JPH0412951A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain a transcribed image having very little deviation of main scanning direction and little strain by driving a variable guide member of transport direction based on the detected signal of a skew angle detecting means, and providing a control means for running direction of recording paper. CONSTITUTION:Skew angle of recording paper 100 transcribed with a toner image by passing through a pressing part is detected by a skew angle detecting means. Based on the skew angle detected signal, a variable guide member 23 is controlled to be driven so as to correct difference between the skew angle of the recording paper 100 after transcription and the angle of running direction of the recording paper 100 due to the variable guide member 23 of transport direction. Consequently, difference between the running direction angle of an image holding body drum 11 for the recording paper 100 and a transcribing roller 12 to the pressing part and the transport direction angle of the recording paper 100 after transcription, can be sufficiently minified, regardless of parameters such as sorts of recording paper 100, environment, print pattern, and image concentration.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention is applicable to printers, facsimiles, ? J! The present invention relates to an image forming apparatus such as a copying machine, and more particularly to an image forming apparatus configured so that no distortion occurs in the transferred image when a toner image on an image carrier drum is transferred onto the surface of a recording paper using a pressure transfer roller.

C. Prior Art] An image receiving member, for example, a printer that forms an image on recording paper;
Various types of image forming devices such as facsimile machines and copying machines have been developed and put into practical use.For example, in printers, the impact of the dot matrix format, which outputs images such as two numbers and characters from digital image information. There are printers, electrostatic printers, laser printers, etc.

For example, in an electrostatic printer, an ion flow electrode is used to form an electrostatic latent image consisting of a large number of dot lines on an image carrier made of a dielectric drum, and this is developed with toner to form a toner image on a recording paper. Japanese Patent Application Laid-Open No. 57-501348 discloses a structure for transferring and fixing the image to the image forming apparatus.

Next, a conventional image forming apparatus having such a configuration is shown in FIG. In the figure, reference numeral 1 denotes a rotatable image bearing drum, on which an electrostatic latent image consisting of a large number of dots is formed by an ion flow recording head 2, and this latent image is transferred to a toner by a developing device 3. The developed toner image is transferred onto the recording paper 5 conveyed between the image bearing drum 1 and the pressure transfer roller 4 and fixed at the same time. Image carrier drum 1
The toner and latent image remaining on the surface are removed by a static elimination cleaning device 6.
The latent image is removed by the latent image and is configured to prepare for the formation of a new latent image.

In such an image forming apparatus using the pressure transfer and simultaneous fixing method, it is necessary to improve toner transfer efficiency, reduce impact and noise when the recording paper 5 enters between the image bearing drum 1 and the pressure transfer roller 4 and is ejected. In order to reduce the pressure and to equalize the pressure distribution, as shown in the diagrammatic plan view of FIG. B are pressed against each other so that they intersect at a certain angle θ.

With this configuration, the pressure contact line between the image carrier drum l and the pressure transfer roller 4 is aligned with the center axis A- of the image carrier drum 1.
Bisector C-C between A and the central axis B-B of the transfer roller 4
The recording paper 5 receives a force of being conveyed perpendicularly to the pressure tangent line CC, causing it to travel obliquely.

When such skew occurs, the image I formed on the recording paper 5 is shifted by θ/2 from the image I that would be formed without such skew. In other words, the image area formed on the recording paper 5 will not be rectangular (square).Such a problem occurs not only when using an ion flow type recording head, but also when using a dot matrix printer or a recording needle. This phenomenon also occurs in electrostatic printers, thermal printers using dot-shaped thermal elements, and the like.

Conventionally, in order to correct such image distortion, that is, to perform squareness correction, for example, Japanese Patent Application Laid-Open No.
Japanese Patent No. 116064 proposes that a copying machine move a lens laterally when scanning an original image, or move a scanning means also laterally. Further, in Japanese Patent Application Laid-open No. 198180/1983, the recording paper 5 is placed in advance in a direction that is deviated by a skew angle β with respect to the direction perpendicular to the rotation center axis of the pressure transfer roller 4, and then the image carrier drum 1 and the transfer roller A proposal has been made to eliminate misalignment of the transferred image in the main scanning direction by entering the contact portion with 4.

(Problems to be Solved by the Invention) However, when the squareness correction technique disclosed in Japanese Patent Application Laid-open No. 56-116064 is applied to the image forming apparatus shown in FIG. Image distortion is corrected by moving the recording head 2 in the same direction as the oblique direction, but mechanically moving the recording head 2 requires a complicated and expensive mechanism, and it is difficult to accurately perform this movement. There is a problem in that it is difficult to make sufficient corrections because it is difficult to do so.

