.
Achieve the objectives.

According to a third aspect of the present invention, the image signal received by the image signal receiving means is driven by the image signal receiving means for receiving the image signal of the original and the polygon motor driven at a predetermined rotation speed. Image forming means for forming an image thereon as an electrostatic latent image, sheet feeding means for feeding a sheet for forming an image of the image signal received by the image signal receiving means, and sheet fed from the sheet feeding means Image forming means further comprising a detecting means for detecting the thickness of the electrostatic latent image formed on the photoreceptor formed by the image forming means on a sheet fed by the sheet feeding means, The image forming means achieves the third object by switching the number of revolutions of the polygon motor according to the thickness of the sheet detected by the detecting means.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. FIG.
1 is a schematic cross-sectional view showing an entire configuration of a digital copying machine according to the present embodiment. As shown in FIG. 1, an image forming unit 1 is arranged at the center of the digital copying machine, and two paper feeding units, a cassette paper feeding unit 2 and a manual paper feeding unit 3, are provided. Below the image forming section 1, a cassette sheet feeding section 2 is provided.
Is arranged. The paper feed unit 2 includes a paper feed cassette 21. Although the manual paper feed unit 3 is disposed on the right side, a paper feed device such as the cassette paper feed unit 2 or the manual paper feed unit 3 can be additionally provided as necessary.
A document reading unit 30 for reading a document is provided above the image forming unit 1. A paper discharge storage unit 4 is formed between the image forming unit 1 and the document reading unit 30, and a recording medium (hereinafter, referred to as a sheet) on which an image is formed is discharged and stored in the paper discharge storage unit 4.

The image forming section 1 includes a drum-shaped photosensitive member 5.
A charging device 6 for charging the surface of the photoconductor 5 around the photoconductor 5; an exposure device 7 for irradiating the surface of the photoconductor 5 with laser light for image information; A developing device 8 for visualizing the transferred electrostatic latent image, a transfer device 9 for transferring a toner image developed on the photoconductor 5 to a sheet, a cleaning device 10 for removing and collecting toner remaining on the photoconductor surface after transfer, and the like. Are located. Further, a fixing device 11 for fixing the toner on the paper on which the toner image is formed is provided.
Is disposed below the image forming apparatus (downstream in the sheet transport path). The sheet that has passed through the fixing device 11 is discharged and stored in the discharge storage unit 4 by the discharge device 12.

The cassette paper feed unit 2 includes a paper feed cassette 21
Unused paper is stored in the paper feed roller, and a bottom plate 22 rotatably supported presses the uppermost paper against a paper feed roller 23 and is pressed by a spring 24 so as to be conveyed. Due to the rotation of the paper feed roller 23, the uppermost sheet is sent out from the paper feed cassette 21 and conveyed to the registration roller 14. The registration roller 14 is controlled so that the conveyance of the sheet is temporarily stopped, and the registration roller 14 starts rotating at a timing so that the positional relationship between the toner image on the surface of the photoconductor 5 and the leading end of the sheet becomes a predetermined position. The manual feed unit 3 has a configuration in which a manual tray is rotatable in the direction of the arrow A or the arrow B. When used, the manual tray is opened to the right so that sheets can be supplied. The manual feed bottom plate (not shown) rotatably supported is pressed by a spring (not shown) so that the uppermost sheet is conveyed by the manual feed roller 25. Due to the rotation of the manual feed roller 25, the uppermost sheet is sent out from the manual feed unit 3 and is conveyed to the registration roller 14.

In the document reading section 30, a reading traveling body 31 composed of a light source for document illumination and a mirror reciprocates in order to perform reading scanning of a document (not shown) placed on a contact glass 32. The image information scanned by the reading traveling body 31 is read as an image signal by a CCD (photoelectric conversion element) 34 installed behind the lens 33. The read image signal is digitized and processed. Based on the image-processed signal, a laser diode (L
D) emits light, and this emission forms an electrostatic latent image on the surface of the photoconductor 5. The optical signal from the LD reaches the photoconductor 5 via a polygon mirror or a lens.
Although not shown, an automatic document feeder for automatically feeding the original onto the contact glass 32 or a pressure plate for holding the original is attached above the original reading unit 30.