Regarding the technique disclosed in Japanese Patent Application Laid-Open No. 61-198180, subsequent research revealed that the skew angle β of the image transferred onto the recording paper with respect to the recording paper is not always constant (rather, depending on the recording paper type and environment), It has been found that there is a large variation within the range of the intersection angle θ between the central axes of the image carrier drum and the transfer roller due to factors such as the print pattern and image density.

For example, the larger the print area or the higher the image density, the larger the skew becomes, and there is a clear tendency for the skew to be large when the humidity is low and the skew to be small when the humidity is high. Therefore, even if the recording paper enters the pressure contact area between the image bearing drum and the transfer roller in advance in an orientation shifted by the skew angle β with respect to the direction perpendicular to the central axis of the transfer roller, it will not pass through the pressure contact area. Since the skew angle β of the recording paper fluctuates, it is difficult to always obtain high squareness.

The present invention has been made to solve the above-mentioned problems in conventional image forming apparatuses. An object of the present invention is to provide an image forming apparatus that can perform correction and always obtain high squareness regardless of changes in parameters such as the type of image, environment, print pattern, and image density.

[Means and operations for solving the problems] In order to solve the above problems, the present invention provides an image bearing drum that holds a toner image obtained by developing a latent image, and an image bearing drum that records the toner image on the image bearing drum. a transfer roller for transferring onto paper, and the transfer roller is pressed against the image carrier drum by shifting the axis of the transfer roller to intersect with the axis of the image carrier drum. In the image forming apparatus, a conveying direction variable guide member configured to arbitrarily change the traveling direction of the recording paper conveyed to the pressure contact portion between the image bearing drum and the transfer roller; A means for detecting a skew angle of the recording paper onto which the toner image has been transferred is provided, and a means for driving the conveyance direction variable guide member based on a detection signal of the skew angle detection means to control the traveling direction of the recording paper. It consists of

In the image forming apparatus configured as described above, the skew angle detection means detects the skew angle of the recording paper that has passed through the pressure contact portion and has the toner image transferred thereto. Then, based on the skew angle detection signal, the guide member control means causes the variable guide member to correct the difference between the skew angle of the recording paper after transfer and the running direction angle of the recording paper by the variable conveyance direction guide member. is driven and controlled. Therefore, the difference between the running direction angle of the recording paper toward the pressure contact portion of the image carrier drum and the transfer roller and the transport direction angle of the recording paper after transfer is calculated as follows:
Recording paper type, environment, print pattern.

This can be made sufficiently small without being influenced by differences in parameters such as image density, and thereby the deviation in the main scanning direction between the transferred image and the recording paper can be made sufficiently small.

〔Example〕

Next, an example will be described. FIG. 1 is a partially omitted perspective view showing an embodiment of an image forming apparatus according to the present invention.
Figure 2 is a side view seen from the downstream side, and Figure 3
, 2) are an enlarged perspective view and a top view of an image bearing drum and a transfer roller portion.

In the figure, reference numeral II denotes an image bearing drum, and a transfer roller 12 is provided in pressure contact with the drum 11, as shown in FIG.
As shown at 81, the central axis f3-B of the transfer roller 12 intersects with the central axis A-A of the drum 11 at an intersection angle θ. A scanning head section 13 is arranged above this drum 11. This scanning head section 1
3, when the rotating drum 11 is composed of a dielectric drum that directly scans and projects an electric charge image, it is disclosed in, for example, Japanese Patent Laid-Open No. 57-501348. An ion emitting head or a multi-needle electrode head is used, and the drum 11 forms a charge image by scanning and projecting a light image after uniformly charging an electrophotographic photoreceptor with a corona charger, like a photoreceptor drum. In the case of a light-emitting diode array head, a liquid crystal matrix head, a laser beam scanning head, a cathode ray tube scanning head, or a document image scanning optical system head, which is the optical system of a normal electrophotographic copying machine, are used.

The drum 11 is driven in the direction of arrow a about the axis A-A, and the transfer roller 12
is rotated in the direction of the arrow as the drum 11 rotates. The drum 11 and transfer roller 1
As shown in FIG. 3 (Bl), the pressure contact portion with 2 has a pressure contact angle α that is 1/2 of the intersection angle θ with respect to the axis A-A.

Further, on the upstream side of the pressure transfer section formed by the drum 11 and the transfer roller 12, there is a pair of feeding rollers 21 for conveying the recording paper 100 in the direction of arrow X perpendicular to the central axis AIA-A of the drum 11. .22 is placed.