In this embodiment, a digital copier which scans and reads an original, digitizes the original, and copies it on paper will be described as an example of an image forming apparatus.
However, the present invention is not limited to this, and an image forming apparatus such as a facsimile apparatus for exchanging image information of a document with a remote place by a control device (not shown) or a so-called network printer apparatus for printing image information handled by a computer on paper. May be. Also in the case of these image forming apparatuses, all the formed images are discharged and stored in one discharge storage unit 4. The paper stacked in the paper discharge storage unit 4 is in a state in which the image-formed side faces down, and even if the processing order of the originals handled by copying, facsimile, and printer is performed from one page and printed, the paper is discharged. When it is taken out from the paper storage unit 4, the first page is at the top, so that it is not necessary to perform an operation such as aligning the pages again.

FIG. 2 is a perspective view of the digital copying machine according to the present embodiment. As shown in FIG.
Can be performed from the front of the digital copier, and the operation of the paper feed cassette 21 for replenishing paper can also be performed from the front. When the manual paper feed unit 3 is used, the manual paper tray on the right side can be opened to supply paper.

Next, first to third embodiments which are image forming operations of a digital copying machine will be described. The digital copying machine is provided with a control unit (not shown). The control unit controls the document reading unit 30, the image forming unit 1, the cassette feeding unit 2, and the like, and can form an image on a sheet. It should be able to do it.
FIG. 3 is a control block diagram illustrating an image forming operation according to the first embodiment. When the paper size is detected and the detected paper size and image data are input to the main control unit, the main control unit expands the image data and counts the number of pixels. The number of rotations of the polygon motor according to the image ratio is set in the main control unit in advance, and the main control unit calculates the image ratio based on the counted number of pixels and the paper size, and then sets the image ratio in advance. The polygon motor driving circuit is controlled by the rotation speed of the polygon motor according to the image ratio.

Here, the image length, which is the image forming magnification in the sub-scanning direction, varies according to the rotation speed of the polygon motor of the exposure device (writing unit) 7. When the rotation speed of the polygon motor is increased with respect to the paper conveyance speed, the latent image on the photoconductor 5 becomes shorter, and when the rotation speed is reduced with respect to the paper conveyance speed, the latent image on the photoconductor 5 becomes longer. As described above, since the driving of the polygon motor is controlled by the rotation speed of the polygon motor according to the preset image ratio, it is possible to form an image having an appropriate image length corresponding to the image ratio on a sheet. FIG. 4 is a diagram showing the relationship between the image ratio and the image length.

FIG. 5 is a control block diagram for explaining an image forming operation according to the second embodiment. The rotation speed of the polygon motor is set in the main control unit in advance depending on whether the sheet is fed from the sheet feeding cassette 21 or the manual sheet feeding unit 3. When cassette paper feed (paper feed from the paper feed cassette 21) or manual paper feed (paper feed from the manual paper feed unit 3) is selected in an operation unit (not shown), the main control unit responds to the paper feed position. Determine the number of rotations of the polygon motor. The polygon motor drive circuit is controlled by the polygon motor rotation speed preset according to the paper feed point selected in this way, so that regardless of the load of each paper feed unit that differs depending on each paper feed location. Thus, an image having an appropriate image length can be formed on a sheet. FIG. 6 is a diagram illustrating the relationship between the load by the sheet feeding unit and the image length.

FIG. 7 is a control block diagram for explaining an image forming operation according to the third embodiment. Digital copiers
It is assumed that a paper thickness detecting unit for detecting the thickness of the transfer paper is provided at the paper feeding unit or below the paper feeding unit. The number of rotations of the polygon motor according to the thickness of the transfer paper is preset in the main control unit, and the number of rotations of the polygon motor is determined according to the thickness of the transfer paper detected by the paper thickness detection unit. It is supposed to be. Also, the thickness of the transfer paper can be input from an operation unit (not shown). In this case, the main control unit also determines the rotation speed of the polygon motor according to the input thickness of the transfer paper. In this way, the rotation speed of the polygon motor can be determined according to the thickness of the transfer paper to control the driving of the polygon motor, so that an image having an appropriate image length can be formed on the paper regardless of the thickness of the transfer paper. Can be done. FIG.
FIG. 4 is a diagram showing a relationship between transfer paper thickness and image length.

[0020]

According to the first aspect of the present invention, the image forming means includes:
Since the rotation speed of the polygon motor is switched in accordance with the image signal received by the image signal receiving means and the size of the paper fed by the paper feeding means, an appropriate polygon motor rotation speed can be controlled by the image ratio. A good image having a stable image length can be obtained.

According to the second aspect of the present invention, the image forming means switches the number of rotations of the polygon motor in accordance with the paper feeding means selected by the selecting means. The number of rotations of the polygon motor can be controlled, and a good image having a stable image length can be obtained irrespective of each paper feeding point used.

According to the third aspect of the present invention, the image forming means switches the number of rotations of the polygon motor in accordance with the thickness of the sheet detected by the detecting means. The number of rotations can be controlled,
A good image having a stable image length can be obtained regardless of the thickness of the transfer paper used.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an entire configuration of a digital copying machine according to an embodiment.

FIG. 2 is a perspective view of the digital copying machine according to the present embodiment.

FIG. 3 is a control block diagram illustrating an image forming operation according to the first embodiment.

FIG. 4 is a diagram showing a relationship between an image ratio and an image length.

FIG. 5 is a control block diagram illustrating an image forming operation according to a second embodiment.

FIG. 6 is a diagram illustrating a relationship between a load caused by a sheet feeding unit and an image length.

FIG. 7 is a control block diagram illustrating an image forming operation according to a third embodiment.

FIG. 8 is a diagram illustrating a relationship between transfer paper thickness and image length.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Image forming unit 2 Cassette feeding unit 3 Manual feeding unit 4 Paper discharge storage unit 5 Photoconductor 6 Charging device 7 Exposure device 8 Developing device 9 Transfer device 10 Cleaning device 11 Fixing device 12 Paper discharge device 30 Document reading unit 31 Reading Running body 32 Contact glass 33 Lens 34 CCD (photoelectric conversion element)

Claims (3)

[Claims] An image signal receiving means for receiving an image signal of a document; and a polygon motor driven at a predetermined number of rotations.
Image forming means for forming an image signal received by the image signal receiving means on a photosensitive member as an electrostatic latent image; and paper feed for feeding a sheet for forming an image of the image signal received by the image signal receiving means Means, and an image forming means for forming an electrostatic latent image on the photoreceptor formed by the image forming means on a sheet fed by the sheet feeding means, wherein the image forming means comprises: An image forming apparatus, wherein the number of rotations of the polygon motor is switched according to an image signal received by the image signal receiving unit and a size of a sheet fed by the sheet feeding unit. 2. An image signal receiving means for receiving an image signal of a document, and a polygon motor driven at a predetermined number of revolutions,
Image forming means for forming an image signal received by the image signal receiving means on a photosensitive member as an electrostatic latent image; and paper feed for feeding a sheet for forming an image of the image signal received by the image signal receiving means Means, when there are a plurality of the paper feeding means, selecting means for selecting which paper feeding means from among the plurality of paper feeding means to feed the paper, and a static image on the photosensitive member formed by the image forming means. Image forming means for forming an image of an electro-latent image on a sheet fed by the sheet feeding means, wherein the image forming means is provided by the polygon motor according to the sheet feeding means selected by the selecting means. An image forming apparatus, wherein the number of rotations is switched. 3. An image signal receiving means for receiving an image signal of a document, and a polygon motor driven at a predetermined number of revolutions,
Image forming means for forming an image signal received by the image signal receiving means on a photosensitive member as an electrostatic latent image; and paper feed for feeding a sheet for forming an image of the image signal received by the image signal receiving means Means for detecting the thickness of a sheet fed from the sheet feeding means, wherein the electrostatic latent image formed on the photoreceptor formed by the image forming means is fed by the sheet feeding means. Image forming means for forming an image on the formed paper, wherein the image forming means switches the rotation speed of the polygon motor according to the thickness of the paper detected by the detecting means. Forming equipment.