The feeding rollers 21 and 22 are supported so as to be rotationally driven in the directions of arrows c and d, respectively.

Further, a flat sheet guide plate 25 is arranged between the pair of drum 11 and transfer roller 12 and the pair of feeding rollers 21 and 22, and one end of the transfer roller 12 of this guide plate 25 is located slightly below the pressure contact surface between the drum 11 and the transfer roller 12, and the other end on the feed roller 21° 22 side has a tip guide surface 25 bent downward.
a is provided, and this tip guide surface 25a is arranged so as to be located slightly below the contact surfaces of both the rollers 21 and 22. Further, a notch 25b is formed on one side of the sheet guide plate 25 and is inclined in the direction of both rollers 2L 22, and a recording sheet is provided on the side of the notch 25b. A variable conveyance direction guide section 23 is disposed for causing the drum 100 to travel at an arbitrary angle, that is, at a skew angle β, with respect to the center line r perpendicular to the central axis line AA of the drum 11. As shown in FIG. 4, the base 23a of the variable guide portion 23 has
A support shaft 24 connected to a running direction guide control motor 56 is provided, and a guide surface 23b is formed in the intermediate portion of the variable guide portion 23. This guide surface 23b is formed perpendicularly to the plate surface of the sheet guide plate 25, and a tip guide surface 23c that slopes outward is formed at the tip of this guide surface 23b.

Also, disposed above the sheet guide plate 25 are sheet deflecting and feeding rollers 26 and 27 that rotate in contact with the plate surface of the guide plate 25. This deflection feed roller 26
．． The feed roller 2L 27 rotates to move the recording paper 100 at a speed faster than the feeding speed of the recording paper 100 being conveyed on the sheet guide plate 25 by the feeding roller 2L 22, and moves the side edge of the recording paper 100 above. The recording paper 100 is moved toward the drum 11 by pressing against the guide surface 23b, and after the recording paper 100 hits the pressure contact portion of the drum 11 and the transfer roller 12, it rotates idly.

A sheet discharge guide Fi28 is disposed downstream of the pressure contact portion between the drum II and the transfer roller 12.

A downwardly bent tip guide surface 28a is formed at the end of the guide plate 28 on the drum 11 side. A notch 28b is provided on one side of the guide plate 28 in a direction perpendicular to the conveying direction of the recording paper, and as shown in FIG. A sensor 50 is installed to detect the position of the side edge of the recording paper 100 conveyed on the guide plate 28.

For example, a CCD line sensor is used as the sensor 50, and the recording paper 10 is conveyed on the guide plate 28.
The side edge position of the recording paper 100 is detected at a predetermined run H1 of the operation timing pulse generated by the output of the rotary encoder provided on the drum 11, and then the same recording paper 100 is detected again after counting a predetermined number of pulses. Detects the position of the side edge of the recording paper, and based on the side edge position information of the recording paper,
The skew angle of the recording paper 100 is detected.

In this way, the drum 11 and the transfer roller 12 are brought into pressure contact 5.
The recording paper 100 that has been fed out from CC and whose side edge position has been detected moves on a sheet ejection guide plate 28 and is ejected. It goes without saying that the image forming apparatus according to the present invention is also provided with a developing device and a static eliminating cleaning device similar to those shown in the conventional example of FIG. 6, although they are not shown.

FIG. 5 is a block diagram showing the overall configuration of an image information processing section and a control section of an image forming apparatus according to the present invention. A code signal from an image data generating device 51 such as a computer is supplied to a character generator 52 to generate a video signal corresponding to a desired character. In accordance with this video signal, the deskew circuit 53 selects an electrode to generate ions, and the corresponding line electrode is designated by a 5-bit parallel signal at a timing corresponding to the video signal.

Based on this 5-bit parallel signal, one circuit of the selected ion recording head driver 54 applies a burst to the line electrode of the throat section 13 to scan the ions, thereby generating ions. Further, the feeding unit 55 manages the timing of the entire image forming apparatus, and calculates the skew angle of the recording paper based on the recording paper side edge position information from the recording paper position sensor 5°. The angle of the conveyance direction variable guide section 23 is determined, a signal is output to the traveling direction guide control motor 56, and the angle of the conveyance direction variable guide section 23 is determined.
is driven to a predetermined angle.

Next, the operation of the image forming apparatus of this embodiment configured as described above will be explained. When the recording paper 100 is fed by the feeding rollers 21 and 22 in the direction of arrow X perpendicular to the central axis A-A of the drum 11, the recording paper 100 is conveyed on the sheet guide plate 25. and deflection feed roller 2
6.27, the recording paper 100 is moved to the deflection feed roller 2.
By the action of 6.27, the side edge of the recording paper 100 is brought into contact with the guide surface 23b of the variable conveyance direction guide section 23, and is sent toward the pressure contact section between the drum 11 and the transfer roller 12. That is, as shown in Figure 3), the drum 11
It is sent in a direction S' shifted by a skew angle β with respect to a direction S perpendicular to the central axis AA of .

Travel skew angle β due to the conveyance direction variable guide section 23
The first sheet of recording paper is determined by the control unit based on the print pattern and image density information of the first sheet of the image to be recorded sent from the host computer, as well as recording paper quality information, environmental information, etc. be done. The second and subsequent sheets are determined by detecting the position of the side edge of the recording sheet that passed through the transfer section immediately before using the recording sheet position sensor 50.

At this time, image distortion can be corrected even more reliably if the configuration is configured such that image information such as image density and print pattern for each page is determined in addition to the information detected by the recording paper position sensor 50. be able to.

In synchronization with the transport movement of the recording paper 100 as described above, an electrostatic latent image is formed on the drum 11 by the scanning head section 13. This latent image is developed into a toner image P by a developing device (not shown). This toner image P is pressure-transferred onto the recording paper 100 at a pressure contact portion between the drum 11 and the transfer roller 12. At this time, the recording paper 100 is discharged in a direction S' substantially perpendicular to the pressure tangent line CC. Recording paper 1 at this time
As mentioned above, the skew amount of 00 is determined by the recording paper position sensor 5.
0 is detected and fed back to the control of the conveyance direction variable guide section 23 during subsequent recording paper feeding.

The image Q transferred to the recording paper 100 in this way has no distortion in the length direction perpendicular to the horizontal direction of the recording paper 100, and no distortion in the width direction, as shown in FIG. arise. However, this newly generated distortion does not accumulate as the recording paper 100 is conveyed (and since the skew angle β is a small corner), there is no problem of spoiling the aesthetic appearance.

〔Effect of the invention〕

As described above based on the embodiments, according to the present invention, based on the skew angle detection signal (by controlling the traveling direction of the conveyance direction variable guide member by the control means), the image bearing drum and the transfer roller of the recording paper are The difference between the direction of travel to the pressure contact part and the direction of conveyance of the recording paper after transfer is determined depending on the type of recording paper and environment 1.
image pattern.

Since it can be made sufficiently small without being affected by changes in parameters such as image density, a transferred image with a sufficiently small deviation in the main scanning direction and little distortion can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of an image forming apparatus according to the present invention, FIG. 2 is a side view of the image forming apparatus as seen from the downstream side, and FIG. FIG. 4 is a diagram showing the variable conveyance direction guide section and its control section; FIG. 5 is a block diagram showing the overall configuration of the image information processing section and the control section; 6
7 is a diagram showing an example of the configuration of a conventional image forming apparatus, and FIG. 7 is a diagram showing an example of image formation on recording paper by the image forming apparatus shown in FIG. 6. In the figure, 11 is an image carrier drum, 12 is a transfer roller, 13 is a scanning head section, 21.22 is a feeding roller, 23
24 is a conveyance direction variable guide portion, 24 is a spindle, 25 is a sheet guide plate, 26.27 is a sheet deflection feed roller, 28 is a sheet discharge guide plate, 28b is a notch portion, 50 is a recording paper position sensor, and 51 is an image A data generating device, 52 a character generator, 53 a deskew circuit, 54 a recording head driver, 55 a control unit, 56 a running direction guide control motor, and 100 a recording sheet. Patent applicant: Olympus Optical Industry Co., Ltd. Figure 3 (A)

Claims (1)

[Claims] 1. It has an image carrier drum that holds a toner image with a developed latent image, and a transfer roller that transfers the toner image on the image carrier drum onto recording paper, and the transfer roller is connected to the image carrier. In an image forming apparatus in which the transfer roller is pressed against the drum so that its axial center intersects with the axial center of the image carrier drum, the image carrier drum is transported to a pressure contact portion between the image carrier drum and the transfer roller. a conveyance direction variable guide member configured to arbitrarily change the running direction of the recording paper; means for detecting a skew angle of the recording paper to which the toner image has been transferred after passing through the pressure contact portion; and the skew angle detection means. an image forming apparatus comprising: means for driving the conveyance direction variable guide member based on a detection signal of the recording paper to control the traveling direction of the recording paper.